全文获取类型
收费全文 | 2599篇 |
免费 | 92篇 |
国内免费 | 24篇 |
专业分类
化学 | 1716篇 |
晶体学 | 9篇 |
力学 | 55篇 |
数学 | 513篇 |
物理学 | 422篇 |
出版年
2023年 | 22篇 |
2022年 | 75篇 |
2021年 | 62篇 |
2020年 | 59篇 |
2019年 | 54篇 |
2018年 | 63篇 |
2017年 | 57篇 |
2016年 | 99篇 |
2015年 | 60篇 |
2014年 | 96篇 |
2013年 | 183篇 |
2012年 | 166篇 |
2011年 | 206篇 |
2010年 | 143篇 |
2009年 | 112篇 |
2008年 | 150篇 |
2007年 | 154篇 |
2006年 | 141篇 |
2005年 | 122篇 |
2004年 | 100篇 |
2003年 | 75篇 |
2002年 | 75篇 |
2001年 | 28篇 |
2000年 | 33篇 |
1999年 | 14篇 |
1998年 | 23篇 |
1997年 | 27篇 |
1996年 | 33篇 |
1995年 | 12篇 |
1994年 | 19篇 |
1993年 | 16篇 |
1992年 | 14篇 |
1991年 | 20篇 |
1990年 | 11篇 |
1989年 | 10篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 17篇 |
1985年 | 20篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 20篇 |
1981年 | 19篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1911年 | 2篇 |
排序方式: 共有2715条查询结果,搜索用时 0 毫秒
141.
Rafael Mallol 《Mathematische Annalen》1960,140(4):344-350
Ohne Zusammenfassung 相似文献
142.
Benito Alcaide Rafael Prez-Ossosio Joaquin Plumet Miguel A. Sierra 《Tetrahedron letters》1982,23(52):5585-5586
The monoimine easily formed bydirect condensation between benzil and 2-aminopyridine adds alcohols and amines to the imine bond without catalysis. A concerted mechanism is proposed. 相似文献
143.
L?da Fontoura Costa G.?TraviesoEmail author C. A.?Ruggiero 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,44(1):119-128
This article investigates the functional properties of complex
networks used as grid computing systems. Complex networks following
the Erdös-Rényi model and other models with a preferential
attachment rule (with and without growth) or priority to the
connection of isolated nodes are studied. Regular networks are also
considered for comparison. The processing load of the parallel
program executed on the grid is assigned to the nodes on demand, and
the efficiency of the overall computation is quantified in terms of
the parallel speedup. It is found that networks with preferential
attachment allow lower computing efficiency than networks with
uniform link attachment. At the same time, considering only node
clusters of the same size, preferential attachment networks display
better efficiencies. The regular networks, on the other hand,
display a poor efficiency, due to their implied larger internode
distances. A correlation is observed between the topological
properties of the network, specially average cluster size, and their
respective computing efficiency. 相似文献
144.
145.
146.
Relative importance of hydrogen bonding and coordinating groups in modulating the zinc-water acidity
Mareque-Rivas JC Prabaharan R de Rosales RT 《Chemical communications (Cambridge, England)》2004,(1):76-77
The presence of second-sphere -NH(2) groups in the proximity of a zinc(ii)-bound water molecule enhances its acidity by ca. 2 pK(a) units. 相似文献
147.
Mareque-Rivas JC Torres Martín de Rosales R Parsons S 《Chemical communications (Cambridge, England)》2004,(5):610-611
Amino H-bond donors adjacent to a zinc(II) centre increase the affinity of phosphates to the zinc(II) centre. 相似文献
148.
Ayala R Martínez JM Pappalardo RR Sánchez Marcos E 《The Journal of chemical physics》2004,121(15):7269-7275
The aim of this work is to compute the stabilization energy E(stab)(n) of [X(H(2)O)(n)](-) (X identical with F, Br, and I for n=1-60) clusters from Monte Carlo simulations using first-principles ab initio potentials. Stabilization energy of [X(H(2)O)(n)](-) clusters is defined as the difference between the vertical photodeachment energy of the cluster and the electron affinity of the isolated halide. On one hand, a study about the relation between cluster structure and the E(stab)(n) value, as well as the dependence of the latter with temperature is performed, on the other hand, a test on the reliability of our recently developed first-principles halide ion-water interaction potentials is carried out. Two different approximations were applied: (1) the Koopmans' theorem and (2) calculation of the difference between the interaction energy of [X(H(2)O)(n)](-) and [X(H(2)O)(n)] clusters using the same ab initio interaction potentials. The developed methodology allows for using the same interaction potentials in the case of the ionic and neutral clusters with the proviso that the charge of the halide anion was switched off in the latter. That is, no specific parametrization of the interaction potentials to fit the magnitude under study was done. The good agreement between our predicted E(stab)(n) and experimental data allows us to validate the first-principles interaction potentials developed elsewhere and used in this study, and supports the fact that this magnitude is mainly determined by electrostatic factors, which can be described by our interaction potentials. No relation between the value of E(stab)(n) and the structure of clusters has been found. The diversity of E(stab)(n) values found for different clusters with similar interaction energy indicates the need for statistical information to properly estimate the stabilization energy of the halide anions. The effect of temperature in the prediction of the E(stab)(n) is not significant as long as it was high enough to avoid cluster trapping into local equilibrium configurations which guarantees an appropriate sampling of the configurational space. Parallel tempering method was applied in particular cases to guarantee satisfactory sampling of clusters at low temperature. 相似文献
149.
A natural-product-inspired photonic logic gate based on photoinduced electron-transfer-generated dual-channel fluorescence 总被引:1,自引:0,他引:1
[structure: see text] Modified 1-benzylisoquinoline N-oxides can operate as molecular logic gates. The combination of dual-channel fluorescence emissions and the preferred interaction for selected chemical inputs allows one to design multifunction and self-reprogrammable molecular logic gates. 相似文献
150.
Rafael?D.?BenguriaEmail author Semjon?A.?Vugalter 《Letters in Mathematical Physics》2004,70(3):249-257
For the Pauli–Fierz operator with a short range potential we study the binding threshold 1() as a function of the fine structure constant and show that it converges to the binding threshold for the Schrödinger operator in the limit 0.This work was supported in part by Fondecyt (Chile), Project #102-0844. Work partially supported by HPRN-CT-2002-00277, and the Volkswagen Stiftung through a cooperation grant. 相似文献