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   2429篇
  免费   38篇
  国内免费   1篇
电工技术   9篇
综合类   4篇
化学工业   143篇
金属工艺   19篇
机械仪表   14篇
建筑科学   44篇
矿业工程   2篇
能源动力   27篇
轻工业   126篇
水利工程   15篇
石油天然气   33篇
无线电   101篇
一般工业技术   174篇
冶金工业   1603篇
原子能技术   13篇
自动化技术   141篇
  2019年   13篇
  2018年   15篇
  2017年   13篇
  2016年   13篇
  2015年   15篇
  2014年   26篇
  2013年   66篇
  2012年   17篇
  2011年   27篇
  2010年   39篇
  2009年   32篇
  2008年   45篇
  2007年   34篇
  2006年   56篇
  2005年   26篇
  2004年   33篇
  2003年   37篇
  2002年   35篇
  2001年   27篇
  2000年   20篇
  1999年   69篇
  1998年   476篇
  1997年   264篇
  1996年   175篇
  1995年   115篇
  1994年   90篇
  1993年   108篇
  1992年   47篇
  1991年   50篇
  1990年   34篇
  1989年   41篇
  1988年   23篇
  1987年   32篇
  1986年   27篇
  1985年   28篇
  1984年   8篇
  1983年   18篇
  1982年   13篇
  1981年   17篇
  1980年   9篇
  1979年   9篇
  1978年   13篇
  1977年   37篇
  1976年   67篇
  1975年   13篇
  1974年   7篇
  1973年   9篇
  1972年   9篇
  1970年   7篇
  1969年   7篇
排序方式: 共有2468条查询结果,搜索用时 15 毫秒
71.
72.
It is not generally appreciated that pseudoxanthoma elasticum (PXE) can be associated with epidermal perforation by elastic fibers. We report an example of this phenomenon. The term "perforating PXE" is suggested and a distinction is made from elastosis perforans serpiginosa (EPS). We believe that most reported cases of coexistence of PXE and EPS are perforating PXE and that the coexistence of EPS has not been clearly demonstrated.  相似文献   
73.
Emotional support is known to provide psychosocial benefits for women with breast cancer, but women can experience a mismatch between support that is wanted and support that is received from their personal supporter. The role of wanted and unwanted support in psychosocial adjustment was examined in 79 women recovering from breast cancer. Four distinct patterns of desired support actions were found using cluster analysis. Patterns of wanted support were not related to better or worse psychosocial adjustment. However, a misalignment of support between the provider and the receiver significantly influenced psychosocial adjustment, and unwanted but received support (support commission) was uniquely associated with poor psychosocial adjustment. Clinical interventions using the support instrument could help match support providers' actions to receivers' preferences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
74.
The authors examined the validity of D. R. Lynam and T. A. Widiger's (2001) prototypes for personality disorders (PDs) derived from the facets of the 5-factor model (FFM) of personality in 2 clinical samples. In the 1st sample (N = 94), there was good agreement between the prototypes generated by experts and the profiles reported by patients. These FFM PD similarity scores also demonstrated good convergent and discriminant validity with results from a semistructured interview and a self-report measure of Axis II pathology. In the 2nd sample (N = 132), the FFM PD similarity scores demonstrated excellent longitudinal stability and good predictive validity with regard to consensus ratings of PD features. The implications of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
75.
76.
77.
The synergistic effect on the thermal decomposition and heat release rate (HRR) in particular the peak heat release rate (PHRR) of unsaturated polyester (UP) resin blended with multiwalled carbon nanotubes (MWNTs) and sepiolite nanoclay was investigated using thermal gravimetric analysis (TGA), pyrolysis combustion flow calorimetery (PCFC) and the cone calorimetery. Initial microcalorimeter findings established a synergistic effect for ternary system comprising a 10:0.5 wt% mixture of sepiolite:MWNT, respectively, which resulted in a 40% reduction in heat release capacity (HRC). This result was also confirmed within the well‐established cone calorimeter by a 50% reduction in PHRR in contrast to unfilled UP. The mechanism behind this reduction is thought to be due to the bridging of the MWNTs between the sepiolite clay needles, creating a tight protective surface layer that reduces the MLR. TGA also confirmed the advantage of such a ternary system through a 36°C shift in the onset decomposition temperature and an 11% increase in residual char. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
78.
79.
Uranium bearing ores are often a complex mixture of minerals and compounds, a number of which are not of economic importance and are commonly referred to as gangue materials. In order to improve the efficiency of the dissolution stage of the overall uranium extraction process, a greater understanding of the minerals and compounds present in the ore is required. A greater knowledge of the gangue materials present is important as they can influence various aspects of the dissolution process such as providing potential adsorption sites for aqueous uranium species and through influencing the equilibrium of reactions involving aqueous uranium species. In this study the mineralogy of a uranium ore was investigated using a range of X-ray diffraction (XRD) based methods including in situ high temperature XRD and XRD using a synchrotron beam line. The results obtained from standard XRD (Cu Kα), high temperature XRD and synchrotron XRD (16.534 keV) were compared and a number of minerals were identified. The improved spatial resolution and intensity of the synchrotron data allowed for superior phase identification of a variety of minerals where standard X-ray techniques gave inconclusive results.  相似文献   
80.
Implementation of a Monte Carlo simulation for the solution of population balance equations (PBEs) requires choice of initial sample number (N0), number of replicates (M), and number of bins for probability distribution reconstruction (n). It is found that Squared Hellinger Distance, H2, is a useful measurement of the accuracy of Monte Carlo (MC) simulation, and can be related directly to N0, M, and n. Asymptotic approximations of H2 are deduced and tested for both one‐dimensional (1‐D) and 2‐D PBEs with coalescence. The central processing unit (CPU) cost, C, is found in a power‐law relationship, , with the CPU cost index, b, indicating the weighting of N0 in the total CPU cost. n must be chosen to balance accuracy and resolution. For fixed n, M × N0 determines the accuracy of MC prediction; if b > 1, then the optimal solution strategy uses multiple replications and small sample size. Conversely, if 0 < b < 1, one replicate and a large initial sample size is preferred. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2394–2402, 2015  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