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   53066篇
  免费   3585篇
  国内免费   181篇
耳鼻咽喉   601篇
儿科学   1067篇
妇产科学   792篇
基础医学   6786篇
口腔科学   693篇
临床医学   4895篇
内科学   12846篇
皮肤病学   532篇
神经病学   5188篇
特种医学   2100篇
外科学   8471篇
综合类   587篇
一般理论   65篇
预防医学   3656篇
眼科学   926篇
药学   3186篇
中国医学   49篇
肿瘤学   4392篇
  2024年   42篇
  2023年   286篇
  2022年   601篇
  2021年   1435篇
  2020年   900篇
  2019年   1294篇
  2018年   1641篇
  2017年   1118篇
  2016年   1206篇
  2015年   1440篇
  2014年   2162篇
  2013年   2510篇
  2012年   4324篇
  2011年   4290篇
  2010年   2401篇
  2009年   2149篇
  2008年   3754篇
  2007年   3864篇
  2006年   3739篇
  2005年   3682篇
  2004年   3283篇
  2003年   3025篇
  2002年   2736篇
  2001年   316篇
  2000年   221篇
  1999年   327篇
  1998年   488篇
  1997年   439篇
  1996年   357篇
  1995年   324篇
  1994年   251篇
  1993年   236篇
  1992年   142篇
  1991年   126篇
  1990年   113篇
  1989年   95篇
  1988年   87篇
  1987年   68篇
  1986年   75篇
  1985年   100篇
  1984年   121篇
  1983年   105篇
  1982年   136篇
  1981年   109篇
  1980年   95篇
  1979年   42篇
  1978年   60篇
  1977年   57篇
  1976年   49篇
  1975年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
OBJECTIVE: The study goal was to critically evaluate 3 popular noninvasive treatments for snoring: an oral spray lubricant applied before bedtime, a nasal strip designed to maintain nasal valve patency, and a head-positioning pillow. STUDY DESIGN: Prospective, randomized blinded clinical trial of 3 popular noninvasive snore aids using objective acoustic snoring analysis and subjective patient and bed-partner questionnaires in 40 snoring patients. A digital recorder allowed snoring analysis with data collected in the home environment over 1 week. RESULTS: There is neither objective nor subjective benefit to the use of tested popular noninvasive snore aids. Palatal snoring, palatal loudness, average loudness of snoring, averaged palatal flutter frequency, and respiratory disturbance index did not significantly change when comparing the 3 snoring aids with no treatment. Subjective comments and complications are reviewed as well. CONCLUSION: This is the first prospective comparison trial of popular noninvasive snoring aids. There is no significant objective or subjective snoring improvement in the anti-snoring aids studied compared with the use of no aid. SIGNIFICANCE: Outcome studies aid in verifying or refuting claims made by popular noninvasive snore aids.  相似文献   
32.
BACKGROUND: To ascertain survival of ischemic advanced heart failure patients by treatment allocation, we examined the outcome of transplant assessment patients allocated to medical therapy, high-risk conventional surgery, or transplantation. METHODS: Patients were identified from the Papworth transplant database and excluded if primary etiology was not ischemic. Grouping was undertaken according to treatment allocation at initial assessment, and analysis was performed by intention to treat. Survival was computed from the time of assessment and Cox regression used to stratify patients according risk with the Heart Failure Survival Score. RESULTS: From May 1993 to September 2001, a total of 755 patients were admitted for transplant assessment, with 348 (46.1%) identified as having heart failure of ischemic origin. Variables required for calculation of the Heart Failure Survival Score was available in 273 patients (78.4%), and 20 patients (7.3%) were lost to follow-up. Of the remaining 253 patients, 89 (35.2%) were allocated to medical therapy, 32 (12.6%) to surgery, and 132 (52.2%) to transplantation. The relative risk (95% confidence limit) of death compared with medical therapy was 0.62 (0.28, 1.40) for surgery and 0.38 (0.24, 0.61) for transplantation in medium- to high-risk patients. For low-risk patients, the relative risks for death compared with medical therapy were 1.87 (0.63, 5.60) for surgery and 1.97 (0.79, 4.96) for transplantation. CONCLUSIONS: Transplantation improved survival of medium- and high-risk patients compared with medical therapy. In the low-risk group, this was not evident. However, repeated assessment of risk is required because the hazard for death rises steadily after the third year in these patients.  相似文献   
33.
