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   6761篇
  免费   542篇
  国内免费   19篇
耳鼻咽喉   68篇
儿科学   188篇
妇产科学   154篇
基础医学   888篇
口腔科学   66篇
临床医学   821篇
内科学   1247篇
皮肤病学   143篇
神经病学   860篇
特种医学   113篇
外科学   781篇
综合类   65篇
一般理论   9篇
预防医学   744篇
眼科学   145篇
药学   519篇
中国医学   6篇
肿瘤学   505篇
  2024年   15篇
  2023年   141篇
  2022年   175篇
  2021年   399篇
  2020年   204篇
  2019年   322篇
  2018年   324篇
  2017年   222篇
  2016年   284篇
  2015年   288篇
  2014年   350篇
  2013年   407篇
  2012年   635篇
  2011年   602篇
  2010年   290篇
  2009年   268篇
  2008年   405篇
  2007年   393篇
  2006年   381篇
  2005年   315篇
  2004年   282篇
  2003年   215篇
  2002年   189篇
  2001年   19篇
  2000年   22篇
  1999年   12篇
  1998年   19篇
  1997年   21篇
  1996年   11篇
  1995年   12篇
  1994年   8篇
  1993年   8篇
  1992年   9篇
  1991年   9篇
  1990年   7篇
  1989年   2篇
  1987年   2篇
  1986年   3篇
  1985年   3篇
  1984年   5篇
  1983年   4篇
  1982年   6篇
  1981年   5篇
  1980年   6篇
  1975年   3篇
  1974年   5篇
  1972年   2篇
  1964年   2篇
  1963年   2篇
  1925年   1篇
排序方式: 共有7322条查询结果,搜索用时 15 毫秒
51.
Hydrothorax as a complication of peritoneal dialysis (PD) is a rare but recognized event. Proposed mechanisms for the development of a pleuro-peritoneal communication include congenital diaphragmatic defects, acquired weakening of diaphragmatic fibers caused by high intra-abdominal pressures during peritoneal dialysis, and impairments in lymphatic drainage. Pleural fluid analysis and diagnostic imaging assist in differentiation from other causes of pleural effusion. Nearly 50% of patients with this diagnosis have resolution of hydrothorax after temporary cessation of PD with interim hemodialysis for 2-6 weeks. Historically, other treatment options have included conventional pleurodesis and open thoracotomy with direct repair, producing variable results. With the advent of video-assisted thoracoscopy (VATS), surgical repairs and pleurodesis are now frequently performed under direct visualization with minimal invasiveness. We report a case of hydrothorax in a patient after recent introduction to peritoneal dialysis. Pleuro-peritoneal communication was documented with thoracentesis and radionuclide scanning. VATS pleurodesis with talc was performed. Repeat scintigraphy performed 1 week after the procedure revealed no residual communication, and patient was able to resume PD without further complications.  相似文献   
52.
53.
STUDY OBJECTIVE: To determine if recommendations regarding perioperative beta-blocker therapy were followed by an increase in the number of eligible presurgical patients receiving beta-blockers and the number achieving the recommended heart rate (HR <60 beats per minute [bpm]). DESIGN: Retrospective, observational study. SETTING: Tertiary-care teaching hospital. MEASUREMENTS: The records of all 718 patients who underwent elective vascular surgery or coronary artery bypass grafting between January 2001 and March 2002 (pre-guideline) and those who did so between April 2002 and September 2003 (post-guideline) were reviewed. Percentage of eligible patients who received beta-blockers preoperatively and the target HR achieved in pre-guideline versus post-guideline patients were recorded. Differences were assessed using the unpaired t test and chi2 analysis. A P value of less than 0.05 is reported. MAIN RESULTS: Fifty percent of the post-guideline patients in the vascular surgery group were receiving beta-blockers at the time of preanesthetic evaluation versus 48% of pre-guideline patients (P = nonsignificant [NS]). Mean