全文获取类型
收费全文 | 839篇 |
免费 | 46篇 |
国内免费 | 26篇 |
专业分类
化学 | 481篇 |
晶体学 | 21篇 |
力学 | 42篇 |
综合类 | 1篇 |
数学 | 161篇 |
物理学 | 205篇 |
出版年
2023年 | 11篇 |
2022年 | 8篇 |
2021年 | 8篇 |
2020年 | 16篇 |
2019年 | 19篇 |
2018年 | 24篇 |
2017年 | 33篇 |
2016年 | 36篇 |
2015年 | 26篇 |
2014年 | 45篇 |
2013年 | 80篇 |
2012年 | 77篇 |
2011年 | 58篇 |
2010年 | 49篇 |
2009年 | 34篇 |
2008年 | 40篇 |
2007年 | 43篇 |
2006年 | 42篇 |
2005年 | 32篇 |
2004年 | 35篇 |
2003年 | 22篇 |
2002年 | 19篇 |
2001年 | 5篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 10篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1968年 | 1篇 |
1937年 | 2篇 |
排序方式: 共有911条查询结果,搜索用时 31 毫秒
91.
92.
Salvatori Mdel R Abou-Jneid R Ghoulami S Martin MT Zaparucha A Al-Mourabit A 《The Journal of organic chemistry》2005,70(20):8208-8211
[Chemical reaction: see text] Various substituted 2-aminotetrahydroazolopyridines and 2-aminohexahydroazolopyridines have been prepared by bromine-mediated addition of protected guanidine or urea to hydropyridine derivatives. The pH-dependent regioselective cleavage of the resulting aminal function led to the 2-aminoazole products III. The yields of the bicycles of type II, and their conversion into azoles III depends on the electronic properties of the substituents on the nitrogen of the tetrahydopyridine. 相似文献
93.
94.
The order parameter fluctuation spectrum in an isotopically disordered KH2PO4 type crystal has been evaluated as a function of the deuterium content using Mori's continued fraction representation. In contrast to a pure system we have now two narrow central peaks and two overdamped soft modes. The results show that the static central peak observed by light scattering in paraelectric KH2PO4 cannot be produced by naturally abundant deuterium. 相似文献
95.
In Geoffroy et al, Acceleration of convergence in Dontchev's iterative method for solving variational inclusions Serdica Math. J. 29 (2003), pp. 45–54] we showed the convergence of a cubic method for solving generalized equations of the form 0 ∈ f(x) +- G(x) where f is a function and G stands for a set-valued map. We investigate here the stability of such a method with respect to some perturbations. More precisely, we consider the perturbed equation y ∈ f(x) +- G(x) and we show that the pseudo-Lipschitzness of the map (f +- G)−1 is closely tied to the uniformity of our method in the sense that the attraction region does not depend on small perturbations of the parameter y. Finally, we provide an enhanced version of the convergence theorem established by Geoffroy, et al. 相似文献
96.
Liu SP Sa C Hu XL Kong L 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(4):817-822
In near neutral to weak basic media, sodium carboxymethyl cellulose (NaCMC) will dissociate to become a macro polymeric anion, which can react with acridine yellow (AY) or acridine orange (AO) to form an ion-association complex resulting in fluorescence quenching of the acridine dyes. The maximum fluorescence quenching wavelength is 505 nm (lambda(ex)=440 nm) for AY system and 530 nm (lambda(ex)=493 nm) for AO system, respectively. The fluorescence quenching values (DeltaF) are directly proportional to the concentrations of NaCMC and the linear ranges are 20.0-4000 microg/L for AY system and 20.0-7000 microg/L for AO system, separately. This method has high sensitivity and the detection limits for NaCMC are 58.0 microg/L (AY system) and 157.2 microg/L (AO system). The effects of coexistent substance have been investigated, and the results show that this method has a relatively good selectivity. A fluorescence quenching method for the determination of NaCMC based on the ion-association reactions of CMC polymeric anion with a basic acridine dye was developed. The method is sensitive, simple and fast. 相似文献
97.
Summary For P∈ F2[z] with P(0)=1 and deg(P)≧ 1, let A =A(P) be the unique subset of N (cf. [9]) such that Σn≧0 p(A,n)zn ≡ P(z) mod 2, where p(A,n) is the number of partitions of n with parts in A. To determine the elements of the set A, it is important to consider the sequence σ(A,n) = Σ d|n, d∈A d, namely, the periodicity of the sequences (σ(A,2kn) mod 2k+1)n≧1 for all k ≧ 0 which was proved in [3]. In this paper, the values of such sequences will be given in terms of orbits. Moreover, a formula
to σ(A,2kn) mod 2k+1 will be established, from which it will be shown that the weight σ(A1,2kzi) mod 2k+1 on the orbit <InlineEquation ID=IE"1"><EquationSource Format="TEX"><![CDATA[<InlineEquation ID=IE"2"><EquationSource Format="TEX"><![CDATA[$]]></EquationSource></InlineEquation>]]></EquationSource></InlineEquation>z_i$
is moved on some other orbit zj when A1 is replaced by A2 with A1= A(P1) and A2= A(P2) P1 and P2 being irreducible in F2[z] of the same odd order. 相似文献
98.
99.
In this paper, we obtain a new abstract formula relating eigenvalues of a self-adjoint operator to two families of symmetric and skew-symmetric operators and their commutators. This formula generalizes earlier ones obtained by Harrell, Stubbe, Hook, Ashbaugh, Hermi, Levitin and Parnovski. We also show how one can use this abstract formulation both for giving different and simpler proofs for all the known results obtained for the eigenvalues of a power of the Laplace operator (i.e. the Dirichlet Laplacian, the clamped plate problem for the bilaplacian and more generally for the polyharmonic problem on a bounded Euclidean domain) and to obtain new ones. In a last paragraph, we derive new bounds for eigenvalues of any power of the Kohn Laplacian on the Heisenberg group. 相似文献
100.
We provide a semilocal convergence analysis for Newton-like methods of ??bounded deterioration?? in a Banach space setting. We establish tighter error bounds on the distances involved, and a more precise information on the location of the solution, under the same or weaker hypotheses than before (Argyros, Acta Math. Sin. (Engl. Ser.), 23:2087?C2096, 2007; Deuflhard, Newton methods for nonlinear problems. Affine invariance and adaptive algorithms, Springer Series in Computational Mathematics, vol. 35. Springer, Berlin, 2004; Ezquerro and Hern??ndez, IMA J. Numer. Anal., 22:187?C205, 2002) using recurrent functions. Numerical examples are also provided involving polynomial, integral, and differential equations. 相似文献