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   1274823篇
  免费   109503篇
  国内免费   1481篇
  1385807篇
  2021年   17727篇
  2020年   12572篇
  2019年   16126篇
  2018年   17236篇
  2017年   16005篇
  2016年   27717篇
  2015年   42143篇
  2014年   50162篇
  2013年   76362篇
  2012年   34000篇
  2011年   21828篇
  2010年   42391篇
  2009年   44165篇
  2008年   21376篇
  2007年   18870篇
  2006年   24808篇
  2005年   25835篇
  2004年   25159篇
  2003年   22837篇
  2002年   20993篇
  2001年   29021篇
  2000年   26096篇
  1999年   27361篇
  1998年   24841篇
  1997年   24686篇
  1996年   24322篇
  1995年   22339篇
  1994年   22285篇
  1993年   21283篇
  1992年   24226篇
  1991年   22818篇
  1990年   21397篇
  1989年   22546篇
  1988年   20541篇
  1987年   19548篇
  1986年   18576篇
  1985年   20617篇
  1984年   20893篇
  1983年   18510篇
  1982年   19639篇
  1981年   19062篇
  1980年   17749篇
  1979年   17037篇
  1978年   16403篇
  1977年   16061篇
  1976年   15275篇
  1975年   14581篇
  1974年   15024篇
  1973年   15382篇
  1972年   12887篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
A comparison has been performed of catalytic properties of unicellular microorganism amine oxidases (AO) from two new enzyme sources, the bacteriumMethanosarcina barkeri and the infusoriaTetrahymena pyriformis. It was shown that the both studied AO deaminate tyramine, serotonin, and benzylamine, but do not deaminate histamine. The AO fromMethanosarcina barkeri catalyzes deamination of all three substrates at an identical rate, while the rate of tyramine deamination under effect of AO fromTetrahymena pyriformis is one order higher than the rate of serotonin deamination, and about two orders higher than the rate of benzylamine deamination. Based on the data of the substrate-inhibitor analysis, a suggestion was made about the existence of one center for the substrate binding in the AO of the studied bacterium, while several centers in the AO of the studied infusoria.  相似文献   
972.
Oxygen concentrations stimulated growth (maximum number of cells) and protease secretion by Tetrahymena thermophila. Agitation and aeration conditions for growth and protease secretion were optimised by a central composite design. The best optimised combination was a stirrer speed of 338 rpm and an aeration of 1 vvm. Journal of Industrial Microbiology & Biotechnology (2000) 25, 58–61. Received 24 September 1999/ Accepted in revised form 06 March 2000  相似文献   
973.
The evaluation of growth by dry weight determination of fungus mycelium for agar plates was examined. The data obtained were statistically analyzed. This method was shown to be sufficiently accurate to be used as an investigative tool.  相似文献   
974.
The results of this study indicate that urbanization has the effect of significantly altering the Guajiro's sense of ideal and feared identity. It was hypothesized that an attempt would be made to minimize dissonance between the ideal and the real or "true" self which the individual privately acknowledges. However, there is found to be considerable dissonance between ideal and real identities, with the latter actually including many components of feared identity. Defective socialization in the city is suggested as a possible reason for failure to achieve ideal standards.  相似文献   
975.
976.
977.
Feasible mechanisms for algal digestion in the king angelfish   总被引:1,自引:0,他引:1  
To determine the ability of the king angelfish Holacanthus passer to digest algae, three algal species were immersed in acidic conditions similar to that found in the stomach of fish. Only one of them was not susceptible to acidic lysis; two were affected after 40 and 60 min at pH 2·0. King angelfish have an expanded region of the intestine called here the hindgut chamber (HC) containing populations of micro-organisms. Some of these micro-organisms have the capacity to grow in cellulose, agar, and alginic acid; the main components of algal cell walls. Micro-organisms grew in carboxymethylcellulose cultures under aerobic and micro-aerobic conditions. The HC is highly vascularized, which could increase absorptive efficiency of material digested in it.  相似文献   
978.
Editor's preface     
J. Hoey 《CMAJ》1998,158(1):5
  相似文献   
979.
Turning, pectoral fin and caudal fin rates and time spent on the nest of male rock bass Ambloplites rupestris , engaged in parental care, were not affected after the attachment of external radio transmitters. Reproductive success was similar between treatment and control fish. Micro external radio transmitters can be used on small fishes for studying parental care duration and post-care movement without altering their behaviour.  相似文献   
980.
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