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   6352篇
  免费   315篇
  国内免费   9篇
电工技术   49篇
综合类   7篇
化学工业   1400篇
金属工艺   101篇
机械仪表   120篇
建筑科学   242篇
矿业工程   17篇
能源动力   108篇
轻工业   744篇
水利工程   49篇
石油天然气   12篇
无线电   390篇
一般工业技术   1019篇
冶金工业   1627篇
原子能技术   33篇
自动化技术   758篇
  2023年   46篇
  2022年   79篇
  2021年   162篇
  2020年   111篇
  2019年   90篇
  2018年   197篇
  2017年   182篇
  2016年   193篇
  2015年   164篇
  2014年   176篇
  2013年   409篇
  2012年   344篇
  2011年   373篇
  2010年   277篇
  2009年   241篇
  2008年   300篇
  2007年   239篇
  2006年   224篇
  2005年   171篇
  2004年   144篇
  2003年   141篇
  2002年   107篇
  2001年   91篇
  2000年   103篇
  1999年   95篇
  1998年   525篇
  1997年   301篇
  1996年   198篇
  1995年   118篇
  1994年   117篇
  1993年   110篇
  1992年   28篇
  1991年   38篇
  1990年   25篇
  1989年   45篇
  1988年   32篇
  1987年   26篇
  1986年   20篇
  1985年   37篇
  1984年   23篇
  1983年   22篇
  1982年   37篇
  1981年   40篇
  1980年   27篇
  1979年   18篇
  1978年   23篇
  1977年   43篇
  1976年   45篇
  1975年   19篇
  1973年   14篇
排序方式: 共有6676条查询结果,搜索用时 203 毫秒
21.
22.
23.
24.
25.
Microcapsules are used for the formulation of drug controlled release and drug targeting dosage forms. Encapsulated hydrophobic drugs are often applied as their solutions in plant oils. The uptake of the oils in the complex coacervate microcapsules can be improved by the addition of surfactants. In this study, soybean, olive and peanut oils were chosen as the representatives of plant oils. The well characterized complex coacervation of gelatin and acacia has been used to produce the microcapsules. The amount of encapsulated oil has been determined gravimetrically. The encapsulation of the oils was high (75-80%). When the surfactants with HLB values from 1.8 to 6.7 were used, the amount of encapsulated oil was high (65-85%). A significant decrease of the oil content in the microcapsules was found when Tween 61 with HLB = 9.6 had been added into the mixture. No oil was found inside the microcapsules from the coacervate emulsion mixture containing Tween 81 (HLB = 10) and Tween 80 (HLB = 15), respectively. The results of the experiment confirm the dependence of hydrophobic substance encapsulation on the HLB published recently for Squalan.  相似文献   
26.
This paper highlights the possibility of inverse gas chromatography for the surface characterization of common fillers (CaCO3, talc, SiO2,) for paints and coatings. Divided solids are described, on the one hand, by the dispersive component of their surface energy and, on the other, by a specific parameter indicating their acid-base interaction potential. The role of the surface morphology at a molecular level is also examined. It is demonstrated that steric effects play an important role in the adsorption of probes on lamellar solids like talc. The consequences of surface treatments as well as examples of practical applications are also reported.  相似文献   
27.
Reviews the book, Psychologie de la famille by Monique V. G. Morval (1985). Morval presents a book with two views: the first looks at the axis of the family in light of systemic approaches and the second centers on the cycle of family life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
28.
A method is presented for computing the values of apparent diffusivity in solids with respect to the concentration of the diffusing substance (water or sodium chloride). This method does not require any assumption upon the mathematical relationship between diffusivity and concentration. It can be applied to experimental measurements of local concentration versus position within the solid (profiles) with relatively few measurements (circa 10) and a mathematical smoothing of the experimental data by using an artificial neural network model. The method was first validated on simulated data obtained by using a constant diffusivity value and on experimental profiles when the relation between diffusivity and concentration was given. It was then applied to original experimental moisture profiles obtained by putting gelatin gels with different initial moisture contents into contact for up to 14 days. The method was also successfully applied to five sets of experimental moisture and sodium chloride profiles taken from the literature and obtained from different food products. Apparent diffusivities calculated by our method were found in agreement with those obtained by authors using different numerical methods to compute the diffusivity values.  相似文献   
29.
Hybrid Approach for Addressing Uncertainty in Risk Assessments   总被引:3,自引:0,他引:3  
Parameter uncertainty is a major aspect of the model-based estimation of the risk of human exposure to pollutants. The Monte Carlo method, which applies probability theory to address model parameter uncertainty, relies on a statistical representation of available information. In recent years, other uncertainty theories have been proposed as alternative approaches to address model parameter uncertainty in situations where available information is insufficient to identify statistically representative probability distributions, due in particular to data scarcity. The simplest such theory is possibility theory, which uses so-called fuzzy numbers to represent model parameter uncertainty. In practice, it may occur that certain model parameters can be reasonably represented by probability distributions, because there are sufficient data available to substantiate such distributions by statistical analysis, while others are better represented by fuzzy numbers (due to data scarcity). The question then arises as to how these two modes of representation of model parameter uncertainty can be combined for the purpose of estimating the risk of exposure. This paper proposes an approach (termed a hybrid approach) which combines Monte Carlo random sampling of probability distribution functions with fuzzy calculus. The approach is applied to a real case of estimation of human exposure, via vegetable consumption, to cadmium present in the surficial soils of an industrial site located in the north of France. The application illustrates the potential of the proposed approach, which allows the uncertainty affecting model parameters to be represented in a way that is consistent with the information at hand. Also, because the hybrid approach takes advantage of the “rich” information provided by probability distributions, while retaining the conservative character of fuzzy calculus, it is believed to hold value in terms of a “reasonable” application of the precautionary principle.  相似文献   
30.
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