全文获取类型
收费全文 | 262634篇 |
免费 | 26604篇 |
国内免费 | 15146篇 |
专业分类
电工技术 | 15970篇 |
技术理论 | 4篇 |
综合类 | 29119篇 |
化学工业 | 27942篇 |
金属工艺 | 26631篇 |
机械仪表 | 22446篇 |
建筑科学 | 35895篇 |
矿业工程 | 12030篇 |
能源动力 | 8136篇 |
轻工业 | 12684篇 |
水利工程 | 9739篇 |
石油天然气 | 12927篇 |
武器工业 | 3086篇 |
无线电 | 14290篇 |
一般工业技术 | 34682篇 |
冶金工业 | 13262篇 |
原子能技术 | 3611篇 |
自动化技术 | 21930篇 |
出版年
2024年 | 1068篇 |
2023年 | 3194篇 |
2022年 | 6878篇 |
2021年 | 7767篇 |
2020年 | 7844篇 |
2019年 | 6792篇 |
2018年 | 6605篇 |
2017年 | 8529篇 |
2016年 | 9355篇 |
2015年 | 9783篇 |
2014年 | 15774篇 |
2013年 | 15766篇 |
2012年 | 19425篇 |
2011年 | 20268篇 |
2010年 | 15544篇 |
2009年 | 15995篇 |
2008年 | 14431篇 |
2007年 | 18064篇 |
2006年 | 16179篇 |
2005年 | 13534篇 |
2004年 | 11392篇 |
2003年 | 9834篇 |
2002年 | 8332篇 |
2001年 | 6921篇 |
2000年 | 6147篇 |
1999年 | 5179篇 |
1998年 | 4096篇 |
1997年 | 3737篇 |
1996年 | 3144篇 |
1995年 | 2699篇 |
1994年 | 2205篇 |
1993年 | 1615篇 |
1992年 | 1436篇 |
1991年 | 1033篇 |
1990年 | 864篇 |
1989年 | 828篇 |
1988年 | 578篇 |
1987年 | 353篇 |
1986年 | 252篇 |
1985年 | 139篇 |
1984年 | 151篇 |
1983年 | 76篇 |
1982年 | 90篇 |
1981年 | 86篇 |
1980年 | 82篇 |
1979年 | 73篇 |
1978年 | 23篇 |
1975年 | 23篇 |
1964年 | 16篇 |
1959年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Stepanov G. V. Kharchenko V. V. Babutskii A. I. Romanov S. V. Feofentov N. A. Kravchenko I. V. 《Strength of Materials》2004,36(3):321-326
The procedure for calculating the life of header – steam generator connector weld joints is proposed. It allows for running out the material plasticity reserve upon static cyclic elastoplastic loading as well as operating conditions, local stress concentrations, and residual stresses after welding. 相似文献
102.
Hung‐Yee Shu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(3):273-280
Liquid–liquid two‐phase epoxidation from cyclohexene and cyclooctene in aqueous potassium peroxymonosulfate (commercially available as Oxone®) solution was studied as an application in pollution prevention. To avoid potential emissions of volatile organic compounds an aqueous solution was employed to replace the usual chlorinated solvents used in epoxide production. A droplet column reactor and stirred tank reactor were used to investigate two‐phase synthesis of epoxide. An aqueous Oxone® solution was used to oxidize a dispersion of alkene droplets and form epoxide. The study of aqueous epoxidation in both reactors showed that the epoxidation of alkenes can be represented as a first order reaction with respect to alkene. The salting out effect of Oxone® concentration was studied in both reactors and found to be very similar at optimal conditions. In comparing the two reactors, it was found that the droplet column reactor produces larger quantities of product per unit reactor volume for the same reaction time. The objective of this study is to provide an alternative reactor design and synthesis route that can meet pollution prevention goals. Copyright © 2004 Society of Chemical Industry 相似文献
103.
John E. Sohn 《The Journal of Adhesion》1985,19(1):15-27
Enhanced matrix-filler adhesion is realized after filler treatment with a surface treatment process. The hydrosol/coupling agent treatment was applied to a wide range of inorganic and organic fillers, and adhesion to a variety of matrix resins was improved. Scanning Electron Microscopy (SEM) was used to determine the locus of failure in the filled systems. The locus of failure shows the relative degree of adhesion between the filler and the polymer matrix. Significant improvement in adhesion in humid environments is also observed. 相似文献
104.
