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991.
V. V. Barbakadze E. P. Kemertelidze I. Targamadze K. Mulkidzhanyan J. Kemink A. J. J. van den Berg K. J. Beukelman A. I. Usov 《Chemistry of Natural Compounds》2005,41(4):374-377
Two high-molecular-weight (>1000 kDa) water-soluble preparations were isolated from stems of Symphytum asperum and S. caucasicum. Their basic component was established as poly[hydroxy-1-carboxy-2-(3,4-dihydroxyphenyl)ethylene], analogous to that of high-molecular-weight
(>1000 kDa) preparations from roots of these same plants, using IR and NMR spectral data.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 303–305, July–August, 2005.
An erratum to this article is available at . 相似文献
992.
The complex permittivity for chlorobenzene–alcohol binary mixtures have been determined over the frequency range of 10 MHz to 20 GHz, at 15, 25, 35, and 45°C, using the time-domain reflectometry (TDR) method for 11 concentrations of each chlorobenzene–alcohol system. The alcohols used were methanol, ethanol, and 1-propanol. The values of static dielectric constant, relaxation time, the corresponding excess properties, the Redlich–Kister coefficients up to the third order, the Kirkwood correlation factor, and thermodynamic parameters of the mixtures have been determined. The excess permittivity is found to be negative for chlorobenzene–methanol and chlorobenzene–ethanol, whereas it is positive in the 1-propanol rich region. The excess inverse relaxation time is negative for all the systems studied here. The Kirkwood effective correlation factor increases with an increasing in the molecular size of the alcohol, but decreases with increasing temperature. 相似文献
993.
HUANG Zun-Xing WANG Xiu-Li LIU Shi-Xiong 《结构化学》2002,21(5):505-508
1 INTRODUCTION Transition metal complexes with ferrocene are of considerable interest in the past fifty years because of their novel structures and special properties[1, 2]. The chemistry of ferrocene and its derivatives has become richer and richer in the last decade. Many complexes containing ferrocenyl have been synthesized and characterized[3~5]. Recently we have reported the synthesis and crystal structure of dibromo[1,1?bis(diphenylphosphino)- ferrocene]cadmium (Ⅱ)[6]. Herein we… 相似文献
994.
Antonella Cartoni Andrea Margonelli Alessandro Finazzi-Agrò 《Tetrahedron letters》2004,45(13):2723-2726
Endocannabinoids have emerged as a new class of lipid mediators, with manifold roles in the central nervous system and in the periphery. Several studies have identified 2-arachidonoyl-glycerol (2-AG) as a major endogenous agonist of cannabinoid receptors. Here, the chemical synthesis of 2-AG is reported, along with the synthesis of its tritium-labeled derivative. These unlabeled and radiolabeled compounds are suitable tools for unravelling some metabolic routes and biological activities of 2-AG in various cells and tissues. 相似文献
995.
High reactivity of the nitrite group in (NN-difluoroamino)dinitroacetonitrile was demonstrated. Based on its reaction with HN3, a new preparative method for the synthesis of 5-[(N,N-difluoroamino)dinitromethylltetrazole was developed; some derivatives of the latter compound have been obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8. pp. 2056–2058, August, 1996. 相似文献
996.
Summary A model of the mechanism for recognition of the D1 receptor has been developed. Conformational analysis for 10 agonists from diverse chemical families was carried out as a first step toward the characterization of the bioactive form. First, maximum structural overlap of the features common to all ligands allowed a simple identification of the candidate bioactive form for each ligand. At a second level of characterization, steric and electronic properties were computed for all accessible structures to analyze those properties that may modulate receptor recognition. 相似文献
997.
Ming Hu Eli M. Pearce T. K. Kwei 《Journal of polymer science. Part A, Polymer chemistry》1993,31(2):553-561
Poly(N1,N3-dimethylbenzimidazolium) (PDMBI) salt and poly(N1-methylbenzimidazole) (PMMBI) were synthesized by methylation of commercial polybenzimidazole [poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole (PBI)]. First, the N-lithium salt of polybenzimidazole was formed by treating polybenzimidazole solution of 1-methyl-2-pyrolidinone (NMP) with lithium hydride at 80°C for 18 h. Ninety percent substitution of PMMBI was obtained by treating the N-lithium salt of PBI with equimolar ratio of iodomethane at room temperature. Upon addition of excess iodomethane to the lithium salt of PBI at 80°C, a polymer was formed that showed 100% substitution on the N1 nitrogen and about 30% substitution of the methyl group on the N3 nitrogen in the form of N1,N3-dimethylbenzimidazolium iodide salt [PDMBI (30%)]. The content of the benzimidazolium iodide salt was increased to about 90% by dissolving PDMBI (30%) in dimethyl sulfoxide (DMSO) and re-treating with excess iodomethane at 80°C overnight. The modified PBI polymers were characterized by NMR and FTIR. The modified PBI differed in solubility from PBI. PMMBI could be easily dissolved in NMP and PDMBI in DMSO at room temperature. The solution of PDMBI could be mixed with water in all proportions without precipitation. PDMBI could be also dissolved directly in a mixture of DMSO and water (1 : 1). Typical polyelectrolyte behavior of viscosity was found in solution of PDMBI (30%) and PDMBI (90%) when DMSO and a mixture of DMSO and water were used as solvents. A salt effect on viscosity was also found in the mixed solvent solution. Thermogravimetric analysis (TGA) showed that the methyl group on the imidazole ring was unstable above 180°C under nitrogen. When PDMBI was heated under nitrogen, one of the methyl groups was lost with the counterion to result in a neutral PMMBI. © 1993 John Wiley & Sons, Inc. 相似文献
998.
