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101.
Stefaan Cottenier Veerle Vanhoof Doru Torumba Valerio Bellini Mehmet Çakmak Michel Rots 《Hyperfine Interactions》2004,158(1-4):9-18
For some years already, ab initio calculations based on Density Functional Theory (DFT) belong to the toolbox of the field of hyperfine interaction studies.
In this paper, the standard ab initio approach is schematically sketched. New features, methods and possibilities that broke through during the past few years
are listed, and their relation to the standard approach is explained. All this is illustrated by some highlights of recent
ab initio work done by the Nuclear Condensed Matter Group at the K.U.Leuven. 相似文献
102.
Kree Cole-McLaughlin Herbert Edelsbrunner John Harer Vijay Natarajan Valerio Pascucci 《Discrete and Computational Geometry》2004,32(2):231-244
Given a Morse function f over a 2-manifold with or without boundary,
the Reeb graph is obtained by contracting the connected components
of the level sets to points.
We prove tight upper and lower bounds on the
number of loops in the Reeb graph
that depend on the genus, the number of boundary components,
and whether or not the 2-manifold is orientable.
We also give an algorithm that constructs the Reeb graph in time
O(n log n), where n is the number of edges in the
triangulation used to represent the 2-manifold and the Morse function. 相似文献
103.
Giuliana Biagi Irene Giorgi Oreste Livi Valerio Scartoni Silvia Velo Antonio Lucacchini Generoso Senatore Pier Luigi Barili 《Journal of heterocyclic chemistry》1995,32(1):169-176
Several new 1,2,3-triazolo[4,5-b][1,4]diazepines were prepared starting from 1-benzyl-1 and 1-phenethyl-4,5-diamino-1,2,3-triazole 2 (Scheme 1), by condensation reactions with β-diketones (Scheme 2), β-ketoesters (Scheme 3), and diethyl malonates (Scheme 4). In the first case we obtained compounds 3 and 4 with basic properties, while the ester function condensations gave cyclic amide derivatives 7, 8, 10, 12 and 13 with acid properties. Some N-methyl derivatives 11, 14 and 15 were obtained from the cyclic amide compounds. Most of compounds were tested for their ability to displace [3H]flunitrazepam from bovine brain membranes but no compound showed benzodiazepine receptor binding affinity. 相似文献
104.
Giuliana Biagi Irene Giorgi Oreste Livi Antonio Nardi Valerio Scartoni 《Journal of heterocyclic chemistry》2002,39(6):1293-1298
Four new triazolylbenzimidazolthione derivatives (2a‐d), analogous to triazolylbenzimidazolone derivatives previously tested as activators of the BKCa potassium channels, were prepared and assayed without success. Some derivatives of a new tricyclic nitrogen heterocycle, 1,2,3‐triazolo[1,5‐a][1,3,5]benzo‐triazepine, bearing a carboxamido group in the 3 position, other substituents in the 8 position and a carbonyl (5a‐d) or thione (6a‐c) or methylthio (7a‐c) function in the 5 position were synthesised. The nucleophilic displacement of the methylthio substituent with morpholine or cyclopentylamine provided the 5‐amino‐substituted tricyclic derivatives 8a‐d. Starting from the l‐(2‐nitrophenyl)‐4‐cyano‐5‐amino‐1,2,3‐triazole (9), the 3‐cyano‐triazolobenzotriazepin‐5‐one derivative 12 was also obtained. The majority of the new compounds were tested towards the BKCa potassium channels, the benzodiazepine and adenosine A1 and A2a receptors, but no remarkable activity was detected. 相似文献
105.
We analyse the overall birefringence which arises from the combined effects of Faraday rotation (non-reciprocal) and bending stress (reciprocal) applied to a monomode optical fibre loop. The theory is substantiated by numerical evaluations and appropriate experimental data are reported. These indicate how it is possible to build non-reciprocal birefringent components, i.e. rotators and isolators, by means of monomode coils. 相似文献
106.
