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991.
Dominik Lungerich Jakob F. Hitzenberger Mario Marcia Frank Hampel Thomas Drewello Norbert Jux 《Angewandte Chemie (International ed. in English)》2014,53(45):12231-12235
A free‐base porphyrin carrying two hexabenzocoronene (HBC) substituents in a trans arrangement and its zinc complex have been prepared. The compounds were characterized extensively and found to form tricationic dimers in the gas phase. X‐ray crystallography confirms for the zinc complex a profound π‐stacking of the HBC moieties. In contrast, the free‐base porphyrin incarcerates n‐heptane which essentially prevents π‐stacking. Upon excitation of the HBC substituents, efficient energy transfer to the central porphyrin is observed. 相似文献
992.
Christine Artner Matthias Czakler Prof. Dr. Ulrich Schubert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):493-498
Mixed‐metal clusters have been obtained from the reaction of titanium alkoxides with either strontium or lead acetate and methacrylic acid. The structures of the clusters are derived from the metallacycle Ti8O8(methacrylate)16. The Sr and Pb atoms in Sr2Ti8O8X2(OOCMe)2(methacrylate)16 (X: acetate or OiPr) and Pb2Ti8O8(OBu)2X2(methacrylate)16(BuOH)2 (X: acetate or methacrylate) occupy the central cavity of the Ti8O8 ring. In addition to the crown‐ether‐like coordination of the ring oxygen atoms to the Sr or Pb atoms, bridging carboxylate ligands support the coordination of the latter atoms. In the compound Pb2Ti6O5(OiPr)3X(methacrylate)14 (X: OiPr or methacrylate), the lead atoms are coordinated by a fragment of the Ti8O8(methacrylate)16 metallacycle. 相似文献
993.
Miguel Angel Harvey Sebastin Suarez Fabio Doctorovich Fabio D. Cukiernik Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(5):440-444
The CoII cation in poly[[aqua(μ‐benzene‐1,2‐dicarboxylato‐κ3O1,O2:O1)(μ‐4,4′‐bipyridine‐κ2N:N′)cobalt(II)] trihydrate], {[Co(C8H4O4)(C10H8N2)(H2O)]·3H2O}n, is octahedrally coordinated by two N atoms of two 4,4′‐bipyridine ligands, three O atoms from phthalate anions and a fourth O atom from a coordinated water molecule. The packing consists of planes of coordination polymers linked by hydrogen bonds mediated by three solvent water molecules; the linkage is achieved by the water molecules forming intricate oligomeric clusters which also involve the O atoms of the phthalate ligands. 相似文献
994.
Natarajan Sathiyamoorthy Venkataramanan Ambigapathy Suvitha Hiroshi Mizuseki Yoshiyuki Kawazoe 《International journal of quantum chemistry》2013,113(15):1940-1948
The structure, stability, adsorption, and dissociation of H2 on nickel clusters doped with late transition metals were investigated using density functional theory with the BP86 functional. Molecular hydrogen physisorption occurred at a vertex atom with a low coordination number. Charge transfer between clusters and the H2 molecule stabilized the physisorption. The chemisorption of H2 occurred at the bridge sites, without any structural or spin change of the clusters. Among the pentamer clusters, Cd, Zn, and Au had the lowest chemisorption energies, while Ir and Pt had higher chemisorption energies for hydrogen. The computed reaction energies and activation barriers for the dissociation mechanism showed that dopants such as Rh, Pd, Pt, and Au have endothermic reaction energies and low activation barriers. This facilitates the reversible adsorption/dissociation of the H2 molecule on these metal‐doped clusters. The dopant atoms play a major role in modulating the physisorption, chemisorption, and dissociation mechanism of H2 on nickel clusters. © 2013 Wiley Periodicals, Inc. 相似文献
995.
Vacancy-solute complexes and their clusters in iron 总被引:1,自引:0,他引:1
J. Kuriplach O. Melikhova C.S. Becquart L. Malerba A. Almazouzi A.L. Morales 《Applied Surface Science》2006,252(9):3303-3308
In this contribution, several vacancy-solute complexes in iron are investigated theoretically from the viewpoint of positron annihilation. In particular, V-Si, V-P, V-Cr, V-Mn, V-Ni, V-Cu and V-Mo complexes are examined. In addition, nano-sized vacancy-Cu clusters in the Fe matrix are also studied. We concentrate on positron lifetimes and coincidence Doppler broadening profiles that bring complementary information about the studied complexes and their clusters. Positron calculations are carried out using the atomic superposition method employing realistic atomic configurations obtained recently using an ab initio pseudopotential method (vacancy-solute complexes) and Monte Carlo/molecular dynamics methods (vacancy-Cu clusters). The main aim of this study is to predict as to what extent such defects are detectable and differentiable using positron annihilation techniques. The results obtained are discussed in the context of experimental data available in the literature. 相似文献
996.
997.
The eigenmodes of a non-viscous, compressible liquid drop are investigated. The spectrum is shown to be derivable from two Hermitian eigenvalue problems which are weakly coupled by a non-Hermitian operator. It is shown that both eigenvalue problems admit an asymptotic, lepto-dermous expansion. Their contribution to the entropy of the droplet therefore also allows for such an expansion. 相似文献
998.
利用Gausian94量子化学从头算程序,选择UMP2/6-311G方法,对N+2Nen(n=1,2,3)的离子簇合物进行了几何全优化,并通过频率分析确认了体系的稳定构型,得到了各稳定簇合物的离解能.用UHF/6-311G方法,计算了N+2离子在n个氖原子(n=1,2,3)氛围中的转动势垒.计算表明:线性结构是N+2Nen(n=1,2)的最稳定结构;与N+2Hen比较,N+2Nen的诱导电荷更大,束缚势阱更深,各向导性明显,N+2没有在原子氛围中的自由这些计算与Maier实验结果一致. 相似文献
999.
B. Hartke 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):57-60
The method of global geometry optimization of atomic and
molecular clusters by evolutionary algorithms is briefly
presented and reviewed. As an exemplary application of a
parallelized implementation of such an algorithm, neutral pure
water clusters are globally optimized. In contrast to previous
studies, the sophisticated and quantitatively reliable TTM2-F
potential is employed. Significant qualitative differences to
the earlier results are found, implicating a breakdown of simple
water models for water clusters of non-trivial size. 相似文献
1000.
N. Nishi K. Kosugi K. Hino T. Yokoyama 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):97-100
A new type of Co-C nanoparticles is synthesized from
CH2Cl2 solution of
Co4(CO)1
2 by heating up to 210
°C in a closed vessel. Transmission
electron microscope (TEM) and electron energy loss spectroscopy
(EELS) observation show that the particles are embedded in
amorphous carbon and their average size is 12 nm. The radial
structure function obtained from the extended X-ray absorption
fine structure (EXAFS) of the Co K-edge absorption of the Co-C
nanoparticles provides a Co-C average distance of 2.08 Å and the
Co-Co distances of 3.18 Å and 3.9 (±0.2) Å. The particles
exhibit the magnetic hysteresis curve with a coercive force of
200 Oe at 20 K and 260 Oe at 300 K. The temperature dependence
of the magnetic susceptibility measured under zero-field cooling
and 10 Oe field cooling conditions exhibits the behavior
characteristic of a set of single magnetic domain nanomagnets in
an amorphous carbon matrix. 相似文献