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   3311篇
  免费   200篇
  国内免费   1篇
电工技术   56篇
综合类   14篇
化学工业   680篇
金属工艺   60篇
机械仪表   66篇
建筑科学   192篇
矿业工程   4篇
能源动力   97篇
轻工业   347篇
水利工程   35篇
石油天然气   23篇
无线电   245篇
一般工业技术   568篇
冶金工业   452篇
原子能技术   22篇
自动化技术   651篇
  2023年   47篇
  2022年   64篇
  2021年   110篇
  2020年   58篇
  2019年   63篇
  2018年   77篇
  2017年   77篇
  2016年   125篇
  2015年   115篇
  2014年   123篇
  2013年   195篇
  2012年   169篇
  2011年   223篇
  2010年   211篇
  2009年   162篇
  2008年   159篇
  2007年   141篇
  2006年   144篇
  2005年   117篇
  2004年   98篇
  2003年   76篇
  2002年   80篇
  2001年   72篇
  2000年   52篇
  1999年   66篇
  1998年   137篇
  1997年   80篇
  1996年   55篇
  1995年   48篇
  1994年   27篇
  1993年   38篇
  1992年   18篇
  1991年   15篇
  1990年   18篇
  1989年   24篇
  1988年   20篇
  1987年   20篇
  1986年   16篇
  1985年   23篇
  1984年   13篇
  1983年   18篇
  1982年   10篇
  1981年   7篇
  1980年   6篇
  1979年   9篇
  1977年   5篇
  1976年   23篇
  1974年   5篇
  1973年   6篇
  1968年   6篇
排序方式: 共有3512条查询结果,搜索用时 250 毫秒
121.
122.
We present a two-dimensional large-aspect-ratio model for the off-contact screen printing of a power-law fluid. We extend the work of White et al. (J Eng Math 54:49–70, 2005) by explicitly including the fluid/air free surface that is present beneath the screen ahead of the squeegee. In the distinguished parameter limit of greatest interest to industry, the process is quasi-steady on the time-scale of a print and can be analysed in three separate regions using the method of matched asymptotic expansions. This allows us to predict where the fluid transfers through the screen, the point at which it first makes contact with the substrate, and the amount of fluid deposited on the substrate during a print stroke. Finally, we show that using a shear-thinning fluid will decrease the amount of fluid transferred ahead of the squeegee, but increase the amount of fluid deposited on the substrate.  相似文献   
123.
124.
125.
126.
In early times, the drug discovery process was mainly based on profiling of new medications in in vivo systems. In the absence of knowledge on enzymatic structures, biochemical signaling or precise cellular processes, researchers were dependent on knowledgeable readout of phenotypic effects in living animals.  相似文献   
127.
128.
Selecting an optimal return policy requires taking into account two effects: the potential positive effect on sales and the potential negative effect of higher costs. We propose a two-step model, in which we first utilize a robust regression to explain purchase behavior, and then apply a zero-inflated negative binominal regression to model the return behavior. We apply this model to data from the most important online platform in China and obtain three main findings. First, the adoption of return policies results in increased sales, while reputation works as a moderator in this process. Second, good reputation and traditional customer friendly return policies (like the Seven-Day Return policy) can significantly increase the number of returns, while more guarantee credibility (enhanced by Guarantee Money) is related to fewer returns. Taken together, both the Seven-Day Return policy (profit increase of +0.29 %) and Guarantee Money (profit increase of +0.016 % per Yuan guarantee) ultimately increase firms’ profit.  相似文献   
129.

Object   

Histology is the gold standard for confirming thermally induced necrosis. Generally, however, no specimen is obtained from thermal ablation therapy for pathological examination. The aim of this study was to provide evidence for the relationship between temperatures reached and resulting tissue coagulation during laser ablation in a near-physiological ex vivo lung tumor model by combining viability staining and direct temperature measurement.  相似文献   
130.
The influence of anthropogenic processes on global material flow systems increasingly dominates the influence of natural processes. In this context, the provision of detailed knowledge on material flow systems is relevant for decision makers in resource policy. This information can be provided in the form of one-year material balances or, if repeated over a period of consecutive years, in the form of national resource budgets. In national resource budgets, all relevant flows of a material through a national economy are balanced and displayed in neatly arranged diagrams. By updating these material balances over a series of years, the development of material stocks can be estimated. Upcoming challenges both regarding supply and disposal of materials can be identified. Comprehensive balances are useful for decision makers in resource policy and, moreover, as an information basis for future exploitation of anthropogenic resources. However, both availability of data and possibilities for assessing the reliability of data are very limited. In this work, a methodology for investigating and evaluating the information basis of national resource budgets is presented. The methodology includes procedures for systematic characterization of resource budget data and formal procedures for evaluating their reliability. From a scientific perspective, the methodology contributes to understanding material flow systems better. It also enables implementing procedures towards national resource budgets in an administrative context.  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