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   85411篇
  免费   17847篇
  国内免费   9篇
  103267篇
  2023年   460篇
  2022年   497篇
  2021年   1245篇
  2020年   2946篇
  2019年   4454篇
  2018年   5370篇
  2017年   5392篇
  2016年   6001篇
  2015年   6687篇
  2014年   6328篇
  2013年   7788篇
  2012年   6470篇
  2011年   5740篇
  2010年   5567篇
  2009年   3764篇
  2008年   4004篇
  2007年   3446篇
  2006年   3242篇
  2005年   2838篇
  2004年   2756篇
  2003年   2471篇
  2002年   2296篇
  2001年   1639篇
  2000年   1559篇
  1999年   1182篇
  1998年   450篇
  1997年   342篇
  1996年   343篇
  1995年   330篇
  1994年   254篇
  1993年   234篇
  1992年   531篇
  1991年   459篇
  1990年   404篇
  1989年   402篇
  1988年   394篇
  1987年   350篇
  1986年   335篇
  1985年   335篇
  1984年   339篇
  1983年   231篇
  1982年   213篇
  1980年   170篇
  1979年   207篇
  1978年   202篇
  1975年   194篇
  1974年   211篇
  1973年   223篇
  1972年   184篇
  1969年   170篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
91.
92.
Formation of protoplasts and their reversion were followed in 7 strains of brevibacteria. The formation of protoplasts and their reversion differed both between various species of brevibacteria and between various mutant strains of the same species.  相似文献   
93.
94.
95.
The structure and absolute configuration of desangeloylshairidin, a guaianolide isolated from Guillonea scabra, have been established by X-ray diffraction analysis. No conformational change was observed in its seven-membered ring between the crystal and deuterochloroform solution states.  相似文献   
96.
97.
In the pea test a highly positive response to the treatment with IAA reversed to a negative one or became 5 to 6 times weaker when CCC was applied together with IAA. In cultivating pea seedlings, following their decapitation, for two days in a 0.25 per cent CCC solution and then in water, growth of their cotyledonous axillaries (cotylaries) were inhibited. This inhibitive action of CCC could be made ineffective when the seedlings, following two-days’ cultivation in the CCC solution, were grown further in kinetin solutions (0.37–3 mg per 1). Cotylaries of decapitated pea seedlings, when grown in kinetin solutions were inhibited. With kinetin solutions of 6–12 mg/l a strong inhibition also occured in the growth of roots at the apical parts of which spherical swellings were developing. The CCC supplied to the roots of intact etiolated pea seedlings is translocated acropetally into the stem at a rate of about 5 cm per hour. Decapitation of the plant causes retardation of this transport, yet a coat of 0.00001–1% IAA or kinetin paste produces acceleration of the stream. Existence of an antagonism between CCC and IAA, demonstrated earlier, was found holding true also for B-9 (N, N-dimethyl-aminesuccinamic acid) and IAA, as the inhibitive action of B-9, 0.06% solution on the growth of lettuce hypocotyls was reduced to a highly significant degree when the plants were supplied with B-9 together with IAA at a concentration of 10 mg/l.  相似文献   
98.
99.
Synthesis of two hydroxy-derivatives of nalidixic acid as a result of microbial transformation was demonstrated in certain species of the genusAspergillus. Aspergillus alliaceus produced 7-hydroxy-nalidixic acid andAspergillus niger 6-hydroxy-nalidixic acid. It was demonstrated that the antibacterial activity of both hydroxy-derivatives (tested inEscherichia coli) was lower than that of the initial nalidixis acid.  相似文献   
100.
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