全文获取类型
收费全文 | 29654篇 |
免费 | 2598篇 |
国内免费 | 1573篇 |
出版年
2023年 | 227篇 |
2022年 | 571篇 |
2021年 | 1130篇 |
2020年 | 796篇 |
2019年 | 942篇 |
2018年 | 1009篇 |
2017年 | 758篇 |
2016年 | 1110篇 |
2015年 | 1689篇 |
2014年 | 1952篇 |
2013年 | 2151篇 |
2012年 | 2630篇 |
2011年 | 2333篇 |
2010年 | 1433篇 |
2009年 | 1318篇 |
2008年 | 1639篇 |
2007年 | 1490篇 |
2006年 | 1291篇 |
2005年 | 1233篇 |
2004年 | 1074篇 |
2003年 | 942篇 |
2002年 | 879篇 |
2001年 | 743篇 |
2000年 | 586篇 |
1999年 | 561篇 |
1998年 | 262篇 |
1997年 | 256篇 |
1996年 | 238篇 |
1995年 | 210篇 |
1994年 | 183篇 |
1993年 | 138篇 |
1992年 | 228篇 |
1991年 | 193篇 |
1990年 | 171篇 |
1989年 | 149篇 |
1988年 | 134篇 |
1987年 | 124篇 |
1986年 | 106篇 |
1985年 | 109篇 |
1984年 | 85篇 |
1983年 | 55篇 |
1982年 | 62篇 |
1981年 | 50篇 |
1980年 | 42篇 |
1979年 | 56篇 |
1978年 | 48篇 |
1977年 | 56篇 |
1976年 | 52篇 |
1974年 | 44篇 |
1973年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
R Liang 《Biochemical and biophysical research communications》1984,120(3):741-746
Primary cell cultures were prepared from breast muscles of 11 day 4 hour-embryonic chicks. Cytoplasmic RNAs were isolated from the cultured cells at various time intervals from day 3 to day 8. A [P32] DNA probe complementary to messenger RNA of myosin heavy chain was used to hybridize with the RNAs after gel electrophoresis. A transient species of polyadenylated RNA with a decreased mobility in electrophoresis was detected during a period of time when contractions of syncytial fibers were first observed. 相似文献
2.
3.
Siew Choo Lim Matthew W. Bowler Ting Feng Lai Haiwei Song 《Nucleic acids research》2012,40(21):11009-11022
Mutations in immunoglobulin µ-binding protein 2 (Ighmbp2) cause distal spinal muscular atrophy type 1 (DSMA1), an autosomal recessive disease that is clinically characterized by distal limb weakness and respiratory distress. However, despite extensive studies, the mechanism of disease-causing mutations remains elusive. Here we report the crystal structures of the Ighmbp2 helicase core with and without bound RNA. The structures show that the overall fold of Ighmbp2 is very similar to that of Upf1, a key helicase involved in nonsense-mediated mRNA decay. Similar to Upf1, domains 1B and 1C of Ighmbp2 undergo large conformational changes in response to RNA binding, rotating 30° and 10°, respectively. The RNA binding and ATPase activities of Ighmbp2 are further enhanced by the R3H domain, located just downstream of the helicase core. Mapping of the pathogenic mutations of DSMA1 onto the helicase core structure provides a molecular basis for understanding the disease-causing consequences of Ighmbp2 mutations. 相似文献
4.
Yunfan Sun Liang Wu Yu Zhong Kaiqian Zhou Yong Hou Zifei Wang Zefan Zhang Jiarui Xie Chunqing Wang Dandan Chen Yaling Huang Xiaochan Wei Yinghong Shi Zhikun Zhao Yuehua Li Ziwei Guo Qichao Yu Liqin Xu Jia Fan 《Cell》2021,184(2):404-421.e16
- Download : Download high-res image (233KB)
- Download : Download full-size image
5.
6.
7.
8.
9.
Interaction of gentamicin and spermine with bilayer membranes containing negatively charged phospholipids 总被引:12,自引:0,他引:12
We measured the electrophoretic mobility of multilamellar phospholipid vesicles, the 31P NMR spectra of both sonicated and multilamellar vesicles, and the conductance of planar bilayer membranes to study the binding of spermine and gentamicin to membranes. Spermine and gentamicin do not bind significantly to the zwitterionic lipid phosphatidylcholine. We measured the concentrations of gentamicin and spermine that reverse the charge on vesicles formed from a mixture of phosphatidylcholine and either phosphatidylserine or phosphatidylinositol. From these measurements, we determined that the intrinsic association constants of the cations with these negative lipids are all about 10 M-1. This value is orders of magnitude lower than the apparent binding constants reported in the literature by other groups because the negative electrostatic surface potential of the membranes and the resultant accumulation of these cations in the aqueous diffuse double layer adjacent to the membranes have not been explicitly considered in previous studies. Our main conclusion is that the Gouy-Chapman-Stern theory of the aqueous diffuse double layer can describe surprisingly well the interaction of gentamicin and spermine with bilayer membranes formed in a 0.1 M NaCl solution if the negative phospholipids constitute less than 50% of the membrane. Thus, the theory should be useful for describing the interactions of these cations with the bilayer component of biological membranes, which typically contain less than 50% negative lipids. For example, our results support the suggestion of Sastrasinh et al. [Sastrasinh, M., Krauss, T. C., Weinberg, J. M., & Humes, H. D. (1982) J. Pharmacol. Exp. Ther. 222, 350-358] that phosphatidylinositol is the major binding site for gentamicin in renal brush border membranes. 相似文献
10.
The Rd gene is expressed in the livers and oviducts of laying hens and codes for the riboflavin-binding protein (RfBP) of egg yolk and egg white. A lambda gt11 cDNA library derived from chicken oviduct poly(A)+ RNA was screened with polyclonal rabbit antiserum to chicken RfBP. Positive clones were isolated and rescreened with a mixed oligonucleotide probe corresponding to residues 20-25 of the mature protein. The largest cDNA clone (969 base pairs) was subcloned into plasmid pIBI21, and the nucleotide sequence was determined by the dideoxynucleotide method. This clone contained the entire coding region for RfBP. The published amino acid sequence of the mature protein was confirmed. In addition, the following 17-residue signal peptide was deduced: Met-Leu-Arg-Phe-Ala-Ile-Thr-Leu-Phe-Ala-Val-Ile-Thr-Ser-Ser-Thr-Cys. Unexpectedly, the nucleotide sequence codes for 2 adjacent arginine residues at the carboxyl terminus that are not observed in the mature protein. The amino acid sequence of RfBP is homologous with bovine milk folate-binding protein. Eight of the nine pairs of cysteines involved in disulfide bonds in RfBP are conserved in folate-binding protein, as are all of the tryptophan residues. Sequence identity between homologous regions of these two vitamin-binding proteins is more than 30%. 相似文献