全文获取类型
收费全文 | 17328篇 |
免费 | 1411篇 |
国内免费 | 751篇 |
专业分类
电工技术 | 925篇 |
技术理论 | 3篇 |
综合类 | 1184篇 |
化学工业 | 3004篇 |
金属工艺 | 834篇 |
机械仪表 | 951篇 |
建筑科学 | 1418篇 |
矿业工程 | 504篇 |
能源动力 | 497篇 |
轻工业 | 1004篇 |
水利工程 | 296篇 |
石油天然气 | 1129篇 |
武器工业 | 111篇 |
无线电 | 2052篇 |
一般工业技术 | 2441篇 |
冶金工业 | 767篇 |
原子能技术 | 178篇 |
自动化技术 | 2192篇 |
出版年
2024年 | 60篇 |
2023年 | 286篇 |
2022年 | 446篇 |
2021年 | 669篇 |
2020年 | 461篇 |
2019年 | 445篇 |
2018年 | 490篇 |
2017年 | 491篇 |
2016年 | 445篇 |
2015年 | 610篇 |
2014年 | 783篇 |
2013年 | 899篇 |
2012年 | 1055篇 |
2011年 | 1139篇 |
2010年 | 1013篇 |
2009年 | 1011篇 |
2008年 | 958篇 |
2007年 | 927篇 |
2006年 | 973篇 |
2005年 | 854篇 |
2004年 | 567篇 |
2003年 | 541篇 |
2002年 | 475篇 |
2001年 | 409篇 |
2000年 | 454篇 |
1999年 | 466篇 |
1998年 | 415篇 |
1997年 | 397篇 |
1996年 | 358篇 |
1995年 | 326篇 |
1994年 | 234篇 |
1993年 | 189篇 |
1992年 | 149篇 |
1991年 | 86篇 |
1990年 | 101篇 |
1989年 | 104篇 |
1988年 | 67篇 |
1987年 | 31篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
DAI Jian S 《中国科学E辑(英文版)》2009,52(4):975-985
This paper presents a classification on the workspaces of planar serial three-link manipulators, that is, position workspace
and orientation angle workspace. Position workspace indicates the region reached by the reference point on the end-effector.
Orientation angle workspace indicates a set of angle ranges by which the end-effector can reach with certain orientation for
every point in the reachable position workspace. By introducing a virtual equivalent mechanism, reachable position workspace
can be divided into several Grashof intervals and non-Grashof intervals. The calculation equations of orientation angle workspace
are deduced in three situations according to the relationships among four link lengths in the virtual four-bar chain. Three
examples are given for three kinds of relationship of link lengths. The orientation angle workspace of extended groups, that
is, two of the three link lengths equal, and the orientation angle workspace when the reference point on the end-effector
moves along a non-radial direction are also discussed. A program is developed to calculate orientation angle workspaces and
output variation curves of orientation angle workspace and key data within the position workspace. The approach and program
in this paper can be used for fast calculation and identification of the variation rule of the orientation angle workspace
of any given planar serial three-link manipulator on the basis of its link parameters, and for the design of a highly dexterous
serial manipulator with proposed link relations.
Supported by the Natural Science Foundation of Shanxi Province (Grant No. 20041070) 相似文献
132.
DongJie Guo HaiTao Ding Haiju Wei Qingsong He Min Yu ZhenDong Dai 《中国科学E辑(英文版)》2009,52(10):3061-3070
This paper reports a new technique to fabricate an ion-exchange polymer-metal composite (IPMC) actuator. This technique is based on a hybrid organic-inorganic composite membrane. In the fabrication course, silica oxide particles, prepared from hydrolysis of tetraethyl orthosilicate in situ with sol-gel reaction, co-crystallize with perfluorosulfonate acid (PFSA) ionomer. Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) analyses demonstrate that a highly water-saving hybrid mem... 相似文献
133.
