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   104330篇
  免费   572篇
  国内免费   885篇
  105787篇
  2020年   81篇
  2019年   82篇
  2018年   11994篇
  2017年   10793篇
  2016年   7695篇
  2015年   864篇
  2014年   632篇
  2013年   772篇
  2012年   4624篇
  2011年   13215篇
  2010年   12264篇
  2009年   8401篇
  2008年   10066篇
  2007年   11668篇
  2006年   606篇
  2005年   837篇
  2004年   1242篇
  2003年   1323篇
  2002年   1053篇
  2001年   521篇
  2000年   377篇
  1999年   197篇
  1998年   90篇
  1992年   247篇
  1991年   249篇
  1990年   182篇
  1989年   214篇
  1988年   244篇
  1987年   247篇
  1986年   206篇
  1985年   236篇
  1984年   197篇
  1983年   175篇
  1982年   82篇
  1980年   79篇
  1979年   229篇
  1978年   151篇
  1977年   130篇
  1976年   134篇
  1975年   166篇
  1974年   263篇
  1973年   257篇
  1972年   489篇
  1971年   516篇
  1970年   257篇
  1969年   243篇
  1968年   185篇
  1967年   185篇
  1966年   167篇
  1965年   137篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
54.
Three cases of neonatal alloimmune thrombocytopenia and one patient with post-transfusion purpura could be diagnosed only by introducing the platelet immunofluorescence test. Thrombocytopenia was caused by anti-PlA1 platelet alloantibodies detected neither in the agglutination nor by the complement fixation test.  相似文献   
55.
Systems biology is an approach to explain the behaviour of a system in relation to its individual components. Synthetic biology uses key hierarchical and modular concepts of systems biology to engineer novel biological systems. In my opinion the next step in biology is to use molecule-to-phenotype data using these approaches and integrate them in the form a periodic table. A periodic table in biology would provide chassis to classify, systematize and compare diversity of component properties vis-a-vis system behaviour. Using periodic table it could be possible to compute higher-level interactions from component properties. This paper examines the concept of building a bio-periodic table using protein fold as the fundamental unit.  相似文献   
56.
Ferruh Aşçi 《Biologia》2009,64(6):1146-1149
In this study, the structural characteristics, unique features, various organ measurements of males and females of the water mite Atractides (Atractides) turcicus sp. n. from Turkey are described. In addition, the study compares their characteristics with related species.  相似文献   
57.
58.
A general in vitro cloning system was established for four Helleborus species: H. argutifolius, H. foetidus, H. niger and H. orientalis. The plant material was introduced in vitro from axillary buds. A Murashige and Skoog (MS)—based medium (Murashige and Skoog 1962) was used supplemented with 2% (w/v) sucrose, 2-isopentenyladenine (2-iP) and 6-benzylaminopurine (BA). Multiplication rates depended on the genotype and varied from 1.3 for H. foetidus till 3.8 for H. niger. The first results showed that the rooting phase could be done ex vitro. Rooting was induced by a drench for one week in a solution of indole-3-butyric acid (IBA -3 mg l−1) and 1-naphthaleneacetic acid (NAA-1 mg l−1) at 5°C.  相似文献   
59.
60.
Acidic lipase finds its commercial values in medical applications and bioremediation of food wastes. In this work, approaches for rapid screening of lipase-producing bacteria were developed and the feasibility assessment of the screening methods was performed. From food waste samples, the proposed screening procedures allowed isolation of sixteen pure bacterial strains expressing higher lipase activity at acidic pH (pH 6.0) than at alkaline pH (pH 9.0). To enhance the accuracy of lipase activity determination under acidic conditions, a novel assay procedure was also developed by deactivating lipase activity by microwave treatment prior to back titration. This additional step could minimize interferences arising from residual lipase activity during conventional direct back-titration methods in measuring lipase activity at acidic pH. Using the four strategies proposed in this work, the best acidic-lipase-producing isolate was obtained by strategy C (SSC) and was identified as Aeromonas sp. C14, displaying an optimal lipase activity of 0.7 U/ml at an acidic pH of 6.0.  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