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   1256578篇
  免费   73634篇
  国内免费   1420篇
耳鼻咽喉   16289篇
儿科学   41445篇
妇产科学   31854篇
基础医学   170368篇
口腔科学   31287篇
临床医学   107886篇
内科学   236490篇
皮肤病学   25299篇
神经病学   97882篇
特种医学   52030篇
外国民族医学   201篇
外科学   193286篇
综合类   24333篇
现状与发展   1篇
一般理论   266篇
预防医学   92478篇
眼科学   27884篇
药学   96255篇
  8篇
中国医学   3496篇
肿瘤学   82594篇
  2021年   8242篇
  2019年   8330篇
  2018年   32559篇
  2017年   25641篇
  2016年   28928篇
  2015年   12559篇
  2014年   16683篇
  2013年   23714篇
  2012年   38334篇
  2011年   53217篇
  2010年   37307篇
  2009年   29235篇
  2008年   49231篇
  2007年   53471篇
  2006年   33949篇
  2005年   33772篇
  2004年   33598篇
  2003年   33228篇
  2002年   30332篇
  2001年   60583篇
  2000年   62207篇
  1999年   51360篇
  1998年   12757篇
  1997年   11289篇
  1996年   11176篇
  1995年   10501篇
  1994年   9519篇
  1993年   8974篇
  1992年   38008篇
  1991年   36531篇
  1990年   36013篇
  1989年   34502篇
  1988年   31025篇
  1987年   30128篇
  1986年   28342篇
  1985年   26576篇
  1984年   19302篇
  1983年   16234篇
  1982年   8888篇
  1979年   17115篇
  1978年   11473篇
  1977年   10270篇
  1976年   8892篇
  1975年   10107篇
  1974年   11729篇
  1973年   11351篇
  1972年   10825篇
  1971年   10139篇
  1970年   9318篇
  1969年   8985篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The aim of the present study was to explore differences in the clinical expression, clinical diagnoses and management of airway diseases in a primary-care setting. Patients aged >or=35 yrs who had ever smoked were enrolled when they presented for any reason to one of eight rural primary-care practices. Respiratory symptom questionnaires and spirometry were administered. In total, 1,034 patients had acceptable and reproducible spirometry, of whom 550 (53%) were males and 484 (47%) were females. Males smoked more than females (41.2 versus 29.2 pack-yrs) respectively, and were more likely to have a pre-bronchodilator forced expiratory volume in one second/forced vital capacity <0.70 at 22.4 versus 11.8%, respectively. However, more females than males reported breathlessness (51.0 versus 42.8%, respectively), a prior diagnosis compatible with airflow obstruction and taking respiratory medications (23.4 versus 14.9%, respectively). In conclusion, the current results suggest that females are more likely than males to report breathlessness and be prescribed respiratory medications independent of differences in the severity of airflow obstruction.  相似文献   
42.
This study was performed to evaluate the surgical strategy in patients with calvarial tumours, in order to design and modify a robot-assisted trepanation system. A total of 75 patients underwent craniectomy for the treatment of calvarial tumours during the 10-year period from 1993 to 2002. The patients' complaints, the size, location and histology of the tumour, and the various cranioplasty techniques used were analysed retrospectively. In a second procedure several craniectomies at typical locations according to the study's results were performed in a laboratory setting using a hexapod robotic tool, constructed at the Helmholtz-Institute, RWTH Aachen University, and plastic model heads. The workflow was documented and the reproducibility and the accuracy of the procedure were registered. A total of 83 surgical procedures were performed on 75 patients. The majority (87 %) of lesions treated surgically were located in the frontal, temporal and anterior parts of the parietal region. Histological examination revealed benign lesions in 66 % of the patients and dural involvement in 46 %. According to these results craniectomies were performed using the robotic system. Mean positioning accuracy of the robotic system while milling was 0.24 mm, with a standard deviation of 0.04 mm, and maximum error under 1 mm. Craniectomies leaving a 1-mm layer of the tabula interna intact to ensure a healthy dura were performed in several regions successfully. The majority of calvarial tumours, requiring surgical treatment in our patients, were located in cosmetically relevant areas in which drilling can be carried out with the robotic trepanation system. Consequently, the surgical approach had to be planned carefully in order to achieve a good cosmetic outcome.  相似文献   
43.
44.
45.
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   
46.
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   
47.
48.
49.
Both vascular surgery and endovascular interventions traumatise the arterial wall, especially the endothelium. The vessel responds with neointimal hyperplasia and/or constrictive remodelling, and this is still the limiting factor in curative interventions. Stent placement prevents constrictive remodelling but is the main trigger for in-stent restenosis. Hyperproliferation of neointimal tissue is the main response to arterial thrombosis, local inflammation or medio-intimal injury such as occurs, for example, after balloon dilatation in the region of arterial anastomoses or of a thrombectomy (Fogarty-manoeuvre). At present, research on prevention of restenosis is focused on inhibiting neointimal hyperproliferation by using drug-eluting stents, and especially sirolimus- or paclitaxel-eluting stents. In addition, further experimental research work is in progress, with the aim of esablishing new treatment regimens and solving the problem of neointimal formation, thrombosis and constrictive remodelling. These include both local and systemic pharmacological therapy, brachy- and laser therapy, and many genetic treatment options, some of which are currently the subjects of experimental studies and early-stage clinical trials. Gene therapy seems like a promising way of preventing restenosis, but has not yet been tested in clinical trials. In the near future, selective, simultaneous, and perhaps even polyphasic regulation for gene silencing of two or more genes involved in the development of restenosis could improve the long-term patency rate.  相似文献   
50.
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