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991.
I. L. Odinets O. I. Artyushin E. A. Antonov P. V. Petrovskii B. I. Freger T. A. Mastryukova M. I. Kabachnik 《Russian Chemical Bulletin》1994,43(1):121-124
It was shown by31P and13C NMR spectroscopy that methyl(3-carboxy-3-oxopropyl)phosphinic acid (4-methylhydroxyphosphinyl-2-oxobutyric acid) (1) and the amide (2) of the latter exist in keto forms in non-aqueous solutions. In aqueous solutions an equilibrium between the keto,gem-diol, and enol forms has been observed. The proportions of the diol and enol forms increase as the acidity of the media increases. Silylation of acid 1 with hexamethyldisilazane gives the tris(trimethylsilyl) derivative of enol form (3) (Z- andE-isomers).Translated fromIzyestiya Akadetnii Nauk. Seriya Khimicheskaya, No. 1, pp. 125–128, January, 1994. 相似文献
992.
Helmut Pfitzner und Helmut Schweppe 《Fresenius' Journal of Analytical Chemistry》1974,268(5):337-342
Zusammenfassung In einer früheren Veröffentlichung [4] ist auf die Möglichkeit der chromatographischen Trennung strukturisomerer Metallchelate hingewiesen worden; sie soll hier ausführlicher dargestellt werden. Weiterhin wird die Trennung von 1:2-Mischkomplexen von Azofarbstoffen und von 1:2-Metallkomplex-Mischungen durch Dünnschicht-Chromatographie (DC) an Polyamid beschrieben. Unter bestimmten Voraussetzungen kann durch DC an Kieselgel zwischen 1:2-Metallkomplexfarbstoffen mit Sulfonsäureamid- bzw. Alkylsulfongruppen und solchen ohne diese Substituenten unterschieden werden. Die beschriebenen DC-Methoden ermöglichen bei richtiger Interpretation eine eindeutige Unterscheidung zwischen strukturisomeren Metallkomplexen der 1:1- und 1:2-Reihe, sowie Mischkomplexen und Komplexmischungen vom 1:2-Metall-chelattyp unsulfierter o,o-Dihydroxyazoverbindungen.Symmetrische o,o-Dihydroxyazoverbindungen, wie z.B. das 2,2-Dihydroxy-5,5-dimethyl-azobenzol(7), sind geeignete Komplexbildner für Schwermetallkationen, um diese als farbige Chelate mit Hilfe der DC voneinander zu trennen. Strukturisomere sind wegen der Molekülsymmetrie ausgeschlossen, so daß die Ergebnisse eindeutig sind.
1:1 and 1:2 metal chelates of unsulphonated o,o-dihydroxyazo compounds: A thin-layer chromatographic investigation
In an earlier publication [4] the possibility of the Chromatographic separation of structurally isomeric metal chelates was mentioned; this is dealt with here in more detail. Further the separation of 1:2 mixed complexes from azo dyes and 1:2 metal-complex mixtures by thin-layer chromatography (TLC) on polyamide is described. In certain circumstances it is possible to distinguish between 1:2 metal-complex dyes with sulphonamide or alkylsulphonyl groups and those without these substituents by TLC on silica gel. The TCL methods described allow-when correctly interpreted-an unambiguous distinction between structurally isomeric metal complexes of the 1:1 and 1:2 series, and mixed complexes and mixtures of complexes of the 1:2 metal-chelate type of unsulphonated o,o-dihydroxyazo compounds.Symmetrical o,o-dihydroxyazo compounds, such as 2,2-dihydroxy-5,5-dimethylazobenzene(7), are suitable as complex-formers for heavy-metal ions, allowing the separation of the latter as their coloured chelates with aid of TLC. Structural isomers are excluded because of the molecular symmetry, so that the results are unambiguous.相似文献
993.
The initial formation of organotin derivatives with Sn-S-N bonds in heterolytic reactions of hexamethylditin or trimethyltin sulfide withN-(chlorothio)phthalimide is suggested. Subsequent interaction of these compounds with sulfenyl chloride affordsN, N-thioorN, N-dithiobisphthalimide. Homolytic reaction of hexamethylditin withN, N-dithiobisphthalimide also occursvia an organotin intermediate, which, in the absence of a nucleophilic reagent, eliminates sulfur and converts intoN-trimethylstannylphthalimide.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2111–2114, December, 1993. 相似文献
994.
