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241.
Summary In this paper, we extend recent work of one of us [Br] to investigate an old problem of the other one [B2]. Given a connected semisimple complex Lie-groupG with Lie-algebrag, we study the representation
of the enveloping algebra of
by global differential operators on a complete homogeneous spaceX=G/P. It turns out that the kernelI
x
of
X
is the annihilator of a generalizedVerma-module. On the other hand, we study the associated graded ideal grI
x
, and relate it to the geometry of a generalizedSpringer-resolution, that is a map
of the cotangent-bundle ofX onto a nilpotent variety in
, as studied e.g. in [BM1]. We prove, for instance, that grI
x
is prime if and only if
X
is birational with normal image. In general, we show that
is prime. Equivalently, the associated variety ofI
x
in
is irreducible: In fact, it is the closure of theRichardson-orbit determined byP. For the homogeneous spaceY=G/(P, P), we prove that the analogous idealI
y
has for associated variety the closure of theDixmier-sheet determined byP. From this main result, we derive as a corollary, that for any module induced from a finitedimensional LieP-module the associated variety of the annihilator is irreducible, proving an old conjecture [B2], 2.5. Finally, we give some applications to the study of associated varieties of primitive ideals. 相似文献
242.
Gerhard Wendlberger Liljana Mladenova-Orlinova Walter Göhring Regina Scharf Erich Wünsch 《Monatshefte für Chemie / Chemical Monthly》1981,112(11):1297-1312
The synthesis of the tetratriacontapeptide amide corresponding to the revised primary structure of human big gastrin I is described. For this purpose the fragments were designed in view of the maximum use of those utilized in our previous synthesis of human big gastrin I according to the first sequence proposal. Consequently the key tripeptide-Pro-Pro-His- (sequence 7–9) was prepared in suitably protected form to be used as amino or carboxyl component for assembly of the segments 1–9 and 1–14, respectively. Final condensation of the latter nona- and tetradecapeptide derivatives with the C-terminal segments 10–34 and 15–34 via the azide and the dicyclohexylcarbodiimide/N-hydroxysuccinimide procedure, respectively, leads to crude fully protected human big gastrin I. Upon deprotection by exposure to trifluoroacetic acid in presence of ethanedithiol-(1,2) as scavanger, ion exchange chromatography and partition chromatography, the desired tetratriacontapeptide amide was isolated in satisfactory yield with a high degree of purity. The identical immunological behaviour of the synthetic material, if compared with that of natural human big gastrin I, represents ulterior strong evidence for the correctness of the newly proposed structure for this putative prohormonal form of the gastrins.
Kurzmitteilung:Wünsch E., Wendlberger G., Mladenova-Orlinova L., Göhring W., Jaeger E., Scharf R., Gregory R. A., Dockray G. J., Hoppe-Seyler's Z. Physiol. Chem.362, 179 (1981). 相似文献
243.
Max F. Bechtold Walter Mahler Robert A. Schunn 《Journal of polymer science. Part A, Polymer chemistry》1980,18(9):2823-2855
Linear relationships among molecular weight, polymerization time, and gelation for the condensation of any monomer, including those of unknown size and functionality, are developed and applied to data on soluble silicic acids generated from tetraethyl silicate and from sodium silicate. The results suggest the formation of monomers containing ca. 12–15 ? OSi units with functionality of ca. 2.05 that condense with a rate constant of ca. 10?4 liter/mole sec and an activation energy of 40–70 kJ/mole. One model compatible with these characteristics and the stoichiometry involved is a ladder polymer ca. 3 ? SiO units wide. Polymer isolation was achieved by replacing residual ? OH with (CH3)3Sio? , as well as by freezing of of aqueous solutions, which yielded fibers under special conditions. Solutions of the uncapped and capped polymers and melts of the latter had low viscosity even for fractions with M?n ~100,000. This implies a coiled or globular nature for the polymers, which is supported by their limited propensity for film and fiber formation. Attemps to improve this situation by copolymerization, the use of other capping agents, and by the polymerization of precapped monomers were unsuccessful. 相似文献
244.
Formation of 4-, 5- and 6-membered heterocycles by ambidoselective cyclization of enolate anions N-Acylmethyl-N-chloracetyl-2,6-dimethylanilines 4 were cyclized with base to 4-, 5- or 6-membered ring compounds, depending on the substituent R2 (Scheme 2). All products can be rationalized as derived from the intermediate enolate anions a and b . The enolate anion a reacts by intramolecular alkylation to yield either 1, 4-oxazines 5 or azetidines 6 (Schemes 1, 3 and 7). The regioselectivity observed is expected on the basis of the allopolarization principle. The enolate anion b reacts only with formation of a new C? C bond (Scheme 5). Comparison with the behaviour of the 2, 6-unsubstituted anilines 9, 1a and 12 , shows a strong dependence not only on electronic but also on steric factors (Scheme 4 and 6). 相似文献
245.
