全文获取类型
收费全文 | 151976篇 |
免费 | 1968篇 |
国内免费 | 656篇 |
专业分类
电工技术 | 3117篇 |
综合类 | 187篇 |
化学工业 | 24108篇 |
金属工艺 | 5783篇 |
机械仪表 | 4954篇 |
建筑科学 | 4418篇 |
矿业工程 | 378篇 |
能源动力 | 3927篇 |
轻工业 | 17309篇 |
水利工程 | 1142篇 |
石油天然气 | 633篇 |
武器工业 | 5篇 |
无线电 | 20512篇 |
一般工业技术 | 28878篇 |
冶金工业 | 23796篇 |
原子能技术 | 2348篇 |
自动化技术 | 13105篇 |
出版年
2019年 | 836篇 |
2018年 | 1086篇 |
2017年 | 1135篇 |
2016年 | 1272篇 |
2015年 | 1067篇 |
2014年 | 1805篇 |
2013年 | 6580篇 |
2012年 | 3196篇 |
2011年 | 4619篇 |
2010年 | 3602篇 |
2009年 | 4156篇 |
2008年 | 4652篇 |
2007年 | 4916篇 |
2006年 | 4354篇 |
2005年 | 4111篇 |
2004年 | 4004篇 |
2003年 | 3902篇 |
2002年 | 3932篇 |
2001年 | 3983篇 |
2000年 | 3745篇 |
1999年 | 3693篇 |
1998年 | 6641篇 |
1997年 | 5234篇 |
1996年 | 4463篇 |
1995年 | 3714篇 |
1994年 | 3360篇 |
1993年 | 3186篇 |
1992年 | 2785篇 |
1991年 | 2692篇 |
1990年 | 2630篇 |
1989年 | 2614篇 |
1988年 | 2460篇 |
1987年 | 2169篇 |
1986年 | 2115篇 |
1985年 | 2560篇 |
1984年 | 2319篇 |
1983年 | 2197篇 |
1982年 | 2069篇 |
1981年 | 1993篇 |
1980年 | 1862篇 |
1979年 | 1876篇 |
1978年 | 1776篇 |
1977年 | 2088篇 |
1976年 | 2569篇 |
1975年 | 1586篇 |
1974年 | 1435篇 |
1973年 | 1457篇 |
1972年 | 1197篇 |
1971年 | 1117篇 |
1970年 | 951篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
J. Bartonicek W. Zaiss W. Hienstorfer H. Kocklemann F. Schckle 《Nuclear Engineering and Design》1995,153(2-3)
At GKN, fatigue monitoring of important components has been conducted since 1979. The monitoring methods depend on the mechanisms of damage; quasi-static loads are regarded as well as dynamic loads. The components were selected for monitoring on the basis of a system analysis. The data resulting from monitoring are used to optimise operation mode steadily. Experience shows that the use of monitoring data as input for fatigue assessment is the most realistic and cost-effective way. This fatigue assessment uses global and local sensitivity studies to evaluate the load-stress relation for each component. These relations can be programmed to produce stress vs. time curves. These are processed according to ASME rules to give a realistic fatigue usage. 相似文献
132.
The magnetization of a melt-texture growth (MTG) HTSC ring has been studied. It is shown that the magnetic field inside the ring is larger than the external field under a certain range of external magnetic fields. We have also investigated the magnetic field dependence of the response of a detective coil near a rotating superconducting ring. The responses of the MTG sample are different for different cooling methods. 相似文献
133.
Summary This paper presents the free vibration of thin doubly-curved shallow shells of rectangular planform. The study covers wide combinations of free, simply supported and clamped boundary conditions. Both positive and negative Gaussian curvatures (spherical and hyperbolic paraboloidal shells resepectively) are considered. Thepb-2 Ritz energy based approach, along with the in-plane and transverse deflections assumed in the form of a product of mathematically complete two-dimensional orthogonal polynomials and a basic function, is employed to model the vibratory characteristic of these shells. Numerical results have been established through convergence study and comparison with published data from the open literature. Extensive sets of new results for various ranges of aspect ratio, curvature ratio andx- andy-shallowness ratios have been presented for future reference. 相似文献
134.
