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   2551篇
  免费   42篇
  国内免费   3篇
化学   1897篇
晶体学   4篇
力学   14篇
数学   313篇
物理学   368篇
  2023年   13篇
  2020年   13篇
  2019年   18篇
  2018年   14篇
  2017年   15篇
  2016年   38篇
  2015年   50篇
  2014年   52篇
  2013年   136篇
  2012年   158篇
  2011年   166篇
  2010年   80篇
  2009年   66篇
  2008年   173篇
  2007年   170篇
  2006年   189篇
  2005年   165篇
  2004年   134篇
  2003年   95篇
  2002年   74篇
  2001年   69篇
  2000年   81篇
  1999年   27篇
  1998年   15篇
  1997年   26篇
  1996年   32篇
  1995年   26篇
  1994年   25篇
  1993年   18篇
  1992年   25篇
  1991年   18篇
  1990年   22篇
  1989年   10篇
  1988年   22篇
  1987年   12篇
  1986年   21篇
  1985年   29篇
  1984年   16篇
  1983年   20篇
  1982年   17篇
  1981年   14篇
  1980年   22篇
  1979年   18篇
  1978年   14篇
  1977年   14篇
  1976年   16篇
  1974年   19篇
  1973年   15篇
  1972年   9篇
  1971年   10篇
排序方式: 共有2596条查询结果,搜索用时 31 毫秒
1.
2.
We describe the synthesis and the physical properties of polyaromatic hydrocarbons (PAHs) containing a phosphorus atom at the edge. In particular, the impact of the successive addition of aromatic rings on the electronic properties was investigated by experimental (UV/Vis absorption, fluorescence, cyclic voltammetry) and theoretical studies (DFT). The physical properties recorded in solution and in the solid state showed that the P‐containing PAHs exhibit properties expected for an emitter in white organic light‐emitting diodes (WOLEDs).  相似文献   
3.
4.
Unsteady motion in single-line flow-injection systems consisting of n tubular elements with valve or hydrodynamic injection is studied theoretically. A formula for the duration of the initial period of unsteady flow is derived. This initial period is much shorter than the mean residence time of the analyte in practical systems. It can therefore be neglected in mathematical modelling of such systems. Experimental data obtained with single-line systems with valve and hydrodynamic injection confirmed the validity of the theoretical equations.  相似文献   
5.
The function lattice, or generalized Boolean algebra, is the set of ℓ-tuples with the ith coordinate an integer between 0 and a bound ni. Two ℓ-tuples t-intersect if they have at least t common nonzero coordinates. We prove a Hilton–Milner type theorem for systems of t-intersecting ℓ-tuples.Received September 29, 2004  相似文献   
6.
Marcel Erné 《Order》1991,8(2):159-173
We introduce a special type of order-preserving maps between quasiordered sets, the so-called cut-stable maps. These form the largest morphism class such that the corresponding category of quasiordered sets contains the category of complete lattices and complete homomorphisms as a full reflective subcategory, the reflector being given by the Dedekind-MacNeille completion (alias normal completion or completion by cuts). Suitable restriction of the object class leads to the category of separated quasiordered sets and its full reflective subcategory of completely distributive lattices. Similar reflections are obtained for continuous lattices, algebraic lattices, etc.  相似文献   
7.
This review summarizes different applications of optical spectroscopic methods in calixarene chemistry including UV/Vis spectrometry, vibrational spectroscopic techniques (FTIR and Raman spectroscopy), luminescence spectroscopy (including fluorescence and phosphorescence), ellipsometry and various optical microscopic methods. Moreover, the results of theoretical studies (AM1, PM3, DFT, ab initio, etc.) are summarized based on selected papers in the field of conformational studies, thermodynamics and complexation features. About 300 references are processed systematically from the results reported mainly in the recent years with emphasis on the potential of practical application of these molecules.  相似文献   
8.
A quick sample preparation method was used for the determination of sulphur and trace metals in oil and oily products by the ICP with a minitorch. Stable aqueous emulsions of oils and oil products were made by using two kinds of emulsifiers (one with low sulphur content, the other sulfonated). Aqueous standard solutions can be used for the preparation of calibration solutions. The contents of S, Al, Cr, Cu, Fe, Mg, Ni and Pb in aqueous emulsions were determined and the results were in good agreement with the composition of oil standard solutions used for control analysis procedure.  相似文献   
9.
Jenó Szigeti 《Order》1990,7(1):77-81
Given a linearly ordered set (A, R ) and an R-monotone function f: AA, we give a necessary and sufficient condition on A, f, R , involving generating sets and forbidden subalgebras, for R to be a well-ordering.Partially supported by Hungarian National Foundation for Scientific Research Grant nr. 1813.  相似文献   
10.
By a result of Pigozzi and Kogalovskii, every algebraic latticeL having a completely join —irreducible top element can be represented as the lattice L() of equational theories extending some fixed theory . Conversely, strengthening a recent result due to Lampe, we show that such a representationL=L() forcesL to satisfy the following condition: if the top element ofL is the join of a nonempty subsetB ofL then there are elementsb..., B such thata=(... (((b1 a) b2) a) ... bn) a for alla L. In presence of modularity, this equation reduces to the identitya=(a b1) ... (a bn). Motivated by these facts, we study several weak forms of distributive laws in arbitrary lattices and related types of prime elements. The main tool for applications to universal algebra is a generalized version of Lampe's Zipper Lemma.Presented by Ralph Freese.  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