Walter Nielsch und Gerhard Böltz 《Fresenius' Journal of Analytical Chemistry》1954,143(3):168-172
Zusammenfassung Es wird gezeigt, daß die Bestimmung des Wismuts mit Thioharnstoff in bromwasserstoffsaurer Lösung auf photometrischem Wege mit dem Gerät ELKO II durchgeführt werden kann. Hierbei benutzt man zweckmäßig das Gerät mit der Glühlampe und Filter S 47 E oder den Quecksilberbrenner in Verbindung mit Filter Hg 436. Damit die Extinktion des gelbgefärbten Komplexes von der Thioharnstoffkonzentration unabhängig wird, muß die Lösung bei Benutzung des Filters S 45 E mindestens 10% Thiohamstoff, bei Benutzung des Filters Hg 436 mindestens 5% Thioharnstoff enthalten. Auch die Bromwasserstoffsäure übt einen Einfluß auf die Ausbildung der Extinktion aus. Wenn man die Messung mit dem Filter S 45 E durchführt und den Thioharnstoffgehalt mit 12% konstant hält, so darf die Bromwasserstoffkonzentration zwischen 1,2–9,2% betragen, um gleichbleibende Extinktionswerte zu erhalten. Benutzt man das Filter Hg 436 bei der gleichen Thioharnstoffkonzentration, so muß der Bromwasserstoffgehalt zwischen 3,0–7,5% liegen. Die Temperatur übt nur einen geringen Einfluß auf die Ausbildung des ThioharnstoffWismutkomplexes aus. Die Extinktion ist zeitunabhängig. Die Extinktionswerte ändern sich innerhalb 3 Std nach Zusammengeben der Reagenslösungen nicht. Das BEERsche Gesetz ist erfüllt. Das Verfahren besitzt erhebliche praktische Bedeutung, da sich sehr viele Metalllegierungen in denen Wismut zu bestimmen ist, mit Hilfe von Bromwasserstoffsäure und Brom sehr schnell lösen lassen. 相似文献
246.
Summary Quantitation of camphechlor/toxaphene in biological matrices like cod-liver oil or fish is difficult because it is a very complex mixture of alicyclic polychlorinated compounds. Furthermore, many toxaphene components are biotransformed and photodegraded and the complex mass spectral fragmentation pattern of HRGC/MSD (electron impact (EI)) cannot be used for quantitation at the g/g-level or below. The use of several indicator-peaks after ECD-detection using the technical standard mixture for calibration does not characterize the entire pattern in a biological sample. Two averaging integration methods that are based on the entire HRGC/ECD-pattern of toxaphene compounds after separation from the PCB congeneres by adsorption chromatography on silicagel, allow a fast and accurate quantitation of the mixture in biological samples, e.g. cod-liver oil. Biological degradation does not disturb the determination because the whole pattern of the complex mixture is considered instead of only a few compounds of the parent mixture which could be degraded or not. 相似文献
247.
Peter Kremminger Walter Weissensteiner 《Monatshefte für Chemie / Chemical Monthly》1991,122(6-7):571-576
Summary The optically active sexidentate Schiff bases [H3
L
5] and [H3
L
6] were prepared from tris[(S)-2-aminopropyl]amine and 5-chlor- and 5-isopropylsalicylaldehyde, respectively. Reaction of rhodium trichloride with [H3
L
6] gave an enantiomerically pure [RhL
6] complex with an absolute configuration of for the octahedral arrangement. The chiroptical properties are given.
Synthese, stereochemische Charakterisierung und Absolutkonfiguration enantiomerenreiner Komplexe sechszähniger Liganden (Kurze Mitt.)
Zusammenfassung Ausgehend von Tris[(S)-2-aminopropyl]amin und 5-Chlor- beziehungsweise 5-Isopropylsalicylaldehyd wurden die optisch aktiven sechszähnigen Schiffschen Basen [H3 L 5] und [H3 L 6] hergestellt. Die Umsetzung von Rhodiumtrichlorid mit [H3 L 6] ergab einen enantiomerenreinen Komplex [RhL 6] mit einer Absolutkonfiguration von für die oktaedrische Anordnung des Liganden. Die chiroptischen Eigenschaften werden angegeben.相似文献
248.
Walter T. Smith John M. Patterson Albert C. Kovelesky 《Journal of heterocyclic chemistry》1990,27(3):549-550
Nitration of naphtho[2,3-c][1,2,5]thiadiazole gives the 5-nitro derivative in 61–66% yield. Chlorination of this product apparently gives an unstable addition product which loses hydrogen chloride on recrystallization to give 4-chloro-8-nitronaphtho[2,3-c][1,2,5]thiadiazole. Thus, naphtho[2,3-c][1,2,5]thiadiazole under nitrating conditions behaves as a 2-substituted naphthalene rather than as an anthracene analog. 相似文献
249.
250.
Zhong Q Han X He L Beesley TE Trahanovsky WS Armstrong DW 《Journal of chromatography. A》2005,1066(1-2):55-70
Chiral stationary phases (CSPs) based on polymeric (R,R)- or (S,S)-1,2-diaminocyclohexane (DACH) derivatives are synthesized. When bonded to 5 microm porous spherical silica gel, the poly (trans-1,2-cyclohexanediyl-bis acrylamide) based poly-cyclic amine polymer (P-CAP) stationary phases is proved to be effective chiral stationary phases that could be used in the normal-phase mode, polar organic mode and with halogenated solvents mobile phases, if desired. Since these are entirely synthetic CSPs, the elution order of all enantiomers can be reversed between the (R,R) P-CAP and (S,S) P-CAP columns. Because of the high loading of chiral selectors, the columns exhibit very high sample capacities. Thus, P-CAP columns are useful for preparative and semi-preparative enantiomeric separations. The application of these CSPs and optimization of their separations are discussed. 相似文献