全文获取类型
收费全文 | 463篇 |
免费 | 12篇 |
国内免费 | 4篇 |
专业分类
林业 | 32篇 |
农学 | 207篇 |
基础科学 | 4篇 |
57篇 | |
综合类 | 110篇 |
农作物 | 32篇 |
水产渔业 | 1篇 |
畜牧兽医 | 24篇 |
园艺 | 4篇 |
植物保护 | 8篇 |
出版年
2024年 | 10篇 |
2023年 | 25篇 |
2022年 | 16篇 |
2021年 | 17篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 21篇 |
2013年 | 28篇 |
2012年 | 23篇 |
2011年 | 38篇 |
2010年 | 23篇 |
2009年 | 23篇 |
2008年 | 25篇 |
2007年 | 21篇 |
2006年 | 37篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 18篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 12篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 2篇 |
排序方式: 共有479条查询结果,搜索用时 15 毫秒
1.
中国珍贵木材树种主要产地热带(除黄杨木类),为国家宝贵的热带木材资源,珍贵木材材质好,用途价值极高,由于所剩资源很少,因之限禁采伐加以保护。从热带林业长远战略思想来讲:一方面要对热带珍贵木材树种大力发展;另一方面对引入国外的珍贵木材树种要大力推广和发展,以期在下世纪中国拥有相当数量的珍贵木材资源得到利用,获得经济效益。 相似文献
2.
Ning De-juan Hou Pei-chen Hu Zan-min Shen Xin Chen Shao-liang College of Biological Sciences Biotechnology Beijing Forestry University Beijing P. R. China Institute of Genetics Developmental Biology Chinese Academy of Sciences Beijing P. R. China 《中国林学(英文版)》2006,8(4):15-19
For this paper, the plasma membrane (PM) H -ATPase gene has been cloned from Populus euphratica Oliv. through a homology based strategy. The isolated 3,210 bp cDNA contains a single 2,862 bp open reading frame (ORF) which encodes a putative H -ATPase protein of 953 amino acid residues, with a significant homology to plasma membrane H -ATPase of Primus persica, Phaseolus vulgaris, Sesbania rostrata and Daucus carota. The predicted protein has a molecular weight of 104,553 Da. The copy number analysis revealed multiple copies of the PM H -ATPase in the P. euphratica genome after digestion of their genomic DNA by the restriction enzymes EcoRI, NdeⅠ, FbaⅠand BglⅡ, and Southern blot. 相似文献
3.
Based on the theory of the K map simplification of logical function(KSLF),this article releases a ICAI Realization for KSLF.Providing three kinds of teaching style:commonness, teaching, practice.This product,wich supports for the K map simplification with random item,is not only helpful to the construction of the curriculum of digital circuit ,but also to the design for digital application system.Under the practice method, This product's guides,checks,and corrects the student's whole process forthe proceeding of KSLF automaticly under the teaching method. 相似文献
4.
Du Yang Xin Mingdao Huang Shaoming 《保鲜与加工》1995,(5):50-56
A new type of three dimenstional inner microfin tube is devoloped. Under four different pressures and in the range of condensing mass velocities from 33 to 153 kg/m2 . s,and by the experimental study of the three kinds of tubes with different microfin parameters, the performances of the condensation heat transfer for R11 in the horizontal microfin tubes and obtained. The experiments show that the inner microfin tube is a hopeful and nighty effective condensing heat transfer enhancement tube. 相似文献
5.
In urban design, only by continuous and dynamic research work from design to finally putting it into practice, can we made good control on city appearance. This article analyzes nowadays defects in our urban design from two aspects as the result establishment and validated control, and tries to conceive a feasibility plan to solve the problem. 相似文献
6.
7.
According to the requirements of communication power supply, such as high reliability, wide application and high availability, the authors raise a new remote control design for a multi-output power supply for communication equipment based on TCPIP protocol and embedded technology. Then the hardware design is given for the system is discussed based on Ethernet professional chip PRTL8019AS and related circuits. The firmware software design for the salve-computer based TCPIP technology, and the soft design of communieation and control for the master-computer are proposed based on Winsoek and MFC technology in detail A test machine is built to do the testing, the test results prove that the test machine works stably and well, satisfies the design rules and also provides a feasible method for the remote supervise in communication power supplier whose requirement includes remote supervise, no-people on duty and so on. 相似文献
8.
9.
The aerodynamic characteristic of wind turbine is calculated by applying the Blade Element Momentum(BEM) theory.Also finite element mode analysis is done for the tower and the rotor.Then the multi-dynamic model of the wind turbine is built in Adams.Also the drive chain is calculated by applying state space method and programmed in Matlab/ Simulink.With that the combined simulation of vibration characteristics is carried out on the base of MATLAB/Simulink and ADAMS,in which the transmission effects and aero-elasticity coupling is fully considered.The results show that the method is able to simulate the vibration characteristic almost the same as software Bladed,which is well-known for analyzing performance and loads for the design and certification of wind turbines. 相似文献
10.
The exact three di me nsional temperatu re distribution and thermal analysiS to inte-grated circuit substrates have been presen ted by means of numerical method of a fin ite difference.Thismethed.which will overcome the di fficuItv of mathematical deduction mav be consltieredas an analytical way aided by com puters for thermal design of electron ic compon ents. 相似文献