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21.
22.
R. F. Klevtsova L. A. Glinskaya T. E. Kokina S. V. Larionov 《Journal of Structural Chemistry》2003,44(2):256-267
Single crystals of [Ni(Phen)(iBu2PS2)2] (I) and [Ni(Phen)3](iBu2PS2)2 (III) compounds were grown, and their structures were determined by Xray diffraction analysis (CAD4 diffractometer, MoK
radiation, 3336 F
hkl
, R = 0.0373 for I and 2575 F
hkl
for III). The crystals of complex I have a triclinic unit cell with the following parameters: a = 11.097(1) , b = 14.903(2) , c = 22.650(3); = 75.18(1)°, = 80.50(1)°, = 75.07(1)°, V = 3479.2(7)3, Z = 4, calc = 1.255 g/cm3, and space group
1; the crystals of III have a monoclinic unit cell with the following parameters: a = 19.010(3), b = 15.481(1) , c = 17.940(3); = 97.58(1)°, V = 5233.5(12)3, Z = 4, calc = 1.292 g/cm3, and space group C2/c. The structure of complex I is built from mononuclear molecules, and the structure of III, from [Ni(Phen)3]2+ complex cations and i Bu2PS2
- outersphere anions. The NiN2S4 coordination polyhedra in the structure of I and NiN6 in the structure of III are distorted octahedra. Based on structural data, the interaction between the coordinated Phen molecules of complexes I, [Ni(Phen)2(iBu2PS2)](iBu2PS2) (II), and III is considered, as well as the packing modes of these complexes. 相似文献
23.
This paper concerns the application of excess adsorption isotherms, measured for solvent mixture/adsorbent systems, to the characterization of TLC data. For this purpose the excess adsorption isotherms for three liquid mixtures: cyclohexane/ benzene, benzene/acetone, and carbon tetrachloride/ethyl acetate on silica gel at 20°C have been measured. These mixtures have been used as binary mobile phases in TLC measurements. It has been shown for a given solute in binary mobile phase that the quantity RM is a simple function of the excess adsorption. Parameters of this function have been used to characterize chromatographic systems with binary mobile phases. 相似文献
24.
Summary The paper discusses the effect of the length and structure of the hydrocarbon chain connecting the nitrile group to the silica gel surface on the chromatographic properties of cyanoalkyl phases.When using non-polar and polar mobile phases, the selectivity of the cyanodecyl phases toward PAHs is higher than of the cyanopropyl phase and of hydroxylated silica gel.Polar additives to the mobile phase drastically decrease the retention on silica gel and on the cyanopropyl phase while affect the properties of cyanodecyl phases only to a considerably less degree. Newly synthesized phases with different structures of the hydrocarbon chain are compared with the commerical cyano-and ODS-phases. The retention mechanism on the cyanoalkyl phases is discussed. 相似文献
25.
Shyan-Ming Yuan 《BIT Numerical Mathematics》1991,31(1):53-68
To maintain consistency on a distributed database system, a commit protocol is often employed to ensure that either all the sub-transactions of a transaction commit or all abort. Special care needs to be taken to ensure the correct functioning of a commit protocol in the face of node failures during the execution of the protocol. A protocol is said to be fault-tolerant if it properly commits or aborts, even if nodes fail.In this paper, we present a fault tolerant decentralized commit protocol which is message optimal in the absence of failures. Furthermore, the protocol (FTDCP) ensures that all sites can achieve a consistent final decision by at most 4 extra messages in the single site failure situation. 相似文献
26.
Mutsuo Igarashi 《Molecular Crystals and Liquid Crystals》2013,570(2):437-440
Abstract Spin-spin relaxation of 23Na-NMR is observed by the spin echo method at room temperature for Y-type zeolite loaded with Na metal without hydration. For saturated and no levels of loading, the echo decay is well fitted by single exponential function. T 2 decreases to be 0.25 times smaller by loading. This decrease of T 2 is explained semiquantitatively with assuming nuclear dipole-dipole interaction between neighboring Na. 相似文献
27.
Rolf Appel Nikolaos Siabalis 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3-4):273-274
Abstract Reactions of carbonyl cyclopentadienyl hydrides from molybdenum and tungsten with 1,4-diphosphabuta-1,3-diene yield metalla-diphospha-pentadiene with a metal-phosphorus-double bond. Metalla-diphosphapentadiene mit einer Metall-Phosphor-Doppelbindung werden durch Umsetzung von Carbonylcyclopentadienylhydriden des Molybdäns und Wolframs mit einem 1,4-Diphospha-buta-1,3-dien erhalten. 相似文献
28.
Marcello Bernardara Emanuele Macrì Sukhendu Mehrotra Paolo Stellari 《Advances in Mathematics》2012,229(2):770-803
We prove a categorical version of the Torelli theorem for cubic threefolds. More precisely, we show that the non-trivial part of a semi-orthogonal decomposition of the derived category of a cubic threefold characterizes its isomorphism class. 相似文献
29.
Alexandr Usnich 《Advances in Mathematics》2011,228(4):1863
The Cremona group acts on the field of two independent commutative variables over complex numbers. We provide a noncommutative algebra that is an analog of a noncommutative field of two independent variables and prove that the Cremona group embeds in a group of outer automorphisms of this algebra. We give two proofs of it, the first proof is technical, the second one is conceptual and proceeds through a construction of a birational invariant of an algebraic variety from its bounded derived category of coherent sheaves. 相似文献
30.
Formation, crystal structure, polymorphism, and transition between polymorphs are reported for M(thd)3, (M = Al, Cr, Mn, Fe, Co, Ga, and In) [(thd)– = anion of H(thd) = C11H20O2 = 2, 2, 6, 6‐tetramethylheptane‐3, 5‐dione]. Fresh crystal‐structure data are provided for monoclinic polymorphs of Al(thd)3, Ga(thd)3, and In(thd)3. Apart from adjustment of the M–Ok bond length, the structural characteristics of M(thd)3 complexes remain essentially unaffected by change of M. Analysis of the M–Ok, Ok–Ck, and Ck–Ck distances support the notion that the M–Ok–Ck–Ck–Ck–Ok– ring forms a heterocyclic unit with σ and π contributions to the bonds. Tentative assessments according to the bond‐valence or bond‐order scheme suggest that the strengths of the σ bonds are approximately equal for the M–Ok, Ok–Ck, and Ck–Ck bonds, whereas the π component of the M–Ok bonds is small compared with those for the Ok–Ck, and Ck–Ck bonds. The contours of a pattern for the occurrence of M(thd)3 polymorphs suggest that polymorphs with structures of orthorhombic or higher symmetry are favored on crystallization from the vapor phase (viz. sublimation). Monoclinic polymorphs prefer crystallization from solution at temperatures closer to ambient. Each of the M(thd)3 complexes subject to this study exhibits three or more polymorphs (further variants are likely to emerge consequent on systematic exploration of the crystallization conditions). High‐temperature powder X‐ray diffraction shows that the monoclinic polymorphs convert irreversibly to the corresponding rotational disordered orthorhombic variant above some 100–150 °C (depending on M). The orthorhombic variant is in turn transformed into polymorphs of tetragonal and cubic symmetry before entering the molten state. These findings are discussed in light of the current conceptions of rotational disorder in molecular crystals. 相似文献