全文获取类型
收费全文 | 1049篇 |
免费 | 13篇 |
专业分类
化学 | 770篇 |
晶体学 | 10篇 |
力学 | 7篇 |
数学 | 127篇 |
物理学 | 148篇 |
出版年
2021年 | 7篇 |
2019年 | 6篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 49篇 |
2012年 | 36篇 |
2011年 | 32篇 |
2010年 | 31篇 |
2009年 | 30篇 |
2008年 | 59篇 |
2007年 | 57篇 |
2006年 | 47篇 |
2005年 | 61篇 |
2004年 | 38篇 |
2003年 | 48篇 |
2002年 | 64篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 19篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1994年 | 14篇 |
1993年 | 5篇 |
1992年 | 17篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 19篇 |
1984年 | 30篇 |
1983年 | 11篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 20篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1975年 | 21篇 |
1974年 | 8篇 |
1973年 | 7篇 |
1972年 | 5篇 |
1971年 | 6篇 |
1968年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有1062条查询结果,搜索用时 15 毫秒
101.
The sensor for adenosine-5′-triphosphate (ATP) is based on H+-ATPase immobilized via a polyvinylbutyral resin on a pH-sensitive field effect transistor. A linear relationship was obtained between the initial rate of change of the differential gate output voltage and the logarithm of the ATP concentration over the range 0.2–1.0 mM ATP. The optimum pH was 9.0 at 40°C but pH 7.0 was preferred for routine measurements. Only slight responses were obtained for 1 mM glucose, creatinine or urea. The ATP-sensing system exhibited a response to 1 mM ATP for at least 18 days. 相似文献
102.
103.
A scheduling model for a production system including machining, setup and assembly operations is considered. Production of a number of single-item products is ordered. Each product is made by assembling a set of several different parts. First, the parts are manufactured in a flow-shop consisting of multiple machines. Then, they are assembled into products on a single assembly stage. Setup operation and setup time are needed when a machine starts processing the parts or it changes items. The operations are partitioned into several blocks. Each block consists of the machining operations, the setup operations, and the assembly operation(s) for one or several products. The parts of the same item in a block are processed successively. The objective function is the mean completion time for all products. We consider a problem to partition the operations into blocks and sequence the parts in each block so as to minimize the objective function. Solution procedures using pseudo-dynamic programming and a branch-and-bound method are proposed. Computational experiments are carried out to evaluate the performance of the solution procedures. It has been found that a good near-optimal schedule is obtained efficiently by the proposed solution procedures. 相似文献
104.
Monte Carlo and quasi-Monte Carlo sampling methods for a class of stochastic mathematical programs with equilibrium constraints 总被引:1,自引:0,他引:1
Gui-Hua Lin Huifu Xu Masao Fukushima 《Mathematical Methods of Operations Research》2008,67(3):423-441
In this paper, we consider a class of stochastic mathematical programs with equilibrium constraints introduced by Birbil et al.
(Math Oper Res 31:739–760, 2006). Firstly, by means of a Monte Carlo method, we obtain a nonsmooth discrete approximation
of the original problem. Then, we propose a smoothing method together with a penalty technique to get a standard nonlinear
programming problem. Some convergence results are established. Moreover, since quasi-Monte Carlo methods are generally faster
than Monte Carlo methods, we discuss a quasi-Monte Carlo sampling approach as well. Furthermore, we give an example in economics
to illustrate the model and show some numerical results with this example.
The first author’s work was supported in part by the Scientific Research Grant-in-Aid from Japan Society for the Promotion
of Science and SRF for ROCS, SEM. The second author’s work was supported in part by the United Kingdom Engineering and Physical
Sciences Research Council grant. The third author’s work was supported in part by the Scientific Research Grant-in-Aid from
Japan Society for the Promotion of Science. 相似文献
105.
Kazuhiko Kandori Kazunao Hayashi Masaki Matsukawa Masao Fukusumi Yoshiaki Morisada 《Colloid and polymer science》2010,288(10-11):1071-1079
The shape and porosity of hematite particles, produced from a forced hydrolysis reaction of acidic FeCl3 solution, were controlled by using Pluronics as nonionic surfactants (0–4 wt.%). Pluronics possess a nominal formula of (PEO) x –(PPO) y –(PEO) x . The effect of Pluronics with low hydrophilicity (PEO contents were less than 50 mol%) was small and provided spherical particles the same as that of the system without Pluronics (control system). However, Pluronics with higher hydrophilicity (PEO contents were over 50 mol%) gave ellipsoidal hematite particles. This effect on the particle morphology was enhanced by an increase in their molecular weight. On the other hand, the Pluronics possessing an opposite nominal formula [(PPO) x –(PEO) y –(PPO) x ] exhibited no effect on the particle shape; it only depressed phase transformation from ?-FeOOH to hematite. Not only the morphology but also the pore size of hematite particles was controlled from nonporous to mesoporous by using Pluronics. The N2 adsorption experiment and t-plot curve analysis revealed that the hematite particles changed from mesoporous to microporous by an increase in the concentration of Pluronics. On the other hand, in the presence of very low amounts of Pluronics molecules (0.1 wt.%), nonporous hematite particles were produced via strong aggregation of PN particles by their hydrogen bonding between hydroxyl and PEO or PPO groups. The dynamic light scattering measurement for the system with Pluronics clarified the existence of polynuclear (PN) particles with a hydrodynamic particle diameter (D a) of ca. 40 nm after these were aged for 6 h. The size of PN particles remained constant at ca. 40 nm during aging time of 12 h~3 days, but the scattering intensity was decreased. This decrease in the scattering intensity reveals that the number of PN particles is reduced by aggregation. The transmission electron microscope, inductively coupled plasma atomic emission spectroscopy, and total organic carbon analysis measurements employed on the systems produced for ellipsoidal particles elucidated that the formation of ellipsoidal hematite particles is attributed to the adsorption of Pluronics on the surfaces of PN and growing hematite particles. 相似文献
106.
