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   9064篇
  免费   194篇
  国内免费   10篇
电工技术   93篇
综合类   13篇
化学工业   1799篇
金属工艺   140篇
机械仪表   116篇
建筑科学   498篇
矿业工程   50篇
能源动力   213篇
轻工业   827篇
水利工程   109篇
石油天然气   59篇
无线电   559篇
一般工业技术   1240篇
冶金工业   2436篇
原子能技术   103篇
自动化技术   1013篇
  2022年   83篇
  2021年   122篇
  2020年   99篇
  2019年   97篇
  2018年   111篇
  2017年   109篇
  2016年   127篇
  2015年   112篇
  2014年   171篇
  2013年   445篇
  2012年   295篇
  2011年   363篇
  2010年   292篇
  2009年   314篇
  2008年   373篇
  2007年   364篇
  2006年   320篇
  2005年   271篇
  2004年   244篇
  2003年   253篇
  2002年   224篇
  2001年   158篇
  2000年   152篇
  1999年   153篇
  1998年   175篇
  1997年   151篇
  1996年   154篇
  1995年   166篇
  1994年   154篇
  1993年   148篇
  1992年   144篇
  1991年   105篇
  1990年   123篇
  1989年   133篇
  1988年   135篇
  1987年   124篇
  1986年   133篇
  1985年   160篇
  1984年   141篇
  1983年   130篇
  1982年   135篇
  1981年   140篇
  1980年   101篇
  1979年   134篇
  1978年   125篇
  1977年   113篇
  1976年   107篇
  1975年   93篇
  1974年   101篇
  1973年   103篇
排序方式: 共有9268条查询结果,搜索用时 15 毫秒
111.
Interest in marketing soybeans on the basis of protein and oil content is increasing. Producers, breeders, handlers and buyers of soybeans need a method of evaluating soybean lots of different composition. A model is presented that predicts, given soybean composition and processing conditions, the yield of crude soybean oil and soybean meal from the processing of soybeans in a solvent extraction plant. From these yields, an estimated processed value (EPV) was calculated. For one set of price conditions, the EPV of typical soybeans had a range of $0.93 per bushel if premiums were paid for meal protein in excess of specifications and a range of $0.53 per bushel if meal protein premiums were not paid. Trading rules established by the National Oilseed Processors Association for domestic meal markets have a significant effect on the value and composition of soybean meal.  相似文献   
112.
Administered tests of R. B. Cattel's (1965, 1971) fluid and crystallized intelligence and ergs and sentiments (e.g., Culture Fair Intelligence Test and the School Motivation Analysis Test), and the Torrance Tests of Creative Thinking to 163 9th graders. Results support the hypothesized distinction between fluid and crystallized intelligence, but they indicate that the distinction between ergs (defined as traits reflecting basic biological needs for emotional expression) and sentiments (defined as source traits which come into existence because of an individual's contacts with important cultural institutions) may be more conceptual than empirical. Multivariate analyses of these results and achievement data substantiate the importance of institutionally learned intellectual skills in both achievement and creativity. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
113.
Investigated the applicability of a "vicarious behavior induction" (VBI) strategy to a residential treatment program for heroin addicts. This strategy was tested using a "videomodel" procedure, in which Ss viewed a series of videotapes developed to depict a model exhibiting "coping" behavior in solving problems related to maintaining drug abstinence (i.e., accepting help, job interviewing, capitalizing on street skills). These results were compared to those obtained from Ss who had viewed a videotaped lecture about coping behavior ("videolecture"). 22 Black heroin addicts from an urban community-based residential drug-abuse treatment program were randomly assigned to either a videomodel or videolecture group. In small subgroups they discussed their respective videotapes with an ex-addict paraprofessional and the E. Ss who participated in the videomodeling group had substantially better vocational outcomes 30, 90 and 180 days after treatment than those who participated in the videolecture group. Advantages of the VBI behavior change strategy are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
114.
The high temperature stress rupture process in polycrystalline solids is examined in terms of grain boundary parting by vacancy condensation at the tip of a crack within the boundary. The gradient for diffusion of these defects is considered in the model to arise from the stress gradient in advance of the flaw tip. A rupture stress function is derived which is shown to closely describe the stress rupture behavior of a number of metals and high temperature alloys.  相似文献   
115.
FemaleExoneura richardsoni, E. bicolor, andE. bicincta (Hymenoptera: Anthophoridae) release a pungent, staining liquid from their mandibular glands upon disturbance. This secretion is primarily composed of ethyl dodecanoate, with lesser amounts of homologous ethyl and methyl esters, salicylaldehyde, and 1,4-benzoquinone. The secretion elicits vigorous grooming when topically applied to antennae ofFormica ants. The shared, unique combination of mandibular gland lipids of these threeExoneura species supports their monophyletic classification, while the presence of salicylaldehyde may associateExoneura (Allodapini) withPithitis (Ceratinini).  相似文献   
116.
