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   1119149篇
  免费   75286篇
  国内免费   1475篇
耳鼻咽喉   15357篇
儿科学   36387篇
妇产科学   29866篇
基础医学   159769篇
口腔科学   30485篇
临床医学   101078篇
内科学   212050篇
皮肤病学   25236篇
神经病学   85976篇
特种医学   44134篇
外国民族医学   202篇
外科学   166976篇
综合类   22082篇
现状与发展   1篇
一般理论   325篇
预防医学   80039篇
眼科学   25182篇
药学   88659篇
  9篇
中国医学   2849篇
肿瘤学   69248篇
  2021年   8701篇
  2019年   9044篇
  2018年   12712篇
  2017年   10002篇
  2016年   11328篇
  2015年   12558篇
  2014年   16940篇
  2013年   24647篇
  2012年   33912篇
  2011年   35778篇
  2010年   20877篇
  2009年   19539篇
  2008年   32828篇
  2007年   34993篇
  2006年   35616篇
  2005年   33775篇
  2004年   32378篇
  2003年   31020篇
  2002年   29748篇
  2001年   60392篇
  2000年   61761篇
  1999年   51244篇
  1998年   12954篇
  1997年   11381篇
  1996年   11347篇
  1995年   10643篇
  1994年   9603篇
  1993年   9112篇
  1992年   37982篇
  1991年   36443篇
  1990年   35890篇
  1989年   34397篇
  1988年   30991篇
  1987年   30085篇
  1986年   28317篇
  1985年   26549篇
  1984年   19283篇
  1983年   16211篇
  1982年   8943篇
  1979年   17090篇
  1978年   11467篇
  1977年   10277篇
  1976年   8881篇
  1975年   10103篇
  1974年   11691篇
  1973年   11306篇
  1972年   10787篇
  1971年   10126篇
  1970年   9273篇
  1969年   8954篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
Four clinical trials of porcine islet transplantation have been reported, and there are verbal reports that clinical trials on much larger scales are continuing in centers in China and Russia. The four reported trials are briefly reviewed and, in the light of the present status of experimental islet xenotransplantation, consideration is given to whether such trials are currently justified. The Ethics Committee of the International Xenotransplantation Association has (1) emphasized the need for encouraging studies in non-human primates before clinical trials should be undertaken, (2) mandatory monitoring for the transfer of porcine microorganisms, and (3) careful regulation and oversight by recognized bodies. Other aspects of the topic, such as the need for informed consent, are briefly discussed. We conclude that, at the present time, more data documenting convincing efficacy, focused on clinically applicable immunosuppressive regimens, are needed to justify the initiation of closely monitored clinical trials. A clinical trial may then be justified even though the potential risk to the patients, and possibly for society, will not be zero.  相似文献   
84.
85.
OBJECTIVE: To determine whether under-reporting of rheumatic fever occurs at hospital, municipal, provincial and national levels of the South African health system. BACKGROUND: Information on the incidence of rheumatic fever (RF) and the prevalence of rheumatic heart disease (RHD) is required for the prevention of valvular heart disease in developing countries. In South Africa, RF was made a notifiable condition in 1989. It has recently been suggested that the reporting of RF cases may be incomplete, possibly because of underreporting by health care professionals and deficient administration of the disease notification system in South Africa. METHOD AND RESULTS: We assessed whether underreporting of RF cases occurs by comparing the numbers of RF cases reported per year at hospital, municipal, provincial and national levels from 1990 to 2004. There was a fall in the number of RF cases reported per year at national and provincial level over the 15 years of observation. A detailed analysis of the number of RF cases reported at hospital, municipal and provincial level for a 5-year period showed that more cases were diagnosed in one hospital (serving a smaller population) than were captured at municipal and provincial level (serving a larger population), suggesting underreporting by health care professionals. There were discrepancies in the number of cases reported at municipal, provincial and national level, suggesting poor administration of the notification system. CONCLUSION: There appears to be underreporting of RF cases by health care professionals, and poor administration of the RF notification system. Health care professionals need to be educated about the statutory requirement to notify all RF cases in South Africa. An effective national disease notification system is required.  相似文献   
86.
87.
88.
89.
INTRODUCTION: Vasopressin, mainly through the V1a-receptor, is thought to be a major player in the maintenance of hyperfiltration. Its inhibition could therefore lead to a decrease in progression of chronic renal failure. To this end, the effect of the vasopressin V1a-receptor-selective antagonist, YM218, was studied on proteinuria and focal glomerulosclerosis in early and late intervention after 5/6 nephrectomy in rats, and compared with an angiotensin-converting enzyme inhibitor (ACE-I). MATERIALS AND METHODS: After 5/6 nephrectomy, early intervention was performed between week 2 and 10 thereafter with the V1a-receptor-selective antagonist (VRA, 10 mg/kg/day, n=10), enalapril (ACE-I, 10 mg/kg/day, n=9), or vehicle (n=8). Late intervention was performed in another group between week 6 and 12 with VRA (10 mg/kg/day, n=7), lisinopril (ACE-I, 5 mg/kg/day, n=7), or vehicle (n=7). RESULTS: In early intervention, proteinuria and focal glomerulosclerosis were significantly decreased by VRA compared to vehicle (44+7% and 59+8% respectively). ACE-I significantly decreased proteinuria (67+7%) and a trend towards a decrease in focal glomerulosclerosis was observed (30+18%). In late intervention, VRA did not decrease proteinuria and focal glomerulosclerosis compared to vehicle (21+20% and 0%, respectively), ACE-I significantly lowered proteinuria (92+2%) and a focal glomerulosclerosis (69+1%) lowering trend was observed. CONCLUSION: These results indicate that VRA may protect against early progression of renal injury after 5/6 nephrectomy, whereas its effectiveness seems limited in established renal damage.  相似文献   
90.
This is the third and final part of a series of articles that report the findings of a study that investigated the effects of a summer externship program on the transition into a professional role among nurses who participated in a summer nurse externship program at an acute care pediatric hospital. Specifically, this article reports the retention and recruitment benefits of a summer nurse externship program for the institution from 1998 through 2003. A total of 153 externs out of the 193 (79.0%) assumed a registered nurse position at the institution, and 77% remained in that role for 12 months. Overall, the nurse extern program for this institution appeared to be an effective recruitment and retention strategy that is on par with the institution and national data for retention and turnover data.  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