首页 | 本学科首页   官方微博 | 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   710279篇
  免费   8941篇
  国内免费   1471篇
电工技术   12982篇
综合类   623篇
化学工业   106053篇
金属工艺   32329篇
机械仪表   23608篇
建筑科学   15615篇
矿业工程   5590篇
能源动力   17663篇
轻工业   53504篇
水利工程   9037篇
石油天然气   18140篇
武器工业   52篇
无线电   75987篇
一般工业技术   149279篇
冶金工业   120390篇
原子能技术   17596篇
自动化技术   62243篇
  2021年   6176篇
  2019年   6195篇
  2018年   14704篇
  2017年   14935篇
  2016年   13969篇
  2015年   7366篇
  2014年   12150篇
  2013年   31204篇
  2012年   19923篇
  2011年   28994篇
  2010年   23880篇
  2009年   25548篇
  2008年   26152篇
  2007年   26851篇
  2006年   19464篇
  2005年   19280篇
  2004年   17789篇
  2003年   17208篇
  2002年   15537篇
  2001年   14756篇
  2000年   13899篇
  1999年   13774篇
  1998年   34015篇
  1997年   24288篇
  1996年   18660篇
  1995年   14707篇
  1994年   13224篇
  1993年   13056篇
  1992年   10039篇
  1991年   9764篇
  1990年   9574篇
  1989年   9252篇
  1988年   9012篇
  1987年   8035篇
  1986年   7910篇
  1985年   8991篇
  1984年   8146篇
  1983年   7813篇
  1982年   7046篇
  1981年   7102篇
  1980年   6906篇
  1979年   7026篇
  1978年   6915篇
  1977年   7611篇
  1976年   9388篇
  1975年   6211篇
  1974年   5947篇
  1973年   6079篇
  1972年   5280篇
  1971年   4907篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Journal of Materials Science: Materials in Electronics - The Co1?xZnxFe2O4 (Co–Zn) ferrite nanoparticles with x varying from 0.0 to 0.4 have been manufactured by facile chemical...  相似文献   
2.
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   
3.
Journal of Engineering Physics and Thermophysics - The generalized nonlocal thermoelastic model in the context of Eringen’s nonlocal elasticity is applied to investigate the...  相似文献   
4.
In the present study, a prebiotic acerola juice containing gluco-oligosaccharides and dextran was produced and processed by high-intensity ultrasound (HIUS). After a simulated in vitro digestion, the gluco-oligosaccharides and dextran maintained 90% and 80% of their initial concentration in all prebiotic’s juices. At the same time, Vitamin C and phenolic compounds concentration increased significantly by 19% and 7% (P < 0.05). After the in vitro digestion, the prebiotic juice HIUS processed by 10 min showed the highest increase in gluco-oligosaccharides and bioactive compound concentrations. The HIUS processing imparted some dextran hydrolysis and improved its fermentability by Lacticaseibacillus casei. Gluco-oligosaccharides were extensively consumed as substrate in simulated intestinal conditions, promoting the L. casei NRRL B-442 growth and production of organic acids and short-chain organic acids. The prebiotic juice HIUS processed for 6 min showed the best responses regarding the metabolism of L. casei NRRL B-442. The results showed high-intensity ultrasound processed acerola juices containing gluco-oligosaccharides and dextran as a prebiotic food.  相似文献   
5.
Inorganic Materials - We have studied the effect of annealing on the chemical and physical properties of mineral-like host matrices for immobilization of the rare-earth–actinide fraction from...  相似文献   
6.
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   
7.
Wireless Personal Communications - Breast cancer is one of the rapid spreading diseases resulting in the death of younger age group of women. Unfortunately, as the detection of cancer is at later...  相似文献   
8.
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   
9.
10.
Theoretical Foundations of Chemical Engineering - The reaction of nickel(II) hydroxide and a mixed ammonia–carbonate solution to form nickel(II) aqua–ammonia complexes is studied in the...  相似文献   
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