全文获取类型
收费全文 | 43688篇 |
免费 | 966篇 |
国内免费 | 190篇 |
专业分类
电工技术 | 583篇 |
综合类 | 640篇 |
化学工业 | 4716篇 |
金属工艺 | 611篇 |
机械仪表 | 894篇 |
建筑科学 | 885篇 |
矿业工程 | 393篇 |
能源动力 | 471篇 |
轻工业 | 2184篇 |
水利工程 | 628篇 |
石油天然气 | 61篇 |
武器工业 | 8篇 |
无线电 | 1933篇 |
一般工业技术 | 3479篇 |
冶金工业 | 21479篇 |
原子能技术 | 188篇 |
自动化技术 | 5691篇 |
出版年
2024年 | 56篇 |
2023年 | 197篇 |
2022年 | 128篇 |
2021年 | 142篇 |
2019年 | 70篇 |
2018年 | 477篇 |
2017年 | 701篇 |
2016年 | 1080篇 |
2015年 | 806篇 |
2014年 | 452篇 |
2013年 | 478篇 |
2012年 | 2228篇 |
2011年 | 2514篇 |
2010年 | 703篇 |
2009年 | 783篇 |
2008年 | 628篇 |
2007年 | 652篇 |
2006年 | 584篇 |
2005年 | 3397篇 |
2004年 | 2615篇 |
2003年 | 2092篇 |
2002年 | 874篇 |
2001年 | 745篇 |
2000年 | 289篇 |
1999年 | 623篇 |
1998年 | 6166篇 |
1997年 | 3810篇 |
1996年 | 2504篇 |
1995年 | 1456篇 |
1994年 | 1070篇 |
1993年 | 1102篇 |
1992年 | 247篇 |
1991年 | 305篇 |
1990年 | 306篇 |
1989年 | 276篇 |
1988年 | 297篇 |
1987年 | 221篇 |
1986年 | 199篇 |
1985年 | 172篇 |
1984年 | 75篇 |
1983年 | 86篇 |
1982年 | 133篇 |
1981年 | 178篇 |
1980年 | 193篇 |
1979年 | 63篇 |
1978年 | 100篇 |
1977年 | 614篇 |
1976年 | 1323篇 |
1975年 | 100篇 |
1971年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 29 毫秒
11.
On the effect of spatial variances in historical rainfall time series to CSO performance evaluation.
Historical, high-resolution rain series are the backbone of modern combined sewer overflow (CSO) structure design. These rain series are the input to the computational estimation of the performance of the measures with respect to CSO pollution abatement. However, those historical precipitation measurements are available at only a few locations. Frequently rain series have to be used from gauging stations at a significant distance. In order to judge and to compensate for this influence an estimate between rain characteristics and combined sewer outflow (CSO) performance indicators would be useful. In this paper such correlations have been sought for a collection of 37 rain series covering large areas of Europe. It was found that the mean annual rain volume can explain most of the variances for the performance indicators Number of overflows and CSO volume. For explaining the spatial differences in the efficiency of the CSO structure another rain characteristic, i.e. the maximum event with a return period of one year, is to be used. 相似文献
12.
A new polymer electrolyte poly(acrylonitrile)-dimethylsulphoxide-salt for electrochemical capacitors
The PAN-DMSO-Et4NBF4 and PAN-DMSO-Et4NTf (Tf is triflate ion) electrolytes were prepared as white, turbid foils with a thickness in the range of 0.1-0.5 mm, using the casting technique. Room temperature conductance of the electrolytes, detected from ac impedance experiments, was at the level of 8 and 14 mS cm−1 for Et4NBF4 and Et4NTf salts, respectively. The electrochemical stability window of approximately 2.6-2.8 V was estimated using a glassy carbon electrode. Temperature dependence of the conductivity is of the Arrhenius-type for both electrolytes, with an activation energy of approximately 34 kJ mol−1. The double-layer capacitors built with these electrolytes, serving both as separators and activated carbon powder (ACP) binders, showed a specific capacity of 50 F g−1 of carbon material. Capacitors were assembled by sandwiching the PAN-DMSO-salt electrolyte between two PAN-salt-DMSO-ACP-AB electrodes and pressing across the system; the resulting devices had a coin-like shape with 8 mm diameter and thickness between 2.0 and 2.5 mm. 相似文献
13.