W. F. Flanagan Lijun Zhong B. D. Lichter 《Metallurgical and Materials Transactions A》1993,24(3):553-559
A model is proposed to explain transgranular-stress corrosion cracking (T-SCC) in face-centered cubic (fcc) materials. Crack
propagation is shown to be anisotropic, in that growth near {110} < 001> is discontinuous due to crack arrest by dislocation
blunting whereas growth away from this growth orientation is continuous. For the former case, renucleation of arrested cracks
involves active dissolution of shear bands at the crack tip, which changes the stress state at Lomer-Cottrell locks, causing
them to fail by cleavage. Once the crack is nucleated, its instantaneous macroscopic crack-growth velocity is considered to
be comprised of multiple nucleation of microcracks with intervening arrests. This microcracking results from the interaction
of the stress fields from neighboring cracks which are forming simultaneously, the crack-opening constraint due to ligaments
which act as “bridges” behind the crack front, and the localized dissolution at the microcrack tip which affectsK
IC and leads to the “cobblestone” appearance. Experimental evidence and theoretical considerations are presented to support
the model. The system studied was Cu-25 at. pct Au in 0.6 M NaCl solution at potentials between 300 and 400 mV (sce), which
precludes hydrogen embrittlement.
This article is based on a presentation made in the symposium “Quasi-Brittle Fracture” presented during the TMS fall meeting,
Cincinnati, OH, October 21–24, 1991, under the auspices of the TMS Mechanical Metallurgy Committee and the ASM/MSD Flow and
Fracture Committee. 相似文献
135.
R. Borkowska J. Laskowski J. Płocharski J. Przyłuski W. Wieczorek 《Journal of Applied Electrochemistry》1993,23(10):991-995
Results for the performance of lithium/Mn02 batteries containing solid polymer electrolytes based on poly(ethylene oxide) blends with some acrylic derivatives are presented. The ionic conductivities of the electrolytes are promising for battery application. It was found, however, that interfacial phenomena impair the battery efficiency. Impedance spectroscopy shows resistive limitations at the anode interface of the batteries, caused either by formation of an electrically distinguishable resistive layer or by chemical interaction between the polymer and lithium, influencing, most probably, the kinetics of the lithium oxidation reaction. 相似文献
136.
137.
G.D. Wignall R.W. Hendricks W.C. Koehler J.S. Lin M.P. Wai E.L. Thomas R.S. Stein 《Polymer》1981,22(7):886-889
A series of small angle neutron scattering measurements on blends of normal polystyrene (PSH) and labelled (deuterated) polystyrene (PSD) have been made with concentrations of PSD from 5 to 50 mol %. It is shown that the single chain form factor of the polymer in bulk can be obtained from a single concentration measurement for any concentration of labelled molecules, providing the molecular weights of the parent and labelled molecules are the same and the molecular weight distributions are narrow. 相似文献
138.
Field surveys of a series of conjugated diunsaturated straight-chain primary alcohols, acetates, and aldehydes (dienes), including the 3,5-dode-cadienyl, 8,10-dodecadienyl, 3,5-tetradecadienyl, 8,10-tetradecadienyl, 9,11-tetradecadienyl, and 10,12-tetradecadienyl primary alcohols, acetates, and most aldehydes, and the related monounsaturated straight-chain primary alcohols, acetates, and aldehydes (monoenes), including the 3-dodecadienyl alcohol and acetates, attracted the following species from the title families. Diene attractants have been demonstrated for at least onePhyllonorycter sp.,Chionodes lugubrella (Fabr.),Leptostales ferruminaria (Zell.),Drepana bilineata (Pack.),Pyrausta fodinalis (Led.),Notocelia purpurissatana Heinr.,Phaneta alterana Heinr. Monoene attractants were demonstrated forHedya separatana (Kft.),Cydia fletcherana (Kft.),Barbara mappana Free.,Ancylis burgessiana (Zell.),Ancylis nubeculana Clem.,Evippe prunifoliella Cham.,Phlyctaenia coronata tertialis (Gn.), aChionodes sp., a Gelechiidae sp., and an unidentifiedPhyllonorycter sp. Replicated field experiments showed attraction-inhibition relationships for most species. Electroantennagram data are presented forLeptostales ferruminaria andDrepana bilineata. 相似文献
139.
Summary Starting with Z-2, 3-diamino-2-butenedinitrile as diamine component the synthesis of the low molecular N,N,O,O-chelate 3.Co and its ligand 3 is optimized. An easy synthesis of the chelate 8.Co covalently bound on macroreticular resins is presented. The chelates 8.Co are the most active heterogenous catalysts for the valence isomerization of quadricyclane to norbornadiene today. 相似文献
140.
Naphthalene-2,3-dicarboxaldehyde (NDA) has been investigated as a new derivatizing reagent for the electrochemical detection of tagged amino acids. Gradient elution allowed for the separation of 18 NDA-derivatized amino acids on an open tubular liquid chromatography column in less than 50 min. Gradient elution and electrochemical detection were found to be compatible. A detection limit of 36 amol was obtained for the asparagine-NDA derivative. The usefulness of this technique for quantitation was demonstrated by the analysis of the NDA-tagged hydrolysis products from bovine chymotrypsinogen. 相似文献