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   212617篇
  免费   22749篇
  国内免费   16389篇
化学   107482篇
晶体学   2102篇
力学   10657篇
综合类   734篇
数学   20749篇
物理学   63832篇
无线电   46199篇
  2023年   3683篇
  2022年   5198篇
  2021年   6702篇
  2020年   6731篇
  2019年   6628篇
  2018年   6465篇
  2017年   6453篇
  2016年   8293篇
  2015年   7631篇
  2014年   9818篇
  2013年   12683篇
  2012年   14527篇
  2011年   14743篇
  2010年   11144篇
  2009年   11313篇
  2008年   11866篇
  2007年   10743篇
  2006年   9997篇
  2005年   8693篇
  2004年   6875篇
  2003年   6097篇
  2002年   5866篇
  2001年   5085篇
  2000年   4419篇
  1999年   4142篇
  1998年   3675篇
  1997年   3282篇
  1996年   3149篇
  1995年   2635篇
  1994年   2510篇
  1993年   2226篇
  1992年   2079篇
  1991年   1947篇
  1990年   1785篇
  1989年   1511篇
  1988年   1309篇
  1987年   1225篇
  1986年   1165篇
  1985年   1161篇
  1984年   1102篇
  1983年   950篇
  1982年   900篇
  1981年   785篇
  1979年   848篇
  1978年   851篇
  1977年   861篇
  1976年   962篇
  1975年   842篇
  1974年   867篇
  1973年   877篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Li  Jun  Zheng  Dayong  Wei  Ning  Sun  Yunfeng  Liu  Li  Yuan  Yuan  Jiang  Qinghua 《Chemistry of Natural Compounds》2022,58(4):650-652
Chemistry of Natural Compounds - A new quassinoid, dehydrobruceantinol B (1), was isolated from the seeds of Brucea javanica, together with two known compounds, bruceantinol (2) and bruceine A (3)....  相似文献   
42.
Annals of the Institute of Statistical Mathematics - In this paper, a model averaging approach is developed for the linear regression models with response missing at random. It is shown that the...  相似文献   
43.
Xu  Mengtao  Li  Changyou  Sun  Yang  Yang  Tianzhi  Zhang  Hongzhuang  Liu  Zhendong  Liu  Haiyang  Li  Zhenyuan  Zhang  Yimin 《Nonlinear dynamics》2021,105(4):3061-3092
Nonlinear Dynamics - Investigation of the dynamic characteristics of linear guideway is essential for enhancing structural performance of machine tools. However, few mechanical models are...  相似文献   
44.
The degradation behavior of implants is significantly important for bone repair. However, it is still unprocurable to spatiotemporally regulate the degradation of the implants to match bone ingrowth. In this paper, a magneto-controlled biodegradation model is established to explore the degradation behavior of magnetic scaffolds in a magnetothermal microenvironment generated by an alternating magnetic field (AMF). The results demonstrate that the scaffolds can be heated by magnetic nanoparticles (NPs) under AMF, which dramatically accelerated scaffold degradation. Especially, magnetic NPs modified by oleic acid with a better interface compatibility exhibit a greater heating efficiency to further facilitate the degradation. Furthermore, the molecular dynamics simulations reveal that the enhanced motion correlation between magnetic NPs and polymer matrix can accelerate the energy transfer. As a proof-of-concept, the feasibility of magneto-controlled degradation for implants is demonstrated, and an optimizing strategy for better heating efficiency of nanomaterials is provided, which may have great instructive significance for clinical medicine.  相似文献   
45.
Sensitivity and multi-directional motivation are major two factors for developing optimized humidity-response materials, which are promising for sensing, energy production, etc. Organic functional groups are commonly used as the water sensitive units through hydrogen bond interactions with water molecules in actuators. The multi-coordination ability of inorganic ions implies that the inorganic ionic compounds are potentially superior water sensitive units. However, the particle forms of inorganic ionic compounds produced by classical nucleation limit the number of exposed ions to interact with water. Recent progress on the inorganic ionic oligomers has broken through the limitation of classical nucleation, and realized the molecular-scaled incorporation of inorganic ionic compounds into an organic matrix. Here, the incorporation of hydrophilic calcium carbonate ionic oligomers into hydrophobic poly(vinylidene fluoride) (PVDF) is demonstrated. The ultra-small calcium carbonate oligomers within a PVDF film endow it with an ultra-sensitive, reversible, and bidirectional response. The motivation ability is superior to other bidirectional humidity-actuators at present, which realizes self-motivation on an ice surface, converting the chemical potential energy of the humidity gradient from ice to kinetic energy.  相似文献   
46.
47.
Zhao  Kui  He  Fangmin  Meng  Jin  Wu  Hao  Zhang  Lei 《Wireless Networks》2021,27(3):1671-1681
Wireless Networks - In such mobile platforms as ships and aircraft, the detection and reconnaissance devices are near to the communication facilities. When working at the same time, they will...  相似文献   
48.
Shen  Aiguo  Ye  Qiubo  Yang  Guangsong  Hao  Xinyu 《Telecommunication Systems》2021,78(4):629-643
Telecommunication Systems - Machine to Machine technology has a broad application prospect in the 5G network, but there is a bottleneck in the energy consumption of intelligent devices powered by...  相似文献   
49.
Liu  Yi  Zhou  Guihua  Chen  Guo 《Wireless Networks》2021,27(1):195-209
Wireless Networks - TCP latency is critical to the performance of Web services. However, packet loss greatly impairs the TCP performance due to its poor loss recovery mechanisms. Recent work FUSO...  相似文献   
50.
Journal of Fourier Analysis and Applications - We develop a theory of Sobolev orthogonal polynomials on the Sierpiński gasket ( $$SG$$ ), which is a fractal set that can be viewed as a limit...  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