首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9100篇
  免费   727篇
  国内免费   22篇
耳鼻咽喉   95篇
儿科学   338篇
妇产科学   188篇
基础医学   1330篇
口腔科学   418篇
临床医学   885篇
内科学   1828篇
皮肤病学   193篇
神经病学   836篇
特种医学   295篇
外科学   1461篇
综合类   115篇
一般理论   6篇
预防医学   657篇
眼科学   115篇
药学   563篇
中国医学   23篇
肿瘤学   503篇
  2023年   123篇
  2022年   184篇
  2021年   389篇
  2020年   224篇
  2019年   282篇
  2018年   337篇
  2017年   219篇
  2016年   235篇
  2015年   240篇
  2014年   332篇
  2013年   379篇
  2012年   591篇
  2011年   560篇
  2010年   300篇
  2009年   259篇
  2008年   398篇
  2007年   386篇
  2006年   356篇
  2005年   364篇
  2004年   299篇
  2003年   301篇
  2002年   275篇
  2001年   237篇
  2000年   220篇
  1999年   185篇
  1998年   89篇
  1997年   65篇
  1996年   63篇
  1995年   52篇
  1994年   52篇
  1993年   52篇
  1992年   125篇
  1991年   125篇
  1990年   115篇
  1989年   124篇
  1988年   101篇
  1987年   107篇
  1986年   93篇
  1985年   91篇
  1984年   61篇
  1983年   53篇
  1980年   42篇
  1979年   62篇
  1978年   42篇
  1974年   54篇
  1973年   39篇
  1972年   54篇
  1971年   58篇
  1970年   44篇
  1969年   36篇
排序方式: 共有9849条查询结果,搜索用时 15 毫秒
91.

Context

The previous European Association of Urology (EAU) guidelines on urinary incontinence comprised a summary of sections of the 2009 International Consultation on Incontinence. A decision was made in 2010 to rewrite these guidelines based on an independent systematic review carried out by the EAU guidelines panel, using a sustainable methodology.

Objective

We present a short version of the full guidelines on assessment, diagnosis, and nonsurgical treatment of urinary incontinence, with the aim of increasing their dissemination.

Evidence acquisition

Evidence appraisal included a pragmatic review of existing systematic reviews and independent new literature searches, based on Population, Intervention, Comparator, Outcome questions. Appraisal of papers was carried out by an international panel of experts, who also collaborated on a series of consensus discussions, to develop concise structured evidence summaries and action-based recommendations using a modified Oxford system.

Evidence summary

The full version of the guidelines is available online (http://www.uroweb.org/guidelines/online-guidelines/). The guidelines include algorithms that refer the reader back to the supporting evidence, and they are more immediately useable in daily clinical practice.

Conclusions

These new guidelines present an up-to-date summary of the available evidence, together with clear clinical algorithms and action-based recommendations based on the best available evidence. Where such evidence does not exist, they present a consensus of expert opinion.  相似文献   
92.

PURPOSE

We aimed to evaluate the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) for detecting post-treatment cervical cancer recurrence. The detection accuracy of T2-weighted (T2W) images was compared with that of T2W MRI combined with either dynamic contrast-enhanced (DCE) MRI or DWI.

METHODS

Thirty-eight women with clinically suspected uterine cervical cancer recurrence more than six months after treatment completion were examined with 1.5 Tesla MRI including T2W, DCE, and DWI sequences. Disease was confirmed histologically and correlated with MRI findings. The diagnostic performance of T2W imaging and its combination with either DCE or DWI were analyzed. Sensitivity, positive predictive value, and accuracy were calculated.

RESULTS

Thirty-six women had histologically proven recurrence. The accuracy for recurrence detection was 80% with T2W/DCE MRI and 92.1% with T2W/DWI. The addition of DCE sequences did not significantly improve the diagnostic ability of T2W imaging, and this sequence combination misclassified two patients as falsely positive and seven as falsely negative. The T2W/DWI combination revealed a positive predictive value of 100% and only three false negatives.