HR in the vascular surgery post-guideline beta-blocker group (70 +/- 14 bpm) was higher than in the pre-guideline beta-blocker group (65 +/- 11 bpm) (P < 0.01). Only 22% of those vascular surgery patients in the post-guideline group who were taking beta-blockers achieved the target HR of less than 60 bpm versus 29% of the vascular surgery patients taking beta-blockers in the pre-guideline group (P = NS). In the coronary artery bypass grafting group, 80% of post-guideline patients received beta-blocker before anesthesia assessment versus 75% of pre-guideline patients (P = NS). Mean HR in the post-guideline beta-blocker group (67 +/- 15 bpm) was similar to the pre-guideline beta-blocker group (64 +/- 13 bpm) (P = NS). Only 28% of the post-guideline patients who were receiving beta-blockers achieved the target HR of less than 60 bpm, which was not significantly different from the 17% achieved in the pre-guideline group (P = NS). CONCLUSION: At our institution, preoperative beta-blocker use was not significantly changed by publication of the recommendations.  相似文献   
54.
A random urine calcium/creatinine ratio (UCa/Cr) is of practical use in screening for hypercalciuria. However, due to worldwide variations, reference values for the pediatric population are not yet well established. Furthermore, no study has been conducted to establish normal UCa/Cr values in young African-American (AA) children. It has also been previously reported that an elevated UCa/Cr is related to a high urine Na/K ratio (UNa/K). The objectives of the present study were: (1) to set normal values of random UCa/Cr by age and race in the pediatric population of Metropolitan Kansas City, (2) to identify potential racial differences in UCa/Cr between Caucasian (CS) and AA children, and (3) to determine the relationship between UCa/Cr and UNa/K in healthy children.A total of 368 healthy children of both genders were enrolled in the study. They were divided into four age groups as follows: (1) <7 months, (2) 8–18 months, (3) 19 months to 6 years, and (4) 7–16 years. Each group was subdivided into AA and CS. A non-fasting random urine specimen from each subject was analyzed for Ca, Na, K and creatinine.The median UCa/Cr values for AA were: (1) 0.13, (2) 0.09, (3) 0.06, and (4) 0.04 and for CS they were (1) 0.26, (2) 0.11, (3) 0.10, and (4) 0.09. The data showed a strong inverse relationship between UCa/Cr and age, the youngest children demonstrating the highest UCa/Cr. In each age group, UCa/Cr in CS exceeded the corresponding value in AA. The age-dependent 95th percentiles of UCa/Cr values for CS were (1) 0.70, (2) 0.50, (3) 0.28, and (4) 0.20 and for AA they were (1) 0.38 and (3) 0.24. Due to outliers, the 95th percentile could not be established for the other two AA subgroups. The relationship between UCa/Cr and UNa/K was found to be extremely weak in both AA (r 2 =0.00005) and CS (r 2 =0.02). On the other hand, a strong linear correlation was observed between UNa/K and age (CS r 2 =0.23, P<0.001, AA r 2 =0.19, P<0.001), explaining in part the lack of correlation between UNa/K and UCa/Cr.We conclude that the child’s age, ethnicity and geographic location should be taken into consideration when assessing UCa/Cr ratio. Contrary to what has previously been reported in hypercalciuric children, no significant relationship was found between UCa/Cr and UNa/K in healthy children. Received: 7 June 2000 / Revised: 21 September 2000 / Accepted: 23 September 2000  相似文献   
55.

