全文获取类型
收费全文 | 53203篇 |
免费 | 4798篇 |
国内免费 | 2414篇 |
专业分类
电工技术 | 3035篇 |
技术理论 | 5篇 |
综合类 | 3117篇 |
化学工业 | 9321篇 |
金属工艺 | 3142篇 |
机械仪表 | 3503篇 |
建筑科学 | 3688篇 |
矿业工程 | 1561篇 |
能源动力 | 1594篇 |
轻工业 | 3686篇 |
水利工程 | 859篇 |
石油天然气 | 2932篇 |
武器工业 | 432篇 |
无线电 | 6382篇 |
一般工业技术 | 7005篇 |
冶金工业 | 2828篇 |
原子能技术 | 575篇 |
自动化技术 | 6750篇 |
出版年
2024年 | 290篇 |
2023年 | 1083篇 |
2022年 | 1854篇 |
2021年 | 2655篇 |
2020年 | 1926篇 |
2019年 | 1759篇 |
2018年 | 1852篇 |
2017年 | 1905篇 |
2016年 | 1770篇 |
2015年 | 2367篇 |
2014年 | 2847篇 |
2013年 | 3316篇 |
2012年 | 3360篇 |
2011年 | 3899篇 |
2010年 | 3060篇 |
2009年 | 2950篇 |
2008年 | 2919篇 |
2007年 | 2583篇 |
2006年 | 2712篇 |
2005年 | 2116篇 |
2004年 | 1571篇 |
2003年 | 1383篇 |
2002年 | 1324篇 |
2001年 | 1144篇 |
2000年 | 1140篇 |
1999年 | 1183篇 |
1998年 | 963篇 |
1997年 | 815篇 |
1996年 | 727篇 |
1995年 | 613篇 |
1994年 | 491篇 |
1993年 | 342篇 |
1992年 | 286篇 |
1991年 | 235篇 |
1990年 | 191篇 |
1989年 | 179篇 |
1988年 | 118篇 |
1987年 | 92篇 |
1986年 | 64篇 |
1985年 | 53篇 |
1984年 | 47篇 |
1983年 | 38篇 |
1982年 | 33篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1976年 | 18篇 |
1975年 | 10篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Flotation is a water treatment alternative to sedimentation, and uses small bubbles to remove low-density particles from potable water and wastewater. The effect of zeta potential, bubble size and particle size on removal efficiency of the electro-flotation process was investigated because previous model-simulations indicated that these attributes are critical for high collision efficiency between micro-bubbles and particles. Solutions containing Al3+ as the metal ion were subjected to various conditions. The zeta potentials of bubbles and particles were similar under identical conditions, and their charges were influenced by metal ion concentration and pH. Maximum removal efficiency was 98 and 12% in the presence and absence of flocculation, respectively. Removal efficiency was higher when particle size was similar to bubble size. These results agree with modelling simulations and indicate that collision efficiency is greater when the zeta potential of one is negative and that of the other is positive and when their sizes are similar. 相似文献
3.
A new excimer laser annealing (ELA) process that uses a floating amorphous-Silicon (a-Si) thin film with a multichannel structure is proposed for high-performance poly-Si thin-film transistors (TFTs). The proposed ELA method produces two-dimensional (2-D) grain growth, which can result in a high-quality grain structure. The dual-gate structure was employed to eliminate the grain boundaries perpendicular to the current flow in the channel. A multichannel structure was adapted in order to arrange the grain boundary to be parallel to the current flow. The proposed poly-Si TFT exhibits high-performance electrical characteristics, which are a high mobility of 504 cm/sup 2//Vsec and a low subthreshold slope of 0.337 V/dec. 相似文献
4.
论文提出了一种混沌通信系统的噪音衰减算法,该算法利用混沌同步现象在接收端获得正确的噪音估计值,从而从接收信号中滤除噪音恢复出正确的信号。通过数值仿真试验表明该方法是可行的。 相似文献
5.
论文将Fermat素性检验的思想运用于不可约多项式的判断,给出了一个对于不可约判断问题的Monte Carlo 算法,分析了该算法的计算复杂度问题,并且给出了次数在200以内的检验结果。 相似文献
6.
7.
A mechanism of soldering of an aluminum alloy die casting to a steel die is proposed. A soldering critical temperature is
postulated, at which iron begins to react with aluminum to form an aluminum-rich liquid phase and solid intermetallic compounds.
The liquid joins the die with the casting upon solidification. The critical temperature is determined by the elements in both
the casting alloy and the die material and is equal to the solidus temperature of the resulting alloy. The critical temperature
is used to predict the onset of die soldering, and the local liquid fraction is related to the soldering tendency. Experiments
have been carried out to validate the concept and to determine the critical temperature for die soldering in an iron-aluminum
system. Thermodynamic calculations are used to determine the critical temperature and soldering tendency for the cases of
pure aluminum and a 380 alloy in a steel mold. Factors affecting the soldering tendency are discussed, and methods for reducing
die soldering are suggested. 相似文献
8.
9.
Jiao Nianyou Jiao Fangjie 《中国油气》2006,13(1):34-35
Recently, the special subject-development and application of rectilinear electromechanical pumping undertaken by Jianghan Petroleum Machinery Factory and China University of Petroleum (East China) Electromechanical Project Institute, which is the component of national key project for domestic petroleum equipment, new material development and application technology during the period of the 11 th Five-Year Plan, 相似文献
10.
针对目前石油钻采用清蜡绞车总体结构设计不合理以及实用性不强等技术难题,研制开发了自喷井电动清蜡绞车。该绞车的核心部件包括过载保护安全装置、牙嵌离合器轴套、自动/手动互换装置、计量装置以及密封装置。在清蜡绞车自动工作中,当清蜡刮刀遇到较大阻力时,清蜡绞车将接收到反馈信号,可实现智能停车,自动转换为手动状态,以便操作人员检查和排除故障,从而确保了操作的安全性,延长了设备的使用寿命。1000余台电动清蜡绞车的现场应用表明,该产品可以大大降低原油的开采成本,具有良好的经济效益和社会效益。 相似文献