全文获取类型
收费全文 | 5539篇 |
免费 | 351篇 |
国内免费 | 101篇 |
专业分类
化学 | 820篇 |
晶体学 | 33篇 |
力学 | 146篇 |
综合类 | 84篇 |
数学 | 1118篇 |
物理学 | 1325篇 |
无线电 | 2465篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 31篇 |
2021年 | 104篇 |
2020年 | 114篇 |
2019年 | 30篇 |
2018年 | 37篇 |
2017年 | 109篇 |
2016年 | 139篇 |
2015年 | 157篇 |
2014年 | 259篇 |
2013年 | 314篇 |
2012年 | 255篇 |
2011年 | 386篇 |
2010年 | 352篇 |
2009年 | 365篇 |
2008年 | 409篇 |
2007年 | 394篇 |
2006年 | 349篇 |
2005年 | 273篇 |
2004年 | 253篇 |
2003年 | 263篇 |
2002年 | 218篇 |
2001年 | 182篇 |
2000年 | 160篇 |
1999年 | 107篇 |
1998年 | 124篇 |
1997年 | 102篇 |
1996年 | 110篇 |
1995年 | 74篇 |
1994年 | 72篇 |
1993年 | 44篇 |
1992年 | 26篇 |
1991年 | 28篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 18篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1976年 | 4篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有5991条查询结果,搜索用时 15 毫秒
781.
Let D be a directed graph; the (l,ω)-Independence Number of graph D, denoted by αl,ω(D), is an important performance parameter for interconnection networks. De Bruijn networks and Kautz networks, denoted by B(d,n) and K(d,n) respectively, are versatile and efficient topological structures of interconnection networks. For l=1,2,…,n, this paper shows that αl,d−1(B(d,n))=dn,αl,d−1(K(d,n))=αl,d(K(d,n))=dn+dn−1 if d≥3 and n≤d−2. In particular, the paper shows the exact value of the Independence Number for B(d,1) and B(d,2) for any d. For the generalized situation, the paper obtains a lower bound αl,d−1(B(d,n))≥d2 if n≥3 and d≥5. 相似文献
782.
783.
In this paper, a new monotonicity, M-monotonicity, is introduced, and the resolvent operator of an M-monotone operator is proved to be single valued and Lipschitz continuous. With the help of the resolvent operator, an equivalence between the variational inequality VI(C,F+G) and the fixed point problem of a nonexpansive mapping is established. A proximal point algorithm is constructed to solve the fixed point problem, which is proved to have a global convergence under the condition that F in the VI problem is strongly monotone and Lipschitz continuous. Furthermore, a convergent path Newton method, which is based on the assumption that the projection mapping ∏C(⋅) is semismooth, is given for calculating ε-solutions to the sequence of fixed point problems, enabling the proximal point algorithm to be implementable. 相似文献
784.
In this paper we generalize classical Lq, q≥p, estimates of the gradient to the Orlicz space for weak solutions of quasilinear elliptic equations of p-Laplacian type. 相似文献
785.
786.
787.
Vanessa Labet André Grand Prof. Jean Cadet Prof. Leif A. Eriksson Prof. 《Chemphyschem》2008,9(8):1195-1203
Five pathways leading to the deamination of cytosine (to uracil) after formation of its deprotonated radical cation are investigated in the gas phase, at the UB3LYP/6‐311G(d,p) level of theory, and in bulk aqueous solvent. The most favorable pathway involves hydrogen‐atom transfer from a water molecule to the N3 nitrogen of the deprotonated radical cation, followed by addition of the resulting hydroxyl radical to the C4 carbon of the cytosine derivative. Following protonation of the amino group (N4), the C4? N4 bond is broken with elimination of the NH3?+ radical and formation of a protonated uracil. The rate‐determining step of this mechanism is hydrogen‐atom transfer from a water molecule to the cytosine derivative. The associated free energy barrier is 70.2 kJ mol?1. 相似文献
788.
Stokes–Einstein (SE) and Stokes–Einstein–Debye (SED) relations in the neat ionic liquid (IL) [C2mim][NTf2] and IL/chloroform mixtures are studied by means of molecular dynamics (MD) simulations. For this purpose, we simulate the translational diffusion coefficients of the cations and anions, the rotational correlation times of the C(2)? H bond in the cation C2mim+, and the viscosities of the whole system. We find that the SE and SED relations are not valid for the pure ionic liquid, nor for IL/chloroform mixtures down to the miscibility gap (at 50 wt % IL). The deviations from both relations could be related to dynamical heterogeneities described by the non‐Gaussian parameter α(t). If α(t) is close to zero, at a concentration of 1 wt % IL in chloroform, both relations become valid. Then, the effective radii and volumes calculated from the SE and SED equations can be related to the structures found in the MD simulations, such as aggregates of ion pairs. Overall, similarities are observed between the dynamical properties of supercooled water and those of ionic liquids. 相似文献
789.
Andrew Bakan 《Journal of Mathematical Analysis and Applications》2008,339(1):197-216
For the sets , 1?p<∞, of positive finite Borel measures μ on the real axis with the set of algebraic polynomials P dense in Lp(R,dμ), we establish a majorization principle of their “boundaries,” i.e. for every there exists such that dμ/dν?1. A corresponding principle holds for the sets , p>0, of non-negative upper semi-continuous on R functions (weights) w such that P is dense in the space : For every there exists such that w?ω. 相似文献
790.
Joaquín Motos María Jesús Planells César F. Talavera 《Journal of Mathematical Analysis and Applications》2008,338(1):162-174
It is proved that the Hörmander and spaces (Ω1⊂Rn, Ω2⊂Rm open sets, 1?p<∞, ki Beurling-Björck weights, k=k1⊗k2) are isomorphic whereas the iterated spaces and are not if 1<p≠q<∞. A similar result for weighted Lp-spaces of entire analytic functions is also obtained. Finally a result on iterated Besov spaces is given: and are not isomorphic when 1<q≠2<∞. 相似文献