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   16007篇
  免费   1090篇
  国内免费   272篇
耳鼻咽喉   230篇
儿科学   217篇
妇产科学   168篇
基础医学   2561篇
口腔科学   319篇
临床医学   1511篇
内科学   3123篇
皮肤病学   519篇
神经病学   1077篇
特种医学   1454篇
外科学   1838篇
综合类   145篇
一般理论   3篇
预防医学   559篇
眼科学   245篇
药学   1895篇
中国医学   271篇
肿瘤学   1234篇
  2024年   11篇
  2023年   142篇
  2022年   483篇
  2021年   682篇
  2020年   331篇
  2019年   472篇
  2018年   569篇
  2017年   503篇
  2016年   681篇
  2015年   890篇
  2014年   1071篇
  2013年   1159篇
  2012年   1488篇
  2011年   1510篇
  2010年   949篇
  2009年   739篇
  2008年   904篇
  2007年   905篇
  2006年   720篇
  2005年   656篇
  2004年   574篇
  2003年   411篇
  2002年   322篇
  2001年   195篇
  2000年   148篇
  1999年   95篇
  1998年   122篇
  1997年   93篇
  1996年   83篇
  1995年   61篇
  1994年   57篇
  1993年   49篇
  1992年   32篇
  1991年   19篇
  1990年   29篇
  1989年   32篇
  1988年   30篇
  1987年   16篇
  1986年   27篇
  1985年   23篇
  1984年   9篇
  1983年   15篇
  1982年   9篇
  1981年   4篇
  1980年   8篇
  1979年   4篇
  1978年   6篇
  1977年   6篇
  1976年   14篇
  1975年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Pure neuronal and mixed neuronal-glial tumors of the central nervous system are uncommon but fascinating because they are less aggressive than the more common glial tumors and their prognosis is excellent. Neurologic manifestations are varied and include seizures, symptoms of increased intracranial pressure, and neurologic deficits according to tumor location. Many neuronal tumors of the central nervous system demonstrate characteristic radiologic findings. At magnetic resonance (MR) imaging, gangliocytomas demonstrate low signal intensity on T1-weighted images, high signal intensity on T2-weighted images, and frequent enhancement on gadolinium-enhanced T1-weighted images. Characteristic MR imaging findings of Lhermitte-Duclos disease are a nonenhancing mass in a cerebellar hemisphere with a striated pattern. Central neurocytomas are typically located in the lateral ventricles near the foramen of Monro with a characteristic attachment to the septum pellucidum. Ganglioneurocytoma is a rare variant of central neurocytoma that is characterized by differentiation toward ganglion cells. In ganglioglioma, a well-defined cystic mass with a solid mural nodule is typically seen. Extension of enhancement to the leptomeninges is characteristic of desmoplastic infantile ganglioglioma and correlates with the firm dural attachment of the solid component. Dysembryoplastic neuroepithelial tumor has a well-demarcated, multilobulated or gyriform appearance.  相似文献   
92.
High-resolution MRA with phase/frequency flow compensation may require very long echo times (TEs). Variable TE (VTE) was implemented into flow-compensated 3D TOF to minimize the effective TE and reduce the flow-related signal void. The k-space of the 3D TOF was divided into segment groups ranging from two to 32 segments with different TEs. The TEs were minimized and the flow-compensation gradient lobes were calculated to null the total first moment at the peak of the echo for each segment. Possible artifacts and off-resonance effects were evaluated, with respect to the number of TE segments, using the point spread function (PSF) and corresponding experiments. The optimal number of TE segments for the least artifact was determined to be one-half of the number of slices. Two types of artifacts caused by VTE were predicted and subsequently observed. The developed pulse sequence 3D TOF-VTE was tested on clinical MRI systems, by performing scans of the cervical carotid artery and intracranial carotid artery at the carotid siphon. The signal distribution near the bifurcation and the siphon was much more uniform with VTE, and the flow-related signal loss was greatly reduced. The resultant MR angiograms provided improved vessel detail. The results show that VTE improved the quality of flow-compensated 3D TOF MRA.  相似文献   
93.
Ham WS  Jeong HJ  Han SW  Kim JH  Kim DK 《The Journal of urology》2004,172(3):1108-1110
PURPOSE: Increasing clinical importance is being placed on the role of differential renal function (DRF) in the management of congenital ureteropelvic junction obstruction. Supranormal DRF of the hydronephrotic kidney on renal scan is a puzzling phenomenon and is hypothesized to be due to an increase in single nephron filtration or nephron volume without sound evidence. We studied the histopathological changes of hydronephrotic kidneys to determine whether glomerular hypertrophy underlies supranormal DRF. MATERIALS AND METHODS: We retrospectively evaluated the records of 3 females and 32 males with unilateral congenital hydronephrosis who underwent pyeloplasty. Mean patient age at operation was 12.6 months (range 0.1 to 144). Needle biopsies from 3 different sites at the lower pole of the kidney were performed during surgery. To evaluate the presence of glomerular hypertrophy, the maximal planar area of glomeruli was measured under light microscopy using an image analyzer. Tissue samples obtained from kidneys without a history of urinary tract disease at autopsy were used as controls. The mean glomerular areas of the patient and control groups were evaluated according to DRF and age. RESULTS: The mean glomerular area values of the patient group were smaller than those of the control group, except for 4 patients. The glomerular areas of the hydronephrotic kidneys with supranormal DRF were not significantly different from those of the control group. Instead, the probability of larger renal glomeruli increased with decreasing DRF (p = 0.1155). CONCLUSIONS: Increased nephron volume can be discounted as a cause of supranormal DRF.  相似文献   
94.

