全文获取类型
收费全文 | 8096篇 |
免费 | 393篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 74篇 |
综合类 | 5篇 |
化学工业 | 1458篇 |
金属工艺 | 175篇 |
机械仪表 | 187篇 |
建筑科学 | 339篇 |
矿业工程 | 20篇 |
能源动力 | 203篇 |
轻工业 | 631篇 |
水利工程 | 89篇 |
石油天然气 | 20篇 |
无线电 | 711篇 |
一般工业技术 | 1568篇 |
冶金工业 | 1848篇 |
原子能技术 | 23篇 |
自动化技术 | 1157篇 |
出版年
2023年 | 62篇 |
2022年 | 108篇 |
2021年 | 193篇 |
2020年 | 151篇 |
2019年 | 157篇 |
2018年 | 194篇 |
2017年 | 187篇 |
2016年 | 225篇 |
2015年 | 175篇 |
2014年 | 281篇 |
2013年 | 427篇 |
2012年 | 440篇 |
2011年 | 554篇 |
2010年 | 374篇 |
2009年 | 329篇 |
2008年 | 418篇 |
2007年 | 383篇 |
2006年 | 346篇 |
2005年 | 294篇 |
2004年 | 229篇 |
2003年 | 196篇 |
2002年 | 214篇 |
2001年 | 153篇 |
2000年 | 124篇 |
1999年 | 121篇 |
1998年 | 314篇 |
1997年 | 211篇 |
1996年 | 159篇 |
1995年 | 114篇 |
1994年 | 121篇 |
1993年 | 103篇 |
1992年 | 68篇 |
1991年 | 46篇 |
1990年 | 79篇 |
1989年 | 79篇 |
1988年 | 63篇 |
1987年 | 58篇 |
1986年 | 56篇 |
1985年 | 59篇 |
1984年 | 55篇 |
1983年 | 46篇 |
1982年 | 48篇 |
1981年 | 42篇 |
1980年 | 35篇 |
1979年 | 33篇 |
1978年 | 27篇 |
1977年 | 53篇 |
1976年 | 75篇 |
1974年 | 27篇 |
1971年 | 25篇 |
排序方式: 共有8508条查询结果,搜索用时 15 毫秒
1.
用于单芯片系统的改进型WXGA LCoS成像器 总被引:1,自引:1,他引:0
WillemA.Sloof MmthewS.Brennesholtz 《现代显示》2004,(3):36-39
本文讨论用于单芯片时序混色的菲利浦DD-720硅基液晶(LCoS)片。这种芯片主要用于HDTV背投影机和多媒体系统。与菲利浦以前的单片LCoS设计相比,由于该芯片具有电接口接点较少、封装简单和温度传感器内置等许多特点,使其应用于投影系统时成本降低。 相似文献
2.
Matthew R. James 《国际强度与非线性控制杂志
》1994,4(6):791-806
》1994,4(6):791-806
In this paper we present a numerical method for estimating the current state of a nonlinear control system. We use finite differences to discretize a modified version of the finite-time observer equations in James. The discretized equations are simple and easily programmed. The convergence and accuracy of the scheme is proved, and the scheme enjoys a number of important properties: availability of rate of convergence estimates, good robustness characteristics, and the ability to handle certain types of discontinuities in the observations. The major disadvantage is that the number of grid points required increases exponentially with the number of state dimensions. 相似文献
3.
The objective of this paper is to prove that the Clausius inequality must be re-stated to have general applicability for heat transfer involving radiative fluxes. The integrand (đQ/T) of the Clausius expression applies to heat conduction and convection, but does not hold for most radiative transfer scenarios, with the exception of reversible infinitesimal net blackbody radiation transfer. In other cases involving radiative transfer, the equality holds for a cycle even though irreversible heat addition by radiative transfer occurs. This is without the erroneous presumption of entropy destruction anywhere in the cycle. Thus, the Clausius inequality indicates reversibility for a cycle that includes an irreversible process. Further, in some radiative cases the quantity đQ/T, where T is the boundary temperature, is not the entropy transfer at the system boundary, and in fact, primarily represents entropy production within the system. It is also clear that in another case considered, the quantity đQ/T had no physical meaning whatsoever. Consequently, the Clausius expression has been re-stated so that it is applicable to cycles with processes involving any form of heat transfer. A new integrand (đQcc/T + đSNet,Rad) is presented, allowing the Clausius inequality to generally apply to all heat transfer scenarios. The work in this paper emphasizes the need to re-state other fundamental equations allowing applicability to all heat transfer processes, and draws attention to the unique character of radiative entropy calculations. 相似文献
4.
