全文获取类型
收费全文 | 37891篇 |
免费 | 3485篇 |
国内免费 | 1962篇 |
专业分类
电工技术 | 2062篇 |
技术理论 | 1篇 |
综合类 | 3476篇 |
化学工业 | 3840篇 |
金属工艺 | 2936篇 |
机械仪表 | 2536篇 |
建筑科学 | 6364篇 |
矿业工程 | 1399篇 |
能源动力 | 960篇 |
轻工业 | 1656篇 |
水利工程 | 1552篇 |
石油天然气 | 2132篇 |
武器工业 | 729篇 |
无线电 | 4966篇 |
一般工业技术 | 3355篇 |
冶金工业 | 1536篇 |
原子能技术 | 336篇 |
自动化技术 | 3502篇 |
出版年
2024年 | 96篇 |
2023年 | 365篇 |
2022年 | 596篇 |
2021年 | 738篇 |
2020年 | 742篇 |
2019年 | 743篇 |
2018年 | 702篇 |
2017年 | 988篇 |
2016年 | 1038篇 |
2015年 | 1101篇 |
2014年 | 1863篇 |
2013年 | 1861篇 |
2012年 | 2448篇 |
2011年 | 2666篇 |
2010年 | 2079篇 |
2009年 | 2155篇 |
2008年 | 2411篇 |
2007年 | 3100篇 |
2006年 | 2836篇 |
2005年 | 2507篇 |
2004年 | 2152篇 |
2003年 | 1834篇 |
2002年 | 1413篇 |
2001年 | 1293篇 |
2000年 | 1080篇 |
1999年 | 869篇 |
1998年 | 687篇 |
1997年 | 561篇 |
1996年 | 476篇 |
1995年 | 396篇 |
1994年 | 322篇 |
1993年 | 239篇 |
1992年 | 195篇 |
1991年 | 159篇 |
1990年 | 145篇 |
1989年 | 126篇 |
1988年 | 93篇 |
1987年 | 55篇 |
1986年 | 56篇 |
1985年 | 25篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 18篇 |
1979年 | 8篇 |
1966年 | 7篇 |
1964年 | 5篇 |
1957年 | 7篇 |
1955年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
针对深圳地铁的桩基托换而进行了一种新型预应力托换结点的试验研究,通过试验,得到了此托换结点的受力特性,为同类的大型托换的理论及实践提供了一种安全可行的方案。 相似文献
102.
对唐钢第二炼铁厂3#高炉开口机的工作原理及其在工作中存在的问题进行了分析,通过对开口机四连杆机构、十路接头油管的改造,节约了大量的备件费用,具有较好的推广使用价值。 相似文献
103.
Techniques and Apparatus for Measuring Rotational Core Losses of Soft Magnetic Materials 总被引:1,自引:0,他引:1
In many situations such as the cores of a rotating electrical machine and the T joints of a multiphase transformer, the local flux density varies with time in terms of both magnitude and direction, i.e. the flux density vector is rotating. Therefore, the magnetic properties of the core materials under the rotating flux density vector excitation should be properly measured, modeled and applied in the design and analysis of these electromagnetic devices. This paper presents an extensive review on the development of techniques and apparatus for measuring the rotational core losses of soft magnetic materials based on the experiences of various researchers in the last hundred years. 相似文献
104.
We have investigated synthesis conditions and some properties of sprayed Cu2ZnSnS4 (CZTS) thin films in order to determine the best preparation conditions for the realization of CZTS based photovoltaic solar cells. The thin films are made by means of spraying of aqueous solutions containing copper chloride, zinc chloride, tin chloride and thiourea on heated glass substrates at various temperatures. In order to optimize the synthesis conditions of the CZTS films, two series of experiments are performed. In the first series the sprayed duration was fixed at 30 min and in the second it is fixed at 60 min. In each series, the substrate temperature was changed from 553°K to 633°K. The X-ray diffraction shows, on one hand, that the best crystallinity was obtained for 613°K as substrate temperature and 60 min as sprayed duration. On the other hand, these CZTS films exhibit the kesterite structure with preferential orientation along the [112] direction. Atomical Force Microscopy was used to determine the grain sizes and the roughness of these CZTS thin film. After the annealing treatment, we estimated the optical band-gap energy of the CZTS thin film exhibiting the best crystallinity as 1.5 eV which is quite close to the optimum value for a solar cell. 相似文献
105.