Background

The purpose of this study is to report a modified transtibial technique to approach the center of anatomical femoral footprint in anterior cruciate ligament (ACL) reconstruction and to investigate the accurate femoral tunnel position with 3-dimensional computed tomography (3D-CT) and radiography after reconstruction.

Methods

From December 2010 to October 2011, we evaluated 98 patients who underwent primary ACL reconstruction using a modified transtibial technique to approach the center of anatomical femoral footprint in single bundle ACL reconstruction with hamstring autograft. Their femoral tunnel positions were investigated with 3D-CT and radiography postoperatively. Femoral tunnel angle was measured on the postoperative anteroposterior (AP) radiograph and the center of the femoral tunnel aperture on the lateral femoral condyle was assessed with 3D-CT according to the quadrant method by two orthopedic surgeons.

Results

According to the quadrant method with 3D-CT, the femoral tunnel was measured at a mean of 32.94% ± 5.16% from the proximal condylar surface (parallel to the Blumensaat line) and 41.89% ± 5.58% from the notch roof (perpendicular to the Blumensaat line) with good interobserver (intraclass correlation coefficients [ICC], 0.766 and 0.793, respectively) and intraobserver reliability (ICC, 0.875 and 0.893, respectively). According to the radiographic measurement on the AP view, the femoral tunnel angles averaged 50.43° ± 7.04° (ICC, 0.783 and 0.911, respectively).

Conclusions

Our modified transtibial technique is anticipated to provide more anatomical placement of the femoral tunnel during ACL reconstruction than the former traditional transtibial techniques.  相似文献   
95.
Nam SH  Jeong JH  Che X  Lim KE  Nam H  Park JS  Choi JY 《BONE》2012,50(1):149-155
We investigated the therapeutic effect of topical Risedronate (RIS) on a mouse model of estrogen-deficient osteoporosis. Fourteen-week-old female mice were ovariectomized and assigned to 4 groups: SHAM-operated (SHAM), OVX mice treated with vehicle (OVX-V), OVX mice treated with 0.2% RIS (OVX-0.2% RIS), and OVX-mice treated with 0.02% RIS (OVX-0.02% RIS). Topical samples containing RIS were prepared in 10% (w/w) polyethylene glycol (PEG, MW 400) and 80 μg of sample was spread on the mice's mid-backs every 3 days for 5 weeks. Micro-CT analysis of femora demonstrated that OVX-0.2% RIS exhibited a 29% greater bone mineral density and 24% greater bone volume fraction than that of OVX-V group. Investigation of the trabecular bone in OVX-0.2% RIS revealed a 24% higher bone volume (BV/TV), 51% higher trabecular number (Tb.N), and 40% lower trabecular separation (Tb.Sp) compared to OVX-V mice. Additionally, bone phenotypes of tibiae were further confirmed by histological analysis. OVX-0.2% RIS group exhibited a 494% greater BV/TV, 464% less Tb.Sp, 81% greater active osteoclast surface (Oc.S/BS) and 26% less osteoclast number (N.Oc/BS) than that of OVX-V group. Collectively, these results indicated that topical delivery of RIS has powerful pharmaceutical effects on the prevention of osteoporosis and bone turnover.  相似文献   
96.
Jeong O  Cho SB  Joo YE  Ryu SY  Park YK 《Surgical endoscopy》2012,26(6):1778-1783

