全文获取类型
收费全文 | 44657篇 |
免费 | 4734篇 |
国内免费 | 12篇 |
出版年
2022年 | 321篇 |
2021年 | 557篇 |
2020年 | 378篇 |
2019年 | 460篇 |
2018年 | 594篇 |
2017年 | 558篇 |
2016年 | 965篇 |
2015年 | 1735篇 |
2014年 | 1705篇 |
2013年 | 2235篇 |
2012年 | 2565篇 |
2011年 | 2270篇 |
2010年 | 1579篇 |
2009年 | 1461篇 |
2008年 | 1972篇 |
2007年 | 1970篇 |
2006年 | 1760篇 |
2005年 | 1709篇 |
2004年 | 1627篇 |
2003年 | 1408篇 |
2002年 | 1414篇 |
2001年 | 1371篇 |
2000年 | 1352篇 |
1999年 | 1208篇 |
1998年 | 664篇 |
1997年 | 622篇 |
1996年 | 606篇 |
1995年 | 585篇 |
1994年 | 539篇 |
1993年 | 575篇 |
1992年 | 1145篇 |
1991年 | 858篇 |
1990年 | 897篇 |
1989年 | 858篇 |
1988年 | 747篇 |
1987年 | 682篇 |
1986年 | 698篇 |
1985年 | 775篇 |
1984年 | 608篇 |
1983年 | 468篇 |
1982年 | 389篇 |
1981年 | 346篇 |
1980年 | 296篇 |
1979年 | 429篇 |
1978年 | 373篇 |
1977年 | 284篇 |
1976年 | 263篇 |
1975年 | 235篇 |
1974年 | 324篇 |
1973年 | 288篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
J. P. van der Walt 《Antonie van Leeuwenhoek》1967,33(1):97-99
The yeast species previously described asPichia robertsii v. d. Walt has been transferred to the new genusWingea. The diagnosis for the genus is given. 相似文献
143.
Preferential expression of cellular retinoic acid binding protein in a subpopulation of neural cells in the developing mouse embryo 总被引:2,自引:0,他引:2
Marie-Josée Vaessen Erika Kootwijk Dirk Bootsma Ad Geurts van Kessel Christine Mummery John Hilkens 《Differentiation; research in biological diversity》1989,40(2):99-105
The cellular retinoic acid binding protein is thought to be involved in the retinoic-acid-mediated signal transduction pathway. We have isolated the mouse cellular retinoic acid binding protein cDNA from an embryonal-carcinoma-derived cell line by using differential cDNA cloning strategies. In situ hybridization on sections of mouse embryos of various developmental stages indicated that the cellular retinoic acid binding protein gene, which we localized on mouse chromosome 9, is preferentially expressed in a subpopulation of neurectodermal cells. This restricted expression pattern suggests an important role for cellular retinoic acid binding protein in murine neurogenesis. 相似文献
144.
145.
146.
147.
148.
149.
The role of territoriality was investigated by studying 25 impala rams at a reserve in the Waterberg region of South Africa (23°45′S, 28°23′E). Mean territorial tenure was 67.25 days (range 23–99), with a mean territory size of 21.0 ± 11.27 ha, compared with home ranges of 34.1 ± 9.03 ha for territorial rams and 58.8 ± 33.35 ha for bachelor rams, using the fixed kernel method. Territory boundaries remained constant, whilst the area surrounding important features such as water holes, appears to be neutral in terms of territoriality. The rut, as evidenced from peaks in chasing and roaring, lasted for 2 months from 10 April to 10 June 2001, with intensified behaviour including matings observed from 16 May to 4 June 2001. Territorial rams chase and roar more than bachelors. Flehmen and display behaviours are performed by all rams, whilst fights and other reproductive behaviours are generally rare. Bachelors browse more than territorial rams. Only bachelors spar and allogroom, and orally groom themselves more than territorial rams. 相似文献
150.