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   2174篇
  免费   129篇
  国内免费   25篇
化学   1566篇
晶体学   21篇
力学   90篇
综合类   4篇
数学   280篇
物理学   367篇
  2024年   7篇
  2023年   15篇
  2022年   55篇
  2021年   99篇
  2020年   61篇
  2019年   76篇
  2018年   85篇
  2017年   63篇
  2016年   130篇
  2015年   99篇
  2014年   92篇
  2013年   237篇
  2012年   146篇
  2011年   168篇
  2010年   129篇
  2009年   103篇
  2008年   105篇
  2007年   104篇
  2006年   66篇
  2005年   63篇
  2004年   59篇
  2003年   49篇
  2002年   40篇
  2001年   18篇
  2000年   17篇
  1999年   9篇
  1998年   15篇
  1996年   16篇
  1995年   6篇
  1994年   8篇
  1993年   7篇
  1992年   9篇
  1991年   10篇
  1990年   13篇
  1989年   10篇
  1988年   9篇
  1987年   8篇
  1986年   8篇
  1985年   12篇
  1984年   9篇
  1983年   5篇
  1982年   8篇
  1981年   6篇
  1980年   7篇
  1979年   9篇
  1978年   6篇
  1977年   6篇
  1976年   12篇
  1975年   9篇
  1973年   5篇
排序方式: 共有2328条查询结果,搜索用时 15 毫秒
1.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain a decomposition of continuity.  相似文献   
2.
A simple, precise and accurate method is proposed for rapid determination of trace amounts of hydroxylamine based on the reaction of hydroxylamine with iodate in acidic media. The reaction of neutral red by the produced nitrite ion was used to monitor the reaction spectrophotometrically at 525 nm by a fixed time method. Hydroxylamine in the range of 0.0400-1.200 microg mL(-1) could be determined. The relative standard deviation for 10 determinations of 0.500 microg mL(-1) hydroxylamine was 1.81% and the limit of detection was 0.010 microg mL(-1). The proposed method was applied to the determination of hydroxylamine in water samples with satisfactory results.  相似文献   
3.
4.
5.
The H-point standard addition method (HPSAM), based on a spectrophotometric measurement for the simultaneous determination of hydrazine and acetylhydrazine, is described. This method is based on the difference between the rates of their reactions with N,N-dimethylaminobenzaldehyde (DAB) in the presence of sodium dodecyl sulfate (SDS) in acidic media. The results showed that hydrazine and acetylhydrazine could be determined simultaneously in the range of 0.020 - 0.70 and 0.20 - 5.0 mg L(-1), respectively. Under the working conditions, the proposed method was successfully applied to the simultaneous determination of hydrazine and acetylhydrazine in several synthetic mixtures and plasma and water samples.  相似文献   
6.
Pre—Separation Axioms in Fuzzifying Topology   总被引:1,自引:0,他引:1  
1  IntroductionYing[5,6 ] introduced and elementally developed so called fuzzifying topology with the semanticmethod of continuous valued L ogic.Shen[7] introduced and studied T0 -,T1-,T2 (Hausdorff) -,T3(regularity) -,T4 (normality) -separation axioms in fuzzifying topology.In [3 ]the concepts of thefamily of fuzzifying pre-open sets,fuzzifying pre-neighbourhood structure of a point and fuzzifyingpre-closure are introduced and studied.It is worth to mention that pre-separation axioms are …  相似文献   
7.
Arylation of the readily available 3‐alkythio‐5‐aryl‐1,2,4‐triazoles gave 5‐alkylthio‐1,3‐diaryl‐1,2,4‐triazoles in moderate yield. The structures of the latter were confirmed by NOE and 13C‐NMR.  相似文献   
8.
In this paper, we prove the Hyers-Ulam-Rassias stability of homomorphisms in quasi-Banach algebras associated to the Pexiderized Cauchy functional equation. This is applied to investigate homomorphisms between quasi-Banach algebras. The concept of Hyers-Ulam-Rassias stability originated from Th.M. Rassias' stability theorem that appeared in his paper [Th.M. Rassias, On the stability of the linear mapping in Banach spaces, Proc. Amer. Math. Soc. 72 (1978) 297-300].  相似文献   
9.
10.
Pongaglabol [8-hydroxy-5-phenyl-furo[2,3-h]benzo(b)pyran-7-one] was synthesized and tested for antibacterial effects againstShigella dysenteriae, Salmonella typhi, Streptococcus β-haemolyticus andStaphylococcus aureus. The synthesized compounds were characterized using UV, IR and1H NMR spectral 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