全文获取类型
收费全文 | 6230篇 |
免费 | 118篇 |
专业分类
化学 | 3415篇 |
晶体学 | 31篇 |
力学 | 132篇 |
数学 | 1417篇 |
物理学 | 1353篇 |
出版年
2021年 | 41篇 |
2020年 | 48篇 |
2019年 | 59篇 |
2018年 | 172篇 |
2017年 | 167篇 |
2016年 | 219篇 |
2015年 | 154篇 |
2014年 | 199篇 |
2013年 | 484篇 |
2012年 | 315篇 |
2011年 | 422篇 |
2010年 | 235篇 |
2009年 | 195篇 |
2008年 | 345篇 |
2007年 | 348篇 |
2006年 | 309篇 |
2005年 | 229篇 |
2004年 | 201篇 |
2003年 | 144篇 |
2002年 | 137篇 |
2001年 | 98篇 |
2000年 | 79篇 |
1999年 | 58篇 |
1998年 | 51篇 |
1997年 | 51篇 |
1996年 | 47篇 |
1995年 | 47篇 |
1994年 | 30篇 |
1993年 | 45篇 |
1992年 | 55篇 |
1991年 | 42篇 |
1990年 | 48篇 |
1989年 | 53篇 |
1988年 | 47篇 |
1987年 | 47篇 |
1986年 | 43篇 |
1985年 | 62篇 |
1984年 | 69篇 |
1983年 | 64篇 |
1982年 | 63篇 |
1981年 | 43篇 |
1980年 | 53篇 |
1979年 | 48篇 |
1978年 | 69篇 |
1977年 | 40篇 |
1976年 | 52篇 |
1975年 | 41篇 |
1974年 | 48篇 |
1973年 | 40篇 |
1972年 | 34篇 |
排序方式: 共有6348条查询结果,搜索用时 15 毫秒
1.
N. S. Simonović 《Few-Body Systems》2006,38(2-4):139-145
In agreement with the Kohn theorem the relative motion (rel) of three electrons in a two-dimensional parabolic trap separates
from the centre-of-mass (CM) motion. By introducing new coordinates the Hamiltonian for relative motion in the approximation
of non-interacting electrons can be taken to the normal form. The eigenstates of the normalized Hamiltonian are products of
the Fock-Darwin states for normal modes. The energy levels for relative motion are obtained by diagonalizing the exact Hamiltonian
in the eigenbasis for the non-interacting case. In this basis the interaction matrix elements can be obtained in the analytical
form. Since the rank of the Hamiltonian matrix is significantly reduced, the calculations are faster and more accurate than
those for the full (CM + rel) motion. This advantage is especially important for the calculations of excited states and the
analysis of energy spectra. 相似文献
2.
3.
In this paper a new definition of a lattice valued intuitionistic fuzzy set (LIFS) is introduced, in an attempt to overcome
the disadvantages of earlier definitions. Some properties of this kind of fuzzy sets and their basic operations are given.
The theorem of synthesis is proved: For every two families of subsets of a set satisfying certain conditions, there is an
lattice valued intuitionistic fuzzy set for which these are families of level sets.
The research supported by Serbian Ministry of Science and Technology, Grant No. 1227. 相似文献
4.
S. Mentus Dijana Jelić Veselinka Grudić 《Journal of Thermal Analysis and Calorimetry》2007,90(2):393-397
Thermal decomposition of lanthanum nitrate to lanthanum oxide was carried out by both temperature programmed heating (TPH)
and citrate-gel combustion. The temperature programmed heating was carried out under flow of oxidizing (air), neutral (nitrogen)
and reducing (25 vol.% hydrogen+argone mixture) gases, and the processes were controlled by simultaneous thermogravimetry
and differential thermal analysis. It was shown that hydrogen atmosphere helps to reduce temperatures of all decomposition
steps. The results of TPH were utilized to check the nature of residues in the products of lanthanum nitrate-to-oxide conversion
performed via citrate-gel combustion technique. 相似文献
5.
