全文获取类型
收费全文 | 128041篇 |
免费 | 19820篇 |
国内免费 | 13951篇 |
专业分类
电工技术 | 14601篇 |
技术理论 | 8篇 |
综合类 | 15825篇 |
化学工业 | 4964篇 |
金属工艺 | 3438篇 |
机械仪表 | 10813篇 |
建筑科学 | 15825篇 |
矿业工程 | 3008篇 |
能源动力 | 3128篇 |
轻工业 | 1671篇 |
水利工程 | 3509篇 |
石油天然气 | 2233篇 |
武器工业 | 2275篇 |
无线电 | 16293篇 |
一般工业技术 | 9974篇 |
冶金工业 | 1954篇 |
原子能技术 | 511篇 |
自动化技术 | 51782篇 |
出版年
2024年 | 909篇 |
2023年 | 2210篇 |
2022年 | 3998篇 |
2021年 | 4400篇 |
2020年 | 4876篇 |
2019年 | 4029篇 |
2018年 | 3983篇 |
2017年 | 4871篇 |
2016年 | 5576篇 |
2015年 | 6311篇 |
2014年 | 9088篇 |
2013年 | 9023篇 |
2012年 | 10390篇 |
2011年 | 10723篇 |
2010年 | 8700篇 |
2009年 | 8891篇 |
2008年 | 8978篇 |
2007年 | 10177篇 |
2006年 | 8369篇 |
2005年 | 6912篇 |
2004年 | 5498篇 |
2003年 | 4496篇 |
2002年 | 3561篇 |
2001年 | 3002篇 |
2000年 | 2598篇 |
1999年 | 2006篇 |
1998年 | 1602篇 |
1997年 | 1335篇 |
1996年 | 1042篇 |
1995年 | 843篇 |
1994年 | 735篇 |
1993年 | 542篇 |
1992年 | 456篇 |
1991年 | 321篇 |
1990年 | 304篇 |
1989年 | 244篇 |
1988年 | 170篇 |
1987年 | 89篇 |
1986年 | 62篇 |
1985年 | 91篇 |
1984年 | 79篇 |
1983年 | 69篇 |
1982年 | 59篇 |
1981年 | 26篇 |
1980年 | 45篇 |
1979年 | 35篇 |
1978年 | 15篇 |
1977年 | 12篇 |
1975年 | 11篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
本文除概略介绍气体检测器的种类处,主要对气体检测器的原理和在实际使用中的局限性作一基本归纳叙述。限于篇幅,本文将论述的重点放在气体检测器的选用与设置规划上,提出个人的一点心得与看法,以作为未来设置气体检测器系统时之参考。 相似文献
62.
本文提出一种关于DMT系统传输纯数据流业务的最佳的功率分配算法,该算法使用了一种有效的表格查手工艺工和拉格朗日乘法器对分搜索办法,能够较快的收敛到最佳的功率点。同时,易于用硬件和软件实现。 相似文献
63.
黄河流域委属大河控制站站网布局分析检验与调整 总被引:4,自引:0,他引:4
简要论述了黄河流域委属大河控制站的基本情况,通过资料分析,按“直线原则”计算了黄河大河控制站布站数目的上、下限,并调查分析落实了各河段近期和中长期治理开发对水资料的需求,确定各河段测站数目的采用值;对照现有站数,结合测站位置,功能,测验,生活条件等,逐段逐站进行审查,综合评估,决定测站的撤,迁,留,并对密度不足的河段提出了设站意见。 相似文献
64.
This paper presents a method to compensate voltage sags with minimum energy injection for a series‐connected voltage restorer using a micro‐SMES. A circuit for extracting the fundamental symmetrical components from sag voltages and a minimum energy injection algorithm is described. Simulations of voltage sag compensation have been carried out using PSCAD/EMTDC for various faults. The simulation results confirm the validity of the proposed method and show the possibility of reducing the size of energy storage devices. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(3): 70–80, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10047 相似文献
65.
NBR/PP热塑性弹性体研究进展 总被引:12,自引:0,他引:12
阐述了NBR/PP共混热塑性弹性体动态硫化胶的国内外研究进展、微观相态结构、性能、应用及展望。 相似文献
66.
