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11.
H. D. Rudolph 《Structural chemistry》1991,2(6):581-588
This work investigates and enumerates the types of molecular structure that can, in principle, be obtained when moments of inertia, planar moments, or rotational constants or different forms of their isotopic differences are least-squares fitted to the respective experimental ground state values. Ther
0-structure, ther
0-derived pseudo-Kraitchman structuresr
I andr
B, and an inequality relation between them are discussed. A least-squares treatment that tries to determine not only the set of structural parameters but also constant, i.e., isotope-independent, rovibrational contributions to the moments of inertia or rotational constants is possible and merits preference. It is shown that the resulting structures are, however, identical with the formerr
orr
B-structures, respectively. 相似文献
12.
Rudolph Willem Ann Delmotte Inge De Borger Monique Biesemans Marcel Gielen Franois Kayser Edward R. T. Tiekink 《Journal of organometallic chemistry》1994,480(1-2):255-259
The synthesis of (Z)-2-methyl-3-triphenylstannyl-3-pentene-2-ol and its characterization by an X-ray diffraction study and multinuclear NMR are reported. The tin atom exhibits a distorted tetrahedral SnC4 geometry with the four Sn---C bond distances experimentally equivalent. The slight distortion from the ideal tetrahedral geometry is because of the presence of a weak intramolecular HO → Sn interaction of 3.012(3) Å which produces a loose four-membered ring. The title compound was characterized in solution by 1H, 13C and 119Sn NMR, and the persistence of the weak intramolecular HO → Sn coordination in solution was revealed by 13C and 119Sn secondary isotope multiplet of partially labelled entities (SIMPLE-NMR) experiments. 相似文献
13.
New Redox Series Based on Transition Metal Complexes of Heterocyclic Arenesulfonylhydrazones Heterocyclic bidentate arenesulfonylhydrazones (2-acetylpyridine-p-toluenesulfonylhydrazone ? APSH? H, 2-acetylquinoline-p-toluenesulfonylhydrazone ? ACSH? H) with transition metal ions afford tetrahedral 1,2-complexes MII(APSH)2 and MII(ACSH)2. In most cases the E-isomers of APSH? and ACSH? are coordinated, five-membered chelate rings are formed with the pyridine and hydrazone nitrogen atoms as donor atoms. In the complexes Zn(APSH)2 and Cu(APSH)2 probably the Z-isomer of APSH? is present with the pyridine and the sulfonylamide nitrogen atoms as a donor set, yielding a six-membered chelate ring. These proposals are based on the magnetic moments, the ligand field spectra, and the binding energies (ESCA). Normally the complexes MII(APSH)2 and MII(ACSH)2 are reduced in two reversible steps. For Fe(APSH)2 and Fe(ACSH)2 a third anodic wave, but for Cu(APSH)2 only one wave is observed. Relations between redox properties and structure of the new complexes are discussed, and the redox series are compared with that of the M(dipy)3n+-type complexes. 相似文献
14.
Summary We prove that a
d
-action by automorphisms of a compact, abelian group is Bernoulli if and only if it has completely positive entropy. The key ingredients of the proof are the extension of certain notions of asymptotic block independence from -actions to
d
-action and their equivalence with Bernoullicity, and a surprisingly close link between one of these asymptotic block independence properties for
d
-actions by automorphisms of compact, abelian groups and the product formula for valuations on global fields.Oblatum 20-X-1994 相似文献
15.
We state a new ergodic theorem, combining the Wiener-Wintner theorem and Bourgain’s theorem concerning the convergence of ergodic averages along return-times sequences. We consider ergodic averages of the form $$\frac{1}{N}\sum\limits_{n = 0}^{N - 1} {e^{in\theta } \cdot f'(S^n y) \cdot f(T^n x)} $$ and we show that the behaviour of these averages characterizes an algebraC of functions, which contains the Kronecker algebra and has interesting properties, linked with multiple recurrence ergodic theorems. 相似文献
16.
