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   1632篇
  免费   352篇
  国内免费   226篇
化学   1110篇
晶体学   43篇
力学   113篇
综合类   16篇
数学   205篇
物理学   723篇
  2024年   4篇
  2023年   38篇
  2022年   71篇
  2021年   78篇
  2020年   80篇
  2019年   77篇
  2018年   65篇
  2017年   71篇
  2016年   86篇
  2015年   85篇
  2014年   117篇
  2013年   112篇
  2012年   159篇
  2011年   164篇
  2010年   119篇
  2009年   118篇
  2008年   121篇
  2007年   78篇
  2006年   93篇
  2005年   66篇
  2004年   47篇
  2003年   49篇
  2002年   54篇
  2001年   36篇
  2000年   16篇
  1999年   25篇
  1998年   25篇
  1997年   26篇
  1996年   20篇
  1995年   10篇
  1994年   15篇
  1993年   13篇
  1992年   5篇
  1991年   6篇
  1990年   4篇
  1989年   10篇
  1988年   8篇
  1987年   4篇
  1986年   5篇
  1985年   13篇
  1984年   4篇
  1983年   2篇
  1982年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   4篇
  1972年   1篇
  1969年   1篇
  1961年   1篇
排序方式: 共有2210条查询结果,搜索用时 31 毫秒
51.
In this paper, we study the following fractional Schrödinger equation with critical or supercritical growth where 0 < s < 1, N > 2s, λ > 0, , , ( ? Δ)s denotes the fractional Laplacian of order s and f is a continuous superlinear but subcritical function. Under some suitable conditions, we prove that the equation has a nontrivial solution for small λ > 0 by variational methods. Our main contribution is related to the fact that we are able to deal with the case .  相似文献   
52.
Ion funnel is a new-style ion guider which can reduce spatial divergence and energy dispersity of the transmission ions by using radio frequency (RF) electric field to confine the ions radially and the direct current (DC) axial electric field to move the ions toward the exit, and thus it can greatly increase the ion transmission efficiency and improve the sensitivity of the mass spectrometry. Since ion funnel was invented in 1997, it has attracted a close attention of mass spectrometry scientists all over the world. Ion funnel has been used in various kinds of mass spectrometry, and built a bridge with high efficiency ion transmission between low vacuum ionization source and high vacuum mass analyzer. In this paper, the principle, technology development, and application progress of ion funnel are reviewed, and the future prospects are prospected.  相似文献   
53.
54.
55.
Palladium-catalyzed three-component carboetherification of cyclic alkenes proceeded to give trans adducts exclusively with excellent enantioselectivity through a Wacker-type pathway. The reaction is also applicable to other oxygen nucleophiles, such as water, phenols, and carboxylic acids, as well as some electron-poor aryl amines.  相似文献   
56.
Flow segmentation based on similar motion patterns in crowded scenes remains an open problem in computer vision due to inherent complexity and vast diversity found in such scenes. To solve this problem, the streakline framework based on Lagrangian fluid dynamics had been proposed recently. However, this framework computed optical flow field using conventional optical flow method (Lucas Kanade method) which has poor anti-interference performance, and serious deviation would be brought to the computation of optical flow field. Moreover, our experimental results show that using the formulation of streak flow similarity in this framework can result in incorrect flow segmentation. Therefore, we combine this framework with a high accurate variational model, and modify the corresponding formulation of streak flow similarity after analyzing the streakline framework in detail. Finally, an improved method is proposed to solve flow segmentation in crowded scenes. Experiments are done to compare these two methods and results verify the validity and accuracy of our method.  相似文献   
57.
58.
A novel reaction of trimethylsilylated arylacetylenes with sulfonyl chlorides was performed in the presence of silver nitrate or triflate.Conjugated vinyl sulfones as dramatic products were obtained in moderate yields and with Z-selectivity.A free radical mechanism has been proposed to account for the formation of the products.  相似文献   
59.
In this paper, we study two-photon ghost interference with the approach of photon quantum theory, and calculate the coincidence counts of D 1 and D 1 detectors. With specific attention to the two-photon interference experiment carried out by Milena D’Angelo et al. (Phys. Rev. Lett. 87:013602, 2001), and find the theoretical result is accordance with experiment data.  相似文献   
60.
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