全文获取类型
收费全文 | 13623篇 |
免费 | 782篇 |
国内免费 | 1634篇 |
专业分类
林业 | 1563篇 |
农学 | 1980篇 |
基础科学 | 1327篇 |
2597篇 | |
综合类 | 4096篇 |
农作物 | 781篇 |
水产渔业 | 529篇 |
畜牧兽医 | 1794篇 |
园艺 | 395篇 |
植物保护 | 977篇 |
出版年
2024年 | 61篇 |
2023年 | 184篇 |
2022年 | 441篇 |
2021年 | 592篇 |
2020年 | 534篇 |
2019年 | 559篇 |
2018年 | 327篇 |
2017年 | 539篇 |
2016年 | 460篇 |
2015年 | 660篇 |
2014年 | 606篇 |
2013年 | 741篇 |
2012年 | 892篇 |
2011年 | 912篇 |
2010年 | 864篇 |
2009年 | 809篇 |
2008年 | 748篇 |
2007年 | 821篇 |
2006年 | 765篇 |
2005年 | 692篇 |
2004年 | 331篇 |
2003年 | 233篇 |
2002年 | 231篇 |
2001年 | 239篇 |
2000年 | 260篇 |
1999年 | 368篇 |
1998年 | 296篇 |
1997年 | 271篇 |
1996年 | 233篇 |
1995年 | 254篇 |
1994年 | 177篇 |
1993年 | 203篇 |
1992年 | 173篇 |
1991年 | 135篇 |
1990年 | 123篇 |
1989年 | 84篇 |
1988年 | 68篇 |
1987年 | 56篇 |
1986年 | 34篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1973年 | 2篇 |
1964年 | 2篇 |
1963年 | 3篇 |
1935年 | 1篇 |
1934年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
131.
杂交水稻品种鉴定技术研究 总被引:1,自引:1,他引:1
该试验用幼苗形态鉴定法对杂交裟品种进行鉴定。结果表明,通过特定的温度、光照和药剂处理,杂交一代F1的茎基部呈深红色,而不育系A和保持系B的茎基部无色或仅呈微红色。故可鉴定出F1的纯度,但不能将A与B区分出来。 相似文献
132.
Magnetorheological materials are a class of smart materials whose reological properties may be rapidly varied by application of magnetic field. By a simple mechanical mold, a visco-plastic model for the materials is developed. It is shown that the model can describe the variation of the mechanical properties for the Magnetorheological materials in the different magnetic field. The result is shown that the model can characterize the mechanical properties of Magnetorheological Materials in plastic and viscous variation. 相似文献
133.
To construct data warehouse with heterogeneous, self-governing and distributed database system is a challenge. Two problems have to be solved: one is how to collect data from heterogeneous data sources by an effective method, the other is how to clear up and change the format of the data collected from data sources. The opening and the interact-operation property of Web Services is Analyzed. A Data Collection System based on Web Services, which communicates with heterogeneous data sources with SOAP and HTTP, has been designed. A Data Collector is introduced to clear up and to transform data with composition technology. The pivotal XML technology of transforming and loading up the data are discussed. 相似文献
134.
Hu Ning Chang Ruqing 《保鲜与加工》1991,(4):16-19
In this paper,a new algorithm for solving large-scale finite element system is presented, which utilizes the architecture of parallel processing. Firstly, the structure is partitioned into sub-regions. Then multi-fronts are used to assemble and eliminate concurrently in every sub-region. Thus the condensed interface stiffness matrices and load vectors are obtained. By serially assembling and solving global equation to get interface displacements and backing to every sub-region, the inter-nodal displacements and element stresses can be solved. The results of computation show that it can not only increase the speed of computation,but also save the memory space of computer effectively. This algorithm is an effective method for solving large-scale structural finite element systems. 相似文献
135.
The high-precision displacement measuring technology of optic-measuring mechanics is, for the first time,successfully applied on the similar model of the model land-layer with a new-type variable modulus of elasticity. The angle of movement and the distributed displacement of upper and lower rock-layers are measured. The technology is a combination of laser's technology and the modern chemical sticker-it is called the sticking moire interferometry. Compared with the measured values, the result is very satisfactory. 相似文献
136.
The design of multi-controller and multi-mode control law is presented for the three-link Acrobot on horizontal bar by employing Human simulated intelligent control method based on sensory-motor Schema.Imitated the characteristics of gymnast's swing-up and handstand movement,the control process of robot is divided by six sequence phase.Then the sensory cell and motor cell and the group of sensory-motor schema is designed based on the analysis of quality-quantity combination.The simulation results show that the controller ensures the gesture and the energy to the desired goal,farther more the motion control of giant swing backword is realized in the simulation. 相似文献
137.
Zhang Jin Hu Zhenji Zhou Shangqi 《保鲜与加工》1991,(3):44-47
The phase transformation in the diffusion layer after slow cooling and aging of pure iron ion -nitrided was investigated with TEM. Refering to principle of Moire method measuring macroscopical strain, the values of coherent strain at interfaces between a" and aN phases were determined by means of TEM analyses. 相似文献
138.
139.
The development circumstance about Handhold Computer technology and products at home and abroad are described in details, resumes the development of the technology and elaborates the difference between our country's technology and the advanced foreign technology. Besides, it also introduces the relationship of Windows CE and Handhold Computer. 相似文献
140.
The solution of the office automation system for the universities is given. The detail steps on developing an office automation system through Lotus Notes are described. 相似文献