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41.
The subsystem synthesis method has been developed in order to improve computational efficiency for a multibody vehicle dynamics model. Using the subsystem synthesis method, equations of motion of the base body and each subsystem can be solved separately. In the subsystem synthesis method, various coordinate systems can be used and various integration methods can be applied in each subsystem, as long as the effective mass matrix and the effective force vector are properly produced. In this paper, comparative study has been carried out for the subsystem synthesis method with Cartesian coordinates and with joint relative coordinates. Two different integration methods such as an explicit integrator and an explicit implicit integrator are employed. In order to see the accuracy and computational efficiency from the different models based on the different coordinate systems and different integration methods, a rough terrain run simulations has been carried out with a 6 × 6 off-road multibody vehicle model. 相似文献
42.
Boo Rim Choe Hyungwoon Koo Michael Stessin 《Integral Equations and Operator Theory》2009,63(4):501-520
We obtain new characterizations of Carleson measures via uniform boundedness of BMO norms of certain mass functions associated
with the given measure in a natural way.
This research was performed during M. Stessin’s visit to Korea University. He thanks the Mathematics Department of Korea University
and the “Brain Pool” program for their hospitality and support. The first two authors were supported by the Korea Research
Foundation Grant funded by the Korean Government (KRF-2008-314-C00012). 相似文献
43.
The energy gradient method has been proposed with the aim of better
understanding the mechanism of flow transition from laminar flow to
turbulent flow. In this method, it is demonstrated that the transition
to turbulence depends on the relative magnitudes of the transverse gradient
of the total mechanical energy which amplifies the disturbance and the energy
loss from viscous friction which damps the disturbance, for given imposed
disturbance. For a given flow geometry and fluid properties, when the maximum
of the function $K$ (a function standing for the ratio of the gradient of total
mechanical energy in the transverse direction to the rate of energy loss due to
viscous friction in the streamwise direction) in the flow field is larger than a
certain critical value, it is expected that instability would occur for some
initial disturbances. In this paper, using the energy gradient analysis, the
equation for calculating the energy gradient function $K$ for plane Couette flow
is derived. The result indicates that $K$ reaches the maximum at the moving walls.
Thus, the fluid layer near the moving wall is the most dangerous position to generate
initial oscillation at sufficient high $\operatorname{Re}$ for given same level of
normalized perturbation in the domain. The critical value of $K$ at turbulent transition,
which is observed from experiments, is about 370 for plane Couette flow when two walls
move in opposite directions (anti-symmetry). This value is about the same as that for
plane Poiseuille flow and pipe Poiseuille flow (385-389). Therefore, it is concluded
that the critical value of $K$ at turbulent transition is about 370-389 for wall-bounded
parallel shear flows which include both pressure (symmetrical case) and shear driven
flows (anti-symmetrical case). 相似文献
44.
Boo YC 《Experimental & molecular medicine》2006,38(1):63-71
Fluid shear stress plays a critical role in vascular health and disease. While protein kinase A (PKA) has been implicated in shear-stimulated signaling events in endothelial cells, it remains unclear whether and how PKA is stimulated in response to shear stress. This issue was addressed in the present study by monitoring the phosphorylation of endogenous substrates of PKA. Shear stress stimulated the phosphorylation of cAMP responsive element binding protein (CREB) in a PKA-dependent manner. Western blot analysis using the antibody reactive against the consensus motif of PKA substrates detected two proteins, P135 and P50, whose phosphorylation was increased by shear stress. The phosphorylation of P135 was blocked by a PKA inhibitor, H89, but not by a phosphoinositide 3-kinase inhibitor, wortmannin. Expression of a constitutively active PKA subunit stimulated P135 phosphorylation, supporting the potential of P135 as a PKA substrate. P135 was identified as endothelial nitric oxide synthase (eNOS) by immunoprecipitation study. PKA appeared to mediate shear stress-stimulated eNOS activation. Shear stress stimulated intracellular translocation of PKA activity from 'soluble' to 'particulate' fractions without involving cellular cAMP increase. Taken together, this study suggests that shear stress stimulates PKA-dependent phosphorylation of target proteins including eNOS, probably by enhancing intracellular site-specific interactions between protein kinase and substrates. 相似文献
45.
Koo HY Lee HJ Go HA Lee YB Bae TS Kim JK Choi WS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(4):1214-1219
We report the synthesis of graphenes with tunable properties due to the growth of needlelike iron oxide (IO) nanoparticles on their surfaces. The electrical conductivity, flexibility, and magnetic properties of graphene nanosheets (GNSs) could be tuned on demand by fine controlling both the surface coverage and the length of the IO nanoneedles. The degree of coverage of the IO nanoparticles on the surface of the GNSs made it possible to control the resulting properties of the IO/GNSs on demand. As examples of their utility, paperlike materials were generated by simple filtration, and the resulting IO/GNS nanocomposites showed extraordinary removal capacity and fast adsorption rates for As(V) and Cr(VI) ions in water. Another possible application is the preparation of multifunctional films equipped with conductivity, flexibility, and magnetic properties. The fabrication process is easy to scale up at a low cost. In addition, both the colloidal solution and film forms of the resulting IO/GNSs were effective for removal of heavy metal ions, meaning this material could be utilized for actual industrial applications. 相似文献
46.
