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   295097篇
  免费   34815篇
  国内免费   151篇
  2018年   2413篇
  2016年   3116篇
  2015年   4073篇
  2014年   4982篇
  2013年   6817篇
  2012年   7796篇
  2011年   7981篇
  2010年   5273篇
  2009年   5094篇
  2008年   7234篇
  2007年   7423篇
  2006年   7292篇
  2005年   7009篇
  2004年   6881篇
  2003年   6679篇
  2002年   6534篇
  2001年   17321篇
  2000年   17504篇
  1999年   13351篇
  1998年   3908篇
  1997年   4160篇
  1996年   3880篇
  1995年   3515篇
  1994年   3491篇
  1993年   3560篇
  1992年   10432篇
  1991年   10366篇
  1990年   9851篇
  1989年   9684篇
  1988年   9030篇
  1987年   8394篇
  1986年   7589篇
  1985年   7445篇
  1984年   5862篇
  1983年   5104篇
  1982年   3639篇
  1981年   3201篇
  1980年   3048篇
  1979年   5374篇
  1978年   4135篇
  1977年   3765篇
  1976年   3328篇
  1975年   3803篇
  1974年   3971篇
  1973年   3912篇
  1972年   3452篇
  1971年   3199篇
  1970年   2835篇
  1969年   2764篇
  1968年   2433篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
On 11 May 1985 the main stand of Bradford City Football Club caught fire. Within four minutes the stand was alight from end to end. Fifty three people were burnt to death and about 250 injured; 83 required admission to hospital, and 55 of these were treated by primary excision of their burns and skin grafting. In such disasters the help of staff from other hospitals and areas is essential. Patients should be assessed to see whether they have burns that will ultimately be fatal; if they have they should not be sent to regional burns units, where they would take up beds that could be used for patients with treatable burns. All districts should ensure that their plans for accidents in which burns injuries predominate are adequate.  相似文献   
982.
Two hybridomas secreting mouse cytotoxic monoclonal antibodies to in vivo and in vitro activated human T-lymphocyte and neutrophil surface membrane antigenic determinants have been produced. One of these monoclonal antibodies (Ta/H-2) appeared to be also specifically reactive to blast cells in the majority of non-T-non-B and T acute lymphoblastic leukemia patients.  相似文献   
983.
Ca2+ uptake and membrane potential in sarcoplasmic reticulum vesicles   总被引:2,自引:0,他引:2  
The rate of calcium uptake by sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle was stimulated by inside-negative membrane potential generated by K+ gradients in the presence of valinomycin. The increase in the calcium transport rate was accompanied by a proportional increase in the rate of calcium-dependent ATP hydrolysis, without significant change in the steady state level of the phosphorylated enzyme intermediate. Changes in the sarcoplasmic reticulum membrane potential during calcium transport were monitored with the optical probe, 3,3'-diethylthiadicarbocyanine. The decrease in the absorbance of 3,3'-diethylthiadicarbocyanine at 660 nm following generation of inside-negative membrane potential was reversed during ATP-induced calcium uptake. These observations support an electrogenic mechanism for the transport of calcium by the sarcoplasmic reticulum.  相似文献   
984.
985.
Flows of biomass and respiratory carbon were studied in a series of propylene-oxide sterilized soil microcosms. One-half of the microcosms received three pulsed additions of 200 ppm glucose-carbon to mimic rhizosphere carbon inputs. Biotic variables were: bacteria (Pseudomonas) alone, or amoebae (Acanthamoeba) and nematodes (Mesodiplogaster) singly, or both combined in the presence of bacteria.Over the 24-day experiment, respiration was significantly higher in the microcosms containing the bacterial grazers. Biomass accumulation by amoebae was significantly higher than that by nematodes. The nematodes respired up to 30-fold more CO2 per unit biomass than did amoebae. Similar amounts of carbon flowed into both respiratory and biomass carbon in microcosms with fauna, compared with the bacteria-alone microcosms. However, partitioning of available carbon by the microfauna varied considerably, with little biomass production and relatively more CO2-C produced in the nematode-containing microcosms. The amoebae, in contrast, allocated more carbon to tissue production (about 40% assimilation efficiency) and correspondingly less to CO2.  相似文献   
986.
987.
988.
989.
990.
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