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   3108篇
  免费   187篇
  国内免费   9篇
化学   2118篇
晶体学   17篇
力学   67篇
数学   487篇
物理学   615篇
  2023年   37篇
  2022年   24篇
  2021年   60篇
  2020年   119篇
  2019年   89篇
  2018年   53篇
  2017年   51篇
  2016年   136篇
  2015年   108篇
  2014年   110篇
  2013年   124篇
  2012年   172篇
  2011年   174篇
  2010年   114篇
  2009年   86篇
  2008年   141篇
  2007年   114篇
  2006年   112篇
  2005年   87篇
  2004年   59篇
  2003年   61篇
  2002年   76篇
  2001年   32篇
  2000年   44篇
  1999年   31篇
  1998年   44篇
  1997年   28篇
  1996年   33篇
  1995年   50篇
  1994年   39篇
  1993年   28篇
  1992年   28篇
  1991年   32篇
  1990年   25篇
  1989年   21篇
  1988年   32篇
  1986年   30篇
  1985年   30篇
  1984年   27篇
  1982年   19篇
  1981年   33篇
  1980年   23篇
  1978年   36篇
  1977年   31篇
  1976年   33篇
  1975年   20篇
  1974年   32篇
  1973年   27篇
  1970年   24篇
  1967年   22篇
排序方式: 共有3304条查询结果,搜索用时 312 毫秒
101.
For more than three decades the catalytic synthesis of acrylates from the cheap and abundantly available C1 building block carbon dioxide and alkenes has been an unsolved problem in catalysis research, both in academia and industry. Herein, we describe a homogeneous catalyst based on nickel that permits the catalytic synthesis of the industrially highly relevant acrylate sodium acrylate from CO2, ethylene, and a base, as demonstrated, at this stage, by a turnover number of greater than 10 with respect to the metal.  相似文献   
102.
103.
104.
The effects of a semi-transparent reacting particle irradiation are analysed using a transient combined heat transfer model. Direct uniform irradiation is found to be favourable for particle heating and decomposition, decreasing the total reaction time by a factor of 3.3 as compared to that for non-uniform irradiation. In both cases heat transfer from the surface to the reaction zone is the process limiting mechanism.  相似文献   
105.
106.
Nitroso compounds are versatile reagents in synthetic organic chemistry. Herein, we disclose a feasible protocol for the ipso-nitrosation of aryl boronic acids using chlorotrimethylsilane–sodium nitrite unison as nitrosation reagent system.  相似文献   
107.
Quarkonium spectral functions at finite temperature are studied, making use of a recently developed method of analyzing QCD sum rules by the maximum entropy method. This approach enables us to directly obtain the spectral function from the sum rules, without having to introduce any specific assumption about its functional form. QCD sum rules for heavy quarkonia incorporate finite temperature effects in form of changing values of the various gluonic condensates that appear in the operator product expansion. These changes depend on the energy density and pressure at finite temperature, which we extract from quenched lattice QCD calculations. As a result, it is found that the charmonium ground states of both S-wave and P-wave channels dissolve into the continuum already at temperatures around or slightly above the critical temperature T c , while the bottomonium states are less influenced by temperature effects, surviving up to about 2.5 T c or higher for S-wave and about 2.0 T c for P-wave states.  相似文献   
108.
Structural constraint represents an attractive tool to modify p-block element properties without the need for unusual oxidation or valence states. The recently reported methyl-calix[4]pyrrolato aluminate established the effect of forcing a tetrahedral aluminum anion into a square-planar coordination mode. However, the generality of this structural motif and any consequence of ligand modification remained open. Herein, a systematic ligand screening was launched, and the class of square-planar aluminum anions was extended by two derivatives that differ in the meso-substitution at the calix[4]pyrrolato ligand. Strikingly, this modification provoked opposing trends in the preference for a Lewis acidic binding mode with σ-donors versus the aluminum-ligand cooperative binding mode with carbonyls. Insights into the origin of these counterintuitive experimental observations were provided by computation and bond analysis. Importantly, this rationale might allow to exploit mode-selective binding for catalytic rate control.  相似文献   
109.
NIFTy , “Numerical Information Field Theory,” is a software framework designed to ease the development and implementation of field inference algorithms. Field equations are formulated independently of the underlying spatial geometry allowing the user to focus on the algorithmic design. Under the hood, NIFTy ensures that the discretization of the implemented equations is consistent. This enables the user to prototype an algorithm rapidly in 1D and then apply it to high‐dimensional real‐world problems. This paper introduces NIFTy  3, a major upgrade to the original NIFTy  framework. NIFTy  3 allows the user to run inference algorithms on massively parallel high performance computing clusters without changing the implementation of the field equations. It supports n‐dimensional Cartesian spaces, spherical spaces, power spaces, and product spaces as well as transforms to their harmonic counterparts. Furthermore, NIFTy  3 is able to handle non‐scalar fields, such as vector or tensor fields. The functionality and performance of the software package is demonstrated with example code, which implements a mock inference inspired by a real‐world algorithm from the realm of information field theory. NIFTy  3 is open‐source software available under the GNU General Public License v3 (GPL‐3) at https://gitlab.mpcdf.mpg.de/ift/NIFTy/tree/NIFTy_3 .  相似文献   
110.
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