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排序方式: 共有658条查询结果,搜索用时 15 毫秒
641.
Grechko M Maksyutenko P Zobov NF Shirin SV Polyansky OL Rizzo TR Boyarkin OV 《The journal of physical chemistry. A》2008,112(42):10539-10545
We report here an experimental approach that enables measurement of weak transitions to a wide range of rovibrational levels of water in the energy region 27,000-34,200 cm(-1). We have previously demonstrated the use of laser double-resonance overtone excitation to access highly excited vibrational levels from single rovibrational states. Although this approach simplifies the assignment of the spectra, it strongly reduces the number of observed transitions and hence our ability to test theoretical predictions. Here, we increase significantly the number of observed transitions by allowing rotational relaxation of H2O at intermediate levels of the double-resonance excitation scheme to the levels of the same nuclear spin (ortho or para). Our recently developed semiempirical potential energy surface PES12 enables assignment of the resulting complex spectra and reproduction of the measured transitions with accuracy better than 1 cm(-1). 相似文献
642.
Edmonds MT Wanke M Tadich A Vulling HM Rietwyk KJ Sharp PL Stark CB Smets Y Schenk A Wu QH Ley L Pakes CI 《The Journal of chemical physics》2012,136(12):124701
Surface sensitive C1s core level photoelectron spectroscopy was used to examine the electronic properties of C(60)F(48) molecules on the C(100):H surface. An upward band bending of 0.74 eV in response to surface transfer doping by fluorofullerene molecules is measured. Two distinct molecular charge states of C(60)F(48) are identified and their relative concentration determined as a function of coverage. One corresponds to ionized molecules that participate in surface charge transfer and the other to neutral molecules that do not. The position of the lowest unoccupied molecular orbital of neutral C(60)F(48) which is the relevant acceptor level for transfer doping lies initially 0.6 eV below the valence band maximum and shifts upwards in the course of transfer doping by up to 0.43 eV due to a doping induced surface dipole. This upward shift in conjunction with the band bending determines the occupation of the acceptor level and limits the ultimately achievable hole concentration with C(60)F(48) as a surface acceptor to values close to 10(13) cm(-2) as reported in the literature. 相似文献
643.
644.
The first synthesis of (-)-heronapyrrole C, the enantiomer of a unique farnesylated 2-nitropyrrole natural product is described. With none of the chiral centers of heronapyrrole C originally assigned, we proposed the most likely natural configuration on the basis of a putative biosynthetic pathway. The key step of the synthesis is a biomimetic polyepoxide cyclization cascade to establish the bis-THF moiety. Thus, (-)-heronapyrrole C is synthesized in eight steps from commercially available starting materials. 相似文献
645.
Zabardasti Abedien Joshaghani Mohammad Nadri Shirin Goudarziafshar Hamid Salehnassaj Maryam 《Structural chemistry》2012,23(5):1497-1502
Structural Chemistry - Ab initio calculations at the MP2/6-311++G(d,p) computational level were used to analyze the interactions between a molecule of B2H6 with some small molecules which often... 相似文献
646.
This review aims to provide a comprehensive overview of the recent advances made in the field of ionic liquids in peptide chemistry and peptide analytics. 相似文献
647.
Zhang J Zhao Y Guan X Stark RE Akins DL Lee JW 《The journal of physical chemistry. C, Nanomaterials and interfaces》2012,116(3):2639-2644
To efficiently recycle CO(2) to economically viable products such as liquid fuels and carbon nanomaterials, the reactivity of CO(2) is required to be fully understood. We have investigated the reaction of CO(2) with ammonia borane (AB), both molecules being able to function as either an acid or a base, to obtain more insights into the amphoteric activity of CO(2). In the present work, we demonstrate that CO(2) can be converted to graphene oxide (GO) using AB at moderate conditions. The conversion consists of two consecutive steps: CO(2) fixation (CO(2) pressure < 3 MPa and temperature < 100 °C) and graphenization (600-750 °C under 0.1 MPa of N(2)). The first step generates a solid compound that contains methoxy (OCH(3)), formate (HCOO) and aliphatic groups while the second graphenization is the pyrolysis of the solid compound to produce graphene oxide-boron oxide nanocomposites, which have been confirmed by micro-Raman spectroscopy, solid state (13)C and (11)B magic angle spinning-nuclear magnetic resonance (MAS-NMR), transmission electron microscopy (TEM), and atomic force microscopy (AFM). Our observations also show that the mass of solid product in CO(2) fixation process and raw graphene oxide nanocomposites is twice and 1.2 times that of AB initially charged, respectively. The formation of aliphatic groups without using metal-containing compounds at mild conditions is of great interest to the synthesis of various organic products starting from CO(2.). 相似文献
648.
649.
Dynamics of fracture in drying suspensions 总被引:1,自引:0,他引:1
Dufresne ER Stark DJ Greenblatt NA Cheng JX Hutchinson JW Mahadevan L Weitz DA 《Langmuir : the ACS journal of surfaces and colloids》2006,22(17):7144-7147
We investigate the dynamics of fracture in drying films of colloidal silica. Water loss quenches the nanoparticle dispersions to form a liquid-saturated elastic network of particles that relieves drying-induced strain by cracking. These cracks display intriguing intermittent motion originating from the deformation of arrested crack tips and aging of the elastic network. The dynamics of a single crack exhibits a universal evolution, described by a balance of the driving elastic power with the sum of interfacial power and the viscous dissipation rate of flowing interstitial fluid. 相似文献
650.