全文获取类型
收费全文 | 2929篇 |
免费 | 122篇 |
国内免费 | 37篇 |
专业分类
电工技术 | 88篇 |
综合类 | 14篇 |
化学工业 | 418篇 |
金属工艺 | 57篇 |
机械仪表 | 76篇 |
建筑科学 | 128篇 |
矿业工程 | 1篇 |
能源动力 | 114篇 |
轻工业 | 228篇 |
水利工程 | 26篇 |
石油天然气 | 11篇 |
武器工业 | 1篇 |
无线电 | 610篇 |
一般工业技术 | 515篇 |
冶金工业 | 403篇 |
原子能技术 | 25篇 |
自动化技术 | 373篇 |
出版年
2023年 | 14篇 |
2022年 | 56篇 |
2021年 | 51篇 |
2020年 | 27篇 |
2019年 | 36篇 |
2018年 | 57篇 |
2017年 | 55篇 |
2016年 | 58篇 |
2015年 | 65篇 |
2014年 | 112篇 |
2013年 | 186篇 |
2012年 | 154篇 |
2011年 | 185篇 |
2010年 | 130篇 |
2009年 | 135篇 |
2008年 | 155篇 |
2007年 | 126篇 |
2006年 | 136篇 |
2005年 | 92篇 |
2004年 | 84篇 |
2003年 | 69篇 |
2002年 | 82篇 |
2001年 | 65篇 |
2000年 | 65篇 |
1999年 | 70篇 |
1998年 | 170篇 |
1997年 | 119篇 |
1996年 | 70篇 |
1995年 | 61篇 |
1994年 | 57篇 |
1993年 | 64篇 |
1992年 | 36篇 |
1991年 | 22篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 19篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1977年 | 6篇 |
1975年 | 13篇 |
1974年 | 7篇 |
1972年 | 6篇 |
1967年 | 5篇 |
1965年 | 6篇 |
排序方式: 共有3088条查询结果,搜索用时 15 毫秒
31.
Fast clustering process for vector quantisation codebook design 总被引:1,自引:0,他引:1
A fast clustering process is introduced to the generalised Lloyd algorithm for vector quantisation codebook design. Simulations show that the proposed codebook design method achieves significant saving in computational time and similar qualitative performance to that of the conventional full-search approach 相似文献
32.
33.
Y.-Y. Lin S.-P. Lo 《The International Journal of Advanced Manufacturing Technology》2004,23(9-10):644-650
In this paper, relative velocity at a given point on the wafer was first derived. The revolutions of wafer and pad are assumed the same and the axisymmetric uniformly distributed pressure form is given. Thus, a 2D axisymmetric quasic-static model for chemical-mechanical polishing process (CMP) was established. Based on the principle of minimum total potential energy and axisymmetric elastic stress-strain relations, a 2D axisymmetric quasic-static finite element model for CMP was thus established. In this model, the four-layer structures including wafer carrier, carrier film, wafer and pad are involved. The von Mises stress distributions on the wafer surface were analysed, the effects of axial, hoop, radial and shear stresses to von Mises stress and the effects of axial, hoop, radial and shear strains to deformation of the wafer were investigated. The findings indicate that near the wafer centre, von Mises stress distribution on the wafer surface was almost uniform, then increased gradually with a small amount. However, near the wafer edge, it would decrease in a large range. Finally, it would increase dramatically and peak significantly at the edge. Besides, the axial stress and strain are the dominant factors to the von Mises stress distributions on the wafer surface and the wafer deformation, respectively. 相似文献
34.
CMOS scaling into the nanometer regime 总被引:11,自引:0,他引:11
Yuan Taur Buchanan D.A. Wei Chen Frank D.J. Ismail K.E. Shih-Hsien Lo Sai-Halasz G.A. Viswanathan R.G. Wann H.-J.C. Wind S.J. Hon-Sum Wong 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1997,85(4):486-504
Starting with a brief review on 0.1-μm (100 nm) CMOS status, this paper addresses the key challenges in further scaling of CMOS technology into the nanometer (sub-100 nm) regime in light of fundamental physical effects and practical considerations. Among the issues discussed are: lithography, power supply and threshold voltage, short-channel effect, gate oxide, high-field effects, dopant number fluctuations and interconnect delays. The last part of the paper discusses several alternative or unconventional device structures, including silicon-on-insulator (SOI), SiGe MOSFET's, low-temperature CMOS, and double-gate MOSFET's, which may lead to the outermost limits of silicon scaling 相似文献
35.
