全文获取类型
收费全文 | 4246篇 |
免费 | 281篇 |
国内免费 | 5篇 |
出版年
2023年 | 22篇 |
2022年 | 46篇 |
2021年 | 145篇 |
2020年 | 48篇 |
2019年 | 64篇 |
2018年 | 107篇 |
2017年 | 80篇 |
2016年 | 131篇 |
2015年 | 167篇 |
2014年 | 241篇 |
2013年 | 311篇 |
2012年 | 350篇 |
2011年 | 362篇 |
2010年 | 214篇 |
2009年 | 224篇 |
2008年 | 230篇 |
2007年 | 232篇 |
2006年 | 202篇 |
2005年 | 155篇 |
2004年 | 168篇 |
2003年 | 131篇 |
2002年 | 109篇 |
2001年 | 60篇 |
2000年 | 70篇 |
1999年 | 39篇 |
1998年 | 22篇 |
1997年 | 26篇 |
1996年 | 15篇 |
1995年 | 27篇 |
1994年 | 21篇 |
1993年 | 32篇 |
1992年 | 30篇 |
1991年 | 42篇 |
1990年 | 21篇 |
1989年 | 20篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 16篇 |
1985年 | 28篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1979年 | 21篇 |
1977年 | 13篇 |
1976年 | 14篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 26篇 |
1972年 | 13篇 |
1971年 | 16篇 |
1967年 | 14篇 |
排序方式: 共有4532条查询结果,搜索用时 15 毫秒
1.
2.
3.
Nitrous oxide (N2O) decreased in vivo oxidation of histidine in rats fed a basal diet marginally deficient in methionine, although hepatic levels of S-adenosylmethionine (AdoMet) were not significantly altered. Excess dietary methionine increased hepatic levels of AdoMet and increased histidine oxidation. However, it did not protect histidine oxidation when the rats were treated with N2O. Parenteral administration of methionine greatly increased hepatic levels of AdoMet and increased histidine oxidation in normal and N2O treated rats. This indicates that when hepatic levels of AdoMet are greatly elevated by administration of methionine, N2O does not affect in vivo histidine oxidation. 相似文献
4.
Summary Maximum lipase production byAspergillus foetidus was obtained from cultures grown in the medium of 2% olive oil and 0.5% sucrose. The optimal conditions for the production of lipases in the Multigen fermenters were found to be at 500rpm with an airflow of 1.5 liter per mimute. Immobilization of the fungal source was found to be infeasible in natural polymers. 相似文献
5.
It is shown for the first time that the content of ubiquinone of liver increases (2.5 fold) on dietary administration of the
widely-used industrial Plasticizer diethylhexyl Phthalate to the rat. The increase is localized almost entirely in mitochondria
in which the concentration of the quinone Per mg Protein is 1.7 times the control. IncorPoration of the radioactive Precursor
(acetate) reveals that the biosynthesis of ubiquinone is increased in the livers of Plasticizer-administered animals. The
rate of degradation is not altered. 相似文献
6.
Lectins, the divalent or polyvalent (glyco) proteins of non-immune origin of the cells agglutinate cells or other materials,
that display more than one saccharide of sufficient complementarity. Lectins considered ‘identical’ in terms of mono-and disaccharide
specificity can be differentiated by their ability to recognise the fine differences in more complex structures. The present
review discusses the interaction of lectins with various oligosaccharides and their resultant separations due to structural
variations. 相似文献
7.
Non-pathogenic, environmental strain ofVibrio cholerae, ELTOR Ogawa EW6 carries a copy of the cholera toxin gene in its chromosome. Restriction enzyme digestion followed by Southern
blot analysis revealed that the structure of the cholera toxin gene in this organism is different from that found in the virulent
strains. The xbaI site which has been found to be conserved in the cholera toxin of the virulent strains examined so far,
is absent here. Results of the RNA dot blot analysis indicated that the cholera toxin gene in EW6 is transcribed much less
efficiently compared to the cholera toxin gene present in the virulent strainVibrio cholerae classical Inaba 569B. 相似文献
8.
The development of sclerotia of Botrytis cinerea was examined at four stages during their maturation. The surface structure developed a network of profusely branched hyphae through their coalescence to a compact sclerotial body which was maturated by the deposition of melanin pigment. A characteristic feature of the hyphal cells of B. cinerea during the later stages of development was the presence of paramural bodies (plasmalemmasomes and lomasomes). Electrondense bodies with a limiting double-membrane congregated against the transverse septa of hyphal cells as sclerotia matured and may migrate from cell to cell through septal pores. We suggest that these and the lipid bodies found in hyphal cells may have a storage function in the resting sclerotia. 相似文献
9.
Paul J. Chuba Myron A. Leon Amit Banerjee Sunil Palchaudhuri 《Molecular & general genetics : MGG》1989,216(2-3):287-292
Summary
Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum. The recombinant plasmid also conferred group II surface exclusion, i.e. the cells were reduced in recipient ability towards the incoming plasmid R538drd in conjugation experiments. Southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2. Determination of the DNA sequence of the fragment demonstrated the presence of a truncated IS2 (165 bp), separated by 250 bp from a 900 bp stretch of homology with lambda DNA, beginning within the Rz gene and continuing in the rightward direction on the lambda map. A 97 amino acid open reading frame (ORF) adjacent to Rz and on the opposite strand, remained intact in iss, with several amino acid changes. The ORF in iss is preceded by sequences resembling prokaryotic ribosome binding sites and promoters. 相似文献
10.
The -galactosidase (EC 3.2.1.32) of Corynebacterium murisepticum (inducible by lactose and galactose) was purified by successive column chromatography on Sephadex G-200, DEAE-Sephadex A-50 and DEAE-cellulose (DE52). The enzyme was found to be a dimer of identical subunits of molecular mass 100,000 daltons. The K
m values of the enzyme for the substrates lactose and o-nitrophenyl--d-galactopyranoside (ONPG) are 16.7 mM and 4.4 mM, respectively, indicating, its low affinity for the substrates. The Ouchterlony immunodiffusion method exhibited immunological homogeneity of the enzyme preparation. The catalytic site of the enzyme does not take part in antigen-antibody reaction. 相似文献