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   130055篇
  免费   190篇
  国内免费   115篇
化学   48282篇
晶体学   2018篇
力学   8157篇
综合类   7篇
数学   27623篇
物理学   44273篇
  2018年   9844篇
  2017年   10811篇
  2016年   4717篇
  2015年   1150篇
  2014年   424篇
  2013年   1028篇
  2012年   5370篇
  2011年   14400篇
  2010年   8347篇
  2009年   8469篇
  2008年   12358篇
  2007年   16283篇
  2006年   921篇
  2005年   8188篇
  2004年   4371篇
  2003年   4276篇
  2002年   2068篇
  2001年   903篇
  2000年   888篇
  1999年   497篇
  1998年   412篇
  1997年   370篇
  1996年   512篇
  1995年   507篇
  1994年   465篇
  1993年   425篇
  1992年   454篇
  1991年   495篇
  1990年   469篇
  1989年   471篇
  1988年   456篇
  1987年   444篇
  1986年   430篇
  1985年   531篇
  1984年   562篇
  1983年   442篇
  1982年   453篇
  1981年   468篇
  1980年   441篇
  1979年   472篇
  1978年   481篇
  1977年   366篇
  1976年   425篇
  1975年   365篇
  1974年   350篇
  1973年   405篇
  1969年   241篇
  1968年   296篇
  1967年   384篇
  1966年   343篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Russian Journal of General Chemistry - The review article traces the main trends of the synthetic approach to the solution of the problem of overcoming the resistance of pathogenic bacterial...  相似文献   
2.
The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information.  相似文献   
3.
4.
5.
6.
7.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
8.
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   
9.
10.
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied.  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