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11.
The successive reaction of (CO)6M with Na[NCR21] and [Et3O]BF4 yields (CO)5M[C(NCR21)OEt] (II: M = Cr; III: M = W; CR21 = C(C6H4Br-p)2 (a), CPh2 (b), C(C6H4OMe-p)2 (c), C(C6H4)2O (d), CBu2tt (e)). Hexacarbonyltungsten, (CO)6W, reacts with Na[NCPh2] and MeOSO2F to give (CO)5W[C(NCPh2) OMe] (IV). X-Ray analysis of IIe shows that: (1) the CNC fragment is almost linear (171.7°); (2) the two NC bond lengths are equal within experimental error; and (3) the O,C,Cr,N plane is perpendicular to the C(Me3),C,N,C(Me3) plane (90.0°). Therefore compounds II–IV are best described as 1-alkoxy-2-azaallenyl complexes. 相似文献
12.
The new hexaalkylborazine chromium tricarbonyls (n-Pr)3B3N3Me3Cr(CO)3 (V), Me3B3N3(n-Pr)3Cr(CO)3 (VI), (i-Pr)3B3N3Me3Cr(CO)3 (VII) and Me3B3N3(i-Pr)3Cr(CO)3 (VIII) have been prepared from fac-Cr(CO)3(MeCN)3 and the corresponding borazine in dioxane or without solvent. They are much more labile than the isomeric complex Et3B3N3Et3Cr(CO)3 (IV) which can be readily obtained from Et3B3N3Me3Cr(CO)3 and Et3B3N3Et3 by ring ligand exchange. The NMR., IR., UV. and Mass spectroscopic data of the complexes IV–VIII will be briefly discussed. The preparation of the borazine derivatives (n-Pr)3B3N3Me3 (IX) and Me3B3N3(n-Pr)3 (X) is also reported. 相似文献
13.
The electron-impact fragmentation of S-p-tolylester of nitrothiobenzoic acid leads to a previously unknown rearrangement in the case of the ortho compound. This consists of an intra molecular redoxreaction with oxygen transfer from the o-nitro group onto the sulphur of the thiol ester group. The position of the nitro group is not only an essential influence on the fragmentation pattern, but also of dramatic importance in determining the lifetime of the molecular ion. 相似文献
14.
Zusammenfassung Die Elektronenstrukturen von Bis-durochinon-nickel(0) und der Komplexe vom Typ Olefin-Ni(0)-Chinon werden im Rahmen der LCAO-MO-Näherung diskutiert und zur Deutung der Absorptionsspektren herangezogen. Den im freien Durochmon auftretenden Übergängen lassen sich in den Komplexspektren jeweils nur wenig verschobene Banden zuordnen. Darüber hinaus wird eine intensive Charge-Transfer-Bande beobachtet, die einem Übergang vom höchsten besetzten Nickelzustand zum tiefsten unbesetzten Chinon-Orbital entspricht. Aus der Intensität der Bande, die im freien Chinon dem b
3g
2b
2
g-Übergang zugeordnet wird, ergibt sich für das gelöste Bis-durochinon-nickel(0)-Molekül die Symmetrie D
2h
. Während die Komplexe mit Durochinon in Übereinstimmung mit der Theorie diamagnetisch sind, weisen die analogen Verbindungen der Dimethylchinone magnetische Momente von 1,52 bzw. 2,75 B. M. auf, woraus auf eine Mitbeteiligung polarer Strukturen am Grundzustand dieser Komplexe geschlossen wird.
6. Mitteilung über Komplexe vom Typ des Bis-durochinon-nickel(0). 5. Mitt. vgl. [11]. 相似文献
The electronic structures of bis-duroquinone-nickel(0) and complexes of the type olefine-Ni(0)-quinone are discussed in the MO-LCAO approximation and used for an interpretation of the absorption spectra. The transitions of the free duroquinone can be correlated with transitions of the complexes at nearly the same wavelengths. In addition, an intense charge transfer band is observed which corresponds to a transition from the highest occupied nickel orbital to the lowest unoccupied quinone orbital. From the intensity of the band which corresponds to b 3g 2b2g in the free quinone, the symmetry D 2h for the dissolved bis-duroquinone-nickel(0) molecule is deduced. Whereas the duroquinone complexes are diamagnetic in agreement with theory, analogous compounds of the diméthylquinones exhibit magnetic momenta of 1.52 and 2.75 B. M. suggesting the participation of polar structures in the ground state of these complexes.
Résumé Les structures électroniques du bis-duroquinone-nickel(0) et des complexes du type oléfine-Ni(0)-quinone sont discutées dans le cadre del'approximationMO-LCAO et utilisées pour l'interprétation des spectres d'absorption. Aux transitions de la duroquinone libre peuvent être attribuées des bandes peu déplacées dans les spectres des complexes. En outre on observe une bande intense correspondant à une transition de la plus haute orbitale occupée du nickel à la plus basse orbitale libre de la quinone. L'intensité de la bande nommée b 3g 2b 2g dans la quinone libre indique la symétrie D 2h pour la molécule dissoute du bis-duroquinone-nickel(0). Tandis que les complexes de la duroquinone sont diamagnétiques en accord avec la théorie, des composés analogues des diméthylquinones présentent des moments magnétiques de 1,52 et de 2,75 B. M. d'où l'on infère la participation de structures polaires à l'état fondamental de ces complexes.
