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991.
992.
In the paper, piezoelectric induced Lamb wave propagation on homogeneous plates is studied by applying different approaches. Assuming the presence of piezoelectric actuators and sensors the transient wave analysis is made using the classical formulation of the finite element method (FEM) and the novel approach of spectral finite element method (SE). Pure mode excitation and mode conversion are numerically simulated for the fundamental modes S0 and A0. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
993.
Zair Asrar Bin Ahmad Juan Miguel Vivar Perez Christian Willberg Ulrich Gabbert 《PAMM》2009,9(1):509-510
Some of the available techniques for Lamb wave propagation simulation are the Finite Element Method (FEM), the Boundary Element Method and the Finite Difference Method. The FEM is the best method when complex damage, geometry or boundary is involved. However, high Lamb wave frequency requires very small element size thus high computational cost in FEM analysis. By using the existence of periodicity in plates, an attempt to reduce this computational cost is done using Wave FEM. The applicability of this method to model Lamb wave propagation in plate is first assessed in this paper for the 1-D wave propagation and compared with FEM explicit method. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
994.
In the paper methods for the coupling of different meshed local domains of a product model, which occur in an adaptivity process are compared. The properties of the applied coupling methods are demonstrated on finite element models from structural mechanics to point out the advantages and disadvantages of the methods in a model adaptivity process in the field of automotive engineering. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
995.
Marina M. Lezhnina Edgar Jordan Sergej A. Klimin Jürgen Löns Hubert Koller Boris N. Mavrin Ulrich Kynast Prof. Dr. 《无机化学与普通化学杂志》2009,635(3):450-455
In the course of investigations on optical properties resulting from the interaction of fluorides with alumosilicate host materials and rare earth guests, a well defined BF4– ion wasfound to be incorporated within the sodalite of composition Na8Al6Si6O24(BF4)2. The resulting cubic molecular structure, which was determined by Rietveld methods (space group P4 n, a = 906.91 pm, wRp = 0.045, Rp = 0.027), contains one anion in each sodalite cage and is, contrarily to expectations, thermally stable. NMR spectroscopic investigations indicated a fast rotatory motion of the BF4– tetrahedra at room temperature and agreed with the tetrahedral BF4– ions found in IR and Raman spectra. Preliminary attempts to obtain a luminescent material by incorporation of Eu3+ through aqueous ion exchange only yielded low rare earth concentrations, giving rise to characteristic red emission lines at 581 nm (5D0 → 7F1) and 615 nm (5D0 → 7F2) in a 1:2 intensity ratio. The material unexpectedly exhibited a strong broad band emission at 520 nm after calcination under Ar, which is attributed to the formation of an Eu2+ species. Further calcination under air partially reestablished the Eu3+ emission. 相似文献
996.
Martin Hofmann Dr. Christine Höhn Frank W. Heinemann Dr. Ulrich Zenneck Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(24):5998-6007
Cage chirality : Cyclic addition reactions of chirally modified stannyl‐1,2,4‐triphospholes with tBuC?P leads to stannylated P5‐deltacyclenes in high yields as separable 1:1 mixtures of diastereomers. Destannylation of a separated diastereomer gives a single enantiomer of an optically pure P? C cage compound. The novel cage‐chiral P5C4 unit (shown here) dominates the chiroptical properties, not only of the isolated enantiomer, but of the diastereomeric compounds as well.
997.
Samples of the solid solution [ZnSnSb2]1−x[2(InSb)]x have been prepared over the whole range of composition by tin flux synthesis. The lattice parameter of the sphalerite-type average structure varies linearly between that of the end members ZnSnSb2 and InSb, a=6.2849(2) and 6.4776(15), respectively. Electron diffraction shows different kinds of structured diffuse scattering for Zn and In rich samples, respectively. The former is attributed to compositional short range ordering, the latter to thermally excited phonon modes. A metal-nonmetal transition takes place between the compositions x=0.8 and x=0.9. 相似文献
998.
Tae-Soo You Jing-Tai Zhao Rainer Pttgen Walter Schnelle Ulrich Burkhardt Yuri Grin Gordon J. Miller 《Journal of solid state chemistry》2009,182(9):2430-2442
Two isoelectronic series, Eu(Ga1−xTtx)2 (Tt=Si, Ge, 0≤x≤1), have been synthesized and characterized by powder and single-crystal X-ray diffraction, physical property measurements, and electronic structure calculations. In Eu(Ga1−xSix)2, crystal structures vary from the KHg2-type to the AlB2-type, and, finally, the ThSi2-type structure as x increases. The hexagonal AlB2-type structure is identified for compositions 0.18(2)≤x<0.70(2) with Ga and Si atoms statistically distributed in the polyanionic 63 nets. As smaller Si atoms replace Ga atoms while the number of valence electrons increases, the lattice parameters, unit cell volumes, and Ga–Si distances in this phase region decrease significantly. Although aspects of X-ray diffraction results suggest puckering of the 63 nets for the Si-richest example of the AlB2-type Eu(Ga1−xSix)2, the complete experimental evidence remains inconclusive. On the other hand, in Eu(Ga1−xGex)2, six different structural types were observed as x varies. In addition to EuGa2 (KHg2-type; space group Imma) and EuGe2 (own structure type, space group P3¯m1), the ternary phases studied show four different structures: the AlB2-type for Ga-rich compositions; the YPtAs-type structure for EuGaGe; and two new structures, which are intergrowths of the YPtAs-type EuGaGe and EuGe2, for Ge-rich compositions. These two Ge-rich phases include: (1) Eu(Ga0.45(2)Ge0.55(2))2 containing two YPtAs-type motifs of EuGaGe plus one EuGe2 motif; and (2) Eu(Ga0.40(2)Ge0.60(2))2 containing one YPtAs-type motif alternating with a split site at and z=0.4798(2) with ca. 50% site occupancy by Ga and Ge along the c-axis. Magnetic susceptibilities of three Eu(Ga1−xGex)2 compounds display Curie–Weiss behavior above ca. 100 K, and show effective magnetic moments indicative of divalent Eu with a 4f7 electronic configuration, consistent with. X-ray absorption spectra (XAS). Density of states (DOS) and crystal orbital Hamilton population (COHP) analyses, based on first principles electronic structure calculations, rationalize the observed homogeneity ranges of the AlB2-type phases in both systems and the structural variations as a function of Tt content. 相似文献
999.
Tetyana Beryozkina Dr. Ksenia Boyko Natalya Khanduyeva Volodymyr Senkovskyy Dr. Marta Horecha Ulrich Oertel Dr. Frank Simon Dr. Manfred Stamm Prof. Anton Kiriy Dr. 《Angewandte Chemie (International ed. in English)》2009,48(15):2695-2698
Graft work : The first surface‐initiated and site‐specific palladium‐catalyzed Suzuki polycondensation that allows selective grafting and patterning of semiconducting and emissive poly[9,9‐bis(2‐ethylhexyl)fluorene] ( 1 ) at room temperature is developed (see scheme). The pattering is demonstrated by AFM (see image).
1000.
Simon Reitz Menekse Cebi Philipp Reiß Gregor Studnik Uwe Linne Ulrich Koert Prof. Dr. Lars‐Oliver Essen Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(26):4853-4857
The attachment of modulators to a trimeric porin ion channel was investigated (see picture of the trimer with a crown ether modulator (orange)). The interplay of modulator and protein is essential for the conformational heterogeneity of the hybrid channel. Single‐site attachment in large pores is not sufficient to change the electrophysiological characteristics of the pores—such change requires additional noncovalent interactions or second‐site attachments.