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   2230333篇
  免费   158150篇
  国内免费   5096篇
耳鼻咽喉   32014篇
儿科学   71396篇
妇产科学   63921篇
基础医学   317071篇
口腔科学   66350篇
临床医学   195019篇
内科学   430519篇
皮肤病学   51550篇
神经病学   178933篇
特种医学   87861篇
外国民族医学   720篇
外科学   339962篇
综合类   51112篇
现状与发展   6篇
一般理论   822篇
预防医学   163081篇
眼科学   52400篇
药学   164904篇
  6篇
中国医学   4683篇
肿瘤学   121249篇
  2018年   22402篇
  2017年   17893篇
  2016年   20378篇
  2015年   22307篇
  2014年   30418篇
  2013年   47192篇
  2012年   61735篇
  2011年   66032篇
  2010年   39164篇
  2009年   36600篇
  2008年   62771篇
  2007年   67592篇
  2006年   68214篇
  2005年   65907篇
  2004年   64083篇
  2003年   62177篇
  2002年   60620篇
  2001年   101875篇
  2000年   105111篇
  1999年   88015篇
  1998年   24424篇
  1997年   22090篇
  1996年   21517篇
  1995年   20428篇
  1994年   19136篇
  1992年   68517篇
  1991年   66538篇
  1990年   65566篇
  1989年   63818篇
  1988年   58831篇
  1987年   58462篇
  1986年   55410篇
  1985年   53140篇
  1984年   39884篇
  1983年   33783篇
  1982年   20420篇
  1981年   18574篇
  1979年   37755篇
  1978年   27153篇
  1977年   23469篇
  1976年   21546篇
  1975年   23735篇
  1974年   28417篇
  1973年   27453篇
  1972年   25910篇
  1971年   24218篇
  1970年   22856篇
  1969年   21764篇
  1968年   20263篇
  1967年   18228篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Summary This study was undertaken to elucidate, using the Golgi method, the neuropathological change in the brain of the macular mutant mouse, whose hemizygote (Ml/y) is considered to be a model of Menkes kinky hair disease (MKHD). The hemizygote mice gradually lost weight after 10 days of age and died with emaciation and seizure around day 15. The normal littermate (+/y) was well developed. In the cerebrum, the arborization of pyramidal neurons in the layer V of the Ml/y was the same as that in the +/y on day 10. However, development of arborization in the Ml/y was delayed in comparison with that in the +/y on days 12 and 14. Purkinje cells with several somal sprouts were observed in the cerebellum in both the Ml/y and +/y on day 7. The somal sprouts in the +/y had regressed gradually by day 12, while they were still in the anterior and middle lobes of the Ml/y on day 14. Additionally, the trunks of Ml/y stem dendrites became thicker and a cactus formation was recognized on the branching portion of the dendrites on day 14. Arborization of these abnormal Purkinje cells was distinctly poor compared with that in the +/y. These results suggest that the growth of the neurons is delayed in the Ml/y and simultaneously their cytoskeletal developments are disturbed, especially in the Purkinje cells. There is a close similarity in many respects to the neuropathological change in MKHD.  相似文献   
993.
Major depression with psychotic features, dementia, and focal neurologic abnormalities appeared in a Haitian man without AIDS or other syndromes of immune compromise. Neurologic evaluation, including brain biopsy, was nondiagnostic, but CSF culture revealed human immunodeficiency virus (HIV).  相似文献   
994.
In order to examine the cholecystohepatic circulation of trichloroethylene (TRI) and its metabolites, we injected the gallbladder with TRI and its metabolites, i.e. chloral hydrate (CH), free-trichloroethanol (F-TCE), trichloroacetic acid (TCA) and conjugated-trichloroethanol (Conj-TCE), using anesthetized dogs. The absorption rates of water from the gallbladder were 25-30% 2 h after administration for all substances. The absorption rates of substances were 65-70% in the CH, F-TCE and TRI groups, and 40-50% in the Conj-TCE and TCA groups 2 h after the administration. Conj-TCE in the blood absorbed from the gallbladder has a tendency to be directly transported to the venous system rather than to be taken into hepatocytes in the liver. All of the administered substances, in particular, F-TCE might be metabolized to other substances in the gallbladder.  相似文献   
995.
