首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   208747篇
  免费   4531篇
  国内免费   733篇
工业技术   214011篇
  2021年   1992篇
  2020年   1577篇
  2019年   1860篇
  2018年   3442篇
  2017年   3446篇
  2016年   3609篇
  2015年   2564篇
  2014年   3965篇
  2013年   10220篇
  2012年   6642篇
  2011年   8300篇
  2010年   6563篇
  2009年   7211篇
  2008年   7451篇
  2007年   7237篇
  2006年   6053篇
  2005年   5568篇
  2004年   5278篇
  2003年   4829篇
  2002年   4523篇
  2001年   4250篇
  2000年   3970篇
  1999年   4311篇
  1998年   12793篇
  1997年   8756篇
  1996年   6457篇
  1995年   4848篇
  1994年   4132篇
  1993年   4059篇
  1992年   2761篇
  1991年   2704篇
  1990年   2580篇
  1989年   2583篇
  1988年   2500篇
  1987年   2238篇
  1986年   2201篇
  1985年   2543篇
  1984年   2320篇
  1983年   2100篇
  1982年   1998篇
  1981年   2083篇
  1980年   1910篇
  1979年   1911篇
  1978年   1865篇
  1977年   2265篇
  1976年   3034篇
  1975年   1622篇
  1974年   1595篇
  1973年   1660篇
  1972年   1382篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
Journal of Materials Science: Materials in Electronics - The ZnO and TiO2 nanopowders have been prepared by means of the pulsed laser reactive ablation of metallic (Zn, Ti) targets. The Structural,...  相似文献   
2.
Semiconductors - The results of the effect of irradiation with Ar ions on the structural, electrophysical, and optical characteristics of ultraviolet Cr/4H-SiC photodetectors in the spectral range...  相似文献   
3.
Chemistry and Technology of Fuels and Oils - This article considers the alternatives for treatment of the raffinate produced at a unit for the extraction of benzene-containing fractions and the...  相似文献   
4.
In the current work, numerical simulations are achieved to study the properties and the characteristics of fluid flow and heat transfer of (Cu–water) nanofluid under the magnetohydrodynamic effects in a horizontal rectangular canal with an open trapezoidal enclosure and an elliptical obstacle. The cavity lower wall is grooved and represents the heat source while the obstacle represents a stationary cold wall. On the other hand, the rest of the walls are considered adiabatic. The governing equations for this investigation are formulated, nondimensionalized, and then solved by Galerkin finite element approach. The numerical findings were examined across a wide range of Richardson number (0.1 ≤ Ri ≤ 10), Reynolds number (1 ≤ Re ≤ 125), Hartmann number (0 ≤ Ha ≤ 100), and volume fraction of nanofluid (0 ≤ φ ≤ 0.05). The current study's findings demonstrate that the flow strength increases inversely as the Reynolds number rises, which pushes the isotherms down to the lower part of the trapezoidal cavity. The Nuavg rises as the Ri rise, the maximum Nuavg = 10.345 at Ri = 10, Re = 50, ϕ = 0.05, and Ha = 0; however, it reduces with increasing Hartmann number. Also, it increase by increasing ϕ, at Ri = 10, the Nuavg increased by 8.44% when the volume fraction of nanofluid increased from (ϕ = 0–0.05).  相似文献   
5.
Chemistry and Technology of Fuels and Oils - The review examines biomass of animal origin in terms of a potential renewable raw material for obtaining CO2-neutral fuel unaffecting the carbon...  相似文献   
6.
Brito  Claúdia  Esteves  Marisa  Peixoto  Hugo  Abelha  António  Machado  José 《Wireless Networks》2022,28(3):1269-1277
Wireless Networks - Continuous ambulatory peritoneal dialysis (CAPD) is a treatment used by patients in the end-stage of chronic kidney diseases. Those patients need to be monitored using blood...  相似文献   
7.
Russian Engineering Research - Systems are considered for the dehydration of petroleum so as to separate water–petroleum emulsions. In particular, the low-temperature microwave (UHF)...  相似文献   
8.
9.

Particles generated by wood machining have a proven impact on the health of users and woodworkers. The aim of this study was to quantify and describe wood particles in solid and gas phases to reliably and reproducibly characterise these emissions. First, we developed an experimental device that produced particles from solid wood and wood-based panels using portable machine tools. The objective was to study the particles emitted by wood machining while avoiding ambient pollution. Based on own technical specifications, the experimental system was defined and composed of various elements that integrated treatment of inlet air through wood machining to the analysis section that allows solid and gas phases. The first experiments were carried out in sanding and sawing modes on materials used in construction, including solid wood (spruce) and composite panels (particle board (PB), oriented strand board (OSB), and medium density fibreboard (MDF)). Wood-based panels showed more emissive behaviour than solid wood, both for the solid phase and the gas phase. These tests validate the feasibility of generating and measuring particles and emissions of volatile organic compounds (VOCs). Further modifications to the experimental device would enable us to integrate additional devices, such as toxicological ones, to better understand the impact of these wood particles on the health of woodworkers.

  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号