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   131766篇
  免费   22450篇
  国内免费   15098篇
化学   91364篇
晶体学   1687篇
力学   8737篇
综合类   916篇
数学   15475篇
物理学   51135篇
  2024年   289篇
  2023年   2466篇
  2022年   4468篇
  2021年   4609篇
  2020年   5147篇
  2019年   5081篇
  2018年   4330篇
  2017年   4176篇
  2016年   6256篇
  2015年   6122篇
  2014年   7527篇
  2013年   9789篇
  2012年   11848篇
  2011年   12434篇
  2010年   8511篇
  2009年   8357篇
  2008年   8832篇
  2007年   7939篇
  2006年   7311篇
  2005年   6116篇
  2004年   4553篇
  2003年   3629篇
  2002年   3436篇
  2001年   2808篇
  2000年   2428篇
  1999年   2603篇
  1998年   2200篇
  1997年   2038篇
  1996年   2171篇
  1995年   1747篇
  1994年   1708篇
  1993年   1362篇
  1992年   1226篇
  1991年   1094篇
  1990年   907篇
  1989年   638篇
  1988年   539篇
  1987年   439篇
  1986年   438篇
  1985年   357篇
  1984年   262篇
  1983年   181篇
  1982年   153篇
  1981年   119篇
  1980年   85篇
  1979年   62篇
  1978年   40篇
  1976年   41篇
  1975年   39篇
  1974年   50篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
81.
82.
In the present research, hierarchical structure observation and mechanical property characterization for a type of biomaterial are carried out. The investigated biomaterial is Hyriopsis cumingii, a typical limnetic shell, which consists of two different structural layers, a prismatic "pillar"structure and a nacreous "brick and mortar" structure. The prismatic layer looks like a "pillar forest" with variationsection pillars sized on the order of several tens of microns.The nacreous material looks like a "brick wall" with bricks sized on the order of several microns. Both pillars and bricks are composed of nanoparticles. The mechanical properties of the hierarchical biomaterial are measured by using the nanoindentation test. Hardness and modulus are measured for both the nacre layer and the prismatic layer, respectively.The nanoindentation size effects for the hierarchical structural materials are investigated experimentally. The results show that the prismatic nanostructured material has a higher stiffness and hardness than the nacre nanostructured material.In addition, the nanoindentation size effects for the hierarchical structural materials are described theoretically, by using the trans-scale mechanics theory considering both strain gradient effect and the surface/interface effect. The modeling results are consistent with experimental ones.  相似文献   
83.
84.
85.
Guo  Yan  Li  Zhuang  Wei  Yuxi  Zhang  Xinxu  Shi  Kexin 《Journal of Solid State Electrochemistry》2022,26(4):1051-1065
Journal of Solid State Electrochemistry - Polyvinylpyrrolidone (PVP) and graphene (G)-modified iron oxides (Fe2O3-PVP-G) are prepared by a simple hydrothermal reaction. Their morphology and...  相似文献   
86.
Journal of Solid State Electrochemistry - Due to their distinctive chemical, electronic, and environmental properties, polypyrrole is used as a blocking barrier for methanol leakage in direct...  相似文献   
87.
Crystallography Reports - A cobalt coordination polymer, {[Co(L1)2(H2O)2] · (HCOO)2 · H2O}n, where L1 is a bis(4-(1H-imidazol-1-yl)phenyl)methanone, has been synthesized and characterized...  相似文献   
88.
The Ramanujan Journal - Inspired by Andrews and Merca’s recent work on the number of even parts over all partitions into distinct parts, we introduce a new kind of Beck type identities, which...  相似文献   
89.
The design and exploration of efficient, stable and environmentally compatible organic emitters for an electrochemiluminescence (ECL) sensor is a promising topic. Herein, a novel environmentally-friendly luminophore, ZnBCBTP@MWCNTs, were fabricated via self-assembly of porphyrin molecules (ZnBCBTP) onto multi-walled carbon nanotubes (MWCNTs). The resulting luminophore ZnBCBTP@MWCNTs displayed not only the highly ECL property and but also the good accelerated electron mobility. Then, a label-free ECL biosensor based ZnBCBTP@MWCNTs was constructed for the ultrasensitive detection of uric acid. Excitingly, this proposed ECL biosensor performed a good linear relationship in the range of 0–300 μM with a low detection limit of 1.4 μM, thus offering another reliable and feasible sensing platform for clinical bioanalysis with good selectivity, stability, and repeatability.  相似文献   
90.
Journal of Thermal Analysis and Calorimetry - A complete analysis of the thermal process about melamine was presented, in which different methods were applied to determine the characteristic of the...  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