全文获取类型
收费全文 | 2274篇 |
免费 | 222篇 |
国内免费 | 1篇 |
专业分类
2497篇 |
出版年
2023年 | 22篇 |
2022年 | 47篇 |
2021年 | 83篇 |
2020年 | 33篇 |
2019年 | 44篇 |
2018年 | 72篇 |
2017年 | 56篇 |
2016年 | 68篇 |
2015年 | 88篇 |
2014年 | 111篇 |
2013年 | 161篇 |
2012年 | 168篇 |
2011年 | 128篇 |
2010年 | 90篇 |
2009年 | 69篇 |
2008年 | 96篇 |
2007年 | 73篇 |
2006年 | 83篇 |
2005年 | 75篇 |
2004年 | 57篇 |
2003年 | 60篇 |
2002年 | 50篇 |
2001年 | 43篇 |
2000年 | 30篇 |
1999年 | 33篇 |
1998年 | 14篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 20篇 |
1992年 | 39篇 |
1991年 | 33篇 |
1990年 | 36篇 |
1989年 | 36篇 |
1988年 | 25篇 |
1987年 | 27篇 |
1986年 | 38篇 |
1985年 | 30篇 |
1984年 | 32篇 |
1983年 | 19篇 |
1982年 | 19篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 25篇 |
1978年 | 17篇 |
1977年 | 20篇 |
1976年 | 20篇 |
1975年 | 24篇 |
1974年 | 24篇 |
排序方式: 共有2497条查询结果,搜索用时 15 毫秒
51.
52.
Choudhury Aparajita Verma Shubham Muthamilarasan Mehanathan Rajam Manchikatla Venkat 《Molecular biology reports》2021,48(11):7477-7485
Molecular Biology Reports - Maruca vitrata is one of the potential insect pests that cause devastating losses to legume cultivation worldwide. Gene functional studies facilitate dissecting the... 相似文献
53.
54.
Chettri Dixita Verma Ashwani Kumar Sarkar Lija Verma Anil Kumar 《Extremophiles : life under extreme conditions》2021,25(3):203-219
Extremophiles - Technological advances in the field of life sciences have led to discovery of organisms that live in harsh environmental conditions referred to as extremophiles. These organisms... 相似文献
55.
Arti Kumari Ved Vrat Verma Rani Gupta 《World journal of microbiology & biotechnology》2012,28(11):3103-3111
Novel lipases lip11 and lip12 from Yarrowia lipolytica MSR80 were cloned and expressed in E. coli HB101 pEZZ18 system along with lip2. These enzymes were constitutively expressed as extracellular proteins with IgG tag. The enzymes were purified by affinity chromatography and analyzed by SDS-PAGE with specific activity of 314, 352 and 198?U/mg for Lip2, Lip11 and Lip12, respectively on olive oil. Biochemical characterization showed that all were active over broad range of pH 4.0?C9.0 and temperature 20?C80?°C with optima at pH 7 and 40?°C. All the three lipases were thermostable up to 80?°C with varying t1/2. Activity on various substrates revealed that they were most active on oils?>?triacylglycerides?>?p-np-esters. Relatively Lip2 and Lip11 showed specificity for mid to long chain fatty acids, while Lip12 was mid chain specific. GC analysis of triolein hydrolysis by these lipases revealed that Lip2 and Lip11 are regioselective, while Lip12 is not. Effect of metal ions showed that Lip2 and Lip12 were activated by Ca2+ whereas Lip11 by Mg2+. All were thiol activated and inhibited by PMSF and N-bromosuccinimide. All were activated by non polar solvents and inhibited by polar solvents. Detailed sequence analysis and structural predictions revealed Lip11 and Lip12 shared 61 and 62?% homology with Lip2 (3O0D) and three dimensional superimposition revealed Lip2 was closer to Lip11 than to Lip12 as was observed during biochemical characterization. Finally, thermostability and substrate specificity has been explained on the basis of detailed amino acid analysis. 相似文献
56.
57.
Mutational study of the bacterial hemoglobin distal heme pocket 总被引:1,自引:0,他引:1
Verma S Patel S Kaur R Chung YT Duk BT Dikshit KL Stark BC Webster DA 《Biochemical and biophysical research communications》2005,326(2):290-297
Ligand binding experiments on three mutants in the distal heme pocket of Vitreoscilla hemoglobin (GlnE7His, ProE8Ala, and GlnE7His,ProE8Ala) were used to probe the role of GlnE7 and ProE8 in the pocket's unusual structure. The oxygen dissociation constants for the wild type, E8Ala mutant, and E7His mutant proteins were 4.5, 4.7, and 1.7microM, respectively; the K(d) for the double mutant was not determinable by our technique. Visible-Soret spectra of the carbonyl and cyanyl forms and FT-IR of the carbonyl form of the E8 mutant were similar to those of the wild type; the opposite was true for the GlnE7His and GlnE7His,ProE8Ala mutants, which also differed from wild type in the visible-Soret spectra of their oxidized forms. Models of the effects of the mutations on distal pocket structure were consistent with the experimental findings, particularly the larger effects of the GlnE7His change. 相似文献
58.
59.
Verma S Nagarathnam D Shao J Zhang L Zhao J Wang Y Li T Mull E Enyedy I Wang C Zhu Q Altieri M Jordan J Dang TT Reddy S 《Bioorganic & medicinal chemistry letters》2005,15(8):1973-1977
A series of aminobenzimidazole-substituted pyrimidines were synthesized and evaluated for biochemical activity against CDK1. A high-speed parallel synthesis approach enabled the identification of a potent lead series having improved potency in the CDK1 assay (IC(50)<10nM). Cell cycle analysis showed that the compounds induced a G2/M block. Docking studies were carried out with a CDK1 homology model, and provide a rationale for the observed activities. 相似文献
60.
Mureins were isolated from two strains ofXanthomonas malvacearum, a phytopathogenic bacterium causing bacterial blight of cotton. The purity of murein was 70–95 % and the amino acid and amino sugar components (glutamic acid, alanine, meso-diaminopimelic acid, muramio acid and glucosamine) were present at the molar ratio of 1: 1.9: 1: 1.12: 0.85. The bacterium secreted a copious amount of slime which masked its surface structure. The slime was composed of densely interwoven network of filamentous material originating from the cell surface and extended into the medium without any discernable boundary. The slime was secreted through surface layers pores by force, giving the effect of a spray or jet. Slime also played a role in chain formation of bacterial cells. 相似文献