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   876449篇
  免费   71278篇
  国内免费   1915篇
耳鼻咽喉   12901篇
儿科学   24993篇
妇产科学   25281篇
基础医学   126488篇
口腔科学   25764篇
临床医学   76485篇
内科学   167547篇
皮肤病学   17395篇
神经病学   71609篇
特种医学   35765篇
外国民族医学   171篇
外科学   138172篇
综合类   24652篇
现状与发展   2篇
一般理论   270篇
预防医学   67626篇
眼科学   20975篇
药学   65713篇
中国医学   1609篇
肿瘤学   46224篇
  2018年   7581篇
  2015年   8032篇
  2014年   11555篇
  2013年   17311篇
  2012年   23576篇
  2011年   24693篇
  2010年   14475篇
  2009年   13625篇
  2008年   23547篇
  2007年   25636篇
  2006年   25509篇
  2005年   25180篇
  2004年   24645篇
  2003年   23701篇
  2002年   22778篇
  2001年   36075篇
  2000年   36626篇
  1999年   31099篇
  1998年   9423篇
  1997年   8681篇
  1996年   8604篇
  1995年   8125篇
  1994年   7802篇
  1992年   26729篇
  1991年   26173篇
  1990年   25685篇
  1989年   24745篇
  1988年   23299篇
  1987年   22949篇
  1986年   21786篇
  1985年   21145篇
  1984年   16429篇
  1983年   14047篇
  1982年   8909篇
  1981年   8240篇
  1980年   7713篇
  1979年   16766篇
  1978年   12150篇
  1977年   10221篇
  1976年   9366篇
  1975年   10174篇
  1974年   12674篇
  1973年   12160篇
  1972年   11561篇
  1971年   10708篇
  1970年   10237篇
  1969年   9924篇
  1968年   8911篇
  1967年   8238篇
  1966年   7669篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Aim: To examine the survival benefit of liver and lung resection for colorectal metastasis and the potential prognostic factors that affect patient survival. Methods: All patients who had resection of lung or liver metastasis for colorectal metastasis in Queen Elizabeth Hospital, Hong Kong from 1995 to 2004 were retrospectively reviewed. The overall and disease‐free survival was analysed, in particularly between liver and lung metastasis. All factors that may have affected the survival were entered into Cox's proportional hazards regression model to identify significant variables associated with survival. Results: At 5 years, the overall survival of patients who had resection of lung and liver metastasis was 44% and 38%, respectively; the disease‐free survival was 26% and 24%, respectively. Overall and disease‐free survival of patients with resection of lung metastasis was comparable to those with resection of liver metastasis. The differentiations of primary tumour and time to metastasis were shown to be significant prognostic factors influencing overall survival. Those patients with systemic chemotherapy after resection of colorectal metastasis demonstrated a significantly higher probability of overall survival. Conclusion: Resection of lung and liver metastases from colorectal origin was safe and both procedures improved survival. The use of chemotherapy after resection of metastasis significantly improved the overall survival.  相似文献   
992.
Guidelines for design of clinical trials evaluating behavioral headache treatments were developed to facilitate production of quality research evaluating behavioral therapies for management of primary headache disorders. These guidelines were produced by a Workgroup of headache researchers under auspices of the American Headache Society. The guidelines are complementary to and modeled after guidelines for pharmacological trials published by the International Headache Society, but they address methodologic considerations unique to behavioral and other nonpharmacological treatments. Explicit guidelines for evaluating behavioral headache therapies are needed as the optimal methodology for behavioral (and other nonpharmacologic) trials necessarily differs from the preferred methodology for drug trials. In addition, trials comparing and integrating drug and behavioral therapies present methodological challenges not addressed by guidelines for pharmacologic research. These guidelines address patient selection, trial design for behavioral treatments and for comparisons across multiple treatment modalities (eg, behavioral vs pharmacologic), evaluation of results, and research ethics. Although developed specifically for behavioral therapies, the guidelines may apply to the design of clinical trials evaluating many forms of nonpharmacologic therapies for headache.  相似文献   
993.
994.
OBJECTIVES: The aim of this study was to investigate if radiation therapy (RT) favorably modulates wound healing at vein graft anastomoses. MATERIALS AND METHODS: Jugular vein grafts were sewn into carotid arteries in 32 rats which were randomly divided into two groups: RT (gamma source, 14 Gray, n=16) and control (C, sham irradiation, n=16). Grafts and adjacent arteries were analyzed at 2 (n=8) and 8 weeks (n=8) by histology, immunohistochemistry, and morphometry. RESULTS: Although, RT did not reduce the overall occurrence of intimal hyperplasia, the distribution differed. RT led to a reduction of intimal hyperplasia in arterial segments (median: C: 41.873 microm2; RT: 6.452 microm2, p < 0.0007). In contrast, RT augmented intimal hyperplasia in vein grafts (median: C: 30.287 microm2; RT: 90.455 microm2, p < 0.014). Vein graft diameters after RT were enlarged (median: C: 2.098 microm; RT: 3.381, p < 0.031). Over 80% of the cells were of mesenchymal origin in both groups. CONCLUSIONS: RT reduced intimal hyperplasia in arterial segments. However, RT led to graft dilatation and increased intimal hyperplasia in vein grafts. RT did not favorably modulate the vascular wound healing response in this model.  相似文献   
995.
996.
997.
Brain morphology was examined using magnetic resonance imaging in 30 first-episode patients with a schizophreniclike psychosis, 15 chronic schizophrenics, and 20 neurological controls. Statistical analyses of computer-generated measurements of regions of interest were controlled for gender, age, social class, and total brain volume. Lateral ventricular size was increased in both first-episode and chronic schizophrenic patients, with greater significance on the left than on the right side. Only the chronic patients, however, had reduced temporal lobe size, which also was greater on the left side. No major correlations of regional brain morphological measurements with cognitive functioning were found, although some measurements of verbal memory were correlated with parahippocampal size. This is a report of a preliminary study that suggests that some morphological brain changes may be present at the time of first treatment for a psychotic illness, whereas others may occur later in the course of illness. Future prospective studies may determine the clinical significance of these changes and whether they progress with the development of illness chronicity.  相似文献   
998.
Cultured brain cells from rat fetuses of ethanol-treated mothers demonstrated more than 2-fold elevations in choline acetyltransferase (ChAT) activity relative to those of control (saline-exposed) fetal brain cells. When cells from control animals were incubated in vitro for 5 days with 0.1% ethanol, ChAT activity was found to increase more than 4-fold. Brain cells from in utero ethanol-treated animals further exposed to ethanol in vitro for 5 days demonstrated significantly higher ChAT activity compared to cells exposed to ethanol only in vivo. These levels were more than 6 times greater than those of central nervous system cells never exposed to ethanol. Acetylcholinesterase (AChE) activity was significantly elevated (greater than 4-fold) in fetal brain cells when ethanol was present both in vivo and in vitro, but neither treatment alone resulted in any significant changes in AChE. These effects of ethanol on enzymes involved in acetylcholine metabolism may contribute to the different developmental neurologic abnormalities associated with fetal alcohol exposure.  相似文献   
999.
A manic depressive illness is diagnosed in many women of childbearing age; thus they are candidates for lithium therapy. Since lithium has the most clearly documented teratogenic effect of all the psychotropic drugs, special care must be taken by the physician and patient when considering its use during this period of life. A review of the literature is presented and suggested guidelines are given for the use of lithium in this at-risk population.  相似文献   
1000.
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