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21.
In the present paper, a multifluid model of two-phase flows with pulverized-coal combustion, based on a continuum-trajectory
model with reacting particle phase, is developed and employed to simulate the 3-D turbulent two-phase flows and combustion
in a new type of pulverized-coal combustor with one primary-air jet placed along the wall of the combustor. The results show
that: (1) this continuum-trajectory model with reacting particle phase can be used in practical engineering to qualitatively
predict the flame stability, concentrations of gas species, possibilities of slag formation and soot deposition, etc.; (2)
large recirculation zones can be created in the combustor, which is favorable to the ignition and flame stabilization.
Sponsored by the National Key Projects of Fundamental Research of China. 相似文献
22.
By means of an asymptotic expansion method of a regular series, an exact higher-order analysis has been carried out for the
near-tip fields of an interfacial crack between two different elastic-plastic materials. The condition of plane strain is
invoked. Two group of solutions have been obtained for the crack surface conditions: (1) traction free and (2) frictionless
contact, respectively. It is found that along the interface ahead of crack tip the stress fields are co-order continuous while
the displacement fields are cross-order continuous. The zone of dominance of the asymptotic solutions has been estimated.
The project supported by the National Natural Science Foundation of China 相似文献
23.
In a vertically oscillating circular cylindrical container, singular perturbation theory of two-time scale expansions is developed in weakly viscous fluids to investigate the motion of single free surface standing wave by linearizing the Navier-Stokes equation. The fluid field is divided into an outer potential flow region and an inner boundary layer region. The solutions of both two regions are obtained and a linear amplitude equation incorporating damping term and external excitation is derived. The condition to appear stable surface wave is obtained and the critical curve is determined. In addition, an analytical expression of damping coefficient is determined. Finally, the dispersion relation, which has been derived from the inviscid fluid approximation, is modified by adding linear damping. It is found that the modified results are reasonably closer to experimental results than former theory. Result shows that when forcing frequency is low, the viscosity of the fluid is prominent for the mode selection. However, when forcing frequency is high, the surface tension of the fluid is prominent. 相似文献
24.
在高超声速飞行条件下, 流入冲压发动机燃烧室并降至低速的空气温度, 随着飞行马赫数增
加升得愈来愈高. 燃料与高温空气混合燃烧释放的化学能将部分转化为解离能. 这些解离能
在长度受限的尾喷管中难以充分复合形成推力, 使冲压发动机性能随飞行马赫数增大而急剧
下降. 导致冲压发动机不适应高超声速飞行器的推进要求. 将此定名为``高超声障'. 半个
世纪以来, 广泛采用``超声速燃烧'降低流入燃烧室的空气温度来克服这种障碍. 虽已取得
不少进展, 然而关键性难点仍需继续攻克. 为了多途径促进吸气推进高超声速飞行的实现,
提出克服``高超声障'的另一种思路:保持现有冲压发动机吸气与燃烧方式, 通过催化促进
燃气解离组分在尾喷管膨胀过程中的复合, 增大冲压发动机的推力, 达到满足高超声速飞行
器的推进要求. 相似文献
25.
在JP10和煤油点火特性激波管实验的基础上,实验研究了硅烷对这两种典型高碳数碳氢燃
料点火特性的影响. 在预加热到70 C的激波管上,采用缝合运行条件获得了近7ms
的实验时间,将实验延伸至低温区. 采用气相色谱分析和高精度真空仪直接测定压力相结合
的方法,确定了燃料气相浓度,解决了高碳数碳氢燃料点火激波管实验时由于管壁吸附影响
燃料气相浓度确定的困难. 实验记录了点火过程中OH自由基发射强度变化,并作为判断点
火发生的标志. 实验温度范围880~1800K, 压力范
围0.16~0.53\,MPa. 当硅烷加入量约为燃料的10%~15%(摩尔比),
质量比为2%~3%, 观测到明显的点火促进作用. 该研究对超燃研究中发动机设计、
燃料选择等方面具有直接的工程意义,也可用于检验燃烧化学动力学模型的合理性. 相似文献
26.
In the paper the wave attenuation in a two layer fluid system is studied. The fluid in the top layer is ideal and that in
the lower layer is the Voigt model of the viscoelastic medium. A dispersion relation is derived and the rate of the wave decay
is computed. The approximate explicit expressions of the decay rate for different water depth are given, where the viscoelasticity
is either very large or very small. Compared with the numerical results, our results are very accurate, which can be used
by an engineer.
The project supported by the National Natural Science Foundation of China and by the Lianyungang Port Office, China 相似文献
27.
The motion of a single spherical small bubble due to buoyancy in the ideal fluid with waves is investigated theoretically
and experimentally in this article. Assuming that the bubble has no effect on the wave field, equations of a bubble motion
are obtained and solved. It is found that the nonlinear effect increases with the increase of the bubble radius and the rising
time. The rising time and the motion orbit are given by calculations and experiments. When the radius of a bubble is smaller
than 0.5mm and the distance from the free surface is greater than the wave height, the results of the present theory are in
close agreement with measurements.
The project supported by the National Natural Science Foundation of China 相似文献
28.
Molecular dynamics simulation of crack-tip processes in copper 总被引:1,自引:0,他引:1
The crack tip processes in copper under mode II loading have been simulated by a molecular dynamics method. The nucleation,
emission, dislocation free zone (DFZ) and pile-up of the dislocations are analyzed by using a suitable atom lattice configuration
and Finnis & Sinclair potential. The simulated results show that the dislocation emitted always exhibits a dissociated fashion.
The stress intensity factor for dislocation nucleation, DFZ and dissociated width of partial dislocations are strongly dependent
on the loading rate. The stress distributions are in agreement with the elasticity solution before the dislocation emission,
but are not in agreement after the emission. The dislocation can move at subsonic wave speed (less than the shear wave speed)
or at transonic speed (greater than the shear wave speed but less than the longitudinal wave speed), but at the longitudinal
wave speed the atom lattice breaks down.
The project supported by the National Natural Science Foundation of China 相似文献
29.
A coupled map lattices with convective nonlinearity or, for short, Convective Coupled Map (CCM) is proposed in this paper
to simulate spatiotemporal chaos in fluid flows. It is found that the parameter region of spatiotemporal chaos can be determined
by the maximal Liapunov exponent of its complexity time series. This simple model implies a similar physical mechanism for
turbulence such that the route to spatiotemporal chaos in fluid flows can be envisaged.
The study is supported by “Nonlinear Sciences Project” from the State Science and Technology Commission of China. 相似文献
30.