全文获取类型
收费全文 | 2070篇 |
免费 | 59篇 |
国内免费 | 74篇 |
专业分类
2203篇 |
出版年
2023年 | 22篇 |
2022年 | 18篇 |
2021年 | 31篇 |
2020年 | 28篇 |
2019年 | 36篇 |
2018年 | 44篇 |
2017年 | 21篇 |
2016年 | 37篇 |
2015年 | 37篇 |
2014年 | 122篇 |
2013年 | 140篇 |
2012年 | 94篇 |
2011年 | 68篇 |
2010年 | 75篇 |
2009年 | 70篇 |
2008年 | 111篇 |
2007年 | 108篇 |
2006年 | 99篇 |
2005年 | 92篇 |
2004年 | 85篇 |
2003年 | 85篇 |
2002年 | 75篇 |
2001年 | 67篇 |
2000年 | 66篇 |
1999年 | 64篇 |
1998年 | 50篇 |
1997年 | 45篇 |
1996年 | 40篇 |
1995年 | 39篇 |
1994年 | 47篇 |
1993年 | 26篇 |
1992年 | 36篇 |
1991年 | 31篇 |
1990年 | 18篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 23篇 |
1984年 | 20篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 6篇 |
1980年 | 13篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1974年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有2203条查询结果,搜索用时 0 毫秒
21.
Rabbits were immunised againstEscherichia coli ribosomes and the partially purified immunoglobulin G fraction had maximum ability to precipitate the ribosomes as well as
the extracted ribosomal proteins. By digestion of immuno-globulin G with papain, monovalent Fab fragments were produced. The
70 S ribosome and its subunits (50 S and 30 S) were separately treated with Fab and then tested in the kinetic assay of degradation
of ribosomes by ribonuclease I at various Mg2+ concentrations. Treated ribosomes and their subunits were degraded at faster rates than the nontreated ones; the rates in
both the control and the treated cases were dependent on the concentration of Mg2+. These results indicate the unfolding of the structure of the ribosome on treatment with antibody fragments, which may be
due to the weakening of the interaction between rRNAs and ribosomal proteins. 相似文献
22.
23.
In the early stages of infection, gaining control of the cellular protein synthesis machinery including its ribosomes is the ultimate combat objective for a virus. To successfully replicate, viruses unequivocally need to usurp and redeploy this machinery for translation of their own mRNA. In response, the host triggers global shutdown of translation while paradoxically allowing swift synthesis of antiviral proteins as a strategy to limit collateral damage. This fundamental conflict at the level of translational control defines the outcome of infection. As part of this special issue on molecular mechanisms of early virus–host cell interactions, we review the current state of knowledge regarding translational control during viral infection with specific emphasis on protein kinase RNA-activated and mammalian target of rapamycin-mediated mechanisms. We also describe recent technological advances that will allow unprecedented insight into how viruses and host cells battle for ribosomes. 相似文献
24.
The phylogenetic relatedness of Issatchenkia spp. was estimated from partial rRNA sequences in two regions of the large subunit and one region of the small subunit. I. terricola was the most divergent species of the genus, differing from other members by 18% nucleotide differences in the highly variable 25S-635 region. These data indicate Issatchenkia to be the most divergent ascomycetous yeast genus presently known. 相似文献
25.
Riboprinting was used to determine the relationships among strains belonging to 15 species of the genusKluyveromyces. The small subunit ribosomal RNA gene (SSU rDNA) was amplified using the Polymerase Chain Reaction (PCR) and subjected to a battery of nine restriction enzymes. Similarity coefficients between strains were calculated based on shared and unique restriction fragments. Cluster analysis revealed three major groups that generally correlated with previously reported relationships based on other molecular data. Variations in SSU rDNA restriction fragments may be used for differentiation of theKluyveromyces strains included in this study.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged. 相似文献
26.
27.
Kraftionema allantoideum,a new genus and family of Ulotrichales (Chlorophyta) adapted for survival in high intertidal pools 下载免费PDF全文
The marine, sand‐dwelling green alga Kraftionema allantoideum gen. et sp. nov. is described from clonal cultures established from samples collected in coastal, high intertidal pools from south eastern Australia. The species forms microscopic, uniseriate, unbranched, 6–8 μm wide filaments surrounded by a gelatinous capsule of varying thickness. Filaments are twisted, knotted, and variable in length from 4 to 50 cells in field samples but straighter and much longer in culture, up to 1.5 mm in length. Cell division occurs in several planes, resulting in daughter cells of varying shape, from square to rectangular to triangular, giving rise to gnarled filaments. Mature cells become allantoid, elongate with rounded ends, before dividing one time to form bicells comprised of two domed cells. Adjacent bicells separate from one another and mature filaments appeared as a string of loosely arranged sausages. A massive, single, banded chloroplast covered 3/4 of the wall circumference, and contained a single large pyrenoid encased in a starch envelope that measures 1.5–2.5 μm. Filaments were not adhesive nor did they produce specialized adhesive cells or structures. Reproduction was by fragmentation with all cells capable of producing a new filament. No motile or reproductive cells were observed. Filaments in culture grew equally well in freshwater or marine media, as well as at high salinity, and cells quickly recovered from desiccation. Phylogenetic analysis based on the nuclear‐encoded small subunit ribosomal RNA (18S) shows the early branching nature of the Kraftionema lineage among Ulotrichales, warranting its recognition as a family (Kraftionemaceae). 相似文献
28.
Nucleotide sequence of the potato rDNA intergenic spacer 总被引:3,自引:0,他引:3
29.
30.
Masih EI Slezack-Deschaumes S Marmaras I Barka EA Vernet G Charpentier C Adholeya A Paul B 《FEMS microbiology letters》2001,202(2):227-232
Pichia membranifaciens strain FY-101, isolated from grape skins, was found to be antagonistic to Botrytis cinerea, the causal organism of the grey mould disease of the grapevine. When grown together on solid as well as liquid media, the yeast brings about the inhibition of this parasitic fungus, coagulation and leakage of its cytoplasm, and suppression of its ability to produce the characteristic grey mould symptoms on the grapevine plantlets. In vitro experiments confirm that this yeast can be used as a biological control organism against B. cinerea. An account of the molecular characterisation of P. membranifaciens (complete sequence of the ITS region of its ribosomal DNA, GenBank accession No. AF 270935), as well as the interaction between B. cinerea and the yeast, are given here. 相似文献