全文获取类型
收费全文 | 635篇 |
免费 | 40篇 |
国内免费 | 3篇 |
专业分类
化学 | 406篇 |
晶体学 | 4篇 |
力学 | 16篇 |
数学 | 138篇 |
物理学 | 114篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 11篇 |
2021年 | 15篇 |
2020年 | 26篇 |
2019年 | 21篇 |
2018年 | 26篇 |
2017年 | 24篇 |
2016年 | 40篇 |
2015年 | 33篇 |
2014年 | 25篇 |
2013年 | 54篇 |
2012年 | 46篇 |
2011年 | 33篇 |
2010年 | 19篇 |
2009年 | 22篇 |
2008年 | 20篇 |
2007年 | 16篇 |
2006年 | 20篇 |
2005年 | 19篇 |
2004年 | 21篇 |
2003年 | 17篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1966年 | 2篇 |
1960年 | 2篇 |
1958年 | 3篇 |
1947年 | 7篇 |
排序方式: 共有678条查询结果,搜索用时 8 毫秒
1.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
2.
We present a new verified optimization method to find regions for Hénon systems where the conditions of chaotic behaviour
hold. The present paper provides a methodology to verify chaos for certain mappings and regions. We discuss first how to check
the set theoretical conditions of a respective theorem in a reliable way by computer programs. Then we introduce optimization
problems that provide a model to locate chaotic regions. We prove the correctness of the underlying checking algorithms and
the optimization model. We have verified an earlier published chaotic region, and we also give new chaotic places located
by the new technique. 相似文献
3.
In bricklayers' model, which is a generalization of the misanthrope processes, we show that a nontrivial class of product distributions is closed under the time-evolution of the process. This class also includes measures fitting to shock data of the limiting PDE. In particular, we show that shocks of this type with discontinuity of size one perform ordinary nearest neighbor random walks only interacting, in an attractive way, via their jump rates. Our results are related to those of Belitsky and Schütz(4) on the simple exclusion process, although we do not use quantum formalism as they do. The structures we find are described from a fixed position. Similar ones were found in Balázs,(2) valak as seen from the random position of the second class particle. 相似文献
4.
Dislocation motion in the real lattice of alloys is highly complex. In a certain temperature range the dynamic strain ageing phenomena have been reported. In this paper the influence of mobile solute atoms (as obstacles) on the motion of dislocation is analysed. Both processes are assumed to be thermally activated. A new model based on this assumption is proposed. The dislocation velocity and the friction stress (due to solute-dislocation interactions) are calculated. A change in the friction stress caused by solute mobility is discussed. 相似文献
5.
In this paper, we study cyclic codes detecting a subclass of close-closed loop bursts viz. low-density close-closed loop bursts. A sub-class of CT close-closed loop bursts called CT low-density close-closed loop bursts is also studied. 相似文献
6.
The conformational space of (4)C(1) alpha- and beta-d-glucuronic acid was scanned by HF/3-21G(p) calculations followed by optimization of the 15 most stable structures for each, using the B3LYP density functional theory method in conjunction with a diffuse polarized valence triple-zeta basis set. We found a general preference of the alpha anomers in the isolated molecules in agreement with the large endo-anomeric hyperconjugation effects in these structures. From the other intramolecular interactions (exo-anomeric hyperconjugation, hydrogen-bonding, dipole-dipole, and steric interactions), the effect of the hydrogen bonding is the most pronounced and plays a major role in determining the stability order within the alpha and beta series. The most stable conformer of both alpha and beta (4)C(1) d-glucuronic acid is the structure with the maximum number (5) of intramolecular hydrogen bonds. Introduction of solvent (water) effects by the SCI-PCM model resulted in two characteristic changes of the energetic properties: the gas-phase stability order changed considerably, and the energy range of the 15 most stable conformers decreased from 30 to 15 kJ/mol. The geometrical parameters reflect well the superimposed effects of hyperconjugation and hydrogen-bonding interactions. Most characteristics are the variations of the C-O bond distances (within a range of 0.04 A) upon the combined intramolecular effects. 相似文献
7.
Fenyvesi Éva Nagai Tsuneji Antal Balázs Zsadon Béla Szejtli József 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(3-4):645-654
Cyclodextrin polymer was compared to other well known disintegrants concerning the swelling properties /water uptake, moisture uptake, hydration capacity, sedimentation volume in water/. Its high disintegrating effect was proved in directly compressed tablets as well as in tablets made by wet granulation. A remarkable improvement in tablet properties was observed. Not only the disintegration of tablets and the dissolution of the drug was accelerated but also the hardness increased when CDP was used as disintegrant. 相似文献
8.
The rapid gas chromatographic detection and determination of ethylene glycol in biological fluids is described. Phenylboronic acid in acetone was used for the esterification of glycol. The phenylboronates of ethylene glycol and 1,2-propylene glycol are not separated on a packed column of medium polarity (OV-17), but they can be separated on a non-polar column (OV-101). In both instances, 1,3-propylene glycol can be used as an internal standard. The method requires only 100 microliters of serum or urine and is suitable for trace analysis in an emergency toxicological laboratory. The utility of the method is demonstrated on two cases of human intoxication with ethylene glycol. 相似文献
9.
P. Baláž K. Tkáčová E. G. Avvakumov 《Journal of Thermal Analysis and Calorimetry》1989,35(5):1325-1330
Experimental results on the influence of preliminary mechanical activation on the thermal decomposition of chalcopyrite are presented and discussed. The following experimental facts were found:
The intensive grinding of chalcopyrite leads to a shift in temperature of the endothermic DTA peak and brings about a decrease in the activation energy of the thermal decomposition of CuFeS2. These results can be attributed to the mechanically produced alterations in structure and surface properties of the mineral. 相似文献
1. | a decrease in the temperature of the endothermic DTA peak of-CuFeS2 from 821 K for a non-activated sample to 763 K for an optimally activated one; |
2. | a decrease in the apparent activation energy of the thermal decomposition of CuFeS2 from 238 kJ mol–1 for a non-activated sample to 72 kJ mol–1 for an optimally activated sample. |
10.