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   3172篇
  免费   173篇
  国内免费   199篇
化学   194篇
晶体学   1篇
力学   89篇
综合类   47篇
数学   2721篇
物理学   492篇
  2024年   3篇
  2023年   35篇
  2022年   27篇
  2021年   57篇
  2020年   40篇
  2019年   62篇
  2018年   64篇
  2017年   82篇
  2016年   68篇
  2015年   71篇
  2014年   134篇
  2013年   253篇
  2012年   124篇
  2011年   136篇
  2010年   132篇
  2009年   177篇
  2008年   236篇
  2007年   231篇
  2006年   179篇
  2005年   151篇
  2004年   135篇
  2003年   138篇
  2002年   144篇
  2001年   93篇
  2000年   107篇
  1999年   81篇
  1998年   78篇
  1997年   85篇
  1996年   57篇
  1995年   52篇
  1994年   42篇
  1993年   24篇
  1992年   26篇
  1991年   15篇
  1990年   29篇
  1989年   14篇
  1988年   14篇
  1987年   20篇
  1986年   8篇
  1985年   16篇
  1984年   14篇
  1983年   7篇
  1982年   15篇
  1981年   19篇
  1980年   8篇
  1979年   16篇
  1978年   7篇
  1977年   11篇
  1976年   2篇
  1975年   2篇
排序方式: 共有3544条查询结果,搜索用时 15 毫秒
991.
A variety of rigorous inequalities for critical exponents is proved. Most notable is the low-temperature Josephson inequalitydv +2 2–. Others are 1 1 +v, 1 1 , 1,d 1 + 1/ (for d),dv, 3 + (for d), 4 , and 2m 2m+2 (form 2). The hypotheses vary; all inequalities are true for the spin-1/2 Ising model with nearest-neighbor ferromagnetic pair interactions.NSF Predoctoral Fellow (1976–1979). Research supported in part by NSF Grant PHY 78-23952.  相似文献   
992.
I give a rigorous proof of the high-temperature Josephson inequalitydv 2–, following the original ideas of Josephson. The proof is applicable to a class of models including the ferromagnetic Ising model and the 4 lattice field theory.Research supported in part by NSF Grant PHY 78-23952.  相似文献   
993.
A carefully Standardized technique is described for the preparation of glass capillary columns which can be used successfully for routine quantitative amino acid analysis. Comparison is made between two different modes of sample injection. Preliminary quantitative results from “split” injection and “on-column” injection techniques are evaluated statistically and it is concluded that the “on-column” system is a prerequisite for quantitative amino acid analysis by glass capillary gas chromatography. An analysis of fish muscle protein hydrolyzate illustrates an application of this technique and results are compared with those from a packed column analysis.  相似文献   
994.
提出了比值导数波谱-多波长最小一乘回归分光光度法。该法能同时测定三组分混合物而毋需零交点波长和等吸收点,且回归稳健性好.可消除异常点的影响。方法用于合成样品和饮料中糖精钠、苯甲酸和山梨酸的同时测定,相对误差<± 3. 5%,回收率为 96. 6%~104.4%,相对标准偏差为2.0%~3.1%.  相似文献   
995.
Considering the uncertainty of measurement (UOM) is mandatory when assessing compliance with reference values given in compositional specifications and statutory limits, but the matter is still open to question. Working in the signal or concentration domains and considering false negative together with false positive errors are the main points of debate. Frequently, the available approaches look too simplified for being accurate or too complex (since more rigorously formulated from a theoretical point of view) for being largely acceptable. In the Authors opinion, assessing compliance with reference values given in compositional specifications and statutory limits is a problem similar to that of estimating the limit of detection. This allows proposing a simple operational approach based on well-known and accepted assumptions and approximations. This proposal, described in the light of the most recent literature information, is aimed to stimulate a critical discussion in view of evaluating possible corrections to the generally accepted approach.Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher.  相似文献   
996.
We establish local and global norm inequalities for solutions of the nonhomogeneous A-harmonic equation A(x,g+du)=h+d?v for differential forms. As applications of these inequalities, we prove the Sobolev-Poincaré type imbedding theorems and obtain Lp-estimates for the gradient operator ∇ and the homotopy operator T from the Banach space Ls(D,Λl) to the Sobolev space W1,s(D,Λl−1), l=1,2,…,n. These results can be used to study both qualitative and quantitative properties of solutions of the A-harmonic equations and the related differential systems.  相似文献   
997.
基于模糊互补判断矩阵的对数最小一乘法及算法程序设计   总被引:1,自引:0,他引:1  
利用正互反判断矩阵与模糊互补判断矩阵的转换关系,探讨模糊互补判断矩阵的一种排序方法——对数最小一乘法,并给出这种算法的程序设计.  相似文献   
998.
Moderate deviations for the quenched mean of the super-Brownian motion with random immigration are proved for 3≤d≤6, which fills in the gap between central limit theorem(CLT)and large deviation principle(LDP).  相似文献   
999.
For a wide class of symmetric trigonometric polynomials, the minimal deviation property is established. As a corollary, the extremal property is proved for the components of the Chebyshev polynomial mappings corresponding to symmetric algebras A α.  相似文献   
1000.
Fifteen international titration standards were evaluated to determine minimum and maximum combined standard uncertainties. Assuming most thorough performance of the analyses revealed minimum values, whereas maximum values of uncertainty were obtained assuming that the analyses had been done under high time pressure. Minimum and maximum uncertainties were compared with the corresponding reproducibility standard deviations. Since the combined standard uncertainty is expected to lie between the reproducibility standard deviation and the maximum combined standard uncertainty, realistic standard uncertainties of individual influence quantities of volumetric and weighing procedures could be calculated. This top-down approach revealed up to 4 times higher uncertainties for volumetric operations compared to the bottom-up approach according to the current literature. Hence, uncertainty due to volumetric operations is obviously strongly underestimated. The present study additionally contains a ranking of the contributions to the uncertainty of titrimetric results.  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