Yu. A. Radin I. A. Grishin T. S. Kontorovich O. B. Panshina A. V. Chugin 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2006,40(2):113-119
Problems arising with connecting the second exhaust-heat boiler to the first exhaust-heat boiler under load in the case of
flow circuits of combined-cycle plants of type PGU-450 are considered. Similar problems exist for two-boiler single-turbine
units of type PGU-325 and for two-boiler single-turbine units of traditional steampower plants with an output of 200–300 MW
upon connection of the second furnace of a two-furnace boiler to the operating first furnace. Analysis of the temperature-induced
stressed state and of the cyclic strength of thick-walled elements of the steam-water conduit of PGU-450 and of two-furnace
boilers of two-boiler single-turbine units with an output of 200–300 MW (the check valve, the inlet header of the water economizer)
is used for determining the steam temperature differences in the high-pressure conduits to the steam turbine and the order
of connection of the second exhaust-heat boiler to the operating fist one. Modes of enabling a two-boiler single-turbine unit
of a combined-cycle plant, which are most “rigid” from the standpoint of thermal strength, are determined.
__________
Translated from élektricheskie Stantsii, No. 2, February 2006, pp. 11–17. 相似文献
105.
106.
Y. MURAKAMI K. TAKAHASHI R. KUSUMOTO 《Fatigue & Fracture of Engineering Materials & Structures》2003,26(6):523-531
ABSTRACT The fatigue crack growth behaviour of 0.47% carbon steel was studied under mode II and III loadings. Mode II fatigue crack growth tests were carried out using specially designed double cantilever (DC) type specimens in order to measure the mode II threshold stress intensity factor range, ΔKIIth. The relationship ΔKIIth > ΔKIth caused crack branching from mode II to I after a crack reached the mode II threshold. Torsion fatigue tests on circumferentially cracked specimens were carried out to study the mechanisms of both mode III crack growth and of the formation of the factory‐roof crack surface morphology. A change in microstructure occurred at a crack tip during crack growth in both mode II and mode III shear cracks. It is presumed that the crack growth mechanisms in mode II and in mode III are essentially the same. Detailed fractographic investigation showed that factory‐roofs were formed by crack branching into mode I. Crack branching started from small semi‐elliptical cracks nucleated by shear at the tip of the original circumferential crack. 相似文献
107.
以工业偏钛酸、硫酸锌、氨水为主要原料,用直接沉淀法并进行热处理得到钛酸锌粉体,并用XRD对产物成分进行了检测。结果表明,不同的锌钛比对钛酸锌(ZnO-TiO2)体系的成分有较大影响。 相似文献
108.
A. Yu. Luchka 《Cybernetics and Systems Analysis》2003,39(6):880-888
A modified variational-gradient method is proposed and substantiated for quasilinear operator equations in a Hilbert space. 相似文献
109.
Chuanju Xu 《Journal of scientific computing》2006,27(1-3):495-505
A stabilization method for the spectral element computation of incompressible flow problems is investigated. It is based on a filtering procedure which consists in filtering the velocity field by a spectral vanishing Helmholtz-type operator at each time step. Relationship between this filtering procedure and SVV-stabilization method, introduced recently in [JCP, 2004, 196(2), p680], is established. A number of numerical examples are presented to show the accuracy and stabilization capability of the method. 相似文献
110.
This paper studies a Kansas Department of Transportation welded plate girder bridge that developed fatigue cracks at small web gaps close to the girder top flange. Repair had been previously performed by softening the connection plate end with a slot retrofit, but cracks were recently found to have reinitiated at some of the repaired details and are again propagating. A comprehensive finite-element method study was performed to investigate the cracking behavior observed in the bridge and to recommend appropriate measures for future bridge retrofit. The analytical results show that stresses developed at the top flange web gaps could exceed yielding under the loading of an HS15 fatigue truck. The current slot repair used in the bridge was found to have introduced higher magnitude fatigue stresses in the web gap. To achieve a permanent repair of the bridge, it is recommended that a welded connection plate to flange attachment be used during future bridge retrofit. The web gap details should be able to withstand unlimited number of load cycles once this additional repair is performed. 相似文献