全文获取类型
收费全文 | 440篇 |
免费 | 9篇 |
专业分类
化学 | 386篇 |
晶体学 | 4篇 |
力学 | 3篇 |
数学 | 15篇 |
物理学 | 41篇 |
出版年
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 32篇 |
2012年 | 17篇 |
2011年 | 15篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 22篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 26篇 |
2004年 | 23篇 |
2003年 | 18篇 |
2002年 | 21篇 |
2001年 | 11篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1976年 | 7篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1968年 | 3篇 |
1960年 | 2篇 |
1937年 | 1篇 |
排序方式: 共有449条查询结果,搜索用时 15 毫秒
71.
Thermal dehydration and decomposition processes of a Pd(II) coordination compound, [PdL4]Cl2·3H2O ( 1 ), (where L is 1‐allylimidazole) were studied by simultaneous TG/DSC techniques under constant heating rates condition. The released gas products were analyzed by online coupling a FTIR spectrometer to the TG equipment. The so obtained evolved gas analysis confirmed that only two ligand molecules were released and that a new 1‐allylimidazole Pd(II) complex, trans‐[PdL2Cl2] ( 2a ), was obtained. The same coordination compound was also prepared by heating 1 at 413.15 K in air atmosphere until a constant weight was reached 2b . Thermal decomposition mechanisms for the 2a and 2b complexes examined were proposed according to the three mass loss steps derived by TG data. Based on the model‐free isoconversional method described by Flynn–Wall–Ozawa (FWO), the dependencies of activation energy on the degree of conversion were determined. A model‐free “single point” method was also applied using the Kissinger equation, and derived results were compared to those of the former method. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 667–674, 2005 相似文献
72.
Janusz Dabrowski Krystyna Kamieska-Trela Lech Kozerski 《Magnetic resonance in chemistry : MRC》1974,6(9):499-502
Carbon-13 magnetic resonance spectra of the s-cis and s-trans rotamers of enamino ketones and thiones of the general formula \documentclass{article}\pagestyle{empty}\begin{document}${\rm X =}\mathop {\rm C}\limits^{\rm 1} {\rm (}\mathop {\rm R}\limits^{\rm 1} {\rm)}\mathop {\rm C}\limits^{\rm 2} {\rm H =}\mathop {\rm C}\limits^{\rm 3} {\rm HN}\mathop {{\rm R}_{\rm 2}}\limits^{\rm 4}$\end{document} (where × = O or S and R-1, R-4 = alkyl) have been obtained. With dimethylaminoacrolein and its thione analogue, restricted rotation could only be observed in the latter. The chemical shift differences between rotamers and homologues are attributed to changes in conjugation and to induced bond polarisation, both these factors resulting from steric strain. In particular, nonplanar deformations of the s-trans rotamers are deduced from their C-2 chemical shift values. 相似文献
73.
Krystyna Parczyk 《Reports on Mathematical Physics》1985,22(1):63-70
It is shown that the Pinster partition of the generalized Lorentz gas is given by the relation (Q,X)∽(Q′, X′) iff Q=Q′, where Q, Q′ are configurations of discs and X, X′ are sets of infinitely many particles. 相似文献
74.
The reactions are reported between selenite and 1,2-dimercaptoethane (DME) or thioacetic acid (TAA) to form moderately stable derivatives having an enhanced absorptions in the 230–360 nm region in combining molar ratios 3:2 and 4:1, respectively. Both reactions invariably yield one product corresponding to the selenium-containing derivative of DME or TAA. The formation of products is a pH dependent process. The equilibrium constants of reactions between selenite and DME or TAA were measured. 相似文献
75.
By an f-graph we mean an unlabeled graph having no vertex of degree greater than f. Let D(n, f) denote the digraph whose node set is the set of f-graphs of order n and such that there is an arc from the node corresponding to graph H to the node corresponding to the graph K if and only if K is obtainable from H by the addition of a single edge. In earlier work, algorithms were developed which produce exact results about the structure of D(n, f), nevertheless many open problems remain. For example, the computation of the order and size of D(n, f) for a number of values of n and f have been obtained. Formulas for the order and size for f = 2 have also been derived. However, no closed form formulas have been determined for the order and size of D(n, f) for any value of f. Here we focus on questions concerning the degrees of the nodes in D(n,n − 1) and comment on related questions for D(n,f) for 2 f < n − 1. 相似文献
76.
Summary A new chelate-forming resin was prepared from common anionexchanger Amberlyst A-26 and thoron. Thoron-loaded resin is stable and resistant to mineral acids. To differentiate the selectivity of thoron-loaded resin trien as competitive reagent was used. In the presence of trien thoron-loaded resin is almost selective for Fe(III) as a counter ion. The application of the resin to the analysis of iron in brass and the preconcentration and determination of iron in natural waters was described. 相似文献
77.
78.
79.
Janusz Dbrowski Krystyna Kamieska-trela Andrzej J. Sadlej 《Magnetic resonance in chemistry : MRC》1971,3(5):589-594
The 14N chemical shifts were measured for a series of quaternary ammonium salts of enamino ketones. An upfield shift of the 14N resonance signals upon quaternization has been observed. The interpretation in terms of the approximate theory of nuclear magnetic shielding is given. The calculations for some model systems result in a general agreement with the experimental data. 相似文献
80.
Lidia Prajer-Janczewska Anna Postawka Krystyna Koćma Krystyna Rudolf 《Monatshefte für Chemie / Chemical Monthly》1968,99(3):1175-1176
Ohne ZusammenfassungMit 1 Abbildung 相似文献