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   513篇
  免费   34篇
  2020年   3篇
  2019年   3篇
  2016年   4篇
  2015年   10篇
  2014年   9篇
  2013年   14篇
  2012年   25篇
  2011年   28篇
  2010年   17篇
  2009年   12篇
  2008年   23篇
  2007年   21篇
  2006年   12篇
  2005年   15篇
  2004年   15篇
  2003年   18篇
  2002年   20篇
  2001年   19篇
  2000年   16篇
  1999年   20篇
  1998年   12篇
  1996年   6篇
  1995年   4篇
  1994年   6篇
  1993年   5篇
  1992年   12篇
  1991年   11篇
  1990年   10篇
  1989年   7篇
  1988年   4篇
  1987年   17篇
  1986年   9篇
  1985年   13篇
  1984年   8篇
  1983年   5篇
  1982年   6篇
  1981年   7篇
  1980年   3篇
  1979年   15篇
  1978年   17篇
  1977年   6篇
  1976年   3篇
  1975年   4篇
  1974年   11篇
  1973年   8篇
  1972年   7篇
  1970年   4篇
  1969年   5篇
  1967年   2篇
  1966年   4篇
排序方式: 共有547条查询结果,搜索用时 31 毫秒
1.
2.
Dehydrogenation of (2S)-[3-13C]isobutyryl-CoA was carried out in vitro using 2-methyl-branched-chain acyl-CoA dehydrogenase purified from rat liver mitochondria. The product was subsequently hydrated by the addition of bovine crotonase. The resulting 3-hydroxyisobutyric acid was predominantly enriched with 13C at the beta-hydroxy position as determined as a methyl ester using electron ionization-gas chromatography-mass spectroscopy. This finding indicates that isobutyryl-CoA is dehydrogenated stereospecifically at the (pro-2S)-methyl and alpha-methine groups to form methacrylyl-CoA, which is later hydrated with the addition of hydrogen on the same side of the molecule from which it was subtracted to produce 3-hydroxyisobutyryl-CoA.  相似文献   
3.
Ten patients with advanced progressive adenocarcinoma of the prostate were treated with a long acting analogue of gonadotrophin releasing hormone. Eight of these patients responded to treatment in terms of pain relief and clinical regression of tumour. Serum gonadotrophin and testosterone concentrations were significantly suppressed by the end of the second week of treatment, testosterone concentrations being comparable with those achieved by castration. The two patients who failed to respond had both relapsed previously when receiving conventional treatment, and neither showed any endocrine response to the analogue. Superagonists of gonadotrophin releasing hormone may be the treatment of choice in adenocarcinoma of the prostate, but further trials are required to establish long term safety and efficacy.  相似文献   
4.
5.
6.
7.
8.
Abstract

Stomach contents of the long‐finned pilot whale, Globicephala melas, are reported for the first time from New Zealand waters. Analyses based on two male and three female whales (2.5–5.3 m in length) that stranded on Farewell Spit, Golden Bay, South Island in December 2005 revealed a diet comprised exclusively of cephalopods (2-33 lower cephalopod beaks per stomach). Two genera of cephalopod from two orders; arrow squid, Nototodarus spp. (Teuthoidea: Ommastrephidae), and common octopus, Pinnoctopus cordiformis (Octopoda: Octopodidae) were represented. A further five pilot whale stomachs were examined and found to be empty.  相似文献   
9.
Bats are the natural reservoirs of a number of high-impact viral zoonoses. We present a quantitative analysis to address the hypothesis that bats are unique in their propensity to host zoonotic viruses based on a comparison with rodents, another important host order. We found that bats indeed host more zoonotic viruses per species than rodents, and we identified life-history and ecological factors that promote zoonotic viral richness. More zoonotic viruses are hosted by species whose distributions overlap with a greater number of other species in the same taxonomic order (sympatry). Specifically in bats, there was evidence for increased zoonotic viral richness in species with smaller litters (one young), greater longevity and more litters per year. Furthermore, our results point to a new hypothesis to explain in part why bats host more zoonotic viruses per species: the stronger effect of sympatry in bats and more viruses shared between bat species suggests that interspecific transmission is more prevalent among bats than among rodents. Although bats host more zoonotic viruses per species, the total number of zoonotic viruses identified in bats (61) was lower than in rodents (68), a result of there being approximately twice the number of rodent species as bat species. Therefore, rodents should still be a serious concern as reservoirs of emerging viruses. These findings shed light on disease emergence and perpetuation mechanisms and may help lead to a predictive framework for identifying future emerging infectious virus reservoirs.  相似文献   
10.
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