67.
Hong Jeong Jeong‐Ho Park 《International Journal of Adaptive Control and Signal Processing》2002,16(1):1-23
Tracking targets of interest is one of the major research areas in radar surveillance systems. We formulate the problem as incomplete data estimation and apply EM to the MAP estimate. The resulting filter has a recursive structure analogous to the Kalman filter. The advantage is that the measurement‐update deals with multiple measurements in parallel and the parameter‐update estimates the system parameters on the fly. Experiments tracking separate targets in parallel show that tracking maintenance ratio of the proposed system is better than that of NNF and RMS position error is smaller than that of PDAF. Also, the system parameters are correctly obtained even from incorrect initial values. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
68.
In this paper we describe, from a theoretical point of view, critical configurations for the projective reconstruction of
a set of points, for a single view, i.e. for calibration of a camera, in the case of projections from ℙk to ℙ2 for k ≥ 4. We give first a general result describing these critical loci in ℙk, which, if irreducible, are algebraic varieties of dimension k−2 and degree 3. If k=4 they can be either a smooth ruled surface or a cone and if k = 5 they can be a smooth three dimensional variety, ruled in planes, or a cone. If k≥ 6, the variety is always a cone, the
vertex of which has dimension at least k − 6. The reducible cases are studied in Appendix A.
These results are then applied to determine explicitly the critical loci for the projections from ℙk which arise from the dynamic scenes in ℙ3 considered in [13].
Marina Bertolini is currently Associate Professor of Geometry at the Department of Mathematics at the Università degli Studi di Milano, Italy.
Her main field of research is Complex Projective Algebraic Geometry, with particular interest for the classification of projective
varieties and for the geometry of Grassmann varieties. On these topics M. Bertolini has published more than twenty reviewed
papers on national and international journals. She has been for some years now interested also in applications of Algebraic
Geometry to Computer Vision problems.
Cristina Turrini is Associate Professor of Geometry at the Department of Mathematics of Università degli Studi di Milano, Italy. Her main
research interest is Complex Projective Algebraic Geometry: subvarieties of Grassmannians, special varieties, automorphisms,
classification. In the last two years she has started to work on applications of Algebraic Geometry to problems of Computer
Vision. She is author or co-author of about thirty reviewed papers. She is also involved in popularization of Mathematics,
and on this subject she is co-editor of some books. 相似文献
69.
可持续发展战略指导下的轨道交通规划与评价 总被引:9,自引:0,他引:9
提出了轨道交通规划与评价在实施可持续发展战略过程中需要研究的问题,研究重点是轨道交通规划与评价方法体系和环境对策,研究了轨道交通规划目标的变化、轨道交通规划优化决策理论与方法、轨道交通规划中的环境影响评价、城市轨道交通网络的合理规划、城际轨道交通——客运专线/高速铁路线路基本走向的规划、轨道交通规划可持续发展的评价指标体系概念框架、轨道交通系统可持续发展的能力建设问题等,并通过实例验证了所建立的理论方法体系和模型体系;不仅进行了有关理论和方法的探讨,而且以面向实际应用为目标,开发了相应的软件系统,为轨道交 相似文献
70.
The aim of this study was to investigate the drug‐loading effects on release and mechanical properties of a scleroglucan gel, with the intention of considering them in delivery systems formulations. The rheological and kinetic properties of a 2 % w/w scleroglucan gel matrix loaded with 0, 0.02, 0.04, 0.06, 0.2 and 0.4 % w/w of theophylline (Th, used as a model drug) were investigated. Rheological measurements were performed in a controlled‐stress rotational‐shear rheometer under isothermal conditions. For theophylline release from the gel a flat Franz cell was used and the kinetic parameters were derived applying a semi‐empirical power law. The influence of scleroglucan molar weight on kinetic and rheological behaviour was also studied. Results suggest two possible effects of drug loading on the gel network: in the 0.04–0.06 % w/w Th range a plasticizing effect and in the 0.2–0.4 % w/w Th range a rigidization effect. In the first range mentioned, the changes in the gel structural properties tested by means of rheological measurements are coincident with changes in drug‐release kinetics. Copyright © 2005 Society of Chemical Industry 相似文献