全文获取类型
收费全文 | 13208篇 |
免费 | 807篇 |
国内免费 | 1053篇 |
专业分类
林业 | 730篇 |
农学 | 957篇 |
基础科学 | 443篇 |
1404篇 | |
综合类 | 4384篇 |
农作物 | 1704篇 |
水产渔业 | 462篇 |
畜牧兽医 | 2635篇 |
园艺 | 1152篇 |
植物保护 | 1197篇 |
出版年
2024年 | 99篇 |
2023年 | 299篇 |
2022年 | 466篇 |
2021年 | 568篇 |
2020年 | 531篇 |
2019年 | 686篇 |
2018年 | 612篇 |
2017年 | 533篇 |
2016年 | 812篇 |
2015年 | 1020篇 |
2014年 | 1139篇 |
2013年 | 1076篇 |
2012年 | 1116篇 |
2011年 | 792篇 |
2010年 | 641篇 |
2009年 | 623篇 |
2008年 | 493篇 |
2007年 | 565篇 |
2006年 | 633篇 |
2005年 | 460篇 |
2004年 | 272篇 |
2003年 | 207篇 |
2002年 | 175篇 |
2001年 | 171篇 |
2000年 | 185篇 |
1999年 | 113篇 |
1998年 | 116篇 |
1997年 | 93篇 |
1996年 | 80篇 |
1995年 | 64篇 |
1994年 | 66篇 |
1993年 | 41篇 |
1992年 | 45篇 |
1991年 | 32篇 |
1990年 | 40篇 |
1989年 | 28篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 33篇 |
1984年 | 19篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 20篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
51.
对在山东的济南、平度、莱西、烟台种植的几种陆地棉(Gossypium hirsutumL.)核雄性不育材料的育性表现进行了研究,结果表明:洞A不育系的衍生材料MB、MA在不同气候条件下有育性的变化。在济南高度不育,可作为不育系。在其他几个地区表现不同程度的可育。其中MB在平度有相当好的育性,能正常结铃。而双隐性核不育材料59A、62A未能观察到育性变化。本文就核不育材料在棉花杂交制种中的应用前景及需深入研究的问题作了探讨。 相似文献
52.
53.
54.
55.
56.
AIM:The β-catenin is a key molecule in the Wnt signal pathway, which plays a critical role in normal development and tumorigenesis. However, the mechanisms of the β-catenin on the cell growth control are still not completely defined. The aim of this study was to test the hypothesis that the mutant β-catenin may regulate the hepatocyte proliferation. METHODS: The immortalized murine hepatocyte cell line, AML12, was used for this study. A plasmid that contain mutant β-catenin S33Y was transfected into the AML12 cells and a stable cell line AML12S33Y was established. The cell growth property of this cell line and the parental cell were compared by flow cytometry analysis and direct cell count. The cells were also tested for the ability to form soft agar colonies, and the ability to form tumors in the severe immune deficient mice (SCID). RESULTS:1. The mutant β-catenin containing cell line AML12S33Y has higher proliferating index compared with the parental AML12 cells (P<0.01), suggesting that mutant β-catenin promotes cell growth. 2. The mutant β-catenin cells formed small colonies in soft agar after 4 weeks of culture, but did not generate tumor in SCID mice. CONCLUSION:The mutant β-catenin promotes liver cell growth. 相似文献
57.
AIM:To investigate the effect of tea-polyphenols (TP) on the activation of NF-κB and the expression of TGF-β1 mRNA in THP-1 cells (a human acute monocytic leukemia cell line). METHODS:THP-1 cells were incubated with the different concentrations of TP, VLDL, LDL or ox-LDL. In the THP-1 cellls, the nuclear malposition rate of NF-κB was detected with immunohistochemistry technique, the positive index of the TGF-β1 mRNA expression was detected by hybridization in situ, and accumulation of total cholesterol (TC) in cells incubated with 0.4-40 μg/L TP was determined with oxidase assay. RESULTS:The nuclear malposition rate of NF-κB, the positive index of the TGF-β1 mRNA expression and TC in THP-1 cells incubated with 0.4-40 μg/L of TP were lower than those with 0 μg/L of TP in TP-V group, TP-L group and TP-O (P<0.05). The differences of these markers in THP-1 cells incubated with more than 40 μg/L TP in TP-V group, TP-L group and TP-O were not statistically significant, compared with TP-C group (P>0.05). CONCLUSION:TP inhibited the activation of NF-κB, the expression of TGF-β1 mRNA and the foam cell formation in the mono-macrophage. 相似文献
58.
Accomodation of important sources of uncertainty in ecological models is essential to realistically predicting ecological processes. The purpose of this project is to develop a robust methodology for modeling natural processes on a landscape while accounting for the variability in a process by utilizing environmental and spatial random effects. A hierarchical Bayesian framework has allowed the simultaneous integration of these effects. This framework naturally assumes variables to be random and the posterior distribution of the model provides probabilistic information about the process. Two species in the genus Desmodium were used as examples to illustrate the utility of the model in Southeast Missouri, USA. In addition, two validation techniques were applied to evaluate the qualitative and quantitative characteristics of the predictions.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
59.
应用生物源农药防治水稻病害 总被引:2,自引:0,他引:2
在稻瘟病始见期天始,喷施4%春雷霉素二次可以控制病害;用3%克菌康1:400倍液喷雾,可以有效控制水稻白叶枯病的危害,在孕穗期初现病时开始,喷链霉素1000万单位二次,也能防治白叶枯病;在纹枯病始现期喷40%纹霉星,病指防效可达67-81%。 相似文献
60.