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31.
By means of the quasi-isothermal-quasi-isobaric thermogravimetry (Q-TG) technique ideal experimental conditions can be realized. This provides a possibility to compare the measured data with data from other phase equilibrium (solubility, tension) examinations.On the example of the Ca(NO3)2-H2O system it is demonstrated that the phase diagrams can be used to interpret thermoanalytical (especially Q-TG) curves, or conversely, the results of thermoanalytical (Q-TG, DTA) examinations can serve for the control of equilibrium data of phase diagrams or to supply missing data.
The authors are indebted to Prof. E. Pungor for valuable discussions, and thank Mrs. M. Kiss and Miss I. Fábián for their technical assistance. 相似文献
Zusammenfassung Mit Hilfe des quasi-isothermischen-quasi-isobaren thermogravimetrischen (Q-TG) Verfahrens können ideale Versuchsbedingungen realisiert werden. Das ermöglicht es, die gemessenen Daten mit von anderen Phasengleichgewicht-Untersuchungen (Lösbarkeit, Tension) stammenden Daten zu vergleichen.Durch das Beispiel des Ca(NO3)2-H2O-Systems wurde es gezeigt, dass die Phasendiagramme zur Erklärung von thermoanalytischen (insbesondere Q-TG) Kurven können angewandt werden, oder umgekehrt, die Ergebnisse der thermoanalytischen (Q-TG, DTA) Untersuchungen als Kontrolle der Gleichgewichtsdaten der Phasendiagramme dienen können, oder die fehlenden Daten liefern können.
- (Q-) . ( , ). Ca(NO3)2-H2O , ( Q-) , .
The authors are indebted to Prof. E. Pungor for valuable discussions, and thank Mrs. M. Kiss and Miss I. Fábián for their technical assistance. 相似文献
32.
Pradeep Mathur Bala Manimaran Md. Munkir Hossain Arnold L. Rheingold Louise M. Liable-Sands Glenn P.A. Yap 《Journal of organometallic chemistry》1997,540(1-2):165-168
The tris-methylene bridged compound (NO)4Fe2Se(μ-CH2)3 has been isolated. It has been characterised by IR and 1H, 13C, and 77Se NMR spectroscopy. Its structure has been determined by single-crystal X-ray diffraction methods. The structure consists of a heavy atom triangle consisting of one Se and two Fe atoms. The Fe-Fe and the two Fe-Se edges are bridged by methylene groups. 相似文献
33.
The influence of localized excited (LE) states on the spectroscopy of charge transfer (CT) complexes has been examined for a series of complexes formed between methyl-substituted benzene donors and 1,2,4,5-tetracyanobenzene as acceptor in 1,2-dichloroethane and octanenitrile solvents. A molecular orbital model was used to describe the appearance of multiple CT absorption bands that occur in the spectra of these complexes. The influence of LE states in these CT absorptions was explored using time-resolved linear dichroism spectroscopy where the direction of the CT transition moment vector (TMV) was used to probe the magnitude of intensity borrowing. The TMV directions for each of the observed CT transitions within the absorption spectra were determined for several complexes. In some cases, the observed CT transitions were interpreted as being pure CT transitions; in others the observed transitions are influenced significantly by a LE transition. The correlation between the TMV directions and the transition energy suggests that the magnitude of intensity borrowing is influenced not only by the energy difference between the CT and LE transitions but also by the specific character of the transitions under consideration. 相似文献
34.
Bruce M. Howard William Fenical Edward V. Arnold Jon Clardy 《Tetrahedron letters》1979,20(31):2841-2844
The structure of a unique bromine-containing ketal, obtusin (), has been determined by spectral and X-ray crystallographic techniques. Obtusin is a natural component of the Mediteranean red alga . 相似文献
35.
Abdol R. Hajipour Majid Mostafavi Arnold E. Ruoho 《Monatshefte für Chemie / Chemical Monthly》2007,138(6):569-572
Summary. A straightforward and effective procedure for the deprotection of thioacetals to the corresponding carbonyl compounds using
potassium persulfate and the ionic liquid [bmim]Br under solvent-free conditions is reported. A variety of aliphatic and aromatic 1,3-dithiolanes or 1,3-dithanes was deprotected
to the corresponding carbonyl derivatives by this procedure. 相似文献
36.
van Wijk AA Spaans A Uzunbajakava N Otto C de Groot HJ Lugtenburg J Buda F 《Journal of the American Chemical Society》2005,127(5):1438-1445
To resolve the molecular basis of the coloration mechanism of alpha-crustacyanin, we used (13)C-labeled astaxanthins as chromophores for solid-state (13)C NMR and resonance Raman spectroscopy of [6,6',7,7']-(13)C(4) alpha-crustacyanin and [8,8',9,9',10,10',11,11',20,20']-(13)C(10) alpha-crustacyanin. We complement the experimental data with time-dependent density functional theory calculations on several models based on the structural information available for beta-crustacyanin. The data rule out major changes and strong polarization effects in the ground-state electron density of astaxanthin upon binding to the protein. Conformational changes in the chromophore and hydrogen-bond interactions between the astaxanthin and the protein can account only for about one-third of the total bathochromic shift in alpha-crustacyanin. The exciton coupling due to the proximity of two astaxanthin chromophores is found to be large, suggesting that aggregation effects in the protein represent the primary source of the color change. 相似文献
37.
