全文获取类型
收费全文 | 306篇 |
免费 | 6篇 |
国内免费 | 3篇 |
专业分类
化学 | 196篇 |
晶体学 | 4篇 |
力学 | 6篇 |
数学 | 38篇 |
物理学 | 71篇 |
出版年
2019年 | 2篇 |
2015年 | 2篇 |
2014年 | 6篇 |
2013年 | 20篇 |
2012年 | 15篇 |
2011年 | 24篇 |
2010年 | 7篇 |
2009年 | 6篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 20篇 |
2005年 | 16篇 |
2004年 | 10篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1991年 | 3篇 |
1987年 | 6篇 |
1985年 | 2篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1970年 | 3篇 |
1969年 | 6篇 |
1968年 | 2篇 |
1967年 | 4篇 |
1966年 | 2篇 |
1941年 | 2篇 |
1938年 | 2篇 |
1893年 | 2篇 |
1881年 | 1篇 |
1880年 | 1篇 |
排序方式: 共有315条查询结果,搜索用时 0 毫秒
11.
Williams DH Davies NL Koivisto JJ 《Journal of the American Chemical Society》2004,126(43):14267-14272
Two models (A and B) have been proposed to account for decreased downfield chemical shifts of a proton bound by noncovalent interactions at a ligand/antibiotic interface as the number of ligand/antibiotic interactions is decreased. In model A, the proton involved in the noncovalent bond suffers a smaller downfield shift because the bond is, with a relatively large probability, broken, and not because it is longer. In model B, the proton involved in the noncovalent bond suffers a smaller downfield shift because the bond is longer, and not because it is, with a relatively large probability, broken. We show that model A cannot account for the chemical shift changes. Model B accounts for the process of positively cooperative binding, in which noncovalent bonds are reduced in length and thereby increase the stability of the organized state. 相似文献
12.
Taatjes CA Welz O Eskola AJ Savee JD Osborn DL Lee EP Dyke JM Mok DW Shallcross DE Percival CJ 《Physical chemistry chemical physics : PCCP》2012,14(30):10391-10400
Criegee biradicals, i.e., carbonyl oxides, are critical intermediates in ozonolysis and have been implicated in autoignition chemistry and other hydrocarbon oxidation systems, but until recently the direct measurement of their gas-phase kinetics has not been feasible. Indirect determinations of Criegee intermediate kinetics often rely on the introduction of a scavenger molecule into an ozonolysis system and analysis of the effects of the scavenger on yields of products associated with Criegee intermediate reactions. Carbonyl species, in particular hexafluoroacetone (CF(3)COCF(3)), have often been used as scavengers. In this work, the reactions of the simplest Criegee intermediate, CH(2)OO (formaldehyde oxide), with three carbonyl species have been measured by laser photolysis/tunable synchrotron photoionization mass spectrometry. Diiodomethane photolysis produces CH(2)I radicals, which react with O(2) to yield CH(2)OO + I. The formaldehyde oxide is reacted with a large excess of a carbonyl reactant and both the disappearance of CH(2)OO and the formation of reaction products are monitored. The rate coefficient for CH(2)OO + hexafluoroacetone is k(1) = (3.0 ± 0.3) × 10(-11) cm(3) molecule(-1) s(-1), supporting the use of hexafluoroacetone as a Criegee-intermediate scavenger. The reactions with acetaldehyde, k(2) = (9.5 ± 0.7) × 10(-13) cm(3) molecule(-1) s(-1), and with acetone, k(3) = (2.3 ± 0.3) × 10(-13) cm(3) molecule(-1) s(-1), are substantially slower. Secondary ozonides and products of ozonide isomerization are observed from the reactions of CH(2)OO with acetone and hexafluoroacetone. Their photoionization spectra are interpreted with the aid of quantum-chemical and Franck-Condon-factor calculations. No secondary ozonide was observable in the reaction of CH(2)OO with acetaldehyde, but acetic acid was identified as a product under the conditions used (4 Torr and 293 K). 相似文献
13.