CONCLUSION

The addition of DWI to T2W sequences considerably improved the diagnostic ability of MRI. Our results support the inclusion of DWI in the initial MRI protocol for the detection of cervical cancer recurrence, leaving DCE sequences as an option for uncertain cases.Cervical cancer is the fourth most frequent cancer in women worldwide (1). Early stage disease is treated with surgery or chemoradiotherapy and has a good prognosis. However, around 30% of all patients treated for cervical carcinoma develop progressive or recurrent tumors (2).Recurrent cervical cancer is defined as local tumor regrowth or the development of distant organ/lymph node metastases at least six months after regression of the initial lesion. Approximately two-thirds of recurrences appear within the first two years following initial treatment, with 90% recurring by five years post-treatment (3). Risk factors for recurrence include histopathologic features, depth of tumor invasion, and nodal status (4).Pelvic recurrence can be located centrally (cervix, uterus, vagina, parametria, ovaries, bladder, or rectum) or in the pelvic sidewalls. Extrapelvic recurrence most commonly involves the para-aortic lymph nodes, lungs, liver, or bone (46).Treatment of recurrent cancer depends on the primary treatment approach, location, and extension. Patients with locally recurrent disease can be offered salvage treatments with curative potential (chemoradiotherapy, if not given previously, or pelvic exenteration in patients who already received chemoradiotherapy). Distant metastases, however, are nearly always incurable (3).In patients who successfully completed primary treatment, surveillance has been advocated to detect the residual or recurrent disease at curable stages (7). The use of imaging studies such as magnetic resonance imaging (MRI) is indicated on the basis of clinical suspicion (8).T2-weighted (T2W) imaging is the reference sequence for cervical cancer staging (9). Recurrent tumors are known to show high signal intensity on T2W MRI, contrasting with the low signal intensity of the cervical stroma. However, some benign conditions such as necrosis, inflammation, and edema may also increase signal intensity on T2W images, representing a potential challenge to the radiologist, particularly after radiotherapy (1013).Moreover, post-treatment changes can result in areas of fibrosis that are also difficult to differentiate from recurrence (14). MRI has proven to be superior to computed tomography (CT) in distinguishing fibrosis and scarring from active disease, but imaging findings are sometimes indeterminate, complicating the evaluation of recurrent disease (3).In recent years, the functional MRI techniques such as dynamic multiphase contrast-enhanced (DCE) MRI and diffusion-weighted imaging (DWI) have emerged as fundamental tools in female pelvic imaging evaluation (15). Although DCE was shown to be more accurate than T2W alone for tumor recurrence identification, the use of both sequences is recommended (10).Recently, DWI has been added to pelvic MRI protocols to increase diagnostic accuracy in tumor staging. This technique is a functional tool that relies on tissue water displacement to create a contrasted image. For correct evaluation and avoidance of pitfalls, the generated images must be interpreted alongside anatomical sequences. The apparent diffusion coefficient (ADC) map is also needed to reduce image misinterpretation, for example due to the T2 shine-through effect (15). In highly cellular tissues, water movement is restricted and such lesions appear bright at high b-values (1000 s/mm2) and have low ADC value, appearing dark gray on ADC maps in contrast to areas of freely moving water such as urine in the bladder (14). Some recent studies have suggested that DWI and ADC maps can be potentially useful in oncologic follow-up (14, 16).The purpose of this study was to compare the accuracy of T2W/DWI with that of conventional anatomical sequences alone and T2W/DCE imaging sequences in the evaluation of recurrent disease in patients treated for uterine cervical carcinoma.  相似文献   
93.

Objectives

This study evaluated the performance of a novel automated software tool for epicardial fat volume (EFV) quantification compared to a standard manual technique at coronary CT angiography (cCTA).

Methods

cCTA data sets of 70 patients (58.6?±?12.9 years, 33 men) were retrospectively analysed using two different post-processing software applications. Observer 1 performed a manual single-plane pericardial border definition and EFVM segmentation (manual approach). Two observers used a software program with fully automated 3D pericardial border definition and EFVA calculation (automated approach). EFV and time required for measuring EFV (including software processing time and manual optimization time) for each method were recorded. Intraobserver and interobserver reliability was assessed on the prototype software measurements. T test, Spearman’s rho, and Bland–Altman plots were used for statistical analysis.

Results

The final EFVA (with manual border optimization) was strongly correlated with the manual axial segmentation measurement (60.9?±?33.2 mL vs. 65.8?±?37.0 mL, rho?=?0.970, P?<?0.001). A mean of 3.9?±?1.9 manual border edits were performed to optimize the automated process. The software prototype required significantly less time to perform the measurements (135.6?±?24.6 s vs. 314.3?±?76.3 s, P?<?0.001) and showed high reliability (ICC?>?0.9).

Conclusions

Automated EFVA quantification is an accurate and time-saving method for quantification of EFV compared to established manual axial segmentation methods.

