全文获取类型
收费全文 | 14372篇 |
免费 | 1446篇 |
国内免费 | 8篇 |
出版年
2021年 | 133篇 |
2019年 | 109篇 |
2018年 | 141篇 |
2017年 | 127篇 |
2016年 | 248篇 |
2015年 | 377篇 |
2014年 | 390篇 |
2013年 | 553篇 |
2012年 | 697篇 |
2011年 | 715篇 |
2010年 | 483篇 |
2009年 | 425篇 |
2008年 | 650篇 |
2007年 | 703篇 |
2006年 | 665篇 |
2005年 | 672篇 |
2004年 | 709篇 |
2003年 | 622篇 |
2002年 | 652篇 |
2001年 | 234篇 |
2000年 | 199篇 |
1999年 | 257篇 |
1998年 | 212篇 |
1997年 | 155篇 |
1996年 | 168篇 |
1995年 | 147篇 |
1994年 | 187篇 |
1993年 | 158篇 |
1992年 | 166篇 |
1991年 | 176篇 |
1990年 | 174篇 |
1989年 | 164篇 |
1988年 | 147篇 |
1987年 | 157篇 |
1986年 | 164篇 |
1985年 | 176篇 |
1984年 | 168篇 |
1983年 | 151篇 |
1982年 | 204篇 |
1981年 | 221篇 |
1980年 | 212篇 |
1979年 | 151篇 |
1978年 | 176篇 |
1977年 | 156篇 |
1976年 | 146篇 |
1975年 | 113篇 |
1974年 | 152篇 |
1973年 | 149篇 |
1970年 | 102篇 |
1969年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Xu Zhang Wei Zhang Santosh L. Saraf Mehdi Nouraie Jin Han Michel Gowhari Johara Hassan Galina Miasnikova Adelina Sergueeva Sergei Nekhai Rick Kittles Roberto F. Machado Joe G. N. Garcia Mark T. Gladwin Martin H. Steinberg Paola Sebastiani Donald A. McClain Victor R. Gordeuk 《Human genetics》2015,134(8):895-904
32.
33.
A convenient procedure was developed for identifying selenocysteine in selenoproteins by mass spectroscopy, based on formation of the 2,4-dinitrophenyl (DNP) derivative. Pure ovine erythrocyte glutathione peroxidase was reduced with sodium borohydride and reacted with 1-fluoro-2,4-dinitrobenzene at neutral pH under anaerobic conditions in 4 M guanidine. The inactivated enzyme was hydrolyzed with 6 N HCl for 20 h at 110 degrees C under anaerobic conditions. Following extraction of the hydrolysate with benzene, Se-(2,4-dinitrophenyl)selenocysteine in the aqueous phase was separated from non-DNP-amino acids by gel-filtration chromatography and then separated from other water-soluble DNP-amino acids by reversed-phase high-performance liquid chromatography. The Se-(2,4-dinitrophenyl)selenocysteine was converted to Se-methyl-N-(2,4-dinitrophenyl)selenocysteine by the addition of sodium barbital to induce an intramolecular Se leads to N shift (Smiles rearrangement) under anaerobic conditions, in the presence of methyl iodide to trap the liberated selenol group. Following esterification of the product's carboxyl group with methanol and hydrochloric acid, it was subjected to direct probe mass spectroscopy and identified as the methyl ester of Se-methyl-N-(2,4-dinitrophenyl)selenocysteine. This procedure allows selenocysteine to be isolated quite easily as a readily identifiable derivative and has permitted the first identification of a seleno amino acid in a protein by mass spectroscopy. 相似文献
34.
A new protein crosslinking agent, 2,3-dibromopropionyl-N-hydroxysuccinimide ester, has been synthesized and characterized. The potential use of this compound as a temperature-controllable heterobifunctional crosslinking agent has been investigated using model systems and its reactivity compared with that of chlorambucil-N-hydroxysuccinimide ester. The coupling of14C-labeled phenylethylamine to lysozyme has been used to illustrate the feasibility of the use of this crosslinking agent for the synthesis of immunotoxins. 相似文献
35.
36.
Donald W. Roy 《BMJ (Clinical research ed.)》1924,1(3298):496-497
37.
38.
Proteins assayed electrophoretically showed variation at only three of 49 presumed genetic loci in alligators from southwestern Louisiana. Average heterozygosity per individual was 0.021±0.012; proportion of polymorphic loci was 0.06. Data on the history, structure, and ecology of this alligator population are consistent with natural selection as the primary factor accounting for this low genetic variability. However, neither a historic population bottleneck nor some genetic mechanism limiting variability can be dismissed as a possible factor.The study was supported by NSF Grant BMS 73-0125 to H.C.D. 相似文献
39.
40.
Donald R. McCarty Christian B. Carson Mark Lazar S. Caprice Simonds 《Genesis (New York, N.Y. : 2000)》1989,10(6):473-481
The viviparous-1 (vp1) locus in maize is a developmental gene that controls diverse aspects of the maturation phase of seed development. Mutations of vp1 alter embryo sensitivity to the hormone abscisic acid and block formation of anthocyanin pigment. Molecular cloning of a Robertson Mutator-induced mutant allele, vp1-mum-1, by transposable element tagging has allowed analysis of several transposon-induced vp1 mutants. In the vp1-Mc mutation, the gene is disrupted by 4.0 kbp insertion, which results in expression of a 3′ truncated mRNA. Phenotypically, this allele is at least partially functional in causing embryo dormancy, but is ineffective in controlling anthocyanin expression. This result suggests that disruption of the C-terminal domain of the Vp1 protein specifically affects regulation of the anthocyanin pathway. A second Mutator- derived allele, vp1-mum2, exhibits an unusual form of somatic mutability in which endosperm cells revert from wild-type vp1 expression to a mutant condition. The vp1-mum2 allele contains a 1.5 kbp Insertion that has no detectable homology to known Mu elements. This element is retained In wild-type germinal revertants derived from vp1-mum2 An apparent DNA modification affecting cleavage at an internal Sstl restriction site in the element correlates with vp1-mum2 states that exhibit wild-type Vp1 expression. A model involving mitotic assortment of modified and unmodified DNA strands during development is proposed for vp1-mum2 somatic mutation. 相似文献