全文获取类型
收费全文 | 1934篇 |
免费 | 31篇 |
国内免费 | 9篇 |
专业分类
化学 | 982篇 |
晶体学 | 18篇 |
力学 | 60篇 |
数学 | 198篇 |
物理学 | 580篇 |
综合类 | 136篇 |
出版年
2020年 | 13篇 |
2016年 | 15篇 |
2015年 | 19篇 |
2014年 | 15篇 |
2013年 | 63篇 |
2012年 | 87篇 |
2011年 | 88篇 |
2010年 | 36篇 |
2009年 | 38篇 |
2008年 | 82篇 |
2007年 | 88篇 |
2006年 | 80篇 |
2005年 | 84篇 |
2004年 | 71篇 |
2003年 | 43篇 |
2002年 | 52篇 |
2001年 | 46篇 |
2000年 | 40篇 |
1999年 | 21篇 |
1998年 | 30篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 29篇 |
1994年 | 42篇 |
1993年 | 48篇 |
1992年 | 44篇 |
1991年 | 40篇 |
1990年 | 29篇 |
1989年 | 39篇 |
1988年 | 29篇 |
1987年 | 23篇 |
1986年 | 28篇 |
1985年 | 41篇 |
1984年 | 24篇 |
1983年 | 31篇 |
1982年 | 21篇 |
1981年 | 29篇 |
1980年 | 24篇 |
1979年 | 34篇 |
1978年 | 29篇 |
1977年 | 30篇 |
1976年 | 27篇 |
1975年 | 30篇 |
1974年 | 33篇 |
1973年 | 35篇 |
1972年 | 25篇 |
1971年 | 15篇 |
1970年 | 14篇 |
1968年 | 16篇 |
1967年 | 16篇 |
排序方式: 共有1974条查询结果,搜索用时 281 毫秒
101.
Philip L. Wylie Richard J. Phillips Kenneth J. Klein Michael Q. Thompson Bruce W. Hermann 《Journal of separation science》1991,14(10):649-655
An experimental injection port has been designed for split or splitless sample introduction in capillary gas chromatography; the inlet uses electronic pressure control, in order that the column head pressure may be set from the GC keyboard, and the inlet may be used in the constant flow or constant pressure modes. Alternatively, the column head pressure may be programmed up or down during a GC run in a manner analogous to even temperature programming. Using electronic pressure control, a method was developed which used high column head pressures (high column flow rates) at the time of injection, followed by rapid reduction of the pressure to that required for optimum GC separation. In this way, high flow rates could be used at the time of splitless injection to reduce sample discrimination, while lower flow rates could be used for the separation. Using this method, up to 5 μl of a test sample could be injected in the splitless mode with no discrimination; in another experiment, 2.3 times as much sample was introduced into the column by using electronic pressure programming. Some GC peak broadening was observed in the first experiment. 相似文献
102.
Bingham RJ Findlay JB Hsieh SY Kalverda AP Kjellberg A Perazzolo C Phillips SE Seshadri K Trinh CH Turnbull WB Bodenhausen G Homans SW 《Journal of the American Chemical Society》2004,126(6):1675-1681
In the present study we examine the thermodynamics of binding of two related pyrazine-derived ligands to the major urinary protein, MUP-I, using a combination of isothermal titration calorimetry (ITC), X-ray crystallography, and NMR backbone (15)N and methyl side-chain (2)H relaxation measurements. Global thermodynamics data derived from ITC indicate that binding is driven by favorable enthalpic contributions, rather than the classical entropy-driven hydrophobic effect. Unfavorable entropic contributions from the protein backbone and side-chain residues in the vicinity of the binding pocket are partially offset by favorable entropic contributions at adjacent positions, suggesting a "conformational relay" mechanism whereby increased rigidity of residues on ligand binding are accompanied by increased conformational freedom of side chains in adjacent positions. The principal driving force governing ligand affinity and specificity can be attributed to solvent-driven enthalpic effects from desolvation of the protein binding pocket. 相似文献
103.
Nigel M. Groome Elghareeb E. Elboray Dr. Martyn W. Inman Prof. H. Ali Dondas Dr. Roger M. Phillips Colin Kilner Prof. Ronald Grigg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(6):2180-2184
Naturally occurring indole‐3‐carbinol and 3,3‐diindolylmethane show bioactivity in a number of disparate disease areas, including cancer, prompting substantial synthetic analogue activity. We describe a new approach to highly functionalised derivatives that starts from allene gas and proceeds via the combination of a three‐component Pd0‐catalysed cascade with a one‐pot, three‐component carbophilic PtII cascade linked to a stereoselective acid‐catalysed Mannich–Michael reaction that generates complex cyclopropyl diindolylmethanes which show selective activity against prostate cancer cell lines. 相似文献
104.
Efficient stochastic FEM for flow in heterogeneous porous media. Part 1: random Gaussian conductivity coefficients
下载免费PDF全文
![点击此处可从《国际流体数值方法杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper is concerned with the development of efficient iterative methods for solving the linear system of equations arising from stochastic FEMs for single‐phase fluid flow in porous media. It is assumed that the conductivity coefficient varies randomly in space according to some given correlation function and is approximated using a truncated Karhunen–Loève expansion. Distinct discretizations of the deterministic and stochastic spaces are required for implementations of the stochastic FEM. In this paper, the deterministic space is discretized using classical finite elements and the stochastic space using a polynomial chaos expansion. The highly structured linear systems which result from this discretization mean that Krylov subspace iterative solvers are extremely effective. The performance of a range of preconditioned iterative methods is investigated and evaluated in terms of robustness with respect to mesh size and variability of the conductivity coefficient. An efficient symmetric block Gauss–Seidel preconditioner is proposed for problems in which the conductivity coefficient has a large standard deviation.The companion paper, herein, referred to as Part 2, considers the situation in which Gaussian random fields are transformed into lognormal ones by projecting the truncated Karhunen–Loève expansion onto a polynomial chaos basis. This results in a stochastic nonlinear problem because the random fields are represented using polynomial chaos containing terms that are generally nonlinear in the random variables. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
105.
106.
Syntheses of 1b-d is described using 1-chloro-2-deoxy-3,5-di-p-toluoyl-D-erythro-pentosyl chloride. 相似文献
107.
Two efficient syntheses of 3-chloro-7-[(chlorocarbonyl)methoxy]-4-methylcoumarin are described, one utilizing traditional chemistry starting from 3-chloro-7-hydroxy-4-methylcoumarin, while the other uses a novel reagent, sulfuryl chloride/thionyl chloride, in a one-pot reaction starting from 7-(carboxymethoxy)-4-methylcoumarin. 相似文献
108.
J. C. Phillips 《哲学杂志》2013,93(16):1949-1962
Electron-phonon interactions appear to explain some of, but not all, the features of the dispersive kinks in recently observed by angle-resolved photoemission spectroscopy. The remaining anomalies have led to suggestions that magnon, and not phonon, interactions are involved. If one abandons the effective-medium approximation and replaces it with dopant-centred filamentary percolation, a picture emerges that is consistent not only with the photoemission experiments but also with tunnelling, infrared and neutron scattering data. 相似文献
109.
110.