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   125879篇
  免费   4555篇
  国内免费   3398篇
化学   52450篇
晶体学   1555篇
力学   9186篇
综合类   214篇
数学   37950篇
物理学   32477篇
  2024年   90篇
  2023年   571篇
  2022年   1125篇
  2021年   1299篇
  2020年   1430篇
  2019年   1627篇
  2018年   12046篇
  2017年   11886篇
  2016年   8359篇
  2015年   2530篇
  2014年   2768篇
  2013年   3762篇
  2012年   7420篇
  2011年   14035篇
  2010年   8799篇
  2009年   9012篇
  2008年   9715篇
  2007年   11631篇
  2006年   2997篇
  2005年   3322篇
  2004年   2984篇
  2003年   3057篇
  2002年   2126篇
  2001年   1214篇
  2000年   1410篇
  1999年   1009篇
  1998年   1041篇
  1997年   942篇
  1996年   713篇
  1995年   470篇
  1994年   388篇
  1993年   331篇
  1992年   293篇
  1991年   301篇
  1990年   236篇
  1989年   222篇
  1988年   181篇
  1987年   162篇
  1986年   168篇
  1985年   137篇
  1984年   118篇
  1983年   113篇
  1982年   104篇
  1981年   90篇
  1980年   97篇
  1979年   80篇
  1978年   79篇
  1977年   65篇
  1976年   60篇
  1973年   62篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Differential Equations - For a spectrally controllable linear autonomous system with incommensurable delays, we construct a dynamic state feedback in the form of a differential-difference...  相似文献   
3.
Crystallography Reports - The crystal and molecular structures of Cl–C6H4–O–C16H33 (I) have been studied, and its differential scanning calorimetry (DSC) study is performed....  相似文献   
4.
A numerical model was developed and validated to investigate the fluid–structure interactions between fully developed pipe flow and core–shell-structured microcapsule in a microchannel. Different flow rates and microcapsule shell thicknesses were considered. A sixth-order rotational symmetric distribution of von Mises stress over the microcapsule shell can be observed on the microcapsule with a thinner shell configuration, especially at higher flow rate conditions. It is also observed that when being carried along in a fully developed pipe flow, the microcapsule with a thinner shell tends to accumulate stress at a higher rate compared to that with a thicker shell. In general, for the same microcapsule configuration, higher flow velocity would induce a higher stress level over the microcapsule shell. The deformation gradient was used to capture the microcapsule's deformation in the present study. The effect of Young's modulus on the microcapsule shell on the microcapsule deformation was investigated as well. Our findings will shed light on the understanding of the stability of core–shell-structured microcapsule when subjected to flow-induced shear stress in a microfluidic system, enabling a more exquisite control over the breakup dynamics of drug-loaded microcapsule for biomedical applications.  相似文献   
5.
Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using...  相似文献   
6.
Journal of Radioanalytical and Nuclear Chemistry - The simplified 8-oxide system (SiO2-B2O3-Na2O-Al2O3-CaO-TiO2-MoO3-La2O3) has been prepared under two types of cooling methods, and analyzed with...  相似文献   
7.
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA.  相似文献   
8.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
9.
10.
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