Background

Extrapolation of rat testicular descent studies to humans has been criticized because of anatomical differences of the cremaster muscle. Human cremaster is described as a thin strip rather than a large, complete sac as in rats, which is proposed to be more important in propelling the testis during descent. This study investigated cremaster muscle anatomy and ontogeny in both normal and cryptorchid rat models.

Methods

Gubernacula from 4 groups of neonatal rats were sectioned longitudinally and transversely: normal Sprague-Dawley, capsaicin pretreated, flutamide pretreated, and congenital cryptorchid rats. Gubernacula were stained with hematoxylin-eosin, Masson trichrome, and desmin immunohistochemistry to study muscle development.

Results

Myoblasts are more numerous at the gubernacular tip, whereas the most differentiated muscle is proximal. Rat cremaster develops as an elongated strip rather than a complete sac derived from abdominal wall muscles. Flutamide and capsaicin pretreatment disrupts development.

Conclusion

Rat cremaster muscle develops as a strip, bearing close resemblance to human cremaster muscle, permitting extrapolation of cremaster function to human testicular descent. The cremaster muscle appears to differentiate from the gubernacular tip during elongation to the scrotum, and requires intact sensory innervation and androgen.  相似文献   
56.
During liver transplantation, the patient is at risk of developing progressive lactic acidosis. Following reperfusion, correction of acidosis may occur. In some patients, acidosis will worsen, a phenomenon referred to as persistent acidosis after reperfusion (PAAR). We compared postoperative outcomes in patients who manifested PAAR vs those that did not. All adult patients undergoing liver transplantation from 2002 to 2015 were included. PAAR is defined by the presence of a significant negative slope coefficient for base excess values measured after hepatic artery anastomosis through 72 hours postoperatively. Primary outcome was a composite of 30‐day and in‐hospital mortality. Secondary outcomes included: ICU LOS, total hospital LOS, and re‐transplantation rate within 7 days. PAAR occurred in 10% of the transplant recipients. Patients with PAAR had higher MELD, BMI, and eGFR and demonstrated a longer median ICU LOS and hospital median LOS with a trend toward mortality difference. But, after propensity matching, the mortality rate difference became significantly higher in patients with PAAR compared with matched controls while the ICU LOS differences disappeared. The re‐transplantation rates were similar also between the PAAR and no PAAR groups. The cohort with PAAR had a significant 30‐day and in‐hospital increase in mortality after propensity score matching.  相似文献   
57.
Enhancing the quantity and quality of cancellous bone with anabolic pharmacologic agents may lead to more successful outcomes of non-cemented joint replacements. Using a novel rabbit model of cancellous bone loading, we examined two specific questions regarding bone formation at the bone–implant interface: (1) does the administration of intermittent PTH, a potent anabolic agent, and mechanical loading individually and combined enhance the peri-implant cancellous bone volume fraction; and, (2) does surgical trauma enhance the anabolic effect of PTH on peri-implant bone volume fraction. In this model, PTH enhanced peri-implant bone volume fraction by 30% in loaded bone, while mechanical loading alone increased bone volume fraction modestly (+ 10%). Combined mechanical loading and PTH treatment had no synergistic effect on any cancellous parameters. However, a strong combined effect was found in bone volume fraction with combined surgery and PTH treatment (+ 34%) compared to intact control limbs. Adaptive changes in the cancellous bone tissue included increased ultimate stress and enhanced remodeling activity. The number of proliferative osteoblasts increased as did their expression of pro-collagen 1 and PTH receptor 1, and the number of TRAP positive osteoclasts also increased. In summary, both loading and intermittent PTH treatment enhanced peri-implant bone volume, and surgery and PTH treatment had a strong combined effect. This finding is of clinical importance since enhancing early osseointegration in the post-surgical period has numerous potential benefits.  相似文献   
58.
Objectives: Antipsychotic-induced weight gain (AIWG) is a common side effect of treatment with antipsychotics such as clozapine and olanzapine. The orexin gene and its receptors are expressed in the hypothalamus and have been associated with maintenance of energy homeostasis. In this study, we have analysed tagging single nucleotide polymorphisms (SNPs) in orexin receptors 1 and 2 (HCRTR1 and HCRTR2) for association with AIWG. Methods: Schizophrenia or schizoaffective disorder subjects (n?=?218), treated mostly with clozapine and olanzapine for up to 14 weeks, were included. Replication was conducted in a subset of CATIE samples (n?=?122) treated with either olanzapine or risperidone for up to 190 days. Association between SNPs and AIWG was assessed using analysis of covariance (ANCOVA) with baseline weight and duration of treatment as covariates. Results: Several SNPs in HCRTR2 were nominally associated with AIWG in patients of European ancestry treated with either clozapine or olanzapine (P<0.05). In the replication analysis two SNPs rs3134701 (P?=?0.043) and rs12662510 (P?=?0.012) were nominally associated with AIWG. None of the SNPs in HCRTR1 were associated with AIWG. Conclusion: This study provides preliminary evidence supporting the role of HCRTR2 in AIWG. However, these results need to be confirmed in large study samples.  相似文献   
59.
60.

Background

The use of non-cultured autologous cells to promote wound healing and in reconstructive procedures is increasing. One common method for preparing these cells is the use of the ReCell® device. However, despite its current clinical use, no characterisation of the cell suspension produced using a ReCell® device has been published.

Objective

To characterise the ReCell suspension that is applied to wounds for cell type, viability, yield, stability and proliferative potential.

Methods

The ReCell® device was used to harvest cells from a 2 cm2 piece of split-thickness skin isolated using a dermatome. The resulting cell suspension was analysed for cell yield, cell type, viability over time, proliferative potential and reproducibility.

Results

Average viable cell yield was 1.7 × 106/cm2 of tissue, with 75.5% of the total cell isolate viable. Total viable cell number was not significantly reduced after 4 h storage at 22 °C or 4 °C, and was stable for 24 h at 4 °C. Proliferative potential was assessed using a colony forming assay, with 0.3% of viable cells isolated forming keratinocyte colonies. Predominantly the suspension contained keratinocytes (64.3 ± 28.8%) and fibroblasts (30.3 ± 14.0%), with a small population of melanocytes also identified (3.5 ± 0.5%). Finally, the supernatant contained low total protein (0.92 mg/ml) and the supernatant had no significant effects on cell viability or growth when applied ex vivo.

Conclusions

These results suggest the ReCell® device provides a method for the preparation of a cell suspension with high viability and proliferative potential, containing viable melanocytes and no apparent toxic cell debris. Further work on the sustained viability of these cells in vivo, and in particular after application to the wound, will be important to better understand the potential of the ReCell® device in the clinic.  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