全文获取类型
收费全文 | 956篇 |
免费 | 50篇 |
出版年
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 20篇 |
2014年 | 34篇 |
2013年 | 52篇 |
2012年 | 67篇 |
2011年 | 55篇 |
2010年 | 32篇 |
2009年 | 34篇 |
2008年 | 52篇 |
2007年 | 62篇 |
2006年 | 52篇 |
2005年 | 75篇 |
2004年 | 70篇 |
2003年 | 71篇 |
2002年 | 54篇 |
2001年 | 16篇 |
2000年 | 21篇 |
1999年 | 19篇 |
1998年 | 8篇 |
1997年 | 12篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 13篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1962年 | 1篇 |
排序方式: 共有1006条查询结果,搜索用时 328 毫秒
171.
Female mate choice by multiple male traits is an important current topic in animal behavior. However, the relative importance
among the multiple cues in female choice is not explored in most cases. Female guppies Poecilia reticulata use both the color saturation of orange spots and the total length of males as mate choice criteria. In the present study,
we used digitally modified video playbacks to examine the relative importance of these two male traits to female mate preferences.
We initially examined the effective difference in the color saturation of orange spots as well as that in total length between
two stimulus male images. Females only showed a strong preference for a bright male image (compared to the dull image) when
the difference in color saturation was large (91% versus 25%). Conversely, females only exhibited a preference for larger
size when they were presented a choice between two relatively small male images (total length 26.0 mm versus 23.0 mm). When
two male images in which both the two traits were modified were presented to females, they prioritized male images possessing
higher color saturation of orange spots, indicating the color saturation of male orange spots to be a more important factor
than the total length in their mate choice. The color saturation of orange spots may convey more reliable information about
the males to the females than their total lengths. These findings imply that females may rank multiple male criteria depending
on relative benefits or costs derived from their mate choice based on each criterion. 相似文献
172.
PtdIns(3, 4, 5)P(3)-dependent Rac exchanger (P-Rex) 1 is a guanine nucleotide exchange factor (GEF) for the small GTPase Rac. P-Rex1 is activated by G protein betagamma subunits (Gbetagamma), and the Gbetagamma-induced activation is inhibited by cAMP-dependent protein kinase A (PKA). However, the details of regulatory mechanism of P-Rex1 remain to be clarified. In the present study, we investigated the mechanism of activation and inhibition of P-Rex1 using various truncated and alanine-substituted mutants and found that the domain-domain interaction of P-Rex1 is important for Gbetagamma-induced activation and PKA-induced inhibition. Immunoprecipitation analysis showed that the second Disheveled/EGL-10/Pleckstrin (DEP) and first PSD-95/Dlg/ZO-1 (PDZ) domains of P-Rex1 associate with the inositol polyphosphate-4-phosphatase (IP4P) domain. Carboxyl-terminal truncation on the IP4P domain or mutations in the protein-binding pocket of the first PDZ domain abolished the association. Analysis of in vitro guanine nucleotide exchange assay, PAK1/2 phosphorylation, and Rac-specific actin reorganization revealed that Gbetagamma could activate a complex of the P-Rex1 mutant lacking the IP4P domain and the isolated IP4P domain as well as full-length P-Rex1. Moreover, PKA phosphorylation prevented the domain-domain interaction and Gbetagamma-binding. These results provide a new insight into the regulation of other Rho-family GEFs and cell responses induced by the heterotrimeric G protein. 相似文献
173.
174.
175.
176.
Takahiro Mukai Jun Suwada Kohei Sano Mayumi Okada Fumihiko Yamamoto Minoru Maeda 《Bioorganic & medicinal chemistry》2009,17(13):4285-4289
From the X-ray crystal structures of Ga–DOTA chelates, we were able to deduce that two free carboxylate groups of the radiogallium–DOTA complex may be utilized for coupling to functional moieties that recognize molecular targets for in vivo imaging without reducing the radiogallium-complex stability. Thus, we designed 2,2′-[4,10-bis(2-{[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]amino}-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,7-diyl]diacetic acid (DOTA-MN2) (7), employing a metronidazole moiety as the recognition site of hypoxic lesions, based on the drug design concept of bifunctional radiopharmaceuticals. Coupling of DOTA-bis(tert-butyl)ester 5 with 1-(2-aminoethyl)-2-methyl-5-nitroimidazole dihydrochloride, followed by deprotection, afforded the required 7 (DOTA-MN2). 67Ga-labeling was carried out by reaction of DOTA-MN2 with 67Ga-citrate. When 67Ga–DOTA-MN2 was incubated in phosphate-buffered saline or mouse plasma, no measurable decomposition occurred over a 24-h period. In biodistribution experiments in NFSa tumor-bearing mice, 67Ga–DOTA-MN2 displayed not only a significant tumor uptake, but also rapid blood clearance and low accumulations in nontarget tissues, resulting in high target-to-nontarget ratios of radioactivity. These results indicate the potential benefits of the drug design of 67Ga–DOTA-MN2. The present findings provide helpful information for the development of radiogallium-labeled radiopharmaceuticals for SPECT and PET studies. 相似文献
177.
178.
179.
180.
Zhang M Ito T Li S Jin J Takeuchi F Lauderdale TL Higashide M Hiramatsu K 《FEMS microbiology letters》2011,323(1):20-28
The genes lukS-PV and lukF-PV for Panton-Valentine leukocidin (PVL) that confers high virulence to Staphylococcus aureus are located on the prophages (PVL phages) which have been classified into group 1 and 2 sfi21-like Siphoviridae. We report novel PVL phages lysogenized in ST59 methicillin-resistant Staphylococcus aureus (MRSA) strains isolated in Japan (JCSC7247) and Taiwan (JCSC5967). The genomes of φ7247PVL and φ5967PVL showed more than 99% identity, and the regions containing the five genes located at both ends of the prophages, int (integrase), hol (holin), ami (amidase), lukS-PV, and lukF-PV, are highly homologous to extant PVL phages. The genes for the structural module are less homologous to these phages, but are highly homologous to non-PVL phages belonging to group 3 Sfi21-like Siphoviridae, for example φN315. Subsequent PCR identification and nucleotide sequencing of an additional 11 Taiwanese ST59 MRSA isolates suggested they all carry the same phage as φ5967PVL, which differed from φ7247PVL by a single base. This study adds evidence to the notion that novel PVL phages would be generated through illegitimate recombination events by acquiring the region at which hol, ami, luk, and int genes would line up upon lytic growth, and suggests that the PVL-positive MRSA clones that have emerged worldwide may carry distinct phages. 相似文献