全文获取类型
收费全文 | 2948篇 |
免费 | 194篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 34篇 |
2020年 | 18篇 |
2019年 | 28篇 |
2018年 | 53篇 |
2017年 | 29篇 |
2016年 | 70篇 |
2015年 | 119篇 |
2014年 | 156篇 |
2013年 | 173篇 |
2012年 | 240篇 |
2011年 | 211篇 |
2010年 | 118篇 |
2009年 | 122篇 |
2008年 | 177篇 |
2007年 | 179篇 |
2006年 | 176篇 |
2005年 | 174篇 |
2004年 | 167篇 |
2003年 | 183篇 |
2002年 | 145篇 |
2001年 | 31篇 |
2000年 | 33篇 |
1999年 | 39篇 |
1998年 | 34篇 |
1997年 | 38篇 |
1996年 | 28篇 |
1995年 | 28篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 24篇 |
1991年 | 29篇 |
1990年 | 20篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1974年 | 6篇 |
1970年 | 5篇 |
1968年 | 6篇 |
排序方式: 共有3143条查询结果,搜索用时 15 毫秒
11.
Seasonal and inter-annual variations of nitrogen diagenesis in the sediments of a recently impounded basin 总被引:2,自引:2,他引:0
The Méry-sur-Oise (France) storage reservoir is an artificial basin of 9 m average depth, fed by water from the river Oise with a mean residence time of about 4 days. Sediments are accumulating at a rate of about 0.7 cm/month. In the sediments, two fractions of organic nitrogen with different rates of bacterial degradation could be distinguished, one associated with fresh phytoplankton, the other made of detrital and more refractory compounds. The fluxes of oxygen, nitrate and ammonium across the sediment-water interface were measured with a bell-jar system at different seasons during a 3 year period following flooding of the basin. The measurements show clear seasonal variations in relation with the variations of temperature and input of fresh phytoplanktonic material to the sediment. In addition, a long term trend of increasing ammonium was observed. Measurements were also carried out after dredging of all accumulated sediments of the basin. They showed a considerable reduction of the flux of nitrate to the sediments and a significant reduction of the flux of ammonium to the water column.These results are interpreted in the light of a non stationary model of N diagenesis in accumulating sediments. This model is able to predict at least the general trends of benthic N cycling of basins during the early stage of their ecological succession. 相似文献
12.
Atrazine and diuron resistant clones were isolated from diploid photoautotrophic protoplastderived colonies of Nicotiana plumbaginifolia. Protoplasts were mutagenised with 0.1 mM N-ethyl-N-nitrosourea and colonies were screened for resistance after plating. Selection of calli was carried out on their ability to grow and green on a selective medium containing either atrazine or diuron. Plants were regenerated from most tolerant calli. Herbicide spray showed that plants of 6 and 4 clones were resistant to atrazine and diuron, respectively.Abbreviations Atrazine
2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine
- diuron
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- NEU
N-ethyl-N-nitrosourea
- PSII
photosystem II 相似文献
13.
Marc-Henri Stern Fangrong Zhang Gilles Thomas Claude Griscelli Alain Aurias 《Human genetics》1988,81(1):18-22
Summary To delimit the 14q32.1 recurrent breakpoint of ataxia telangiectasia clones, we performed an in situ hybridization study with various probes located on the 14q32 band. We thus mapped this breakpoint between the D14S1 and Pi loci. Furthermore, an interstitial duplication including D14S1 and a part of the IgH locus was demonstrated on a t(14;14) clone. 相似文献
14.
