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991.
StructureofPotassiumofUndecatungstomononickelosilicateQuLun-Yu;MaRong-Hua;ChenYa-Guang(DepartmentofChemistry,NortheastNormalU... 相似文献
992.
Bernhard Spingler Jürgen F.K Müller Markus Neuburger Margareta Zehnder 《Journal of organometallic chemistry》1998,570(2):700
Bicyclic chiral phosphoric triamide 1 reacts after lithiation and addition with several electrophiles in a highly regio- and diastereoselective fashion. The stannylated product 2 can be recrystallised to a single diastereomer. Its X-ray analysis is the first solid state structure determination of a chiral hexamethylphosphoric triamide analogue. 相似文献
993.
994.
Adeline Leyris 《Tetrahedron letters》2005,46(50):8677-8680
Both enantiomers of tert-butylphenylphosphine oxide can be easily synthesised starting from (S)-prolinol-based oxazaphospholidine. 相似文献
995.
Yoichi Sakai Ryo Omatsuzawa Iwao Sakazaki Sayaka Suzuki Hayato Hashino Takanobu Saito Takahiko Iriyama 《Hyperfine Interactions》2005,166(1-4):483-487
Samarium–iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th2Zn17-type and a TbCu7-type structure, respectively. Structure comparison between these types was investigated for Sm–Fe intermetallic compounds and their nitrides by 57Fe-Mössbauer spectroscopy. 相似文献
996.
The thermal properties and thermal stability of diaspore-corundum (AlOOH-Al2O3), from Goian (Pontevedra, Spain) were studied by means of differential thermal analysis (DTA), thermogravimetry (TG), high temperature X-ray diffraction (HTXRD) and thermally stimulated luminescence (TL) techniques. The samples were annealed to link the combined effect of (i) dehydroxylation, (ii) oxidation-reduction of chromophores (Mn 0.5%, Fe2O3 0.12%, TiO2 0.021% and Cr 80 ppm) determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and (iii) phase transitions whilst sample heating (i.e. α-AlOOH→α′-Al2P3→α-Al2O3). The blue colour of diaspore, attributed to the Ti4+-Fe2+ intervalence-charge-transfer mechanism, turns to white (circa 500 °C) in good agreement with the DTA endothermic peak (dehydroxylation). The coexistence of α-AlOOH and α′-Al2P3 phases has been detected by in situ HTXRD and could be correlated to the thermoluminescence tests performed on preheated aliquots (up to 500 °C). 相似文献
997.
Deyue Zhang Fuming Ma 《高等学校计算数学学报(英文版)》2006,15(2):164-179
1 Introduction The phenomenon of optical activity in special materials has been known since the beginning of the last century. Whereas optical activity has been considered in optics and in quantum mechanics for many years, its analysis within the framewor… 相似文献
998.
Krzysztof Lewiski Julita Eilmes 《Journal of inclusion phenomena and macrocyclic chemistry》2005,52(3-4):261-266
Recrystallization of the title Cu(II) complex from pyridine afforded solid (1:1) pyridine inclusion compound. The crystal structure revealed a pleated-sheet-like arrangement of saddle-shaped molecules of the host, with molecules of pyridine enclathrated within intermolecular cavities. Careful analysis of intermolecular contacts showed that weak aromatic edge-to-face (C–H···Fπ) interactions occur between pyridine and host molecules. The crystal packing appeared to be also stabilized by the host–host C–H···O hydrogen bonds.in final form: 22 December 2004This revised version was published online in July 2005 with a corrected issue number. 相似文献
999.
Two acyl and three fluoroacyl derivatives of 32 chiral alcohols have been chromatographed on a GC column coated with octakis(2,6-di-O-n-pentyl-3-O-trifluoroacetyl)- γ-cyclodextrin. Significant differences were observed between the stereoselectivity obtained for the derivatives and that for the underivatized alcohols. Of the derivatives, only the fluoroacylated compounds were separated into enantiomers. Derivatization with fluoroacyl groups reversed the elution order for at least some of the analytes. Stereoselectivity towards simple 2- and 3-hydroxy alkanes and their fluoroacyl derivatives was highest for those alcohols with a four-carbon chain attached to the stereogenic center. For longer-chain fluoroacyl derivative groups stereoselectivity was higher for the 2- and 3-hydroxy alkanes. Differences in stereoselectivity towards alcohols with a methyl-branched alkane chain and their fluoroacyl derivatives was related to the distance between the methyl group and the hydroxyl or fluoroacyl groups. Different degrees of saturation in the carbon chain resulted in differences in stereoselectivity. Thermodynamic data calculated for a number of analytes suggest that the alcohols and trifluoroacetate derivatives are interacting with the stationary phase by similar mechanisms. The stereospecific interaction appears to have a hydrogen bonding or dipole–dipole contribution and some form of steric component, depending upon the shape and/or size of the solute. 相似文献
1000.