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21.
A convergent formal total synthesis of OF 4949 III is described. Arene-ruthenium chemistry was used in the construction of the diaryl ether linkage in high yield, and cycloamidation under high dilution conditions (0.005 M) was achieved using DPPA as coupling reagent. SmI(2) was used to reductively remove the 2-iodoethyl ester protecting group in the presence of DMPU or HMPA. 相似文献
22.
A new method is presented for spectrophotometric micro-determinations of cadmium by means of a triazine dye, called “Cadion”The method is a highly sensitive one, permitting the determination of 0.05 p.p.m. cadmium in the final solution, with satisfactory accuracy and reproducibility.The interference of the main foreign anions and cations is studied, and a way of eliminating the interfering ions is suggestedSome examples are given for the application of the proposed method 相似文献
23.
Anthony B. Cornwell Philip G. Harrison John A. Richards 《Journal of organometallic chemistry》1977,140(3):273-287
The reaction of organotin chlorides with the lithium salt of 7,7,8,8-tetracyanoquinodimethane (TCNQ) or hexaalkylditins with TCNQ yield stable organotin-substituted free radicals of the types R3SnTCNQ. (R = Me, n-Pr, n-Bu) and Me2Sn(TCNQ.)2. The reaction of hexaphenylditin with TCNQ yields a (σ → π) charge transfer complex of stoichiometry (Ph3SnSnPh3)·TCNQ, whilst [Me2SnCl(terpyridyl)+](TCNQ-·) was isolated from the reaction of [Me2SnCl(terpyridlyl)+][Me2SnCl3-] and LiTCNQ. The oxidation of hexaalkylditins by tetracyanoethylene (TCNE) yields stable free radicals of the type R3SnTCNE·, but treatment with 2,3,5,6-tetrachlorobenzoquinone yields either R3SnOC6Cl4O·-p (R = Me) or R3SnOC6Cl4OSnR3-p (R = n-Bu, Ph). Tin-119 Mössbauer spectroscopy shows that the derivatives R3SnTCNQ· and R3TCNE· have trigonally-bipyramidally coordinated tin with planar [SnC3] skeletons and bridging [TCNQ·] and [TCNE·] groups forming infinite one-dimensional chain structures. Me3SnOC6Cl4O·-p was inferred to possess a similar structure but with oxy bridges forming chains with a Sn---O---Sn---O backbone. Me2Sn(TCNQ·)2 has a structure intermediate between tetrahedral and octahedral with a non-linear MeSnMe unit and anisobidentate chelation by two TCNQ groups. The TCNQ derivatives were of two types: (i) “green” or “brown”, indicative of delocalisation of the Ione electron over the cyanoquinone ligand, and (ii) a “blue” form in which spin-pairing of the Ione electron between adjacent organic groups takes place. Me3SnTCNQ· may exist in both forms depending upon the mode of preparation. 相似文献
24.
The [Ru(bipy)(2)(1)](PF(6))(2) (bipy refers to 2,2'-bipyridine) complex, comprising a ruthenium(II) tris(2,2'-bipyridine) luminophore covalently linked to a di[(o-triethyleneglycoxy)phenyl]amine crown ether 1, has been synthesized and fully characterized. The photophysical properties of this metal complex have been examined in solution at ambient temperature. Luminescence from the metal complex is enhanced significantly in the presence of various adventitious cations, including protons. In particular, Li(+) cations bind to the crown ether, as evidenced by (1)H NMR and luminescence spectroscopy. Cation binding serves to decrease the rate of reductive quenching of the triplet state of the metal complex, thereby increasing the extent of luminescence. The solution-phase conformation of [Ru(bipy)(2)(1)](PF(6))(2), with and without encapsulated Li(+), has been examined by 2-D NMR and by molecular dynamics simulations. 相似文献
25.
Cowley AR Downs AJ Himmel HJ Marchant S Parsons S Yeoman JA 《Dalton transactions (Cambridge, England : 2003)》2005,(9):1591-1597
The novel adduct 1,1,3,3-tetramethylguanidine-gallane, (Me2N)2CN(H).GaH3, has been prepared by the reaction of [(Me2N)2CNH2]+Cl- with LiGaH4 in Et2O solution. Its spectroscopic properties indicate a monomeric species with an unusually strong coordinate link between the imido function and GaH3, an inference confirmed by the crystal structure at 150 K which also reveals significant secondary interactions through non-classical N-H...H-Ga bridges. Despite the intrinsic strength of the Ga-N bond, however, vaporisation at ca. 310 K occurs with partial dissociation, and decomposition via more than one pathway proceeds at temperatures >330-350 K to give a variety of products, including the free base, Me2NH, H2, and a novel gallium-nitrogen compound composed of a Ga4N4 cubane-like core bridged on three edges by -N{C(NMe2)2}GaH2- units. 相似文献
26.
