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941.
942.
The Bridgman anvil technique offers a simple and versatile means of generating very high pressures required in solid state
studies. The opposed anvil technique is based on the principle of massive support. The practical case of a gasketted anvil
is considered, and an expression for the maximum pressure generated under massive support is derived in terms of the geometric
parameters, the strength of the anvil material and the gasket properties. In particular, for a given maximum pressure, it
is possible to calculate the taper angle, the taper height and the gasket thickness from this expression. The anvil is assumed
to be in the elastic region under load. Good agreement is obtained between the calculated and the experimental values for
the massive support factor (msf) for various taper angles. By choosing the proper geometry, it is possible to achieve a pressure as high as 130 kbar in an
alloy steel anvil. It has been clearly found that the straight portion, where the taper ends, does not really take any part
in changing the stress pattern. Thus the minimum straight portion can serve the purpose, and will result in material saving.
Anvils exhibit yielding at very high pressure. It is also pointed out that a further strengthening of the anvil can extend
the ultimate pressure. Several methods of further strengthening the anvils are discussed. 相似文献
943.
944.
The leading infra-red divergent corrections to massive quark scattering in quantum chromodynamics are very simple to fourth order. A simple dependence on the effective coupling constant is conjectured to hold to all orders. 相似文献
945.
946.
The reactivity of atomic cobalt toward molecular oxygen in rare gas matrices has been reinvestigated. Experiments confirm that Co atoms in their a(4)F ground state are inert toward O(2) in solid argon and neon but reactive in the b(4)F first excited state, in agreement with the previous gas-phase study of Honma and co-workers. The formation of CoO(2) starting from effusive beams of Co and O(2) has been followed by IR absorption spectroscopy, both in neon and argon matrices. Our observations show that only the dioxo form, OCoO, is stabilized in the matrix and that IR absorptions previously assigned to the peroxo and superoxo forms are due to other, larger species. The present data strongly support the linear geometry in rare gas matrices proposed by Weltner and co-workers. We report on measurements on all IR-active fundamental modes for (16)OCo(16)O, (18)OCo(18)O, and (16)OCo(18)O with additional combination transitions supplying anharmonicity correction. This allows for a 5.93 +/- 0.02 mdyne/A CoO harmonic bond force constant in solid neon. Using the empirical relationship previously optimized for the CoO diatomics, an approximate value for the CoO internuclear bond distance is proposed (1.615 +/- 0.01A). In light of recent theoretical studies predicting (2)A(1) or (6)A(1) electronic ground states, the geometry and electronic structure of the OCoO molecule has also been reconsidered. Calculations carried out at the CCSD(T)/6-311G(3df) level indicate a linear structure with an r(e) = 1.62 A bond distance, consistent with the experimental estimate. For later studies of larger systems, where CCSD(T) calculations become too time-consuming, an effective DFT-based method is proposed which reproduces the basic electronic and geometrical properties of cobalt dioxide. Quantitative results are compared to the experimental data and high-level results regarding bond length and frequencies. This DFT method is used to propose a reaction pathway. 相似文献
947.
948.
I.Ralph C. Bick Mohammad A. Hai Nigel W. Preston Rex T. Gallagher 《Tetrahedron letters》1980,21(6):545-546
Aristotelinone and serratoline, two new Aristotelia alkaloids, are shown to have indole and indolenine structures respectively from their spectra and reduction products. 相似文献
949.
D. Mohammad T. Mahmood M. A. Qureshi M. Ejaz 《Journal of Radioanalytical and Nuclear Chemistry》1978,42(1):45-58
In an attempt to gain an understanding of factors affecting the extraction of iron(III) by 4-(5-nonyl)pyridine, the equilibria
between hydrogen chloride and benzene solutions of 4-(5-nonyl)pyridine have been studied. From acid distribution data and
visible absorption spectra of the organic phases, it was concluded that FeCl
4
−
ion, with a tetrahedral sp3 configuration is the principal iron containing species. The pyridine extraction of macro and trace amounts of the metal has
indicated the formation of 1∶1 and 2∶1 complexes respectively. The 2∶1 complexes are assumed to result from association of
a 1∶1 complex with a molecule of the pyridine hydrochloride. The salting-out effect increases in the order, LiCl<NaCl<MgCl2<AlCl3 and these differences in the effect have been attributed to the different degree of hydration of cations of the salts present
and to the ionic radii. The effect of various anions including the reducing agents have been described. Separation factors
of several metal ions relative to ferric iron, in 6M HCl, are also reported. 相似文献
950.
The most recently measured differential cross-section data forπ
−
p → η’n has been fitted by using a simple Regge pole model with phenomenological residue functions. It has also been observed that
this inelastic process has the scaling property. 相似文献