6. Mitteilung über Komplexe vom Typ des Bis-durochinon-nickel(0). 5. Mitt. vgl. [11]. 相似文献
15.
Helmut Schweppe 《Analytical and bioanalytical chemistry》1975,276(4):291-296
A simple method of identifying the more important natural dyes that have found widespread use for dyeing textiles is described. This involves thin-layer chromatographic comparison on Mikropolyamid F 1700 (Schl. & Sch.). The reliability of dye recognition is increased by combining various methods of identification on the chromatogram by employing the following procedure: (1) The normal coloration, (2) the fluorescent colour in UV light, (3) the change in shade with ammoniacal steam, and (4) the colour reaction with aluminium salts or, where hydroxyflavones have already been identified by reaction (3), with iron(III) chloride. In addition, various specific reactions for identifying individual natural colours are given. Furthermore, methods are indicated whereby identification can be effected by comparing infra-red spectra after a simple preparation of the sample. 相似文献
16.
Hans Weidmann Hanns Wolf Oberwalder Egon Wildschek Helmut Schwarz 《Monatshefte für Chemie / Chemical Monthly》1972,103(1):210-217
Zusammenfassung Durch acylierende Dehydratisierung von 1,2-Isopropyliden-d-xylo-und-d-ribo-pentodialdo-furanoseoxim bzw. aus Furanuronsäureestern und-amiden werden über eine Reihe von Zwischenstufen verschiedene 3-O-Acyl-pentofuranuronsäurenitrile synthetisiert und deren Reaktionen untersucht.
Mit 1 Abbildung
Aus den DissertationenH. W. Oberwalder (1970) undE. Wildschek (1967), Technische Hochschule in Graz. 相似文献
Synthesis of xyluronic and riburonic acid derivatives
Various 3-O-acyl-pentofuranurononitrils were synthesized by acylating dehydration of 1,2-isopropylidene-d-xylo- andd-ribo-pentodialdo-furanose oximes, or pentofuranuronic acids via intermediates. Their reactions were investigated.
Mit 1 Abbildung
Aus den DissertationenH. W. Oberwalder (1970) undE. Wildschek (1967), Technische Hochschule in Graz. 相似文献
17.
Bis-(2,4,5-triphenylimidazolyls) result from the dimerization of 2,4,5-triphenylimidazolyls and from the nucleophilic attack of 2,4,5-triphenylimidazole anions upon 2,4,5-triphenylimidazolylium cations. The isomeric bis-imidazolyls consist of imidazole and isoimidazole systems. Imidazoles undergo only anodic oxidation, isoimidazoles only cathodic reduction. Therefore the bis-imidazolyls may be analyzed from their electrochemical behaviour. Bis-(2,4,5-triphenylimidazolyl)-1,2′ and bis-(2,4,5-triphenylimidazolyl)-1,4′ undergo reductive bond cleavage in an ē.c?.ē. mechanism from which 2,4,5-triphenyl-imidazole anions result. The electrochemical properties of one of the bis-imidazolyls agree with that of 1,4,5-triphenyl-2-(2,4,5-triphenylisoimidazolyl-4)-imidazole and not with that of bis-(2,4,5-triphenylimidazolyl)-2,4′ as reported in literature. 相似文献
18.
Helmut Meyn 《Designs, Codes and Cryptography》1995,6(2):107-116
For an odd prime powerq the infinite field GF(q
2 )=
n0 GF (q
2n
) is explicitly presented by a sequence (f
n)1 ofN-polynomials. This means that, for a suitably chosen initial polynomialf
1, the defining polynomialsf
nGF(q)[x] of degrees2
n are constructed by iteration of the transformation of variablexx+1/x and have linearly independent roots over GF(q). In addition, the sequences are trace-compatible in the sense that the relative traces map the corresponding roots onto each other. In this first paper the caseq1 (mod 4) is considered and the caseq3 (mod 4) will be dealt with in a second paper. This specific construction solves a problem raised by A. Scheerhorn in [11]. 相似文献
19.
We give a necessary and sufficient condition for a Bell-type inequality to hold in a horizontal sum of finitely many finite Boolean algebras. 相似文献
20.
Motivated by the concept of maximum entropy methods in signal and image processing, we introduce and discuss a class of ‘directed diffusion equations’ with suitable boundary conditions. The paradigmatic ‘directed diffusion equation’ is The relative entropy $ Sb[f](t): = - \int_\Omega {f(t,x)} \;\ln \;(f(t,x)/b(x))dx $ is rapidly increasing along solution trajectories of (i). This suggests that solving (i) will yield efficient procedures for entropy maximization. We also discuss the asymptotic behavior of solutions of (i)—this is readily done because (i) has a large family of Ljapunov functionals. 相似文献