全文获取类型
收费全文 | 2241篇 |
免费 | 77篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 30篇 |
综合类 | 6篇 |
化学工业 | 493篇 |
金属工艺 | 57篇 |
机械仪表 | 26篇 |
建筑科学 | 118篇 |
矿业工程 | 10篇 |
能源动力 | 96篇 |
轻工业 | 136篇 |
水利工程 | 6篇 |
石油天然气 | 15篇 |
无线电 | 158篇 |
一般工业技术 | 340篇 |
冶金工业 | 479篇 |
原子能技术 | 24篇 |
自动化技术 | 336篇 |
出版年
2022年 | 23篇 |
2021年 | 38篇 |
2020年 | 25篇 |
2019年 | 25篇 |
2018年 | 33篇 |
2017年 | 35篇 |
2016年 | 32篇 |
2015年 | 34篇 |
2014年 | 48篇 |
2013年 | 220篇 |
2012年 | 72篇 |
2011年 | 82篇 |
2010年 | 90篇 |
2009年 | 84篇 |
2008年 | 94篇 |
2007年 | 76篇 |
2006年 | 57篇 |
2005年 | 63篇 |
2004年 | 50篇 |
2003年 | 47篇 |
2002年 | 41篇 |
2001年 | 36篇 |
2000年 | 20篇 |
1999年 | 35篇 |
1998年 | 74篇 |
1997年 | 49篇 |
1996年 | 49篇 |
1995年 | 51篇 |
1994年 | 42篇 |
1993年 | 44篇 |
1992年 | 30篇 |
1991年 | 28篇 |
1990年 | 37篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 27篇 |
1986年 | 33篇 |
1985年 | 22篇 |
1984年 | 32篇 |
1983年 | 27篇 |
1982年 | 29篇 |
1981年 | 33篇 |
1980年 | 20篇 |
1979年 | 20篇 |
1978年 | 19篇 |
1977年 | 23篇 |
1976年 | 18篇 |
1975年 | 31篇 |
1974年 | 19篇 |
1973年 | 17篇 |
排序方式: 共有2330条查询结果,搜索用时 15 毫秒
91.
The equations that govern the various transport phenomena occurring in a polymer electrolyte membrane fuel cell (PEMFC) were formulated and implemented in a commercial finite element software, in order to predict the fuel cell current density with respect to the operating conditions. The numerical model showed polarization curves in accordance with literature. The catalyst utilization was then improved by optimizing the platinum distribution (design variable) in the fuel cell, so as to maximize current density (objective function) for a fixed total amount of platinum (constraint). The first analysis showed that, for equal anode and cathode catalyst layer thicknesses, maximal current density was achieved by placing more catalyst in the cathode than in the anode. The second analysis showed that, for equal anode and cathode catalyst layer density, maximal current density was achieved by using a catalyst layer that is thicker on the cathode side than that on the anode side. Finally, a topological optimization of the platinum density within the cathode catalyst layer was performed with a gradient based algorithm, and the results showed that at a high stoichiometric ratio, the best design has most of its platinum placed where the reaction rate is the highest, i.e., close to the membrane layer. 相似文献
92.
93.
94.
Louis Sica 《Journal of Modern Optics》2013,60(16-18):2461-2468
Abstract Violation of Bell inequalities is widely regarded as a definitive test for non-locality. However, Bell correlational inequalities must always be satisfied by all jointly present, cross-correlated data. The correlations of variable pairs obtained in repeated runs are not cross-correlated in this way and are not required to satisfy the Bell inequality. In addition, by using information regarded as non-local, proper joint correlations may be computed among counterfactual and measured variables. These correlations satisfy the Bell inequality, but are spatially non-stationary in angle. By using a simple symmetry condition, such considerations may be extended to inequalities in probabilities. The latter may be derived directly from correlational inequalities developed by Clauser, Horne, Shimony and Holt (CHSH). Violation of either correlational or probabilistic Bell inequalities then implies that the Bell correlation cannot be accounted for by a stochastic process that is spatially stationary in angle coordinates. However, other processes may still be allowed. 相似文献
95.
96.
97.
Treatment of complex gaseous emissions emitted by a rendering facility using a semi‐industrial biofilter
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
98.
An X‐FEM‐based numerical–asymptotic expansion for simulating a Stokes flow near a sharp corner
下载免费PDF全文
![点击此处可从《International journal for numerical methods in engineering》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Louis C. Foucard Franck J. Vernerey 《International journal for numerical methods in engineering》2015,102(2):79-98
A numerical technique that is based on the integration of the asymptotic solution in the numerical framework for computing the local singular behavior of Stokes flow near a sharp corner is presented. Moffat's asymptotic solution is used, and special enriched shape functions are developed and integrated in the extended finite element method (X‐FEM) framework to solve the Navier–Stokes equations. The no‐slip boundary condition on the walls of the corner is enforced via the use of Lagrange multipliers. Flows around corners with different angles are simulated, and the results are compared with both those of the known analytic solution and the X‐FEM with no special enrichment near the corner. The results of the present technique are shown to greatly reduce the error made in computing the pressure and velocity fields near a corner tip without the need for mesh refinement near the corner. The method is then applied to the estimation of the permeability of a network of fibers, where it is shown that the local small‐scale pressure singularities have a large impact on the large‐scale network permeability. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
99.
Louis de Redon 《The International journal of environmental studies》2013,70(5):722-744
This speculative opinion is based on an apparent dream caused by Donald Trump’s decision to withdraw the U.S. from the Paris Agreement. The account includes a comparison between arguments against the abolition of slavery and those against ending a fossil-fuel based economy in favor of sustainability through a green approach. Recent social disturbance in France shows that a carbon tax has not been persuasively advocated. But it should be clear that unchanged laissez-faire economics will produce disaster in light of the facts about global heating and climate change. This account is based on historical and contemporary quotations from American political figures from both the XIX and XXI centuries. The parallels raise fundamental issues of human rights. 相似文献
100.