全文获取类型
收费全文 | 276123篇 |
免费 | 30231篇 |
国内免费 | 258篇 |
专业分类
306612篇 |
出版年
2016年 | 3080篇 |
2015年 | 4302篇 |
2014年 | 4855篇 |
2013年 | 7384篇 |
2012年 | 7943篇 |
2011年 | 8195篇 |
2010年 | 5434篇 |
2009年 | 5012篇 |
2008年 | 7420篇 |
2007年 | 7528篇 |
2006年 | 7163篇 |
2005年 | 6910篇 |
2004年 | 6818篇 |
2003年 | 6600篇 |
2002年 | 6393篇 |
2001年 | 11749篇 |
2000年 | 11792篇 |
1999年 | 9330篇 |
1998年 | 3389篇 |
1997年 | 3622篇 |
1996年 | 3522篇 |
1995年 | 3128篇 |
1994年 | 3110篇 |
1993年 | 3105篇 |
1992年 | 7867篇 |
1991年 | 7853篇 |
1990年 | 7516篇 |
1989年 | 7475篇 |
1988年 | 6855篇 |
1987年 | 6601篇 |
1986年 | 6020篇 |
1985年 | 6207篇 |
1984年 | 5148篇 |
1983年 | 4339篇 |
1982年 | 3373篇 |
1981年 | 3145篇 |
1980年 | 2948篇 |
1979年 | 4952篇 |
1978年 | 3812篇 |
1977年 | 3725篇 |
1976年 | 3433篇 |
1975年 | 3786篇 |
1974年 | 4176篇 |
1973年 | 4093篇 |
1972年 | 3666篇 |
1971年 | 3435篇 |
1970年 | 3086篇 |
1969年 | 2995篇 |
1968年 | 2745篇 |
1967年 | 2370篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
143.
Electron microscope examination of two plaque variants from a nuclear polyhedrosis virus of the alfalfa looper, Autographa californica 总被引:3,自引:0,他引:3
This investigation looks into the ultrastructural differences between plaque variants of the alfalfa looper nuclear polyhedrosis virus. The variants exhibit distinct differences in polyhedra morphology and enveloping of the nucleocapsids.Tissues from larvae infected per os or subcutaneously with virus from one type of plaque always contained virus representative of both plaques. This was not true of the in vitro cultured cells. In those cells, a culture infected with one plaque type always developed infections that were typical of that particular plaque. 相似文献
144.
145.
146.
147.
Enumeration of denitrifying microbial populations in turf 总被引:2,自引:0,他引:2
Summary Denitrifer populations of a silt and silt loam soil under a Kentucky bluegrass turf were enumerated using the most probable
number (MPN) procedure. The influence of soil texture, soil depth, soil moisture, and additions of nitrate fertilizer on denitrifier
populations were determined.
Saturated soil conditions increased denitrifier populations 87-fold in the silt soil and 121-fold in the silt loam soil. Denitrifier
populations did not differ significantly between soil depths and additions of fertilizer nitrate did not influence populations. 相似文献
148.
149.
150.
The congenitally jaundiced Gunn rat does not conjugate bilirubin but does conjugate bilirubin dimethyl diester. Partial defects in conjugating p-nitrophenol and demethylating aminopyrine are also evident. A proposed mechanism to explain this combination of findings is a defective microsomal membrane. To examine the 'matrix' of Gunn microsomal membranes, hepatic microsomes were isolated from Gunn (jj) and outbred Wistar (JJ) rats and were studied by electron paramagnetic resonance spectroscopy of 7-doxylstearic and 12-doxylstearic acid probes, fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene, glucose-6-phosphatase activity vs. temperature, and lipid analysis. The data indicate several factors related to lipid bilayer order do not differ in microsomes from jj and JJ. 相似文献