全文获取类型
收费全文 | 2638篇 |
免费 | 222篇 |
国内免费 | 1篇 |
出版年
2023年 | 12篇 |
2022年 | 31篇 |
2021年 | 54篇 |
2020年 | 38篇 |
2019年 | 34篇 |
2018年 | 44篇 |
2017年 | 43篇 |
2016年 | 68篇 |
2015年 | 110篇 |
2014年 | 114篇 |
2013年 | 135篇 |
2012年 | 185篇 |
2011年 | 162篇 |
2010年 | 105篇 |
2009年 | 111篇 |
2008年 | 144篇 |
2007年 | 132篇 |
2006年 | 114篇 |
2005年 | 129篇 |
2004年 | 134篇 |
2003年 | 111篇 |
2002年 | 131篇 |
2001年 | 46篇 |
2000年 | 26篇 |
1999年 | 39篇 |
1998年 | 30篇 |
1997年 | 24篇 |
1996年 | 27篇 |
1995年 | 27篇 |
1994年 | 32篇 |
1993年 | 18篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 15篇 |
1988年 | 21篇 |
1987年 | 27篇 |
1985年 | 26篇 |
1984年 | 28篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 16篇 |
1977年 | 18篇 |
1976年 | 17篇 |
1975年 | 11篇 |
1973年 | 21篇 |
1972年 | 11篇 |
1971年 | 11篇 |
排序方式: 共有2861条查询结果,搜索用时 31 毫秒
71.
Mode of formation of cholesta-5,7-dien-3β-ol from cholest-5-en-3β-ol by larvae of Calliphora erythrocephala
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
1. The conversion of cholest-5-en-3beta-ol (cholesterol) into cholesta-5,7-dien-3beta-ol by axenic Calliphora erythrocephala larvae was demonstrated. 2. The transformation is probably direct (Delta(5)-->Delta(5,7)) and does not involve a Delta(0) intermediate (Delta(5)-->Delta(0)-->Delta(7)--> Delta(5,7)). 3. Delta(7)-bond formation involves the stereospecific elimination of the 7beta hydrogen atom. 4. The relative amounts of free and esterified sterols were determined in larvae grown on cholesterol as sole sterol source and on 5alpha-cholestan-3beta-ol supplemented with minimal amounts of cholesterol. 5. The significance of the results is assessed in relation to the probable role of cholesta-5,7-dien-3beta-ol as an intermediate in the biosynthesis of ecdysones. 相似文献
72.
73.
The largest non-unit eigenvalue λ of the transition matrix for the Wright-Fisher Markov chain model of random genetic drift is found numerically with selective advantages of genotypes taken into account. Polynomials in the selection coefficients are fitted to λ in order to summarize the behaviour of λ with varying selection. Also found are the values of the selective advantages which give rise to an acceleration to the rate of fixation of alleles. These values are compared to results for the diffusion approximation to the Wright-Fisher model. 相似文献
74.
Trevor Baines 《BMJ (Clinical research ed.)》1985,291(6501):1050-1051
75.
Trevor Lukey Kuldeep Neote John F. Loman Ardythe E. Unger Fred G. Biddle Floyd F. Snyder 《Biochemical genetics》1985,23(3-4):347-356
An improved method for detecting four Np-1 (purine nucleoside phosphorylase) alleles in mouse erythrocytes by cellulose acetate electrophoresis is described. The previous linkage of Np-1 and Es-10 (esterase-10) was confirmed, with a map distance of 13.0±2.6 cM. Np-2 was detected by either specific activity assay or starch gel electrophoresis and shown to be linked to Es-10, 15.9 ± 3.1 cM, on chromosome 14. No recombinants between Np-1 and Np-2 were observed in 52 offspring, indicating either that these loci are either closely associated or that Np-2 represents simply a property of existing allelic products of the Np-1 locus.This research was supported by Medical Research Council of Canada grants to F.G.B. and F.F.S. 相似文献
76.
77.
78.
79.
Sura Ali Benjamin Jenkins Jiujun Cheng Briallen Lobb Xin Wei Suhelen Egan Trevor C. Charles Brendan J. McConkey John Austin Andrew C. Doxey 《Molecular microbiology》2020,114(6):979-990
S-layers are paracrystalline proteinaceous lattices that surround prokaryotic cells, forming a critical interface between the cells and their extracellular environment. Here, we report the discovery of a novel S-layer protein present in the Gram-negative marine organism, Pseudoalteromonas tunicata D2. An uncharacterized protein (EAR28894) was identified as the most abundant protein in planktonic cultures and biofilms. Bioinformatic methods predicted a beta-helical structure for EAR28894 similar to the Caulobacter S-layer protein, RsaA, despite sharing less than 20% sequence identity. Transmission electron microscopy revealed that purified EAR28894 protein assembled into paracrystalline sheets with a unique square lattice symmetry and a unit cell spacing of ~9.1 nm. An S-layer was found surrounding the outer membrane in wild-type cells and completely removed from cells in an EAR28894 deletion mutant. S-layer material also appeared to be “shed” from wild-type cells and was highly abundant in the extracellular matrix where it is associated with outer membrane vesicles and other matrix components. EAR28894 and its homologs form a new family of S-layer proteins that are widely distributed in Gammaproteobacteria including species of Pseudoalteromonas and Vibrio, and found exclusively in marine metagenomes. We propose the name Slr4 for this novel protein family. 相似文献
80.