This paper looks at the concepts of entities, identities, identifiers and credentials, their definitions, and how they combine
to authenticate an identity to an account, or function, within a service. Credentials can be divided into several different
types on the basis of their use, origin and characteristics. In particular, types such as composite, dynamic and derived credentials
will be considered, and their applicability within an identity management system. Each credential must be managed through
its entire life cycle from initial registration, general use and suspension, to deletion. The notion of public (i.e. freely
distributable) and private (i.e. known only to you) aspects of a credential is explored. The bindings, by trusted third parties,
of identifiers and public credentials into permits and instruments of proof is explained along with the convenience, but greater
exposure, of local information. Several scenarios are analysed in terms of how different types of credentials are employed
during the authentication process. 相似文献
5.
A. J. Wright A. Wong L. L. Diosady 《Food research international (Ottawa, Ont.)》2003,36(9-10):1069-1072
A Ni catalyst was added to a cis-selective Pd catalyst in an attempt to further improve the Pd catalyst's cis-selectivity and activity for canola oil hydrogenation. The system was tested under reaction conditions known to be suitable for cis-selective hydrogenation with the Pd catalyst (50 ppm Pd, 70 °C, and 5.2 MPa). Although inactive on its own under these conditions, the addition of 100 ppm Ni increased the hydrogenation activity (from 2.12 to 2.49 10−2 min−1). Further addition of Ni up to 1000 ppm resulted in no further improvements in activity. The trans isomer contents of the oils hydrogenated with Pd and the Pd/Ni systems were similar. The level of conjugated dienes decreased rapidly during hydrogenation with both Pd alone and with the Pd/Ni combination and no changes in conjugation were detected in the presence of the Ni catalyst alone. The increased activity of the Pd/Ni system over Pd alone was attributed to adsorption of catalyst poisons from the oil by Ni. 相似文献
6.
Rosenberg Florian Curbera Francisco Duftler Matthew J. Khalaf Rania 《Internet Computing, IEEE》2008,12(5):24-31
The use of RESTful Web services has gained momentum in the development of distributed applications based on traditional Web standards such as HTTP. In particular, these services can integrate easily into various applications, such as mashups. Composing RESTful services into Web-scale workflows requires a lightweight composition language that's capable of describing both the control and data flow that constitute a workflow. The authors address these issues with Bite, a lightweight and extensible composition language that enables the creation of Web-scale workflows and uses RESTful services as its main composable entities. 相似文献
7.
Presents an obituary for David V. Smith, who succumbed to a brain tumor on September 30, 2006 at the age of 63. He was Simon R. Bruesch Professor and chair of the Department of Anatomy and Neurobiology and the director of the Neuroscience Institute at the University of Tennessee Health Science Center (UTHSC). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
Off-Site Exposure to Respirable Aerosols Produced during the Disk-Incorporation of Class B Biosolids
Swee Yang Low Tania Paez-Rubio Carolina Baertsch Matthew Kucharski Jordan Peccia 《Canadian Metallurgical Quarterly》2007,133(10):987-994
Field experiments were conducted at a Class B biosolids land application site in central Arizona to measure, model, and source-track the off-site transport of aerosols emitted when biosolids were disk-incorporated into soils. Real-time PM10 monitoring provided time-resolved aerosol information sufficient for verifying both off-site concentration and off-site exposure time model results. Under the conditions considered and at a distance of 165?m from the aerosol source, biosolids disk-incorporation resulted in an intermittent exposure to biosolids-derived aerosol concentration between 15 and 40?μg/m3 and an inhalable biosolids dose between 2 and 8?μg. Transport modeling predicted that these doses will decrease with increasing wind speed. In addition, three DNA sequence-based biosolids source tracking methods were applied to aerosol samples and confirmed the presence of biosolids in aerosols at 5, 65, and 165?m from the aerosol source. Field measurements and modeling indicate that the nature of biosolids-derived aerosol exposure is a series of intermittent high concentration puffs, rather than a continuous low concentration. 相似文献
9.
10.
J. Matthew Shumway 《Papers in Regional Science》1993,72(2):159-176
The length of time that individuals are unemployed has considerable political and policy significance. Important questions about the factors influencing the duration of unemployment remain to be answered. The purpose of this paper is to carry out an empirical investigation of the factors that cause unemployment to be of a longer or shorter duration. Such factors are identified within a micro-economic framework drawn from human capital and job search theories. Event history methods and panel data are used to model unemployment duration. The data come from the Survey of Income and Program Participation (SIPP) which contains weekly information on labor force status over about a two and a half year period, as well as data on a number of individual and locational attributes. Evidence from the empirical investigation suggests that migration, temporary layoff and income during unemployment combine with individual characteristics to influence the duration of unemployment spells.An earlier version of this paper was presented at the 38th North American Meetings of the RSAI, New Orleans, LA, November 1991. 相似文献