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951.
Mabilia R Di Palo V Cassardo C Ciuchini C Pasini A Possanzini M 《Annali di chimica》2007,97(10):1027-1037
Measurements of gaseous organic compounds were carried out near Ny-Alesund, in the Norwegian Arctic, during September 2004. Twenty alkanes, alkenes and aromatic hydrocarbons from ethane to toluene and six aldehydes and ketones from formaldehyde to butanal, were identified and quantified in air samples. Hydrocarbons showed a quite uniform distribution, with ethane being by far the most abundant component (> 1 ppb), followed by propane (> 0.4 ppb) and butanes (> 0.3 ppb), while for unsaturated homologues, except ethene, concentrations never exceeding 0.05 ppb were observed. This distribution confirmed that hydrocarbon depletion during the transport time from Europe into the Arctic was depending upon their atmospheric lifetimes, calculated relatively to the OH reactivity scale. The presence of short lived hydrocarbons could be associated to local sources of anthropogenic and/or biogenic origin. Although the local air photochemistry played a primary role in the production of lower aldehydes in late summer, the observed mixing ratios of formaldehyde (in the 0.25 - 0.50 ppb range) could not be fully explained by known gas-phase chemistry. In this case additional sources, such as fluxes of formaldehyde from snow pack to the atmosphere and/or local anthropogenic activities, were to be taken into consideration. The possible influences of these sources on HCHO mixing ratios were analysed by means of a backward-trajectory circulation model. 相似文献
952.
Food contamination from natural or anthropogenic sources poses severe risks to human health. It is now largely accepted that continuous exposure to low doses of toxic chemicals can be related to several chronic diseases, including some type of cancer and serious hormonal dysfunctions.Contemporary analytical methods have the sensitivity required for contamination detection and quantification, but direct application of these methods on food samples can be rarely performed. In fact, the matrix introduces severe disturbances, and analysis can be performed only after some clean-up and preconcentration steps. Current sample pre-treatment methods, mostly based on the solid phase extraction technique, are very fast and inexpensive but show a lack of selectivity, while methods based on immunoaffinity extraction are very selective but expensive and not suitable for harsh environments. Thus, inexpensive, rapid and selective clean-up methods, relaying on “intelligent” materials are needed. Recent years have seen a significant increase of the “molecularly imprinted solid phase extraction” (MISPE) technique in the food contaminant analysis. In fact, this technique seems to be particularly suitable for extractive applications where analyte selectivity in the presence of very complex and structured matrices represents the main problem. In this review, several applications of MISPE in food contamination analysis will be discussed, with particular emphasis on the extraction of pesticides, drugs residua, mycotoxins and environmental contaminants. 相似文献
953.
Masciocchi N Pettinari C Alberti E Pettinari R Nicola CD Albisetti AF Sironi A 《Inorganic chemistry》2007,46(25):10501-10509
New polynuclear coordination species containing the ditopic bis(1-imidazolyl)methane (Bim) ligand have been prepared as microcrystalline powders and structurally characterized by ab initio X-ray powder diffraction methods. [Zn(CH3COO)2(Bim)]n contains 1D chains with tetrahedral metal atoms bridged by Bim ligands; [CdBr2(Bim)]n shows a dense packing with hexacoordinated Cd(II) ions and mu-Br and mu-Bim bridges; at variance, the isomorphous [ZnCl2(Bim)]n and [ZnBr2(Bim)]n species contain cyclic dimers based on tetrahedral Zn(II) ions. Thermodiffractometric analysis allowed estimation of the linear thermal expansion coefficients and strain tensors derived there from. Bim-rich phases, with 2:1 ligand-to-metal ratio, were also isolated: ZnBr2(Bim)2(H2O)3 and [Cd(CH3COO)2(Bim)2]n containing cis and trans MN4O2 chromophores, respectively, show 1D polymers built upon M2Bim2 cycles, hinged on the metal ions. In all species the conformation of the Bim ligands is Cs (or nearly so), while in the few sparse reports of similar coordination polymers the alternative C2 one was preferentially observed. 相似文献
954.