Sevim Akyüz Tanil Akyüz J. Eric D. Davies 《Journal of inclusion phenomena and macrocyclic chemistry》1993,15(2):105-119
The adsorption of 4,4-bipyridyl by natural sepiolite and smectite group clay minerals (bentonite, hectorite and saponite) from Anatolia (Turkey) has been studied using vibrational spectroscopy. Investigation of Fourier-transform infrared and Fourier-transform Raman spectra of adsorbed 4,4-bipyridyl indicate the presence of chemisorbed species. However, any evidence for the generation of anionic species on the surface of the phyllosilicates has not been detected. It is proposed that the adsorbed bipyridyl molecules on sepiolite are centrosymmetric and H-bonded to the surface hydroxyls through both the nitrogen lone pairs as bidentate ligands. The adsorbed bipyridyl molecules on the smectite group clays are coordinated to exchangeable cations both directly and also indirectly through water as monodentate ligands. XRD patterns of the clays studied are also recorded. 相似文献
995.
Ultra-high-molecular-weight polyethylene (UHMWPE) – carbon black (CB) blends were prepared by gelation/ crystallization from
PE dilute solutions containing CB particles. The UHMWPE/CB composition chosen were 1/0.15, 1/0.25, 1/0.5, 1/0.75, 1/1, 1/3,
1/5, and 1/9, etc. The cross-linking of PE chains was performed by chemical reaction of dicumyl-peroxide at 160 °C. X-ray diffraction patterns indicate that the crystallinity of PE within the blends decreased drastically through the chemical
reaction at high temperature. The sample preparation method by gelation/crystallization provided the UHMWPE–CB system with
various CB contents up to 90% and the conductivities for the resultant specimens were in the range from 10-9 to 1 Ω-1 cm-1 corresponding to the electric conductivity range of semiconductors. The blends assured thermal stability of electric conductivity
by cross-linking of PE chains, although the mechanical property such as the storage and loss moduli were very sensitive to
temperature. The conductivity of the blends with CB content ≥20% were almost independent of temperature up to 220 °C and the values in the heating and cooling processes were almost the same. On the other hand, for the UHMWPE–CB blends with
13% CB content corresponding to the critical one, temperature dependence of electric resistivity showed positive temperature
coefficient (PTC) effect. The PTC intensities for non-cross-linked and cross-linked materials were lower than that of the
corresponding low-molecular-weight-polyethylene (LMWPE)–CB blend but the maximum peak appeared at 160 °C which is higher than the peak temperature of LMWPE–CB blend.
Received: 10 December 1997 Accepted: 9 April 1998 相似文献
996.
Y. Marcus 《Journal of solution chemistry》1991,20(9):929-944
Taft and Kamlet's -scale of solvent hydrogen bond donation ability is reexamined with regard to its correlations with three widely used polarity scales: Dimroth and Reichardt's E
T
(30), Kosower's Z and Mayer's A
N
, as well as with the m values of the solvents when present as monomeric solutes. The correlation with E
T
serves to extend the solvent -scale according to the expression:
相似文献
997.
Ab initio calculation of the 4-ClC6H4CH2Cl molecule was performed by the restricted Hartree-Fock method in the split valence 6–31 G* basis set with complete optimization of its geometry. Populations of p-orbitals of atoms of this molecule were analyzed.35Cl NQR frequencies and asymmetry parameters of the electric field gradient on35Cl nuclei were estimated on the basis of the populations of valent p-orbitals of CI atoms and their components. Good conformity with the experimental values was obtained when only less diffuse components of p-orbitals were used in calculations of populations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 823–826, April, 1996. 相似文献
998.
I. I. Ponomarev Yu. Yu. Rybkin E. I. Goryunov P. V. Petrovskii K. A. Lyssenko 《Russian Chemical Bulletin》2004,53(12):2881-2883
The reaction of 4,4-dimethyldiphenyl ether with phosphorus trichloride in the presence of anhydrous aluminum chloride was studied. This reaction affords 2,8-dimethyl-10H-105-phenoxaphosphine 10-oxide as virtually the only product. In air, the latter in an alkaline solution is quantitatively transformed into 10-hydroxy-2,8-dimethyl-10H-105-phenoxaphosphine 10-oxide.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2762–2765, December, 2004. 相似文献
999.
D.?Mitra S.?Francis L.?VarshneyEmail author 《Journal of Thermal Analysis and Calorimetry》2004,78(3):821-829
DSC and TG studies were carried out on -radiation processed Indian natural products of medicinal importance, namely Ashwagandha (Withania Somnifera), Amla (Emblica Officinalis) and Hartiki (Terminalia chebula). DSC thermoanalytical curves were recorded from 35 to 400°C in air and nitrogen atmosphere. Similarly, TG thermoanalytical curves were taken from 35 to 700°C in air and nitrogen atmosphere. Irradiated products gave significantly different thermoanalytical profiles in comparison to non-irradiated samples. The differences were observed above decomposition temperature of 200°C and were non-linear with respect to radiation dose. Partial oxidation of the products during irradiation in air could be responsible for the observed differences. 相似文献
1000.
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