全文获取类型
收费全文 | 5703篇 |
免费 | 323篇 |
学科分类
生物科学 | 6026篇 |
出版年
2023年 | 20篇 |
2022年 | 43篇 |
2021年 | 87篇 |
2020年 | 58篇 |
2019年 | 64篇 |
2018年 | 94篇 |
2017年 | 99篇 |
2016年 | 142篇 |
2015年 | 208篇 |
2014年 | 215篇 |
2013年 | 361篇 |
2012年 | 375篇 |
2011年 | 395篇 |
2010年 | 244篇 |
2009年 | 210篇 |
2008年 | 372篇 |
2007年 | 327篇 |
2006年 | 350篇 |
2005年 | 327篇 |
2004年 | 270篇 |
2003年 | 257篇 |
2002年 | 234篇 |
2001年 | 118篇 |
2000年 | 115篇 |
1999年 | 106篇 |
1998年 | 50篇 |
1997年 | 66篇 |
1996年 | 38篇 |
1995年 | 25篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 72篇 |
1991年 | 62篇 |
1990年 | 55篇 |
1989年 | 53篇 |
1988年 | 78篇 |
1987年 | 47篇 |
1986年 | 33篇 |
1985年 | 24篇 |
1984年 | 32篇 |
1983年 | 22篇 |
1982年 | 23篇 |
1980年 | 16篇 |
1979年 | 24篇 |
1978年 | 23篇 |
1976年 | 11篇 |
1975年 | 16篇 |
1974年 | 13篇 |
1973年 | 19篇 |
1971年 | 12篇 |
排序方式: 共有6026条查询结果,搜索用时 0 毫秒
1.
Satoko Iwahori Daisuke Kohmon Junya Kobayashi Yuhei Tani Takashi Yugawa Kenshi Komatsu 《Cell cycle (Georgetown, Tex.)》2014,13(3):471-481
Ataxia-telangiectasia mutated (ATM) plays crucial roles in DNA damage responses, especially with regard to DNA double-strand breaks (DSBs). However, it appears that ATM can be activated not only by DSB, but also by some changes in chromatin architecture, suggesting potential ATM function in cell cycle control. Here, we found that ATM is involved in timely degradation of Cdt1, a critical replication licensing factor, during the unperturbed S phase. At least in certain cell types, degradation of p27Kip1 was also impaired by ATM inhibition. The novel ATM function for Cdt1 regulation was dependent on its kinase activity and NBS1. Indeed, we found that ATM is moderately phosphorylated at Ser1981 during the S phase. ATM silencing induced partial reduction in levels of Skp2, a component of SCFSkp2 ubiquitin ligase that controls Cdt1 degradation. Furthermore, Skp2 silencing resulted in Cdt1 stabilization like ATM inhibition. In addition, as reported previously, ATM silencing partially prevented Akt phosphorylation at Ser473, indicative of its activation, and Akt inhibition led to modest stabilization of Cdt1. Therefore, the ATM-Akt-SCFSkp2 pathway may partly contribute to the novel ATM function. Finally, ATM inhibition rendered cells hypersensitive to induction of re-replication, indicating importance for maintenance of genome stability. 相似文献
2.
3.
Synthesis of cytochrome c oxidase in the liver of Rana catesbeiana tadpole treated with griseofulvin
The effect of griseofulvin treatment on the synthesis of cytochrome c oxidase was studied with the liver of the tadpole, Rana catesbeiana. (1) In the liver of tadpole treated with griseofulvin, a ferrochelatase inhibitor, the synthesis of heme a, but not cytochrome c oxidase protein, is inhibited. (2) The apocytochrome c oxidase which is formed in the liver of tadpole treated with griseofulvin is converted to the active holoenzyme by exogenously added heme a. 相似文献
4.
Bacteriocin sensitivity typing according to the method of Traub (Appl. Microbiol. 1971. 21: 837-840) was carried out on 226 clinical isolates of Serratia marcescens obtained from inpatients at Nagasaki University Hospital during the period from January 1976 to December 1978. The isolates were divided into 16 different bacteriocin types, mainly 26, 4, and 9. The distribution of the types suggests that Serratia marcescens infections may be caused by cross infection. Reproducibility of bacteriocin typing and the relationship between serotypes (O-antigen) and bacteriocin types are discussed in regard to the application of this method to the study of nosocomial infections. 相似文献
5.
6.
When pregnant mice were fed biotin-deficient diets, cleft palate occurred more frequently in male fetuses than in female fetuses. Possible underlying mechanisms are speculated on, and some methodological problems in the analysis of sex-related differences in multiparous animals are discussed. 相似文献
7.
8.
Daisuke Hirata Alexei V. Abramov Gennady F. Baryshnikov Ryuichi Masuda 《Biological journal of the Linnean Society. Linnean Society of London》2014,111(3):627-635
Sequence analyses of the complete brown bear, Ursus arctos, mitochondrial DNA (mtDNA) genome have detected scattered single nucleotide polymorphisms (SNPs) that define distinct mtDNA haplogroups in phylogeographical studies. The degraded DNA in historical samples, such as stuffed or excavated specimens, however, is often not suitable for sequence analyses. To address this problem, we developed an amplified product length polymorphism (APLP) analysis for mtDNA‐haplogrouping U. arctos specimens by detecting haplogroup‐specific SNPs. We verified the validity and utility of this method by analysing up to 170‐year‐old skin samples from U. arctos specimens collected widely across continental Eurasia. We detected some of the same haplogroups as those occurring in eastern Hokkaido (Japan) and eastern Alaska in continental Eurasia (the Altai and the Caucasus). Our results show that U. arctos in eastern Hokkaido and eastern Alaska descended from a common ancestor in continental Eurasia, and suggest that U. arctos occupied several refugia in southern Asia during the Last Glacial Maximum. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 627–635. 相似文献
9.
The genetic differentiation among populations of the leaf beetle Chrysolina virgata living in wetlands of Japan was studied based on the sequence data of the mitochondrial cytochrome oxidase subunit I gene region (750 bp). Two distinct lineages of mitochondrial haplotypes were found: one (clade A) consisted of 26 haplotypes distributed over the distribution range of C. virgata between north‐east Honshu and Kyushu, whereas the other (clade B) was monotypic and confined to a small region in north‐east Honshu where it coexisted with clade A. Nested clade analysis for these haplotypes suggested that range expansion and following differentiation due to isolation by distance might have resulted in the present distribution pattern of the haplotypes in clade A. We discuss the evolutionary process leading to the occurrence of two distinct haplotype clades in Japan in terms of repeated colonization from the continent and range expansion and contraction during climatic changes. 相似文献
10.
Early and late periodic patterns of even skipped expression are controlled by distinct regulatory elements that respond to different spatial cues 总被引:14,自引:0,他引:14
We have identified the regulatory sequences required for the periodic expression of the Drosophila pair rule gene even skipped (eve). We find that the gradually changing pattern of periodic eve expression during early embryogenesis is directed by two distinct regulatory programs. Initially, eve expression in individual stripes is established by different regulatory elements, each of which responds to nonperiodic spatial cues provided, at least in part, by the gap genes. Later, coordinate expression of eve in all seven stripes is directed by a single regulatory region that responds to periodic cues provided by primary pair rule genes, including eve itself. As a consequence of this two-step regulatory program, eve functions both in the establishment of the periodic pattern of gene expression and in the subsequent specification of parasegmental boundaries. 相似文献