Sejin Park Taek Dong Chung Sun Kil Kang Ran-A Jeong Hankil Boo Hee Chan Kim 《Analytical sciences》2004,20(12):1635-1638
Amperometric glucose sensors were fabricated using glucose oxidase (GOx) entrapped in zirconium hydrogenphosphate (ZrP), and their performance was evaluated. Reportedly, alpha-ZrP is one of the candidates that are expected to improve the stability of enzymes immobilized on solid surfaces. We intercalated GOxs into ZrP (GOx/ZrP), cast the GOx/ZrP suspension in polyvinylalcohol on a platinum electrode, and dried it in a vacuum oven. The morphological layered structure was investigated by scanning electron microscopy. The enzymatic activities, which were determined by open-circuit potentiometric technique, reached the highest when GOxs were immobilized in ZrP at ca. pH 5. In vitro tests showed good linear responses in the 0-25 mM range and the sensitivity of 0.14 nA mM(-1) at 0.4 V vs. Ag/AgCl. The sensors, as made, were stable for more than 3 days within a limited deterioration. 相似文献
47.
Boo Rim Choe Hyungwoon Koo Wayne Smith 《Transactions of the American Mathematical Society》2003,355(7):2829-2855
We study the action of composition operators on Sobolev spaces of analytic functions having fractional derivatives in some weighted Bergman space or Hardy space on the unit disk. Criteria for when such operators are bounded or compact are given. In particular, we find the precise range of orders of fractional derivatives for which all composition operators are bounded on such spaces. Sharp results about boundedness and compactness of a composition operator are also given when the inducing map is polygonal.
48.
Dynamics and energetics for intramolecular excimer formation of a diarylsilane, di-9H-fluoren-9-yldimethylsilane (DFYDMS) have been investigated by means of ps time-resolved fluorescence spectroscopy and ab initio calculation. Multiple fluorescence decay curves were globally deconvolved to generate time-resolved fluorescence spectra and decay-associated spectra (DAS), from which species-associated spectra (SAS) were obtained. It is shown in the global analysis that there are at least three excited states: Two states are the locally excited (LE) states (lambda(max) approximately 320 nm) having lifetimes of 0.70 +/- 0.04 and 1.75 +/- 0.02 ns, and another is the excimer state (lambda(max) approximately 400 nm) having a lifetime of 7.34 +/- 0.02 ns. The species which decays with 0.70 ns evolves into a species with a red-shifted spectrum, which in turn decays in 7.34 ns. The experimental and ab initio results indicate that the rise time of 0.70 ns corresponds to the conversion of the initial S(1) LE state having a near sandwich geometry to the S(1) excimer state adopting a true sandwich geometry. 相似文献
49.
[reaction: see text] Bicyclic and tricyclic gamma-butyrolactones with 5,7-, 5,6,5-, 5,6,6-, or 5,7,5-fused ring systems, being found in xanthanolides, eudesmanolides, and guaianolides, were readily synthesized from methyl furan-2-carboxylic acid. Key steps were a copper(I)-catalyzed asymmetric cyclopropanation, Sakurai allylations, intramolecular ene reactions, and ring-closing metathesis reactions. 相似文献
50.
Siew Wan Fong Deepak Adhikari Evert Klaseboer Boo Cheong Khoo 《Experiments in fluids》2009,46(4):705-724
This paper aims to study the complex interaction between multiple bubbles, and to provide a summary and physical explanation
of the phenomena observed during the interaction of two bubbles. High-speed photography is utilized to observe the experiments
involving multiple spark-generated bubbles. Numerical simulations corresponding to the experiments are performed using the
Boundary Element Method (BEM). The bubbles are typically between 3 and 5 mm in radius and are generated either in-phase (at
the same time) or with phase differences. Complex phenomena are observed such as bubble splitting, and high-speed jetting
inside a bubble caused by another collapsing bubble nearby (termed the ‘catapult’ effect). The two-bubble interactions are
broadly classified in a graph according to two parameters: the relative inter-bubble distance and the phase difference (a
new parameter introduced). The BEM simulations provide insight into the physics, such as bubble shape changes in detail, and
jet velocities. Also presented in this paper are the experimental results of three bubble interactions. The interesting and
complex observations of multiple bubble interaction are important for a better understanding of real life applications in
medical ultrasonic treatment and ultrasonic cleaning. Many of the three bubble interactions can be explained by isolating
bubble pairs and classifying their interaction according to the graph for the two bubble case. This graph can be a useful
tool to predict the behavior of multiple bubble interactions. 相似文献