Fangzin Fu Hongyu Li Dongsheng Zhu Qunxin Fang Huade Pan Edward R. T. Tiekink Franois Kayser Monique Biesemans Ingrid Verbruggen Rudolph Willem Marcel Gielen 《Journal of organometallic chemistry》1995,490(1-2):163-171
The synthesis and characterization by 1H, 13C, 119Sn NMR and 119Sn Mössbauer spectroscopy of (Z)-1-[2-(triphenylstannyl)vinyl]-1-cycloheptanol,
(1), and (Z)-1-[2-tri-p-tolylstannyl)vinyl-1-cycloheptanol,
(2), are described, together with their halodemetallation by I2, Br2 and ICIl to yield derivatives of the types
(Ar = phenyl or p-tolyl, N = 1, 2; X = I, Br, Cl, respectively). The solid-state structures of four compounds have been determined by X-ray diffraction analysis. In the crystals of
(1) and
(2) the Sn atom has a tetrahedral geometry distorted towards trigonal bipyramid as a consequence of a close intramolecular contact with the hydroxyl O(1) atom of 2.742(3) Å and 2.768(3) Å, respectively. A trigonal bipyramidal geometry is found in
(12) and
(4), in which significant Sn---O(1) interactions are noted [2.437(8) Å and 2.407(8) Å, respectively]. 相似文献
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17.
18.
Biesemans M Martins JC Jurkschat K Pieper N Seemeyer S Willem R 《Magnetic resonance in chemistry : MRC》2004,42(9):776-780
It is demonstrated that long-range nJ(1H,117Sn) coupling constants down to 0.3 Hz, can be accurately quantified from non-linear fitting of the sine modulation of the associated 1H-117Sn correlation cross-peak intensities sampled as a function of the heteronuclear antiphase coherence preparation time in the 1H-117Sn J-HMQC pulse sequence. The contribution of additional, undesired modulations is illustrated and assessed using the product operator formalism, and is traced back to contributions that arise from miss-setting of the wandering 180 degrees pulse angle in the constant time period. The power of the method and its use in the characterization of weak intramolecular donor-acceptor interactions are illustrated by the determination of long-range nJ(1H,117Sn) coupling constants of bis[3-(dimethylamino)propyl]tin derivatives, [Me2N(CH2)3]2SnR2 (', R = Me; 3, R = Ph; 4, R = t-Bu). By comparing these with the values found for the corresponding bis(4-methylpentyl)tin derivatives, [Me2CH(CH2)3]2SnR2 (2', R = Me; 3', R = Ph), which lack such interactions, the use of long-range coupling constants to detect intramolecular donor-acceptor interactions is evaluated. It is concluded that nJ(1H,117Sn) couplings up to six bonds through an organic carbon chain can be quantified, whether donor-acceptor interactions are present or not. Furthermore, evidence is presented that, when two scalar coupling pathways co-exist, the pathway involving an intramolecular donor-acceptor interaction can have opposite sign, thus decreasing the overall coupling constant to a value smaller than that actually measured in the absence of a donor-acceptor interaction, where only one coupling pathway is active. There is nevertheless clear numerical value discrimination in the series of compounds investigated between long-range couplings in derivatives without weak intramolecular donor-acceptor interactions and those where such interactions can exist. 相似文献
19.
Bobby L. Wilson Rudolph R. Schwarzer Callista O. Chukwuenye 《Microchemical Journal》1982,27(4):558-563
This paper reports the development of a field electrode method for the determination of total sulfide in water. The method involves the use of preweighed sodium sulfide crystals in the standardization process. Sodium sulfide crystals were weighed and sealed in air-tight plastic volumetric flasks. Standards were prepared in the field by adding a sulfide antioxidant buffer to the flasks containing the sulfide crystals and diluting it to mark with deionized deaerated water. Standards of lower concentration were prepared by serial dilutions of first standards.The results of the reproducibility determination revealed that sulfide concentrations as low as 6 ppb could be measured with a reproducibility of better than ±10%.Water samples were collected from a series of lakes in Fort Bend County, Texas (near Houston) and analyzed for sulfide content. The sulfide ion concentrations of these samples were determined directly in the field by use of an Orion Model 407A/F specific meter equipped with a silver/sulfide ion selective electrode in conjunction with a double junction reference electrode. 相似文献
20.
Rodrigues JA Abramovitch RA de Sousa JD Leiva GC 《The Journal of organic chemistry》2004,69(9):2920-2928
In preliminary communications, we reported the diastereoselective synthesis of cularine and sarcocapnine via the intramolecular ring closure of nitrenium and oxenium ions, a new highly diastereoselective reductive methylation with (+)-8-phenylmenthyl chloroacetate followed by reduction with sodium borohydride, and a facile entry to the isoquinoline precursors by aza-Wittig electrocyclic ring closure. We now report the full details of the syntheses of (+)-O-demethylcularine, (+)-cularine, (+)-sarcocapnidine, (+)-sarcocapnine, and (+)-crassifoline and describe different methods of synthesis of their precursors. 相似文献