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111.
Pierre-Luc Girard-Lauriault Juan-Carlos Ruiz Thomas Gross Michael R. Wertheimer Wolfgang E. S. Unger 《Plasma Chemistry and Plasma Processing》2011,31(4):535-550
Nitrogen (N)-rich organic thin films were deposited using both low-pressure plasma- and vacuum-ultraviolet-based techniques, from mixtures of ammonia (NH3) and ethylene (C2H4). These films were investigated using angle-resolved and excitation energy resolved X-ray photoelectron spectroscopy (ARXPS and ERXPS, respectively) in order to determine their sub-surface chemical profiles. These two techniques enable one to tune the ??XPS 95%?? information depth, z 95%, by varying either the angle or the excitation energy. Using a combination of both techniques, z 95% can be varied continuously from 0.7 to 11 nm. The surface-near chemistry is investigated using both high-resolution C 1s spectra and elemental concentrations derived from elemental peak intensities. Results show that while laboratory XPS, and even ARXPS, suggest homogenous surface chemistries, the novel combination of ARXPS and ERXPS points to the existence of a compositional profile in the extreme outer surface layer. Our conclusions are supported by simulations using SESSA software. 相似文献
112.
113.
Amino acids are studied extensively using capillary electrophoresis. In a previous article, we reviewed applications reported in the period 1999-early 2001 (Prata, C., Bonnafous, P., Fraysse, N., Treilhou, M., Poinsot, V., Couderc, F., Electrophoresis 2001, 22, 4129-4138). In this article we follow on with this review for the period end of 2001-beginning of 2003. We will report the developments of detection methods, separations of enantiomers, the new medical applications, and amino acids in food and plants. This review shows that CE is more and more important for the amino acid analysis. 相似文献
114.
Anne-Sophie RebstockFlorence Mongin François TrécourtGuy Quéguiner 《Tetrahedron》2003,59(27):4973-4977
The ring deprotonation of 2-(2- and 4-pyridyl)benzoic acids using lithium dialkylamides in THF at rt, and the in situ cyclization afforded 4- and 2-azafluorenones, respectively. 1-Azafluorenone was obtained from ethyl 2-(3-pyridyl)benzoate using a similar protocol. 相似文献
115.
From bergamot oil (Citrus bergamia RISSO), (?)-(4S, 8R)-8-epi-α-bisabolol ( 2 ) and (?)-(4R, 8S)-4-epi-β-bisabolol ( 3 ) were isolated. The absolute configuration of their stereoisomers 4 and 5 was established by an enantioselective synthesis starting from (?)-(S)-p-mentha-1,8-dien-4-ol. 相似文献
116.
117.
Jean -François Labarre Marcel Graffeuil Jean -Paul Faucher Maurice Pasdeloup Jean -Pierre Laurent 《Theoretical chemistry accounts》1968,11(5):423-433
Résumé Une utilisation conjointe des méthodes L.C.A.O.-C.U.V. et d'itération tournante permet d'atteindre des structures électroniques ( + ) cohérentes avec l'U.V.(et donc le gradient de population électronique de liaison qui conditionne l'aromaticité) de huit borazines et boroxines, substitués ou non, de symètrie D
3h
. L'échelle d'aromaticité obtenue permet de rendre compte des propriétés magnétiques (RMN, RQ, effet Faraday, diamagnétisme) de ce type de molécules. On parvient en particulier aux deux conclusions essentielles suivantes: les borazines sont nettement plus aromatiques que les boroxines isologues et la greffe de groupements méthyles ou d'atomes de chlore, qu'elle se fasse sur le bore ou sur l'azote, confère toujours au dérivé substitué une aromaticité au moins égale à celle du borazine lui-même.
Recherche effectuée dans le cadre de la R.C.P. n du C.N.R.S. 相似文献
A simple method to calculate the - and -electron structure of borazines and of substituted boroxines of symmetry D3h: A theoretical estimation of the relative aromaticity of those molecules
( + ) electronic structures calculations are performed for eight D 3h borazines and boroxines, using in concert previously published U.V.-consistent H.M.O.-L.C.A.O. and bond by bond iteration methods. An estimation of bond electronic populations gradients is so obtained, allowing to set up a new aromaticity scale for such molecules. The main results are the following: Borazines are much more aromatic than isologous boroxines and B-or N-graft of alkyl groups or chlorine atoms never decreases (and generally increases) aromaticity.
Zusammenfassung Es wird für acht Borazol- und Boroxolverbindungen mit D 3h -Symmetrie unter Verwendung einer am UV-Spektrum geeichten iterativen HMO-LCAO-Theorie die - und -Elektronenstruktur bestimmt. Hiermit kann eine Abschätzung des Gradienten der Bindungselektronendichten gewonnen werden, aus der eine Einteilung der Moleküle nach ihrem aromatischen Charakter hervorgeht. Es ergibt sich, daß die Borazole aromatischer sind als die isoelektronischen Boroxole und daß eine Substitution der H-Atome am Bor oder Stickstoff durch Chlor oder Methylgruppen die Aromatizität fast immer erhöht, jedenfalls aber nie erniedrigt.
Recherche effectuée dans le cadre de la R.C.P. n du C.N.R.S. 相似文献
118.
Compound CpMoI2(iPr2dad) (iPr2dad = iPrNCHCHNiPr), obtained by halide exchange from CpMoCl2(iPr2dad) and NaI, has been isolated and characterized by EPR spectroscopy, cyclic voltammetry, and X-ray crystallography. Its action as a catalyst in atom transfer radical polymerization (ATRP) and as a spin trap in organometallic radical polymerization (OMRP) of styrene and methyl acrylate (MA) monomers has been investigated and compared with that of the dichloro analogue. Compound CpMoCl2(iPr2dad) catalyzes the ATRP of styrene and MA with low efficiency factors f (as low as 0.37 for MA and ethyl 2-chloropropionate as initiator), while it irreversibly traps the corresponding growing radical chains under OMRP conditions. On the other hand, compound CpMoI2(iPr2dad) has a greater ATRP catalytic activity than the dichloro analogue and yields f = 1 for MA and ethyl 2-iodopropionate as initiator. Under OMRP conditions, it does not irreversibly trap the growing radical chains. This comparison serves to illustrate the general principle that low initiator efficiency factors, sometimes observed in ATRP, may result from the interplay of the ATRP and OMRP mechanisms, when the latter ones involves an irreversible radical trapping process. 相似文献
119.
Jean M. J. Tronchet Françoise Barbalat-Rey Jeannine F. Tronchet Faranak Raehidzadeh 《Journal of carbohydrate chemistry》2013,32(2):193-204
Replacement of the alkyl group of l-aryl-3-alkyltriazenes with a sugar moiety did not significantly modify their tautomeric behaviour. The same replacement done on 1-aryl-3-alkyl-3-methyl-triazenes did not affect to any large extent their rotameric properties. In contrast, the most prominent biological properties, anticancer activity and toxicity, of 1-aryl-3-methyltria-zenes disappeared on replacement of the methyl group with a sugar moiety. Unexpectedly, the N-acetyltriazene 15 was highly cyto-toxic. 相似文献
120.
Thanks to the successive use of two esterases with different regioselectivities and conventional organic chemistry we have synthesized (1R,2S) and (1S,2S) dehydrocoronamic acids. 相似文献