全文获取类型
收费全文 | 53459篇 |
免费 | 4383篇 |
国内免费 | 1954篇 |
专业分类
电工技术 | 4148篇 |
技术理论 | 1篇 |
综合类 | 5858篇 |
化学工业 | 2628篇 |
金属工艺 | 1469篇 |
机械仪表 | 5181篇 |
建筑科学 | 19488篇 |
矿业工程 | 2625篇 |
能源动力 | 1562篇 |
轻工业 | 2478篇 |
水利工程 | 3766篇 |
石油天然气 | 1631篇 |
武器工业 | 208篇 |
无线电 | 1659篇 |
一般工业技术 | 3175篇 |
冶金工业 | 2059篇 |
原子能技术 | 142篇 |
自动化技术 | 1718篇 |
出版年
2024年 | 236篇 |
2023年 | 596篇 |
2022年 | 1215篇 |
2021年 | 1396篇 |
2020年 | 1493篇 |
2019年 | 1142篇 |
2018年 | 1204篇 |
2017年 | 1412篇 |
2016年 | 1569篇 |
2015年 | 1776篇 |
2014年 | 3726篇 |
2013年 | 2516篇 |
2012年 | 3931篇 |
2011年 | 4161篇 |
2010年 | 3349篇 |
2009年 | 3554篇 |
2008年 | 3036篇 |
2007年 | 3969篇 |
2006年 | 3561篇 |
2005年 | 2996篇 |
2004年 | 2296篇 |
2003年 | 1932篇 |
2002年 | 1734篇 |
2001年 | 1425篇 |
2000年 | 1205篇 |
1999年 | 924篇 |
1998年 | 768篇 |
1997年 | 612篇 |
1996年 | 524篇 |
1995年 | 389篇 |
1994年 | 299篇 |
1993年 | 190篇 |
1992年 | 149篇 |
1991年 | 98篇 |
1990年 | 75篇 |
1989年 | 78篇 |
1988年 | 46篇 |
1987年 | 39篇 |
1986年 | 28篇 |
1985年 | 31篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 21篇 |
1981年 | 5篇 |
1980年 | 26篇 |
1979年 | 18篇 |
1957年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
B. Bereqvist 《Strain》1987,23(1):7-13
The design and performance of precision bending equipment for testing straight beams with constant rectangular section under a pure bending moment is described. Part 1 deals with the loading arrangements and Part 2 with the rig for measuring beam deflection. The methods for recording deflection of strain gauges applied on the beam have been described elsewhere.1–4
The reactions to the deadweight gravity loads are taken via ball bearings. The total bending moment inaccuracy, i.e. the sum of estimated systematic errors and random errors, the latter expressed as the 2Ga confidence interval about the mean (2Gcim ), is about ± 25 x. 10-4% , for 23 tests with a steel beam with 15 mm × 75 mm cross sectional dimensions, loaded to 1-1.5 mm/m strain.
The measuring rig stands on the beam via hardened and polished spherical segment feet and uses a capacitive transducer system with less than 5nm resolution. Various application tasks are described. The total inaccuracy of the measured deflection, i.e. apart from bending moment inaccuracy, is about ± 35 times 104% for about 10 reproduced, not repeated, tests with the same steel beam. The deflection for such a beam is of the order of 2 to 4 mm. 相似文献
The reactions to the deadweight gravity loads are taken via ball bearings. The total bending moment inaccuracy, i.e. the sum of estimated systematic errors and random errors, the latter expressed as the 2Ga confidence interval about the mean (2G
The measuring rig stands on the beam via hardened and polished spherical segment feet and uses a capacitive transducer system with less than 5nm resolution. Various application tasks are described. The total inaccuracy of the measured deflection, i.e. apart from bending moment inaccuracy, is about ± 35 times 10
23.