Background

Knowledge of the intraoperative location of lesions is a prerequisite for deciding the proper extent of gastric resection or the choice of anastomosis technique during totally laparoscopic distal gastrectomy (TLDG) for early gastric cancer (EGC). In this study we introduce a novel tumor localization method for TLDG: endoscopic blood tattooing.

Methods

Twenty-three consecutive patients scheduled for TLDG for EGC were enrolled in this prospective study. The day before surgery, 2–3?ml of autologous blood was injected into the gastric muscle layer at 3–4?cm proximal to the lesion during endoscopy.

Results

The study subjects consisted of 15 males and 8 females with a mean age of 61?±?10.4?years. During surgery, the endoscopic blood tattooed sites were successfully identified in all 23 patients. No complications associated with the procedure occurred, and no patient had microscopic residual tumor cells at the proximal resection margin, with a mean proximal margin length of 3.3?±?2.7?cm. Eighteen patients underwent TLDG with Billroth II anastomosis, four patients with Roux-en-Y gastrojejunostomy, and one patient with laparoscopic total gastrectomy. At final pathologic examinations, 20 patients were of stage IA and 3 were of stage IB according to the UICC TNM classification (6th ed.).

Conclusions

Endoscopic blood tattooing provides a simple and useful means of localizing lesions during TLDG for EGC. Although the superiority of this technique over other localization methods needs to be evaluated further, the authors recommend endoscopic blood tattooing as an alternative to other intraoperative localization methods for laparoscopic surgery for EGC.  相似文献   
97.
This prospective study evaluated the safety of tadalafil 5 mg taken once a day in terms of hypotensive side effects and whether it improves lower urinary tract symptoms (LUTS) and restores sexual function in patients with erectile dysfunction who are receiving concomitant α-blocker (AB) therapy for benign prostatic hyperplasia (BPH). A total of 158 LUTS/BPH patients receiving AB therapy for ≥3 months were given tadalafil 5 mg once a day. Before treatment with tadalafil (V1), and 4 weeks (V2) and 12 weeks (V3) after starting tadalafil, blood pressure, heart rate, International Prostate Symptom Score (IPSS), maximal urine flow rate (Qmax), postvoiding residual urine volume, and International Index of Erectile Function (IIEF-5) score were measured. Of the 158 LUTS/BPH patients, a total of 119 completed the trial. Blood pressure (systolic and diastolic) and heart rate did not change. IPSS and IIEF-5 scores improved significantly, but Qmax and postvoiding residual urine volume did not; however, in the 39 men with a low baseline Qmax (≤10 mL/s), Qmax rose significantly from 7.97 ± 1.44 mL/s (baseline) to 8.91 ± 1.60 mL/s (V3; P = .012). The remaining patients (baseline Qmax >10 mL/s) did not change. At V2 and V3, adverse side effects were observed in 10 men (7.30%) and 6 men (5.04%), respectively. Facial flushing was the most common adverse side effect (6 men at V2 and 4 men at V3), followed by headache (2 men each at V2 and V3) and dizziness (2 men at V2). Two patients dropped out of the study because of adverse side effects. In conclusion, tadalafil 5 mg once a day in combination with AB appeared to have few adverse effects on hypotensive events and can improve LUTS and restore sexual function.  相似文献   
98.
Lim BJ  Jeong JY  Chang YK  Na KR  Lee KW  Shin YT  Choi DE 《Renal failure》2012,34(7):892-900
Although cisplatin is a highly effective antineoplastic agent, nephrotoxicity is its major clinical problem. Recently, it was reported that Spirulina, a blue-green algae, has potent antioxidant properties. The aim of this study was to establish the possible protective role of C-phycocyanin (PC), one of the active ingredients of Spirulina, against cisplatin-induced nephrotoxicity. This study was carried out using human kidney-2 (HK-2) cells and male C57BL6 mice. Cells and mice were divided into four groups; untreated control group, PC-treated control group, cisplatin-treated group, and PC plus cisplatin-treated group. The molecular, functional, and structural parameters were measured. PC significantly attenuated blood urea nitrogen, serum creatinine, renal histological damages, and apoptotic cell death in cisplatin-treated mice. The cisplatin-induced cell death was significantly attenuated in cells pretreated with PC. PC also significantly attenuated the elevation of p-ERK, p-JNK, and p-p38 induced by cisplatin treatment. The expression of Bax, caspase-9, and caspase-3 in cisplatin-treated cells were also decreased by PC treatment. In conclusion, PC ameliorates cisplatin-induced nephrotoxicity and, at least in part, suppression of p-ERK, p-JNK, p-p38, Bax, caspase-9, and caspase-3 may be involved in this mechanism.  相似文献   
99.

