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81.
蛋白质分子与配体的作用模式主要有直接的环区结合及铰链式结合两种方式。针对这两种不同的作用方式,我们提出采用不同的策略进行结合过程的构象研究。对于直接的环区结合模式,通过建立环区主链构象库,来实现蛋白质环区与配体的准柔性对接,并以链霉抗生物素蛋白体系为例对构象库建立的可行性进行了验证计算。对铰链结合方式,采用分步对接的方法进行计算,并具体应用于HIV蛋白酶与其小分子配体的结合过程。计算结果表明,这两种处理方法分别能较好地模拟不同类型的蛋白质与配体结合的的构象变化。 相似文献
82.
We present a molecular dynamics study of the solvation properties of large spherical ions S+ and S− of same size, in water, chloroform and acetonitrile solutions, and at a water–chloroform interface. According to the “extrathermodynamic” TATB hypothesis, such ions have identical free energies of transfer from water to any solvent. We find that this is not the case, because S− interacts better than S+ with water (by about 20 kcal mol−1), while S+ is better solvated by acetonitrile (by about 2 kcal mol−1) and chloroform (about 8 kcal mol−1) solvents. The importance of “long-range” electrostatic interactions on the charge discrimination by solvent is demonstrated by the comparison of standard vs corrected methods to calculate: (i) the electrostatic potential at the centre of the solute; (ii) the interaction energies between the ions and the solvents; and (iii) the free energies of charging the neutral sphere S0 to S+ and S−, respectively. These conclusions are obtained with several solvent models and simulation conditions. The question of ion pairing for the S+S−, S+Cl− and S−Na+ pairs is also examined in the three solvents. Finally, simulations at a liquid–liquid water–chloroform interface represented explicitly, show that S+ and S− are highly surface active, although they do not possess, like classical surfactants, an amphiphilic topology. Adsorption at the interface is found with different methodologies and at different ion concentrations. These results are important in the context of the “TATB hypothesis”, and for our understanding of solvation of large hydrophobic ions in pure liquids or in heterogeneous liquid environments. 相似文献
83.
A fractal model of a filled polymer is proposed. The model allows us to estimate quantitatively the volume of an interphase,
to take into account geometrical factors influencing the character and the interphase adhesion level, and to predict the mechanical
strength of interfacial bonds. This makes it possible to calculate the size of the critical structural defect and the mechanical
properties of filled polymers, which are in agreement with the experimental data.
Translated from Mekhanika Kompozitnykh Materialov, Vol. 36, No. 1, pp. 3–32, January–February, 2000. 相似文献
84.
85.
We investigate properties of square-Gaussian stochastic processes. These processes are formed by quadratic forms of Gaussian processes or by limits in the mean square of quadratic forms of Gaussian processes. Special classes of these processes are determined and investigated. For processes from these classes estimates of large deviation probability are obtained. These estimates we use to estimate the probability that Gaussian vector-valued process leave some region on some interval of time. We construct asymptotic confidence regions for estimates of covariance functions of vector-valued Gaussian processes. Criterion of hypothesis testing on covariance functions of these processes is constructed. 相似文献
86.
We examine two point particles interacting via a smooth Lennard-Jones-type potential of finite range on a two-dimensional torus. We find situations under which this system contains a stable, elliptic periodic orbit and hence is not ergodic. This result is in contrast to the case of hard spheres interacting via inelastic collision, which are always ergodic for two particles, are conjectured to be ergodic for arbitrarily many particles, and can never contain elliptic periodic orbits. 相似文献
87.
88.
André Mas 《Statistical Inference for Stochastic Processes》2007,10(2):147-163
Let X
1,...,X
n
be an i.i.d. sample of random curves, viewed as Hilbert space valued random elements, with mean curve m. An asymptotic test of m = m
0 vs m ≠ m
0 is proposed, when m
0 is a fixed known function. The test statistics converges under very mild assumptions and relies on the pseudo-inversion of
the covariance operator (leading to a non standard inverse problem). The power against local alternatives is investigated.
In final form November 2004 相似文献
89.
Geoffrey S Watson 《Journal of multivariate analysis》1984,14(1):74-82
The density of the Langevin (or Fisher-Von Mises) distribution is proportional to exp κμ′x, where x and the modal vector μ are unit vectors in q. κ (≥0) is called the concentration parameter. The distribution of statistics for testing hypotheses about the modal vectors of m distributions simplify greatly as the concentration parameters tend to infinity. The non-null distributions are obtained for statistics appropriate when κ1,…,κm are known but tend to infinity, and are unknown but equal to κ which tends to infinity. The three null hypotheses are H01:μ = μ0(m=1), H02:μ1 = … =μm, H03:μi?V, i=1,…,m In each case a sequence of alternatives is taken tending to the null hypothesis. 相似文献
90.
At the Third International Congress of Mathematicians Julius König gave a flawed refutation of Cantor's continuum hypothesis and the well-ordering theorem. A newly discovered postcard of Zermelo to Max Dehn supports the view that Zermelo quickly detected the gap in König's argument. This is in contrast to more recent views that attribute this role exclusively to Hausdorff. 相似文献