V. Anjos M.J.V. Bell E.F. da Silva Jr. R.W.A. Franco I.A. Esquef 《Microelectronics Journal》2005,36(11):977-980
In this paper we report the use of photothermal techniques such as Thermal lens (TL) spectrometry, Photoacoustic and heat capacity, ρcp, to determine the thermo-optical parameters, such as thermal conductivity (K), thermal diffusivity (D), specific heat (cp) and the optical path dependence with temperature (ds/dT), of an undoped polycrystalline 3C-SiC. To our knowledge, this is the first time that Thermal lens technique is used for wide band-gap systems. Results obtained for the polycrystalline sample with TL technique indicates that ds/dT is negative at room temperature. Moreover, the obtained values of thermal diffusivity and thermal conductivity are in good agreement with that found in the literature, indicating that the phototermal techniques can be used to obtain the referred parameters in circumstances where other techniques cannot be used, for example, in harsh environments. 相似文献
24.
压密注浆及其在地基加固中的应用 总被引:1,自引:0,他引:1
在简单介绍了压密注浆工法的加固机理、影响被加固土体强度的因素的基础上,结合工程实例介绍了压缩注浆工法的工程应用情况。 相似文献
25.
随着电容测量技术的迅速发展,电容传感器在非电量测量和自动检测中得到广泛应用,但它在使用过程中也存在一些问题,针对在使用电容传感器过程中存在的几个问题,从电容传感器的原理和工作过程两个方面进行了讨论,并提出行之有效的处理方法。 相似文献
26.
The saturation capacity of n-alkanes in CHA, AFX and ERI zeolites, that consist of cages separated by windows, decreases with increasing carbon number. The major aim of the present communication is to demonstrate the possibility of separating n-alkane mixtures relying on differences in saturation capacities. To investigate this possibility, Configurational-Bias Monte Carlo simulations for adsorption of C3–nC6, nC4–nC6, and nC5–nC6 mixtures in CHA, AFX and ERI were carried out for equimolar bulk fluid phase. These mixture simulations show that for operation at fluid phase fugacities below about 1 MPa, the adsorbed phase in equilibrium with the bulk vapor phase is predominantly the alkane with the longer chain length, i.e. nC6. However, for operation at pressures in excess of 1 MPa, the adsorbed phase in equilibrium with the bulk liquid phase is richer in the component with the smaller chain length. In some cases, the nC6 is practically excluded from the zeolite. 相似文献
27.
The present study is an investigation on the behaviors of concrete-filled thin-walled steel tubular members subjected to combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. ABAQUS software is used in this paper for the finite element analysis (FEA). A comparison of results calculated using this modeling shows generally good agreement with test results. The FEA modeling is then used to investigate the influence of important parameters that determine the ultimate strength of the composite members under combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. The parametric studies provide information for the development of formulae for calculating the ultimate strength of the composite members subjected to combined loading. 相似文献
28.
浅谈门式刚架轻型钢结构厂房中抗风柱的设置 总被引:1,自引:0,他引:1
通过对抗风柱上下端的节点几种形式进行分析比较,提出建议性的节点连续方式。 相似文献
29.
金沙江防洪(库容)规划的探讨 总被引:1,自引:0,他引:1
在分析长江灾害洪水特征的基础上,全面深入地研究了全沙江水库的防洪库客、防洪目标、防洪特点和调度原则,并对防洪库容的作用进行了估算和分析。从多方面比较了虎跳峡高坝方案与低坝方案,结果表明:高坝方案的效益明显高于低坝方案,而两者所需付出的代价相差不大。 相似文献
30.
芳烃抽提装置技术改造 总被引:3,自引:0,他引:3
由于中国石化锦西石化分公司600kt/a连续重整装置的建设,芳烃抽提装置的原料由原来的脱戊烷油变为Ce组分。为此,对抽余油水洗塔和芳烃分离部分的苯塔塔盘,以及苯塔塔顶和塔底抽出部分进行了改造,更换部分机泵和增加变频泵,并将常规仪表改为DCS控制。改造后装置实现一次开车成功,生产出合格产品。抽余油中总芳烃含量小于0.1%,苯回收率达到99%以上。 相似文献