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91.
Jussi Väisälä 《Results in Mathematics》2005,48(1-2):184-195
We show that quasihyperbolic geodesics exist in convex domains in reflexive Banach spaces and that quasihyperbolic geodesies are quasiconvex in the norm metric in convex domains in all normed spaces. 相似文献
92.
Jussi Klemelä 《Computational Statistics》2005,20(2):349-368
Summary We present algorithms for finding the level set tree of a multivariate density estimate. That is, we find the separated components
of level sets of the estimate for a series of levels, gather information on the separated components, such as volume and barycenter,
and present the information together with the tree structure of the separated components. The algorithm proceeds by first
building a binary tree which partitions the support of the density estimate, followed by bottom-up travels of this tree during
which we join those parts of the level sets which touch each other. As a byproduct we present an algorithm for evaluating
a kernel estimate on a large multidimensional grid. Since we find the barycenters of the separated components of the level
sets also for high levels, our method finds the locations of local extremes of the estimate.
Writing of this article was financed by Deutsche Forschungsgemeinschaft under project MA1026/8-1. 相似文献
93.
This paper studies a telecommunications company's optimal networkinvestment strategies. The objective of the company is to maximizethe value of the network. According to our numerical exampleswe are not able to consider a single point-to-point connectionseparately from the network, because the network demands andcapacities affect each other. Therefore, the whole network structurehas to be considered in the point-to-point investments. 相似文献
94.
Tero Kumpulainen Jussi Pekkanen Jani Valkama Jarmo Laakso Reijo Tuokko Matti Mäntysalo 《Optics & Laser Technology》2011,43(3):570-576
New manufacturing methods are being sought for electronics production. Printable electronics is a promising method for producing low cost and large-scale electronics. In printable electronics nanoparticle inks printed on the surface of substrate contain additives, such as dispersing agent and carrier fluids that provide good printing properties by changing the viscosity and separating the nanoparticles of the ink. In the sintering process ink particles are heated to a certain, ink-specific temperature. During the sintering process the carrier fluid and dispersing agents are evaporated from the ink. Additional heating after evaporation causes the nanoparticles to start to agglomerate. A small particle size allows the use of a considerably lower sintering temperature than with bulk silver, for example 220 °C. The sintering process is usually utilized with a convection oven, with a long sintering time, and the thermal load on the surrounding material can become too great as components and patterns are formed from layers of different type inks. Hence, alternative sintering methods are sought. This paper describes tests done with two different types of laser; pulsed and continuous wave lasers. Laser sintering enables short sintering times and selective sintering, making it possible for printed structures to contain fragile active components produced with other technologies. 相似文献
95.
A generalized variant of the Calderón problem from electrical impedance tomography with partial data for anisotropic Lipschitz conductivities is considered in an arbitrary space dimension n ≥ 2. The following two results are shown: (i) The selfadjoint Dirichlet operator associated with an elliptic differential expression on a bounded Lipschitz domain is determined uniquely up to unitary equivalence by the knowledge of the Dirichlet-to-Neumann map on an open subset of the boundary, and (ii) the Dirichlet operator can be reconstructed from the residuals of the Dirichlet-to-Neumann map on this subset. 相似文献
96.
We prove, that a Hamiltonian with infinitely many δ-point interactions in the plane can be approximated in the norm resolvent sense by a family of Schrödinger operators with regular, local scaled short-range potentials. Similar well known results from the 1D and the 3D case are complemented thereby. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
97.
It is shown that the finiteness of eigenvalues in a spectral gap of a definitizable or locally definitizable selfadjoint operator in a Krein space is preserved under finite rank perturbations. This results is applied to a class of singular Sturm–Liouville operators with an indefinite weight function. 相似文献
98.
Matti Sihvonen Jussi Lintunen Elena Valkama Kari Hyytiäinen 《Natural Resource Modeling》2020,33(4):e12289
We develop a modeling framework, based on discrete-time dynamic optimization, to study the effect of legacy nutrient stores and soil nutrient dynamics on optimal nutrient management and agri-environmental policy in crop production. Three alternative measures are studied to reduce nutrient loss: reduced fertilization, nonlegume catch crop cultivation and gypsum amendment. According to our results, landowner can bring down excessively high phosphorus stocks causing environmental damage within decades, by simultaneous optimization of the nitrogen and phosphorus fertilizers on the economic basis of profit maximization. Our results suggest that nitrogen loss abatement with catch crops is socially optimal, whereas the use of gypsum is well justified as a temporary measure on soils with high soil phosphorus levels. A dynamic tax-subsidy-scheme, which takes into account the current soil nutrient levels and field attributes such as soil texture, can enforce the socially optimal outcome. The welfare losses of the static steady-state-based tax-subsidy-schemes are increasing functions of the legacy nutrient stores and soil's ability to hold nutrients. Recommendations for Resource Managers
- We develop a modeling framework to study the effect of the legacy nutrient stores and the soil nutrient dynamics on the optimal nutrient management and agri-environmental policy in crop production.
- Nonlegume catch crop cultivation is a socially optimal long-term measure for nitrogen loss abatement, whereas phosphorus loss abatement with gypsum is socially optimal on soils with high soil phosphorus levels.
- A dynamic tax-subsidy-scheme, which is adjusted annually according to the soil nutrient stocks, leads to social optimum. Although this can be difficult to implement in practice, it can be useful in the derivation of the simpler, static tax-subsidy-schemes.
- If a gypsum subsidy is paid for those years, where the soil P level is above the threshold level for the gypsum application, the welfare loss of the static steady-state-based tax-subsidy-schemes is almost zero.
- Simultaneous adjustment of the N and P fertilizer rates enables the use of simple, static and soil-texture-ignorant tax-subsidy schemes, without a notable social welfare loss
99.
100.
Antonietta Pepe Lu Zhao Juha Koikkalainen Jarmo Hietala Ulla Ruotsalainen Jussi Tohka 《Magnetic resonance imaging》2013
The study of the structural asymmetries in the human brain can assist the early diagnosis and progression of various neuropsychiatric disorders, and give insights into the biological bases of several cognitive deficits. The high inter-subject variability in cortical morphology complicates the detection of abnormal asymmetries especially if only small samples are available. This work introduces a novel automatic method for the local (vertex-level) statistical shape analysis of gross cerebral hemispheric surface asymmetries which is robust to the individual cortical variations. After segmentation of the cerebral hemispheric volumes from three-dimensional (3D) T1-weighted magnetic resonance images (MRI) and their spatial normalization to a common space, the right hemispheric masks were reflected to match with the left ones. Cerebral hemispheric surfaces were extracted using a deformable model-based algorithm which extracted the salient morphological features while establishing the point correspondence between the surfaces. The interhemispheric asymmetry, quantified by customized measures of asymmetry, was evaluated in a few thousands of corresponding surface vertices and tested for statistical significance. 相似文献