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   1157篇
  免费   30篇
  国内免费   4篇
化学   732篇
晶体学   7篇
力学   12篇
数学   164篇
物理学   276篇
  2023年   11篇
  2022年   9篇
  2021年   16篇
  2020年   23篇
  2019年   11篇
  2018年   7篇
  2017年   11篇
  2016年   29篇
  2015年   30篇
  2014年   37篇
  2013年   65篇
  2012年   66篇
  2011年   84篇
  2010年   49篇
  2009年   33篇
  2008年   52篇
  2007年   56篇
  2006年   56篇
  2005年   46篇
  2004年   43篇
  2003年   28篇
  2002年   23篇
  2001年   21篇
  2000年   15篇
  1999年   15篇
  1998年   12篇
  1997年   14篇
  1995年   10篇
  1994年   12篇
  1993年   11篇
  1992年   14篇
  1990年   12篇
  1989年   6篇
  1988年   12篇
  1985年   13篇
  1984年   10篇
  1983年   10篇
  1982年   9篇
  1981年   16篇
  1980年   13篇
  1979年   15篇
  1978年   9篇
  1977年   6篇
  1976年   8篇
  1975年   10篇
  1974年   6篇
  1972年   9篇
  1971年   8篇
  1970年   6篇
  1936年   6篇
排序方式: 共有1191条查询结果,搜索用时 15 毫秒
1.
A Lieb-Thirring-Sobolev type inequality for Pauli Hamiltonians with magnetic fields is derived. The bound is in terms of an effective field, whose energy is comparable to that of the magnetic field itself. An application to the stability of matter in magnetic fields is given. Received: 19 September 1996 / Accepted: 3 January 1997  相似文献   
2.
3.
Functional Quantization and Small Ball Probabilities for Gaussian Processes   总被引:1,自引:0,他引:1  
Quantization consists in studying the L r -error induced by the approximation of a random vector X by a vector (quantized version) taking a finite number n of values. We investigate this problem for Gaussian random vectors in an infinite dimensional Banach space and in particular, for Gaussian processes. A precise link proved by Fehringer(4) and Dereich et al. (3) relates lower and upper bounds for small ball probabilities with upper and lower bounds for the quantization error, respectively. We establish a complete relationship by showing that the same holds for the direction from the quantization error to small ball probabilities. This allows us to compute the exact rate of convergence to zero of the minimal L r -quantization error from logarithmic small ball asymptotics and vice versa.  相似文献   
4.
We consider a charged particle following the boundary of a two dimensional domain because a homogeneous magnetic field is applied. We develop the basic scattering theory for the corresponding quantum mechanical edge states. The scattering operator attains a limit for large magnetic fields which preserves Landau bands. We interpret the corresponding scattering phases in terms of classical trajectories. Communicated by Yosi Avron submitted 23/02/05, accepted 3/05/05  相似文献   
5.
6.
The modified nucleoside Πd (1) was used in the synthesis of the oligonucleotide d (TpTpΠpCpGpTpCpApApApApTpC). Diester methodology being unsatisfactory, the triester synthesis was investigated with the unnatural nucleoside. An improved method of nucleoside phosphorylation was developed for the synthesis of the fully-protected nucleotide 2e. This molecule could be cleanly and selectively deprotected, and allowed the efficient synthesis of the desired oligonucleotide.  相似文献   
7.
Zusammenfassung Die Bitterwertbestimmung nachR. Wasicky und Mitarbeitern eignet sich zur Bestimmung des Gesamtbitterstoffgehalts von Präparaten aus dem Milchsaft vonLactuca virosa.
Summary R. Wasicky's and his collaborators' method of evaluating bitters is suitable for the determination of the total contents of bitter principles of preparations derived from the milky juice of lactuca virosa.

Résumé L'appréciation des amers d'aprèsR. Wasicky et ses collaborateurs peut être utilisée pour déterminer la teneur en amers totaux de préparations à base du suc laiteux de lactuca virosa.


Zur quantitativen Bestimmung der Bitterstoffe inLactuca wurde von den Verfassern eine gustometrische Methode verwendet. Da diese grundsätzlich den kolorimetrischen Methoden gleichzustellen ist, außerdem infolge des häufigen Vorkommens von bitter schmeckenden Substanzen in biologischen Materialien ein Interesse für die Bestimmungsmöglichkeit dieser Verbindungen besteht, wurde die vorliegende Arbeit aufgenommen.Die Schriftleitung.  相似文献   
8.
[chemical reaction: see text]. Three new ent-trachylobane diterpenoids (1-3) were isolated and structures elucidated from Mitrephora glabra Scheff. (Annonaceae). Mitrephorone A (1) possesses a hexacyclic ring system with adjacent ketone moieties and an oxetane ring, both of which are unprecedented among trachylobanes. All compounds were evaluated for cytotoxicity against a panel of cancer cells, where 1 displayed the most potent and broadest activity, and against a battery of antimicrobial assays, where all compounds were approximately equipotent.  相似文献   
9.
Abstract— The interaction of serum albumin-bound acceptors with enzyme-generated and protected triplet species was studied in two types of systems. Chlorophyll-a bound to bovine and human serum albumins is efficiently excited by enzymatically generated triplet acetone and acetaldehyde. When the Chl-a concentration is much lower than that of the albumin the interaction occurs with chlorophyll in an aggregate in which one Chl-a is surrounded by several protein molecules. When the Chl-a concentration is higher than that of the protein, the aggregate contains the proteins and fluorescent chlorophylls in a 1:1 ratio. The excess chlorophylls, although able to interact with the donors, are not fluorescent.
In another study, probes bound to various specific sites of serum albumins were used as quenchers of the enzymatically generated triplet acetone. The efficiency of quenching by all the bound probes is equal and in one case even stronger than for the free probes.
A model for the interaction of the excited species contained in the enzyme with the acceptor(s) located in the protein is proposed.
The present results provide further evidence that enzyme-generated and protected triplet carbonyl species can interact through a collisional process with acceptors bound to or constituents of macromolecules.  相似文献   
10.
Klockow D  Graf GF  Auffarth J 《Talanta》1979,26(8):733-736
A technique is described for the determination of catalytically active substances, in which a slow catalysed reaction is coupled to a fast competitive reaction. One reactant, which at the same time serves as the indicator substance, is removed by the slow reaction as well as by the competitor added to the system from outside. Under suitable conditions the time for the complete removal of the indicator substance is dependent only on the rate of the catalysed reaction and consequently on the catalyst concentration. The technique is illustrated by means of the phosphate-catalysed reduction of Mo(VI) by ascorbic acid.  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