全文获取类型
收费全文 | 3587篇 |
免费 | 204篇 |
出版年
2023年 | 9篇 |
2022年 | 6篇 |
2021年 | 50篇 |
2020年 | 24篇 |
2019年 | 21篇 |
2018年 | 56篇 |
2017年 | 46篇 |
2016年 | 70篇 |
2015年 | 140篇 |
2014年 | 162篇 |
2013年 | 236篇 |
2012年 | 261篇 |
2011年 | 272篇 |
2010年 | 156篇 |
2009年 | 162篇 |
2008年 | 245篇 |
2007年 | 270篇 |
2006年 | 241篇 |
2005年 | 213篇 |
2004年 | 227篇 |
2003年 | 231篇 |
2002年 | 225篇 |
2001年 | 26篇 |
2000年 | 29篇 |
1999年 | 35篇 |
1998年 | 38篇 |
1997年 | 37篇 |
1996年 | 23篇 |
1995年 | 35篇 |
1994年 | 23篇 |
1993年 | 22篇 |
1992年 | 27篇 |
1991年 | 19篇 |
1990年 | 33篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1959年 | 1篇 |
1958年 | 2篇 |
排序方式: 共有3791条查询结果,搜索用时 15 毫秒
1.
2.
3.
A new snake-eel,Apterichtus keramanus, is described on the basis of a single 276-mm TL specimen trawled from the coast of Kerama Islands, Okinawa Prefecture, Japan.
The species is unique in the genus in having the posterior nostril opening entirely inside the mouth and a dark band running
from the anteroventral margin of the eye to the upper lip. 相似文献
4.
Atsushi Takeda Masatoshi Nakamura Hiroaki Fujii Chihiro Uematsu Tatsuya Minamino Paul A. Adlard Ashley I. Bush Haruna Tamano 《PloS one》2014,9(12)
We examined an idea that short-term cognition is transiently affected by a state of confusion in Zn2+ transport system due to a local increase in amyloid-β (Aβ) concentration. A single injection of Aβ (25 pmol) into the dentate gyrus affected dentate gyrus long-term potentiation (LTP) 1 h after the injection, but not 4 h after the injection. Simultaneously, 1-h memory of object recognition was affected when the training was performed 1 h after the injection, but not 4 h after the injection. Aβ-mediated impairments of LTP and memory were rescued in the presence of zinc chelators, suggesting that Zn2+ is involved in Aβ action. When Aβ was injected into the dentate gyrus, intracellular Zn2+ levels were increased only in the injected area in the dentate gyrus, suggesting that Aβ induces the influx of Zn2+ into cells in the injected area. When Aβ was added to hippocampal slices, Aβ did not increase intracellular Zn2+ levels in the dentate granule cell layer in ACSF without Zn2+, but in ACSF containing Zn2+. The increase in intracellular Zn2+ levels was inhibited in the presence of CaEDTA, an extracellular zinc chelator, but not in the presence of CNQX, an AMPA receptor antagonist. The present study indicates that Aβ-mediated Zn2+ influx into dentate granule cells, which may occur without AMPA receptor activation, transiently induces a short-term cognitive deficit. Extracellular Zn2+ may play a key role for transiently Aβ-induced cognition deficits. 相似文献
5.
6.
7.
One of the water stress-specific cDNA clones of rice characterisedpreviously, wsi18, was selected for further study. The wsi18gene can be induced by water stress conditions such as mannitol,NaCl, and dryness, but not by ABA, cold, or heat. A genomicclone for wsi18, pwsi18, contained about 1.7 kbp of the 5' upstreamsequence, two introns, and the full coding sequence. The 5'-upstreamsequence of pwsi18 contained putative cis-acting elements, namelyan ABA-responsive element (ABRE), three G-boxes, three E-boxes,a MEF-2 sequence, four direct and two inverted repeats, andfour sequences similar to DRE, which is involved in the dehydrationresponse of Arabi-dopsis genes. The gusA reporter gene underthe control of the pwsi18 promoter showed transient expressionin response to water stress. Deletion of the downstream DRE-likesequence between the distal G-boxes-2 and -3 resulted in ratherlow GUS expression. (Received March 27, 1997; Accepted November 5, 1997) 相似文献
8.