Introduction

Preoperative factors favoring the performance of non-orthotopic bladder substitution (OBS) after radical cystectomy for muscle-invasive bladder cancer were identified.

Patients and methods

We retrospectively reviewed the medical records of 730 patients who underwent radical cystectomy for urothelial carcinoma of the bladder. After excluding 75 patients who were unable to undergo OBS due to the tumor location or elevated serum creatinine level, we assessed the preoperative factors in the remaining 655 patients. Multivariate logistic regression analysis was performed to identify the independent preoperative predictors of type of urinary diversion.

Results

Of the 655 patients, 171 (26.1%) underwent non-OBS. Patients who underwent non-OBS were more likely to be older and females, to have a lower educational status, non-organ confined disease, more comorbid medical conditions, more impaired performance status, lower body mass index, anemia, azotemia, and hypoalbuminemia, and to be treated by less-experienced surgeons (P?<?0.05 each). After adjusting for provider-based factors, multivariate analysis showed that factors independently associated with non-OBS included advanced age (odds ratio [OR] 4.10, P?<?0.001), female gender (OR 2.08, P?=?0.027), ECOG performance status (??1 vs 0, OR 5.20, P?<?0.001), low educational status (OR 1.59, P?=?0.042), clinically node-positive disease (OR 2.36, P?=?0.003), anemia (OR 1.67, P?=?0.041), azotemia (OR 3.97, P?<?0.001), and hypoalbuminemia (OR 1.84, P?=?0.046).

Conclusion

Several patient-based as well as provider-based factors were associated with the type of urinary diversion after radical cystectomy. Advanced age, female gender, low performance status, low education level, clinically node-positive disease, anemia, hypoalbuminemia, and azotemia were associated with non-OBS, as surgery was performed by relatively inexperienced surgeons.  相似文献   
100.

Background

We evaluated the clinical and radiologic results of impacted femoral neck fractures treated with multiple pinning and determined the influence of the progression of impaction at the fracture site on clinical outcome.

Methods

There were 34 patients with a mean age of 65.5 years. The mean follow-up period was 3.4 years. Progression of fracture site impaction was measured using an articulo-trochanteric distance index and the percentage decrease in the articulo-trochanteric distance index between follow-up intervals. The failure of treatment was clarified as non-union and avascular necrosis. Other characteristics of the patients, including mean waiting time for surgery, preoperative Singh index score, and body mass index, were also measured to evaluate the influence on the clinical outcome of surgery.

Results

There were 6 fractures which were not treated successfully (3 non-union, 8.8% and 3 avascular necrosis, 8.8%). The mean percentage decrease of the articulo-trochanteric distance index within the first 6 weeks after surgery was 4.5% in the successful group and 25.1% in the failure group (p < 0.001). There was also a significant mean percentage decrease in the articulo-trochanteric distance index between 6 weeks and 3 months (p < 0.001).

Conclusions

Primary stabilization with Knowles pins for impacted femoral neck fractures had a reasonable clinical outcome with low morbidity. Despite a significant difference of a mean percentage decrease in the articulo-trochanteric distance index between the successful group and the failure group, we could not verify it as a risk factor for failure of treatment because the odds ratio was not statistically significant.  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