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   206689篇
  免费   3598篇
  国内免费   1049篇
电工技术   3954篇
综合类   583篇
化学工业   29781篇
金属工艺   8531篇
机械仪表   6456篇
建筑科学   5324篇
矿业工程   1558篇
能源动力   5393篇
轻工业   17659篇
水利工程   2471篇
石油天然气   4323篇
武器工业   72篇
无线电   24338篇
一般工业技术   41186篇
冶金工业   37639篇
原子能技术   5165篇
自动化技术   16903篇
  2021年   1954篇
  2020年   1448篇
  2019年   1828篇
  2018年   2851篇
  2017年   2953篇
  2016年   3107篇
  2015年   2164篇
  2014年   3517篇
  2013年   9583篇
  2012年   5609篇
  2011年   7620篇
  2010年   6103篇
  2009年   6857篇
  2008年   6909篇
  2007年   6939篇
  2006年   6013篇
  2005年   5617篇
  2004年   5266篇
  2003年   5130篇
  2002年   4739篇
  2001年   4830篇
  2000年   4749篇
  1999年   4884篇
  1998年   11511篇
  1997年   8239篇
  1996年   6501篇
  1995年   4750篇
  1994年   4339篇
  1993年   4132篇
  1992年   3253篇
  1991年   3119篇
  1990年   2897篇
  1989年   2974篇
  1988年   2810篇
  1987年   2371篇
  1986年   2288篇
  1985年   2696篇
  1984年   2480篇
  1983年   2310篇
  1982年   2061篇
  1981年   2187篇
  1980年   2014篇
  1979年   2101篇
  1978年   2101篇
  1977年   2349篇
  1976年   3163篇
  1975年   1815篇
  1974年   1740篇
  1973年   1762篇
  1972年   1439篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Two experiments examined how cross-list directional associations influenced list-method directed forgetting and the degree of interference observed on each list. Each List 1 item had a (a) bidirectionally related item on List 2 (chip ←→ potato), (b) forward association with an item on List 2 (chip → wood), (c) backward association from an item on List 2 (chip ← chisel), or (d) no relationship with List 2 items. The results revealed that associative relationships that eliminated retroactive interference in the baseline condition also eliminated the directed forgetting costs. In contrast, associative relationships did not affect List 2 recall in the forget group, which remained unchanged across experimental conditions. However, certain conditions reduced proactive interference in the remember group, thereby eliminating the benefits of directed forgetting. The directed forgetting costs and benefits were observed independently of each other. The authors propose that these effects emerged from a combination of item and context strengthening induced by different associative directions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
992.
The emulsifying effect of a polyethylene-based ionomer on the phase size/composition relationship was studied for polypropylene/polyamide and polyethylene/polyamide blends. The particle size measured for the uncompatibilized blends increased with minor phase concentration, particularly as the region of dual phase continuity was approached. This relationship was less pronounced when ionomer was added, and the dimensions of the dispersed phase were significantly reduced. A narrowing of the region of dual phase continuity was observed due to the addition of ionomer. An increase in the torque measured during melt blending in a Brabender mixing chamber resulted when ionomer was added, due to the increase in the interactions at the interface. The particle size determined for the uncompatibilized blends increased with viscosity ratio. The effect was also less pronounced for the compatibilized blends. From these observations, it was possible to conclude that the effect of interfacial modification on morphology predominates over that of composition and viscosity ratio. The effects were interpreted in terms of the reduction of interfacial mobility due to the compatibilization.  相似文献   
993.
The applicability of fluidised-bed reactor (FBR) based sulphate reducing bioprocess was investigated for the treatment of iron containing (40-90 mg/L) acidic wastewater at 65 degrees C. The FBR was inoculated with sulphate-reducing bacteria (SRB) originally enriched from a hot mining environment. Ethanol or acetate was supplemented as carbon and electron source for the SRB. A rapid startup with 99.9, 46 and 29% ethanol, sulphate and acetate removals, in respective order, was observed even after 6 days. Iron was almost completely removed with a rate of 90 mg/L.d. The feed pH was decreased gradually from its initial value of 6 to around 3.7 during 100 days of operation. The wastewater pH of 4.3-4.4 was neutralised by the alkalinity produced in acetate oxidation and the average effluent pH was 7.8 +/- 0.8. Although ethanol removal was complete, acetate accumulated. Later the FBR was fed with acetate only. Although acetate was present in the reactor for 295 days, its oxidation rates did not improve, which may be due to low growth rate and poor attachment ability of acetate oxidising SRB. Hence, the oxidation of acetate is the rate limiting step in the sulphidogenic ethanol oxidation by the thermophilic SRB.  相似文献   
994.
995.
The Open Channel     
Estell  B. 《Computer》1987,20(11):90-91
  相似文献   
996.
997.
Translated from Khimiya i Tekhnoloyiya Topliv i Masel, No. 3, pp. 3–5, March, 1989.  相似文献   
998.
The milling industry faces the task of saving energy without impairing the quantity and quality of the products. By applying experimental plans for the optimization of several effect variables, approximations (compromise solutions) between the cause variables (conditioning parameters) and the effect variables (quantity and quality parameters) are sought, which satisfy the aims laid down.  相似文献   
999.
1000.
Most of the UK nuclear power reactors are gas-cooled and graphite moderated. As well as acting as a moderator the graphite also acts as a structural component providing channels for the coolant gas and control rods. For this reason the structural integrity assessments of nuclear graphite components is an essential element of reactor design. In order to perform graphite component stress analysis, the definition of the constitutive equation relating stress and strain for irradiated graphite is required. Apart from the usual elastic and thermal strains, irradiated graphite components are subject to additional strains due to fast neutron irradiation and radiolytic oxidation. In this paper a material model for nuclear graphite is presented along with an example of a stress analysis of a nuclear graphite moderator brick subject to both fast neutron irradiation and radiolytic oxidation.  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