全文获取类型
收费全文 | 76387篇 |
免费 | 7876篇 |
国内免费 | 5776篇 |
专业分类
电工技术 | 5805篇 |
技术理论 | 3篇 |
综合类 | 6284篇 |
化学工业 | 14472篇 |
金属工艺 | 5324篇 |
机械仪表 | 5994篇 |
建筑科学 | 2959篇 |
矿业工程 | 1751篇 |
能源动力 | 6285篇 |
轻工业 | 2856篇 |
水利工程 | 5272篇 |
石油天然气 | 4255篇 |
武器工业 | 717篇 |
无线电 | 5902篇 |
一般工业技术 | 10882篇 |
冶金工业 | 3599篇 |
原子能技术 | 1728篇 |
自动化技术 | 5951篇 |
出版年
2024年 | 374篇 |
2023年 | 1080篇 |
2022年 | 1912篇 |
2021年 | 2270篇 |
2020年 | 2440篇 |
2019年 | 2099篇 |
2018年 | 2005篇 |
2017年 | 2600篇 |
2016年 | 2772篇 |
2015年 | 2829篇 |
2014年 | 3944篇 |
2013年 | 4798篇 |
2012年 | 4902篇 |
2011年 | 5935篇 |
2010年 | 4162篇 |
2009年 | 4540篇 |
2008年 | 4172篇 |
2007年 | 5073篇 |
2006年 | 4771篇 |
2005年 | 4163篇 |
2004年 | 3601篇 |
2003年 | 3130篇 |
2002年 | 2573篇 |
2001年 | 2248篇 |
2000年 | 1957篇 |
1999年 | 1644篇 |
1998年 | 1405篇 |
1997年 | 1169篇 |
1996年 | 1045篇 |
1995年 | 937篇 |
1994年 | 817篇 |
1993年 | 639篇 |
1992年 | 504篇 |
1991年 | 338篇 |
1990年 | 301篇 |
1989年 | 245篇 |
1988年 | 163篇 |
1987年 | 113篇 |
1986年 | 75篇 |
1985年 | 41篇 |
1984年 | 57篇 |
1983年 | 40篇 |
1982年 | 28篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 20篇 |
1977年 | 5篇 |
1975年 | 5篇 |
1959年 | 26篇 |
1951年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
在连铸生产铝镇静钢时,水口絮流一直是困扰工程技术人员的一个难题.从絮流的原因入手,分析了Al2O3生成的控制.并介绍了几种钢水钙化的方法,从中比较出用复合造渣材料来解决浇铸铝镇静钢的优点. 相似文献
192.
将空气中烧成的镍导体用于散热制冷片制作工艺中,可降低成本,提高合格率。通过实验得到的最佳值为:镍导体中4号玻璃(SiO2>30,B2O3>10,PbO<55,TiO2少许)的含量4.5%,化学镀镍时间50min,方阻47.5mΩ/□,附着力8.1N/mm2。 相似文献
193.
油酸乙二醇单酯在基础油与水界面上形成吸附膜的研究 总被引:1,自引:0,他引:1
以油酸和乙二醇为原料,在酸性催化剂作用下,用硼酸间接酯化法合成了润滑油油性油酸乙二醇单酯,用界面张力仪测定了单酯含量的矿物油的界面张力。用量小二乘法求得油中油酸乙二醇单脂的浓度与油对水界面张力关系的回归方程。依据所求的回归方程和Gibbs公式计算出油酸乙二醇单脂在油与水界面上形成吸附膜时的最低浓度。 相似文献
194.
Michael E. G. Ferguson Peter L. Spedding 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):262-278
Experimental data for air–water two-phase co-current flow in two different pipe diameters were used to test the prediction of pressure drop by a number of existing theories and correlations. Several models are shown to be useful for prediction, particularly with the stratified regimes which have proved difficult to handle in the past. The model suggested by Olujic proved to be of particular value. 相似文献
195.
热处理WO3电变色膜稳定性研究 总被引:1,自引:0,他引:1
采用电子束蒸发淀积WO3薄膜。根据已有的WO3薄膜脱水过程结论而选择适当温度对薄膜进行退火处理。在大量含水的和不含水的两类Li^+电解质中进行比较性着色和消色循环实验,表明在290℃以下热退火处理能明显增加WO3薄膜在含水 电解质中的循环寿命。 相似文献
196.
钛酸铅系薄膜的热释电性能及其应用 总被引:10,自引:1,他引:9
叙述了钛酸铅系薄膜的热释电原理,介绍了国际上近几年钛酸铅系薄膜材料、制备工艺及热释电性能,并与块状陶瓷材料进行了比较,分析表明钛酸铅系薄膜具有优良的热释电性能及可观的应用前景。 相似文献
197.
Wang Jia-lu Department of Engineering Mechanics Tsinghua University Beijing P.R.ChinaSun Mao Lian Qi-xiang Institute of Fluid Mechanics Beijing University of Aeronautics Astronautics Beijing P.R.China 《水动力学研究与进展(B辑)》1993,(4)
The starting flow around a uniformly accelerated circular cylinder is investigatedby flow visualization techncque and solving N-S equations numerically in detail.The results ofthe starting flow are similar with those of the impulsively started one.At lower Re_α,numbers the“phenomenon a”is revealed;the“phenomenon β”appears at higher Re_α numbers,but withonly one secondary vortex.At the early stage of the starting vortex formation,the flow islaminar;at the later stage,the flow transforms into turbulent flow.The velocity distribution inthe flow field is measured with the multiwires installment.The calculational results are comparedwith the results of experiment,and both are in agreement with each other. 相似文献
198.
NUMERICALMODELFORDYNAMICSIMULATIONOFTRAFFICFLOWWuZheng;ZengLi-nong(DepartmentAppliedMechanics,FudanUniversity,Shaghai200433,P... 相似文献
199.
Cu, In and Se have been codeposited in thin films by potentiostatic one-step electrodeposition. The as-deposited material has shown direct optical transitions attributable to the CuInSe2 semiconductor, but also additional absorption corresponding to another semimetallic phase. The secondary phases are selenium and copper selenide compounds which have been determined by composition measurements. In order to eliminate the semimetallic phases and to improve the semiconductor behaviour of the electrodeposited material, thermal and chemical treatments have been performed. After heat-treatment of the samples at 400°C in flowing argon, elemental selenium loss has been detected together with an enhancement of the allowed direct optical transition. The subsequent chemical etching of the layers in a KCN solution has showed to be successful in eliminating the copper selenide phases which were responsible of the remaining sub-bandgap absorption. 相似文献
200.
Wu Ting M. Badaye T. Morishita N. Koshizuka S. Tanaka 《Journal of Superconductivity》1996,9(6):637-645
Recently, superconducting Nd1Ba2Cu3Oy (Ndl23) thin films with high superconducting transition temperature (T
c) have been successfully fabricated at our institute employing the standard laser ablation method. In this paper, we report the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half-integer number of thec-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. This result is supported byI-V STS measurements. The surface morphology of the Nd123 thin films is compared with that of thec-axis-oriented Y1Ba2Cu3Sy thin films. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive. The results of STS measurements together with the fact that we are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films. 相似文献