全文获取类型
收费全文 | 197篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 134篇 |
晶体学 | 3篇 |
力学 | 5篇 |
数学 | 39篇 |
物理学 | 23篇 |
出版年
2020年 | 1篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2011年 | 7篇 |
2010年 | 9篇 |
2009年 | 3篇 |
2008年 | 18篇 |
2007年 | 10篇 |
2006年 | 7篇 |
2005年 | 14篇 |
2004年 | 12篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有204条查询结果,搜索用时 347 毫秒
31.
Let be the injective tensor product of the separable Banach spaces X and Y and let SX, SY and be the unit spheres of these spaces. The tensor product of two symmetric finite measures η1 on SX and η2 on SY, η1?η2, is defined in a natural way as a measure on . It is shown that η1? η2 is the spectral measure of a p-stable random variable W on , 0 <p < 2, if and only if η1 and η2 are the spectral measures of p-stable random variables U and V on X and Y, respectively. Actually upper and lower bounds for in terms of the random variables U and V are obtained. When X = C(S), Y = C(T) with S, T compact metric spaces, and η1, and η2 are discrete, our results imply that if θi, θij are i.i.d. standard symmetric real valued p-stable random variables, 0 < p <2, xi?C(S), and yi?C(T), then the series ∑ijθijxi(s) yj(t) converges uniformly a.s. iff the series ∑iθixi(s) and ∑iθiyi(t) both converge uniformly a.s. When p = 2 this follows from Chevet's theorem on Gaussian processes. Several examples are given. One of them requires an interesting upper bound on the probability distribution of the maximum of i.i.d. p-stable random variables taking values in a general Banach space. 相似文献
32.
A class
of measurable functions on a probability space is called a Glivenko-Cantelli class if the empirical measuresP
n
converge to the trueP uniformly over
almost surely.
is a universal Glivenko-Cantelli class if it is a Glivenko-Cantelli Cantelli class for all lawsP on a measurable space, and a uniform Glivenko-Cantelli class if the convergence is also uniform inP. We give general sufficient conditions for the Glivenko-Cantelli and universal Glivenko-Cantelli properties and examples to show that some stronger conditions are not necessary. The uniform Glivenko-Cantelli property is characterized, under measurability assumptions, by an entropy condition. 相似文献
33.
Shyh‐Ying Chiou Gin‐Win Lai Yi‐Hon Tsai Yu‐Ru Lee Long‐Yau Lin Gia‐Lih Lin 《中国化学会会志》2005,52(4):843-848
The goal of this work is to determine enzyme kinetics and mechanisms of acetylcholinesterase and butyrylcholinesterase inhibition by five cardiovascular drugs, lovastatin, simvastatin, amlodipine besylate, nifedipine, and hydralazine hydrochloride, and two benzodiazepines, diazepam and chlordiazepoxide hydrochloride. All drugs in this study are reversible mixed‐type inhibitors of acetylcholinesterase and butyrylcholinesterase. The pKi values for acetylcholinesterase and butyrylcholinesterase inhibition by the cardiovascular drugs are linearly correlated with the molecular weights of the drugs with the slopes of 0.005 and 0.0021, respectively. Therefore, van der Waals' interactions between acetylcholinesterase and the cardiovascular drugs are stronger than those between butyrylcholinesterase and the drugs. This is probably due to a smaller active site gorge and a more significant peripheral anionic substrate binding site of acetylcholinesterase than those of butyrylcholinesterase. The fact that the pKi values for both butyrylcholinesterase and acetylcholinesterase inhibition by the cardiovascular drugs are linearly correlated with each other suggests that both enzyme inhibition reactions proceed via a common mechanism. Furthermore, amlodipine besylate may be useful in Alzheimer's disease treatment similar to donepezil. 相似文献
34.
Di Bussolo V Liu J Huffman Jr Gin DY 《Angewandte Chemie (International ed. in English)》2000,39(1):204-207
Nitrogen transfer to glycals: A new method for direct C2-aza-glycosylation with glycal donors has been developed (see scheme), employing the new reagent combination of thianthrene-S-oxide and trifluoroacetic anhydride for glycal activation, in an overall one-pot procedure. 相似文献
35.