Pettinari C Pettinari R Marchetti F Macchioni A Zuccaccia D Skelton BW White AH 《Inorganic chemistry》2007,46(3):896-906
Rhodium(III) and iridium(III) complexes containing bis(pyrazolyl)methane ligands (pz = pyrazole, L' in general; specifically, L1 = H2C(pz)2, L2 = H2C(pzMe2)2, L3 = H2C(pz4Me)2, L4 = Me2C(pz)2), have been prepared in a study exploring the reactivity of these ligands toward [Cp*MCl(mu-Cl)]2 dimers (M = Rh, Ir; Cp* = pentamethylcyclopentadienyl). When the reaction was carried out in acetone solution, complexes of the type [Cp*M(L')Cl]Cl were obtained. However, when L1 and L2 ligands have been employed with excess [Cp*MCl(mu-Cl)]2, the formation of [Cp*M(L')Cl][Cp*MCl3] species has been observed. PGSE NMR measurements have been carried out for these complexes, in which the counterion is a cyclopentadienyl metal complex, in CD2Cl2 as a function of the concentration. The hydrodynamic radius (rH) and, consequently, the hydrodynamic volume (VH) of all the species have been determined from the measured translational self-diffusion coefficients (Dt), indicating the predominance of ion pairs in solution. NOE measurements and X-ray single-crystal studies suggest that the [Cp*MCl3]- approaches the cation, orienting the three Cl-legs of the "piano-stool" toward the CH2 moieties of the bis(pyrazolyl)methane ligands. The reaction of 1 equiv of [Cp*M(L')Cl]Cl or [Cp*M(L')Cl][Cp*MCl3] with 1 equiv of AgX (X = ClO4 or CF3SO3) in CH2Cl2 allows the generation of [Cp*M(L')Cl]X, whereas the reaction of 1 equiv of [Cp*M(L')Cl] with 2 equiv of AgX yields the dicationic complexes [Cp*M(L')(H2O)][X]2, where single water molecules are directly bonded to the metal atoms. The solid-state structures of a number of complexes were confirmed by X-ray crystallographic studies. The reaction of [Cp*Ir(L')(H2O)][X]2 with ammonium formate in water or acetone solution allows the generation of the hydride species [Cp*Ir(L')H][X]. 相似文献
955.
Banfi L Basso A Guanti G Kielland N Repetto C Riva R 《The Journal of organic chemistry》2007,72(6):2151-2160
A short, two-step approach to the synthesis of diazepane or diazocane systems, based on a Ugi multicomponent reaction followed by a subsequent intramolecular SN2 reaction was studied. 1-sulfonyl tetrahydrobenzo[e]-1,4-diazepin-1-ones 1 were obtained in very high yield through a Ugi multicomponent reaction followed by Mitsunobu cyclization. On the other hand, aliphatic 1-sulfonyl 1,4-diazepan-5-ones 2 could be obtained employing different cyclization conditions (sulfuryl diimidazole). A similar approach toward diazocane rings using hydroxamates as nucleophiles was less successful, affording only O-cyclized adducts or unexpected side products. A mechanistic explanation of the observed outcomes is proposed. 相似文献
956.
Lombardo M Mosconi E Pasi F Petrini M Trombini C 《The Journal of organic chemistry》2007,72(5):1834-1837
Zinc-promoted hydroxyallylation of alpha-amidoalkyl arylsulfones 4 using 3-bromo-propenyl methyl carbonate 5 proceeds smoothly in DMF at room temperature to afford high yields of differentially protected anti-1,2-amino alcohols 6. 相似文献
957.
Tushar S. Basu Baul Wandondor Rynjah Claudio Pettinari Robert Jirásko Anthony Linden 《Journal of organometallic chemistry》2007,692(17):3625-3635
Reactions of 5-[(E)-2-(aryl)-1-diazenyl]-2-hydroxybenzoic acids (LHH′, where the aryl group is an R-substituted phenyl ring such that for L1HH′: X = H; L2HH′: X=2′-OCH3; L3HH′: X = 3′-CH3; L4HH′: X = 4′-CH3; L5HH′:X = 4′-Cl) with nOct2SnO in 2:1 and 1:1 molar ratios have been investigated. Two types of complexes, nOct2Sn(LH)2 and {[nOct2Sn(LH)]2O}2, were isolated and they have been characterized by 1H, 13C, 119Sn NMR, ESI-MS, IR and 119mSn Mössbauer spectroscopic techniques in combination with elemental analyses. The crystal structures of nOct2Sn(L1H)2 (1), {[nOct2Sn(L2H)]2O}2 (3) and {[nOct2Sn(L3H)]2O}2(4) were determined. The mononuclear complex 1 was found to adopt a skew-trapezoidal bipyramidal arrangement around the tin atom while 3 and 4 are centrosymmetric tetranuclear bis(dicarboxylatotetrabutyldistannoxane) complexes containing a planar Sn4O2 core in which two μ3-oxo O-atoms connect an Sn2O2 ring to two exocyclic Sn-atoms. The solution structures were confirmed by 119Sn NMR spectroscopy by observing one tin resonance in compound 1 and two tin resonances in {[nOct2Sn(L5H)]2O}2 (5). {[nOct2Sn(L2H)]2O}2 (3) and {[nOct2Sn(L3H)]2O}2 (4) undergo very complex exchange processes in deuteriochloroform solution, which has been confirmed by variable temperature 1H NMR spectroscopy. The cleavage of the most labile bond in the molecule was studied by ESI mass spectrometry. 相似文献
958.
