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   1070篇
  免费   189篇
  国内免费   120篇
化学   444篇
晶体学   10篇
力学   82篇
综合类   74篇
数学   218篇
物理学   551篇
  2024年   2篇
  2023年   13篇
  2022年   39篇
  2021年   46篇
  2020年   44篇
  2019年   30篇
  2018年   28篇
  2017年   52篇
  2016年   51篇
  2015年   28篇
  2014年   50篇
  2013年   68篇
  2012年   36篇
  2011年   47篇
  2010年   51篇
  2009年   44篇
  2008年   84篇
  2007年   60篇
  2006年   64篇
  2005年   47篇
  2004年   58篇
  2003年   46篇
  2002年   46篇
  2001年   49篇
  2000年   48篇
  1999年   21篇
  1998年   26篇
  1997年   22篇
  1996年   21篇
  1995年   9篇
  1994年   12篇
  1993年   18篇
  1992年   12篇
  1991年   15篇
  1990年   12篇
  1989年   3篇
  1988年   8篇
  1987年   9篇
  1986年   8篇
  1985年   9篇
  1984年   11篇
  1983年   4篇
  1982年   8篇
  1981年   3篇
  1980年   2篇
  1979年   6篇
  1978年   2篇
  1976年   3篇
  1974年   1篇
  1973年   1篇
排序方式: 共有1379条查询结果,搜索用时 15 毫秒
91.
Auguste Besson 《Pramana》2004,62(3):537-540
The RunII of the Dø experiment was started in March 2001. The first preliminary results on searches for new physics are presented, with a luminosity of ~ 10 pb?1 from the data collected in 2001-2002. We report results in mSUGRA (jets + missingEt channel), GMSB (diphotons), RPV (trileptons and like sign dileptons) and large extra dimensions (dielectrons and diphotons).  相似文献   
92.
NMR spectroscopy, capillary GLC, and GLC-MS are used to study the composition of free and sulfated sterols from the far-east starfishLeptasterias alaskensis asiatica(Fischer) andL. Fisheri(Djakonov). The total free sterols of both species are shown to have similar qualitative and quantitative compositions and contain mainly7 -sterols. Sterol sulfate fractions contain cholesterol sulfate as the main component but differ in the ratios of5 :0 :7 -sterol derivatives. Possible reasons for these differences are discussed. A new steroid, 3-hydroxycholest-5-en-7-one sulfate, was isolated.  相似文献   
93.
Chemical Composition of Certain Sedum Species of Kazakhstan   总被引:2,自引:0,他引:2  
The chemical composition of sevenSedumspecies growing in Kazakhstan was studied by chromatography. The contents of seven groups of natural compounds were determined. Comparison with markers and literature data identified 24 compounds including 9 that have not been described previously inSedumspecies  相似文献   
94.
Geometric process (GP) was introduced by Lam[4,5], it is defined as a stochastic process {Xn, n = 1, 2,…} for which there exists a real number a > 0, such that {an-1 Xn, n = 1,2, …} forms a renewal process (RP). In this paper, we study some limit theorems in GP. We first derive the Wald equation for GP and then obtain the limit theorems of the age, residual life and the total life at t for a GP. A general limit theorem for Sn with a > 1 is also studied. Furthermore, we make a comparison between GP and RP, including the comparison of their limit distributions of the age, residual life and the total life at t.  相似文献   
95.
One of the most important problems of coding theory is to constructcodes with best possible minimum distances. In this paper, we generalize the method introduced by [8] and obtain new codes which improve the best known minimum distance bounds of some linear codes. We have found a new linear ternary code and 8 new linear codes over with improved minimumdistances. First we introduce a generalized version of Gray map,then we give definition of quasi cyclic codes and introduce nearlyquasi cyclic codes. Next, we give the parameters of new codeswith their generator matrices. Finally, we have included twotables which give Hamming weight enumerators of these new codes.  相似文献   
96.
新的奇偶非线性相干态及其非经典性质   总被引:1,自引:0,他引:1       下载免费PDF全文
孟祥国  王继锁 《物理学报》2007,56(4):2154-2159
构造出了一种新的奇偶非线性相干态, 并借助于数值计算方法研究了它们的压缩、振幅平方压缩、反聚束和相位概率分布等非经典性质. 结果表明, 与通常的奇偶相干态和非线性奇偶相干态不同, 在参数|λ|的不同取值范围内, 新的奇偶非线性相干态在Y1Y2两个方向均可呈现振幅平方压缩效应, 而压缩效应仅在偶非线性相干态的X2方向上呈现, 反聚束效应仅在奇非线性相干态中呈现. 另外, 通过研究新的奇偶非线性相干态相位概率分布, 发现新的奇偶非线性相干态具有完全不同的量子干涉特性. 关键词: 新的奇偶非线性相干态 压缩效应 反聚束 相位概率分布  相似文献   
97.
在矢势与标势相等的情况下,对Hartmann势加新环型势的Klein-Gordon方程精确求解.给出了归一化的角向和径向波函数,同时获得了能谱方程.  相似文献   
98.
A new fluorogenic probe for sodium new houttuyfonate (SNH) was proposed. 4‐Methylumbelliferyl‐2,4‐dinitrobenzenesulfonate (4‐MUDNBS) was a nonfluorescent compound and was synthesized via the one‐step reaction of 4‐methylumbelliferone (4‐MU) with 2,4‐dinitrobenzenesulfonyl chloride. In basic media, SNH was decomposed to produce sodium sulfite, which then reacted with 4‐MUDNBS to yield highly fluorescent 4‐MU, hence leading to the fluorescence increase of the reaction solution. A linear correlation existed between the emission intensity and the concentration of SNH within the range from 0.5 to 15 μg·mL−1 with a detection limit of 0.15 μg· mL−1 (3δ). The effect of substituents on the benzenesulfonyl moiety of the probe is discussed, and the presence of electronegative groups is favorable for the proposed cleavage reaction.  相似文献   
99.
Abstract We show that with symmetric agents, noncooperation is the only stable coalition structure in a fishery with more than two countries. In the case of asymmetric fishing nations, partial or full cooperation may be stable even if the number of countries exceeds two. These are important results for recent fisheries economics papers that have not allowed for coalition formation. As an example how of one can use the model, we study the problem of new entrants into Regional Fisheries Management Organizations (RFMOs). We show that depending on the economic structure of the fishery, new entrants may make cooperation more difficult or easier.  相似文献   
100.
纳米科学技术及其在军事领域的应用展望   总被引:1,自引:0,他引:1  
本文对作21世纪高新技术之一的纳米科学技术进行了阐述,并结合当前国内外的进展,就其在军用新材料技术,隐身技术,武器研制技术和军用电子技术等四个领域中在未来军事战争中的应用进行了阐述和展望。  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