全文获取类型
收费全文 | 4564篇 |
免费 | 199篇 |
国内免费 | 667篇 |
专业分类
林业 | 288篇 |
农学 | 477篇 |
基础科学 | 680篇 |
920篇 | |
综合类 | 1955篇 |
农作物 | 305篇 |
水产渔业 | 47篇 |
畜牧兽医 | 165篇 |
园艺 | 171篇 |
植物保护 | 422篇 |
出版年
2024年 | 48篇 |
2023年 | 130篇 |
2022年 | 163篇 |
2021年 | 202篇 |
2020年 | 194篇 |
2019年 | 224篇 |
2018年 | 178篇 |
2017年 | 267篇 |
2016年 | 362篇 |
2015年 | 235篇 |
2014年 | 305篇 |
2013年 | 255篇 |
2012年 | 373篇 |
2011年 | 311篇 |
2010年 | 247篇 |
2009年 | 202篇 |
2008年 | 180篇 |
2007年 | 202篇 |
2006年 | 204篇 |
2005年 | 182篇 |
2004年 | 132篇 |
2003年 | 108篇 |
2002年 | 107篇 |
2001年 | 93篇 |
2000年 | 90篇 |
1999年 | 55篇 |
1998年 | 72篇 |
1997年 | 52篇 |
1996年 | 47篇 |
1995年 | 28篇 |
1994年 | 36篇 |
1993年 | 29篇 |
1992年 | 25篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 16篇 |
1988年 | 17篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1962年 | 2篇 |
排序方式: 共有5430条查询结果,搜索用时 62 毫秒
31.
32.
33.
34.
The study in molecular morphology is given with a highresolution Atomic Force Microscope AFM.IPC-208B.By taking TiN thim film prepared by magnerton sputtering method and polymide(PI) fibre for examples,the preferenthal growing plme of TiN thin film,the atomic arranges of TiN thin film on the preferential growing plme and the surficial micro-structure can be ascertained form the three-dimensional images obtamed by AFM.IPC-208B.These experiments not only identify small structures of the materials,but also affirm that AFM.IPC-208B holds the precision of atomic level and potential application in micro-structure field,at the same time it establishs the groundwork for the application in micro-process kingdom. 相似文献
35.
Liu Xiangchen Li Zeqiang 《保鲜与加工》1991,(5):109-115
In this paper the reimprovement for G. I. Taylor theory of plastic deformation in impact of cylindical projectiles is done. The impulse in the reimproved theory is G. I. Taylor' s 1/2, and 3/4 of G. I. Taylor' s improved theory. The analytical solution of the reimproved theory shows that it gives better agreement with exprimental results than those of the original Taylor' s theory and, the improved theory. 相似文献
36.
37.
Using gained experimental data to develop the models of stable flow stresses at high temperature plastic deformation by statistical methods for alloy materials, precision of the models is poor and at the same time the processes of modeling are complicated with great workload. On the basis of the data obtained on Gleeble-1500 Thermal Simulator,the predicting models for the relation between stable flow stress during high temperature plastic deformation and deformation strain, strain rate and temperature for 1420 Al-Li alloy have been developed with BP Artificial Neural Network method. The results show that the model on basis of BPNN is practical and it reflects the real feature of the deforming process. It states that the difference between the real value and the output of the model is in order of 5 percent. 相似文献
38.
Xie Shangfen Shen Hui 《保鲜与加工》1991,(4):93-96
The electrochromism of polyaniline films, which is prepared by electropolymer-ization from aniline in acidic aqueous solution onto platinum,is investigated in 330-700nm through in-situ ellipsometric technique. The results indicate that the ellipsometric peak of the reduced state(-0. 2V) of the film appears at 390-400nm and the oxidized state(0. 55V) at 500-530nm. The elec-trochromic reaction from the reduced "yellow" state to the oxidized "green" state is suggested via intermediate state whose ellipsometric peak appears at 466-470nm. 相似文献
39.
Huang Zongming 《保鲜与加工》1996,(3):42-48
Parameters dominating elasto- plastic earthquake response of SDOF systems,relation between ground motion amplitude and elasto- plastic response of SDOF systems are presented in this paper. 相似文献
40.