全文获取类型
收费全文 | 9367篇 |
免费 | 868篇 |
国内免费 | 40篇 |
专业分类
电工技术 | 136篇 |
综合类 | 13篇 |
化学工业 | 2166篇 |
金属工艺 | 238篇 |
机械仪表 | 390篇 |
建筑科学 | 243篇 |
矿业工程 | 4篇 |
能源动力 | 404篇 |
轻工业 | 761篇 |
水利工程 | 32篇 |
石油天然气 | 4篇 |
无线电 | 1771篇 |
一般工业技术 | 2009篇 |
冶金工业 | 823篇 |
原子能技术 | 125篇 |
自动化技术 | 1156篇 |
出版年
2024年 | 13篇 |
2023年 | 92篇 |
2022年 | 155篇 |
2021年 | 226篇 |
2020年 | 195篇 |
2019年 | 235篇 |
2018年 | 315篇 |
2017年 | 251篇 |
2016年 | 373篇 |
2015年 | 312篇 |
2014年 | 417篇 |
2013年 | 678篇 |
2012年 | 510篇 |
2011年 | 662篇 |
2010年 | 527篇 |
2009年 | 535篇 |
2008年 | 515篇 |
2007年 | 414篇 |
2006年 | 389篇 |
2005年 | 320篇 |
2004年 | 307篇 |
2003年 | 269篇 |
2002年 | 253篇 |
2001年 | 225篇 |
2000年 | 196篇 |
1999年 | 211篇 |
1998年 | 318篇 |
1997年 | 236篇 |
1996年 | 182篇 |
1995年 | 137篇 |
1994年 | 116篇 |
1993年 | 82篇 |
1992年 | 61篇 |
1991年 | 60篇 |
1990年 | 60篇 |
1989年 | 55篇 |
1988年 | 39篇 |
1987年 | 46篇 |
1986年 | 49篇 |
1985年 | 33篇 |
1984年 | 26篇 |
1983年 | 28篇 |
1982年 | 8篇 |
1981年 | 20篇 |
1980年 | 20篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 18篇 |
1976年 | 25篇 |
1975年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Stefan Yoshi Buhmann Hassan Safari Dirk-Gunnar Welsch Ho Trung Dung 《Open Systems & Information Dynamics》2006,13(4):427-436
We establish a general relation between dispersion forces. First, based on QED in causal media, leading-order perturbation theory is used to express both the single-atom Casimir-Polder and the two-atom van der Waals potentials in terms of the atomic polarizabilities and the Green tensor for the body-assisted electromagnetic field. Endowed with this geometry-independent framework, we then employ the Born expansion of the Green tensor together with the Clausius-Mosotti relation to prove that the macroscopic Casimir-Polder potential of an atom in the presence of dielectric bodies is due to an infinite sum of its microscopic many-atom van der Waals interactions with the atoms comprising the bodies. This theorem holds for inhomogeneous, dispersing, and absorbing bodies of arbitrary shapes and arbitrary atomic composition on an arbitrary background of additional magnetodielectric bodies. 相似文献
63.
Carl A. Soderstrom Patricia C. Dischinger Gordon S. Smith J.Richard Hebel David R. McDuff David A. Gorelick Timothy J. Kerns Shiu M. Ho Kathleen M. Read 《Accident; analysis and prevention》1997,29(6):715-721
A structured in-depth interview employing standardized criteria was used to determine the prevalence of lifetime and current alcohol dependence (alcoholism) in unselected consecutive patients admitted to a regional Level I trauma center. Of 629 patients, 157 (25.0%) were current alcoholics at the time of injury. An additional 87 (13.8%) were diagnosed as lifetime non-current alcoholics. There was no significant difference in the rates of current alcohol dependence among patients injured in vehicular crashes (23.5%), other unintentional trauma victims (29.3%), and those injured as a result of violence (24.6%). Of BAC + (blood alcohol concentration positive) patients, 54.5% were current alcoholics. However, 14.4% of alcohol-negative patients were also diagnosed as alcohol dependent. 相似文献
64.
Shye Lin Wu Chung Len Lee Tan Fu Lei Chen C.F. Chen L.J. Ho K.Z. Ling Y.C. 《Electron Device Letters, IEEE》1994,15(4):120-122
In this study, it is demonstrated that the incorporation of fluorine can enhance poly-Si/Si interfacial oxide break-up in the poly-Si emitter contacted p+-n shallow junction formation. The annealing temperature for breaking up the poly-Si/Si interfacial oxide has been found to be as low as 900°C. As a result, the junction depth of the BF2-implanted device is much larger than that of the boron-implanted device 相似文献
65.
66.
This paper proposes two new methods for designing a class of two-channel perfect reconstruction (PR) finite impulse response (FIR) filterbanks (FBs) and wavelets with K-regularity of high order and studies its multiplier-less implementation. It is based on the two-channel structural PR FB proposed by Phoong et al (1995). The basic principle is to represent the K-regularity condition as a set of linear equality constraints in the design variables so that the least square and minimax design problems can be solved, respectively, as a quadratic programming problem with linear equality constraints (QPLC) and a semidefinite programming (SDP) problem. We also demonstrate that it is always possible to realize such FBs with sum-of-powers-of-two (SOPOT) coefficients while preserving the regularity constraints using Bernstein polynomials. However, this implementation usually requires long coefficient wordlength and another direct-form implementation, which can realize multiplier-less wavelets with K-regularity condition up to fifth order, is proposed. Several design examples are given to demonstrate the effectiveness of the proposed methods. 相似文献
67.
68.
69.
Low temperature heat capacity measurements have been made on hot isostatically pressed Nb3Sn and arc cast, homogenized, and A15 transformation annealed V-23.3 at. pct Ga and V-18.1 at. pct Ga. The heat capacity measurements
display the superconducting transition temperature (T
c), and have been used to evaluate the effects of plastic deformation on theT
c range. Plastic deformation to the extent of 15 pct compression at 1525 and 1650 °C does not alter the superconducting transition
in polycrystalline Nb3Sn. Plastic deformation to the extent of 15 pct compression at 1050 and 1200 °C does not alter the superconducting transition
in polycrystalline V-23.3Ga, transformed to A15 structure with a fifty-hour 1150 °C anneal. The same statement can be made
for A15 V-18.1Ga, deformed at 1050 °C after a fifty-hour, 1150 °C anneal. With onlyfive hours annealing at 1150 °C, A15 V-23.2Ga displays a lowering and broadening of theT
c range upon 1050 and 1200 °C plastic deformation. With onlyfive hours annealing at 1150 °C, A15 V-18.1Ga displays a broad, but increasedT
c range after plastic deformation at 1050 °C. 相似文献
70.
Sung Ho Jeong Joon Jeong Yi Jong Keun Kim Man Yeong Ha 《Journal of Mechanical Science and Technology》1991,5(1):16-21
A computer program to calculate the strip temperature heated in the continuous annealing furnace was developed, using the
zone method for radiative heat transfer analysis with the measured gas temperature in the furnace. Using theF
E Operator, the present study considered the effects of soot and transient species, in addition to the H2O−CO2 gas mixture on the gas radiative heat transfer. The predicted strip temperature distribution forF
E=1.05 represented well the measured data. The maximum difference in the heat flux transfered to the strip from the combustion
gas forF
E=1.0 (without soot and transient species gas radiation) and 1.05 (with soot and transient species gas radiation) was about
15%. The present study also investigated the effects of line speed and thickness variations on the strip temperature, establishing
the bases for the on-line computer model. 相似文献