全文获取类型
收费全文 | 849篇 |
免费 | 18篇 |
国内免费 | 5篇 |
专业分类
化学 | 384篇 |
晶体学 | 7篇 |
力学 | 41篇 |
数学 | 239篇 |
物理学 | 201篇 |
出版年
2022年 | 10篇 |
2021年 | 25篇 |
2020年 | 28篇 |
2019年 | 19篇 |
2018年 | 18篇 |
2017年 | 24篇 |
2016年 | 26篇 |
2015年 | 21篇 |
2014年 | 38篇 |
2013年 | 69篇 |
2012年 | 49篇 |
2011年 | 46篇 |
2010年 | 49篇 |
2009年 | 38篇 |
2008年 | 51篇 |
2007年 | 31篇 |
2006年 | 44篇 |
2005年 | 31篇 |
2004年 | 26篇 |
2003年 | 25篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1990年 | 6篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 11篇 |
1975年 | 4篇 |
1974年 | 9篇 |
1973年 | 5篇 |
1972年 | 8篇 |
1971年 | 6篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 5篇 |
1967年 | 3篇 |
1961年 | 3篇 |
排序方式: 共有872条查询结果,搜索用时 15 毫秒
1.
Kerstin Paech Adrian Dumitru Jürgen Schaffner-Bielich Stefan Schramm Horst Stöcker Gebhard Zeeb Detlef Zschiesche 《Acta Physica Hungarica A》2004,21(2-4):151-156
The measured particle ratios in central heavy-ion collisions are investigated within a chemical and thermal equilibrium chiral SU(3) σ?ω approach. Contrary to the commonly adopted non-interacting gas calculations, the chiral SU(3) model predicts modified effective hadron masses and effective chemical potentials in the medium and a transition to a chirally restored phase at high temperatures or chemical potentials. the influence of three different types of phase transitions is investigated. We show that the deduced freeze-out values considerably depend on the underlying model while the quality of the fit is approximately the same. 相似文献
2.
A new theory of transverse susceptibility (TS) based on magnetization vector dynamics, as described by the Landau–Lifshitz equation of motion, is given. It is shown that the traditional TS experiment is, in fact, the zero-frequency limit of the ferromagnetic resonance (FMR). The importance of these results resides in the generality of the approach which allows one to find the TS for virtually any magnetic system if an expression for the magnetic free-energy density is known. Moreover, the effect of the frequency of excitatory AC field on the TS experiments and the effect of energy dissipation through the imaginary part of TS emerge coherently from the new TS model. 相似文献
3.
3-Methyl-5-oxo-1-phenyl-2-pyrazolin-4-ylazo-2'-(6',8'-naphthalenedisulfonic acid) (disodium salt) is proposed as a new reagent for the gravimetric determination of zirconium. The precipitate formed at pH 1–1.5 can be weighed directly and there are few interferences. 相似文献
4.
M. Ştefănescu M. Stoia O. Ştefănescu A. Popa M. Simon C. Ionescu 《Journal of Thermal Analysis and Calorimetry》2007,88(1):19-26
Hybrid organic-inorganic materials,
silica – polyols (ethylene-glycol – EG; 1,2 propane diol –
1,2PG; 1,3 propane diol – 1,3PG and glycerol – GL), were prepared
by a sol-gel process starting from tetraethylorthosilicate (TEOS) and polyols,
in acid catalysis. The resulting materials were studied by thermal analysis
(in air and nitrogen), FTIR and solid state 29Si-NMR
spectroscopy. These techniques evidenced the presence of polyols in the silica
matrix both hydrogen bounded and chemically bounded in the silica network.
The thermal analysis proves to be the most appropriate technique to evidence
the organic chains linked in the matrix network and to follow the thermal
evolution of the gels to the SiO2 matrix. 相似文献
5.
It is shown that on the superacid cyclization of esters of bishomobicyclogeranylgeranic and E,E-bishomofarnesic acids fully cyclized hydroxyesters are formed in good yield, while on the interaction of esters of 6-hydroxy- and 6-acyloxy-15-bishomobicyclogeranylgeranic acids with a superacid no carbocyclization takes place. 相似文献
6.
7.
Dumitru Ivascu Gabriel Burstein 《Journal of Mathematical Analysis and Applications》1985,106(1):171-179
Some results are given on the homology groups of the abstract simplicial complex associated to a multivariable control system, as an extension of the central result of J. Casti (J. Math. Anal. Appl.68 (1979), 347–370) to the multivariable case. The method used is “polyhedral dynamics” as termed by J. Casti, who introduced it. A given control system is mapped into a simplicial complex and then its homological structure is studied. These results, obtained in the multivariable case by the use of the Mayer-Vietoris homology sequence and of the relative homology sequence, present topological invariants for control systems thus creating the possibility of a new topological classification of multivariable systems. An example is given to clarify the approach. 相似文献
8.
Continuous 1-dimensional wavelet transform (WT) was applied to the quantitative analysis of a vitamin combination of thiamine hydrochloride (THI) and pyridoxine hydrochloride (PYR) with strongly overlapping signals. Absorbance data from the UV-Vis absorption spectrum of width 1150 were subjected to Gauss1 and Gauss2 WTs. Because of its flexibility, data processing, and its high signal amplitude, the continuous WT method is a powerful tool for analysis of multicomponent mixtures. By measuring the amplitude signals corresponding to the selected zero-crossing points of the transformed signal, we obtained the calibration curve. The validation of the calibration graphs was confirmed with different mixtures of THI and PYR at various concentration ratios. A brief explanation of the continuous wavelet method is given. MATLAB 6.5 software was used to perform the calculations. The results of our study were compared with those obtained by spectroscopic, chemometric, and liquid chromatographic methods, and good agreement was found. 相似文献
9.
In this study the influence of the experimental conditions on the obtention of polyelectrolyte multilayer capsules was investigated. Two ways of the simple coacervation method was used to obtain spherical capsules involving chitosan and hyaluronan, chitosan being inside the particle covered by a hyaluronan layer to increase the biocompatibility. The 1H-NMR spectroscopy confirmed a polyelectrolyte complex formation and the optical microscopy shows that the complexed capsules have good sphericity with average diameters ranging from 590 at 1550 μm in the experimental conditions adopted. One can observe that in the acid medium the complexed capsules are much stable than the chitosan beads. The structures described provide a starting point for the design and fabrication of complexed capsules made of two biocompatible natural polymers with potential applicability in medical or pharmaceutical applications. Few diffusion experiments demonstrated that the complexed layer controls the diffusion of dextran included in the chitosan inner domain. 相似文献
10.
D. Humelnicu G. Drochioiu K. Popa 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):291-293
The efficiency of the yeast suspension ofSaccharomyces cerevisiae was studied in the decontamination of radioactive residual waste waters and in the biological behavior of the levuric mass.
The effect of reaction time on the amino acid content in the supernatant and on the concentration of radioactive ions was
also investigated. The reaction of yeast with the toxic agent showed that the living matter behaves differently from the chemical
components of the cell. The yeast had the tendency to aggregate in the presence of radioactive ions.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献