AC hot-carrier effects in n-MOSFETs with thin (~85 Å) N2O-nitrided gate oxides have been studied and compared with control devices with gate oxides grown in O2. Results show that furnace N2O-nitrided oxide devices exhibit significantly reduced AC-stress-induced degradation. In addition, they show weaker dependences of device degradation on applied gate pulse frequency and pulse width. Results suggest that the improved AC-hot-carrier immunity of the N2O-nitrided oxide device may be due to the significantly suppressed interface state generation and neutral electron trap generation during stressing 相似文献
36.
Experimental demonstration of multiwavelength optical network with microwave subcarriers 总被引:1,自引:0,他引:1
The authors use the unique multiwavelength filtering capability of the acousto-optic tunable filter to demonstrate multiple broadband services with only one fixed-wavelength transmitter and receiver per user in the first experimental demonstration of a multiwavelength subcarrier network.<> 相似文献
37.
Eslami Vahideh Ashofteh Parisa-Sadat Golfam Parvin Loáiciga Hugo A. 《Water Resources Management》2021,35(12):4085-4110
Water Resources Management - Environmental Impact Assessments (EIAs) of development projects are necessary to minimize negative impacts and maximize benefits. The objective of this paper is to... 相似文献
38.
Fatty acid monoesters of propylene glycol (1,2-propanediol) are good water-in-oil emulsifiers. These esters were synthesized
enzymatically to overcome the problems associated with chemical processes. APseudomonas lipase was added to reaction mixtures containing propylene glycol and various acyl donors (fatty acids, fatty acid ethyl
esters, fatty acid anhydrides and triglycerides) in organic solvents, and the mixtures were shaken at 30°C. The products were
analyzed by gas chromatography. The yield of monoesters was affected by the acyl donors, organic solvents, temperature, water
content, pH memory and reaction time. The anhydrous (lyophilized) enzyme and fatty acid anhydrides were best for monoester
production. The optimum pH ranges were 4–5 and 8–10. The yields of propylene glycol monolaurate, monomyristate, monopalmitate,
monostearate and monooleate with 50 mM fatty acid anhydrides as acyl donors were 97.2, 79.6, 83.7, 89.7 and 93.4 mM, respectively;
those with 50 mM fatty acids as acyl donors were 37.3, 28.7, 28.7, 35.3 and 36.2 mM, respectively. The yields of propylene
glycol monopalmitate, monostearate and monooleate with 50 mM triglycerides as acyl donors were 87.4, 65.1 and 83.2 mM, respectively. 相似文献
39.
Ten trace elements (Cr, Zn, Fe, Mn, Cu, Co, Ni, Mo, V and Sr) and sulfur were determined in the saturate, aromatic and resin fractions of 15 crude oils from Mara (DM) and Mara Oeste (DMO) fields of the Maracaibo Basin, Venezuela. The oils studied are classified as unaltered or altered by biodegradation. In the altered oil, the depletion of n-alkanes, the absence of isoprenoids and the presence of steranes and hopanes unaltered by biodegradation are indicative of moderate biodegradation. The elements Zn, Fe, Mn, Cu, Ni, and Sr were detected in the saturated hydrocarbon fraction; Cr and V were detected in the aromatic fraction in addition to the above elements; whereas the elements detected for the resin fraction were Cr, Zn, Fe, Cu, Ni, Mo, V, and Sr. Co was not detected in any fractions of the oils analyzed. Sulfur was found in all fractions of the oils studied. It was proposed that Fe, Zn, Sr, and Mn could have entered the oil during migration or Fe, Zn and Mn as pollutants during oil extraction. Cr and Cu may be of biological origin and Mo could be incorporated into the reservoir through bacteria. Only S, V, and Ni in the resin fractions can be used as indicators of the origin and correlation of Mara and Mara Oeste oils. Based on the results obtained in this work, it can be established that the V/(V+Ni) ratio in the resin fraction can be used as a correlation parameter, for these oils. 相似文献
40.
Fu-Ping Zhang Jin-Mei Du Yu-Sheng Liu Hong-Liang He 《Journal of the American Ceramic Society》2007,90(8):2639-2641
Shock-induced depoling of the ferroelectric (FE) ceramic PZT 95/5 is utilized in a number of pulsed power devices. Nondestructive testing of remanent polarization of PZT 95/5 is developed by pyroelectric effect in this paper. Approximately linear relation between the change of polarization during low- to high-temperature rhombohedral FE phase and the remanent polarization was found through pyroelectricity of a single piece of PZT 95/5 ceramics. The change of polarization of a prototype for shock-driven pulsed power during the FEHT ↔FELT phase transformation was also investigated through directly measuring the pyroelectric current. Results indicate that pyroelectric effect caused by the reversible FEHT –FELT phase transition could be used as a non-destructive inspection for the remanent polarization of a prototype about shock-driven pulsed power supply. 相似文献