全文获取类型
收费全文 | 555篇 |
免费 | 1篇 |
国内免费 | 9篇 |
专业分类
系统科学 | 6篇 |
丛书文集 | 1篇 |
教育与普及 | 1篇 |
理论与方法论 | 3篇 |
现状及发展 | 75篇 |
研究方法 | 73篇 |
综合类 | 372篇 |
自然研究 | 34篇 |
出版年
2019年 | 3篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2013年 | 6篇 |
2012年 | 30篇 |
2011年 | 59篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2008年 | 31篇 |
2007年 | 47篇 |
2006年 | 32篇 |
2005年 | 27篇 |
2004年 | 29篇 |
2003年 | 20篇 |
2002年 | 29篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 11篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 11篇 |
1970年 | 7篇 |
1969年 | 3篇 |
1968年 | 9篇 |
1967年 | 8篇 |
1966年 | 4篇 |
1965年 | 6篇 |
排序方式: 共有565条查询结果,搜索用时 281 毫秒
61.
本书介绍了生物医学几个不同分支学科中有代表性的共同的研究方法。这些方法不仅使用最广泛,而且也是最基本的方法。书中概述了所介绍方法的目的、局限性,并提供了适用的替代方法。 相似文献
62.
Structural basis of the allosteric behaviour of phosphofructokinase 总被引:12,自引:0,他引:12
Comparison between the crystal structures of low- and high-affinity forms of phosphofructokinase shows a close coupling between the change of quaternary structure and local changes triggered by binding of the allosteric effectors. These concerted changes link all the substrate and effector sites in the tetramer, and explain the change of affinity for the cooperative substrate. 相似文献
63.
Nature of the motor element in electrokinetic shape changes of cochlear outer hair cells 总被引:25,自引:0,他引:25
It is the prevailing notion that cochlear outer hair cells function as mechanical effectors as well as sensory receptors. Electrically induced changes in the shape of mammalian outer hair cells, studied in vitro, are commonly assumed to represent an aspect of their effector process that may occur in vivo. The nature of the motile process is obscure, even though none of the established cellular motors can be involved. Although it is known that the motile response is under voltage control, it is uncertain whether the stimulus is a drop in the voltage along the long axis of the cell or variation in the transmembrane potential. We have now performed experiments with cells partitioned in differing degrees between two chambers. Applied voltage stimulates the cell membrane segments in opposite polarity to an amount dependent on the partitioning. The findings show, in accordance with previous suggestions, that the driving stimulus is a local transmembrane voltage drop and that the cellular motor consists of many independent elements, distributed along the cell membrane and its associated cortical structures. We further show that the primary action of the motor elements is along the longitudinal dimension of the cell without necessarily involving changes in intracellular hydrostatic pressure. This establishes the outer hair cell motor as unique among mechanisms that control cell shape. 相似文献
64.
65.
Critical role of an eight-amino acid sequence of VP1 in neutralization of poliovirus type 3 总被引:1,自引:0,他引:1
The three serotypes of poliovirus are members of the picornaviradae, a group of viruses which cause a variety of diseases of considerable importance in man and animals. We have previously used antigenic mutants resistant to neutralizing monoclonal antibodies to identify a single antigenic site for the neutralization of poliovirus type 3 (ref. 1). Evidence based on oligonucleotide mapping suggested that this site corresponded largely to one physicochemical region of the capsid protein viral polypeptide 1 (VP1). We now present conclusive evidence that most of the mutations conferring resistance to neutralization are confined to an eight-amino acid region of VP1, specified by a sequence of viral RNA 277-300 bases from the start of the region coding for VP1. These data strongly suggest that this small region constitutes a major antigenic site involved in virus neutralization and they provide the most detailed information currently available on the antigenic site of a human virus. 相似文献
66.
The c-erb-A gene encodes a thyroid hormone receptor 总被引:143,自引:0,他引:143
The cDNA sequence of human c-erb-A, the cellular counterpart of the viral oncogene v-erb-A, indicates that the protein encoded by the gene is related to the steroid hormone receptors. Binding studies with the protein show it to be a receptor for thyroid hormones. 相似文献
67.
M. L. Barrett A. M. Scutt F. J. Evans 《Cellular and molecular life sciences : CMLS》1986,42(4):452-453
Summary Two novel prenylat flavones, termed Cannflavin A and B, were isolated from the cannabinoid free ethanolic extract ofCannabis sativa L. Both compounds inhibited prostaglandin E2 production by human rheumatoid synovial cells in culture.This communication is dedicated to the memory of the late Professor J. W. Fairbairn and the late Dr. J. T. Pickens. We are grateful to the Medical Research Council for a project grant and to Ms J. Elliot of King's College London for NMR spectra. 相似文献
68.
69.
Structure of mouse kallikrein gene family suggests a role in specific processing of biologically active peptides 总被引:34,自引:0,他引:34
The glandular kallikrein gene family comprises 25-30 highly homologous genes that encode specific proteases involved in the processing of biologically active peptides. In the mouse all the members of this family are closely linked on chromosome 7. The 9.5-kilobase nucleotide sequence of a mouse genomic clone contains one complete kallikrein gene (mGK-1), which is expressed in the male mouse submaxillary gland, and the 3' end of another (mGK-2). Differences in the coding potential of these genes and the amino acid sequences of other known kallikreins seem to be functionally related to the substrate specificity of the different enzymes. 相似文献