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   785篇
  免费   42篇
  国内免费   2篇
电工技术   7篇
化学工业   223篇
金属工艺   9篇
机械仪表   10篇
建筑科学   66篇
矿业工程   2篇
能源动力   14篇
轻工业   147篇
水利工程   12篇
石油天然气   2篇
无线电   65篇
一般工业技术   110篇
冶金工业   61篇
原子能技术   2篇
自动化技术   99篇
  2024年   2篇
  2023年   13篇
  2022年   43篇
  2021年   48篇
  2020年   22篇
  2019年   28篇
  2018年   25篇
  2017年   19篇
  2016年   23篇
  2015年   24篇
  2014年   34篇
  2013年   68篇
  2012年   42篇
  2011年   71篇
  2010年   49篇
  2009年   51篇
  2008年   36篇
  2007年   40篇
  2006年   31篇
  2005年   22篇
  2004年   18篇
  2003年   20篇
  2002年   13篇
  2001年   15篇
  2000年   9篇
  1999年   7篇
  1998年   6篇
  1997年   10篇
  1996年   10篇
  1995年   4篇
  1994年   2篇
  1993年   5篇
  1992年   7篇
  1991年   1篇
  1989年   3篇
  1987年   1篇
  1981年   1篇
  1957年   1篇
  1926年   1篇
  1924年   2篇
  1922年   2篇
排序方式: 共有829条查询结果,搜索用时 10 毫秒
151.
A catalyst of Ni supported on alumina coated monolith has been prepared, characterized and tested in NH3 decomposition. The characterization of the catalyst by XPS and TPR showed that there is no formation of aluminates after catalyst use. It is studied the effect of the space velocity, by varying the feed flow rate and the catalyst??s length. Some evidences are shown about the reaction inhibition by produced H2 and about the reasons for the better performance of the monolith than packed bed catalyst.  相似文献   
152.
The temperature–composition phase diagram in the diluted region of the cationic surfactant cetyldimethylbenzylammonium salicylate/water system was studied with a battery of techniques. The Krafft temperature (T k = 33 ± 1 °C) was measured by differential scanning calorimetry, polarizing microscopy, conductimetry, viscosimetry, and rheometry. The critical vesicle concentration (cvc, ~0.002 wt%) and a vesicle–micellar transition (cvm, ~0.005 wt%) was detected at a temperature of 35 °C. Below T k and concentrations ≤2 wt%, a transparent solution is formed (I). Above 2–8.5 wt%, a lamellar (L1) phase forms. At higher concentrations and up to 12 wt%, a second lamellar phase (L2) is detected. From 12.4 to 15.5 wt%, an emulsion phase (E) is formed. Rheological dynamic measurements for the I phase indicate that the system exhibits a predominantly viscous behavior (G′ < G″) for concentrations lower than the overlap or entanglement concentration (C e, ~0.75 wt%). At higher concentrations, wormlike micelles form and the elastic behavior predominates (G′ > G″). The elastic (G′) modulus collapses in a concentration–time master curve in the whole reduced frequencies range ωτ c examined, whereas the viscous modulus (G″) collapses only at reduced frequencies lower than 0.1. Reduced stress plotted as a function of the reduced shear rate yields a good superposition of the curves at the different concentrations up to the onset of the non-linear behavior.  相似文献   
153.
AFPA culture medium, which is used for recognition of Aspergillus flavus and A. parasiticus, has been validated in a collaborative study including nine laboratories located in Australia, Brazil, Denmark, The Netherlands, Sweden and United Kingdom. Three freeze-dried fungal mixtures, containing A. flavus/A. parasiticus and background fungi, were produced and checked for homogeneity. The coefficients of variance were low, ranging from 0.81% to 1.09% for total fungal counts and between 2.50% and 2.72% for counts of A. flavus/A. parasiticus. The laboratories analysed the contents of two vials of each mixture on commercial A. flavus and A. parasiticus agar (AFPA), in-house-made AFPA, and on a standard media, dichloran 18% glycerol agar (DG18). Reproducibility values for counts of A. flavus/A. parasiticus indicated no differences between the commercial AFPA and the in-house-made AFPA. Variation between laboratories was low, indicating that the medium was effective in use. Reproducibility values for DG18 were higher. There were no differences in counts of A. flavus/A. parasiticus on AFPA and DG18. However, DG18 gave slightly higher total fungal counts compared to AFPA.  相似文献   
154.
