全文获取类型
收费全文 | 63420篇 |
免费 | 3515篇 |
国内免费 | 73篇 |
专业分类
电工技术 | 443篇 |
综合类 | 61篇 |
化学工业 | 11481篇 |
金属工艺 | 1060篇 |
机械仪表 | 1284篇 |
建筑科学 | 1898篇 |
矿业工程 | 118篇 |
能源动力 | 1173篇 |
轻工业 | 9576篇 |
水利工程 | 604篇 |
石油天然气 | 267篇 |
武器工业 | 5篇 |
无线电 | 3063篇 |
一般工业技术 | 10511篇 |
冶金工业 | 16921篇 |
原子能技术 | 253篇 |
自动化技术 | 8290篇 |
出版年
2023年 | 547篇 |
2022年 | 547篇 |
2021年 | 1374篇 |
2020年 | 1216篇 |
2019年 | 1185篇 |
2018年 | 2379篇 |
2017年 | 2352篇 |
2016年 | 2421篇 |
2015年 | 1793篇 |
2014年 | 2215篇 |
2013年 | 4631篇 |
2012年 | 3691篇 |
2011年 | 3325篇 |
2010年 | 2712篇 |
2009年 | 2379篇 |
2008年 | 2669篇 |
2007年 | 2370篇 |
2006年 | 1698篇 |
2005年 | 1417篇 |
2004年 | 1328篇 |
2003年 | 1185篇 |
2002年 | 1060篇 |
2001年 | 723篇 |
2000年 | 689篇 |
1999年 | 943篇 |
1998年 | 5506篇 |
1997年 | 3370篇 |
1996年 | 2136篇 |
1995年 | 1227篇 |
1994年 | 1010篇 |
1993年 | 1034篇 |
1992年 | 306篇 |
1991年 | 315篇 |
1990年 | 312篇 |
1989年 | 301篇 |
1988年 | 298篇 |
1987年 | 282篇 |
1986年 | 270篇 |
1985年 | 305篇 |
1984年 | 249篇 |
1983年 | 170篇 |
1982年 | 206篇 |
1981年 | 245篇 |
1980年 | 227篇 |
1979年 | 160篇 |
1978年 | 151篇 |
1977年 | 356篇 |
1976年 | 727篇 |
1975年 | 124篇 |
1973年 | 122篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Abdeljaoued Emna Brulé Mathieu Tayibi Saida Manolakos Dimitris Oukarroum Abdallah Monlau Florian Barakat Abdellatif 《Clean Technologies and Environmental Policy》2020,22(10):1967-1997
Clean Technologies and Environmental Policy - Biochar has caught great attention over the last decade, yielding a large number of publications in a broad range of disciplines. This scientometric... 相似文献
42.
43.
Meza-Espinoza Libier de los Ángeles Vivar-Vera María de Lourdes García-Magaña María Sáyago-Ayerdi Sonia G. Chacón-López Alejandra Becerrea-Verdín Eduardo M. Montalvo-González Efigenia 《Food science and biotechnology》2018,27(2):509-517
Food Science and Biotechnology - The enzymatic activity and partial characterization of proteases from Bromelia karatas fruits were evaluated and compared with Bromelia pinguin proteases. The... 相似文献
44.
J Comas I Rodríguez-Roda M Poch K V Gernaey C Rosen U Jeppsson 《Water science and technology》2006,53(4-5):303-311
Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance. 相似文献
45.
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
46.
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
47.
Quality of service has become today a major concern for operators of mobile communication networks. The massive development of networks and strong competition between operators has lead to the necessary and daily follow-up of network quality of service, a key factor for its subscriber’s fidelity. This article aims at presenting the optimization methodology and proposes its illustration with a case of RNO (Radio Network Optimisation) software usage, one of the Alcatel optimization toolchain component. After a short presentation of cellular network, the optimization basic principles are described. RNO software and its main functionnalities are then detailed before a last part dedicated to a real case of optimization done with RNO software. 相似文献
48.
D. Vignolles D. Smirnov G. Rikken B. Raquet H. Rakoto C. Proust M. Nardone J. Léotin F. Lecouturier M. Goiran O. Drachenko J. M. Broto L. Brossard A. Audouard 《Journal of Low Temperature Physics》2003,133(1-2):97-120
An overview over past and present activities and future developments at the Toulouse pulsed magnetic field facility is given, both as far as technical developments of the infrastructure, as well as low temperature physics performed at the LNCMP are concerned. 相似文献
49.
介绍北方交通大学与比利时鲁汶大学、布鲁塞尔自由大学、比利时铁路公司合作,在巴黎至布鲁塞尔之间高速铁路线上的Antoing大桥进行的二次高速铁路桥梁动力试验。试验桥梁由跨度50m的多跨预应力混凝土简支槽型梁构成,试验中列车速度达265-310km/h。通过现场试验和实验结果分析,得到了桥梁的频率、振型、阻尼等自振特性,以及桥梁在高速列车作用下的动挠度、梁和桥墩的横向和竖向加速度、橡胶支座的相对位移、梁体的动应变等动力响应特性。试验经验和测试结果对于充实高速铁路桥梁动力分析理论、改进数值分析模型、验证计算结果、提高高速铁路桥梁的动力设计水平、保证行车安全,具有重要的意义。 相似文献
50.
IC Wilson TJ Gardner JM DiNatale AM Gillinov WE Curtis DE Cameron 《Canadian Metallurgical Quarterly》1993,106(5):805-810
Leukocyte depletion improves early postischemic ventricular performance in neonatal models of global myocardial ischemia. However, the rate of leukocyte reaccumulation after cardiopulmonary bypass and its subsequent impact on myocardial function is not known. This laboratory study examined the effect of leukocyte depletion on myocardial performance during the initial 6-hour period after bypass in an in situ, in vivo porcine model of neonatal cardiac surgery. Fifteen 3- to 5-day-old piglets (eight control and seven leukocyte depleted animals) were instrumented by placement of left ventricular short-axis sonomicrometry crystals and an intraventricular micromanometer catheter. Mechanical leukocyte depletion was achieved with Pall RC100 filters (Pall Biomedical, Inc., Fajardo, Puerto Rico) in the cardiopulmonary bypass circuit. Neonatal hearts were subjected to 90 minutes of hypothermic ischemia after a single dose of cold crystalloid cardioplegia. Two control animals died after the operation and were excluded from data analysis. Leukocyte filtration reduced the granulocyte count during initial myocardial reperfusion to 0.8% of control values. However, circulating granulocyte counts increased in leukocyte depleted animals throughout the postoperative period, reaching 68% of control values by 6 hours. Despite this rapid return of circulating granulocytes, animals subjected to leukocyte depletion had significantly better preservation of left ventricular performance (measured by preload recruitable stroke work, p < or = 0.02), left ventricular systolic function (measured by end-systolic pressure-volume relationship, p < or = 0.05), and ventricular compliance (p < or = 0.04) during the experiment. These changes in ventricular function were associated with a significant increase in left ventricular water content (p < or = 0.02) and tissue myeloperoxidase activity (p < or = 0.005) in control animals compared with leukocyte depleted animals. This study demonstrates that leukocyte depletion during initial reperfusion results in sustained improvement in postischemic left ventricular function despite the rapid return of granulocytes to the circulation. 相似文献