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   91425篇
  免费   955篇
  国内免费   417篇
化学   33516篇
晶体学   1005篇
力学   7128篇
综合类   1篇
数学   32925篇
物理学   18222篇
  2023年   168篇
  2022年   377篇
  2021年   429篇
  2020年   467篇
  2019年   529篇
  2018年   10759篇
  2017年   10559篇
  2016年   6677篇
  2015年   1308篇
  2014年   1038篇
  2013年   1555篇
  2012年   4806篇
  2011年   11502篇
  2010年   6313篇
  2009年   6575篇
  2008年   7244篇
  2007年   9384篇
  2006年   763篇
  2005年   1770篇
  2004年   1877篇
  2003年   2251篇
  2002年   1249篇
  2001年   394篇
  2000年   415篇
  1999年   248篇
  1998年   262篇
  1997年   242篇
  1996年   288篇
  1995年   187篇
  1994年   144篇
  1993年   184篇
  1992年   148篇
  1991年   139篇
  1990年   116篇
  1989年   129篇
  1988年   107篇
  1987年   102篇
  1986年   99篇
  1985年   109篇
  1984年   105篇
  1983年   90篇
  1982年   88篇
  1981年   77篇
  1980年   91篇
  1979年   105篇
  1978年   83篇
  1977年   71篇
  1976年   57篇
  1975年   50篇
  1973年   49篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
12.
13.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  相似文献   
14.
15.
16.
17.
A facile synthetic strategy towards conformationally stable chiral chromophores based on dimeric porphyrinoids has been established. A peculiar class of face-to-face intramolecularly interlocked corrole dimers were formed by the oxidative C−C coupling linked at the inner carbon sites upon simple treatment of copper(II) ions. Their intrinsic electronic structures were modulated by the peripheral corrole ring annulations, which lead to distinct optical properties and redox profiles. The stereogenic carbon centers implemented in the confused corrole skeleton provided a rationale for designing novel chiral materials.  相似文献   
18.
Journal of Thermal Analysis and Calorimetry - In the case of flow boiling, the prediction of vapour fraction in the horizontal microchannel is a severe issue using the numerical technique....  相似文献   
19.
Journal of Thermal Analysis and Calorimetry - Nanofluids have gained recent attention because of their potential applications in diverse engineering fields like enhancing thermal transport,...  相似文献   
20.
In the present work, the use of cylindrical turbulators in a double pipe heat exchanger has been investigated. Cylindrical fin type of turbulators has been placed circumferentially separated by 90° on the outer side of an inner pipe at a regular pitch. Experimental studies were undertaken for different air flow rates in a turbulent regime whose Reynolds number range between 2500 and 10000. Heat transfer characteristics like Nu and friction factor have been experimentally determined. Parametric studies were conducted by changing the pitch and also the orientation of the turbulators. Nu and friction factor were found to increase as the pitch is reduced. A model with alternatively changed orientation outperformed others by exhibiting highest Nu and reduced friction factor.  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