Martina Nveke Peter G. Jones Armand Blaschette Dietmar Schomburg Heiko K. Cammenga Matthias Epple 《无机化学与普通化学杂志》1993,619(6):1027-1036
Polysulfonyl Amines. XLI. A Silver(I) Hydrate with an Unusual Composition: Characterization of Tetrakis(dimesylamido)aquatetrasilver(I) [Ag4(N)SO2CH3)2}4(H2O)] by X-Ray Diffraction and Thermal Analysis The title compound is obtained by crystallizing AgN(SO2CH3)2 from water at room temperature. Crystallographic data (at ?95°C): Triclinic space group P1 , a = 864.6(4), b = 1 211.2(5), c = 1 399.1(5) pm, α = 90.97(3), β = 90.90(3), γ = 98.25(4)°, V = 1.4496 nm3, Z = 2, Dx = 2.608 Mg m?3. The four independent silver atoms and the water molecule form zigzag chains Ag(1)-Ag(2)-(μ-H2O)-Ag(3) …? Ag(4) …? Ag(1′) with distances Ag(1)-Ag(2) 309.7, Ag(2)-O(w) 241.8, O(w)-Ag(3) 241.4, Ag(3) …? Ag(4) 342.9, Ag(4) …? Ag(1′) 361.4 pm. The catenated silver atoms are further connected by the dimesylamide anions acting as tridentate bridging (α-O, N, ω-O)-ligands. The resulting strands are interconnected into layers through one O(S)-Ag′ contact (247 pm) and one hydrogen bond O(w)-H(l) …? O′(S) per repeating unit. Between the layers, a weak O(S) …? Ag″ interaction (271 ptn) and a hydrogen bond O(w)-H(2) …? O(S) per repeating unit are observed. The silver atoms Ag(l) to Ag(4) display the coordination numbers 5 [NO,Ag(2), distorted trigonal bipyramid], 5[NO2,O(w)Ag(I), distorted trigonal bipyramid], 5[O4,O(w), trigonal bipyramid], and 2 + 1 (N2, li-near; plus a secondary Ag …? 0 contact). The dehydration of the title compound and a solid-solid phase transformation in anhydrous AgN(SO2CH3)2, were quantitatively investigated by thermoconductometry and time- and temperature-resolved X-ray diffractometry (TXRD). 相似文献
999.
Summary Procedures were developed for the preparation of the 2-, 3-, 4-, and 6-monosubstituted chloro and bromo 8-quinolinols which afforded greater yields and/or reduced the number of steps in the preparation. 100 MHz1H-NMR spectra for the 12 possible monochloro and monobromo analogues are given.
Verbesserte Synthese von Monochlor- und Monobrom-8-chinolinolen
Zusammenfassung Es wurden Verfahren entwickelt, um 2-, 3-, 4- und 6-Chlor bzw. -Brom-8-chinolinole in besseren Ausbeuten und/oder bei reduzierter Anzahl von Synthesestufen herzustellen. Die1H-NMR-Spektren der 12 möglichen Monochlor- und Monobromverbindungen werden angegeben.相似文献
1000.
A. V. Shastin T. I. Godovikova B. L. Korsunskii 《Chemistry of Heterocyclic Compounds》2003,39(8):1037-1040
Acylation of 2,4,6-tris(tert-butoxycarbonylmethyl)-1,3,5-triazine with acetic anhydride in the presence of lithium hydride with subsequent removal of the tert-butoxycarbonyl groups with trifluoroacetic acid leads to 2,4,6-tris(acetonyl)-1,3,5-triazine, the cyclic analog of -cyanoacetone. The special spectral features of this compound compared with triazines obtained previously are discussed. 相似文献