全文获取类型
收费全文 | 1363816篇 |
免费 | 122618篇 |
国内免费 | 1412篇 |
出版年
2021年 | 17836篇 |
2019年 | 16163篇 |
2018年 | 17815篇 |
2017年 | 16629篇 |
2016年 | 28162篇 |
2015年 | 42486篇 |
2014年 | 50431篇 |
2013年 | 76749篇 |
2012年 | 36875篇 |
2011年 | 25218篇 |
2010年 | 43552篇 |
2009年 | 44977篇 |
2008年 | 24207篇 |
2007年 | 22010篇 |
2006年 | 27333篇 |
2005年 | 28370篇 |
2004年 | 27586篇 |
2003年 | 25133篇 |
2002年 | 23323篇 |
2001年 | 35057篇 |
2000年 | 32537篇 |
1999年 | 32527篇 |
1998年 | 25705篇 |
1997年 | 25496篇 |
1996年 | 24994篇 |
1995年 | 23138篇 |
1994年 | 22980篇 |
1993年 | 22116篇 |
1992年 | 28353篇 |
1991年 | 26541篇 |
1990年 | 25438篇 |
1989年 | 26310篇 |
1988年 | 24022篇 |
1987年 | 22845篇 |
1986年 | 21679篇 |
1985年 | 23511篇 |
1984年 | 23140篇 |
1983年 | 20458篇 |
1982年 | 20789篇 |
1981年 | 19921篇 |
1980年 | 18763篇 |
1979年 | 19309篇 |
1978年 | 18127篇 |
1977年 | 17249篇 |
1976年 | 16500篇 |
1975年 | 16017篇 |
1974年 | 16312篇 |
1973年 | 16663篇 |
1972年 | 14070篇 |
1971年 | 12780篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
153.
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
154.
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
155.
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
156.
Scott M. Montgomery 《CMAJ》2010,182(11):1157-1158
157.
E. N. Medvedeva N. A. Neverova T. E. Fedorova V. A. Babkin E. S. Meteleva A. V. Dushkin T. G. Tolstikova M. V. Khvostov M. P. Dolgikh 《Russian Journal of Bioorganic Chemistry》2010,36(7):853-859
It has been found by gel-penetrating chromatography and quantitative 13C NMR spectroscopy that mechanochemical processing of arabinogalactan isolated from the wood of the Siberian larch changes
the molecular mass distribution, monosaccharide composition, and the degree of branching of its macromolecules. This is due
to the partial destruction of polysaccharide macromolecules and subsequent recombination of resulting fragments. The intensity
of these processes depends on the conditions of mechanochemical processing. Based on the data of IR and 13C NMR spectra, the conclusion has been drawn that no functionalization of arabinogalactan macromolecules occurs under these
conditions. The toxicopharmacological properties of mechanically processed arabinogalactan have been studied. Its acute toxicity
is >5000 mg/kg. 相似文献
158.
159.
160.
Maleylated-BSA suppresses IFN-gamma-mediated Ia expression in murine peritoneal macrophages 总被引:1,自引:0,他引:1
T A Hamilton P V Gainey D O Adams 《Journal of immunology (Baltimore, Md. : 1950)》1987,138(12):4063-4068
Maleylated bovine serum albumin (maleyl-BSA) and other polyanionic polymers that are recognized by cell surface receptors on macrophages have been shown to induce chemotaxis, protease secretion, and tumoricidal function in this cell type. In this paper the effect of maleyl-BSA on Ia antigen expression has been evaluated. In a fashion similar to LPS, maleyl-BSA suppressed IFN-gamma-induced expression of Ia in a time- and dose-dependent manner. Also like LPS, maleyl-BSA stimulated the production and secretion of substantial amounts of PGE2 over a 24-hr period. This did not, however, appear to be the primary mechanism by which expression of Ia was suppressed, because co-treatment of the cells with indomethacin, which totally inhibited the production of PGE2, only minimally affected the suppressive activity. Surprisingly, the suppressive activity of both maleyl-BSA and LPS could be largely abrogated by co-treatment of the cells with cyclohexamide during the time period when Ia expression was sensitive to suppression. This effect was selective in that PGE2- or dibutyryl cyclic AMP-induced suppression of Ia expression was not affected by cyclohexamide treatment. The data support the concept that there are multiple molecular mechanisms involved in the negative regulation of IFN-gamma-induced Ia expression in macrophages. Such mechanisms may include, in addition to the synthesis of PGE2 and consequent elevation in intracellular levels of cyclic AMP, one or more proteins made early after treatment with either maleyl-BSA or LPS. Thus the function of some of these early gene products may be to regulate expression of functional genes such as that encoding Ia antigen. 相似文献