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   534篇
  免费   10篇
  国内免费   9篇
化学   244篇
晶体学   1篇
力学   30篇
数学   102篇
物理学   176篇
  2022年   4篇
  2021年   9篇
  2020年   7篇
  2019年   9篇
  2018年   11篇
  2017年   12篇
  2016年   16篇
  2015年   10篇
  2014年   13篇
  2013年   28篇
  2012年   22篇
  2011年   30篇
  2010年   10篇
  2009年   16篇
  2008年   30篇
  2007年   15篇
  2006年   24篇
  2005年   28篇
  2004年   24篇
  2003年   19篇
  2002年   18篇
  2001年   21篇
  2000年   13篇
  1999年   6篇
  1998年   11篇
  1997年   8篇
  1996年   6篇
  1995年   11篇
  1994年   5篇
  1993年   4篇
  1992年   8篇
  1991年   10篇
  1990年   6篇
  1988年   5篇
  1985年   6篇
  1984年   9篇
  1982年   7篇
  1981年   5篇
  1980年   2篇
  1979年   3篇
  1978年   3篇
  1977年   7篇
  1976年   5篇
  1975年   6篇
  1974年   9篇
  1973年   4篇
  1971年   4篇
  1970年   2篇
  1968年   2篇
  1967年   2篇
排序方式: 共有553条查询结果,搜索用时 31 毫秒
451.
ImmobilizedZoogloea and zooglan in calcium alginate-silica matrix was shown to have a high adsorption capacity for Cu and Cd ions. Our results showed that Cu-ion uptake in the presence of Ca and Mg ions can be enhanced using immobilizedZoogloea and zooglan. Heavy metal ion adsorption efficiency decreased in the following order: Cu > Cd > Zn > Cr. The adsorbed metal ions were desorbed completely using sulfuric acid. ImmobilizedZoogloea and zooglan which was repetitively regenerated adsorbed heavy metal ions without a loss of adsorption capacity.  相似文献   
452.
Diffusion coefficients of CoCl2, Co(NO3)2, and Cu(NO3)2 salts, characterizing permeation of their aqueous solutions across glass membranes with predominant pore radius in the range from 70 to 4.5 nm are determined. With pores in the membranes becoming narrower, the diffusion mobility of the electrolytes decreases.  相似文献   
453.
454.
Native and hydrolyzed fibroin of natural silk modified by benzimidazolyl-2-methylcarbamate hydrochloride was studied using IR spectroscopy, electron-microscopy, X-ray structure analysis, solubility, and dialysis. Mechanical treatment of a mixture of native and hydrolyzed fibroin of natural silk with benzimidazolyl-2- methtylcarbamate hydrochloride in a 2:1 ratio was shown to form inclusion complexes.  相似文献   
455.
The spectrum of a Bragg grating in a multimode optical fiber can be controlled by the number of irradiation pulses during the writing procedure. Hence, a single mode grating can be fabrication readily within a multimode fiber. The width of the stop band of the grating can also be controlled by means of the number of irradiation pulses. A tilted grating leads to the coupling of core mode to cladding mode, and when the tilt is sufficiently large, eventually to radiation mode. In the case of small tilt, the grating spectrum is the sum of the core-core mode spectrum and the core-cladding mode spectrum.  相似文献   
456.
We characterize both invariant and totally real immersions into the quaternionic projective space by the spectra of the Jacobi operator. Also, we study spectral characterization of harmonic submersions when the target manifold is the quaternionic projective space.  相似文献   
457.
The problem of interpretation of hotwire measurements of acoustic fields in compressible flows is considered. Relations between massflow and totaltemperature fluctuations registered by a hotwire anemometer and pressure and velocity fluctuations are found. The relations obtained are applicable in the general case for measurement of resultant acoustic fluctuations at some point of the flow, which are generated by arbitrary distributed sources of sound with priorunknown properties.  相似文献   
458.
本文主要研究了连通图的半边路径数目和两个辅助图的路径数目之间的一种关系.并且根据这种关系,我们给出了连通图和平面图的无符号拉普拉斯谱半径的一些上界.  相似文献   
459.
Nuclear-purity uranium was refined by passing a solution of uranyl nitrate in 3–5 M HNO3 in succession through pulsed extraction, washing, and stripping columns for feeding into the U(III)–U(IV) chemical exchange system for uranium isotope separation. The extractant (tri-n-butyl phosphate, TBP), the diluent (kerosene), nitric acid, ammonium carbonate, sodium nitrate, and water were preliminarily refined to chemical purity. The diameter and height of pulsed columns for uranium purification was 25 and 1500 mm, respectively, and the pulse frequency was 1 s–1. The content of transition metals (Fe, Co, Ni, Cu, Ag) and Pb, which can catalyze the U(III) oxidation in acidic aqueous solutions, was reduced to the level lower than 1 ppm (10–4%). The total purification factor was higher than 103. The purification required 3–4 theoretical plates with HETP of the columns of 35–40 cm.  相似文献   
460.
This is the second of two papers, in which we study the problem of prescribing Webster scalar curvature on the CR sphere as a given function f. Using the Webster scalar curvature flow, we prove an existence result under suitable assumptions on the Morse indices of f.  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