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141.
142.
143.
ADSORPTION OF 2,4-DICHLOROBENZOXYACETIC ACID ONTO HYPERCROSSLINKED RESIN MODIFIED BY PHENOLIC HYDROXYL GROUP (AM-1) 总被引:2,自引:0,他引:2
INTRODUCTIONAdsorption has been considered to be the best available technology for removing organics from water in the USSafe Drinking Water Act[1]. Due to many drawbacks of activated carbon[2-7], the most widely used adsorbent,hypercrosslinked polymeric adsorbents developed by Tsyurupa and Davankov[8] have been increasingly viewedas an alternative to activated carbon for selective removal of specific organic substances from contaminatedwater[9-12], and series of researches have been do… 相似文献
144.
Prochiral alkenes, aldehydes, and ketones constitute the most frequently used starting materials for enantioselective organic syntheses. Protocols often involve chiral binding agents or Lewis acids that can give two diastereomeric adducts, the ratios of which are measures of chiral recognition. With π adducts, the diastereomers differ in the enantioface of the C?C or O?C group bound to the Lewis acid. This review provides the first comprehensive analysis of such equilibria and related binding phenomena with chiral transition metal Lewis acids. An extensive body of data from the authors' laboratory for complexes of the pyramidal rhenium fragment [(η5?C5H5)Re(No)(PPh3)]+ ( I ) affords particular insight. Literature data for other complexes are also summarized. A general model for chiral recognition based upon the relative steric properties of four quadrants is presented. This enables binding selectivities to be individually and rationally optimized for different classes of ligands. Electronic effects are also identified and correlated with specific structural properties. Relationships between binding equilibria, reactivity, and product configurations are discussed. 相似文献
145.
F. F. C. Bazito S. I. Córdoba de Torresi R. M. Torresi 《Journal of Solid State Electrochemistry》2007,11(11):1471-1479
Poly(phenylene sulfide phenyleneamine), PPSA, is a copolymer of poly(aniline) and poly(phenylene sulfide), soluble in conventional
organic solvents as tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and cyclohexanone. In this research, its electrochemical
behavior has been studied in acetonitrile in the presence of different electrolytes, where the loss of electroactivity was
observed after few cycles. In this paper, the charge compensation dynamics of PPSA is analyzed through electrochemical quartz
crystal microbalance experiments and electroacoustic impedance measurements. Raman spectroscopy data have shown that once
the oxidation of the sulfur atom occurs, a loss of electroactivity is observed, being not possible to recover the pristine
state of the polymer. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data obtained for the fully oxidized polymer
are consistent with the formation of a networked polymer due to the electrophilic attack of the positive sulfur atom on the
activated aromatic rings. Electrochemical quartz crystal microbalance results clearly show that the degree of irreversibility
fully depends on the chemical nature of the anions with a negligible participation of the cations of the electrolytic solution.
This work is in memoriam of Prof. Dr. Francisco C. Nart, dearest friend and colleague, whose scientific skills and enthusiasm
will always be remembered. 相似文献
146.
Interatomic distances in the transition state were estimated for the reactions of radical abstraction: H· + H2, H· + HCl, H· + CH4, N·H2 + NH3, HO· + H2O, HO2
· + HOOH, and C·H3 + SiH4. The calculation was performed by the quantum-chemical density functional method or coupled clusters method (QCH), as well as by the methods of intersecting parabolas (IPM) and Morse curves (IMM), using experimental data (activation energies and reaction enthalpies). The results of the latter two methods are close to the quantum-chemical calculation and differ only by the increment a: r(IPM or IMM) = a + r(QCH), where a = –4.5·10–12 m for IPM and a = +1.9·10–12 m for IMM. 相似文献
147.
Summary Further to Gilpin's observations in liquid chromatography of the irreversible transformation of alkyl grafts, following the replacement of an organic mobile phase by an aqueous one, we describe some gas chromatographic experiments which lead to similar (log Vs, I/T) plots, as a consequence of the same solvent release process.We use paraffin films on siliceous supports or hydroxylated liquid substrates or C22-alkyl bonded silica. These experiments demonstrate that this irreversible transition and the melting-like reversible transition are completely different phenomena. They confirm the existence of at least three kinds of monomeric alkyl films. 相似文献
148.
149.
合成了9种具L-氨基酸衍生物结构的介晶化合物(I-Ⅲ,Ⅳab,Ⅴa,b,Ⅵa,b)、4种氨基酸衍生物(A1-4)和6种介晶化合物(M1-6).新化合物(Ⅰ-Ⅲ,Ⅳa,b,Ⅴa,b,Ⅵa,b,A4,M3-6)的化学结构通过IR、1HNMR和元素分析证实;并用偏光显微观察和DSC分析研究了其相变行为,结果表明有8种化合物(M3-6,Ⅵa,b,Ⅴb,Ⅵb)呈现液晶相变。测定了它们的比旋光度。通过X射线衍射研究了化合物Ⅵh120~130℃和Ⅵb170~180℃的近晶结构,Ⅵb显,Ⅵb呈。测定了化合物Ⅳb的电滞回线,证明其具铁电性。 相似文献
150.
We report a comprehensive theoretical study on the decarbonylation of acetaldehyde by Fe+ and Cr+. Various intermediates, transition states, and products involved in the decarbonylation reactions are fully optimized at the B3LYP/6-311+G(2df,2pd) level of theory. The potential energy surfaces (PESs) corresponding to [M,O,C2,H4]+(M=Cr and Fe) are examined in detail using B3LYP and CCSD(T) methods, respectively. The validity of these theoretical methods is calibrated with respect to the available thermochemical data. Calculations suggest that the Cr+ mediated decarbonylation of acetaldehyde takes place in four steps on the sextet surface: encounter complexation, C-C activation, aldehyde H-shift, and nonreactive dissociation, in good accordance with the Co+ mediated decarbonylation of acetaldehyde [Zhao, Zhang, Guo, Wu, Lu, Chem. Phys. Lett. 2005, 414, 28], while for the Fe+/acetaldehyde system decarbonylation can occur on both the quartet and the sextet PESs. The quartet pathway, which experiences spin-orbit coupling between the two surfaces, is energetically more favorable; whereas along the sextet decarbonylation coordinate several high-energy barriers are revealed. The theoretical results are compared with the experimental product kinetic energy and angular distributions of decarbonylation of acetaldehyde by Fe+ and Cr+ measured using a crossed-beam technique [Sonnenfroh, Farrar, J. Am. Chem. Soc. 1986, 108, 3521]. 相似文献