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   3688篇
  免费   48篇
  国内免费   14篇
电工技术   46篇
综合类   28篇
化学工业   141篇
金属工艺   9篇
机械仪表   105篇
建筑科学   45篇
矿业工程   13篇
能源动力   11篇
轻工业   385篇
水利工程   11篇
石油天然气   3篇
无线电   82篇
一般工业技术   148篇
冶金工业   2562篇
原子能技术   4篇
自动化技术   157篇
  2022年   19篇
  2021年   6篇
  2020年   18篇
  2019年   35篇
  2018年   10篇
  2017年   9篇
  2016年   11篇
  2015年   6篇
  2014年   12篇
  2013年   172篇
  2012年   39篇
  2011年   45篇
  2010年   44篇
  2009年   46篇
  2008年   49篇
  2007年   52篇
  2006年   37篇
  2005年   37篇
  2004年   29篇
  2003年   34篇
  2002年   20篇
  2000年   17篇
  1999年   95篇
  1998年   832篇
  1997年   481篇
  1996年   317篇
  1995年   170篇
  1994年   139篇
  1993年   168篇
  1992年   35篇
  1991年   37篇
  1990年   49篇
  1989年   50篇
  1988年   45篇
  1987年   59篇
  1986年   42篇
  1985年   46篇
  1984年   14篇
  1983年   10篇
  1982年   19篇
  1981年   28篇
  1980年   25篇
  1979年   16篇
  1978年   12篇
  1977年   66篇
  1976年   147篇
  1975年   7篇
  1973年   8篇
  1955年   18篇
  1954年   16篇
排序方式: 共有3750条查询结果,搜索用时 15 毫秒
41.
42.
Cookies enriched with 0, 5, 10, 15, 20, and 25% full-fat sweet lupine flour (FFSL) were evaluated by a sensory panel using the rank of preference and paired comparison tests. Cookies with 0, 5, and 10% FFSL were preferred while those containing 20 and 25% FFSL were rejected (p≤0.01). Studies conducted with school children showed similar acceptability for 0 and 10% FFSL-containing cookies which was different (p = 0.05) from those containing 20% FFSL. Fortification of the basic formula with 10% FFSL was recommended on the basis of acceptability.  相似文献   
43.
44.
Burkholderia pseudomallei is the causative agent of melioidosis, a disease increasingly recognized as an important cause of morbidity and mortality in many regions of the world. B. pseudomallei is a facultative intracellular pathogen capable of invading eukaryotic cells. We used Tn5-OT182 mutagenesis to generate mutants deficient in the ability to invade a human type II pneumocyte cell line (A549 cells). One of these mutants, AJ1D8, exhibited approximately 10% of the ability of the parental strain, 1026b, to invade A549 cells. There was no difference in the abilities of 1026b and AJ1D8 to resist killing by RAW macrophages or the human defensin HNP-1. The nucleotide sequence flanking the Tn5-OT182 integration in AJ1D8 was determined, and two open reading frames were identified. The predicted proteins shared considerable homology with two-component regulatory systems involved in the regulation of heavy-metal resistance in other organisms. AJ1D8 was 16-fold more sensitive to Cd2+ and twofold more sensitive to Zn2+ than was 1026b but was not sensitive to any of the other heavy metals examined. The B. pseudomallei two-component regulatory system, termed irlRS, complemented the invasion-deficient and heavy-metal-sensitive phenotype of AJ1D8 in trans. There was no significant difference between the virulence of AJ1D8 and that of 1026b in infant diabetic rats and Syrian hamsters, suggesting that the irlRS locus is probably not a virulence determinant in these animal models of acute B. pseudomallei infection.  相似文献   
45.
An experimental study was conducted to examine the effectiveness of sodium carbonate in alkali, surfactant and polymer combined slugs in recovering waterflood residual oil. The effects of sodium carbonate concentration on the slug viscosity, interfacial tension, and phase behavior were first examined. Core flood experiments were conducted with unfired linear Berea sandstone cores. The incremental oil recovery, oil cut, residual resistance factor, and chemical propagation were measured for each flood.A significant oil bank was formed for all combined slugs having sodium carbonate concentration ≥1 wt%. The incremental oil recovery, oil cut and the injectivity of the combined slugs greatly improved as sodium carbonate concentration was increased. The effect of sodium carbonate concentration on chemical propagation was dramatic for the synthetic surfactant; a slight delay in surfactant breakthrough and a much slower rate of surfactant propagation were observed at high sodium carbonate concentrations.The results obtained in the present study indicate that the residual oil was recovered by two mechanisms: low interfacial tension and wettability reversal. The former mechanism is dominant at sodium carbonate concentrations ≤1 wt%, whereas the latter plays an important role only at high sodium carbonate concentrations.  相似文献   
46.
47.
48.
Comments on R. L. Woolfolk and F. C. Richardson's (see record 1985-12614-001) discussion of the ideology of behavior therapy and their argument that behavior therapy cannot develop a conception of what might be appropriate goals of treatment. The present author contends that goals are as much a scientific question as are questions of technique. A scientific approach to the study of goal selection is presented that can be applied to any type of adjustment problem. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
49.
50.
介绍了卷烟信息网络防伪管理系统构建原理、技术特点和功能 ,及其在烟草行业中的应用。  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