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211.
212.
213.
Cwiklik L Buck U Kulig W Kubisiak P Jungwirth P 《The Journal of chemical physics》2008,128(15):154306
Ab initio molecular dynamics simulations modeling low-energy collisions of a sodium atom with a cluster with more than 30 water molecules are presented. We follow the dynamics of the atom-cluster interaction and the delocalization of the valence electron of sodium together with the changes in the electron binding energy. This electron tends to be shared by the nascent sodium cation and the water cluster. IR spectra of the sodium-water cluster are both computationally and experimentally obtained, with a good agreement between the two approaches. 相似文献
214.
Leitenberger SM Reister-Gottfried E Seifert U 《Langmuir : the ACS journal of surfaces and colloids》2008,24(4):1254-1261
We consider the lateral diffusion of a protein interacting with the curvature of the membrane. The interaction energy is minimized if the particle is at a membrane position with a certain curvature that agrees with the spontaneous curvature of the particle. We employ stochastic simulations that take into account both the thermal fluctuations of the membrane and the diffusive behavior of the particle. In this study, we neglect the influence of the particle on the membrane dynamics, thus the membrane dynamics agrees with that of a freely fluctuating membrane. Overall, we find that this curvature coupling substantially enhances the diffusion coefficient. We compare the ratio of the projected or measured diffusion coefficient and the free intramembrane diffusion coefficient, which is a parameter of the simulations, with analytical results that rely on several approximations. We find that the simulations always lead to a somewhat smaller diffusion coefficient than that from our analytical approach. A detailed study of the correlations of the forces acting on the particle indicates that the diffusing inclusion tries to follow favorable positions on the membrane such that forces along the trajectory are on average smaller than they would be for random particle positions. 相似文献
215.
A new hierarchy of augmented basis sets optimized for the calculation of molecular properties such as indirect spin-spin coupling constants is presented. Based on the Dunning hierarchy of cc-pVXZ (X = D, T, Q, and 5) basis sets augmentation functions with tight exponents have been optimized for coupled-cluster calculations of indirect spin-spin coupling constants. The optimal exponents for these tight functions have been obtained by optimizing the sum of the absolute values of all contributions to the coupling constant. On the basis of a series of test cases (CO, HF, N(2), F(2), H(2)O, NH(3), and CH(4)) we propose a set of tight s, p, and d functions to be added to the uncontracted Dunning basis sets, and, subsequently, to recontract. The resulting ccJ-pVXZ (X = D, T, Q, and 5) basis sets demonstrate excellent cost efficiency in benchmark calculations. These new basis sets should generally be applicable for the calculation of spin-spin coupling constants and other properties that have a strong dependence on powers of 1r or even contain a delta distribution for correlated ab initio methods. 相似文献
216.
Joachim Zuschrader Gerald Reiter Heinz Falk 《Monatshefte für Chemie / Chemical Monthly》2008,139(8):995-998
An ω,ω′-disubstituted hypericin derivative bearing two dicyclohexylurea moieties separated by propionyl chains from the chromophore and an ω,ω′-dithioacetal of hypericin were prepared. Both showed excellent production of oxidizing species comparable to hypericin when irradiated with appropriate light as shown by the photodestruction of bilirubin IXα. 相似文献
217.
The mono- and bis-iodo-substituted NHC-stabilized alanes (NHC) ⋅ AlH2I and (NHC) ⋅ AlHI2 offer a convenient entry for further substitution reactions at aluminum. Reactions of (NHC) ⋅ AlH2I 1 – 4 with one equivalent of NaCp afforded the adducts (NHC) ⋅ AlH2Cp 9 – 12 (NHC=Me2ImMe ( 9 ), iPr2ImMe ( 10 ), iPr2Im ( 11 ), Dipp2Im ( 12 )). Alane adducts with two Cp substituents (NHC) ⋅ AlHCp2 13 – 16 (NHC=Me2ImMe ( 13 ), iPr2ImMe ( 14 ), iPr2Im ( 15 ), Dipp2Im ( 16 )) were prepared by the analogous reaction of (NHC) ⋅ AlHI2 5 – 8 using two equivalents of NaCp. The unusual dimeric adducts ((NHC) ⋅ AlH2Cp ⋅ CpMgI)2 17 – 19 (NHC=Me2ImMe ( 17 ), iPr2ImMe ( 18 ), iPr2Im ( 19 )) were obtained from the reaction of 1 – 3 with MgCp2. 相似文献
218.
219.
G. Reiter G. Castelein P. Hoerner G. Riess J.-U. Sommer G. Floudas 《The European physical journal. E, Soft matter》2000,2(4):319-334
Spin-coated thin films of about 100nm of low-molecular-weight hydrogenated poly(butadiene-b- ethyleneoxide) (PBh-PEO) diblock copolymers have been crystallized at various constant temperatures. Crystallization has been observed in real
time by light microscopy. Detailed structural information was obtained by atomic force microscopy, mainly enabled by the large
viscoelastic contrast between amorphous and crystalline regions. The behavior in thin films is compared to the bulk properties
of the polymer. Crystallization started from an annealed microphase separated melt where optical microscopy indicated a lamellar
orientation parallel to the substrate. A small difference in the length of the crystallizable block produced significantly
different crystallization behavior, both in the bulk and in thin films. For thin films of the shortest diblock copolymer (45%
PEO content) and for an undercooling larger than about 10 degrees, crystallization created vertically oriented lamellae. These
vertical lamellae could be preferentially aligned over several micrometers when crystallization occurred close to a three-phase
contact line. Annealing at temperatures closer to the melting point or keeping the sample at room temperature for several
months allowed the formation of a lamellar structure parallel to the substrate. A tentative interpretation based on kinetically
caused chain folding and relaxation within the crystalline state, with implications on general aspects of polymer crystallization,
is presented.
Received 19 March 1999 and Received in final form 14 December 1999 相似文献
220.
The eigenvalue analysis of rolling tires is one part of the simulation of tire rolling noise radiation for the reduction of traffic noise. In this paper the general strategies of numerical eigenvalue analysis for nonsymmetric matrices are shown. The special effects observed on rotating bodies are discussed in details. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献