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101.
The kinetics of acetoxylation of cyclododecene and (E,E,E)-1,5,9-cyclododecatriene catalyzed by Pd(OAc)2 has been studied in glacial acetic acid solutions at 323–343 K and atmospheric pressure. The experimental data were described
by kinetic equations of the Michaelis-Menten type. 相似文献
102.
Vassil St. Georgiev Grace A. Bennett Lesley A. Radov Dietgard K. Kamp Laura A. Trusso 《Journal of heterocyclic chemistry》1986,23(5):1359-1362
The synthesis of a series of 2-substituted 2,3-dihydro-5H-thiazolo[2,3-b]quinazoline derivatives is described. Some of the title compounds exerted antiinflammatory and immunomodulating activities in laboratory animal models. 相似文献
103.
Summary. The mechanism of the keto-enol tautomerism of malonaldehyde was studied by ab initio methods using 6-21G** and 6-311G** basis functions at the HF level. Two separate mechanisms were examined: through-space proton transfer in the ω-shaped form
and through-space proton transfer in a sickle-shaped form obtained from the ω form by rotation. The transition state structure
of the ω form is non-planar, whereas that of the sickle form is planar. The sickle form is connected with a 2nd order saddle, indicating that there should exist a lower energy barrier, i.e. that the through-bond mechanism may be preferred. The calculated energy barriers of keto-enol tautomerism for the sickle
form is twice as high as those for the omega form.
Received January 18, 1999. Accepted (revised) August 4, 1999 相似文献
104.
V. Dimitrov 《Physics of Particles and Nuclei Letters》2011,8(4):391-394
Initially, relational model of data has been specified by E. F. Codd with the naming conventions to the attributes called
“relationship”. It is something between relations and tables, i.e., between implementation and user view on data. In this
paper, ideas for “relationship” are formally specified in Z-notation. The last one is an ISO standard now. The purpose of this paper is to reinvestigate ideas behind the “relationships”
in a more formal way. This approach is useful for further research in extending relation model of data to capture multimedia
data and data streams, which are, usually, generated by different kinds of sensors. 相似文献
105.
The behavior of the Kozachenko–Leonenko estimates for the(differential) Shannon entropy is studied when the number of i.i.d. vector-valued observations tends to infinity. The asymptotic unbiasedness and L~2-consistency of the estimates are established. The conditions employed involve the analogues of the Hardy–Littlewood maximal function. It is shown that the results are valid in particular for the entropy estimation of any nondegenerate Gaussian vector. 相似文献
106.
Ivan E. Dimitrov Ravinder Reddy John S. Leigh 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,145(2):302
Intermolecular 129Xe–1H nuclear Overhauser effects and 129Xe longitudinal relaxation time measurements were used to demonstrate that the dipole–dipole coupling is the dominant relaxation mechanism for 129Xe in water, at room temperature. 129Xe–1H cross-relaxation rates were derived to be ςXeH 3.2 ± 0.3 × 10−3 s−1, independent of xenon pressure (in the range of 1–10 bar) and of the presence of oxygen. Corresponding xenon–proton internuclear distances were calculated to be 2.69 ± 0.12 Å. Using the magnitude of the dipole–dipole coupling and the spin density ratio between dissolved xenon and bulk water, it is estimated that 129Xe–1H spin polarization-induced nuclear Overhauser effects would yield little net proton signal enhancement in water. 相似文献
107.
The space and time change of the optical density of laser-produced microplasma is studied. A statistical model is proposed which allows its utilization for assessing plasma optical density at a constant, as well as at a changing laser radiation intensity. 相似文献
108.
The oxidation of metal sulphides and sulphide concentrates was studied by means of DTA, TG and DTG curves. The behaviour of
ZnS, CdS, GaS, Tl2S, Sb2S3 and Sb2S5 during thermal treatment in an oxidizing medium was investigated. The properties of these sulphides were compared and conclusions
were drawn about their probable oxidation reactions and the kind of end-products obtained. The characteristic temperatures
of the studied sulphides were determined on the basis of curves (DTA). The values obtained were used to compare the behaviour
of the sulphides during the oxidation process in a fluid bed. The results can be used to improve the technological and economic
indices in the industrial production of zinc.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
109.
Excited‐state deactivation channels via internal conversions in two position isomers of hydroxy‐methyl‐pyridine: a theoretical study
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Two position isomers of hydroxy‐methyl‐pyridine (3‐hydroxy‐2‐methyl‐pyridine and 2‐hydroxy‐3‐methyl‐pyridine) were studied theoretically at the BLYP level of theory in order to find mechanisms explaining the excited‐state deactivations of isomers through ring puckering and “ethylene‐like” conical intersections. The study aims also to clarify the mechanisms of the ground‐state proton transfers. Three conical intersections S0/S1 for each isomer were found, which are accessible through the 1ππ* excited states. In both isomers, there is a 1ππ* excited‐state reaction path, which leads, in a completely barrierless manner, to the one of the conical intersections S0/S1. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
110.
Said El‐Kurdi Abdal‐Azim Al‐Terkawi Bernd M. Schmidt Anton Dimitrov Dr. Konrad Seppelt Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(2):595-599
WF6 reacts with phosphines R3P forming 1:1 compounds. With R=P(CH3)3 the coordination around the tungsten atom is capped trigonal prismatic, with R=P(CH3)2C6H5 the coordination is capped octahedral, as established by single‐crystal structure determinations: [(CH3)3P? WF6]: a=752.5(21), b=945.7(24), c=629.8(18) pm. β=110.36(13)°, space group Cm, Z=2; [(CH3)2(C6H5)P? WF6]: a=762.2(2), b=1123.5(2), c=2647.5(6) pm, space group Pbca, Z=8. [(CF3CH2)2N? WF5] reacts smoothly with P(C6H5)3 forming known P(C6H5)3(F)2 and [(CF3CH2)2N? WF4? P(C6H5)3], a stable, green, molecular species, identified among other methods with an crystal structure determination: a=914.9(1), b=956.0(1), c=1449.8(2) pm, α=7.642(4), β=81.648(3), γ=81.519°, space group P$\bar 1$ , Z=2. 相似文献