全文获取类型
收费全文 | 8120篇 |
免费 | 613篇 |
国内免费 | 3篇 |
出版年
2023年 | 68篇 |
2022年 | 125篇 |
2021年 | 292篇 |
2020年 | 172篇 |
2019年 | 212篇 |
2018年 | 283篇 |
2017年 | 222篇 |
2016年 | 350篇 |
2015年 | 454篇 |
2014年 | 467篇 |
2013年 | 537篇 |
2012年 | 685篇 |
2011年 | 642篇 |
2010年 | 379篇 |
2009年 | 318篇 |
2008年 | 417篇 |
2007年 | 428篇 |
2006年 | 408篇 |
2005年 | 307篇 |
2004年 | 334篇 |
2003年 | 303篇 |
2002年 | 260篇 |
2001年 | 100篇 |
2000年 | 87篇 |
1999年 | 95篇 |
1998年 | 74篇 |
1997年 | 65篇 |
1996年 | 48篇 |
1995年 | 55篇 |
1994年 | 45篇 |
1993年 | 21篇 |
1992年 | 45篇 |
1991年 | 41篇 |
1990年 | 50篇 |
1989年 | 32篇 |
1988年 | 29篇 |
1987年 | 24篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 20篇 |
1982年 | 10篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1975年 | 20篇 |
1974年 | 10篇 |
1973年 | 9篇 |
排序方式: 共有8736条查询结果,搜索用时 882 毫秒
1.
2.
Sacramento Doralice Rodrigues Coelho Rosalie Reed Rodrigues Wigg Márcia Dutra Toledo Luna Linhares Luiz Fernando de Matos dos Santos Marta Gonçalves Azevedo Soares Semêdo Luzia Teixeira de Ribeiro da Silva Antonio Jorge 《World journal of microbiology & biotechnology》2004,20(3):225-229
A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial
activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions,
obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic
fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type
1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
4.
Elizabeth Storer Scholl Antonella Pirone Daniel H Cox R Keith Duncan Michele H Jacob 《Channels (Austin, Tex.)》2014,8(1):62-75
Small conductance Ca2+-sensitive potassium (SK2) channels are voltage-independent, Ca2+-activated ion channels that conduct potassium cations and thereby modulate the intrinsic excitability and synaptic transmission of neurons and sensory hair cells. In the cochlea, SK2 channels are functionally coupled to the highly Ca2+ permeant α9/10-nicotinic acetylcholine receptors (nAChRs) at olivocochlear postsynaptic sites. SK2 activation leads to outer hair cell hyperpolarization and frequency-selective suppression of afferent sound transmission. These inhibitory responses are essential for normal regulation of sound sensitivity, frequency selectivity, and suppression of background noise. However, little is known about the molecular interactions of these key functional channels. Here we show that SK2 channels co-precipitate with α9/10-nAChRs and with the actin-binding protein α-actinin-1. SK2 alternative splicing, resulting in a 3 amino acid insertion in the intracellular 3′ terminus, modulates these interactions. Further, relative abundance of the SK2 splice variants changes during developmental stages of synapse maturation in both the avian cochlea and the mammalian forebrain. Using heterologous cell expression to separately study the 2 distinct isoforms, we show that the variants differ in protein interactions and surface expression levels, and that Ca2+ and Ca2+-bound calmodulin differentially regulate their protein interactions. Our findings suggest that the SK2 isoforms may be distinctly modulated by activity-induced Ca2+ influx. Alternative splicing of SK2 may serve as a novel mechanism to differentially regulate the maturation and function of olivocochlear and neuronal synapses. 相似文献
5.
6.
Daneen Schaeffer Filipa Pereira Reis Sean J. Johnson Cec��lia Maria Arraiano Ambro van Hoof 《Nucleic acids research》2012,40(18):9298-9307
The 10-subunit RNA exosome is involved in a large number of diverse RNA processing and degradation events in eukaryotes. These reactions are carried out by the single catalytic subunit, Rrp44p/Dis3p, which is composed of three parts that are conserved throughout eukaryotes. The exosome is named for the 3′ to 5′ exoribonuclease activity provided by a large C-terminal region of the Rrp44p subunit that resembles other exoribonucleases. Rrp44p also contains an endoribonuclease domain. Finally, the very N-terminus of Rrp44p contains three Cys residues (CR3 motif) that are conserved in many eukaryotes but have no known function. These three conserved Cys residues cluster with a previously unrecognized conserved His residue in what resembles a metal-ion-binding site. Genetic and biochemical data show that this CR3 motif affects both endo- and exonuclease activity in vivo and both the nuclear and cytoplasmic exosome, as well as the ability of Rrp44p to associate with the other exosome subunits. These data provide the first direct evidence that the exosome-Rrp44p interaction is functionally important and also provides a molecular explanation for the functional defects when the conserved Cys residues are mutated. 相似文献
7.
Plant chloroplasts are not only the main cellular location for storage of elemental iron (Fe), but also the main site for Fe, which is incorporated into chlorophyll, haem and the photosynthetic machinery. How plants measure internal Fe levels is unknown. We describe here a new Fe‐dependent response, a change in the period of the circadian clock. In Arabidopsis, the period lengthens when Fe becomes limiting, and gradually shortens as external Fe levels increase. Etiolated seedlings or light‐grown plants treated with plastid translation inhibitors do not respond to changes in Fe supply, pointing to developed chloroplasts as central hubs for circadian Fe sensing. Phytochrome‐deficient mutants maintain a short period even under Fe deficiency, stressing the role of early light signalling in coupling the clock to Fe responses. Further mutant and pharmacological analyses suggest that known players in plastid‐to‐nucleus signalling do not directly participate in Fe sensing. We propose that the sensor governing circadian Fe responses defines a new retrograde pathway that involves a plastid‐encoded protein that depends on phytochromes and the functional state of chloroplasts. 相似文献
8.
9.