Key Points

? Manual epicardial fat volume quantification correlates with risk factors but is time-consuming. ? The novel software prototype automates measurement of epicardial fat volume with good accuracy. ? This novel approach is less time-consuming and could be incorporated into clinical workflow.  相似文献   
94.
BACKGROUND: Tertiary hyperparathyroidism typically occurs in patients who have recovered from renal failure after renal transplantation. This report describes a syndrome of tertiary hyperparathyroidism after recovery from multiple organ failure (MOF) with acute oliguric renal failure (AORF). METHODS: Six patients with MOF including AORF are presented. Increased parathyroid hormone (PTH) levels were documented as early as 3 weeks after injury or septic insult and remained increased in some patients for several weeks. RESULTS: The resultant increase in calcium levels led to recurrent bouts of bradycardia, often leading to asystole requiring cardiopulmonary resuscitation. Hypercalcemic-induced bradycardia was refractory to hydration, loop diuresis, atropine, and external pacing. Definitive treatment requires bisphosphonate therapy, which must be repeated until organ function has returned to normal. CONCLUSIONS: A new syndrome of life-threatening tertiary hyperparathyroidism is described in patients with critical illness. This syndrome probably is being overlooked frequently in critical care units. Early diagnosis and prophylactic treatment with bisphosphonate may preclude the life-threatening cardiac arrhythmias.  相似文献   
95.
BACKGROUND CONTEXT: Spinal epidural hematoma can result from traumatic and atraumatic etiologies. Atraumatic spinal epidural hematomas have been reported as an initial presentation of multiple myeloma. There are no other reports previously describing spinal epidural hematoma after a pathologic spinal fracture. PURPOSE: To present the first reported case of a spinal epidural hematoma after a pathologic fracture and a very unusual initial presentation of multiple myeloma in a young patient. STUDY DESIGN/SETTING: Case report. METHODS: A healthy asymptomatic 37-year-old male was struck in the head with a ball while playing soccer. Initial symptoms included severe back pain without neurologic symptoms. Complete motor paralysis developed over the next 24 hours in the lower extremities with a sensory level of T10. Magnetic resonance imaging evaluation of the spine revealed a T6 compression fracture with a dorsal T3 to T10 epidural hematoma. The patient underwent surgical T2 to T8 posterior spinal decompression with evacuation of the hematoma. Serum and urine electrophoresis and bone marrow biopsy were performed. RESULTS: The results of the electrophoresis revealed an immunoglobulin A monoclonal spike. The bone marrow biopsy was positive for plasma cell myeloma. Recovery of some motor function was noted in both lower extremities postoperatively. The patient was subsequently started on steroids and chemotherapy for myeloma. The patient has also undergone bone marrow transplant, and his myeloma is currently in remission. CONCLUSION: This is the first reported case of spinal epidural hematoma after a pathologic spinal fracture. Also, this case represents an unusual initial presentation of multiple myeloma in a young patient.  相似文献   
96.
Purpose : To carry out a comparative study on potential cytogenetic fingerprints for radiation LET in human metaphase lymphocytes. Materials and methods : Human lymphocytes were irradiated in vitro with 3.0Gy 60 Co γ-rays, 0.9 Gy 3 H β -rays or 0.2 Gy 2.7Mev neutrons. Detailed chromosome aberrations were analysed by combined FISH with pan-telomere staining and specific wholechromosome painting (1, 2 and 4). Total chromosome translocations and insertions were also analysed by multicolour wholechromosome painting (chromosomes 1, 2 and 4 orange, chromosomes 3, 5 and 6 green). Results : Among the six proposed radiation cytogenetic fingerprints, the ratio of total simple translocations to insertions (I-ratio), showed the largest difference between low-LET 60Co γ-ray and high-LET neutron radiation. The ratios of complete exchanges to incomplete rejoinings [S(I)-ratio] and dicentrics to interstitial deletions (H-ratio), showed a similar significant difference between low- and high-LET radiation. The ratios of centric rings to interstitial deletion (G-ratio) showed a trend of LETrelated difference, but the difference was not significant in this data set. The ratios of dicentrics to centric rings (F-ratio) and apparent complete exchanges to hidden complete exchanges [S(II)-ratio], showed no difference between low- and high-LET radiation. In the 1426 radiation-induced chromosome aberrations observed after 52h culture, evidence for sister-chromatid fusion but not telomere addition was found. Conclusion : Pan-telomere staining plus specific whole chromosome painting allows simultaneous and objective detection of complete or incomplete chromosome exchanges and interstitial or terminal deletions in human peripheral lymphocytes. Of the six proposed cytogenetic ratios, the I-ratio is the most effective cytogenetic fingerprint for distinguishing low-LET from high-LET radiation in human metaphase human lymphocytes.  相似文献   
97.
A 4-year-old girl suffered intraventricular and subarachnoid hemorrhage during endoscopic third ventriculostomy. Cerebral angiography revealed a traumatic basilar aneurysm secondary to basilar artery injury. The aneurysm was treated with selective endovascular embolization using Guglielmi detachable coils. We review some therapeutic features of traumatic basilar aneurysms after endoscopic third ventriculostomy and describe the feasibility of endovascular selective therapy to manage these lesions successfully.  相似文献   
