全文获取类型
收费全文 | 1896篇 |
免费 | 124篇 |
国内免费 | 197篇 |
专业分类
林业 | 190篇 |
农学 | 160篇 |
基础科学 | 245篇 |
269篇 | |
综合类 | 891篇 |
农作物 | 42篇 |
水产渔业 | 104篇 |
畜牧兽医 | 162篇 |
园艺 | 45篇 |
植物保护 | 109篇 |
出版年
2024年 | 15篇 |
2023年 | 38篇 |
2022年 | 75篇 |
2021年 | 73篇 |
2020年 | 60篇 |
2019年 | 73篇 |
2018年 | 61篇 |
2017年 | 82篇 |
2016年 | 90篇 |
2015年 | 71篇 |
2014年 | 120篇 |
2013年 | 79篇 |
2012年 | 161篇 |
2011年 | 140篇 |
2010年 | 86篇 |
2009年 | 126篇 |
2008年 | 85篇 |
2007年 | 140篇 |
2006年 | 86篇 |
2005年 | 76篇 |
2004年 | 65篇 |
2003年 | 68篇 |
2002年 | 39篇 |
2001年 | 33篇 |
2000年 | 40篇 |
1999年 | 34篇 |
1998年 | 20篇 |
1997年 | 24篇 |
1996年 | 21篇 |
1995年 | 19篇 |
1994年 | 18篇 |
1993年 | 21篇 |
1992年 | 22篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1986年 | 1篇 |
排序方式: 共有2217条查询结果,搜索用时 15 毫秒
1.
2.
3.
This paper points out the shortcoming of the existing project break-even analysis method. A new improved method-the dynamic project break-even analysis method has been put forward. 相似文献
4.
He Chuanjiang 《保鲜与加工》1993,(3):116-120
A three critical point theorem is proved. As its applications, Dirichlet problem for a class of quasilinear elliptic equations cf second order is considered. 相似文献
5.
6.
ZHANG Chun-tao~ 《保鲜与加工》2004,(7):78-81
Crossover operator and mutation operator are basic operators of genetic algorithm , which play important roles in improving the quality of the solution populations. We propose the improved crossover operator , mutation operator and rotation operator on the basis of good point set with the traveling salesman problem , the experimental result shows these operators are very efficient. 相似文献
7.
With the rapid increase of the Internet user and widely application of Web,the current network technology is facing great challenge. More and more multimedia operations occupy plenty of bandwidth,and result in the network congestion. Therefore,people begin to use QoS to utilize the bandwidth effectively,and ensure the transport of the emergent operation data. The paper introduces the protocols and basic components of QoS,then expatiates the conception and the basic principles of policy control QoS, moreover,emphasizes the structure model of policy control QoS and how it runs. At last,it introduces the transport process of data packets under the control of policies in a policy control QoS system,and how to make the policies in the real world. 相似文献
8.
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
9.
10.
In this paper,by the use of Farkas lemma and its inve-rse proposition,the generalized Kuhu-Tuoker conditions for the existanceof strong minimum point in differential multiobjective programming inBanach spaces and the existance of sufficient condition of weak Paretominimum Foint are derived. 相似文献