Specific interactions that depend on the nature of electrolytes are observed when proteins and other molecules are studied by potentiometric, spectroscopic and theoretical methods at high salt concentrations. More recently, it became clear that such interactions may also be observed in solutions that can be described by the Debye-Hückel theory, i.e., at physiological (0.1 mol dm−3) and lower concentrations. We carried out molecular dynamics simulations of bovine serum albumin in physiological solutions at T=300 and 350 K. Analysis of the simulations revealed some differences between LiCl solutions and those of NaCl and KCl. The binding of Li+ ions to the protein was associated with a negative free energy of interaction whereas much fewer Na+ and K+ ions were associated with the protein surface. Interestingly, unlike other proteins BSA does not show a preference to Na+ over K+. Quantum chemical calculations identified a significant contribution from polarisation to the hydration of Li+ and (to a lesser degree) Na+, which may indicate that polarisable force-fields will provide more accurate results for such systems.  相似文献   
155.
156.
157.
Seasonal periods of high rainfall have been shown to cause elevated natural organic matter (NOM) loadings at treatment works. These high levels lead to difficulties in removing sufficient NOM to meet trihalomethane standards, and hence better alternative treatments are required. Here the removal of NOM was investigated by conventional coagulation treatment using both bulk and fractionated NOM. Initial experiments showed that over 70% removal of the hydrophobic and hydrophilic acid fractions was achieved at the works, while only 16% of the hydrophilic nonacid fraction was being removed. Bench scale jar testing of the isolated NOM fractions demonstrated that high removals of the hydrophobic fractions were achieved and that optimized conditions increased removal of the hydrophilic fractions, indicating that staged coagulation could be of benefit in the removal of the recalcitrant fractions. Experiments using optimized staged coagulation indicated that a small increase in the removal of the total NOM of this water was possible when compared to conventional treatment.  相似文献   
158.
In this study, the oxidation behavior of FeCoCrNiMn (HEA + Mn) is compared to three modified HEAs manufactured by substituting Mn with Al, Cu, or Al + Cu. Oxidation tests were conducted between 600°C and 800°C for up to 500 h in synthetic air. Substitution of Mn leads to a significant improvement in the oxidation resistance for the three modified HEAs. For FeCoCrNiCu (HEA + Cu), a local attack of a Cu-rich phase was observed, leading to the formation of CuO blisters on the surface. The FeCoCrNiAl (HEA + Al) alloy was characterized by the formation of a thin Al2O3 surface layer for all temperatures. However, for the HEA + Al alloy the formation of AlN was observed after 300 h at 800°C, leading to a partial breakdown of the protective scale. FeCoCrNiCuAl (HEA + Cu + Al) by far showed the best oxidation resistance, characterized by the formation of a highly protective Al2O3 scale that effectively inhibited nitrogen penetration into the metal subsurface and local attack of the Cu-rich phase.  相似文献   
159.
160.

Smart homes are becoming increasingly popular in providing people with the services they desire. Activity recognition is a fundamental task to provide personalised home facilities. Many promising approaches are being used for activity recognition; one of them is data-driven. It has some fascinating features and advantages. However, there are drawbacks such as the lack of ability to providing home automation from the day one due to the limited data available. In this paper, we propose an approach, called READY (useR-guided nEw smart home ADaptation sYstem) for developing a personalised automation system that provides the user with smart home services the moment they move into their new house. The system development process was strongly user-centred, involving users in every step of the system’s design. Later, the user-guided transfer learning approach was introduced that uses an old smart home data set to enhance the existing smart home service with user contributions. Finally, the proposed approach and designed system were tested and validated in the smart lab that showed promising results.

  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