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排序方式: 共有1395条查询结果,搜索用时 42 毫秒
991.
Airapetian A Akopov N Akopov Z Amarian M Ammosov VV Andrus A Aschenauer EC Augustyniak W Avakian R Avetissian A Avetissian E Bailey P Baturin V Baumgarten C Beckmann M Belostotski S Bernreuther S Bianchi N Blok HP Böttcher H Borissov A Bouwhuis M Brack J Brüll A Bryzgalov V Capitani GP Chiang HC Ciullo G Contalbrigo M Dalpiaz PF De Leo R De Nardo L De Sanctis E Devitsin E Di Nezza P Düren M Ehrenfried M Elalaoui-Moulay A Elbakian G Ellinghaus F Elschenbroich U Ely J Fabbri R Fantoni A 《Physical review letters》2004,92(1):012005
Double-spin asymmetries of semiinclusive cross sections for the production of identified pions and kaons have been measured in deep inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with reanalyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data. 相似文献
992.
We report on a diode-pumped 1.3-microm Nd:GdVO4 cw laser, intracavity doubled for highly efficient generation of red light. We obtained as much as 2.4 W of power at 670 nm (corresponding to 26% optical-to-optical efficiency) in a nearly TEM00 mode and with small amplitude noise. To the best of our knowledge, these results represent the highest performance at this wavelength for cw solid-state lasers. 相似文献
993.
de Petris G Cartoni A Rosi M Troiani A Angelini G Ursini O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(24):6411-6421
A hitherto unknown, atmospherically relevant, isotope-exchange reaction was studied in ionised gaseous mixtures containing carbon dioxide and monoxide. The mechanism of the O exchange, proceeding over a double-minimum potential-energy surface, was positively established by mass spectrometric and theoretical methods that also allowed the identification and characterisation of the C2O3+ intermediate. The increase of internal energy displaces the observed reactivity towards an endothermic reaction path that involves only CO2 and represents an indirect route to the dissociation of carbon dioxide. 相似文献
994.
We present a microscopic model of the interaction and adsorption mechanism of simple organic molecules on SiC surfaces as obtained from ab initio molecular-dynamics simulations. Our results open the way to functionalization of silicon carbide, a leading candidate material for biocompatible devices. 相似文献
995.
Bazzicalupi C Bencini A Bianchi A Danesi A Giorgi C Lodeiro C Pina F Santarelli S Valtancoli B 《Chemical communications (Cambridge, England)》2005,(20):2630-2632
A protonated Zn(II) complex with a terpyridine-containing pentaamine macrocycle catalyses ATP hydrolysis in the presence of a second metal ion, which acts as cofactor assisting the phosphoryl transfer from ATP to an amine group of the receptor. 相似文献
996.
997.
998.
We present a model where the phase of a wave front is obtained by processing the intensity of speckle field pattern. By using the light propagation equation and knowing the intensity of the wavefront it is possible to build a system of linear equations which can be solved to give the wanted phase information. Simulations are presented and the convergence of the solution is discussed. 相似文献
999.
E. Comini S. Bianchi G. Faglia M. Ferroni A. Vomiero G. Sberveglieri 《Applied Physics A: Materials Science & Processing》2007,89(1):73-76
Quasi-one-dimensional nanostructures of tin oxide were produced in controlled conditions through condensation from the vapor
phase. The preparation was assisted by noble metal catalysts and uniform single-crystalline nanowires were produced. The nucleation
of nanowires was achieved at 470 °C, owing to the vapor–liquid–solid growth mechanism activated by the catalytic Pt clusters.
The peculiar microstructural properties of these semiconducting metal oxide nanostructures will be summarized. The high aspect
ratio and the high degree of crystallinity achieved for the nanowires foresee their functional exploitation.
PACS 61.46.Hk; 81.07.Bc; 81.16.Hc; 68.37.Lp 相似文献
1000.
Denlinger JD Clack JA Allen JW Gweon GH Poirier DM Olson CG Sarrao JL Bianchi AD Fisk Z 《Physical review letters》2002,89(15):157601
Complementary angle-resolved photoemission and bulk-sensitive k-resolved resonant inelastic x-ray scattering of divalent hexaborides reveal a >1 eV X-point gap between the valence and conduction bands, in contradiction to the band overlap assumed in several models of their novel ferromagnetism. This semiconducting gap implies that carriers detected in transport measurements arise from defects, and the measured location of the bulk Fermi level at the bottom of the conduction band implicates boron vacancies as the origin of the excess electrons. The measured band structure and X-point gap in CaB6 additionally provide a stringent test case for many-body quasiparticle band calculations. 相似文献