Core replacement energies are calculated for nitrogen and oxygen in various gaseous cations from accurate core binding energies and thermodynamic data. The values for a given element differ in some cases by much more than the experimental errors. These chemical shifts in core replacement energy can be rationalized by recognizing that they are equal to the shifts in the energy of transfering an electron from a core level to a nucleus. As expected, relatively endothermic core replacement energies are found for atoms which have a high density of nonbonding valence s electrons. 相似文献
36.
The proposed technique for hydrodynamic injection is based on commutation in a simple flow-injection system with only one peristaltic pump. Precise results (usually r.s.d. < 1%) are attained even when injected volumes are small (1–10 μl). Dead-volume effects are associated with the mechanical flexibility of the system and with diffusion; differences between effective sample size and the dimensions of the injection duct are emphasized, particularly for small volumes. The proposed technique is checked for a spectrophotometric model system and confirmed by the atomic absorption spectrometry of chromium in steels. With a sampling rate of 120 h?1, the precision is better than 99% for chromium contents in the 0.0–30.0% (w/w) range. The results agree well with those obtained by i.c.p./a/e/s. and conventional a.a.s. 相似文献
37.
[reaction: see text] The synthesis of a selectively protected form of the bicyclic guanidine fragment of batzelladine A from L-aspartic acid is reported, thereby establishing the absolute configuration of the bicyclic guanidine ring system within the natural product. 相似文献
38.
Water samples with variable salinity are analysed by a flow-injection—inductively coupled plasma (ICP) system. The sampling zone approach is used to level the sample and standard saline contents in order to compensate for matrix effects. Calibration graphs for Ca, Mg, Al, Fe, P and Si at three different sodium concentrations are obtained. The sample and standard salinity matching is done automatically by processing the sample sodium signal from the ICP with a microcomputer and adding a suitable amount of sodium. The decision process consists in choosing the appropriate standard solution and adjusting the commutation delay for the sampling zone, using a previously determined time—concentration curve. Sodium interference is minimized, allowing the analysis of water samples with a saline matrix up to 2.5% (w/v) NaCl. The proposed method is suitable for 60 samples h?1. 相似文献
39.
M. J. Arias P. Muñoz J. R. Moyano J. M. Ginés Cs. Novák 《Journal of Thermal Analysis and Calorimetry》1998,51(3):973-980
Techniques of DSC, TG/DTG, EGD and HSM were used to study and characterize the complex formation and state of dispersion after co-grinding of a 1:1 mixture of omeprazole (OME) and γ-cyclodextrin (γ-CD) under various conditions. The changed crystalline properties of the composites obtained by co-grinding suggested distinct types of interactions between the components, as a consequence of the variations in the grinding procedure. The experimental data clearly revealed that a true solid complex OME-γ-CD was obtained only by wetting the mixture of the components with phosphate buffer during the co-grinding. Other co-grinding procedures yielded only amorphous drug—CD mixtures or their combination with partial complexation. 相似文献
40.
J. M. Ginés M. J. Arias C. Novák P. J. Sánchez-Soto A. Ruiz-Conde E. Morillo 《Journal of Thermal Analysis and Calorimetry》1995,45(4):659-666
The formation of crystalline inclusion complex of triamterene with β-cyclodextrin (β-CD) was studied, evaluating the thermal behaviour and dispersion state of this drug in different types of binary systems. Spray-drying and co-grinding (oscillating mill) mixtures of triameterene with β-CD were prepared in 1∶1 molar ratio. The changes of crystalline properties of original (untreated) triamterene, β-CD, and composites obtained by co-grinding and spray-drying were investigated in comparison with those produced in simple physical mixtures. The thermal behaviour of the different samples was investigated using DTA. X-ray diffraction was applied as a complementary technique. The results have been explained by formation of amorphous drug particles on spray-drying samples and co-grinding or alternatively by means of a solid dispersion formation or a combination of these two. A contamination effect by grinding media was also observed as increasing grinding time. 相似文献