全文获取类型
收费全文 | 1453篇 |
免费 | 83篇 |
专业分类
1536篇 |
出版年
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 43篇 |
2020年 | 22篇 |
2019年 | 34篇 |
2018年 | 49篇 |
2017年 | 28篇 |
2016年 | 42篇 |
2015年 | 55篇 |
2014年 | 85篇 |
2013年 | 91篇 |
2012年 | 78篇 |
2011年 | 89篇 |
2010年 | 64篇 |
2009年 | 52篇 |
2008年 | 63篇 |
2007年 | 80篇 |
2006年 | 49篇 |
2005年 | 66篇 |
2004年 | 39篇 |
2003年 | 41篇 |
2002年 | 38篇 |
2001年 | 19篇 |
2000年 | 26篇 |
1999年 | 14篇 |
1997年 | 7篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1992年 | 11篇 |
1991年 | 25篇 |
1990年 | 16篇 |
1989年 | 23篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 21篇 |
1983年 | 10篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 22篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1975年 | 13篇 |
1974年 | 6篇 |
1973年 | 10篇 |
1972年 | 9篇 |
1971年 | 7篇 |
1969年 | 5篇 |
排序方式: 共有1536条查询结果,搜索用时 15 毫秒
21.
Phosphatidylethanolamine distribution and fluidity in outer and inner membranes of the gram-negative bacterium Erwinia carotovora. 总被引:1,自引:1,他引:0 下载免费PDF全文
1. The distribution of phosphatidylethanolamine, the major lipid of Erwinia carotovora, was investigated in intact bacteria, spheroplasts and outer- and inner-membrane preparations, with the amino-group reagent 2,4,6-trinitrobenzenesulphonic acid. Only 4% was found on the external surface of the outer membrane with 30% on the internal surface, whereas the inner membrane had 27 and 38% on its external and internal surfaces respectively. Some comparative studies were made with three other bacteria. 2. The fluidity of the membranes of E. carotovora was studied by using the fluorescent probe 1,6-diphenylhexa-1,3,5-triene. Results were consistent with the hydrocarbon region of the outer membrane bilayer being less fluid than that of the inner one. 3. On the basis of these and other results a model for the outer- and inner-membrane structures of E. carotovora is proposed. 相似文献
22.
23.
Shukla RN 《Biochemistry and experimental biology》1977,13(4):411-416
Proteins and lipids in the haemolymph in both the sexes of the Danais chrysippus has been observed during the first gonotropic cycle. The concentration fluctuations in these haemolymph metabolites are correlated with the physiological state of the insect. The total protein and lipid concentration in the haemolymph of unmated females have been found to be low than the concentration found for the normal females although it followed the same type of oscillations in the concentration as have been observed for normal females. 相似文献
24.
Govind J. Kapadia Y.N. Shukla S.P. Basak Henry M. Fales E.A. Sokoloski 《Phytochemistry》1978,17(8):1444-1445
Melovinone, a new alkaloid isolated from the roots of Melochia tomentosa has been characterized as 3,7,8-trimethoxy-2-methyl-5(5′-phenylpentyl)-4-quinolinone. 相似文献
25.
We have investigated the characteristics of platelet-activating factor (PAF)-stimulated protein tyrosine phosphorylation in rabbit platelets and its relationship to pp60c-src. 32P-Labeled platelets were challenged with PAF (10(-7) M) for 15 s, the reaction was killed by lysis at 4 degrees C, and samples were loaded onto a phosphotyrosine monoclonal antibody (Tyr(P)-mAb)-agarose column. The column was eluted with 10 mM phenyl phosphate, and the fractions were collected. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, followed by autoradiography of the column fractions, showed that PAF increased the radioactivity of about a dozen protein bands with predominant ones of approximate molecular masses of 50, 60, 71, 82, and 300 kDa. When Tyr(P)-mAb-agarose column fractions were subjected to immunoblotting with pp60v-src mAb, it was observed that PAF treatment increased the reactivity of 50- and 60-kDa protein species. Immunoprecipitation with pp60v-src mAb further confirmed that PAF treatment increased phosphorylation of the 60- and 50-kDa proteins. Polyclonal antibody to G-protein (alpha-subunit) did not exhibit any reactivity to the column fractions and thus ruled out this protein as substrate for the tyrosine kinase. We next attempted to localize the pp60c-src. Platelet membrane particulate and cytosol fractions were separated from control and PAF-treated platelets, and it was observed that the immunoreactivity to pp60v-src mAb dramatically increased in the particulate membrane fraction from PAF-treated platelets. A concomitant decrease in the immunoreactivity in the cytosol fraction of PAF-treated platelets was also noted. It is concluded that PAF stimulates phosphorylation of pp60c-src tyrosine kinase and causes its rapid translocation from cytosol to membranes in rabbit platelets. 相似文献
26.
