全文获取类型
收费全文 | 50619篇 |
免费 | 1032篇 |
国内免费 | 1778篇 |
专业分类
林业 | 4415篇 |
农学 | 2988篇 |
基础科学 | 3060篇 |
2706篇 | |
综合类 | 19248篇 |
农作物 | 2809篇 |
水产渔业 | 1776篇 |
畜牧兽医 | 11337篇 |
园艺 | 3728篇 |
植物保护 | 1362篇 |
出版年
2024年 | 372篇 |
2023年 | 1204篇 |
2022年 | 1321篇 |
2021年 | 1113篇 |
2020年 | 1059篇 |
2019年 | 1499篇 |
2018年 | 1647篇 |
2017年 | 790篇 |
2016年 | 999篇 |
2015年 | 1096篇 |
2014年 | 2690篇 |
2013年 | 1947篇 |
2012年 | 2394篇 |
2011年 | 2332篇 |
2010年 | 1981篇 |
2009年 | 2149篇 |
2008年 | 2191篇 |
2007年 | 2074篇 |
2006年 | 1968篇 |
2005年 | 1802篇 |
2004年 | 1688篇 |
2003年 | 1518篇 |
2002年 | 1409篇 |
2001年 | 1288篇 |
2000年 | 1347篇 |
1999年 | 1267篇 |
1998年 | 1238篇 |
1997年 | 1230篇 |
1996年 | 1173篇 |
1995年 | 1102篇 |
1994年 | 1063篇 |
1993年 | 1020篇 |
1992年 | 907篇 |
1991年 | 822篇 |
1990年 | 801篇 |
1989年 | 633篇 |
1988年 | 296篇 |
1987年 | 261篇 |
1986年 | 269篇 |
1985年 | 257篇 |
1984年 | 218篇 |
1983年 | 203篇 |
1982年 | 143篇 |
1981年 | 156篇 |
1980年 | 83篇 |
1979年 | 55篇 |
1963年 | 24篇 |
1962年 | 25篇 |
1959年 | 31篇 |
1957年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
991.
Xu Jiang Xian Xuefu Du Yungui Zhang Guangyang 《保鲜与加工》1993,(5):42-47
992.
Zhang Xiangwei Xu Meihe 《保鲜与加工》1991,(4):8-15
The reliability of random vibration is discussed,and then by using the first order perturbation method and with the aid of relation of the systemic response function to the first order sensetivity of variable damp parameter, the rate of change of structural reliability indication is derived, therefore the constraint equation to guarantee reliability for the structural optimization design is proved and the satisfactory result is obtained,test and the practicability of this method is tested. 相似文献
993.
Zhang Caian Mo Lilong Lu Zhiwen 《保鲜与加工》1992,(6):128-131
This paper discuss the effects of automatic plug mills in small seamless tube mills. Far from traditional ideas,the auther comes rp with mew ideas, which adot the mew process of replacing rolling by piercing,a huge sum of economical interests and great social benefits will be gained. 相似文献
994.
Zhang Shiqing 《保鲜与加工》1996,(6):96-103
This paper generalizes all known results on Rabinowitz's minimal periodic solution conjecture under the assumption that Hamiltonian function is C2 strictly convex. 相似文献
995.
Zhang Wei Ren Zhen Qin Yihong Liao Qing 《保鲜与加工》1990,(1):56-62
A flexible mathematical model used for dynamic simulation studies of HVDC systems which is based on the stale variable method is presented, and the correspongding computer program has been implemented. Generality, easy to use, and suitable to run on microcomputers are the main features of the model and the computer program. Therefore the model is easy to be extended for application. An example is given in the paper to verily the coneclness of the model and the program. 相似文献
996.
Zhang Shiqing 《保鲜与加工》1989,(1):105-107
In this paper, by use of the pseudo-gradient vector field, the three critical points theorem in [2] is extended to the C1 function in the Ba-nach space, and therefore the three critical, points theorem in [5] is strengthened and the existence of the saddle point of the C2 function is discussed. 相似文献
997.
998.
Zhang Dingfei Wh Enling 《保鲜与加工》1989,(5):51-58
This paper deals with the kinetics of carbon atoms transfer from gas phase to solid phase in gas carburizing. According to the kinetic equations of the chemical reactions on the solid surface, it is deduced that the carbon transfer quantity from gas phase to solid phase is in direct proportion to the difference of carbon activiries between gas phase and solid phase. Based on what is mentioned above, we set up the kinetic equation of carbon transfer from gas phase to solid phase, discussed the factors which affected the carbon transfer. It was known then that increasing the contents of carbon monoxide and hydrogen in gas phase could qu'icken the carbon transfer. On the other hand, proper oxidants, especially proper water, could quicken the carbon transfer. 相似文献
1000.
Zhang Deshan 《保鲜与加工》1988,(2)
This paper suggests a calculation formula for eccentrically loaded brickwork or column with biaxial bending in terms of ultimate strength design method. The coefficients of the formula, are compiled as design charts so that the formula can be directly used for design of this kind of structural members. 相似文献