全文获取类型
收费全文 | 244428篇 |
免费 | 2717篇 |
国内免费 | 430篇 |
专业分类
电工技术 | 4347篇 |
综合类 | 258篇 |
化学工业 | 39825篇 |
金属工艺 | 9417篇 |
机械仪表 | 7453篇 |
建筑科学 | 5642篇 |
矿业工程 | 1398篇 |
能源动力 | 5231篇 |
轻工业 | 25051篇 |
水利工程 | 2497篇 |
石油天然气 | 5105篇 |
武器工业 | 32篇 |
无线电 | 25321篇 |
一般工业技术 | 45201篇 |
冶金工业 | 46298篇 |
原子能技术 | 5968篇 |
自动化技术 | 18531篇 |
出版年
2021年 | 2134篇 |
2019年 | 2059篇 |
2018年 | 3544篇 |
2017年 | 3468篇 |
2016年 | 3738篇 |
2015年 | 2280篇 |
2014年 | 3950篇 |
2013年 | 10336篇 |
2012年 | 6256篇 |
2011年 | 8464篇 |
2010年 | 6659篇 |
2009年 | 7348篇 |
2008年 | 7726篇 |
2007年 | 7852篇 |
2006年 | 7002篇 |
2005年 | 6166篇 |
2004年 | 5905篇 |
2003年 | 5675篇 |
2002年 | 5758篇 |
2001年 | 5631篇 |
2000年 | 5438篇 |
1999年 | 5374篇 |
1998年 | 12764篇 |
1997年 | 9017篇 |
1996年 | 6951篇 |
1995年 | 5391篇 |
1994年 | 4795篇 |
1993年 | 4674篇 |
1992年 | 3709篇 |
1991年 | 3420篇 |
1990年 | 3629篇 |
1989年 | 3519篇 |
1988年 | 3339篇 |
1987年 | 2935篇 |
1986年 | 2967篇 |
1985年 | 3406篇 |
1984年 | 3251篇 |
1983年 | 2931篇 |
1982年 | 2757篇 |
1981年 | 2843篇 |
1980年 | 2747篇 |
1979年 | 2652篇 |
1978年 | 2709篇 |
1977年 | 2971篇 |
1976年 | 3861篇 |
1975年 | 2390篇 |
1974年 | 2255篇 |
1973年 | 2392篇 |
1972年 | 1982篇 |
1971年 | 1865篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
891.
Lada E.K. Jye-Chyi Lu Wilson J.R. 《Semiconductor Manufacturing, IEEE Transactions on》2002,15(1):79-90
To detect faults in a time-dependent process, we apply a discrete wavelet transform (DWT) to several independently replicated data sets generated by that process. The DWT can capture irregular data patterns such as sharp "jumps" better than the Fourier transform and standard statistical procedures without adding much computational complexity. Our wavelet coefficient selection method effectively balances model parsimony against data reconstruction error. The few selected wavelet coefficients serve as the "reduced-size" data set to facilitate an efficient decision-making method in situations with potentially large-volume data sets. We develop a general procedure to detect process faults based on differences between the reduced-size data sets obtained from the nominal (in-control) process and from a new instance of the target process that must be tested for an out-of-control condition. The distribution of the test statistic is constructed first using normal distribution theory and then with a new resampling procedure called "reversed jackknifing" that does not require any restrictive distributional assumptions. A Monte Carlo study demonstrates the effectiveness of these procedures. Our methods successfully detect process faults for quadrupole mass spectrometry samples collected from a rapid thermal chemical vapor deposition process 相似文献
892.
893.
Papaioannou G. Karabassi E.-A. Theoharis T. 《IEEE transactions on pattern analysis and machine intelligence》2002,24(1):114-124
The problem of re-assembling an object from its parts or fragments has never been addressed with a unified computational approach, which depends on the pure geometric form of the parts and not on application-specific features. We propose a method for the automatic reconstruction of a model based on the geometry of its parts, which may be computer-generated models or range-scanned models. The matching process can benefit from any other external constraint imposed by the specific application 相似文献
894.
Mössbauer studies of Fe2+ in water-soaked nafion polymer membranes in the temperature range between 90 K and 250 K have been performed. Above a critical temperature (~ 180 K) the spectra exhibit both elastic narrow absorption lines and quasielastic broad lines. These spectra are typical of bounded diffusion phenomena observed by Mössbauer spectroscopy in macromolecular systems like haemoglobin, myoglobin and ferritin. Similar spectral shapes have been observed by quasielastic neutron scattering from water in nafion membranes. Within 50 K above the critical temperature the total Mössbauer absorption area decreases by an order of magnitude whereas the narrow absorption line decreases by two orders of magnitude. The results are interpreted in terms of bounded diffusive motion of the iron. Using a model based on overdamped harmonically bound Brownian motion, the essential parameters of the iron motion can be derived as a function of temperature. The iron motion most probably reflects the motion of a large Fe2+ complex, e.g. Fe(H2O)2+6, which is attached to the polymer side chains via the sulphonic group. 相似文献
895.
896.
897.
Phillips Dorothy A.; Hearty Paul J.; Latrémouille Susane; Treurniet William C.; Whalen Thomas E. 《Canadian Metallurgical Quarterly》1985,26(3):219
Discusses telematics, a new field of behavioral research in Canada that has grown with the technical developments in which computers and telecommunications have been combined. Three domains of behavioral research reflect relationships between humans and the technology and use the evidence and methods of different areas of psychology: (1) interface studies address perception and performance questions, (2) dialog studies focus on cognitive processes, and (3) impact studies investigate social relations and how institutions and individuals are affected by telematics. Studies conducted during the past 5 yrs by the Behavioural Research and Evaluation division of the Department of Communications, Government of Canada, are described in each of these 3 domains. Behavioral research in telematics is expected to be an increasingly important activity in which psychologists may play an active part as the technology disseminates. (French abstract) (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
898.
Melting and crystallization behaviour of elastoplastic semicrystalline copolymers: poly(ether ester)
The melting and crystallization behaviour of an elastoplastic semi-crystalline poly(etherester) has been studied by differential scanning calorimetry. The shape of the melting endotherm is strongly dependent on heating rate and annealing time and results from the sum of simultaneous melting and crystallization phenomena. Samples prepared by different techniques, i.e. by solvent evaporation or by melt extrusion, behave very differently owing to specific crystal morphologies. By applying the Hoffman-Weeks plot, the equilibrium melting temperature has been extrapolated. The Avrami treatment allows the calculation of the index n and of the rate constant K from the isothermal kinetic data. 相似文献
899.
900.
Yu. V. Drobyshevskii V. K. Ezhov E. A. Lobikov V. N. Prusakov V. F. Serik V. B. Sokolov 《Atomic Energy》2002,93(1):578-588
The exploding-wire method, the photochemical method of irradiation with a light flux from a high-pressure mercury lamp, a high-intensity spark discharge, and irradiation by a CO2 laser are used to reduce plutonium hexafluoride and to separate it from uranium hexafluoride. The dependence of the reduction of plutonium hexafluoride on the wire material, the mass of the reduced product, and the amount of input energy is investigated.It is shown that the methods presented for reducing plutonium hexafluoride and separating it from uranium hexafluoride can be used under static and dynamic conditions for preparative purposes and on a large scale. 相似文献