Marek L. Główka Henryk Krawczyk Ryszard Bodalski Valerio Bertolasi 《Journal of chemical crystallography》1989,19(4):701-705
The crystals (C16H18NO2P,M
r=287.30) are orthorhombic, space group Pbca witha=8.200(2),b=14.857(2), andc=24.396(5)Å,V=2972.1 Å3,Z=8,D
x=1.284 mg m–3,(MoK)=0.71069 Å,=1.90 cm–1,F(000)=216,T=295K. FinalR=0.044 for 1673 observed reflections collected on a diffractometer. Structure solved by direct methods.Cis-junction and double bond in the six-membered ring cause its almost ideal sofa conformation. The two neighboring methyl groups are cis, and cyano substituent is in an equatorial position. There is a shortintramolecular H(o-phenyl)O(endocyclic) contact of 2.53(3)Å and the phenyl ring is in a less favorable rotational orientation due to molecular packing. 相似文献
107.
C-Galactosyl and C-ribosyl β-amino acids were prepared by one-pot InCl3-catalyzed Mannich-type three-component condensation (3CC) by combining the corresponding formyl C-glycoside, p-methoxybenzyl amine, and a ketene silyl acetal. In each case the reaction was highly stereoselective and afforded only one single product in good to excellent yields. 相似文献
108.
Sandro Calogero Paolo Ganis Valerio Peruzzo Giuseppe Tagliavini 《Journal of organometallic chemistry》1980,191(2):381-390
The halogenocarboxylates (cyclo-C6H11)3SnO2CR′, (R′ = CH3, CH2Cl, CHCl2, CCl3 and CF3) have been prepared, and characterized by Mössbauer and IR spectroscopy. The crystal structure of (cyclo-C6H11)3SnO2CCF3 has been determined by X-ray analysis. The crystals are orthorhombic, space group Pcmn, with unit cell parameters a 14.390 ± 0.004, b, 13.427 ± 0.004, c 11.516 ± 0.003 Å. The structure was resolved by Patterson methods and refined to an R value of 0.147. The coordination about the tin atom can be considered distorted trigonal-pyramidal or distorted tetrahedral. Mössbauer data are explained in terms of distortions of bond angles about the tin atom. 相似文献
109.
Ulderico Mazzi Edoardo Roncari Roberto Rossi Valerio Bertolasi Orazio Traverso Luciano Magon 《Transition Metal Chemistry》1980,5(1):289-293
Summary The reactions of ReOX3(PPh3)2 (X = CI or Br) withN-methylsalicylideneimine (Me-saIH),N-phenylsalicylideneimine (Ph-saIH),N,N-ethylenebis(salicyli(leneimine) [(SaIH)2en] and 8-hvdroxyquinoline (Oxinell) are here reported. They give rise to the ReOX2(Me-sal)PPh2. ReOX-(Me-sal)2, ReOX2(Ph-sal)PPh3, ReOX(Ph-sal),, Re2O2X4-(Sal2en)(PPh3)2, ReOX2(Oxine)PPh, and ReOX(Oxine)2 complexes. 相似文献
110.
Giuliana Biagi Irene Giorgi Oreste Livi Federica Pacchini Valerio Scartoni Oreste Leroy Salerni 《Journal of heterocyclic chemistry》2004,41(4):575-580
A suitably substituted pyrimidine 1 was converted to a number of title compounds. Nucleophilic substitu tion involving the chlorine atoms in 1 by treatment with phenylmethanethiol yielded 2 or 3 , depending on the reaction temperature. Treatment of 3 with an amine afforded 6‐phenylmethanesulfanyl‐N4‐substituted‐2‐phenyl‐pyrimidine‐4,5‐diamines 4–7 . These pyrimidines were converted into 2‐phenylpurines 8–11 and 2‐phenyl‐8‐azapurines 12–14 , by treatment with triethyl orthoformate in the presence of hydrochloric acid (or acetic anhydride), or with potassium nitrite and acetic acid respectively. The thioether function on C(6) was then converted into a sulfonyl group by oxidation with m‐chloroperoxybenzoic acid affording purines 15–18 and their 8‐azaanalogs 19–21 ; these compounds, as crude products, were treated with an amine to yield the corresponding adenines 22–25 or 8‐azaadenines 26–31. All reactions were performed under conditions com patible with the possible use of a thiomethyl resin in place of phenylmethanethiol to bind the pyrimidine ring of 1 to a solid phase. 相似文献