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61.
In this critical review, the strategic and economic benefits of C-H functionalization logic will be analyzed through the critical lens of total synthesis. In order to illustrate the dramatically simplifying effects this type of logic can potentially have on synthetic planning, we take the reader through a series of case studies in which it has already been successfully applied. In the first section, a chronological look at key historical syntheses will be examined, leading into modern day examples. In the second section, our own experience with applying and executing synthesis with a C-H functionalization "mindset" will be discussed (114 references). 相似文献
62.
Using results from the dielectric theory of polar solids and liquids, we calculate the mesoscopic, spatially-varying dielectric constant at points in and around a protein by combining a generalization Kirkwood-Fr?hlich theory along with short all-atom molecular dynamics simulations of equilibrium protein fluctuations. The resulting dielectric permittivity tensor is found to exhibit significant heterogeneity and anisotropy in the protein interior. Around the surface of the protein it may exceed the dielectric constant of bulk water, especially near the mobile side chains of polar residues, such as K, N, Q, and E. The anisotropic character of the protein dielectric selectively modulates the attractions and repulsions between charged groups in close proximity. 相似文献
63.
Delay differential equations are of sufficient importance in modelling real-life phenomena to merit the attention of numerical
analysts. In this paper, we discuss key features of delay differential equations (DDEs) and consider the main issues to be
addressed when constructing robust numerical codes for their solution. We provide an introduction to the existing literature
and numerical codes, and in particular we indicate the approaches adopted by the authors. We also indicate some of the unresolved
issues in the numerical solution of DDEs.
Communicated by J.C. Mason 相似文献
64.
65.
Simona Percec Ross Getty Will Marshall Gabriel Skidd Roger French 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):541-550
Oligomers consisting of aromatic building blocks separated by alkynyl units were synthesized by Sonogashira cross-coupling of aryl halides with terminal acetylenes. Strong electron acceptors such as F and CF3 and weak electron donors like CH3 were placed as substituents on one of the benzene rings. Acetyl-protected sulfhydryl groups were attached to one end of these molecules to promote their self-organization on gold surfaces. The electron-transport properties of such self-assembled monolayers (SAMs) are highly sensitive to the local order of the molecules in the solid state. Single crystals were analyzed by X-ray diffraction experiments that revealed structural details that could lead to a better understanding of the electron-transport properties. The unsymmetrical substitution of the aromatic rings by electron-active groups in the ortho-, meta-, or para positions resulted in changes of such molecular parameters as bonding and torsion angles and planarity. These parameters, in turn, can affect the angle of the molecular attachment to a gold substrate and the density of the resulting SAMs. Patterned SAMs of some of these molecules and comparison alkane thiols were obtained on gold by microcontact printing or flooding. The SAM thickness was determined by spectroscopic ellipsometry. Surface potential differences between adjacent SAMs or between SAMs and the gold substrate were measured by scanning surface potential microscopy under ambient conditions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 541–550, 2004 相似文献
66.
Joykrishna Dey A. Yvette Will Rezik A. Agbaria Peter W. Rabideau Atteye H. Abdourazak Renata Sygula Isiah M. Warner 《Journal of fluorescence》1997,7(3):231-236
The spectroscopic properties of corannulene and cyclopentacorannulene are examined by use of absorption and steady-state fluorescence
measurements. A red shift in the emission maxima of cyclopentacorannulene is noted with respect to the emission maxima in
the corannulene spectrum. Similar differences in the absorption spectra of both molecules are also observed. Reasons for the
dissimilarities in the absorption and emission spectra of these molecules are discussed. The fluorescence quantum yields and
lifetimes of the molecules measured in organic solvents are reported. The fluorescence quantum yield and lifetime of cyclopentacorannulene
are lower than those of corannulene. This difference is attributed to the highly strained and nonplanar structure of cyclopentacorannulene.
The effectiveness of nitromethane as a quencher of corannulene and cyclopentacorannulene fluorescence is examined. In contrast
to previously reported results, the fluorescence of these molecules is quenched by nitromethane. Fluorescence quenching of
the molecules has been attributed to complex formation in the ground state, i.e., static quenching. 相似文献
67.
The only known examples of Anosov diffeomorphisms are hyperbolic automorphisms of infranilmanifolds, and the existence of such automorphisms is a really strong condition on the rational nilpotent Lie algebra determined by the lattice, so called an Anosov Lie algebra. We prove that n⊕?⊕n (s times, s≥2) has an Anosov rational form for any graded real nilpotent Lie algebra n having a rational form. We also obtain some obstructions for the types of nilpotent Lie algebras allowed, and use the fact that the eigenvalues of the automorphism are algebraic integers (even units) to show that the types (5,3) and (3,3,2) are not possible for Anosov Lie algebras. 相似文献
68.
69.
P. Gippner K. D. Schilling F. Stary E. Will K. Heidel S. M. Lukyanov Yu. E. Penionzhkevich V. S. Salamatin H. Sodan G. G. Chubarian R. Schmidt 《Zeitschrift für Physik A Hadrons and Nuclei》1988,330(4):433-434
TotaT kinetic energy vs. fragment mass distributions have been measured in the reactions of64Zn projectiles with114Sn,natAg and139La nuclei at incidence energies of 20–50% above the Coulomb barrier. Conclusions are drawn on the possible influence of nuclear structure effects on the energy dissipation and the mass drift behaviour of the present collision systems. 相似文献
70.