全文获取类型
收费全文 | 2389篇 |
免费 | 96篇 |
国内免费 | 7篇 |
专业分类
化学 | 1702篇 |
晶体学 | 26篇 |
力学 | 58篇 |
数学 | 331篇 |
物理学 | 375篇 |
出版年
2022年 | 18篇 |
2021年 | 25篇 |
2020年 | 22篇 |
2019年 | 26篇 |
2018年 | 22篇 |
2017年 | 12篇 |
2016年 | 57篇 |
2015年 | 54篇 |
2014年 | 66篇 |
2013年 | 158篇 |
2012年 | 130篇 |
2011年 | 154篇 |
2010年 | 95篇 |
2009年 | 73篇 |
2008年 | 131篇 |
2007年 | 138篇 |
2006年 | 144篇 |
2005年 | 123篇 |
2004年 | 133篇 |
2003年 | 101篇 |
2002年 | 93篇 |
2001年 | 21篇 |
2000年 | 29篇 |
1999年 | 22篇 |
1998年 | 26篇 |
1997年 | 29篇 |
1996年 | 34篇 |
1995年 | 25篇 |
1994年 | 27篇 |
1993年 | 25篇 |
1992年 | 17篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 13篇 |
1986年 | 20篇 |
1985年 | 34篇 |
1984年 | 33篇 |
1983年 | 23篇 |
1982年 | 22篇 |
1981年 | 30篇 |
1980年 | 31篇 |
1979年 | 20篇 |
1978年 | 18篇 |
1977年 | 23篇 |
1976年 | 15篇 |
1975年 | 21篇 |
1974年 | 13篇 |
1973年 | 21篇 |
排序方式: 共有2492条查询结果,搜索用时 15 毫秒
91.
Synchronized EPI phase contrast velocimetry in a mixing reactor 总被引:3,自引:0,他引:3
Notwithstanding its widespread use in cardiovascular and functional MRI studies, Echo Planar Imaging (EPI) has only recently been subjected to systematic validation studies. Most velocity measurement studies employing such ultrafast MRI methods involve the use of phantoms characterized by rigid or deformable solid motion. The current implementation involves a rotating phantom (angular velocity up to 10.5 rpm) with a superimposed swirling liquid flow (with axial velocities ranging between 0.145 and 0.27 cm/s) of water doped with copper sulfate. The standard implementation of single-shot EPI with phase contrast velocity encoding allows the complete mapping of the Eulerian velocity field in slices perpendicular to the rotation axis following a subtractive procedure requiring the synchronized acquisition of each velocity component on each selected transverse slice during two revolutions of the rotor. The image acquisition time is 100 ms (per velocity component) at each 64 x 64 slice. In addition to acquiring full-field velocity data for future direct comparisons with other techniques, EPI is employed here for the first time to reconstruct the three-dimensional flow field between the blades of a partitioned pipe mixer. 相似文献
92.
This paper deals with functional linear regression for spatial data. We study the asymptotic properties of an estimator of a linear model where a spatial scalar response variable is related to a spatial functional explanatory variable and to its derivative. Convergence results with rate of this estimator are derived. 相似文献
93.
94.
95.
Computational Fluid Dynamic Design of Jet Stirred Reactors for Measuring Intrinsic Kinetics of Gas‐Phase and Gas‐Solid Reactions
下载免费PDF全文
![点击此处可从《国际化学动力学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nonreactive and reactive computational fluid dynamic simulations were applied to optimize the design of a laboratory scale jet stirred reactor for measuring intrinsic kinetics of gas‐phase and gas‐solid reactions, i.e. kinetics determined by chemical steps only and not by heat or mass transfer. In the past these reactors were designed and tested based on empirical design criteria and residence time distribution experiments. This work shows that these do not always capture important local effects that are vital for kinetic studies. First the degree of macro–mixing was evaluated for three different geometries (down case, 45° case and 90° case) by performing in silico residence time distribution experiments at 900 K, showing that with these type of experiments only minor differences are observed. However, the ethane steam cracking simulations revealed major differences, with the 45° case being the most uniform in terms of temperature and the 90° case being by far the worst. The species nonuniformity in all geometries was acceptable and was in some cases even partly masked by important shortcut streams such as those observed in the 90° case. The existing gradients on the substrate surface are sufficiently small to be neglected in modeling efforts. As temperature is the major parameter determining the rate of the surface reactions, the 45° case is suggested as the best geometry for measuring intrinsic kinetics. 相似文献
96.
97.
98.
99.
100.
Dr. Christophe Kahlfuss Dr. Raymond Grüber Prof. Elise Dumont Prof. Guy Royal Floris Chevallier Dr. Saioa Cobo Prof. Eric Saint-Aman Dr. Christophe Bucher 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1573-1580
A dynamic supramolecular approach is developed to promote the π-dimerization of viologen radicals at room temperature and in standard concentration ranges. The approach involves cis- or trans-protected palladium centers serving as inorganic hinges linking two functionalized viologens endowed with metal-ion coordinating properties. Based on detailed spectroscopic, electrochemical and computational data, we show that the one-electron electrochemical reduction of the viologen units in different dynamic metal/ligand mixtures leads to the formation of the same intramolecular π-dimer, regardless of the initial environment around the metallic precursor and of the relative ratio between metal and ligand initially introduced in solution. The large-scale electron-triggered reorganization of the building blocks introduced in solution thus involves drastic changes in the stoichiometry and stereochemistry of the palladium/viologen complexes proceeding in some cases through a palladium centered trans→cis isomerization of the coordinated ligands. 相似文献