全文获取类型
收费全文 | 3886篇 |
免费 | 67篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 40篇 |
综合类 | 3篇 |
化学工业 | 547篇 |
金属工艺 | 43篇 |
机械仪表 | 66篇 |
建筑科学 | 205篇 |
矿业工程 | 15篇 |
能源动力 | 76篇 |
轻工业 | 270篇 |
水利工程 | 13篇 |
石油天然气 | 21篇 |
无线电 | 294篇 |
一般工业技术 | 519篇 |
冶金工业 | 1372篇 |
原子能技术 | 30篇 |
自动化技术 | 443篇 |
出版年
2021年 | 26篇 |
2019年 | 25篇 |
2018年 | 26篇 |
2017年 | 29篇 |
2016年 | 47篇 |
2015年 | 34篇 |
2014年 | 46篇 |
2013年 | 173篇 |
2012年 | 100篇 |
2011年 | 134篇 |
2010年 | 114篇 |
2009年 | 102篇 |
2008年 | 141篇 |
2007年 | 133篇 |
2006年 | 131篇 |
2005年 | 94篇 |
2004年 | 91篇 |
2003年 | 92篇 |
2002年 | 89篇 |
2001年 | 71篇 |
2000年 | 61篇 |
1999年 | 77篇 |
1998年 | 205篇 |
1997年 | 138篇 |
1996年 | 117篇 |
1995年 | 112篇 |
1994年 | 98篇 |
1993年 | 94篇 |
1992年 | 70篇 |
1991年 | 47篇 |
1990年 | 57篇 |
1989年 | 57篇 |
1988年 | 69篇 |
1987年 | 59篇 |
1986年 | 61篇 |
1985年 | 64篇 |
1984年 | 56篇 |
1983年 | 57篇 |
1982年 | 59篇 |
1981年 | 50篇 |
1980年 | 55篇 |
1979年 | 48篇 |
1978年 | 36篇 |
1977年 | 44篇 |
1976年 | 67篇 |
1975年 | 43篇 |
1974年 | 50篇 |
1973年 | 35篇 |
1972年 | 29篇 |
1971年 | 22篇 |
排序方式: 共有3957条查询结果,搜索用时 31 毫秒
91.
Bandi S.P.R. Washburn C. Mukund P.R. Kolnik J. Paradis K. Howard S. Burleson J. 《Microwave and Wireless Components Letters, IEEE》2006,16(5):290-292
One of the most challenging problems encountered in developing RF circuits is accurate prediction of MOS behavior at microwave signal and data frequencies. An attempt is made in this work to accurately model the device input impedance for the 1-20-GHz frequency range. The effect of device length and single-leg width on the input impedance is studied with the aid of extensive measured data obtained from devices built in 0.11-/spl mu/m and 0.18-/spl mu/m technologies. The measured data illustrates that the device input impedance has a nonlinear frequency dependency. It is also shown that this variation in input impedance is a result of gate poly-silicon depletion, which can be modeled by an external RC network connected at the gate of the device. Excellent agreement between the simulation results and the measured data validates the model in the device active region. 相似文献
92.
Controversies are rampant in contemporary psychology concerning the appropriate method for observing consciousness and the role inner experience should play in psychological theorizing. These conflicting orientations reflect, in part, methodological differences between natural science and human science interpretations of psychology. Humanistic psychology and philosophical phenomenology both employ a human science approach to psychology that seeks to explain behavior in terms of a person's subjective existence. Maslow's and Heidegger's formulations are both fulfillment theories in that they specify moral values that suggest how life ought to be lived. Natural science methodology rejects the possibility that moral imperatives can be validated, whereas human science methodology allows phenomenological convictions to justify recommendations about a fulfilled life and a good society. The social role of psychology is analyzed within the framework of phenomenological convictions and scientific truth. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
93.
Martins Silvia S.; Mazzotti Guido; Chilcoat Howard D. 《Canadian Metallurgical Quarterly》2005,13(3):244
This study aims to estimate changes in the prevalence of ecstasy use over time, analyze the overlap of ecstasy use and other drug use, and compare other drug use in ecstasy versus marijuana users. The authors hypothesized that ecstasy users early in the "epidemic" would be polydrug users and that associations between ecstasy and other drug use would diminish as the prevalence of ecstasy use increased. Data were drawn from public use data files from the 1995, 1997, 1999, and 2001 National Household Survey on Drug Abuse. Ecstasy use increased in the U.S. population and the prevalence was greater in younger age groups. Ecstasy users were likely to use a variety of other drugs; however, association of ecstasy use with other drug use was strongest early in the "epidemic," diminishing as the number of new users increased. Later, more drug-naive adolescents and young adults began experimenting with ecstasy. These results can orient prevention strategies that target ecstasy users. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
S. Rudtsch H. P. Ebert F. Hemberger G. Barth R. Brandt U. Groß W. Hohenauer K. Jaenicke-Roessler E. Kaschnitz E. Pfaff W. Pößnecker G. Pottlacher M. Rhode B. Wilthan 《International Journal of Thermophysics》2005,26(3):855-867
The results of an inter laboratory comparison of thermal conductivity, thermal diffusivity, specific heat capacity, and thermal
expansion measurements on austenitic stainless steel in the temperature range between 20 and 1000°C are presented here. Mean
values are presented for the physical properties studied. Reliable relative expanded uncertainties can be stated for the properties
determined, which were achieved by applying good measurement practice, i.e., 3% for thermal expansion, 5% for specific heat
capacity and thermal diffusivity, and 6% for thermal conductivity. The mean values derived from this intercomparison agree
well with the results of a previous intercomparison in 1990.