Takahiro Ishii Tatsufumi Okino Yosuke Mino Hiroaki Tamiya Fuyuhiko Matsuda 《Plant Growth Regulation》2007,52(2):131-139
Starfish waste has been shown to be an effective compost material not only in the promotion of plant growth but also in terms
of having insecticidal activity. In the present study, plant growth regulation by chemicals from starfish was examined. The
aqueous fraction from a hot water extract of the starfish Asterias amurensis Lütken showed plant-growth activity, while the aqueous fraction from a methanol extract inhibited growth of Brassica campestris. The lipophilic fraction from the methanol extract also exhibited a plant growth-promoting effect. The active components
from each extract were identified. Asterubine from the hot water extract promoted plant growth. A ceramide from the lipophilic
fraction showed root growth promoting effect, and three glucocerebrosides had promotive effects on the entire plant. Asterosaponins
were identified as the main growth inhibitors in the aqueous fraction of the methanol extract. These active compounds from
starfish waste could be analyzed as potential plant growth regulators in agricultural applications in the future. 相似文献
9.
Gram‐negative bacteria cause many types of infections in animals from fish and shrimps to humans. Bacteria use Type III secretion systems (TTSSs) to translocate their toxins directly into eukaryotic cells. The V‐antigen is a multifunctional protein required for the TTSS in Yersinia and Pseudomonas aeruginosa. V‐antigen vaccines and anti‐V‐antigen antisera confer protection against Yersinia or P. aeruginosa infections in animal models. The V‐antigen forms a pentameric cap structure at the tip of the Type III secretory needle; this structure, which has evolved from the bacterial flagellar cap structure, is indispensable for toxin translocation. Various pathogenic gram‐negative bacteria such as Photorhabdus luminescens, Vibrio spp., and Aeromonas spp. encode homologs of the V‐antigen. Because the V‐antigens of pathogenic gram‐negative bacteria play a key role in toxin translocation, they are potential therapeutic targets for combatting bacterial virulence. In the USA and Europe, these vaccines and specific antibodies against V‐antigens are in clinical trials investigating the treatment of Yersinia or P. aeruginosa infections. Pathogenic gram‐negative bacteria are of great interest because of their ability to infect fish and shrimp farms, their potential for exploitation in biological terrorism attacks, and their ability to cause opportunistic infections in humans. Thus, elucidation of the roles of the V‐antigen in the TTSS and mechanisms by which these functions can be blocked is critical to facilitating the development of improved anti‐V‐antigen strategies. 相似文献
10.
Yukako Ishigaki Hiroyuki Tanaka Hiroaki Akama Toshiki Ogara Koji Uwai Kiyotaka Tokuraku 《PloS one》2013,8(8)
The aggregation of amyloid β protein (Aβ) is a key step in the pathogenesis of Alzheimer’s disease (AD), and therefore inhibitory substances for Aβ aggregation may have preventive and/or therapeutic potential for AD. Here we report a novel microliter-scale high-throughput screening system for Aβ aggregation inhibitors based on fluorescence microscopy-imaging technology with quantum-dot Nanoprobes. This screening system could be analyzed with a 5-µl sample volume when a 1536-well plate was used, and the inhibitory activity could be estimated as half-maximal effective concentrations (EC50). We attempted to comprehensively screen Aβ aggregation inhibitors from 52 spices using this system to assess whether this novel screening system is actually useful for screening inhibitors. Screening results indicate that approximately 90% of the ethanolic extracts from the spices showed inhibitory activity for Aβ aggregation. Interestingly, spices belonging to the Lamiaceae, the mint family, showed significantly higher activity than the average of tested spices. Furthermore, we tried to isolate the main inhibitory compound from
Satureja
hortensis
, summer savory, a member of the Lamiaceae, using this system, and revealed that the main active compound was rosmarinic acid. These results demonstrate that this novel microliter-scale high-throughput screening system could be applied to the actual screening of Aβ aggregation inhibitors. Since this system can analyze at a microscopic scale, it is likely that further minimization of the system would easily be possible such as protein microarray technology. 相似文献