The multiplication of A. culbertsoni in the peptone medium was not inhibited by 10-20 mM concentration of alpha-difluoromethyl ornithine (DMFO) while a partial and transient inhibition of cell multiplication was observed by 10-20 mM DFMO in proteose peptone, yeast extract, glucose (PYG) medium. Ornithine decarboxylase (ODC) activity in the cells and cell free extracts was strongly inhibited by DFMO, excluding enzyme refractoriness and impermeability of cells for DFMO as the possible causes of DFMO resistance. The presence of polyamines in the peptone and PYG media as well as uptake of polyamines by the amoebae has been demonstrated. The growth and multiplication of A. culbertsoni in chemically defined medium was not affected by 1-5 mM DFMO while 10-20 mM DMFO yielded partial inhibition. A lowering of diaminopropane levels and enhancement of spermidine levels was observed in DFMO inhibited cells and level of ODC was drastically reduced in the inhibited cultures. Uptake of polyamines from the growth media may partly account for DFMO resistance of A. culbertsoni. Alternative mechanisms for DFMO resistance are indicated. 相似文献
27.
R Shanker R K Dogra S Khanna S N Srivastava L J Shukla S Gupta J C Katiyar 《Indian journal of experimental biology》1992,30(5):388-393
Pathomorphological and immunological studies were carried out on rodents following oral administration of 0, 0.1, 0.25 and 0.5% (w/w) metanil yellow, mixed in diet, for 30 days. No significant change in hematologic parameters and histologic architecture of liver, kidney, mesenteric lymph node, thymus and urinary bladder was observed except for mild desquamation of intestinal villi and moderate changes in Peyer's patches of small intestine with higher doses. Among immunological parameters, significant enhancement in the primary humoral immune response (anti-SRBC IgM plaque forming cells of spleen) was observed with the lowest dose of metanil yellow while higher doses produced opposing effects. An elevated cutaneous delayed type hypersensitivity (DTH) reaction to SRBC was seen in 0.1% metanil yellow treated animals but higher doses did not influence the reaction. The treatment also caused changes in functional capabilities of macrophages. Although these immune alterations could hardly influence the local immunity of gut, as measured by the capacity of animals to cause rejection of Nippostrongylus brasiliensis parasite, the potential to modulate the immunity in general by metanil yellow however assumes considerable biological significance. 相似文献
28.
The pattern of arterial supply to the various parts (clavicular, sternocostal and aponeurotic) of the pectoralis major muscle was studied in 7 cadaver dissections and 10 angiograms by injecting a radio-opaque substance. Three main arteries supplied the muscle, i.e. the pectoral branch of the thoracoacromial trunk (TAT-PB), the lateral thoracic artery and the perorating branch of the internal thoracic artery, supported by other branches of the TAT and the superior thoracic artery. It is observed that the TAT-PB, a chief vascular pedicle, anastomoses freely with other arteries and supplies most parts of the muscle. The present study is mainly focussed on the exclusion of the chief vascular pedicle of muscle to eliminate the confusion of previous studies and prevent the unnecessary hindrance and complications of the muscle flap. 相似文献
29.
30.
Glycophorin prepared by a lithium di-iodosalicylate-extraction/phenol-partition method was rich in polyphosphoinositides (phosphatidyl-myo-inositol 4-phosphate and phosphatidyl-myo-inositol 4,5-bisphosphate), but glycophorin extracted by Triton X-100 showed no such enrichment. The enrichment observed in the former preparations appeared not to be caused by pre-existing association between glycophorin and polyphosphoinositides in the human erythrocyte membrane, but to be largely a consequence of the preparative procedures. 相似文献