全文获取类型
收费全文 | 4372篇 |
免费 | 287篇 |
国内免费 | 2篇 |
专业分类
4661篇 |
出版年
2023年 | 22篇 |
2022年 | 58篇 |
2021年 | 113篇 |
2020年 | 87篇 |
2019年 | 92篇 |
2018年 | 121篇 |
2017年 | 124篇 |
2016年 | 172篇 |
2015年 | 234篇 |
2014年 | 237篇 |
2013年 | 331篇 |
2012年 | 378篇 |
2011年 | 336篇 |
2010年 | 212篇 |
2009年 | 186篇 |
2008年 | 249篇 |
2007年 | 243篇 |
2006年 | 209篇 |
2005年 | 197篇 |
2004年 | 170篇 |
2003年 | 191篇 |
2002年 | 165篇 |
2001年 | 52篇 |
2000年 | 35篇 |
1999年 | 39篇 |
1998年 | 43篇 |
1997年 | 26篇 |
1996年 | 26篇 |
1995年 | 23篇 |
1994年 | 21篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 26篇 |
1990年 | 25篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 22篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1973年 | 3篇 |
1964年 | 4篇 |
排序方式: 共有4661条查询结果,搜索用时 15 毫秒
31.
Douglas E Bassett Jr Munira A Basrai Carla Connelly Katherine M Hyland Katsumi Kitagawa Melanie L Mayer Dwight M Morrow Andrew M Page Vicente A Resto Robert V Skibbens Philip Hieter 《Current opinion in genetics & development》1996,6(6):763-766
The completion of the genome sequence of the budding yeast Saccharomyces cerevisiae marks the dawn of an exciting new era in eukaryotic biology that will bring with it a new understanding of yeast, other model organisms, and human beings. This body of sequence data benefits yeast researchers by obviating the need for piecemeal sequencing of genes, and allows researchers working with other organisms to tap into experimental advantages inherent in the yeast system and learn from functionally characterized yeast gene products which are their proteins of interest. In addition, the yeast post-genome sequence era is serving as a testing ground for powerful new technologies, and proven experimental approaches are being applied for the first time in a comprehensive fashion on a complete eukaryotic gene repertoire. 相似文献
32.
33.
Nuclear counterparts of the cytoplasmic mitochondrial 12S rRNA gene: A problem of ancient DNA and molecular phylogenies 总被引:10,自引:0,他引:10
Antoinette C. van der Kuyl Carla L. Kuiken John T. Dekker Wladimir R. K. Perizonius Jaap Goudsmit 《Journal of molecular evolution》1995,40(6):652-657
Monkey mummy bones and teeth originating from the North Saqqara Baboon Galleries (Egypt), soft tissue from a mummified baboon in a museum collection, and nineteenth/twentieth-century skin fragments from mangabeys were used for DNA extraction and PCR amplification of part of the mitochondrial 12S rRNA gene. Sequences aligning with the 12S rRNA gene were recovered but were only distantly related to contemporary monkey mitochondrial 12S rRNA sequences. However, many of these sequences were identical or closely related to human nuclear DNA sequences resembling mitochondrial 12S rRNA (isolated from a cell line depleted in mitochondria) and therefore have to be considered contamination. Subsequently in a separate study we were able to recover genuine mitochondrial 12S rRNA sequences from many extant species of nonhuman Old World primates and sequences closely resembling the human nuclear integrations. Analysis of all sequences by the neighbor-joining (NJ) method indicated that mitochondrial DNA sequences and their nuclear counterparts can be divided into two distinct clusters. One cluster contained all temporary cytoplasmic mitochondrial DNA sequences and approximately half of the monkey nuclear mitochondriallike sequences. A second cluster contained most human nuclear sequences and the other half of monkey nuclear sequences with a separate branch leading to human and gorilla mitochondrial and nuclear sequences. Sequences recovered from ancient materials were equally divided between the two clusters. These results constitute a warning for when working with ancient DNA or performing phylogenetic analysis using mitochondrial DNA as a target sequence: Nuclear counterparts of mitochondrial genes may lead to faulty interpretation of results.Correspondence to: A.C. van der Kuyl 相似文献
34.
35.
Characterization of a Small Family (CAIII) of Microsatellite-Containing Sequences with X-Y Homology 总被引:4,自引:0,他引:4
Patrizia Malaspina Bianca Maria Ciminelli Luigi Viggiano Carla Jodice Fulvio Cruciani Piero Santolamazza Daniele Sellitto Rosaria Scozzari Luciano Terrenato Mariano Rocchi Andrea Novelletto 《Journal of molecular evolution》1997,44(6):652-659
Four X-linked loci showing homology with a previously described Y-linked polymorphic locus (DYS413) were identified and characterized.
