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   428034篇
  免费   3998篇
  国内免费   950篇
化学   216625篇
晶体学   6798篇
力学   19439篇
综合类   16篇
数学   58833篇
物理学   131271篇
  2019年   2715篇
  2018年   11473篇
  2017年   12277篇
  2016年   9214篇
  2015年   4539篇
  2014年   5556篇
  2013年   14952篇
  2012年   14653篇
  2011年   24929篇
  2010年   15574篇
  2009年   15279篇
  2008年   21750篇
  2007年   25073篇
  2006年   11365篇
  2005年   16924篇
  2004年   12521篇
  2003年   11540篇
  2002年   9358篇
  2001年   9549篇
  2000年   7527篇
  1999年   5706篇
  1998年   4650篇
  1997年   4526篇
  1996年   4661篇
  1995年   4339篇
  1994年   4035篇
  1993年   3945篇
  1992年   4695篇
  1991年   4501篇
  1990年   4384篇
  1989年   4389篇
  1988年   4429篇
  1987年   4443篇
  1986年   4200篇
  1985年   5561篇
  1984年   5608篇
  1983年   4571篇
  1982年   4933篇
  1981年   4854篇
  1980年   4654篇
  1979年   4971篇
  1978年   5106篇
  1977年   5050篇
  1976年   4925篇
  1975年   4589篇
  1974年   4393篇
  1973年   4614篇
  1972年   2987篇
  1968年   2851篇
  1967年   2724篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Blood serum samples were irradiated by monochromatic synchrotron radiation (15 keV) and by 2.4-MeV protons to compare their performance for the detection of trace elements by x-ray fluorescence (XRF) spectrometry. Absolute concentration assignment was based on the addition of an internal standard and on a method which uses the incoherent and coherent radiation as a flux monitor of the incoming beam. Preliminary experiments with a synchrotron XRF microprobe are reported.  相似文献   
133.
Summary Three weak variants of compactness which lie strictly between compactness and quasicompactness, are introduced. Their basic properties are studied. The interplay with mapping and their direct and inverse preservation under mappings are investigated. In the process three decompositions of compactness are observed.  相似文献   
134.
135.
136.
We show that the Hardy-Littlewood maximal operator and a class of Calderón-Zygmund singular integrals satisfy the strong type modular inequality in variable Lp spaces if and only if the variable exponent p(x) ∼ const. Received: 15 September 2004  相似文献   
137.
A mixed problem is considered for a system of partial differential equations modeling the process of adsorption dynamics. An existence and uniqueness theorem is proved for this problem, and the solution properties are investigated. The inverse problem is posed, involving the determination of the system coefficient given additional information about the solution. A uniqueness theorem is proved for the solution of the inverse problem.__________Translated from Prikladnaya Matematika i Informatika, No. 16, pp. 5 – 14, 2004.  相似文献   
138.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive projections in Dedekind complete vector lattices and f-algebras. AMS Classification: 47B65, 46A40, 06F25  相似文献   
139.
A three-dimensional examination of blood vessels is provided using MR data from seven cases. The vascular surfaces are constructed with an algorithm that automatically follows the selected artery or vein and generates a projected three-dimensional gradient shaded image. Fast 3DFT pulse sequences were optimized to enhance the time-of-flight contrast of the intravascular region. By increasing the surface threshold value in a three-dimensional head study, the flesh of a patient's face was peeled away to demonstrate the superfacial temporal artery. Gated cardiac images show the great vessels and cardiac chambers. A three-dimensional view of the aorta shows an irregular surface in the vicinity of an adrenal tumor. 3D MR exams provide a non-invasive technique for assessing vascular morphology in a clinical setting.  相似文献   
140.
Compact, time‐harmonic, acoustic sources produce waves that decay too slowly to be square‐integrable on a line away from the sources. We introduce an inner product, arising directly from Green's second theorem, to form a Hilbert space of these waves and present examples of its computation.1 © 2005 Wiley Periodicals, Inc.  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