全文获取类型
收费全文 | 199311篇 |
免费 | 10208篇 |
国内免费 | 873篇 |
出版年
2021年 | 1453篇 |
2020年 | 902篇 |
2019年 | 1110篇 |
2018年 | 12958篇 |
2017年 | 11696篇 |
2016年 | 9409篇 |
2015年 | 4260篇 |
2014年 | 4463篇 |
2013年 | 5749篇 |
2012年 | 11119篇 |
2011年 | 19456篇 |
2010年 | 16221篇 |
2009年 | 12170篇 |
2008年 | 15393篇 |
2007年 | 17187篇 |
2006年 | 6336篇 |
2005年 | 6226篇 |
2004年 | 6604篇 |
2003年 | 6436篇 |
2002年 | 5882篇 |
2001年 | 1411篇 |
2000年 | 1011篇 |
1999年 | 1320篇 |
1998年 | 1575篇 |
1997年 | 1177篇 |
1996年 | 1040篇 |
1995年 | 981篇 |
1994年 | 941篇 |
1993年 | 1027篇 |
1992年 | 1017篇 |
1991年 | 892篇 |
1990年 | 836篇 |
1989年 | 812篇 |
1988年 | 810篇 |
1987年 | 755篇 |
1986年 | 779篇 |
1985年 | 856篇 |
1984年 | 1057篇 |
1983年 | 921篇 |
1982年 | 1125篇 |
1981年 | 1178篇 |
1980年 | 1038篇 |
1979年 | 714篇 |
1978年 | 778篇 |
1977年 | 724篇 |
1976年 | 698篇 |
1974年 | 660篇 |
1973年 | 612篇 |
1972年 | 658篇 |
1971年 | 621篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Grape thaumatin-like proteins (TLPs) play roles in plant-pathogen interactions and can cause protein haze in white wine unless removed prior to bottling. Different isoforms of TLPs have different hazing potential and aggregation behavior. Here we present the elucidation of the molecular structures of three grape TLPs that display different hazing potential. The three TLPs have very similar structures despite belonging to two different classes (F2/4JRU is a thaumatin-like protein while I/4L5H and H2/4MBT are VVTL1), and having different unfolding temperatures (56 vs. 62°C), with protein F2/4JRU being heat unstable and forming haze, while I/4L5H does not. These differences in properties are attributable to the conformation of a single loop and the amino acid composition of its flanking regions. 相似文献
12.
Lincoln D Stein 《Genome biology》2010,11(5):207
With DNA sequencing now getting cheaper more quickly than data storage or computation, the time may have come for genome informatics
to migrate to the cloud. 相似文献
13.
Puerto Rican populations of two species of sea anemones (Bunodosoma cavernata and B. granulifera) which had previously been considered one were assayed electrophoretically for enzymes encoded by 12 loci. The two species shared no common allozymes at 6 of the 12 loci. Genetic distance and identity values based on these allozymes were computed for the Puerto Rican populations and for B. cavernata from Florida and B. granulifera from Panama. The Puerto Rican populations of both species had much higher genetic identities for their geographically distant conspecifics than for each other. These results indicate that the two species are reproductively isolated and should be considered as separate valid species. Average heterozygosities are presented which are the first published for coelenterate species. 相似文献
14.
Rice fields are an alternative habitat for waterbirds and provide food and shelter for many avian species, but there is a lack of information about how the use of rice fields translates into population level effects. The aim of this study was to test the relationship between the use of rice fields by European waterbirds and trends in their populations. We tested this relationship during the autumn migration season and during the breeding season. Based on counts conducted over the last 23 years in natural marshes and areas of rice fields in Doñana (SW Spain), an index of rice field use was constructed for 76 bird species, which was then compared to these species’ European population trends obtained from the literature. A positive relationship was found between waterbird population trends and the use of rice fields during autumn migration season. Our study suggests that changes in the Common Agriculture Policy in Europe leading to reductions in areas of rice cultivation may have important effects on waterbirds. The restoration of former marsh areas and the maintenance of rice cultivation would seem to be more environmentally friendly approaches than the use of these areas to grow alternative crops or solar farms. 相似文献
15.
16.
17.
18.
19.
Robert S. Steneck 《Current biology : CB》2009,19(3):R117-R119
20.