Mann DL Ware GM Bonnin E Eitenmiller RR Barna E Christiansen S De Borde JL DeVries J Gilliland P Hemmer J Kalman A Konings E Levin D Salvati L Woollard D 《Journal of AOAC International》2005,88(1):30-37
A liquid chromatographic (LC) method was validated for the determination of total vitamin B6 in infant formula. Total vitamin B6 was quantified by converting the phosphorylated and free vitamers into pyridoxine. Pyridoxine was determined by ion pair reversed-phase LC with fluorescence detection. The method was subjected to an AOAC collaborative study involving a factory-manufactured, milk- and soy-based infant formula. Each was spiked at 3 concentrations in the range of 0-1 microg/g and sent as blind duplicate to participant laboratories. Nine laboratories returned valid data which were statistically analyzed for outliers and precision parameters. The repeatability relative standard deviation (RSD(r)) ranges were 2.0-4.0 and 3.5-5.9% for fortified milk- and soy-based formulas, respectively. The reproducibility relative standard deviation (RSD(R)) ranges were 8.2-8.4 and 6.7-11.2% for fortified milk- and soy-based formulas, respectively. HORRAT values ranged from 0.42 to 0.53, indicating that the precision of the method is acceptable. The mean RSD(r):RSD(R) values were 0.60 and 0.55 for milk- and soy-based formulas, respectively. As expected, RSDs for the unfortified samples were higher, but their HORRAT values (0.81 and 2.06) helped define a realistic limit of quantitation as 0.05 microg/g. Recovery data were quantitative and varied between 81.4 and 98.0% (mean = 89.8%) for each of 6 spiked materials. 相似文献
14.
15.
The mode of action of the secondary metabolite chlorofusin, which antagonises the interaction between p53 and MDM2, involves direct binding to the N-terminal domain of MDM2. 相似文献
16.
17.
18.
Evans Betty S. Dudley Connie A. Klasson K. Thomas 《Applied biochemistry and biotechnology》1996,57(1):885-894
Applied Biochemistry and Biotechnology - Many industrial locations have identified the need for treatment of polychlorinated biphenyl (PCB) wastes and remediation of PCB-contaminated sites.... 相似文献
19.
Dudley R. Herschbach 《International journal of quantum chemistry》1996,57(3):295-308
Chief features of dimensional scaling methods are exemplified by briefly reviewing prototypical applications and recent developments. The pseudoclassical large-D limit usually can be evaluated exactly regardless of the magnitude, nature, and number of strong, nonseparable dynamical interactions. Often, this limit can be accurately linked to D = 3 by perturbation or interpolation methods. This is because the dimension dependence of many-body effects tends to be smooth and mild when calibrated by appropriate one- or few-body problems. A simple renormalization procedure applied to atoms with up N ∼ 100 electrons yields a major part of the correlation energy. From Hartree-Fock input, a renormalized nuclear charge is determined which renders the dimensionally scaled energy at D → ∞ a good approximation to that for D = 3 with the actual Z. Prospects are discussed for other means to exploit dimensional scaling, including an analogous renormalization procedure for molecules. © 1996 John Wiley & Sons, Inc. 相似文献
20.
Dudley Paul Johnson 《Journal of Theoretical Probability》1989,2(4):433-436
We show that under suitable conditions $$\begin{gathered} E_x f\left\{ {a + \int_0^t \beta \left[ {b + \int_0^s {\alpha \left( {X_r } \right)dr, c + s, X_s } } \right]ds, b + \int_0^t {\alpha \left( {X_s } \right)ds, c + t, X_t } } \right\} \hfill \\ = e^{tG} f\left[ {a, b, c, x} \right] \hfill \\ \end{gathered} $$ whereX t is a Brownian motion andG is the generator of a (C 0) contraction semigroupe tG. 相似文献