996.
Assessing the role of family planning in reducing maternal mortality   总被引:1,自引:0,他引:1  
It is widely believed that family planning has important benefits for both maternal and child health. Despite this, little work has been done to quantify the potential effect of family planning in reducing maternal mortality. This paper assesses the impact of family planning in averting maternal deaths, and discusses the overall ability of risk strategies to address the bulk of maternal mortality. The practical difficulties of providing effective contraception to populations with high maternal mortality are addressed, and the need for maternal health care services as an adjunct to useful family planning programs is emphasized. Although family planning cannot by itself cause a substantial reduction in risk of pregnancy, the combined strategies of general fertility reduction, abortion services, and family planning for high-risk groups might effectively address about half of all maternal mortality in the developing world. Pregnancy and delivery care have the potential for saving large numbers of lives with appropriate interventions. It is concluded that reproductive risks can be reduced only by preventing unwanted pregnancies and protecting maternal health during wanted ones.  相似文献   
997.
Plasma pyridoxal-5'-phosphate and pyridoxal levels increased significantly (p less than 0.05) when single, oral bolus doses of pyridoxine were increased from 10 to 25 and from 25 to 50 mg in nine female volunteers. However, when the dose was increased to 100 mg, plasma pyridoxal-5'-phosphate levels did not differ significantly from those recorded after the 50 mg dose. Within 3 h plasma pyridoxal levels rose with a factor of 3.85 compared with the 50 mg dose but high pyridoxal levels were eliminated from the circulation. Renal clearance of pyridoxal remained a constant, low percentage (less than 2.0%) of each pyridoxine supplement in spite of the observed very high circulating pyridoxal levels. Pyridoxine supplementation is discussed in relation to circulating pyridoxal-5'-phosphate and pyridoxal availability for cellular metabolism.  相似文献   
998.
About 85% of the population of two Somali communities harboured soil-transmitted intestinal nematodes and/or protozoa. The commonest parasite (75% in the Lafoole institution and 59% in the Afgoye institution) was Trichuris trichiura. Mixed infections were common. The source of infection is contaminated fields around dwelling quarters, because of indiscriminate defaecation. One of the factors responsible for the higher incidence of hookworm in Lafoole (45%) compared with Afgoye (1.5%) may be the different soil character of the surrounding fields.  相似文献   
999.
1000.
Delta hepatitis virus infection in China   总被引:1,自引:0,他引:1  
To assess the prevalence, epidemiological features and prognostic implications of hepatitis D (Delta) in Sichuan Province, The People's Republic of China, 649 sera (515 from HBsAg positive patients and 134 from HBsAg negative subjects) were tested by radioimmunoassay (RIA) for antibody to the hepatitis D virus (anti-HD). Forty-seven sera (7.2%) showed some degree of reactivity. Serial dilutions of these sera indicated that prozoning was not responsible for the equivocal results. Thirty-four of the 47 sera were submitted under code to a second laboratory for independent analysis. According to those results anti-HD antibodies were detected in four of these sera. The overall prevalence of anti-HD in the HBsAg positive patients therefore was 0.8% (4/515). On the basis of clinical, biochemical and histological data 427 HBsAg positive sera were further divided into acute Type B hepatitis, chronic Type B hepatitis, healthy carrier state and hepatocellular carcinoma (HCC) subgroups. Two of 65 (3.1%) anti-HD positive sera belonged to the acute Type B hepatitis group; one of 104 (0.9%), the chronic Type B hepatitis group and one of 246 (0.4%), the healthy carrier group. No antibody was detected in sera from 12 HBsAg positive HCC patients. All HBsAg negative patients were negative for anti-HD antibody. The results of this study indicate that despite a high prevalence of hepatitis B virus infection, positive serology for delta virus is uncommon in Sichuan Province, The People's Republic of China.  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