航空放射性遥感系统采用航空γ能谱仪,在空中飞行探测地表放射性,能够快速进行大面积环境放射性调查。结合已经开始进行的首次大面积航空放射性遥感调查工作,简要介绍了航空放射性遥感系统构成、核探测γ能谱测量和数据处理技术。对系统转换因子刻度和剥离系数刻度方法进行了讨论,并对初步应用情况进行了总结。 相似文献
106.
107.
Summary We introduce a very simple model for thermally activated atomic migration on a lattice, and several techniques to handle it. For thermodynamical systems, the model can be used for simulating decomposition paths taking into account relevant metallurgical features. Close to equilibrium, the simplest mean-field approximation of the model can be linearized with respect to the departure from equilibrium; one then gets a microscopic interpretation of classical phenomenological coefficients, such as mobility, interfacial transfer coefficient, rate constants for the coupled relaxation of concentration and order fields. Further away from the equilibrium, the nonlinearities can be taken into account in a consistent way. For driven alloys, i.e. alloys submitted to external forcing, forced atomic migration is added to the model and new features emerge: the model is supported by several experimental results some of which confirmed its predictions a posteriori. 相似文献
108.
The condition of the surfaces is of crucial importance for the deuterium permeation through materials. In this work a study of the surface constants for the adsorption (σk1) and release (σk2) of deuterium under different surface conditions on the martensitic steel DIN 1.4914 (MANET) has been carried out. The growth of an oxide surface layer (Cr2O3) of about 25–30 nm in a MANET sample, heat treated in an oxidizing environment, compared to the bare MANET that have a ‘natural' oxide of about 5 nm has provoked a reduction of both the permeation rate and the recombination coefficient (about 3 orders of magnitude). In addition, the permeation governing process has changed from diffusion-limited to surface-limited. The measurements of the permeation rate of deuterium were performed by a gas-phase permeation technique over the temperature range 574–746 K and for deuterium driving pressures in the range from 3 to 105 Pa. 相似文献
109.
不锈钢网架结构试验研究 总被引:1,自引:1,他引:0
对奥氏体不锈钢网架结构的物理力学性能、焊接性能加以分析,并进行了不锈钢焊接空心球节点承载力试验,确定了该种节点的受拉和受压承载能力。在此基础上,又做了不锈钢组合扭网壳模型的破坏性试验研究,试验结果与理论计算值比较,吻合较好。 相似文献
110.
Real-time accurate hand path tracking and joint trajectory planning for industrial robots (I) 总被引:1,自引:0,他引:1
Previously, researchers raised the accuracy for a robot’s hand to track a specified path in Cartesian space mainly through
increasing the number of knots on the path and the number of the path’s segments, which results in the heavier online computational
burden for the robot controller. Aiming at overcoming this drawback, the authors propose a new kind of real-time accurate
hand path tracking and joint trajectory planning method. Through selecting some extra knots on the specified hand path by
a certain rule and introducing a sinusoidal function to the joint displacement equation of each segment, this method can greatly
raise the path tracking accuracy of robot’s hand and does not change the number of the path’s segments. It also does not increase
markedly the computational burden of robot controller. The result of simulation indicates that this method is very effective,
and has important value in increasing the application of industrial robots.
Foundation item: Foundation of the Robotics Laboratory, Chinese Academy of Sciences (No. RL200002)
Biography of the first author: TAN Guan-zheng, Dr., professor, born in Oct. 1962, majoring in artificial intelligence, robotics and automation. 相似文献