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   105797篇
  免费   7231篇
  国内免费   16篇
  2023年   557篇
  2022年   414篇
  2021年   997篇
  2020年   926篇
  2019年   946篇
  2018年   2561篇
  2017年   2281篇
  2016年   3192篇
  2015年   4782篇
  2014年   4847篇
  2013年   6500篇
  2012年   7955篇
  2011年   7447篇
  2010年   4742篇
  2009年   3497篇
  2008年   6119篇
  2007年   6044篇
  2006年   5520篇
  2005年   5174篇
  2004年   4846篇
  2003年   4462篇
  2002年   4103篇
  2001年   2144篇
  2000年   2111篇
  1999年   1830篇
  1998年   763篇
  1997年   590篇
  1996年   518篇
  1995年   536篇
  1994年   547篇
  1993年   409篇
  1992年   1228篇
  1991年   1148篇
  1990年   1013篇
  1989年   942篇
  1988年   887篇
  1987年   755篇
  1986年   687篇
  1985年   763篇
  1984年   660篇
  1983年   551篇
  1982年   423篇
  1981年   415篇
  1979年   568篇
  1978年   439篇
  1977年   392篇
  1976年   376篇
  1975年   426篇
  1974年   444篇
  1973年   452篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Formation and regeneration of Penicillium chrysogenum protoplasts   总被引:3,自引:0,他引:3  
  相似文献   
993.
994.
995.
Summary A direct immunohistochemical method of high specificity is presented for the demonstration of sites of cathepsin B1. Antisera were raised in rabbits against pure enzyme preparations. The specific antibodies were subsequently isolated and labelled according to methods previously published. Sections from tissues specially rich in this enzyme like liver, kidney, intestinal epithelia and the active macrophages of talcum granulomas were studied. The results suggest a localization of this enzyme mainly to lysosomal organelles and phagocytic vacuoles, which are known from chemical data to contain this enzyme. The prerequisite for a positive tissue reaction is that the enzyme must be present in a form available for antigen-antibody interaction.  相似文献   
996.
Scleronodular type of Hodgkin''s disease: experience at the Centre hospitalier universitaire de SherbrookeThe nodular sclerosis type of Hodgkin''s disease appears to be a distinct clinical entity. However, the incidence, the initial localization of the tumour and the survival of the patients are variable. The present study was carried out on a group of 17 patients, all French Canadians living in the province of Quebec, from a total of 31 with Hodgkin''s disease, an incidence of 55%. There were more males (10) than females (7). The mean age of the group was 37 years, but that of the females was lower than that of the males. The mediastinum was involved at the onset in 47% of the patients. The initial staging (according to the classification of Rye) in 76% of the patients was I or II.Four patients showed disease below the diaphragm. The lungs were infiltrated three times, the spleen six times, and the liver five times. The duration of survival of the 17 patients was twice that of the patients with the three other types of the disease.  相似文献   
997.
998.
Caudal mesoderm pattern of anomalies: from renal agenesis to sirenomelia   总被引:2,自引:0,他引:2  
B K?llén  J Winberg 《Teratology》1974,9(1):99-111
  相似文献   
999.
1. The cytosol alcohol dehydrogenase (alcohol-NAD oxidoreductase, EC 1.1.1.1) of Astasia longa was partially purified and characterized from cells grown in the presence of air+CO(2) (95:5) or of O(2)+CO(2) (95:5). 2. Under both these growth conditions, the cells contained a fraction, ADHII, which was characterized by its electrophoretic properties, by a high degree of resistance to heat inactivation, by a sharp pH optimum at 8.2 and by its kinetic properties. The estimated molecular weight of this fraction was approx. 150000, which is similar to that of yeast alcohol dehydrogenase. 3. Cells grown in air+CO(2) (95:5) contain another fraction, ADHI, which can be further separated into two subfractions by polyacrylamide-gel electrophoresis and by DEAE-cellulose chromatography. This was termed fraction ;ADHI-air'. 4. In addition to fraction ADHII, cells grown in the presence of O(2) have a twofold increase in fraction ADHI-air activity as well as two new fractions that could not be demonstrated in air-grown cells. These new fractions which we have called fraction ;ADHI-O(2)', account for about 10% of the total activity. 5. The ADHI fractions (air) and (O(2)) have similar broad pH-activity curves and similar kinetic properties, both having a lower K(m) for ethanol and NAD than fraction ADHII. However, they differ from each other with respect to their activity with various substrates. The estimated molecular weight of these two ADHI fractions and their chromatographic behaviour on hydroxyapatite and on DEAE-cellulose also distinguish them.  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