By fluorescent in situ hybridization (FISH), somatic cell hybrids, and YAC screening, the X-linked members of this small family
of sequences (CAIII) all map in Xp22, while the Y members map in Yq11. These loci contribute to the overall similarity of
the two genomic regions. All of the CAIII loci contain an internal microsatellite of the (CA)n type. The microsatellites display extensive length polymorphism in two of the X-linked members as well as in the Y members.
In addition, common sequence variants are found in the portions flanking the microsatellites in two of the X-linked members.
Our results indicate that, during the evolution of this family, length variation on the Y chromosome was accumulated at a
rate not slower than that on the X chromosome. Finally, these sequences represent a model system with which to analyze human
populations for similar X- and Y-linked polymorphisms.
Received: 29 July 1996 / Accepted: 15 January 1997 相似文献
36.
A three-dimensional structure of the NAD-dependent D -lactate dehydrogenase of Lactobacillus bulgaricus is modeled using the structure of the formate dehydrogenase of Pseudomonas sp. as template. Both sequences share only 22% of identical residues. Regions for knowledge-based modeling are defined from the structurally conserved regions predicted by multiple alignment of a set of related protein sequences with low homology. The model of the D -LDH subunit shows, as for the formate dehydrogenase, an α/β structure, with a catalytic domain and a coenzyme binding domain. It points out the catalytic histidine (His-296) and supports the hypothetical catalytic mechanism. It also suggests that the other residues involved in the active site are Arg-235, possibly involved in the binding of the carboxyl group of the pyruvate, and Phe-299, a candidate for stabilizing the methyl group of the substrate. © 1995 Wiley-Liss, Inc. 相似文献
37.
38.
39.
Carol M. Warner Ruth M. Graves Carla M. Tollefson Mary Jo F. Schmerr Thomas J. Stephens Carmen F. Merryman Paul H. Maurer 《Immunogenetics》1976,3(1):337-348
The immune response of allophenic mice of type C57BL/6(A × SJL) F1 to GL administered in complete Freund's adjuvant was tested. Control mice of the three strains C57BL/6, A, and SJL are all nonresponders to this antigen. However, the F1 generations of C57BL/6 × A, C57BL/6 × SJL, and A × SJL were all responders to the antigen, so that the complementarity of at least two genes is confirmed. The allophenic mice showed no further complementation beyond the F1 generation, a result which may argue against the possibility that more than two genes control the response to GL in these mouse strains. Characterization of the allophenic mice over several months showed that they exhibit chimeric drift, both in their coat color and in peripheral white blood cell population. There is no apparent correlation of coat color to the lymphocyte composition of the mice at any one time. The mice are true chimeras, since killing of the two populations of white blood cells with two different anti-H-2 sera produced a 100 percent killing. The immune response of individual allophenic mice to GL showed a good correlation to the number of A × SJL lympho-cytes in the animal.Abbreviations used in this paper are GL
an amino acid polymer of 57 %l-glutamic acid, 38%l-lysine, and 5%l-phenylalanine
- GLT15
an amino acid polymer ofl-glutamic acid,l-lysine, and 15 %l-tyrosine
- (T,G)-A-L
an amino acid polymer having a polylysine backbone with side chains of polyd-l-alanine, terminating in short sequences of tyrosine and glutamic acid
- GAT10
an amino acid polymer of 60%l-glutamic acid, 30%l-alanine, and 10%l-tyrosine
- GLA5
an amino acid polymer of 57%l-glutamic acid, 38%l-lysine, and 5%l-alanine
- DNP
2,4 dinitrophenyl
- BGG
bovine gamma globulin
- FCS
fetal calf serum
- PWBC
peripheral white blood cell
- SWBC
spleen white blood cell
- T cell
thymus-derived lymphocyte
- B cell
bone marrow-derived lymphocyte 相似文献
40.
Several methods were described for visualization of proteolytic activity on electrophoregrams obtained with agar, agarose, starch, or acrylamide gels as supporting media. In most of these reports casein or hemoglobin were used as nonspecific substrates (1–3). Recently, colorimetric assays for trypsin, using α-benzoyl-d,l-arginine-p-nitroanilide (4), and for subtilisin, using Z-glycyl-glycyl-l-leucine-p-nitroanilide (5) were introduced for the localization of these proteases after acetate celulose and acrylamide gel electrophoresis. No convenient and simple methods were in practice for detection of leucineaminopeptidase (3), although this enzyme was assayed in solution with specific chromogenic substrates such as l-leucine-p-nitroanilide or l-leucine-β-naphtylamide (6,7).The present report describes the use of p-nitroanilide substrate-l-leucine-p-nitroanilide for detection of leucineaminopeptidase activity after acrylamide gel electrophoresis. The method allows a rapid and sensitive localization of leucineaminopeptidases. 相似文献