全文获取类型
收费全文 | 31629篇 |
免费 | 2550篇 |
国内免费 | 2903篇 |
出版年
2024年 | 61篇 |
2023年 | 434篇 |
2022年 | 1023篇 |
2021年 | 1650篇 |
2020年 | 1150篇 |
2019年 | 1437篇 |
2018年 | 1289篇 |
2017年 | 955篇 |
2016年 | 1426篇 |
2015年 | 1982篇 |
2014年 | 2429篇 |
2013年 | 2508篇 |
2012年 | 3091篇 |
2011年 | 2672篇 |
2010年 | 1684篇 |
2009年 | 1476篇 |
2008年 | 1671篇 |
2007年 | 1439篇 |
2006年 | 1265篇 |
2005年 | 1050篇 |
2004年 | 877篇 |
2003年 | 782篇 |
2002年 | 658篇 |
2001年 | 478篇 |
2000年 | 470篇 |
1999年 | 465篇 |
1998年 | 320篇 |
1997年 | 301篇 |
1996年 | 273篇 |
1995年 | 236篇 |
1994年 | 230篇 |
1993年 | 153篇 |
1992年 | 213篇 |
1991年 | 181篇 |
1990年 | 138篇 |
1989年 | 121篇 |
1988年 | 82篇 |
1987年 | 62篇 |
1986年 | 55篇 |
1985年 | 73篇 |
1984年 | 34篇 |
1983年 | 33篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1976年 | 10篇 |
1975年 | 11篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
W. D. Roof H. Q. Fang K. D. Young Jianling Sun & Ry Young 《Molecular microbiology》1997,25(6):1031-1046
slyD encodes a 196 amino acid polypeptide that is a member of the FKBP family of cis–trans peptidyl–prolyl isomerases (PPIases). slyD mutations affect plaque formation by the phage φX174 by blocking the action of the phage lysis protein E. Here we describe the selection of a set of spontaneous slyD mutations conferring resistance to the expression of gene E from a plasmid. These mutations occur disproportionately in residues of SlyD that, based on the structure of the prototype mammalian FKBP12, make ligand contacts with immunosuppressing drug molecules or are conserved in other FKBP proteins. A wide variation in the plating efficiency of φX174 on these E R strains is observed, relative to the parental, indicating that these alleles differ widely in residual SlyD activity. Moreover, it is found that slyD mutations cause significant growth rate defects in Escherichia coli B and C backgrounds. Finally, overexpression of slyD causes filamentation of the host. Thus, among the FKBP genes found in organisms across the evolutionary spectrum, slyD is unique in having three distinct drug-independent phenotypes. 相似文献
22.
23.
24.
25.
26.
Yuhui He Makusu Tsutsui Ralph H. Scheicher Chun Fan Masateru Taniguchi Tomoji Kawai 《Biophysical journal》2013
Experiments using nanopores demonstrated that a salt gradient enhances the capture rate of DNA and reduces its translocation speed. These two effects can help to enable electrical DNA sequencing with nanopores. Here, we provide a quantitative theoretical evaluation that shows the positive net charges, which accumulate around the pore entrance due to the salt gradient, are responsible for the two observed effects: they reinforce the electric capture field, resulting in promoted molecule capture rate; and they induce cationic electroosmotic flow through the nanopore, thus significantly retarding the motion of the anionic DNA through the nanopore. Our multiphysical simulation results show that, during the polymer trapping stage, the former effect plays the major role, thus resulting in promoted DNA capture rate, while during the nanopore-penetrating stage the latter effect dominates and consequently reduces the DNA translocation speed significantly. Quantitative agreement with experimental results has been reached by further taking nanopore wall surface charges into account. 相似文献
27.
Yan-Hong He Guo-Gui Ning Ya-Lin Sun Yan Hu Xing-Yu Zhao Man-Zhu Bao 《Molecular breeding : new strategies in plant improvement》2010,26(1):19-29
A male sterile line was isolated in marigold (Tagetes erecta L.) and cytological analysis determined this to be a novel genic male sterility trait (Tems). Through the use of amplified fragment length polymorphisms (AFLPs) and bulked segregant analysis (BSA), tightly linked
markers of Tems were identified with a view towards a map-based cloning strategy. It was found that spontaneous homeotic conversion of floral
organs was the underlying cause of the male sterility in this marigold line. Thus, petals of male sterile plants resembled
sepal-like structures and the stamens were partially converted to styles, although without the full characteristics or function
of the true style organs. We have constructed a fine marker-based map for the Tems gene. This is intended to provide a tool for marker assisted selection (MAS) strategies in hybrid breeding and map-based
cloning strategies for the male sterility locus. We discuss the significance of this spontaneously derived genic male sterility
trait relating to the homeotic conversion of floral organs in marigold. 相似文献
28.
29.
Abstract Morphological features of mature larvae of Petelia rivulosa (Butler), Exangerona prattiaria (Leech) and Culcula panterinaria (Bremer & Grey) of Ennominae are described and illustrated. All specimens examined are deposited in the Insect Collection of Department of Forest Resources Protection, Kangwon National University, Korea. 相似文献
30.
beta-Oxidation and Glyoxylate Cycle Coupled to NADH: Cytochrome c and Ferricyanide Reductases in Glyoxysomes
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Glyoxysomes isolated from castor bean (Ricinus communis L., var Hale) endosperm had NADH:ferricyanide reductase and NADH:cytochrome c reductase activities averaging 720 and 140 nanomole electrons/per minute per milligram glyoxysomal protein, respectively. These redox activities were greater than could be attributed to contamination of the glyoxysomal fractions in which 1.4% of the protein was mitochondrial and 5% endoplasmic reticulum. The NADH:ferricyanide reductase activity in the glyoxysomes was greater than the palmitoyl-coenzyme A (CoA) oxidation activity which generated NADH at a rate of 340 nanomole electrons per minute per milligram glyoxysomal protein. Palmitoyl-CoA oxidation could be coupled to ferricyanide or cytochrome c reduction. Complete oxidation of palmitoyl-CoA, yielding 14 nanomole electrons/per nanomole palmitoyl-CoA, was demonstrated with the acceptors, NAL, cytochrome c, and ferricyanide. Malate was also oxidized by glyoxysomes, if acetyl-CoA, ferricyanide, or cytochrome c was present. Glyoxysomal NADH:ferricyanide reductase activity has the capacity to support the combined rates of NADH generation by β-oxidation and the glyoxylate cycle. 相似文献