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   276212篇
  免费   2196篇
  国内免费   661篇
化学   146877篇
晶体学   4236篇
力学   12210篇
综合类   9篇
数学   31054篇
物理学   84683篇
  2019年   2407篇
  2018年   3226篇
  2017年   3208篇
  2016年   4650篇
  2015年   2806篇
  2014年   4434篇
  2013年   11172篇
  2012年   8384篇
  2011年   10278篇
  2010年   7368篇
  2009年   7114篇
  2008年   9667篇
  2007年   9830篇
  2006年   9193篇
  2005年   8345篇
  2004年   7716篇
  2003年   6970篇
  2002年   6894篇
  2001年   7466篇
  2000年   5804篇
  1999年   4481篇
  1998年   3959篇
  1997年   3953篇
  1996年   3722篇
  1995年   3431篇
  1994年   3592篇
  1993年   3314篇
  1992年   3794篇
  1991年   3794篇
  1990年   3691篇
  1989年   3543篇
  1988年   3677篇
  1987年   3595篇
  1986年   3404篇
  1985年   4507篇
  1984年   4775篇
  1983年   3983篇
  1982年   4139篇
  1981年   4067篇
  1980年   4033篇
  1979年   4008篇
  1978年   4312篇
  1977年   4221篇
  1976年   4283篇
  1975年   3965篇
  1974年   3983篇
  1973年   4148篇
  1972年   2900篇
  1971年   2420篇
  1970年   2193篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The European Physical Journal E - The temperature-induced microphase separation of the binary liquid system iso-butyric acid+heavy water (iBA + D2O) in a mesoporous silica glass (CPG-10-75) of...  相似文献   
102.
Frank  A. I.  Nosov  V. G. 《JETP Letters》2004,79(7):313-315
JETP Letters - The problem of storing ultracold neutrons over a plane magnetic mirror in the presence of gravity is considered. For neutrons with a definite polarization, the sum of the magnetic...  相似文献   
103.
Bibliography: 42 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 306, 2003, pp. 7–15.  相似文献   
104.
105.
Substituted coumarins are synthesized from phenols and β-ketoesters by the Pechmann reaction, using a Wells-Dawson heteropolyacid (H6P2W18O62·24H2O) as catalyst by a solvent-free procedure. This one requires low reaction times, 130 °C temperature and as little as 1 mol % of Wells-Dawson acid, obtaining good to excellent yields of coumarins. The catalyst showed to be reusable with no differences in the yields. The results are compared with those of the reactions performed in toluene solution. The presented synthetic procedure is a convenient, clean and fast alternative for synthesizing 4-substituted coumarins (17 examples).  相似文献   
106.
The distribution of mono- poly- and unlabelled protein molecules in the radiolabelling mixture was calculated from probability point of view as a function of the radioiodine/protein ratio.  相似文献   
107.
On the basis of a computer analysis of four classes of toxic polypeptides, generalized primary structures of each class have been obtained which can be used for planning the synthesis of biologically active compounds.  相似文献   
108.
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   
109.
The precision of intensity modulated fiber optic sensor systems mainly is restricted by the attenuation characteristics of the analog fiber optical data link. Special encoding and referencing schemes are used to overcome this data link dependence. In this paper encoding and referencing principles for optical sensors are outlined and compared. Especially the two wavelengths referencing and the optical delay line processing techniques are discussed in more detail and results are presented.  相似文献   
110.
The synergetic effect of corrosion and corrosion induced hydrogen embrittlement damage processes which occur at local scale has been found to result in a dramatic macroscopic tensile ductility loss of the 2024 aluminum alloy. In the present work, the tensile behaviour of corroded 2024 T351 specimens has been estimated on the basis of FE analysis by taking into account the local material properties in the damaged areas. A parametric study is involved to account for the effect of thickness in the results. Calculated tensile properties obtained with the analysis agree well with experimental data.  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