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991.
Christian Gancet Rosangela Pirri Jean Marc Dalens Bernard Boutevin Bernard Guyot Cdric Loubat Jean Le Petit Anne Marie Farnet Simone Tagger 《Macromolecular Symposia》1999,144(1):211-217
The biodegradability of polyacrylic acid derivatives may be improved through introduction of some fragility points within the main carbon chains. These weakness points can be either hydrolizable bonds or oxidizable sites. Enzymatic hydrolysis and oxydative biomimetic degradation tests have been set up in order to quickly evaluate new polymeric structures, before their possible evaluation through microbial degradation by Candida tropicalis. 相似文献
992.
Marc A. Little Jonathan J. Loughrey Amedeo Santoro Malcolm A. Halcrow Michaele J. Hardie 《Tetrahedron letters》2014
The synthesis of four 3,4-di(alkylsulfanyl)benzyl alcohol derivatives is described, in five steps from methyl 3,4-di(hydroxy)benzoate via a Newman–Kwart rearrangement. Incubation of these derivatives in formic acid affords 2,3,7,8,12,13-hexakis(alkylsulfanyl)-10,15-dihydro-5H-tribenzo[a,d,g]cyclononene products, which are hexa-sulfanyl analogues of the well-known supramolecular cavitand host, cyclotriveratrylene (CTV). The yield of this cyclization depends strongly on the alkylsulfanyl substituents present, in the order SMe > SEt ≈ SiPr ? SBn. A crystal structure determination of one of the cyclotrimers shows a mode of self-association that is commonly exhibited by CTV itself. 相似文献
993.
994.
995.
André L. Beauchamp Stephan Latour Marc J. Olivier James D. Wuest 《Journal of organometallic chemistry》1983,254(3):283-291
The title compound, C58H52Sn3, belongs to the triclinic space group P, with a 10.165, b 13.365, c 18.670 Å, α 96.28, β 93.88, γ 103.15°, V = 2443.8 Å3, fw = 1105.1, Z = 2, Dcalc 1.501 g cm?3, m.p. 206.5–208°C, λ(Mo-K) 0.71069 Å. The structure was refined on 2684 nonzero reflections to an R factor of 0.044. The crystal contains molecules in which the (SnCH2)3CH core possesses an approximate C3 symmetry. The three SnC(H2) bonds are gauche to the C(4)-H bond. Repulsive interactions involving the bulky Ph3Sn substituents lead to large SnC(H2)C(H) angles (av. 117.3°), whereas the C(H2)C(H)C(H2) angles at the tertiary carbon average 111.3°. Little distortion of the Ph3Sn groups themselves is present, since the PhSnPh angles (av. 109.8°) are almost equal to the C(H2)SnPh angles (av. 109.9°). The molecule as a whole has no symmetry because the aromatic rings in the three Ph3Sn groups have different orientations. The phenyl groups create a pocket in the middle of the molecule which encloses and shields the tertiary hydrogen atom. The resulting inaccessibility of this hydrogen accounts in part for the low reactivity of the title compound in redox reactions. 相似文献
996.
A nonlocal species concentration theory for diffusion and phase changes is introduced from a nonlocal free energy density. It can be applied, say, to electrode materials of lithium ion batteries. This theory incorporates two second-order partial differential equations involving second-order spatial derivatives of species concentration and an additional variable called nonlocal species concentration. Nonlocal species concentration theory can be interpreted as an extension of the Cahn–Hilliard theory. In principle, nonlocal effects beyond an infinitesimal neighborhood are taken into account. In this theory, the nonlocal free energy density is split into the penalty energy density and the variance energy density. The thickness of the interface between two phases in phase segregated states of a material is controlled by a normalized penalty energy coefficient and a characteristic interface length scale. We implemented the theory in COMSOL Multiphysics\(^{\circledR }\) for a spherically symmetric boundary value problem of lithium insertion into a \(\hbox {Li}_x\hbox {Mn}_2\hbox {O}_4\) cathode material particle of a lithium ion battery. The two above-mentioned material parameters controlling the interface are determined for \(\hbox {Li}_x\hbox {Mn}_2\hbox {O}_4\), and the interface evolution is studied. Comparison to the Cahn–Hilliard theory shows that nonlocal species concentration theory is superior when simulating problems where the dimensions of the microstructure such as phase boundaries are of the same order of magnitude as the problem size. This is typically the case in nanosized particles of phase-separating electrode materials. For example, the nonlocality of nonlocal species concentration theory turns out to make the interface of the local concentration field thinner than in Cahn–Hilliard theory. 相似文献
997.
