全文获取类型
收费全文 | 8585篇 |
免费 | 542篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 133篇 |
综合类 | 24篇 |
化学工业 | 1797篇 |
金属工艺 | 187篇 |
机械仪表 | 192篇 |
建筑科学 | 439篇 |
矿业工程 | 40篇 |
能源动力 | 116篇 |
轻工业 | 1283篇 |
水利工程 | 41篇 |
石油天然气 | 12篇 |
无线电 | 651篇 |
一般工业技术 | 2453篇 |
冶金工业 | 353篇 |
原子能技术 | 74篇 |
自动化技术 | 1334篇 |
出版年
2023年 | 116篇 |
2022年 | 62篇 |
2021年 | 186篇 |
2020年 | 139篇 |
2019年 | 137篇 |
2018年 | 301篇 |
2017年 | 308篇 |
2016年 | 344篇 |
2015年 | 256篇 |
2014年 | 331篇 |
2013年 | 628篇 |
2012年 | 415篇 |
2011年 | 522篇 |
2010年 | 413篇 |
2009年 | 429篇 |
2008年 | 475篇 |
2007年 | 437篇 |
2006年 | 316篇 |
2005年 | 271篇 |
2004年 | 225篇 |
2003年 | 229篇 |
2002年 | 201篇 |
2001年 | 177篇 |
2000年 | 150篇 |
1999年 | 119篇 |
1998年 | 173篇 |
1997年 | 138篇 |
1996年 | 119篇 |
1995年 | 81篇 |
1994年 | 78篇 |
1993年 | 63篇 |
1992年 | 44篇 |
1991年 | 52篇 |
1990年 | 35篇 |
1989年 | 38篇 |
1988年 | 29篇 |
1987年 | 37篇 |
1986年 | 49篇 |
1985年 | 107篇 |
1984年 | 65篇 |
1983年 | 51篇 |
1982年 | 52篇 |
1981年 | 39篇 |
1980年 | 47篇 |
1979年 | 37篇 |
1978年 | 41篇 |
1976年 | 27篇 |
1974年 | 24篇 |
1973年 | 28篇 |
1943年 | 26篇 |
排序方式: 共有9129条查询结果,搜索用时 15 毫秒
11.
12.
13.
During the process of writing a comprehensive dictionary ofFinnish dialects, a large set of maps describing the regionaldistribution of the dialect words have been compiled in electronicform. In this article, we set out to analyse this corpus ofdata in order to gain new insight on the variation of Finnishdialects. We use a wide range of multivariate data analysismethods, including principal components analysis, independentcomponents analysis, clustering, and multidimensional scaling.We explain how to preprocess the data to overcome the problemof uneven sampling caused by the way the data has been collected.We discuss the results obtained by these methods and comparethem to the traditional view of Finnish dialect groups. 相似文献
14.
R. Hopfengärtner M. Lippert W. Dorsch H. Dietrich G. Kreiselmeyer G. Saemann-Ischenko 《Journal of Superconductivity and Novel Magnetism》1994,7(2):319-322
We report on measurements of the in-plane resistivityρ and Hall coefficientR H (B∥c) of various oxygen-deficient epitaxial films of YBa2Cu3O7?x in the normal state. The superconducting transition temperaturesT c of the samples vary from 14 to 90 K. Both the resistivity and the Hall coefficient exhibit a strong dependence on the oxygen content and the temperature. Asx increases,T c decreases continuously, whileρ andR H gradually increase in magnitude. Furthermore, also the characteristic linear dependences ofραT andR Hα T ?1 of the highly doped compounds changes to a nonlinear behavior for the samples withT c lower than 60 K. The unusual doping and temperature dependence ofR H will be compared to the predictions of our calculations, based on a two-dimensional tight-binding model using the relaxation-time approximation. The model considers also the next-nearest-neighbor hopping, which strongly influences the predicted Hall coefficient. Additionally, the cotangent of the Hall angle cot(Θ H ) is discussed in the framework of the two-dimensional Luttinger liquid theory. 相似文献
15.
16.
17.