Paul L. Booth  W. Eric Thomas   《Brain research》1991,548(1-2):163-171
Ramified microglial cells were investigated in primary cultures of dissociated cerebral cortical tissue from rats. The identification of these cells was confirmed through immunohistochemical staining with 7 monoclonal antibodies selective for microglia. While there was significant variation in staining intensity with different antibodies, all stained the identified ramified cells; the antibodies OX-42 and ED1 yielded the most intense immunoreactivity. Based on distinctive morphological features, the microglia could be identified in living cultures where they were monitored using time-lapse video recording. This technique revealed extremely dynamic features of cellular plasticity and motility. Ramified microglia exhibited constant and rapid alterations in the size and shape of their cell body with an associated extension and retraction of processes; concomitantly, the cells moved about in a circumscribed area. These features of plasticity and motility were unique to this cell type, and correlated with OX-42 immunostaining. The microglia also possessed a differentially high level of pinocytotic activity; this too was correlated with OX-42 staining. From the nature of their morphological plasticity and motility, high pinocytosis, and cellular distribution, it is hypothesized that the ramified microglia specifically function as a system of fluid cleansing in normal brain tissue.  相似文献   
34.
35.
36.
OBJECTIVE: The aim of this paper is to assess the accuracy of an algorithm implemented by PRAXIM in the SURGETICS navigation station for detection of the hip center. This study will assess the robustness and accuracy of the algorithm in various clinical situations such as those involving non-sphericity of the femoral head, motion of the pelvis during hip center detection, and restricted range of motion. MATERIALS AND METHODS: The localization of the hip center, based on kinematics, relies on the recording of n successive positions of the femoral rigid body in the localizer reference system during a passive circumduction motion of the hip joint. Therefore, the shape of the clouds of points acquired may vary from one acquisition to the next. To allow a comprehensive study of the consequences of these variations for hip center detection, we developed a simulator to generate numerous clouds of points. Results given subsequently for each test are the values of the difference between the femoral mechanical axis computed with C(c), the computed hip center, and the same axis computed with C(o), the reference hip center. RESULTS: Test 1: Sensitivity to noise. The errors ranged from 3.33 E - 12 (SD 3.29E - 12) for a noise of 0 mm to 8.18E - 1 (SD - 7.05E - 1) for a noise of 15 mm. Test 2: Sensitivity to the shape of the acquisition motion. All trajectories gave an error < 1 degrees . Test 3: Sensitivity to restricted range of motion. No value > 1 degrees was found during this test. Test 4: Sensitivity to the distance between two points of the cloud. No value > 0.5 degrees was found during this test. Test 5: Sensitivity to the number of points included in the cloud. No value > 1 degrees was found during this test. CONCLUSIONS: The Surgetics algorithm is robust to noise, can compensate for pelvic motion, and can be used even in the case of restricted range of motion.  相似文献   
37.
38.
Despite recent improvement, significant racial disparities in outcome still persist after renal transplantation among African American patients in the United States. This study evaluated the association of race and ethnicity with allograft outcomes in a French population of 952 Caucasian (Cauc) patients and 140 African European (AE) patients who underwent renal transplantation in our center between 1987 and 2003. Demographic characteristics were similar for the two cohorts other than cause of end-stage renal failure (more hypertension among AE and more polycystic kidney disease among Cauc) and cold ischemia time (significantly longer for AE). Immunosuppressive treatment was comparable between groups. There were no significant differences between AE and Cauc in the incidence of acute rejection (31% vs. 30%). At 5 years post-transplant, patient survival (93% vs. 92%), graft survival (83% in both groups) and graft function (creatinine clearance 48 mL/min vs. 45 mL/min) were also similar among the AE and Cauc patients. We demonstrate that ethnic origin does not affect outcome after renal transplantation in France. Therefore, differences observed in the United States cannot be only related to immunologic or pharmacologic factors. The results of renal transplantation in patients of African origin could be improved with universal immunosuppressive drug coverage.  相似文献   
39.
40.
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