Amin Abdolvand Robert W. Lloyd Marc J. J. Schmidt David J. Whitehead Zhu Liu Lin Li 《Applied Physics A: Materials Science & Processing》2009,95(2):447-452
We present results on the growth of highly organised, reproducible, periodic microstructure arrays on a stainless steel substrate
using multi-pulsed Nd:YAG (wavelength of 1064 nm, pulse duration of 7 ns, repetition rate of 25 kHz, beam quality factor of
M
2∼1.5) laser irradiation in standard atmospheric environment (room temperature and normal pressure) with laser spot diameter
of the target being ∼50 μm. The target surface was irradiated at laser fluence of ∼2.2 J/cm2 and intensity of ∼0.31×109 W/cm2, resulting in the controllable generation of arrays of microstructures with average periods ranging from ∼30 to ∼70 μm, depending
on the hatching overlap between the consecutive scans. The received tips of the structures were either below or at the level
of the original substrate surface, depending on the experimental conditions. The peculiarity of our work is on the utilised
approach for scanning the laser beam over the surface. A possible mechanism for the formation of the structures is proposed. 相似文献
998.
Marc Wouts 《Communications in Mathematical Physics》2009,289(1):157-204
We study the surface tension and the phenomenon of phase coexistence for the Ising model on with ferromagnetic but random couplings. We prove the convergence in probability (with respect to random couplings) of surface
tension and analyze its large deviations: upper deviations occur at volume order while lower deviations occur at surface order.
We study the asymptotics of surface tension at low temperatures and relate the quenched value τ
q
of surface tension to maximal flows (first passage times if d = 2). For a broad class of distributions of the couplings we show that the inequality –where τ
a
is the surface tension under the averaged Gibbs measure – is strict at low temperatures. We also describe the phenomenon
of phase coexistence in the dilute Ising model and discuss some of the consequences of the media randomness. All of our results
hold as well for the dilute Potts and random cluster models. 相似文献
999.
Four potential metabolites of the potassium-competitive acid blocker BYK 405879 (1) were synthesized which might be formed in vivo by enzymatic oxidation of the pyran moiety or the methyl groups attached to the (hetero) aromatic system. In all cases, the oxidation of the parent compound 1 was accompanied by a significant loss of pharmacological activity and by a decrease in lipophilicity. The target compounds 6, 14, 20, and 21 constitute valuable tool substances for the investigation of the metabolic fate of BYK 405879 (1). 相似文献
1000.
The synthesis of a polypseudorotaxane, polyrotaxane, and polycatenane containing the electron-deficient cyclophane cyclobis(paraquat-p-phenylene) (CBPQT4+) subunit in the side chain is described. These interlocked supramolecular polymers have been prepared from an azide-functionalized polystyrene derivative and an acetylene-functionalized [2]rotaxane, [2]catenane and their parent tetracationic cyclophane via Cu(I)-catalyzed 1,3 dipolar cycloadditions (‘click chemistry’). The synthesis and characterization of the polymers and intermediates has been described using IR, 1H NMR, UV spectroscopies, and voltammetry. We have shown that the CBPQT4+ unit of the side chain polystyrene derivative has the ability to reversibly undergo complexation with a complementary dialkoxynaphthalene derivative. 相似文献