In order to restrain the mid-spatial frequency error in magnetorheological finishing (MRF) process, a novel part-random path is designed based on the theory of maximum entropy method (MEM). Using KDMRF-1000F polishing machine, one flat work piece (98 mm in diameter) is polished. The mid-spatial frequency error in the region using part-random path is much lower than that by using common raster path. After one MRF iteration (7.46 min), peak-to-valley (PV) is 0.062 wave (1 wave =632.8 nm), root-mean-square (RM... 相似文献
134.
JuYing Wu ChengXi Zhou QingWen Zhu EnRong Li Ge Dai Long Ba YuHong Huang Jun Mei 《中国科学E辑(英文版)》2009,52(12):3497-3503
The ruthenium oxide nanoparticles with size less than 20 nm were fabricated by annealing the metallic ruthenium nanoparticles
in air, which were synthesized by using the thermal reduction in the polyol solution. The rutile structure of the ruthenium
oxide was proved by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The oxide has
good electron conductivity. The surface of the ruthenium oxide was modified by a vinyl silane coupling agent. The assembling
of the silane to the oxide surface was proved by Infrared (IR) absorption spectroscopy. By mixing the nanoparticles with poly(methylvinylsiloxane)
(PMVS) silicone rubber, a composite filled with dispersive conducting phase was fabricated. The temperature dependent conductivity
shows that the electron transportation through composite is mainly dominated by tunneling. The measurement of piezoresistance
shows that the composite at low strain has high piezoresistance repeatability. The 3D reconstruction images of the composite
filled with carbon black or ruthenium oxide show that the aggregation of the nanoparticles differs much for two composites.
The narrow distribution range of the particle size was thought to be the main factor for the high piezoresistance recurrence. 相似文献
135.
通过分析比较,找出制备硅酸盐富锌涂料的理想配方。试验检测表明:该涂层具有良好的附着力,较强防腐性能等。是一种很有发展潜力的防腐蚀涂料。 相似文献
136.
137.
In this paper, a new liquid membrane technique, hollow fiber renewal liquid membrane (HFRLM), is presented, which is based on the surface renewal theory, and integrates the advantages of fiber membrane extraction, liquid film permeation and other liquid membrane processes. The results from the system of CuSO4+D2EHPA in kerosene+HCl show that the HFRLM process is very stable. The liquid membrane is renewed constantly during the process, the direct contact of organic droplets and aqueous phase provides large mass transfer area. These effects can significantly reduce the mass transfer resistance in the lumen side. Then the mixture of feed phase and organic phase flowing through the lumen side gives a higher mass transfer rate than that of stripping phase and organic phase, because the aqueous layer diffusion of feed phase is the rate-controlling step. The overall mass transfer coefficient increases with increasing flow rates and D2EHPA concentration in the organic phase, and with decreasing initial copper concentration in the feed phase. The overall mass transfer coefficient also increases with increasing pH in the feed phase, and reaches a maximum value at pH of 4.44, then decreases. Also, there is a favorable w/o volume ratio of 20:1 to 30:1 for this process. Compared with hollow fiber supported liquid membrane and hollow fiber membrane extraction processes, HFRLM process has a high mass transfer rate. Mathematical model for the HFRLM process based on the surface renewal theory is developed. The calculated results are in good agreement with experimental results under the conditions studied. 相似文献
138.
139.
本文对反应注射充模过程中的铺展流、射流、绕流和气泡的特性进行了分析研究,并讨论了模具浇口结构及位置对充模的影响,给出了制品的设计方法。 相似文献
140.
Monte Carlo simulations were used to investigate the compatibilizing effects of diblock copolymers in A/B/A-B diblock copolymer ternary blends and triblock copolymers in A/B/triblock copolymer ternary blends, respectively. The volume fraction of homopolymer A was 19% and was the dispersed phase. The simulation results show that diblock copolymers with longer A-blocks are more efficient as compatibilizers, and symmetric triblock copolymers with a shorter middle block length are easily able to bridge each other through the association of the end blocks. This kind of triblock copolymers have relatively high ability to retard phase separation as compatibilizers. 相似文献