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   393780篇
  免费   2743篇
  国内免费   701篇
化学   170566篇
晶体学   5412篇
力学   18537篇
综合类   9篇
数学   52584篇
物理学   112301篇
无线电   37815篇
  2019年   2522篇
  2018年   12105篇
  2017年   12889篇
  2016年   8876篇
  2015年   3597篇
  2014年   4784篇
  2013年   11425篇
  2012年   12713篇
  2011年   22423篇
  2010年   14833篇
  2009年   14954篇
  2008年   20496篇
  2007年   24315篇
  2006年   10415篇
  2005年   15714篇
  2004年   12073篇
  2003年   11402篇
  2002年   9252篇
  2001年   8637篇
  2000年   7151篇
  1999年   5452篇
  1998年   4976篇
  1997年   4920篇
  1996年   4692篇
  1995年   4347篇
  1994年   4433篇
  1993年   4101篇
  1992年   4513篇
  1991年   4582篇
  1990年   4451篇
  1989年   4241篇
  1988年   4268篇
  1987年   3898篇
  1986年   3687篇
  1985年   4772篇
  1984年   5069篇
  1983年   4253篇
  1982年   4344篇
  1981年   4277篇
  1980年   4215篇
  1979年   4174篇
  1978年   4495篇
  1977年   4340篇
  1976年   4425篇
  1975年   4062篇
  1974年   4136篇
  1973年   4319篇
  1972年   3042篇
  1971年   2520篇
  1970年   2335篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT) started a pivotal period in indirect detection of dark matter. By outperforming expectations, for the first time a robust and stringent test of the paradigm of weakly interacting massive particles (WIMPs) is within reach. In this paper, we discuss astrophysical targets for WIMP detection and the challenges they present, review the analysis tools which have been employed to tackle these challenges, and summarize the status of constraints on and the claimed detections in the WIMP parameter space. Methods and results will be discussed in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook on short term and longer term developments.  相似文献   
102.
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method.  相似文献   
103.
104.
105.
In the present work we describe a two‐dimensional liquid chromatographic system (2D‐LC) with detection by mass spectrometry (MS) for the simultaneous separation of endogenous metabolites of clinical interest and excreted xenobiotics deriving from exposure to toxic compounds. The 2D‐LC system involves two orthogonal chromatographic modes, hydrophilic interaction liquid chromatography (HILIC) to separate polar endogenous metabolites and reversed‐phase (RP) chromatography to separate excreted xenobiotics of low and intermediate polarity. Additionally, the present proposal has the novelty of incorporating an on‐line sample treatment based on the use of restricted access materials (RAMs), which permits the direct injection of urine samples into the system. The work is focused on the instrumental coupling, studying all possible options and attempting to circumvent the problems of solvent incompatibility between the RAM device and the two chromatographic columns, HILIC and RP. The instrumental configuration developed, RAM‐HILIC‐RPLC‐MS/MS, allows the simultaneous assessment of urinary metabolites of clinical interest and excreted compounds derived from exposure to toxic agents with minimal sample manipulation. Thus, it may be of interest in areas such as occupational and environmental toxicology in order to explore the possible relationship between the two types of compounds. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
106.
107.
Technical Physics - The influence of SiO2 impurity (with a concentration varying from 0 to 10 mol %) on the stability of tetragonal ZrO2 (t-ZrO2) and on a set of micro- and macromechanical...  相似文献   
108.
Russian Physics Journal - Using the potentials, generated by a tight binding approximation, the equilibrium atomic structure and the phonon spectra of Cr and Ni thin films (one monolayer) deposited...  相似文献   
109.
110.
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