The reactive aldehyde acrolein is a ubiquitous environmental pollutant and is also generated endogenously. It is a strong electrophile and reacts rapidly with nucleophiles including thiolates. This review focuses on the effects of acrolein on thioredoxin reductase (TrxR) and thioredoxin (Trx), which are major regulators of intracellular protein thiol redox balance. Acrolein causes irreversible effects on TrxR and Trx, which are consistent with the formation of covalent adducts to selenocysteine and cysteine residues that are key to their activity. TrxR and Trx are more sensitive than some other redox-sensitive proteins, and their prolonged inhibition could disrupt a number of redox-sensitive functions in cells. Among these effects are the oxidation of peroxiredoxins and the activation of apoptosis signal regulating kinase (ASK1). ASK1 promotes MAP kinase activation, and p38 activation contributes to apoptosis and a number of other acrolein-induced stress responses. Overall, the disruption of the TrxR/Trx system by acrolein could be significant early and prolonged events that affect many aspects of redox-sensitive signaling and oxidant stress.  相似文献   
117.
This review presents the state‐of‐the‐art concerning the application of natural and artificial high‐intensity sweeteners, fructans and bulking agents such as polyols as sugar replacers in sweet‐baked goods and their effects on product characteristics. The recent much publicised attention given to weight gain of the population and its consequences on the occurrence of diet‐related diseases in developed countries has influenced the food manufacturers attempts to provide the consumer with reduced energy products. The replacement of sucrose in sweet bakery products by alternative natural or artificial sweeteners can be a challenging issue. Sucrose as a main ingredient in sweet bakery products contributes, aside from providing sweetness, to numerous processing and product characteristics. Intense sweeteners have a high sweetness compared with sucrose but lack in their contribution to the body of the product, whereas the replacement of sucrose with bulking sweeteners may result in products with a similar body but a lack in taste and flavour.  相似文献   
118.
The National Household Survey carried out in 2009 by Brazil??s bureau of the census contains information on a representative sample of 121,708 households. The questionnaire includes items that enable us to identify households that experience moderate and severe degrees of food insecurity. The results of logistic regression analyses support the hypothesis that the odds of food insecurity are higher among female-headed households compared to male-headed households. Net of statistical controls for region, urban residence, age, monthly per capita household income, and five indicators of the internal composition of the household, the odds of moderate and severe food insecurity are, respectively, 32?% and 16?% higher among households headed by women compared to households headed by men. Further analyses show that the likelihood of food insecurity increases with presence of young children 0?C10?years of age and older children 11?C18?years of age. The importance of intra-household characteristics is confirmed by results that show that the odds of both moderate and severe food insecurity increase with additional adult males but decrease with additional adult females. Evidence that the presence of adult females reduces food insecurity is consistent with studies of gender differences in household decision making which show that, compared to men, women??s spending patterns have a greater positive effect on the welfare of children and other members of the household. The conclusions are discussed in the context of the poverty and hunger alleviation initiatives in Brazil??s new social policy agenda.  相似文献   
119.
3 ward climate scales were derived from 2 independent studies linking treatment environments as perceived by patients and staff to treatment outcome as assessed by ward dropout, release, and community tenure rates. Patients and staff from 7 large and 8 small Veterans Administration hospital wards completed the Ward Atmosphere Scales. Patients and staff agreed in perceiving wards with high dropout rates as low in involvement, support, order and organization, and program clarity, whereas wards with high release rates were perceived as strongly emphasizing practical orientation, but as relatively "unexpressive." Wards that kept patients out of the hospital longest were seen as emphasizing autonomy and independence, practical orientation, order and organization, and the open expression of feelings, particularly angry feelings. It is concluded that some relatively consistent findings are emerging from studies in this area. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
120.
Retraction: The following article from the Journal of the Science of Food and Agriculture , ‘Temperature affects flavour intensity and quality of aroma in fresh basil (Ocimum basilicum L.) leaves’ by Xianmin Chang, Peter G Alderson, Tracey A Hollowood, Louise Hewson, and Charles J Wright, published online on 19 October 2005 in Wiley InterScience (www.interscience.wiley.com), has been retracted by agreement between the authors, the journal Editor in Chief, David S. Reid and John Wiley & Sons, Ltd. The retraction has been agreed due to overlap between this article and the following article published in the The Journal of Horticultural Science & Biotechnology ; ‘Effect of temperature integration on the growth and volatile oil content of Basil (Ocimum basilicum L.)’ by Xianmin Chang, Peter G Alderson and Charles J Wright. Volume 80 Issue 5, 2005, pages 593 – 598  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