全文获取类型
收费全文 | 26118篇 |
免费 | 1131篇 |
国内免费 | 36篇 |
专业分类
电工技术 | 342篇 |
综合类 | 39篇 |
化学工业 | 5900篇 |
金属工艺 | 406篇 |
机械仪表 | 491篇 |
建筑科学 | 1425篇 |
矿业工程 | 107篇 |
能源动力 | 647篇 |
轻工业 | 2037篇 |
水利工程 | 248篇 |
石油天然气 | 72篇 |
无线电 | 1878篇 |
一般工业技术 | 4757篇 |
冶金工业 | 4931篇 |
原子能技术 | 196篇 |
自动化技术 | 3809篇 |
出版年
2023年 | 232篇 |
2022年 | 371篇 |
2021年 | 589篇 |
2020年 | 362篇 |
2019年 | 467篇 |
2018年 | 580篇 |
2017年 | 516篇 |
2016年 | 683篇 |
2015年 | 611篇 |
2014年 | 806篇 |
2013年 | 1532篇 |
2012年 | 1247篇 |
2011年 | 1616篇 |
2010年 | 1135篇 |
2009年 | 1063篇 |
2008年 | 1214篇 |
2007年 | 1145篇 |
2006年 | 1006篇 |
2005年 | 800篇 |
2004年 | 776篇 |
2003年 | 690篇 |
2002年 | 590篇 |
2001年 | 452篇 |
2000年 | 375篇 |
1999年 | 426篇 |
1998年 | 865篇 |
1997年 | 617篇 |
1996年 | 488篇 |
1995年 | 437篇 |
1994年 | 396篇 |
1993年 | 384篇 |
1992年 | 278篇 |
1991年 | 207篇 |
1990年 | 272篇 |
1989年 | 269篇 |
1988年 | 220篇 |
1987年 | 229篇 |
1986年 | 231篇 |
1985年 | 274篇 |
1984年 | 236篇 |
1983年 | 228篇 |
1982年 | 210篇 |
1981年 | 204篇 |
1980年 | 175篇 |
1979年 | 199篇 |
1978年 | 167篇 |
1977年 | 198篇 |
1976年 | 247篇 |
1975年 | 165篇 |
1974年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
van Dick Rolf; Wagner Ulrich; Pettigrew Thomas F.; Christ Oliver; Wolf Carina; Petzel Thomas; Castro Vanessa Smith; Jackson James S. 《Canadian Metallurgical Quarterly》2004,87(2):211
Furthering G. W. Allport's (1954) contentions for optimal contact, the authors introduce a new construct: the perceived importance of contact. They propose that perceived importance is the best proximal predictor of contact's reduction of prejudice. If individuals have opportunities for contact at work or in the neighborhood, their chances to have intergroup acquaintances and friends increase. Intergroup contact among acquaintances and friends can be perceived as more or less important, which in turn determines intergroup evaluations. A 1st study shows that the new measure of perceived importance is indeed distinct from established quantity and quality indicators. The results are cross-validated in a 2nd study that also sheds light on the meaning of importance. In 3rd and 4th studies, structural equation analyses and a meta-analysis support the hypotheses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
Valentian A. Thomas O. Vladimirescu A. Amara A. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2004,12(6):662-669
A simple, yet realistic physics-based model is introduced to describe the subthreshold drain current of a MOSFET taking into account the body- and drain-voltage dependencies, including the short channel effects. This model, verified by SPICE simulations, describes adequately the pseudotriode and pseudosaturation regions of MOS transistors operated below V/sub T/. It can be applied for predicting bulk- or partially depleted (PD) SOI CMOS circuit operation. Analytical expressions derived for the logic switching threshold and delay are applied to predict the performance of CMOS-SOI inverters. 相似文献
43.
