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   1709篇
  免费   50篇
  国内免费   2篇
电工技术   8篇
化学工业   302篇
金属工艺   16篇
机械仪表   12篇
建筑科学   87篇
矿业工程   3篇
能源动力   24篇
轻工业   172篇
水利工程   10篇
石油天然气   2篇
无线电   83篇
一般工业技术   196篇
冶金工业   662篇
原子能技术   5篇
自动化技术   179篇
  2022年   28篇
  2021年   54篇
  2020年   25篇
  2019年   28篇
  2018年   25篇
  2017年   20篇
  2016年   24篇
  2015年   24篇
  2014年   44篇
  2013年   100篇
  2012年   71篇
  2011年   63篇
  2010年   60篇
  2009年   54篇
  2008年   73篇
  2007年   57篇
  2006年   55篇
  2005年   49篇
  2004年   48篇
  2003年   20篇
  2002年   52篇
  2001年   40篇
  2000年   35篇
  1999年   36篇
  1998年   22篇
  1997年   22篇
  1996年   31篇
  1995年   28篇
  1994年   36篇
  1993年   42篇
  1992年   40篇
  1991年   11篇
  1990年   37篇
  1989年   34篇
  1988年   33篇
  1987年   31篇
  1986年   23篇
  1985年   31篇
  1984年   32篇
  1983年   21篇
  1982年   15篇
  1981年   16篇
  1980年   15篇
  1979年   26篇
  1978年   16篇
  1977年   11篇
  1976年   14篇
  1975年   19篇
  1973年   9篇
  1972年   12篇
排序方式: 共有1761条查询结果,搜索用时 15 毫秒
91.
92.
Attempted to replicate earlier findings by B. Pope and A. W. Siegman (see PA, Vol. 39:13386, and Vol. 40:509) that there is an inverse relationship between interviewer specificity and both interviewee productivity and uncertainty, through the use of more naturalistic interviewers. 24 18-40 yr. old psychiatric inpatients were interviewed 3 times in a low specificity, high specificity, and an uncontrolled interview. Previous findings were supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
93.
Reports for 1982 are listed for the following regional association meetings: Sixty-Second Annual Meeting of the Western Psychological Association; Fifty-Second Annual Meeting of the Rocky Mountain Psychological Association; Fifty-Fourth Annual Meeting of the Midwestern Psychological Association; Twenty-Eighth Annual Meeting of the Southeastern Psychological Association; Twenty-Eighth Annual Meeting of the Southwestern Psychological Association; Twenty-Second Annual Meeting of the New England Psychological Association; Fifty-Third Annual Meeting of the Eastern Psychological Association; and Seventy-Fourth Annual Meeting of the Southern Society for Philosophy and Psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
94.
Growth and metabolism of selected strains of probiotic bacteria in milk   总被引:1,自引:0,他引:1  
Growth and metabolism of five probiotic strains with well-documented health effects were studied in ultra-high temperature (UHT) treated milk, supplemented with 0.5% (w/v) tryptone or 0.75% (w/v) fructose. The probiotic strains were Lactobacillus acidophilus La5, Lb. acidophilus 1748, Lactobacillus rhamnosus GG, Lactobacillus reuteri SD 2112 and Bifidobacterium animalis BB12. Fermentation was followed for 72 h at 37 degrees C and the samples were analysed for pH, log cfu ml(-1), volatile compounds, organic acids and carbon dioxide. The strains reduced pH from 6.7 to between 3.9 and 4.4 after 24 h of incubation. All strains attained viable cell counts above 8.7-9.18 log cfu ml(-1) after 6-16 h of incubation. The two Lb. acidophilus strains showed a stable level of viable cells during 12-72 h of incubation but the three other strains showed a reduction of 0.4-1.1 log cfu ml(-1) from 24 to 72 h of incubation. However, all strains showed cell levels between 7.8 and 8.7 log cfu ml(-1) after 72 h of incubation. After 48 h of incubation, the amount of lactic acid produced varied according to strain from 6949 to 14,000 mg kg(-1) and acetic acid produced varied from 0 to 6901 mg kg(-1). Three of the strains metabolised citrate but only low amounts of diacetyl and acetoin were detected within strains, 0.2-0.8 and 6.5-10 mg kg(-1), respectively. Carbon dioxide produced varied from 221 to 3942 mg kg(-1) and was connected to the citrate-fermenting ability of the strain used and their carbohydrate fermentation pathway. Three of the strains produced detectable levels of acetaldehyde and the concentration varied from 9.4 to 12.6 mg kg(-1) after 24 h of incubation. All five probiotic strains showed very different profiles of metabolites during fermentation; however, the two Lb. acidophilus strains were the most alike. Our findings show the importance of controlling the fermentation time since the probiotic strains produced different amounts of metabolic products according to fermentation time.  相似文献   
95.
