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   4618篇
  免费   308篇
  2021年   46篇
  2020年   23篇
  2019年   35篇
  2018年   49篇
  2017年   40篇
  2016年   62篇
  2015年   100篇
  2014年   134篇
  2013年   238篇
  2012年   208篇
  2011年   210篇
  2010年   131篇
  2009年   125篇
  2008年   181篇
  2007年   216篇
  2006年   199篇
  2005年   197篇
  2004年   208篇
  2003年   210篇
  2002年   208篇
  2001年   189篇
  2000年   205篇
  1999年   158篇
  1998年   74篇
  1997年   70篇
  1996年   57篇
  1995年   44篇
  1994年   38篇
  1993年   35篇
  1992年   84篇
  1991年   108篇
  1990年   96篇
  1989年   97篇
  1988年   83篇
  1987年   82篇
  1986年   77篇
  1985年   79篇
  1984年   63篇
  1983年   63篇
  1982年   34篇
  1981年   23篇
  1980年   18篇
  1979年   41篇
  1978年   26篇
  1977年   30篇
  1976年   21篇
  1975年   21篇
  1974年   24篇
  1973年   30篇
  1970年   18篇
排序方式: 共有4926条查询结果,搜索用时 78 毫秒
991.
992.
Linalool is an important compound that contributes to the floral aroma in wines. This study showed the effect of light exposure on linalool accumulation in berries. The grape bunches were covered with films that block the full light spectrum (Shade) and the UV spectrum (UV-block), and a transparent film (Control). The linalool content was significantly higher in juice from Control-covered berries than in juice from Shade- and UV-block-covered berries, and the expression levels of the representative genes in linalool biosynthesis in Shade- and UV-block-covered berries were markedly lower than in Control-covered berries. These findings suggest that exposing berries to light is essential for linalool biosynthesis. To reflect sunlight onto grape clusters, reflective sheets were placed on the ground of a vineyard. The linalool content in berries exposed to sunlight reflected from the reflective sheets was higher than those in the control.  相似文献   
993.
994.
Genetic variation plays a pivotal role in species viability and the maintenance of population genetic variation is a main focus of conservation biology. Threatened species often show reduced genetic variation compared to non-threatened species, and this is considered indicative of lowered evolutionary potential, compromised reproductive fitness, and elevated extinction risk. The southern purple-spotted gudgeon, Mogurnda adspersa, is a small freshwater fish with poor dispersal potential that was once common throughout the Murray–Darling Basin (MDB) and along the central east coast of Australia. Its numbers and distribution have shrunk dramatically in the MDB due to flow alteration, degradation of habitat, decreasing water quality, and introduction of alien species. We used microsatellite DNA markers to assess population structure and genetic variation at both large (i.e. across basin) and fine (i.e. within river catchments) spatial scales using a substantial sampling effort across the species range (n = 579 individuals; 35 localities). The results consistently indicated very low levels of genetic variation throughout, including along the east coast where the species is relatively common. At the broader scale, three highly differentiated groups of populations were found, concordant with previously reported genealogical distinctiveness. Hence we propose each group as a distinct Evolutionarily Significant Unit. We also inferred a minimum of 12 management units in M. adspersa, with no appreciable gene flow between them. Our study discloses findings relevant for both long- and short-term management, as it informs on the geographic context in which conservation priorities should be defined and specifies biological units for population monitoring and translocations.  相似文献   
995.
996.
997.
998.
999.
1000.
Obese diabetes was induced by monosodium aspartate (MSA) administration in KK male mice and the diabetic KK mice were divided into two groups, younger (12-week-old) and older (35-week-old). The diabetic KK mice were castrated and administered with androgen and effect of androgen on glycosuria appearance was investigated. Androgen dependent tear proteins (Mtp-M) were detected by the method of polyacrylamide gel electrophoresis. Blood androgen level was estimated by observation of change of the pattern of Mtp-M. In the younger mice group, glycosuria disappeared temporarily after castration and then appeared naturally again. The Mtp-M declined with castration, but did not disappear in this experimental period. In the older mice group, glycosuria and Mtp-M disappeared completely and blood glucose level decreased considerably after castration. However, in the castrated older mice, the glycosuria and the Mtp-M appeared again after the administration of dehydroepiandrosterone (DHEA), and the increasing of blood glucose level was observed. These results strongly suggested that androgen had an important role in the onset of diabetes in the KK mice treated with MSA.  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