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   3769篇
  免费   51篇
电工技术   30篇
综合类   4篇
化学工业   232篇
金属工艺   24篇
机械仪表   24篇
建筑科学   26篇
能源动力   33篇
轻工业   75篇
水利工程   5篇
石油天然气   3篇
无线电   126篇
一般工业技术   232篇
冶金工业   2826篇
原子能技术   15篇
自动化技术   165篇
  2021年   13篇
  2020年   9篇
  2019年   18篇
  2018年   15篇
  2017年   23篇
  2016年   26篇
  2015年   13篇
  2014年   33篇
  2013年   39篇
  2012年   24篇
  2011年   55篇
  2010年   39篇
  2009年   29篇
  2008年   38篇
  2007年   53篇
  2006年   36篇
  2005年   46篇
  2004年   27篇
  2003年   28篇
  2002年   20篇
  2001年   24篇
  2000年   23篇
  1999年   104篇
  1998年   891篇
  1997年   489篇
  1996年   349篇
  1995年   200篇
  1994年   162篇
  1993年   177篇
  1992年   31篇
  1991年   42篇
  1990年   41篇
  1989年   54篇
  1988年   54篇
  1987年   49篇
  1986年   50篇
  1985年   41篇
  1984年   11篇
  1983年   26篇
  1982年   15篇
  1981年   36篇
  1980年   29篇
  1979年   13篇
  1978年   31篇
  1977年   61篇
  1976年   141篇
  1975年   18篇
  1974年   18篇
  1970年   9篇
  1969年   9篇
排序方式: 共有3820条查询结果,搜索用时 15 毫秒
41.
42.
Summary ESCA is used to characterize ion beam irradiated P(p-ClPhMA)-samples. The results show a chlorine abstraction. The experimental findings are in accordance with a recently proposed model for a crosslinking mechanism of halogenated aromatic polymers.  相似文献   
43.
44.
The extent of the dominant singular field is investigated for a finite crack under stress wave loading. Using a boundary integral equation method the complete solution as well as the near field solution is determined. A comparison of the two fields indicates that the singular field dominates within a small domain at the crack tip. The size of the dominance region in the dynamic case may be very different from that in the static case.  相似文献   
45.
Interleukin (IL)-1 alpha and beta are cytokines which can mediate inflammatory, bone resorbing, and reparative effects in the periodontium, but few longitudinal data exist exploring their role following periodontal therapy. This study examined gingival crevicular fluid (GCF) concentrations of IL-1 alpha and IL-1 beta at sites with shallow sulci (SS) or inflamed moderate/advanced pockets (M/AP) before and 6 months after treatment with closed scaling/root planing (SC/RP) or papillary flap debridement (PFD), all in the same subject (n = 14 patients). No significant differences were noted in IL-1 alpha or beta concentrations (determined with two-site enzyme-linked immunosorbent assays) between SS and M/AP sites at baseline. While both therapies improved clinical parameters of periodontal disease, IL-1 alpha concentration increased significantly (p < 0.05) in M/AP-PFD sites 6 months after treatment, but were unchanged in other groups. IL-1 beta concentrations were numerically lower after therapy, except for a significant increase (p < 0.05) in M/AP-PFD sites. These data suggest that surgical wound healing in an inflamed, plaque-infected site (M/AP-PFD) results in prolonged production of IL-1, which may be a reflection of the extent of tissue trauma and delayed wound healing. In spite of increased IL-1 levels, these sites demonstrated significant short-term improvement in clinical attachment level (+ 1.8 mm, p < or = 0.001) postoperatively.  相似文献   
46.
47.
The measured plastic deformation of Mg-PSZ under stress contains contributions from both transformation and microcracking. A method is described to separate the contributions from transformation and microcracking for samples deformed in uniaxial tension. Such a separation enables the ratio of the longitudinal to transverse strains arising from the transformation to be estimated. The results are compared to the predictions of the shear–dilatation model of Chen and Reyes-Morel. Serious discrepancies are found between the experimental results and the predictions of the model and the possible reason for this is discussed.  相似文献   
48.
49.
The Subjective Stress Scale (SSS; Bramston & Bostock, 1994) was developed to measure stress in people with a mild intellectual disability. In previous research, the SSS was found to measure two broad dimensions of stress (a) a General Worry factor and (b) a factor that tapped concerns about Negative Interpersonal Relations (Bramston & Fogarty, 1995). The present study sought to continue this line of research by introducing a slightly modified form of the SSS, to be known as the Lifestress Inventory (LI) and examining the psychometric properties of the scale when administered to a new sample of 221 people with mild intellectual disabilities. Confirmatory factor analysis indicated that three underlying factors corresponding to General Worry, Negative Interpersonal Relations, and Coping were sufficient to account for the correlations among the items in the LI. Rasch analysis indicated some improvements to the scoring format for the LI and also showed that the most easily experienced stressors were associated with the Negative Interpersonal Relations dimension. The refinements introduced by the LI and the further demonstration that some of the broad stress dimensions identified in the general population can also be found in people with an intellectual disability represent important milestones for researchers interested in exploring reactions to stress among this population.  相似文献   
50.
A controlled study evaluating the effectiveness of exposure plus response-prevention treatment of bulimia nervosa was conducted in a sample of 47 women. This was a four-group comparison involving three treatment conditions and a waiting-list control group. The three treatment conditions were (a) exposure plus response prevention conducted in a single setting (clinic), (b) exposure plus response prevention conducted in multiple settings (clinic, patients' homes, and restaurants), and (c) cognitive–behavioral therapy without exposure plus response prevention. All treatment was provided to groups of 3 patients at a time. Outcome was evaluated at posttreatment and at a 6-month follow-up. The three treatment groups improved significantly on most outcome measures, whereas the waiting-list control group showed little change. At follow-up, there was a slightly better outcome on vomiting behavior and amount of food consumed in one of the test meals for the exposure plus response-prevention groups relative to the no-exposure group. However, on all other measures, the degree of improvement from pretreatment to follow-up was the same for all three treatment groups. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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