A revised methodology is described for research on metacognitive monitoring, especially judgments of learning (JOLs), to investigate psychological processing that previously has been only hypothetical and unobservable. During data collection a new stage of recall occurs just prior to the JOL, so that during data analysis the items can be partitioned into subcategories to measure the degree of JOL accuracy in ways that are more analytic than was previously possible. A weighted-average combinatorial rule allows the component measures of JOL accuracy to be combined into the usual overall measure of metacognitive accuracy. An example using the revised methodology offers a new explanation for the delayed-JOL effect, in which delayed JOLs are more accurate than immediate JOLs for predicting recall. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two
copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example
of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive
slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal
deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures
after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and
erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors
(ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements,
the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node. 相似文献
45.
Weian Huang Fuhrmann D.R. Politte D.G. Thomas L.J. Jr. States D.J. 《IEEE transactions on bio-medical engineering》1998,45(4):422-428
In four-color fluorescence-based automated DNA sequencing, a 4×4 filter matrix parameterizes the relationship between the dye-intensity signals of interest and the data collected by an optical imaging system. The filter matrix is important because the estimated DNA sequence is based on the dye intensities that can only be recovered via inversion of the matrix. Here, the authors present a calibration method for the estimation of the columns of this matrix, using data generated through a special experiment in which DNA samples are labeled with only one fluorescent dye at a time. Simulations and applications of the method to real data are provided, with promising results 相似文献
46.
College readers read and answered questions on 12 short essays. Essays formatted so that points between phrases had fractional extra space added to them were comprehended better than normally formatted text. These improvements were specific to average readers. Practically, the results justify classroom research on the benefits of phrase-sensitive formatting; theoretically, the results add to existing evidence that poor to average readers specifically lack perceptual strategies for grouping word sequences into phrases. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
Björn Täljsten 《International Journal of Fracture》1996,82(3):253-266
This paper presents the use of fracture mechanics for the plate bonding technique. Plates of steel or carbon-fibre reinforced
plastic are bonded with an epoxy adhesive to rectangular concrete prisms and loaded in shear up to failure, what is normally
known in fracture mechanics as mode II failure. In this special application a linear and a nonlinear approach are presented.
The nonlinear equation derived for a realistic shear-deformation curve can only be used for numerical calculations. However,
for simplified shear-deformation curves, the derived formula can be solved analytically. Results from tests, which are compared
with the theory, are also presented. 相似文献
48.
John C. Hart Gordon W. Lescinsky Daniel J. Sandin Thomas A. DeFanti Louis H. Kauffman 《The Visual computer》1993,9(7):346-355
The pipelined architecture and parallel organization of the AT&T Pixel Machine image computer are described and demonstrated with applications for the visualization of multidimensional fractals, particularly linear fractals and quaternion/ stacked Julia sets. Techniques for pushing the Pixel Machine to its peak abilities are described and apply to more recent parallel image computers as well. 相似文献
49.
R Thomas 《Canadian Metallurgical Quarterly》1993,15(4):285-289
The purpose for this study was to evaluate the results of silicone oil use in patients who have undergone vitrectomy for proliferative vitreoretinopathy (PVR). The authors reviewed the 5-year results of 50 consecutive patients (52 eyes) with grade C1/D3 PVR operated on in 1987. Silicone oil has been removed in 42 eyes. The retina remained attached in 38 eyes. Visual acuities were finger counting in 12 eyes and 0.1 or greater in 19 eyes. Glaucoma was thought to be the major cause of loss of visual acuity after an initial improvement (9 eyes), as well as the most frequent complication of surgery (13 eyes). Silicone oil was deemed nonremovable in 10 operated eyes. A questionnaire was developed to determine the patients' perceptions of the use of silicone oil, and 46 patients responded to the questionnaire. Four patients indicated that they would not have elected to have surgery again. Six patients thought that surgery was not worthwhile, but would permit treatment again. Most patients thought that a modest amount of improvement had taken place and that vision was stable. Subjectively, most patients believed that surgery was worthwhile. 相似文献
50.