98.
BACKGROUND: The octogenarian patient is often perceived as too fragile to undergo cardiothoracic surgery. Our study aimed to compare postoperative complications in patients aged less than 80 versus elderly patients (80 years or more) after surgical cardiac intervention (coronary artery bypass or valve replacement). METHODS: Subjects were all patients (n = 8,361) who had an open-heart procedure, either coronary artery bypass or valve implantation or replacement, at two medical centers located in northern Virginia using the same surgical group. A computerized medical record database was reviewed to determine preoperative risk factors and postoperative outcomes. Predictors of complications were identified by univariate and multivariate logistic regression. RESULTS: A total of 3,214 complications were recorded. The most prevalent complications were prolonged ventilation time in the intensive care unit, reoperation for bleeding, and pneumonia. The overall mortality rate was 2.4% (204 of 8,361). Persons aged over 80 years had nearly double the mortality rate compared with younger patients (4.1% [18 of 444] to 2.3% [186 of 7,917]). Age greater than 80 years (odds ratio = 2.65, 95% confidence interval = 2.18 to 3.22) and male gender (odds ratio = 0.62, 95% confidence interval = 0.56 to 0.69) were the best univariate predictors of a single postoperative complication. CONCLUSIONS: Octogenarian patients manifested twice the risk of death from a cardiac intervention with an average 2-day longer hospital stay compared with their younger counterparts. Furthermore, octogenarians were at markedly higher risk of nonfatal postoperative complications.  相似文献   
99.
Robotic systems may be particularly supportive for procedures requiring careful pelvic dissection and suturing in the Douglas pouch, as in surgery for rectal prolapse. Studies reporting robot-assisted laparoscopic rectovaginopexy for rectal prolapse, however, are scarce. This prospective cohort study evaluated the outcome of this technique up to one year after surgery. From January 2005 to June 2006, 15 consecutive patients with a rectal prolapse, either with or without a concomitant rectocele or enterocele, underwent robot-assisted laparoscopic rectovaginopexy with support of the da Vinci robotic system. A prospective cohort study was performed on operating times, blood loss, intra-operative and post-operative complications, and outcome at a minimum of one year after surgery. Median age at time of operation was 62 years (33–72) and median body mass index 24.9 (20.9–33.9). Median robot set-up time was 10 min (3–15) and median skin-to-skin operating time was 160 min (120–180). No conversions to open surgery were necessary. No in-hospital complications occurred and there was no mortality. Median hospital stay was four days (2–9). During one year follow-up, two patients needed surgical reintervention. One patient was operated for recurrent enterocele and rectocele one week after surgery. In another patient an incisional hernia at the camera port occurred three months after surgery. At one year after surgery, 87% of patients claimed to be satisfied with their postoperative result. Robot-assisted laparoscopic rectovaginopexy proved to be an effective technique with favourable outcomes in most patients in this prospective series. The operating team experienced the support of the robotic system as beneficial, especially during the dissection of the rectovaginal plane and suturing in the Douglas pouch.  相似文献   
100.
OBJECTIVE: To investigate the effects of inosine on the acute lung inflammation induced by lipopolysaccharide (LPS) in vivo and on the activation and cytotoxicity elicited by proinflammatory cytokines on human lung epithelial (A549) cells in vitro. SUMMARY BACKGROUND DATA: Inosine is an endogenous purine recently shown to exert immunomodulatory and antiinflammatory effects. METHODS: Mice challenged with intratracheal LPS (50 microg) were treated after 1, 6, and 12 hours with inosine (200 mg/kg intraperitoneal) or vehicle. After 24 hours, bronchoalveolar lavage fluid was obtained to measure proinflammatory (tumor necrosis factor-alpha [TNF-alpha], interleukin [IL]-1beta, IL-6), and antiinflammatory (IL-10, IL-4) cytokines, chemokines (MIP-1alpha and MIP-2), myeloperoxidase activity and total cell counts, nitric oxide production, and proteins. Lung histology and immunohistochemical detection of 3-nitrotyrosine, a marker of nitrosative stress, were performed in inflated-fixed lungs. In vitro, cell viability and production of the chemokine IL-8 were evaluated in A549 cells stimulated with a mixture of cytokines in the presence or absence of inosine. RESULTS: Inosine downregulated the LPS-induced expression of TNF-alpha, IL-1beta, IL-6 and MIP-2 and tended to reduce MIP-1alpha, whereas it enhanced the production of IL-4. Total leukocyte counts, myeloperoxidase, nitric oxide production, and proteins were all significantly decreased by inosine. The purine also improved lung morphology and suppressed 3-nitrotyrosine staining in the lungs after LPS. Inosine attenuated the cytotoxicity and the expression of IL-8 induced by proinflammatory cytokines in A549 cells. CONCLUSIONS: Inosine largely suppressed LPS-induced lung inflammation in vivo and reduced the toxicity of cytokines in lung cells in vitro. These data support the proposal that inosine might represent a useful adjunct in the therapy of acute respiratory distress syndrome.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号