全文获取类型
| 收费全文 | 11510篇 |
| 免费 | 3778篇 |
专业分类
| 林业 | 258篇 |
| 农学 | 498篇 |
| 基础科学 | 7篇 |
| 1632篇 | |
| 综合类 | 577篇 |
| 农作物 | 162篇 |
| 水产渔业 | 2609篇 |
| 畜牧兽医 | 8146篇 |
| 园艺 | 46篇 |
| 植物保护 | 1353篇 |
出版年
| 2023年 | 75篇 |
| 2022年 | 29篇 |
| 2021年 | 162篇 |
| 2020年 | 609篇 |
| 2019年 | 1074篇 |
| 2018年 | 975篇 |
| 2017年 | 1015篇 |
| 2016年 | 989篇 |
| 2015年 | 907篇 |
| 2014年 | 935篇 |
| 2013年 | 1156篇 |
| 2012年 | 616篇 |
| 2011年 | 702篇 |
| 2010年 | 718篇 |
| 2009年 | 391篇 |
| 2008年 | 415篇 |
| 2007年 | 243篇 |
| 2006年 | 271篇 |
| 2005年 | 229篇 |
| 2004年 | 275篇 |
| 2003年 | 273篇 |
| 2002年 | 264篇 |
| 2001年 | 181篇 |
| 2000年 | 222篇 |
| 1999年 | 123篇 |
| 1998年 | 126篇 |
| 1997年 | 138篇 |
| 1996年 | 106篇 |
| 1995年 | 103篇 |
| 1994年 | 115篇 |
| 1993年 | 154篇 |
| 1992年 | 156篇 |
| 1991年 | 139篇 |
| 1990年 | 153篇 |
| 1989年 | 135篇 |
| 1988年 | 118篇 |
| 1987年 | 117篇 |
| 1986年 | 91篇 |
| 1985年 | 89篇 |
| 1984年 | 64篇 |
| 1983年 | 79篇 |
| 1982年 | 42篇 |
| 1981年 | 32篇 |
| 1979年 | 39篇 |
| 1978年 | 29篇 |
| 1975年 | 28篇 |
| 1972年 | 29篇 |
| 1971年 | 37篇 |
| 1970年 | 30篇 |
| 1969年 | 30篇 |
排序方式： 共有10000条查询结果，搜索用时 46 毫秒
991.
Mitton-Fry RM Anderson EM Hughes TR Lundblad V Wuttke DS 《Science (New York, N.Y.)》2002,296(5565):145-147
The essential Cdc13 protein in the yeast Saccharomyces cerevisiae is a single-stranded telomeric DNA binding protein required for chromosome end protection and telomere replication. Here we report the solution structure of the Cdc13 DNA binding domain in complex with telomeric DNA. The structure reveals the use of a single OB (oligonucleotide/oligosaccharide binding) fold augmented by an unusually large loop for DNA recognition. This OB fold is structurally similar to OB folds found in the ciliated protozoan telomere end-binding protein, although no sequence similarity is apparent between them. The common usage of an OB fold for telomeric DNA interaction demonstrates conservation of end-protection mechanisms among eukaryotes. 相似文献
992.
Anderson HR 《Science (New York, N.Y.)》1963,139(3549):42-45
993.
994.
995.
Anderson OL 《Science (New York, N.Y.)》1981,213(4503):76-82
A major component of the Inter-Union Commission on Geodynamics Project, labeled "Internal Properties and Processes," included certain experimental and theoretical research in tectonophysics, seismology, geochemistry, petrology, volcanology, and planetology. This review focuses on a few research areas in which there have been surprises and reversals. In particular, attention is given to the attempts to quantify the thermal profile in the earth's interior and the material properties of the earth's interior. 相似文献
996.
A quantitative method was used to determine the concentration of receptor-estrogen complex in the nuclear fraction of rat uterine cells throughout the estrous cycle. The concentrations of nuclear receptor-estrogen complex were: metestrus, 0.22; diestrus, 0.75; proestrus, 1.29; and estrus, 0.31 picomoles per milligram of DNA. This cyclic fluctuation in the nuclear complex closely parallels the secretion of ovarian estrogen during the estrous cycle, an indication that the accumulation of receptor-estrogen complex by the nuclear fraction of uterine cells may be of physiological significance, and under the control of endogenous estrogen. 相似文献
997.
998.
999.
Retroviral infection involves continued genetic variation, leading to phenotypic and immunological selection for more fit virus variants in the host. For retroviruses that cause immunodeficiency, pathogenesis is linked to the emergence of T cell-tropic, cytopathic viruses. Here we show that an immunodeficiency-inducing, T cell-tropic feline leukemia virus (FeLV) has evolved such that it cannot infect cells unless both a classic multiple membrane-spanning receptor molecule (Pit1) and a second coreceptor or entry factor are present. This second receptor component, which we call FeLIX, was identified as an endogenously expressed protein that is similar to a portion of the FeLV envelope protein. This cellular protein can function either as a transmembrane protein or as a soluble component to facilitate infection. 相似文献
1000.