Pino A Alimonti A Botrè F Minoia C Bocca B Conti ME 《Rapid communications in mass spectrometry : RCM》2007,21(12):1900-1906
A simple and efficient digestion method for rapid sample preparation and quantification of 25 chemical elements in lichens by sector field inductively coupled plasma mass spectrometry is described. A microwave (MW)-assisted acid digestion was carried out at atmospheric pressure simultaneously handling up to 80 samples in screw-capped disposable polystyrene tubes. This digestion procedure was compared with the established MW digestion in closed vessels in order to examine its potential applicability in routine analysis for environmental monitoring. Three certified reference materials, i.e. BCR 482 (lichens), BCR 62 (olive leaves) and BCR 100 (beech leaves), as well as a small set of real samples were analyzed. Limits of quantification, accuracy and precision of the method were assessed. The majority of the elements were totally recovered from the lichens and from the other vegetable matrices. Low contamination risk, simplicity, time-saving, and applicability in routine analyses make this method very suitable for use in extensive screening campaigns. 相似文献
959.
Berríos C Cardenas-Jirón GI Marco JF Gutiérrez C Ureta-Zañartu MS 《The journal of physical chemistry. A》2007,111(14):2706-2714
A set of substituted (sulfonate, amino) nickel porphyrin derivatives such as phthalocyanine and phenylporphyrin was studied by spectroscopic (UV-vis, FTIR, XPS) and quantum-chemical methods. The Q and Soret bands were identified in the UV-vis spectra of aquo solutions of the tetrasulfo-substituted complexes and in DMF and ACN solutions of the amino-substituted phenylporphyrin and phthalocyanine Ni(II) complexes, respectively. In all the complexes the frontier molecular orbitals predict that the oxidation and reduction sites are localized on the ligand rather than in the metal atom. A natural bonding orbital (NBO) analysis of all the complexes showed that a two-center bond NBO between the pyrrolic nitrogens (Npyrr) and the nickel atom does not exist, the Npyrr...Ni interaction occurring instead by a delocalization from one lone pair of each Npyrr toward one lone pair of the nickel atom, as estimated by second-order perturbation theory. The calculated values of electronic transitions between the frontier molecular orbitals are in good agreeement with the UV-vis data. At the theoretical level, we found that while the ligand effect is more important in the Q-band (approximately 16 kcal/mol), the substituent effect is more significant in the Soret band (approximately 9 kcal/mol). A good agreement was also found between the experimental and calculated infrared spectra, which allowed the assignment of many experimental bands. The XPS results indicate that the Ni(II) present in the phenylporphyrin structure is not affected by a change of the substituent (sulfonate or amino). 相似文献
960.
Eugenie Geringer Dr. Marina Gerhard Prof. Dr. M. Koch Dr. Claudio K. Krug Prof. Dr. J. Michael Gottfried Prof. Dr. Stefanie Dehnen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(8):2734-2741
Herein, we present the synthesis of two pyrene-functionalized clusters, [(RpyrSn)4S6]⋅2 CH2Cl2 ( 4 ) and [(RpyrSn)4Sn2S10]⋅n CH2Cl2 (n=4, 5 a ; n=2, 5 b ; Rpyr=CMe2CH2C(Me)N-NC(H)C16H9), both of which form in reactions of the organotin sulfide cluster [(RNSn)4S6] ( C ; RN=CMe2CH2C(Me)N-NH2) with the well-known fluorescent dye 1-pyrenecarboxaldehyde ( B ). In contrast, reactions using an organotin sulfide cluster with another core structure, [(RNSn)3S4Cl] ( A ), leads to formation of small molecular fragments, [(RpyrCl2Sn)2S] ( 1 ), (pyren-1-ylmethylene)hydrazine ( 2 ), and 1,2-bis(pyren-1-ylmethylene)hydrazine ( 3 ). Besides synthesis and structures of the new compounds, we report the influence of the inorganic core on the optical properties of the dye, which was analyzed exemplarily for compound 5 a via absorption and fluorescence spectroscopy. This cluster was also used for exploring the potential of such non-volatile clusters for deposition on a metal surface under vacuum conditions. 相似文献