Negative ion photoelectron spectroscopy of solvated electron cluster anions, (H2O)
n
−
and (NH3)
n
−
G. H. Lee S. T. Arnold J. G. Eaton H. W. Sarkas K. H. Bowen C. Ludewigt H. Haberland 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):9-12
The photodetachment spectra of (H2O) n =2?69/? and (NH3) n =41?1100/? have been recorded, and vertical detachment energies (VDEs) were obtained from the spectra. For both systems, the cluster anion VDEs increase smoothly with increasing sizes and most species plot linearly withn ?1/3, extrapolating to a VDE (n=∞) value which is very close to the photoelectric threshold energy for the corresponding condensed phase solvated electron system. The linear extrapolation of this data to the analogous condensed phase property suggests that these cluster anions are gas phase counterparts to solvated electrons, i.e. they are embryonic forms of hydrated and ammoniated electrons which mature with increasing cluster size toward condensed phase solvated electrons. 相似文献
38.
Ashok G. Bajaj Sukh Dev Edward Arnold Bruce Tagle Jon Clardy 《Tetrahedron letters》1981,22(46):4623-4626
The steroechemistry of guggulsterol-1, a component of the exudate of , is shown to be 20(R), 22(R)(). 相似文献
39.
Crich D Mataka J Zakharov LN Rheingold AL Wink DJ 《Journal of the American Chemical Society》2002,124(21):6028-6036
A series of four S-allyl D-thiopyranosides, alpha- and beta-manno and xylo, were oxidized with MCPBA at low temperature to give seven of the eight possible sulfoxides, whose configuration at sulfur was determined either directly by X-ray crystallography or by correlation with closely related structures. For the axial thioglycosides oxidation leads very predominantly to the (R)(S)-diastereomer in the xylo series and exclusively so in the manno series; the configuration at C2 is of little importance in determining the stereoselectivity of oxidation of axial thioglycopyranosides. In the equatorial series the configuration at C2 has a significant effect on the outcome of the reaction as, although both series favored the (S)(S)-sulfoxide, selectivity was significantly higher in the case of the beta-mannoside than of the beta-xyloside. The two alpha-xylo sulfoxides have different conformations of the pyranoside ring with the (R)(S)-isomer adopting the (1)C(4) chair and the (S)(S)-diastereomer the (4)C(1). Each pair of diastereomeric sulfoxides was thermally equilibrated in C(6)D(6) and in CD(3)OD. In the mannose series the kinetic isomers are also thermodynamically preferred. In the xylose series, on the other hand, the nature of the thermodynamic isomer in both the alpha- and beta-anomers is a function of solvent with a switch observed on going from C(6)D(6) to CD(3)OD. The results are rationalized in terms of the exo-anomeric effect, steric shielding provided by H3 and H5 in the axial series, the interaction of the C2-O2 and sulfoxide dipoles, and increased steric interactions on hydrogen bonding of the sulfoxides to CD(3)OD. 相似文献
40.
Two new isostructural Zintl phases, EuInGe and SrInGe, are obtained from high-temperature reactions of the pure elements in welded Ta tubes. Both ternary phases crystallize in a new structure type in space group Pnma (No. 62), with a = 4.921(1) A, b = 3.9865(9) A, and c = 16.004(3) A for EuInGe; and a = 5.021(1) A, b = 4.0455(9) A, and c = 16.188(4) A for SrInGe. The crystal structures established by single-crystal X-ray diffraction feature zigzag chains of 3-bonded Ge atoms and puckered layers of 4-bonded In atoms. The two structural units are linked into an anionic network with channels composed of 5-membered and 7-membered rings. The channels are filled by the respective divalent cations. The chemical bonding of the anionic [InGe](2)(-) network, derived from a one-electron oxidative distortion of the alpha-ThSi(2) structure, is explained using extended-Hückel band structure calculations. Magnetic measurements indicate that EuInGe exhibits Curie-Weiss paramagnetic behavior above 35 K and antiferromagnetic behavior below 35 K. The calculated effective moment, mu(eff) = 8.11 mu(B), of EuInGe and the diamagnetic behavior of SrInGe are consistent with the oxidation states of Eu(II) and Sr(II), respectively. 相似文献