全文获取类型
收费全文 | 4938篇 |
免费 | 241篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 56篇 |
综合类 | 9篇 |
化学工业 | 1249篇 |
金属工艺 | 85篇 |
机械仪表 | 81篇 |
建筑科学 | 242篇 |
矿业工程 | 8篇 |
能源动力 | 171篇 |
轻工业 | 374篇 |
水利工程 | 28篇 |
石油天然气 | 9篇 |
无线电 | 518篇 |
一般工业技术 | 970篇 |
冶金工业 | 353篇 |
原子能技术 | 26篇 |
自动化技术 | 1004篇 |
出版年
2023年 | 70篇 |
2022年 | 92篇 |
2021年 | 169篇 |
2020年 | 116篇 |
2019年 | 110篇 |
2018年 | 129篇 |
2017年 | 118篇 |
2016年 | 175篇 |
2015年 | 130篇 |
2014年 | 222篇 |
2013年 | 314篇 |
2012年 | 338篇 |
2011年 | 411篇 |
2010年 | 286篇 |
2009年 | 262篇 |
2008年 | 274篇 |
2007年 | 271篇 |
2006年 | 219篇 |
2005年 | 190篇 |
2004年 | 149篇 |
2003年 | 104篇 |
2002年 | 108篇 |
2001年 | 78篇 |
2000年 | 80篇 |
1999年 | 77篇 |
1998年 | 110篇 |
1997年 | 82篇 |
1996年 | 65篇 |
1995年 | 50篇 |
1994年 | 51篇 |
1993年 | 37篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 12篇 |
1975年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有5183条查询结果,搜索用时 0 毫秒
1.
Olivier Merlin Jeffrey P. Walker Abdelghani Chehbouni Yann Kerr 《Remote sensing of environment》2008,112(10):3935-3946
A deterministic approach for downscaling ~ 40 km resolution Soil Moisture and Ocean Salinity (SMOS) observations is developed from 1 km resolution MODerate resolution Imaging Spectroradiometer (MODIS) data. To account for the lower soil moisture sensitivity of MODIS surface temperature compared to that of L-band brightness temperature, the disaggregation scale is fixed to 10 times the spatial resolution of MODIS thermal data (10 km). Four different analytic downscaling relationships are derived from MODIS and physically-based model predictions of soil evaporative efficiency. The four downscaling algorithms differ with regards to i) the assumed relationship (linear or nonlinear) between soil evaporative efficiency and near-surface soil moisture, and ii) the scale at which soil parameters are available (40 km or 10 km). The 1 km resolution airborne L-band brightness temperature from the National Airborne Field Experiment 2006 (NAFE'06) are used to generate a time series of eleven clear sky 40 km by 60 km near-surface soil moisture observations to represent SMOS pixels across the three-week experiment. The overall root mean square difference between downscaled and observed soil moisture varies between 1.4% v/v and 1.8% v/v depending on the downscaling algorithm used, with soil moisture values ranging from 0 to 15% v/v. The accuracy and robustness of the downscaling algorithms are discussed in terms of their assumptions and applicability to SMOS. 相似文献
2.
3.
Service-centric software system is a multidisciplinary paradigm concerned with software systems that are constructed as compositions of autonomous services. These systems extend the service-oriented architecture paradigm by focusing on the design, development, and maintenance of software built under SOAs. In this special issue, we present five articles that tackle service-centric software systems. 相似文献
4.
5.
Kraut E.A. Olivier J.C. West J.B. 《Antennas and Propagation, IEEE Transactions on》1994,42(12):1646-1648
The finite-difference time-domain (FDTD) method is applied to predict reflection coefficients for edge slots penetrating the adjacent broadsides of thick nailed rectangular X-band waveguides. Measured and calculated values S11 are compared to experiment for waveguides terminated by shorted loads 相似文献
6.
KristieValdez OlivierMeilhon 《电子设计应用》2004,(4):69-72
本文用一种创新的方法提出了四种功率因数校正(PFC)电路设计。两种临界导通模式(CRM)升压.一种连续导通模式(CCM)升压和一种CCM单段回扫,并且推荐了基于功率要求、效率、失真程度、电路板空间和成本限制的解决方案。 相似文献
7.
Auguste Commeyras Hlne Collet Laurent Boiteau Jacques Taillades Odile Vandenabeele‐Trambouze Herv Cottet Jean‐Philippe Biron Raphaël Plasson Louis Mion Olivier Lagrille Herv Martin Franck Selsis Michel Dobrijevic 《Polymer International》2002,51(7):661-665
Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry. 相似文献
8.
Volmer C. Weber J. Stephan R. Blau K. Hein M.A. 《Antennas and Propagation, IEEE Transactions on》2008,56(2):360-370
Placing the radiators of antenna arrays closer than aggravates the problem of power mismatch. Based on efficiency considerations, a general analysis of this effect is presented, putting forward a simple tool to quantify, compare, and optimize the performance of antenna arrays. This analysis is not restricted with respect to the number of radiators or the degree of compactness. In order to improve power matching, a systematic approach for the design of lossless decoupling and matching networks based on 180 directional couplers is suggested for up to eight radiators. Implications of network losses, which have not yet received appropriate attention by researchers in the past, will be analyzed and discussed by means of a manufactured three-element prototype array. 相似文献
9.
Stephan Boden Martina Bieberle Uwe Hampel 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2008,139(2):351-362
Cone-beam type X-ray computed tomography (CBCT) is a potential method to measure three-dimensional phase distributions in vessels. An example for that is the measurement of gas profiles in stirred chemical reactors. Such data are highly valuable for the assessment and evaluation of chemical processes, for optimisation of the reactor and stirrer design, and for evaluation of computational fluid dynamics codes used to model the fluid flow and heat transfer in reactive systems. However, there are considerable difficulties for accurate quantitative measurements due to beam hardening and radiation scattering effects. In a theoretical and experimental work we have investigated the non-linear effects of both physical phenomena and developed a suitable measurement setup as well as calibration and software correction methods to achieve a highly accurate measurement of void fraction profiles with CBCT. 相似文献
10.