Simone Grinfeld Paul Jacquet Jan Gilles Lucile Baugnet-Mahieu 《Development genes and evolution》1988,197(5):302-304
Summary In some strains of mice, eggs when X irradiated during the pronuclear stage, undergo a mitotic block in the G2 phase of the first cell cycle and cleave when the second division takes place in controls. The importance of this effect varies considerably with the strain and depends exclusively on the maternal genotype. In previous work, two-dimensional electrophoresis showed that eggs blocked at the one-cell stage after irradiation, undergo the same modifications in polypeptide synthesis as two-cell controls of the same age, except at the time of normal first mitosis, where three polypeptide sets of 30, 35 and 45 kDa appear only in cleaving controls. In the present study, we have found phosphorylations in dividing controls, on polypeptides of 30, 35 and 45 kDa. These phosphorylations are not seen in blocked irradiated eggs. 相似文献
15.
16.
Sylviane Olschwang Richard Fabre Pierre Laurent-Puig Anne Vassal Bernard Hamelin Yusuke Nakamura Gilles Thomas 《Human genetics》1992,88(6):658-660
Summary The EF5.44 locus is in close proximity to the chromosome 5 region to which the genetic defect responsible for familial adenomatous polyposis has been mapped. We have devised two oligonucleotides that promote the specific polymerase chain reaction (PCR) amplificiation of a 365-bp sequence in this region. Analysis by denaturing gradient gel electrophoresis of the resulting fragment has unravelled individual differences that could be identified as a single base pair change in aMnlI restriction site. This PCR assayable polymorphism increases the informativeness at this locus, and should be useful in the presymptomatic diagnosis of familial adenomatous polyposis. 相似文献
17.
Competitive exclusion of diarrheagenic Escherichia coli (ETEC) from human enterocyte-like Caco-2 cells by heat-killed Lactobacillus 总被引:7,自引:0,他引:7
Gilles Chauvière Marie-Hélène Coconnier Sophie Kerneis Arlette Darfeuille-Michaud Bernard Joly Alain L. Servin 《FEMS microbiology letters》1992,91(3):213-217
Diarrheagenic Escherichia coli (ETEC) bearing CFA/I or CFA/II adhesive factors specifically adhere onto the brush border of the polarized epithelial human intestinal Caco-2 cells in culture. Heat-killed Lactobacillus acidophilus strain LB, that adheres onto Caco-2 cells, inhibits diarrheagenic Escherichia coli adhesion in a concentration-dependent manner. Since the L. acidophilus does not express ETEC-CFA adhesive factors, it can be postulated that the heat-killed L. acidophilus LB cells inhibit diarrheagenic E. coli attachment by steric hindrance of the human enterocytic ETEC receptors. 相似文献
18.
Hlne Blanch Lawrence G. Wright Gilles Vergnaud Batrice de Gouyon Valrie Lauthier Lee M. Silver Jean Dausset Howard M. Cann Richard S. Spielman 《Genomics》1992,12(4):826-828
Human homologues of mouse t-complex genes have been cloned and localized physically to chromosome 6p or 6q. TCP1, TCP10, and PLG are human homologues of genes located in the proximal portion of the t-complex on mouse chromosome 17. We present here results of genetic mapping of these human t-complex homologues previously localized to 6q25-q27, 6q21-q27, and 6q26-q27, respectively, by physical techniques. TCP1 and PLG do not recombine with each other and are separated from TCP10 by about 15 cM, while the corresponding mouse genes are no more than 4 cM apart. Genetic mapping with markers well localized cytogenetically places TCP1 and PLG proximal to TCP10 and localizes the latter to the cytogenetic band 6q27. It is likely that the organization of human t-complex homologues on 6q is similar to that of t haplotypes rather than that of wildtype murine chromosome 17. 相似文献
19.
20.
Characterization of a frequent polymorphism in the coding sequence of the Tp53 gene in colonic cancer patients and a control population 总被引:2,自引:0,他引:2
Sylviane Olschwang Pierre Laurent-Puig Anne Vassal Rémy-J. Salmon Gilles Thomas 《Human genetics》1991,86(4):369-370
Summary We describe a simple method for characterizing a frequent polymorphism (that subsitutes an arginine for a proline) in the coding sequence of the Tp53 gene in patients with colonic cancer and in a control population. We could find no evidence that this polymorphism is associated with a marked predisposition to colorectal cancer. 相似文献