全文获取类型
收费全文 | 47622篇 |
免费 | 3975篇 |
国内免费 | 9篇 |
出版年
2023年 | 236篇 |
2021年 | 349篇 |
2020年 | 312篇 |
2019年 | 303篇 |
2018年 | 962篇 |
2017年 | 979篇 |
2016年 | 1024篇 |
2015年 | 855篇 |
2014年 | 1025篇 |
2013年 | 1926篇 |
2012年 | 3235篇 |
2011年 | 3650篇 |
2010年 | 1850篇 |
2009年 | 1179篇 |
2008年 | 3041篇 |
2007年 | 3108篇 |
2006年 | 2887篇 |
2005年 | 2588篇 |
2004年 | 2465篇 |
2003年 | 2296篇 |
2002年 | 2266篇 |
2001年 | 1596篇 |
2000年 | 1854篇 |
1999年 | 981篇 |
1998年 | 468篇 |
1997年 | 373篇 |
1996年 | 444篇 |
1995年 | 391篇 |
1994年 | 398篇 |
1993年 | 366篇 |
1992年 | 409篇 |
1991年 | 343篇 |
1990年 | 312篇 |
1989年 | 302篇 |
1988年 | 280篇 |
1987年 | 274篇 |
1986年 | 229篇 |
1985年 | 334篇 |
1984年 | 404篇 |
1983年 | 363篇 |
1982年 | 334篇 |
1981年 | 326篇 |
1980年 | 283篇 |
1979年 | 291篇 |
1978年 | 295篇 |
1977年 | 267篇 |
1976年 | 267篇 |
1975年 | 310篇 |
1974年 | 235篇 |
1973年 | 223篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.
Christoph D. Dahl Nikos K. Logothetis Heinrich H. Bülthoff Christian Wallraven 《Proceedings. Biological sciences / The Royal Society》2010,277(1696):2973-2981
Primates possess the remarkable ability to differentiate faces of group members and to extract relevant information about the individual directly from the face. Recognition of conspecific faces is achieved by means of holistic processing, i.e. the processing of the face as an unparsed, perceptual whole, rather than as the collection of independent features (part-based processing). The most striking example of holistic processing is the Thatcher illusion. Local changes in facial features are hardly noticeable when the whole face is inverted (rotated 180°), but strikingly grotesque when the face is upright. This effect can be explained by a lack of processing capabilities for locally rotated facial features when the face is turned upside down. Recently, a Thatcher illusion was described in the macaque monkey analogous to that known from human investigations. Using a habituation paradigm combined with eye tracking, we address the critical follow-up questions raised in the aforementioned study to show the Thatcher illusion as a function of the observer''s species (humans and macaques), the stimulus'' species (humans and macaques) and the level of perceptual expertise (novice, expert). 相似文献
22.
Strains of paramyxovirus type 1 (PMV-1) have been isolated from diseased racing pigeons in Sweden. One of these isolates was selected for studies of the pathogenicity and contagiousness in chickens. The same isolate was previously found to have a high intravenous pathogenicity index (IVPI) in 6 weeks old chickens. In three experiments it was found that the PMV-1 isolate was very pathogenic for 1 week old chickens but not pathogenic for 120 day old pullets inoculated intranasally and ocularly. Symptoms in the young chickens were similar to those seen in the neurotropic form of Newcastle disease. The mortality was high and the incubation period 5–11 days. The disease easily spread to young chickens kept in contact with diseased birds. The microscopic examination revealed an interstitial nonpurulent pneumonia and a nonpurulent encephalitis in the young chickens. In the pullets the only finding was a mild encephalitis. PMV-1 was recovered from all young chickens but not from the pullets. Both the chickens and the inoculated pullets developed antibodies to PMV-1. 相似文献
23.
24.
Background
Identifying essential genes in bacteria supports to identify potential drug targets and an understanding of minimal requirements for a synthetic cell. However, experimentally assaying the essentiality of their coding genes is resource intensive and not feasible for all bacterial organisms, in particular if they are infective. 相似文献25.
26.
27.
28.
29.
Comparative analysis of the cattle and human genomes: detection of ZOO-FISH and gene mapping-based chromosomal homologies 总被引:6,自引:0,他引:6
Comparative chromosome painting with individual human chromosome-specific libraries (CSLs) on cattle metaphase chromosomes
delineated 46 homologous chromosomal segments between the two species. Continuous arrangement of these segments on individual
cattle chromosomes demonstrates a nearly complete coverage of the bovine karyotype and shows physical boundaries of bovine
chromosomal segments homologous to individual human chromosomes. Alignment of the available comparative gene mapping data
with the homologous segments strongly supports the detected gross homologies between the karyotypes of the two species. In
addition to cattle, four human CSLs were hybridized to sheep metaphase chromosomes also, to further verify the known karyotype
homology within the Bovidae. Besides its application to karyotype evolution research, the comparative knowledge provides for
rapid expansion of the much needed Type I locus-based bovine gene map.
Received: 9 September 1995 / Accepted: 4 December 1995 相似文献
30.