全文获取类型
收费全文 | 2320篇 |
免费 | 242篇 |
国内免费 | 2篇 |
出版年
2023年 | 11篇 |
2022年 | 34篇 |
2021年 | 38篇 |
2020年 | 35篇 |
2019年 | 41篇 |
2018年 | 38篇 |
2017年 | 55篇 |
2016年 | 66篇 |
2015年 | 91篇 |
2014年 | 110篇 |
2013年 | 114篇 |
2012年 | 178篇 |
2011年 | 217篇 |
2010年 | 153篇 |
2009年 | 107篇 |
2008年 | 117篇 |
2007年 | 120篇 |
2006年 | 96篇 |
2005年 | 90篇 |
2004年 | 92篇 |
2003年 | 81篇 |
2002年 | 75篇 |
2001年 | 36篇 |
2000年 | 30篇 |
1999年 | 34篇 |
1998年 | 17篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 16篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 25篇 |
1990年 | 21篇 |
1989年 | 27篇 |
1988年 | 17篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 27篇 |
1983年 | 12篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 11篇 |
1975年 | 11篇 |
1974年 | 15篇 |
1973年 | 12篇 |
1972年 | 17篇 |
1970年 | 12篇 |
排序方式: 共有2564条查询结果,搜索用时 468 毫秒
1.
This study used monoclonal antibodies to sheep MHC class II molecules as well as an L cell transfectant (T8.1) which expresses DRA and DRB genes to show that two distinct DRβ chains are expressed in the sheep. Two anti-β chain specific monoclonal antibodies VPM37 and VPM43 react with DR antigen but not DQ antigen by ELISA. These two antibodies do not react with the DRβ chain expressed in the T8.1 cell line. Two-dimensional immunoblotting shows that these antibodies recognize a subgroup of the spots recognized by the DR-specific monoclonal antibody VPM57 which does react with the T8.1 β chain. Amino-terminal sequence analysis of the α chain associated with VPM37β chain shows that this α chain is homologous to the human DRα chain strongly indicating that the β chain is DR-like. VPM37 and VPM43 are shown to be directed against different epitopes on sheep MHC class II molecules so it is highly unlikely that the data can be explained by the presence of posttranslational modifications or the existence of a very common allele. These data provide clear evidence for the expression of two distinct DRP chains in the sheep. 相似文献
2.
3.
A valinomycin-mediated potassium conductivity has been studied using a glass U-tube in which two aqueous compartments are separated by a fritted glass filter impregnated with valinomycin and one or more pure phospholipids. This system can be used to detect the beginning and end of lateral phase separations in binary lipid mixtures, and also demonstrates a pronounced maximum in electrical conductivity of dipalmitoyl phosphatidylcholine at the transition temperature, 41°C. 相似文献
4.
No consensus exists concerning the mechanisms, distribution,or adaptive significance of consciousness. Agreement on anyone of these issues would aid in resolving others. Given a reliablebehavioral or neuroanatomical test for consciousness, we couldmap its distribution and describe its evolution. Conversely,if we knew its distribution, we could assess its adaptive valueand look for similarly distributed neuroanatomies to help usget at its mechanisms. Morgan's Canonthe rule that we should avoid attributinghumanlike mental states to other animals whenever possibleimpedesthe use of the comparative method in unraveling this knot. Ifinterpreted in this context as a parsimony criterion, Morgan'sCanon is logically equivalent to epiphenomenalism. It is parsimoniousif and only if conscious mental events play no causal role inhuman behavior and human consciousness has no adaptive significance.Rejecting this conclusion entails rejecting the parsimony interpretationof Morgan's Canon. 相似文献
5.
6.
7.
Heat shock-induced changes in the structural stability of proteinaceous karyoskeletal elements in vitro and morphological effects in situ 总被引:15,自引:5,他引:10
下载免费PDF全文
![点击此处可从《The Journal of cell biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Karyoskeletal protein fractions prepared from Drosophila melanogaster embryos contain morphologically identifiable remnants of nuclear pore complexes and peripheral lamina as well as what appears to be an internal nuclear "matrix" (Fisher, P. A., M. Berrios, and G. Blobel, 1982, J. Cell Biol., 92: 674-686). Structural stability of these proteinaceous assemblies is dependent on thermal incubation in vitro (37 degrees C, 15 min) before subfractionation of nuclei. In the absence of such incubation, greater than 90% of the total karyoskeletal protein including major polypeptide components of internal "matrix," pore complexes, and the peripheral lamina, is solubilized by 1 M NaCl. In vivo heat shock induces karyoskeletal stabilization resembling that resulting from thermal incubation in vitro. Immunocytochemical studies have been used to establish the effects of heat shock on the organization and distribution of major karyoskeletal marker proteins in situ. Taken together, these results are consistent with the notion that in vivo, regulation of karyoskeletal plasticity (and perhaps form) may be a functionally significant component of the Drosophila heat shock response. They also have broad practical implications for studies pertaining to the structure and function of karyoskeletal protein (nuclear "matrix") fractions isolated from higher eukaryotic cells. 相似文献
8.
Mapping of the gene for anti-müllerian hormone to the short arm of human chromosome 19 总被引:3,自引:0,他引:3
O Cohen-Haguenauer J Y Picard M G Mattéi S Serero V C Nguyen M F de Tand D Guerrier M C Hors-Cayla N Josso J Frézal 《Cytogenetics and cell genetics》1987,44(1):2-6
The gene coding for human anti-Müllerian hormone (AMH) was localized to subbands p13.2----p13.3 on chromosome 19, using in situ hybridization and Southern blot analysis of a panel of man-mouse and man-hamster somatic cell hybrids. 相似文献
9.
B McConnell 《Nucleic acids research》1987,15(23):10007-10020
The two amino protons of 3', 5'-cyclic guanosine monophosphate are shown to differ drastically in their solvent exchange properties: One is rapidly exchanging and sensitive to buffer catalysis; the other slow and insensitive. This observation accounts for the marked contrast between stopped-flow and NMR observations on buffer catalysis of amino proton exchange in guanosine monophosphates. The amino protons of guanine compounds traverse a "fast" solvent exchange position through the process of amino rotation, which together with kinetic considerations and comparative data on adenine and cytosine compounds, supports proposals of solvent exchange mediated by events at the guanine (N-3) site, rather than the (N-7) site. Exchange does not conform to rate expressions used by different workers for amino proton exchange. 相似文献
10.
Two enterotoxigenic Escherichia coli strains of serotype 0.25.H42 that produced coli surface associated antigens CS4 and CS6 hybridized with a probe containing the cfaD sequence that regulates expression of colonization factor antigen CFA/I. Transformation of a cloned cfaD gene into some derivatives of the strains that were negative for CS4 and CS6 resulted in expression of CS4 but not CS6. By hybridization the sequence that regulated CS4 production in the wild type 025 strains was located on a plasmid that also encoded the CS6 antigen. The structural genes for the CS4 antigen were on a separate plasmid. The 025 strains carried a third plasmid encoding enterotoxin production which was therefore unlinked to regulation sequences or genes encoding CS antigens. 相似文献