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   46077篇
  免费   4905篇
  国内免费   107篇
耳鼻咽喉   438篇
儿科学   1224篇
妇产科学   1095篇
基础医学   6922篇
口腔科学   1064篇
临床医学   5676篇
内科学   8458篇
皮肤病学   544篇
神经病学   4456篇
特种医学   1830篇
外国民族医学   57篇
外科学   5935篇
综合类   994篇
一般理论   43篇
预防医学   5150篇
眼科学   1130篇
药学   3450篇
中国医学   27篇
肿瘤学   2596篇
  2021年   655篇
  2020年   414篇
  2019年   645篇
  2018年   717篇
  2017年   552篇
  2016年   605篇
  2015年   648篇
  2014年   964篇
  2013年   1521篇
  2012年   2033篇
  2011年   2073篇
  2010年   1243篇
  2009年   1082篇
  2008年   1972篇
  2007年   1965篇
  2006年   2000篇
  2005年   1913篇
  2004年   1951篇
  2003年   1718篇
  2002年   1692篇
  2001年   1484篇
  2000年   1609篇
  1999年   1366篇
  1998年   592篇
  1997年   516篇
  1996年   479篇
  1995年   481篇
  1994年   443篇
  1993年   406篇
  1992年   1075篇
  1991年   1114篇
  1990年   1024篇
  1989年   1010篇
  1988年   1012篇
  1987年   878篇
  1986年   870篇
  1985年   847篇
  1984年   705篇
  1983年   582篇
  1982年   387篇
  1981年   363篇
  1980年   348篇
  1979年   662篇
  1978年   516篇
  1977年   442篇
  1976年   422篇
  1975年   385篇
  1974年   438篇
  1973年   435篇
  1972年   377篇
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
21.
22.
Vaccine cuisine.   总被引:1,自引:0,他引:1       下载免费PDF全文
  相似文献   
23.
Although extracellular matrix (ECM) glycoproteins play important roles in neural development, their levels are generally believed to decrease in the adult brain. Immunohistochemical analysis indicates that the anti-adhesive ECM glycoprotein SPARC/osteonectin, which contains a follistatin ‘module’, is expressed in the adult rabbit nervous system. In the cerebellum, SPARC is present in Bergmann glia, with a strong signal along their radial fibres. SPARC, while enriched in membrane fractions, is not a transmembrane protein. In the hippocampus, colocalization of SPARC is observed in cells which express the astrocytic marker GFAP. The expression of SPARC by a subset of astrocytes, particularly in synaptic enriched areas, suggests a continuing role for the ECM in the adult brain.  相似文献   
24.
Segregation analysis of leprosy in families of northern Thailand   总被引:4,自引:0,他引:4  
Sixty-three families with multiple instances of leprosy were identified through a major leprosy treatment center in northern Thailand. Complex segregation analyses for single major genes or polygenic inheritance were performed using the maximum-likelihood routine POINTER to determine the most likely etiologic model of genetic susceptibility. Liability differences between men and women were considered in these models. When individuals were considered to be affected because they had any form of leprosy, a generalized major gene model with nearly dominant parameters on the liability scale, but additive penetrances, was found to be the most likely. When only those individuals who had tuberculoid forms of leprosy were considered to be affected, a recessive model was found to be the most likely; however, the discrimination between various models was poor. Further analyses are necessary to delineate genetic mechanisms to explain these apparently divergent results. In particular, methods of testing two locus models should be considered.  相似文献   
25.
Patients on long-term haemodialysis suffer from dialysis arthropathy due to the deposition of dialysis amyloid. We investigated the use of 99Tc-labelled methylene diphosphonate bone scans in 17 patients as a possible in vivo diagnostic technique. In most clinically affected joints, with the exception of shoulders and hands, there was increased radioisotope uptake consistent with uptake by periarticular bone. In addition, we describe intense soft-tissue uptake around some clinically affected large joints. In contrast, control groups of patients on haemodialysis without arthropathy and patients without renal failure did not have increased uptake. A semi-quantitative scale of uptake was devised, and the following correlations were significant: pain perception and isotope uptake score in the ankles and feet, and the number of radiological lesions and isotope uptake scores in the wrists and knees. The following sites where the radioisotope might bind in the affected joints are proposed: amyloid deposits, areas of soft-tissue calcification, or areas of increased bone turnover. It is concluded that whereas the scanning technique cannot make a definite diagnosis of amyloid and, therefore, cannot be expected to supersede histological diagnosis, it is a useful adjuvant investigation, of particular importance in those patients unable or unwilling to undergo biopsy.  相似文献   
26.
Aim : The study was designed to determine the effect of computerized nutrition information on consumer food choice in two workplace restaurants, one in which customers had to pay for their lunch and the other providing a free lunch. Methods : Customers entering the restaurants were asked to make selections from the menu on a computer screen. The energy, saturated fatty acids, non-milk extrinsic sugars and non-starch polysaccharide content of the meal selected was displayed graphically in proportion to the dietary reference values. They were given the opportunity to change their selected meal and the composition of all meals was recorded. Results : The nutritional composition of the first meal provoked 16% of customers to make a second selection. The proportion of energy in the first selection had been 31% higher for saturated fatty acids and 23% higher for non-milk extrinsic sugars than the first selection made by people who were satisfied with their first choice. In their second attempt they succeeded in reducing both nutrients to levels similar to those present in the meals selected by people who had been satisfied with their first selection. Customers>> selections for non-starch polysaccharide and energy did not differ between the groups. The main changes made by customers to achieve improved second choices were to omit dishes (44%), add dishes (19%), make changes within a menu category (46%), and make changes from one menu category to another (26%). Conclusion : It was concluded that provision of graphical nutrition information on a computer screen could be used by a subset of the users of both restaurants to enable them to improve their menu selections to a similar composition to that selected by the other people who used the computer system.  相似文献   
27.
Netlines     
  相似文献   
28.
29.
The effects of two promoters of hepatocarcinogenesis--phenobarbital and butylated hydroxytoluene (BHT)--on five hepatic biochemical parameters were examined in adult female rats. Phenobarbital given orally in two doses each of 110 mg/kg 21 and 4 hr before the rats were killed caused large increases in hepatic ornithine decarboxylase (ODC) activity and cytochrome P-450 content. Extending the number of phenobarbital treatments to five increased the hepatic enzyme induction and also caused a minor decrease in hepatic glutathione and a small increase in serum alanine aminotransferase activity. Two oral doses of 700 mg BHT/kg (20% of the LD50) caused hepatic DNA damage and induction of both ODC activity and cytochrome P-450 content. When the dose of BHT was reduced from 700 to 140 mg/kg no significant effects on the biochemical parameters were found. Both promoters of hepatocarcinogenesis were identified by their induction of ODC, a marker for promotional potential, but only BHT showed a potential for carcinogenic initiation. The biochemical parameters examined, particularly the alkaline elution technique for DNA damage, ornithine decarboxylase activity and serum alanine aminotransferase, may constitute a useful assay system for examining a compound's potential for carcinogenic initiation, carcinogenic promotion and cellular toxicity.  相似文献   
30.
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