全文获取类型
收费全文 | 29131篇 |
免费 | 1217篇 |
国内免费 | 2255篇 |
专业分类
林业 | 3681篇 |
农学 | 2295篇 |
基础科学 | 3764篇 |
3669篇 | |
综合类 | 13734篇 |
农作物 | 901篇 |
水产渔业 | 828篇 |
畜牧兽医 | 2011篇 |
园艺 | 797篇 |
植物保护 | 923篇 |
出版年
2024年 | 125篇 |
2023年 | 345篇 |
2022年 | 556篇 |
2021年 | 684篇 |
2020年 | 692篇 |
2019年 | 811篇 |
2018年 | 515篇 |
2017年 | 823篇 |
2016年 | 1115篇 |
2015年 | 990篇 |
2014年 | 1443篇 |
2013年 | 1417篇 |
2012年 | 2253篇 |
2011年 | 2385篇 |
2010年 | 1881篇 |
2009年 | 1987篇 |
2008年 | 1932篇 |
2007年 | 2239篇 |
2006年 | 1831篇 |
2005年 | 1578篇 |
2004年 | 1149篇 |
2003年 | 962篇 |
2002年 | 743篇 |
2001年 | 641篇 |
2000年 | 524篇 |
1999年 | 424篇 |
1998年 | 392篇 |
1997年 | 326篇 |
1996年 | 309篇 |
1995年 | 281篇 |
1994年 | 252篇 |
1993年 | 223篇 |
1992年 | 178篇 |
1991年 | 121篇 |
1990年 | 165篇 |
1989年 | 104篇 |
1988年 | 107篇 |
1987年 | 45篇 |
1986年 | 21篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1956年 | 2篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
企业文化是企业可持续发展的精神支柱,为企业发展提供核心竞争力。针对企业文化建设中的认识误处,分析了企业文化与农业机械化服务组织的关系,阐述了企业文化在农机化服务体系建设中的作用。对开展企业文化建设,推动农机化服务体系健康发展具有重要意义。 相似文献
102.
为了解河北省玉米产量变化的规律,明确今后育种工作的目标和前景,利用灰色系统理论的GM(1,1)模型,依据1980-2003年河北省审定的玉米品种的区域试验产量,建立预测模型为:^X(k+1)^(1)=324 818.583 945e^0.018524-318 652.083 945。并在生产因素保持相对稳定的条件下,据此模型对河北省玉米生产进行规划性预测,为生产的规划与决策提供科学依据。预测结果表明,在挖掘耕地资源和非耕地资源的生产潜力,提高农业资源综合生产能力的情况下,河北省的玉米产量将在2030年有可能达到15 052.6 kg/hm^2。 相似文献
103.
104.
Wang Jianping Mi Linshu Chen Gang 《保鲜与加工》1993,(6):32-37
The angular frequency and decaying constant of each copmonect for the
transient waveform in power systems were obtained by using the discrete Fourier transform; the amplitude and phase angle were calculated in the linear curve fitting method. And all of the parameters obtained above were treated in an unified optimization by using the curve fitting optimization of the least square method of general nonlinear funcrion so as to get the results of waveform analysis. Two examples are included. 相似文献
105.
In component-based system regression testing, the dependence model of component-based system should be built in order to confirm the part which will be affected by modify. Since high reusability and high complexity, the existing dependence models may not be applicable to component-based systems, a hierarchical dependence model is proposed to describe component-based. Through the forward slicing of modified points in the model, the modified and affected parts can be gotten, then traverse these parts and get affected testing path, thereby regression testing examples can be chosen effectively, the efficiency of regression testing can be improred. 相似文献
106.
According to the new requirement of sustainable development in the new stage, this paper puts forward the definition of the safeguarding capacity of regional sustainable development and uses some statistical methods of frequency statistics and principal component analysis to construct the index system of safeguarding capacity. Then it takes the data of the Three Gorges reservoir area for example to make empirical analysis, and provides efficient measurement tools to further measure the regional sustainability together with its safeguarding capacity, and therefore helps the government and the relevant organizations to establish more scientific policies of sustainable development. 相似文献
107.
According to the needs of setting up a professional system based on motorcycle design,the CBR(case based reasoning) and RBR(rule based reasoning) methods are introduced.After discussing the difference between the two kinds of reasoning,a method of integrating them into the motorcycle design flow is put forward to realize the design reusable technology and improve the design efficiency,by using the CBR in the step of selecting the similar motorcycle and the RBR in project's modification according to correlative rules. 相似文献
108.
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
109.
Yi Shuping Gai Xuchang Xu Xiangsui 《保鲜与加工》1992,(2):65-70
Based on Group Technology, part families of the norm of working hour are formed according to the similarity among components. With the progressive regerssion, the models of the norm of working hour are built for every part family. A computer aided norm model building program and a computer aided norm of working hour planning system are developed. The system is successfully integrated with CAD/CAPP system. Some examples of the model building and calculation results are illustrated as well. 相似文献
110.
At present, in the evaluation process of the real estate value the material form is mainly concentrated on, while the value brought by the real estate brand are usually neglected. In this paper, considering the particularity of the real estate brand evaluation, the method of network analysis is adopted. In the evaluation process, the evaluation method of excess income law are developed by leading the thoughts and methods of the fuzzy set theory, and a systematic assess model is found. Then, an example is given as illustration. At last, the appraise about the application of the model is made. 相似文献