Hongli Liu Tomoko Yamashita Tadashi Kamiyama Masao Fujisawa Takayoshi Kimura 《Journal of Thermal Analysis and Calorimetry》2010,99(1):95-103
The excess molar enthalpies of 8 binary mixtures for the o-, m-, and p-isomers of fluoroiodobenzene, fluoromethoxybenzene, bromofluorobenzene, chlorofluoro-benzene, difluorobenzene, fluoromethylbenzene,
fluoronitrobenzene, and aminofluoro-benzene were measured at 298.15 K. The changes of the measured enthalpies were very small.
The experimental results revealed that the isomers containing two electron-acceptor groups showed the most positive excess
enthalpy change, while isomers containing both one electron donor and one electron acceptor group, such as aminofluorobenzene,
showed more stable and always the most negative results. 相似文献
107.
Velocity dispersion and attenuation in granular marine sediments: comparison of measurements with predictions using acoustic models 总被引:1,自引:0,他引:1
Kimura M 《The Journal of the Acoustical Society of America》2011,129(6):3544-3561
The large velocity dispersion recently reported could be explained by a gap stiffness model incorporated into the Biot model (the BIMGS model) proposed by the author. However, at high frequencies, some measured results have been reported for negative velocity dispersion and attenuation proportional to the first to fourth power of frequency. In this study, first, it is shown that the results of velocity dispersion and attenuation calculated using the BIMGS model are consistent with the results measured in two kinds of water-saturated sands with different grain sizes, except in the high-frequency range. Then, the velocity dispersion and attenuation in six kinds of water-saturated glass beads and four kinds of water-saturated silica sands with different grain sizes are measured in the frequency ranges of 80-140 and 300-700 kHz. The measured results are compared with those calculated using the BIMGS model plus some acoustic models. It is shown that the velocity dispersion and attenuation are well predicted by using the BIMGS model in the range of kd ≤ 0.5 (k: wavenumber in water, d: grain diameter) and by using the BIMGS model plus multiple scattering effects in the range of kd ≥ 0.5 in which negative velocity dispersion appears. 相似文献
108.
Peter Hockicko Peter Bury Peter Sidor Hikaru Kobayashi Masao Takahashi Takashi Yanase 《Central European Journal of Physics》2011,9(1):242-249
A set of MOS structures with thin SiO2 layers prepared by nitric acid oxidation (NAOS) method was investigated using acoustic deep level transient spectroscopy
(A-DLTS) to explain the role of annealing treatment (post-oxidation annealing (POA) and post-metallization annealing (PMA))
at different conditions on the distribution of interface states. The activation energies of interface states and the corresponding
capture cross-section were calculated both from Arrhenius plots constructed for individual peaks of the A-DLTS spectra and
applying the method of modeling of measured acoustic spectra. The energy distribution of the interface states was determined
also from the dependence of acoustoelectric response signal (ARS) on the external bias voltage (U
ac
- V
G
curves). By comparing the A-DLTS spectra, U
ac
- V
G
characteristics and some electrical measurements (G-V, I-V curves) of investigated MOS structures with no treatment with those treated with POA and/or PMA, the role of individual treatments
was observed. The definite decrease of the interface states in the structures with the PMA treatment in comparison with the
POA treatment was confirmed too. 相似文献
109.
Luís M. Fernandes Joaquim J. Júdice Hanif D. Sherali Masao Fukushima 《Journal of Global Optimization》2014,59(2-3):307-326
In this paper, a parametric algorithm is introduced for computing all eigenvalues for two Eigenvalue Complementarity Problems discussed in the literature. The algorithm searches a finite number of nested intervals \([\bar{l}, \bar{u}]\) in such a way that, in each iteration, either an eigenvalue is computed in \([\bar{l}, \bar{u}]\) or a certificate of nonexistence of an eigenvalue in \([\bar{l}, \bar{u}]\) is provided. A hybrid method that combines an enumerative method [1] and a semi-smooth algorithm [2] is discussed for dealing with the Eigenvalue Complementarity Problem over an interval \([\bar{l}, \bar{u}]\) . Computational experience is presented to illustrate the efficacy and efficiency of the proposed techniques. 相似文献
110.
This paper is concerned with the stationary problem of the Stokes equation in an infinite layer and provides a condition on
the external force sufficient for the existence of the solution. Since the Poiseuille flow is a solution to the homogeneous
equation, the solution is not unique when p = ∞. It is also proved that, under some suitable conditions, solutions to the homogeneous equation are limited only to the
Poiseuille flow. 相似文献