全文获取类型
收费全文 | 4535篇 |
免费 | 448篇 |
国内免费 | 4篇 |
专业分类
4987篇 |
出版年
2023年 | 23篇 |
2022年 | 30篇 |
2021年 | 62篇 |
2020年 | 28篇 |
2019年 | 41篇 |
2018年 | 68篇 |
2017年 | 55篇 |
2016年 | 91篇 |
2015年 | 142篇 |
2014年 | 167篇 |
2013年 | 238篇 |
2012年 | 260篇 |
2011年 | 234篇 |
2010年 | 176篇 |
2009年 | 169篇 |
2008年 | 226篇 |
2007年 | 253篇 |
2006年 | 245篇 |
2005年 | 223篇 |
2004年 | 198篇 |
2003年 | 180篇 |
2002年 | 201篇 |
2001年 | 70篇 |
2000年 | 100篇 |
1999年 | 101篇 |
1998年 | 94篇 |
1997年 | 61篇 |
1996年 | 58篇 |
1995年 | 47篇 |
1994年 | 67篇 |
1993年 | 65篇 |
1992年 | 60篇 |
1991年 | 63篇 |
1990年 | 59篇 |
1989年 | 49篇 |
1988年 | 51篇 |
1987年 | 36篇 |
1986年 | 32篇 |
1985年 | 50篇 |
1984年 | 41篇 |
1983年 | 33篇 |
1982年 | 43篇 |
1981年 | 42篇 |
1980年 | 38篇 |
1979年 | 38篇 |
1978年 | 21篇 |
1977年 | 25篇 |
1976年 | 28篇 |
1975年 | 30篇 |
1974年 | 34篇 |
排序方式: 共有4987条查询结果,搜索用时 0 毫秒
1.
Pierre Fellmann Jens Andersen Philippe F. Devaux Marc le Maire Alain Bienvenue 《Biochemical and biophysical research communications》1980,95(1):289-295
A spin labeled fatty acid (16-doxylstearic acid) was linked to a photochemical reacting group (azido derivative). When the molecule is introduced, at a low concentration, into rabbit sarcoplasmic reticulum membranes, the spectrum before illumination is identical to the spectrum obtained with the corresponding spin labeled fatty acid. After illumination, a large immobilized components is seen. It corresponds to about 70% of the ESR signal of the effectively bound label, at room temperature. The fraction of immobilized component varies with temperature, from 100% at 0°C to 50% at 35°C. Addition of a small amount of detergent (dodecyl octaethylene glycol monoether), under non solubilizing conditions, decreases the fraction of signal due to a strongly immobilized probe. A possible interpretation is that the immobilized signal reflects protein bound spin labels trapped in Ca2+ ATPase oligomers, which are partially dissociated by detergent addition or temperature increase. 相似文献
2.
3.
Sylvie Cablé Michèle Kedinger Michel Dauça 《Differentiation; research in biological diversity》1993,54(2):99-108
Abstract. The development of peroxisomes and expression of their enzymes were investigated in differentiating intestinal epithelial cells during their migration along the crypt-villus axis. Sequential cell populations harvested by a low-temperature method were identified by microscopy, determination of alkaline phosphatase and sucrase activities and incorporation of [3 H]-thymidine into DNA. Ultrastructural cytochemistry after staining for catalase activity, revealed the presence of peroxisomes in undifferentiated stem cells located in the crypt region. Morphometry indicated that the number of these organelles increased as intestinal epithelial cells differentiate. Catalase activity was higher in the crypt cells than in the mature enterocytes harvested from villus tips. On the other hand, an increasing gradient of activity was observed from crypts to villus tips for peroxisomal oxidases, i.e. fatty acyl coA oxidase, D-amino acid oxidase and polyamine oxidase. These findings indicate that biogenesis of peroxisomes occurs during migration of intestinal epithelial cells along the crypt-villus axis and that peroxisomal oxidases contribute substantially to the biochemical maturation of enterocytes. 相似文献
4.
5.
Four main molecular forms of acetylcholinesterase (AChE) can be solubilized from newborn rat superior cervical ganglia (SCG), homogenized in the presence of a high-ionic-strength, detergent-containing medium. These forms, respectively referred to as 16, 10, 6.5, and 4 S, are characterized by their sedimentation coefficients. Their relative proportions in SCG are notably different in vivo during postnatal maturation, and in culture. The 16-S AChE appears to be mainly neuronal in origin, is maintained in culture independently of original presynaptic in vivo elements, and its cellular pool is not depleted in the presence of tetrodotoxin (TTX). 相似文献
6.
A predominant idiotype on rabbit anti-VH a1 allotype antibodies: sharing by both major and minor VH subgroups 总被引:2,自引:0,他引:2
In every rabbit examined, greater than or equal to 80% of antibodies directed against the VH allotypic marker, a1, bears a predominant idiotype (IdX-a1). The IdX-a1 marker is site-associated and expressed on H chains, but not L chains, of anti-a1 antibody. Experiments using rabbits suppressed for the VH a subgroup demonstrated that IdX-a1 can be associated with both major (a+) and minor (a-) VH subgroup gene products and that a1 rabbits contain IdX-a1 within their genetic repertoire. The genetic and regulatory implications of our results are discussed. 相似文献
7.
C-Glycosylflavonoids. The chemistry of aspalathin 总被引:1,自引:0,他引:1
1. The isolation of aspalathin, the principal phenolic constituent in the leaves of Aspalathus linearis, is described and its properties are discussed. 2. The compound has been identified as 3'-C-beta-d-glucopyranosyl-2',3,4,4',6'-pentahydroxydihydrochalcone by the preparation and analysis of various derivatives, by photochemical oxidation to 2,3-dihydroiso-orientin and by nuclear-magnetic-resonance studies. 相似文献
8.
P Navarro-Rosinés C Roux A Bellemère 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》2001,324(5):443-451
An ultrastructural study of Weddellomyces epicallopisma (ascomata wall, asci, ascospores and vegetative hyphae), the first done on the family Dacampiaceae, confirms most of the observations made in light microscopy. Moreover it shows that ascospores are provided with an endospore (not visible in light microscope) and that the structure of the ascospore septum is more complex. The similarity of the wall structure between the ascospore and the hyphoid appendages, developed on the upper part of the ascoma, is emphasized. 相似文献
9.
10.
Nucleotide sequence of 10 kilobases of rat tyrosine aminotransferase gene 5'' flanking region. 总被引:5,自引:3,他引:2
J Oddos T Grange K D Carr B Matthews J Roux H Richard-Foy R Pictet 《Nucleic acids research》1989,17(21):8877-8878