Vehicle detection by means of stereo vision-based obstacles features extraction and monocular pattern analysis. 总被引:2,自引:0,他引:2
Gwena?lle Toulminet Massimo Bertozzi Stéphane Mousset Abdelaziz Bensrhair Alberto Broggi 《IEEE transactions on image processing》2006,15(8):2364-2375
This paper presents a stereo vision system for the detection and distance computation of a preceding vehicle. It is divided in two major steps. Initially, a stereo vision-based algorithm is used to extract relevant three-dimensional (3-D) features in the scene, these features are investigated further in order to select the ones that belong to vertical objects only and not to the road or background. These 3-D vertical features are then used as a starting point for preceding vehicle detection; by using a symmetry operator, a match against a simplified model of a rear vehicle's shape is performed using a monocular vision-based approach that allows the identification of a preceding vehicle. In addition, using the 3-D information previously extracted, an accurate distance computation is performed. 相似文献
14.
Sébastien Ambellouis Fran?ois Cabestaing Jack-Gérard Postaire 《IEEE transactions on image processing》2006,15(6):1601-1609
Energy-based methods for motion estimation in image sequences process the input data either in the spatiotemporal or in the frequency domain. In both cases, the algorithms already described in the literature often require a huge number of elementary operations. In this paper, we describe a class of velocity selective filters which yield an accurate detection of the edges moving in the sequence. We first present a filtering scheme based on a convolution operation computed on a finite size neighborhood and describe its properties in the spatiotemporal and frequency domains. Then, we show that filters with similar properties can be implemented recursively, i.e., as convolutions computed on infinite-size neighborhoods. As an example, we finally show the filters' responses in the case of two superimposed translational motions. 相似文献
15.
Presents an obituary and information about the life and accomplishments of Josef Maria Bro?ek. Born August 14, 1913, in the ancient town of Melnik, in central Bohemia, today the Czech Republic, Josef spent his childhood in Poland (Warsaw, 1913- 1915) and in Siberia (1915-1920). His education in Czechoslovakia culminated with a thesis on "Memory, Its Measurement and Structure" and a PhD awarded in June 1937. In the history of psychology, his lifetime project bore the title "Historiography of Psychology Around the World," and it covered about 20 geographical areas. Extensive attention was devoted to institutional and organizational developments as journals, academic settings, archives, museums, research groups, conferences, and institutes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
17.
Frank te Beest Ad Peeters Kees van Berkel Hans Kerkhoff 《Journal of Electronic Testing》2003,19(4):397-406
Handshake circuits form a special class of asynchronous circuits that has enabled the industrial exploitation of the asynchronous potential such as low power, low electromagnetic emission, and increased cryptographic security. In this paper we present a test solution for handshake circuits that brings synchronous test-quality to asynchronous circuits. We add a synchronous mode of operation to handshake circuits that allows full controllability and observability during test. This technique is demonstrated on some industrial examples and gives over 99% stuck-at fault coverage, using test-pattern generators developed for synchronous circuits. The paper describes how such a full-scan mode can be achieved, including an approach to minimize the number of dummy latches in case latches are used in the data path of the handshake circuit. 相似文献
18.
19.
20.
H. W. Brinks V. A. Yartys B. C. Hauback H. Fjellvg B. Ouladdiaf 《Journal of Alloys and Compounds》2002,340(1-2):62-66
TbNiSiD1.78 has been studied by powder neutron diffraction below 100 K. The compound takes the hexagonal room temperature structure at 100 and 50 K (P63/mmc). At 2 K, below the antiferromagnetic ordering temperature of 10 K, there is a small orthorhombic distortion of the lattice. The refined unit-cell dimensions at 2 K (space group Pnma) are a=7.9505(2), b=4.02502(14), c=6.9823(2) Å. The magnetic moments of Tb are 8.71(6) μB, and are ordered antiferromagnetically along a. 相似文献