全文获取类型
收费全文 | 1264610篇 |
免费 | 104872篇 |
国内免费 | 1564篇 |
专业分类
1371046篇 |
出版年
2021年 | 17691篇 |
2020年 | 12597篇 |
2019年 | 16141篇 |
2018年 | 17760篇 |
2017年 | 16594篇 |
2016年 | 28074篇 |
2015年 | 42115篇 |
2014年 | 50077篇 |
2013年 | 76339篇 |
2012年 | 33409篇 |
2011年 | 21701篇 |
2010年 | 43070篇 |
2009年 | 44656篇 |
2008年 | 20804篇 |
2007年 | 18589篇 |
2006年 | 24059篇 |
2005年 | 25592篇 |
2004年 | 24506篇 |
2003年 | 22172篇 |
2002年 | 20333篇 |
2001年 | 29040篇 |
2000年 | 26314篇 |
1999年 | 27739篇 |
1998年 | 24734篇 |
1997年 | 24477篇 |
1996年 | 24099篇 |
1995年 | 22270篇 |
1994年 | 22082篇 |
1993年 | 21125篇 |
1992年 | 24056篇 |
1991年 | 22431篇 |
1990年 | 21432篇 |
1989年 | 22316篇 |
1988年 | 20447篇 |
1987年 | 19376篇 |
1986年 | 18338篇 |
1985年 | 20514篇 |
1984年 | 20803篇 |
1983年 | 18449篇 |
1982年 | 19398篇 |
1981年 | 18867篇 |
1980年 | 17628篇 |
1979年 | 16637篇 |
1978年 | 16229篇 |
1977年 | 15719篇 |
1976年 | 15097篇 |
1975年 | 14439篇 |
1974年 | 14716篇 |
1973年 | 15198篇 |
1972年 | 12638篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
The marine bacteriumVibrio anguillarum causes disease in fish worldwide and is particularly devastating in aquaculture. Little is known about the ecology ofV. anguillarum in the environment and how this may relate to the pathogenicity of this organism. Combining membrane filtration and a species-specific DNA probe, culturableV. anguillarum cells were detected in water from three habitats and in chinook salmon (Onchorynchus tshawytscha) tissue samples. Results show that different marine habitats have a marked effect on cell numbers and that water temperature may play a role in the culturability and distribution ofV. anguillarum. Vibrio anguillarum was detected from the gills of salmon within 24 h of transfer of fingerlings from freshwater to seawater, with cell numbers reaching a concentration of 1.9 × 102 cells g–1 tissue 28 days post transfer.Vibrio anguillarum cell numbers were low in the colon throughout the study, andV. anguillarum was not detected in healthy kidney samples. The methodology reported in this paper allows the accurate quantification of culturableV. anguillarum cells and has allowed a preliminary study of the ecology of this species. 相似文献
103.
The fish pathogenVibrio anguillarum causes significant economic losses in commercially cultured fish species worldwide. At present, identification ofV. anguillarum requires conventional isolation and culturing techniques. Using differential hybridization, a 310 base pairV. anguillarum-specific DNA fragment was isolated for use as a probe. In specificity studies against 19 different bacterial species, including twoVibrio sp. and fish pathogens, and 223 marine bacterial isolates, the probe hybridized exclusively toV. anguillarum strains. The probe also strongly hybridizes to 7 of 9 serotypes tested, with serotype 09 giving a weak probe reaction and serotype O7 negative. The probe allows rapid and accurate detection of both pathogenic and environmental strains ofV. anguillarum. 相似文献
104.
S-adenosyl-L-homocysteine (S-AH), a potent inhibitor of biological transmethylation, decreased the response of rat retina adenylate cyclase to dopamine and to 2-amino-6, 7-dihydroxytetrahydronaphtalene (ADTN). This effect appeared for 10?7M of S-adenosyl-L-homocysteine and was linear for concentration ranging to 10?4M. S-adenosyl-L-homocysteine did not decrease the cyclic AMP accumulation with sodium fluoride, a non specific adenylate cyclase activator. On the other hand, the incorporation of methyl group was reduced in rat retina homogenates by S-adenosyl-L-homocysteine. These findings suggest that the activity of the dopamine dependent adenylate cyclase is linked to a methylation process. 相似文献
105.
106.
107.
V K Khugaeva E D Klimenko P N Aleksandrov G F Leskova M I Reutov 《Biulleten' eksperimental'no? biologii i meditsiny》1985,100(7):15-19
Experiments were made on rabbit fed an atherogenic diet (0.5 g/kg cholesterol) singly for 15 and 24 h and repeatedly for 3, 9 and 30 days. At early stages of lipid metabolism distress the interrelationship was established between blood rheological disorders and microcirculatory abnormalities. The dependence of the initial reaction of some rheological characteristics on their initial level was marked. 相似文献
108.
Vernon Shattuck Frank R. Katterman 《Biochemical and biophysical research communications》1982,109(3):1017-1025
When cotyledonary tissue of cotton are treated with the mutagen ethyl methanesulfonate and then germinated, an enhanced, unscheduled DNA synthesis response is observed, along with a concomitant increase in the thymidine triphosphate precursor pool size. The implications of these results are discussed in this paper. 相似文献
109.
110.