To solve today’s ecological problems, scientists need well documented, validated, and coherent data archives. Historically, however, ecologists have collected and stored data idiosyncratically, making data integration even among close collaborators difficult. Further, effective ecology data warehouses and subsequent data mining require that individual databases be accurately described with metadata against which the data themselves have been validated. Using database technology would make documenting data sets for archiving, integration, and data mining easier, but few ecologists have expertise to use database technology and they cannot afford to hire programmers. In this paper, we identify the benefits that would accrue from ecologists’ use of modern information technology and the obstacles that prevent that use. We describe our prototype, the Canopy DataBank, through which we aim to enable individual ecologists in the forest canopy research community to be their own database programmers. The key feature that makes this possible is domain-specific database components, which we call templates. We also show how additional tools that reuse these components, such as for visualization, could provide gains in productivity and motivate the use of new technology. Finally, we suggest ways in which communities might share database components and how components might be used to foster easier data integration to solve new ecological problems.  相似文献   
96.
Community computing has recently grown to become a major research area in human–computer interaction. One of the objectives of community computing is to support computer supported cooperative work among distributed collaborators working toward shared professional goals in online communities of practice. A core issue in designing and developing community computing infrastructures – the underlying socio-technical layer that supports communitarian activities – is sustainability. Many community computing initiatives fail because the underlying infrastructure does not meet end user requirements; the community is unable to maintain a critical mass of users consistently over time; it generates insufficient social capital to support significant contributions by members of the community; or, as typically happens with funded initiatives, financial and human capital resource become unavailable to further maintain the infrastructure. Based on more than nine years of design experience with Tapped In – an online community of practice for education professionals – we present a case study that discusses four design interventions that have sustained the Tapped In infrastructure and its community to date. These interventions represent broader design strategies for developing online environments for professional communities of practice.  相似文献   
97.
Alcohol dependent smokers (N=118) enrolled in an intensive outpatient substance abuse treatment program were randomized to a concurrent brief or intensive smoking cessation intervention. Brief treatment consisted of a 15-min counseling session with 5 min of follow-up. Intensive intervention consisted of three 1-hr counseling sessions plus 8 weeks of nicotine patch therapy. The cigarette abstinence rate, verified by breath carbon monoxide, was significantly higher for the intensive treatment group (27.5%) versus the rate for the brief treatment group (6.6%) at 1 month after the quit date but not at 6 months, when abstinence rates fell to 9.1% for the intensive treatment group and 2.1% for the brief treatment group. Smoking treatment assignment did not significantly impact alcohol outcomes. Although intensive smoking treatment was associated with higher rates of short-term tobacco abstinence, other, perhaps more intensive, smoking interventions are needed to produce lasting smoking cessation in alcohol dependent smokers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
98.
99.
Psychological, biological, social, and physical environmental variables were examined for their association with physical activity of young people. A national sample of 1,504 parents and children in Grades 4–12 were interviewed by telephone. Twenty-two potential determinants were assessed along with an 11-item child physical activity index (α?=?.76). Hierarchical multiple regressions were conducted separately for 6 age–sex subgroups. Percentage of variance explained ranged from 18% for boys in Grades 4–6 to 59% for girls in Grades 10–12. Three variables had strong and consistent associations with the child physical activity index that generalized across subgroups: use of afternoon time for sports and physical activity, enjoyment of physical education, and family support for physical activity. These 3 variables should be targeted for change to promote physical activity in all groups of young people. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
100.
A pronounced degree of vertical imbalance in Australian fiscal federalism has placed increasing financial pressures on lower levels of government, including local government. This has led local government to seek additional ways of financing infrastructure development through developer charges. Due to the lower priority the Australian Bureau of Statistics has accorded local government statistics in recent years, it has been difficult to gauge the extent of use of developer charges as a revenue source. This paper attempts to review the evolution of developer contributions policy and describe the increasing importance of these charges in Australian local government, with special emphasis on New South Wales.  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