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   2853篇
  免费   177篇
  国内免费   27篇
化学   1781篇
晶体学   30篇
力学   80篇
数学   207篇
物理学   506篇
无线电   453篇
  2024年   22篇
  2023年   60篇
  2022年   172篇
  2021年   251篇
  2020年   120篇
  2019年   146篇
  2018年   130篇
  2017年   110篇
  2016年   203篇
  2015年   130篇
  2014年   169篇
  2013年   189篇
  2012年   227篇
  2011年   189篇
  2010年   123篇
  2009年   86篇
  2008年   108篇
  2007年   101篇
  2006年   99篇
  2005年   90篇
  2004年   59篇
  2003年   49篇
  2002年   33篇
  2001年   14篇
  2000年   11篇
  1999年   9篇
  1998年   7篇
  1997年   6篇
  1996年   8篇
  1995年   11篇
  1994年   8篇
  1993年   7篇
  1992年   7篇
  1991年   6篇
  1990年   9篇
  1989年   7篇
  1988年   7篇
  1987年   5篇
  1985年   7篇
  1984年   8篇
  1983年   5篇
  1982年   5篇
  1981年   18篇
  1980年   7篇
  1979年   4篇
  1978年   2篇
  1976年   3篇
  1965年   3篇
  1935年   1篇
  1934年   1篇
排序方式: 共有3057条查询结果,搜索用时 187 毫秒
81.
82.
83.
84.
Journal of Thermal Analysis and Calorimetry - In this investigation, a series of experiments were conducted to explore the effects of liquefied petroleum gas (LPG) mixture of 60% propane and 40%...  相似文献   
85.
Transparent inorganic‐polymer nanocomposite films are of tremendous current interest inemerging solar coverings including photovoltaic encapsulants and commercial greenhouse plastics, but suffer from significant radiative heat loss. This work provides a new and simple approach for controlling this heat loss by using mesoporous silica/quantum dot nanoparticles in poly(ethylene‐co‐vinyl acetate) (EVA) films. Mesoporous silica shells were grown on CdS‐ZnS quantum dot (QDs) cores using a reverse microemulsion technique, controlling the shell thickness. These mesoporous silica nanoparticles (MSNs) were then melt‐mixed with EVA pellets using a mini twin‐screw extruder and pressed into thin films of concentration variable controlled thickness. The results demonstrate that the experimental MSNs showed improved infrared and thermal wavebands retention in the EVA transparent films compared to commercial silica additives, even at lower concentrations. It was also found MSNs enhanced the quantum yield and photostability of the QDs, providing high visible light transmission and blocking of UV transmission of interest for next generation solar coatings. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 851–859  相似文献   
86.
In this paper, we consider a carrier sense multiple access based wireless local area network (WLAN) with a successive interference cancellation (SIC) technique. We develop an analytical model to compute the average throughput of a user in a WLAN with the SIC technique in presence of path loss, Rayleigh fading and log-normal shadowing. We then validate the model via simulation. By means of the developed analytical model, we compute the average throughput of a user in WLAN systems without and with the SIC technique and evaluate the throughput gain provided by the SIC technique. We find that the throughput gain provided by the SIC technique is significant. However, the throughput gain varies significantly depending on the parameters of network and wireless channel. We find that the throughput gain provided by the SIC technique increases with increasing the number of users in WLAN, medium access rate of the users and the variance in shadowing and it decreases with increasing the data transmission rate. We also investigate the effect of the decoding capability of the SIC technique on the throughput performance. We find that throughputs obtained with decoding capability of 2 and 3 packets are very close.  相似文献   
87.
Molecular Diversity - In the present work, a series of bisbenzazole derivatives were designed and synthesized as antiproliferative agents. The antiproliferative activity of these compounds was...  相似文献   
88.
Dopamine (DA) is an important neurotransmitter, which is created and released from the central nervous system. It plays a crucial role in human activities, like cognition, emotions, and response to anything. Maladjustment of DA in human blood serum results in different neural diseases, like Parkinson's and Schizophrenia. Consequently, researchers have started working on DA detection in blood serum, which is undoubtedly a hot research area. Electrochemical sensing techniques are more promising to detect DA in real samples. However, utilizing conventional electrodes for selective determination of DA encounters numerous problems due to the coexistence of other materials, such as uric acid and ascorbic acid, which have an oxidation potential close to DA. To overcome such problems, researchers have put their focus on the modification of bare electrodes. The aim of this review is to present recent advances in modifications of most used bare electrodes with carbonaceous materials, especially graphene, its derivatives, and carbon nanotubes, for electrochemical detection of DA. A brief discussion about the mechanistic phenomena at the electrode interface has also been included in this review.  相似文献   
89.
90.
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