A new example of stereospecific cationic cyclization of iron tricarbonyl diene complexes with pendant alkenes and arenes is provided. Protonation of a double bond vicinal to the iron tricarbonyl diene moiety is employed to trigger the cyclization, rather than the previously reported Lewis/protic acid dehydroxylation of diastereomeric alcohols, eliminating one step of separation and avoiding some reactivity problems previously encountered for one of the alcohol diastereoisomers. [reaction: see text] 相似文献
27.
H.David Empsall Bernard L. Shaw Anthony J. Stringer 《Journal of organometallic chemistry》1975,94(1):131-138
Several new platinum(II) acetylide complexes, trans-{Pt[CCCR1R2(OR3)]2-L2} (R1, R2 H, Me, Et; CR1R2 cyclohexylidene; R3 H, Me or Ph), trans-[Pt(CCCH2CH2OH)2L2], trans-[Pt(p-tolylacetylide)2L2] and trans-[PtX(p-tolylacetylide)L2] (L PMe2Ph or in one case, AsMe2Ph) have been prepared. Platinum(II) acetylide complexes with tertiary hydroxyl groups are easily dehydrated by acetic anhydride/pyridine to give platinum-enyne complexes. Analogous compounds with primary hydroxyl groups do not dehydrate but give acetates. 1H and 13C NMR data are given and the shift reagent Eu(fod)3 was used to analyse the 1H NMR spectrum of trans-[Pt(CCCH2CH2OH)2(PMe2Ph)2]. 相似文献
28.
A series of new esters of lutein ( 1a ) have been prepared with the aim of confirming the structure of lutein via an X‐ray crystal‐structure analysis. Although well crystallized, only one of the derivatives, the (?)‐(1R)‐menthyl carbonate ( 1i ) proved to be useful for a complete structure analysis. The same derivative of zeaxanthin ( 2a ) also allowed its crystal structure to be determined. Both analyses represent the first successful X‐ray crystal structure analyses of the most important xanthophylls. At the same time, they confirm both the constitution and absolute configuration of 1a and 2a that had been deduced earlier by classical methods. 相似文献
29.
Anthony Poë 《Journal of organometallic chemistry》1976,120(1):C20-C21
The palladium(I) and platinum(I) complexes [(CH3NC)6M2]2+ undergo substitution reactions with isocyanides, phosphines and halide or pseudohalide ions. With triphenylphosphine, axial substitution is preferred. The product [(CH3NC)5(Ph3P)Pd2]2+ is fluxional. 相似文献
30.
McCaffery AJ Osborne MA Marsh RJ Lawrance WD Waclawik ER 《The Journal of chemical physics》2004,121(1):169-180
Vibrational relaxation of the 6(1) level of S(1)((1)B(2u)) benzene is analyzed using the angular momentum model of inelastic processes. Momentum-(rotational) angular momentum diagrams illustrate energetic and angular momentum constraints on the disposal of released energy and the effect of collision partner on resultant benzene rotational excitation. A kinematic "equivalent rotor" model is introduced that allows quantitative prediction of rotational distributions from inelastic collisions in polyatomic molecules. The method was tested by predicting K-state distributions in glyoxal-Ne as well as J-state distributions in rotationally inelastic acetylene-He collisions before being used to predict J and K distributions from vibrational relaxation of 6(1) benzene by H(2), D(2), and CH(4). Diagrammatic methods and calculations illustrate changes resulting from simultaneous collision partner excitation, a particularly effective mechanism in p-H(2) where some 70% of the available 6(1)-->0(0) energy may be disposed into 0-->2 rotation. These results support the explanation for branching ratios in 6(1)-->0(0) relaxation given by Waclawik and Lawrance and the absence of this pathway for monatomic partners. Collision-induced vibrational relaxation in molecules represents competition between the magnitude of the energy gap of a potential transition and the ability of the colliding species to generate the angular momentum (rotational and orbital) needed for the transition to proceed. Transition probability falls rapidly as DeltaJ increases and for a given molecule-collision partner pair will provide a limit to the gap that may be bridged. Energy constraints increase as collision partner mass increases, an effect that is amplified when J(i)>0. Large energy gaps are most effectively bridged using light collision partners. For efficient vibrational relaxation in polyatomics an additional requirement is that the molecular motion of the mode must be capable of generating molecular rotation on contact with the collision partner in order to meet the angular momentum requirements. We postulate that this may account for some of the striking propensities that characterize polyatomic energy transfer. 相似文献