全文获取类型
收费全文 | 963篇 |
免费 | 76篇 |
专业分类
林业 | 29篇 |
农学 | 12篇 |
基础科学 | 7篇 |
113篇 | |
综合类 | 226篇 |
农作物 | 49篇 |
水产渔业 | 57篇 |
畜牧兽医 | 467篇 |
园艺 | 28篇 |
植物保护 | 51篇 |
出版年
2020年 | 15篇 |
2019年 | 15篇 |
2018年 | 21篇 |
2017年 | 22篇 |
2016年 | 18篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 51篇 |
2012年 | 28篇 |
2011年 | 52篇 |
2010年 | 22篇 |
2009年 | 25篇 |
2008年 | 33篇 |
2007年 | 38篇 |
2006年 | 21篇 |
2005年 | 34篇 |
2004年 | 29篇 |
2003年 | 34篇 |
2002年 | 23篇 |
2001年 | 21篇 |
2000年 | 27篇 |
1999年 | 22篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1992年 | 21篇 |
1991年 | 17篇 |
1990年 | 8篇 |
1989年 | 18篇 |
1988年 | 18篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1974年 | 11篇 |
1973年 | 15篇 |
1972年 | 20篇 |
1971年 | 16篇 |
1970年 | 12篇 |
1969年 | 7篇 |
1968年 | 9篇 |
1967年 | 9篇 |
1947年 | 6篇 |
1912年 | 6篇 |
排序方式: 共有1039条查询结果,搜索用时 484 毫秒
91.
92.
Dealkylation and loss of capacity for reactivation of cholinesterase inhibited by sarin 总被引:2,自引:0,他引:2
Inhibition of rat brain acetylcholinesterase by (32)P-sarin in vivo results initially in (32)P-isopropylmethylphosphonylated enzyme. The percentage of inhibited enzyme that could not be reactivated by pyridinium aldoxime methochloride (aged enzyme) approximated the amount of radioactivity identified as (32)P-methylphosphonate. The (32)P-isopropyl methylphosphonate not released fromthe inhibited enzyme by the oxime accounted for 51 +/- 10 percent ( standard deviation) of the radioactivity fixed to brain tissue. It showed no correlation with aging and was probably bound to sites other than acetylcholinesterase. 相似文献
93.
Harris AC Kamenetsky VS White NC van Achterbergh E Ryan CG 《Science (New York, N.Y.)》2003,302(5653):2109-2111
At a porphyry copper-gold deposit in Bajo de la Alumbrera, Argentina, silicate-melt inclusions coexist with hypersaline liquid- and vapor-rich inclusions in the earliest magmatic-hydrothermal quartz veins. Copper concentrations of the hypersaline liquid and vapor inclusions reached maxima of 10.0 weight % (wt %) and 4.5 wt %, respectively. These unusually copper-rich inclusions are considered to be the most primitive ore fluid found thus far. Their preservation with coexisting melt allows for the direct quantification of important oreforming processes, including determination of bulk partition coefficients of metals from magma into ore-forming magmatic volatile phases. 相似文献
94.
95.
Campbell DB Jurgens RF Dyce RB Harris FS Pettengill GH 《Science (New York, N.Y.)》1970,170(3962):1090-1092
A radar interferometer was used to map unambiguously the surface reflectivity of Venus in the polarized mode at a wavelength of 70 centimeters. The observed region extended from 260 degrees to 30 degrees in longitude and from -60 degrees to 50 degrees in latitude with a surface resolution of approximately 3 degrees by 3 degrees . The result agrees well in most respects with earlier maps made elsewhere at shorter wavelengths and, in addition, discloses a number of new "features." 相似文献
96.
Harris JE 《Science (New York, N.Y.)》1914,40(1031):491-493
97.
98.
99.
Simmen MW Leitgeb S Charlton J Jones SJ Harris BR Clark VH Bird A 《Science (New York, N.Y.)》1999,283(5405):1164-1167
The genome of the invertebrate chordate Ciona intestinalis was found to be a stable mosaic of methylated and nonmethylated domains. Multiple copies of an apparently active long terminal repeat retrotransposon and a long interspersed element are nonmethylated and a large fraction of abundant short interspersed elements are also methylation free. Genes, by contrast, are predominantly methylated. These data are incompatible with the genome defense model, which proposes that DNA methylation in animals is primarily targeted to endogenous transposable elements. Cytosine methylation in this urochordate may be preferentially directed to genes. 相似文献
100.
Harris WA 《Science (New York, N.Y.)》1988,240(4849):229