全文获取类型
收费全文 | 26859篇 |
免费 | 2150篇 |
国内免费 | 1785篇 |
专业分类
电工技术 | 1537篇 |
技术理论 | 1篇 |
综合类 | 3087篇 |
化学工业 | 2273篇 |
金属工艺 | 1146篇 |
机械仪表 | 2990篇 |
建筑科学 | 2082篇 |
矿业工程 | 628篇 |
能源动力 | 807篇 |
轻工业 | 1074篇 |
水利工程 | 622篇 |
石油天然气 | 585篇 |
武器工业 | 177篇 |
无线电 | 1785篇 |
一般工业技术 | 3469篇 |
冶金工业 | 1138篇 |
原子能技术 | 161篇 |
自动化技术 | 7232篇 |
出版年
2024年 | 93篇 |
2023年 | 286篇 |
2022年 | 471篇 |
2021年 | 561篇 |
2020年 | 736篇 |
2019年 | 654篇 |
2018年 | 647篇 |
2017年 | 793篇 |
2016年 | 897篇 |
2015年 | 949篇 |
2014年 | 1736篇 |
2013年 | 1925篇 |
2012年 | 1941篇 |
2011年 | 1867篇 |
2010年 | 1448篇 |
2009年 | 1689篇 |
2008年 | 1638篇 |
2007年 | 1863篇 |
2006年 | 1653篇 |
2005年 | 1412篇 |
2004年 | 1126篇 |
2003年 | 995篇 |
2002年 | 825篇 |
2001年 | 775篇 |
2000年 | 640篇 |
1999年 | 515篇 |
1998年 | 453篇 |
1997年 | 370篇 |
1996年 | 307篇 |
1995年 | 264篇 |
1994年 | 224篇 |
1993年 | 169篇 |
1992年 | 156篇 |
1991年 | 118篇 |
1990年 | 112篇 |
1989年 | 105篇 |
1988年 | 83篇 |
1987年 | 44篇 |
1986年 | 26篇 |
1985年 | 27篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 20篇 |
1981年 | 13篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1964年 | 8篇 |
1963年 | 9篇 |
1961年 | 8篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
41.
Behaviour of a series of lubricant oils and the effect of a non stoichiometric inorganic compound, as solid extreme pressure additive, on rolling fatigue life are studied using the rolling four-ball accelerated service simulation test proposed by Barwell and Scott. The results show, in all tested cases, the remarkable efficacy of this type of additive. The Total Acidity Number (tan) was found to increase with performance time for the case of the base lubricant, while for the oils with additives, it remained at its constant low value. This led to a proposal of a possible mechanism of the additive performance in the rolling process. 相似文献
42.
Using the focal mechanisms of earthquakes taken place from 1950 to 1996, the type and direction of principal strains were established, which made it possible to determine the volume stress-strain state of the south-east flank of the Baikal rift zone on the basis of the inverse problem solution. The variations in the stress-strain fields and spatial distribution of the stored potential energy density were found by the displacements of the daylight surface points in Tunkinsk geodetic proving ground in 1975 - 1986. 相似文献
43.
In the paper, a model typical for contact situations of automotive brakes is established based on the method of movable cellular automata. The processes taking place at local contacts in an automotive brake system are analysed. Based on microscopic and micro-analytical observations, the following contact situations were simulated: (i) a couple of ferritic steel against pearlitic steel, both covered by an oxide layer mixed with graphite nanoparticles and (ii) the same situation but without oxide layers. The results of calculated mean coefficients of friction of the oxide-on-oxide contact correspond well to expected values for a real braking system, whereas steel-on-steel contact are twice as high. This allows one to make some conclusions; for example, oxide formation will take place more quickly than friction layer elimination, and finally this is responsible for the stabilisation of the coefficient of friction. 相似文献
44.
The short contact time dissolution of vitrinite and inertinite concentrates of an Australian bituminous coal was studied under isothermal conditions with tetralin as solvent. The reactivity of the two maceral types and the yields and nature of the products were determined for a range of reaction temperatures (400, 420 and 440 °C) and reaction times (2–20 min). The dissolution of vitrinite proceeded at a significantly greater rate than for inertinite and was associated with greater selectivity to soluble non-gaseous products. At very short reaction times (2 min), the vitrinite underwent solubilizing reactions to yield products of higher molecular weight and greater oxygen functionality than was the case for inertinite, for which changes in the chemical nature of the products were negligible over the range of conditions studied. At longer reaction times (5 min), the composition of the vitrinite-derived products was similar to that of the inertinite-derived products. 相似文献
45.
A numerical solution of the inverse problem of the gravitational field at a single point is obtained using six field elements
for a point, a spherical cap, a differential spherical sector and a vertical segment. In the system of six equations obtained,
the unknowns are the mass of the body, the depth of its center, and the second, third, and fourth degree moments. The accuracy
of the solution of this system is ten times higher than when using three field elements.
__________
Translated from Izmeritel’naya Tekhnika, No. 5, pp. 3–8, May, 2007. 相似文献
46.
简述了我国钨矿业概况、现有采选技术水平及钨矿加工利用率 ;从资源配置出发 ,阐述了钨矿业发展存在的几个主要问题 ,并且针对性地提出了可持续发展的几点建议。 相似文献
47.
Roberto Leoni Bruno Buonomo Gabriella Castellano Francesco Mattioli Guido Torrioli Luciana Di Gaspare Florestano Evangelisti 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,520(1-3):44-47
We discuss the performance, of a normal metal hot electron bolometer (NHEB) that we have measured at 0.3 K. We found that the noise equivalent power was limited by the amplifier noise. To improve the NHEB power response and to make it more robust and reliable we propose to substitute the normal metal with heavily doped silicon. The heavily doped silicon behaves like a metal with lower carrier concentration and has a smaller electron–phonon thermal coupling. We have fabricated superconductor-doped silicon-superconductor contacts (S-Sm-S) and we have used them as thermometers and coolers. 相似文献
48.
H. M. Park M. C. Sung 《International journal for numerical methods in engineering》2004,60(12):1949-1968
The Karhunen–Loève Galerkin procedure is employed to solve an inverse radiation problem of determining the time‐varying strength of a heat source, which mimics flames in a furnace, from temperature measurements in three‐dimensional participating media where radiation and conduction occur simultaneously. The inverse radiation problem is solved through the minimization of a performance function, which is expressed by the sum of square residuals between calculated and observed temperature, using a conjugate gradient method. Through the Karhunen–Loève Galerkin procedure, one can represent the system dynamics with a minimum degree of freedom, and consequently the amount of computation required in the solution of the inverse problem is reduced drastically when the present technique is adopted. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
49.
LW15-252型SF_6断路器存在的问题和对策 总被引:1,自引:1,他引:0
国产SF6断路器已在电力系统中得到了广泛的应用,随着时间的推移,这种断路器存在的问题也逐渐地暴露出来。笔者介绍了LW15-252型SF6断路器在实际运用中存在的问题和采取的对策。 相似文献
50.
A method is considered to solve a conditional optimization problem with a linear-fractional objective function over permutations.
The performance of sub algorithms to solve this problem is evaluated. The practical efficiency of the algorithm is analyzed
by conducting numerical experiments.
__________
Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 133–146, July–August 2007. 相似文献