全文获取类型
收费全文 | 3406篇 |
免费 | 128篇 |
国内免费 | 249篇 |
专业分类
林业 | 584篇 |
农学 | 187篇 |
基础科学 | 653篇 |
451篇 | |
综合类 | 1385篇 |
农作物 | 87篇 |
水产渔业 | 52篇 |
畜牧兽医 | 244篇 |
园艺 | 47篇 |
植物保护 | 93篇 |
出版年
2024年 | 20篇 |
2023年 | 69篇 |
2022年 | 107篇 |
2021年 | 106篇 |
2020年 | 73篇 |
2019年 | 121篇 |
2018年 | 59篇 |
2017年 | 106篇 |
2016年 | 141篇 |
2015年 | 106篇 |
2014年 | 135篇 |
2013年 | 123篇 |
2012年 | 246篇 |
2011年 | 227篇 |
2010年 | 194篇 |
2009年 | 225篇 |
2008年 | 212篇 |
2007年 | 258篇 |
2006年 | 213篇 |
2005年 | 176篇 |
2004年 | 131篇 |
2003年 | 125篇 |
2002年 | 94篇 |
2001年 | 92篇 |
2000年 | 71篇 |
1999年 | 71篇 |
1998年 | 54篇 |
1997年 | 48篇 |
1996年 | 38篇 |
1995年 | 35篇 |
1994年 | 19篇 |
1993年 | 22篇 |
1992年 | 22篇 |
1991年 | 12篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 15篇 |
1987年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有3783条查询结果,搜索用时 453 毫秒
31.
Xiang Dong 《保鲜与加工》1992,(6):98-105
A new scoap-like testability measure SCTM(a signal conflict oriented testability meaure) is presented, which represents not only the difficulty to control and observe the value of a node,but also the probability to cause signal conflict in the process of test generation. A parallel calculation scheme is offered, which speeds up the calculation m/2 times. Here m is the word length of a computer. 相似文献
32.
Zhao Yunbin Duan Yurong 《保鲜与加工》1993,(5):125-130
A new globally convergent algorithm was presented for a continuous differen-tiable nonlinear programming by defining a measure function deviating from the Kuhn-Tucker point. With this algorithm which can be used to get the optimum solution of the problem,the optimal lagrangian multiplier corresponding the optimal solution of the problem was also obtained. A new iterative algorithm for quadratic programming is obtained when applying the general algorithm to quadratic programming. Finally,a numerical example was given. 相似文献
33.
Chen Ganping Xu Guoyu Qin Yihong 《保鲜与加工》1990,(1):43-48
A digital power system stabilizer ( DPSS ) and its design method are presented in this paper. The mathematical model of a single machine infinite bus power system is obtained using off-line parameter identifications, and on the base of the identified model the control system is synthesized by generalized minimum variance control principles. Through feedback combination of several signals this control system has double functions of damping low frequency oscillation and automatic voltage regulating. In order to avoid static errors the very effective way is to combine discrete generalized minimum variance control with continuous integral control. Besides the proposed control strategy is very simple in structures and very easy to realize. Simulation results under several cases have shown the correctness and effectiveness of the proposed control strategy. 相似文献
34.
35.
In this paper, partial differential equations of vortex flow-stream function in boundary fitted coordinates and related ADI equations were listed. The flow around a cylinder in quadrilateral area by auto control boundary was computed. The diagram of distribution of speed arrow, constant lines of flow-stream function, vortex, two speed parts and pressure were studied. 相似文献
36.
37.
38.
39.
论证了30装载机断裂机理,通过对动臂危险截面受力分析,在不改变工作装置各零部件铰点、保证零部件通用性的情况下,增加动臂板危险截面面积,提高动臂危险截面处安全系数,改进下料与焊接工艺,从而避免了动臂断裂。 相似文献
40.