An erratum to this article is availabale at . 相似文献
95.
BillHoward 《个人电脑》2003,9(6):149-149
有谁相信Intel和MIcrosoft所说的一切吗7我也不相信。所以我对过去两周PC Magazine实验室的结果感到吃惊:配备新型1.6GHz Intel Pentium M CPU的centnno系统堪与配备3.06GHz台式机芯片的笔记本媲美,Centrino系统的电池寿命几乎是近期的高端笔记本的两倍。Centrino笔记本几乎具备我们所希望的以及Intel所声称的一切优点。 相似文献
96.
97.
This paper introduces the ideas behind BPML, the business process modelling language published by BPMI. BPML provides a process-centric (as opposed to a datacentric) metalanguage and execution model for business systems. It is underpinned by a strong mathematical foundation, the pi-calculus. The current paper is derived from supplementary appendices to a book which describes a ‘third wave’ approach to business process management [Business Process Management: The Third Wave, 2003]. The aim is to model business processes directly in an executable form, so that the mobility and mutability inherent in business behaviour is reflected and supported in the corresponding IT systems, erasing the present IT-business divide. 相似文献
98.
Howard Bowman Helen Cameron Peter King Simon Thompson 《Formal Methods in System Design》2003,22(1):5-38
This paper explores a formalism for describing a wide class of multimedia document constraints, based on an interval temporal logic. We describe the requirements that arise from the multimedia documents application area, and we illustrate these requirements using several examples. Then we present the temporal logic formalism that we use. This logic extends existing interval temporal logic with a number of new features: actions, framing of actions, past operators, a projection-like operator called filter and a new handling of interval length. The notation is applied to the specification of the examples, and in particular a set of logical manipulations, providing feedback to an author, is presented. A model theory, logic and satisfaction relation are defined for the notation. 相似文献
99.
John John E. So Thomas J. Downar Raghunandan Janardhan Howard Jay Siegel 《International journal of parallel programming》1998,26(2):183-207
The performance of conjugate gradient (CG) algorithms for the solution of the system of linear equations that results from the finite-differencing of the neutron diffusion equation was analyzed on SIMD, MIMD, and mixed-mode parallel machines. A block preconditioner based on the incomplete Cholesky factorization was used to accelerate the conjugate gradient search. The issues involved in mapping both the unpreconditioned and preconditioned conjugate gradient algorithms onto the mixed-mode PASM prototype, the SIMD MasPar MP-1, and the MIMD Intel Paragon XP/S are discussed. On PASM , the mixed-mode implementation outperformed either SIMD or MIMD alone. Theoretical performance predictions were analyzed and compared with the experimental results on the MasPar MP-1 and the Paragon XP/S. Other issues addressed include the impact on execution time of the number of processors used, the effect of the interprocessor communication network on performance, and the relationship of the number of processors to the quality of the preconditioning. Applications studies such as this are necessary in the development of software tools for mapping algorithms onto either a single parallel machine or a heterogeneous suite of parallel machines. 相似文献
100.
S. Das E. J. Palmiere I. C. Howard 《Metallurgical and Materials Transactions A》2004,35(13):1087-1095
This article presents a novel experimental technique to infer the coupled effects of friction and heat transfer during the
hot rolling of steels. The technique, termed the “cut-groove” method, relates the behavior of the deforming grooves cut on
the strip surface to the local effects of friction and heat transfer. Validation of the experimentally observed groove shapes
involved developing two-dimensional (2-D) and three-dimensional (3-D) finite-element (FE) models that employed a probabilistic
distribution diagram (PDD). The PDD framework modeled the roll-strip interface and accounted for the variations in the oxide
scale as distinct states that affect both friction and heat transfer. The numerically predicted groove openings are in good
agreement with the experimentally observed groove shapes, particularly for the 2-D case. For the 3-D model, deviations are
observed at regions close to the strip edges that are affected by nonplanar strain arising from spread during laboratory rolling.
S. DAS, formerly Student, Department of Engineering Materials, and later Research Associate, Institute of Microstructural
and Mechanical Process Engineering, The University of Sheffield (IMMPETUS), Sheffield, SI 3JD, United Kingdom 相似文献