6.
Solichová D Melichar B Klejna M Jurašková B Královská L Bláha V Zd'ánský P Zadák Z 《Talanta》2003,60(2-3):459-465
Twelve self-sustaining nonagenarians, 10 women and two men, aged 94+/-3 years, and eight institutionalised nonagenarians, eight women, aged 91+/-1 year as well as 11 control subjects, seven women and four men, aged 84+/-5 years entered the study. Urinary neopterin, an indicator of systemic immune activation, and serum thiobarbituric acid reactive substances (TBARS), a marker of lipoperoxidation, were determined initially, and collection of the blood and urine samples was repeated at 3-month interval. Neopterin was measured in the urine specimens by reversed-phase high performance liquid chromatography. A C(18) reversed-phase column 3.3x150 mm, 5 mum-diameter packing Separon SGX was used. Potassium phosphate buffer (15 mmol l(-1), pH 6.4) at flow rate of 0.8 ml min(-1) was used as mobile phase. After centrifugation (5 min, 1300xg) and diluting 100 mul of urine specimens with 1.0 ml of mobile phase containing 2 g of disodium-EDTA per litre, a 20 mul sample was injected on a column. Neopterin was identified by its native fluorescence (353 nm excitation, 438 nm emission). Creatinine was determined by Jaffé kinetic reaction after dilution of sample 1:50 (v/v). The concentration of neopterin in urine was expressed as neopterin/creatinine ratio (mumol mol(-1) creatinine). TBARS were determined spectrofluorometrically using LS-5 spectrofluorimeter (excitation wavelength 528 nm, emission wavelength 558 nm) after extraction with n-butanol treatment with thiobarbituric acid. The significance of differences between nonagenarians and control group was examined by ANOVA-Kruskal-Wallis tests, using statistical software NCSS 6.0.21 (Kaysville, UT, 1996). The decision on significance was based on P=0.05. Urinary neopterin was significantly higher in institutionalised compared to self-sustaining subjects and controls (625+/-565 vs. 203+/-63 mumol mol(-1) creatinine, and 198+/-128 mumol mol(-1) creatinine, respectively, P=0.006). The serum TBARS were higher in both groups of nonagenarians (3.23+/-1.16 mumol l(-1) and 2.69+/-0.39 vs. 2.12+/-0.83 mumol l(-1) for the self-sustaining, institutionalised and controls, respectively, P=0.023). We conclude that the fluorimetric determinations of urinary neopterin and serum TBARS can be useful for the monitoring health status in the elderly patients. 相似文献
7.
8.
Marijana ?aković Zora Popović 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):m507-m509
In the title compound, [Ni(N3)2(C6H6N2O)2], the NiII atom lies on an inversion centre. The distorted octahedral nickel(II) coordination environment contains two planar trans-related N,O-chelating picolinamide ligands in one plane and two monodentate azide ligands perpendicular to this plane. Molecules are linked into a three-dimensional framework by N—H...N hydrogen bonds. 相似文献
9.
Miodrag M. Spalević 《Numerical Algorithms》2007,46(3):253-264
We have recently proposed a very simple numerical method for constructing the averaged Gaussian quadrature formulas. These
formulas exist in many more cases than the real positive Gauss–Kronrod formulas. In this note we try to answer whether the
averaged Gaussian formulas are an adequate alternative to the corresponding Gauss–Kronrod quadrature formulas, to estimate
the remainder term of a Gaussian rule. 相似文献
10.
We consider a four-dimensional generalization of Hess–Appel’rot system and costruct its Lax pair. Both classical and algebro-geometric integration procedure are proceeded. The algebro-geometric integration is based on deep facts from geometry of Prym varieties such as the Mumford relation and Mumford-Dalalyan theory. The integration is similar to the integration of Lagrange bitop which has recetly been performed by the authors. 相似文献