In-Situ and Real-Time Investigation of Columnar-to-Equiaxed Transition in Metallic Alloy 总被引:1,自引:0,他引:1
H. Nguyen-Thi G. Reinhart N. Mangelinck-Noël H. Jung B. Billia T. Schenk J. Gastaldi J. Härtwig J. Baruchel 《Metallurgical and Materials Transactions A》2007,38(7):1458-1464
In this article, we present a review of observations during Al-3.5 wt pct Ni alloy solidi.cation experiments performed at
the European Synchrotron Radiation Facility (ESRF) in Grenoble. These experiments provide direct access to dynamical phenomena
during columnar growth (initial transient and breakdown of a planar solid-liquid interface), and for the first time to the
transition from columnar-to-equiaxed microstructure (nucleation ahead of a columnar front and blocking of a columnar front
by an equiaxed microstructure) and fully equiaxed growth (propagation of an effective front). Based on these experimental
observations, critical parameters such as columnar growth velocity variation during the transition or equiaxed-grain diameter
are measured and discussed.
This article is based on a presentation made in the symposium entitled “Solidi.cation Modeling and Microstructure Formation:
In Honor of Prof. John Hunt,” which occurred March 13–15, 2006, during the TMS Spring Meeting in San Antonio, Texas, under
the auspices of the TMS Materials Processing and Manufacturing Division, Solidification Committee. 相似文献
18.
F. -U. Gast P. S. Dittrich P. Schwille M. Weigel M. Mertig J. Opitz U. Queitsch S. Diez B. Lincoln F. Wottawah S. Schinkinger J. Guck J. Käs J. Smolinski K. Salchert C. Werner C. Duschl M. S. Jäger K. Uhlig P. Geggier S. Howitz 《Microfluidics and nanofluidics》2006,2(1):21-36
We describe a novel microfluidic perfusion system for high-resolution microscopes. Its modular design allows pre-coating of
the coverslip surface with reagents, biomolecules, or cells. A poly(dimethylsiloxane) (PDMS) layer is cast in a special molding
station, using masters made by photolithography and dry etching of silicon or by photoresist patterning on glass or silicon.
This channel system can be reused while the coverslip is exchanged between experiments. As normal fluidic connectors are used,
the link to external, computer-programmable syringe pumps is standardized and various fluidic channel networks can be used
in the same setup. The system can house hydrogel microvalves and microelectrodes close to the imaging area to control the
influx of reaction partners. We present a range of applications, including single-molecule analysis by fluorescence correlation
spectroscopy (FCS), manipulation of single molecules for nanostructuring by hydrodynamic flow fields or the action of motor
proteins, generation of concentration gradients, trapping and stretching of live cells using optical fibers precisely mounted
in the PDMS layer, and the integration of microelectrodes for actuation and sensing. 相似文献
19.
J. Riikonen A. Säynätjoki M. Sopanen H. Lipsanen J. Ahopelto 《Journal of Materials Science: Materials in Electronics》2003,14(5-7):403-405
The growth of GaAs on polycrystalline silicon-on-insulator (SOI) substrates by metal organic vapor phase epitaxy using a two-step growth process was studied in this work. We have compared the variation of the growth temperature and the thickness of the initial GaAs epilayer in the structures grown on polycrystalline SOI to ones grown on SOI and epi-Si. Structural properties were studied using high-resolution X-ray diffraction (XRD). The growth temperature had a strong effect on the FWHM of the (0 0 4) XRD curve in structures grown on SOI and epi-Si. In the case of polycrystalline SOI the effect was not as strong. Optical properties of the samples in which the optically active layer consisted of self-organized In0.5Ga0.5As quantum dots were investigated by photoluminescence measurements. The photoluminescence intensity from structures grown on polycrystalline SOI was comparable to that from structures grown on SOI and epi-Si. 相似文献
20.
In this paper, we summarize our recent efforts to analyze transmission probabilities of extremely thin SiO2 gate oxides using microscopic models of Si[100]-SiO2-Si[100] heterojunctions. We predict energy-dependent tunneling masses and their influence on transmission coefficients, discuss tunneling probabilities and analyze effects arising from the violation of parallel momentum conservation. As an application of the present method, gate currents in short bulk MOSFETs are calculated, including elastic defect-assisted contributions. 相似文献