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   297181篇
  免费   2257篇
  国内免费   516篇
化学   142221篇
晶体学   4249篇
力学   14783篇
综合类   11篇
数学   43274篇
物理学   95416篇
  2020年   1724篇
  2019年   1922篇
  2018年   10844篇
  2017年   11728篇
  2016年   7485篇
  2015年   3043篇
  2014年   3677篇
  2013年   9209篇
  2012年   10786篇
  2011年   20333篇
  2010年   12688篇
  2009年   12778篇
  2008年   17544篇
  2007年   21039篇
  2006年   6908篇
  2005年   12791篇
  2004年   8915篇
  2003年   8443篇
  2002年   6286篇
  2001年   6299篇
  2000年   4933篇
  1999年   3559篇
  1998年   2793篇
  1997年   2721篇
  1996年   2760篇
  1995年   2538篇
  1994年   2421篇
  1993年   2245篇
  1992年   2897篇
  1991年   2774篇
  1990年   2680篇
  1989年   2685篇
  1988年   2731篇
  1987年   2731篇
  1986年   2575篇
  1985年   3321篇
  1984年   3347篇
  1983年   2619篇
  1982年   2728篇
  1981年   2789篇
  1980年   2565篇
  1979年   2927篇
  1978年   2938篇
  1977年   2979篇
  1976年   2852篇
  1975年   2583篇
  1974年   2525篇
  1973年   2529篇
  1972年   1714篇
  1968年   1798篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
41.
42.
ABSTRACT

This study was to investigate the piezotolerance and diversity indices of microflora of Indian white prawn (Fenneropenaeus indicus) after high pressure (HP)-treatment. Indian white prawns subjected to HP-treatments and its effect was studied up to species level and compared with unpressurized samples. The bacterium was identified by using bacterial identification schemes, biochemical tests and API kits (bioMérieux, Marcyl’Etoile, France). Diversity analysis was performed using PRIMER (Plymouth Routines in Multivariate Research) software v 5.2.2. The significant elimination of microflora was found to be proportional with the pressure level. In the case of spore formers, mere destruction was noticed after HP-treatment. Arthrobacter spp., Listeria grayi and Corynebacterium spp. were the most piezotolerant bacteria in HP-treated samples. Diversity indices revealed a significant reduction of microflora of Indian white prawn. The apparent reduction of microflora with pressure level was clearly evident from the diversity indices; moreover a diminished piezotolerance of Gram negative spoilage bacteria was also observed.  相似文献   
43.
44.
Journal of Solid State Electrochemistry - The “shuttle effect” of polysulfides is a serious issue, resulting in a decrease in the life-cycle of lithium-sulfur (Li-S) batteries. To...  相似文献   
45.
Journal of Thermal Analysis and Calorimetry - Low productivity of single-slope solar still is the main barrier for its worldwide usability. An attempt has been conducted to enhance the distillate...  相似文献   
46.
Journal of Thermal Analysis and Calorimetry - Modeling and computations are performed to study the ND-Co3O4/EG hybrid nanoliquid mixed convective flow past a vertical porous cylinder. The flow...  相似文献   
47.
Unsteady transitions of separation patterns in single expansion ramp nozzle   总被引:2,自引:0,他引:2  
Y. Yu  J. Xu  K. Yu  J. Mo 《Shock Waves》2015,25(6):623-633
  相似文献   
48.
49.
50.
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters.  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