全文获取类型
收费全文 | 4537篇 |
免费 | 721篇 |
国内免费 | 416篇 |
专业分类
化学 | 3182篇 |
晶体学 | 43篇 |
力学 | 271篇 |
综合类 | 46篇 |
数学 | 428篇 |
物理学 | 1704篇 |
出版年
2024年 | 14篇 |
2023年 | 125篇 |
2022年 | 171篇 |
2021年 | 189篇 |
2020年 | 213篇 |
2019年 | 166篇 |
2018年 | 145篇 |
2017年 | 128篇 |
2016年 | 207篇 |
2015年 | 182篇 |
2014年 | 253篇 |
2013年 | 281篇 |
2012年 | 396篇 |
2011年 | 361篇 |
2010年 | 270篇 |
2009年 | 267篇 |
2008年 | 287篇 |
2007年 | 273篇 |
2006年 | 274篇 |
2005年 | 183篇 |
2004年 | 130篇 |
2003年 | 111篇 |
2002年 | 100篇 |
2001年 | 86篇 |
2000年 | 86篇 |
1999年 | 99篇 |
1998年 | 90篇 |
1997年 | 89篇 |
1996年 | 65篇 |
1995年 | 90篇 |
1994年 | 75篇 |
1993年 | 44篇 |
1992年 | 58篇 |
1991年 | 45篇 |
1990年 | 40篇 |
1989年 | 26篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有5674条查询结果,搜索用时 15 毫秒
51.
Liu-Ying Nie Lingling Wang Ke-Qiu Chen B.S. Zou L.H. Zhao 《Physica E: Low-dimensional Systems and Nanostructures》2007,39(2):185-190
Based on the scattering-matrix method, the influence of obstacles on the thermal conductance in quantum wire was investigated. Three types of obstacles are employed in our calculation. We present a detailed study of the thermal conductance as a function of distance between two obstacles and temperature. The results show that there is qualitative difference in the dependence of the thermal conductance versus width between two obstacles for different temperatures. We also find that the calculated thermal conductance increases with the width W of quantum wire in all cases. 相似文献
52.
Path protections have become increasingly important for current mesh optical networks because fast restorations in generalized multiprotocol label switching(GMPLS) networks are uncertain.However,setting up additional disjoint paths to protect connections leads to more path setup blocking and signaling collisions.We analyze signaling collisions,path blocking and blocking probability,as well as calculate node-to-node blocking probabilities.A signaling-based path-segment protection(PSP) is proposed,which integrates segment protections and path protections as well as enhances the performance of path protections and ring protections.The setup of PSP connections causes less blocking probability than the setup of path protection connections in the simulations. 相似文献
53.
54.
以丝阵内爆零维模型为基础,采用Pspice模拟行为建模方法,建立了丝阵内爆动态电感与Z箍缩驱动器耦合的全电路模型,实现驱动器放电过程与丝阵内爆过程的自洽求解,并研究了丝阵参数、电路参数对内爆过程的影响.结果表明:丝阵负载与驱动器存在强耦合关系,丝阵参数、电路参数对丝阵峰值箍缩电流、内爆时间、内爆动能影响很大;在驱动器参数不变,内爆时间不超过电路固有放电周期1/4的前提下,峰值箍缩电流、内爆时间、内爆动能随丝阵质量的增加而增大,内爆时间随丝阵初始半径的增加而增大;在丝阵参数不变时,随着驱动器等效电容的增大,内爆时间减小,丝阵内爆动能增大,但驱动器储能转化为内爆动能的效率却先增大后减小.对于特定的驱动器,优化的丝阵参数应使内爆过程充分利用驱动器固有放电周期的上升沿,使丝阵快速收缩的时间起点接近电路固有放电周期的四分之一,以获得最大的动能效率.
关键词:
Z箍缩驱动器
零维内爆模型
模拟行为建模
耦合特性 相似文献
55.
Xin Chen Jun Tao Gang Zou Qijin Zhang Pei Wang 《Applied Physics A: Materials Science & Processing》2010,100(1):223-230
Diacetylene monomer containing p-nitrophenyl azobenzene moiety (NADA) was synthesized. Silver nanoparticles with different
concentrations were adulterated in the above polymerized NADA (PNADA) films and the third-order nonlinear optical properties
were investigated in detail. UV–vis spectra and transmission electron microscopy were used to confirm the formation of PNADA/Ag
nanocomposite films. The silver nanoparticles (average size of 10 nm) were well dispersed in the polymer films. The value
of the nonlinear refractive index n
2 for PNADA films (8.48×10−15 cm2/W) was much higher than that of pure polydiacetylene films. Further, the introduction of silver nanoparticles into the PNADA
polymer films led to the further enhancement of nonlinear optical properties. The maximum value of n
2 for PNADA/Ag nanocomposite films could be 11.6×10−15 cm2/W. This enhancement should be ascribed to the surface plasmon resonance of silver nanoparticles. 相似文献
56.
研究了退火温度对ZrO2纳米材料中Eu3+离子发光性质的影响. 材料的结构、晶粒尺寸和形状以及晶格的排列分别由XRD,TEM表征. 结果表明:用共沉淀法制备的ZrO2纳米材料具有不随退火温度变化、稳定的四方结构;材料的晶粒尺寸随退火温度的提高而增大;晶格的排列由无序逐渐变为有序;发射光谱表明其主要发射在595 nm和604 nm处;在394 nm的紫外光辐照下得到了不同样品的604 nm荧光发射强度的变化不同. 这种现象与样品中O2-离子含量和样品表面的表面缺陷有关;另外,电荷迁移带随退火温度的变化而变化. 相似文献
57.
Load optimal design for a primary test stand facility based on a zero-dimensional load model 下载免费PDF全文
In order to couple the numerical simulation of a primary test stand driver with an optimal load design, a zero-dimensional wire array load model is designed based on the Saturn load model using PSPICE, which is an upgraded version of the Simulation Program with Integrated Circuit Emphasis (SPICE) designed by the ORCAD Corporation to perform circuit simulations. This paper calculates different load parameters and discusses factors influencing the driving current curve. With appropriate driving current curves chosen, further magneto-hydrodynamic calculations are carried out and discussed to provide the best results for experiments. The suggested optimal load parameters play an important role in experimental load design. 相似文献
58.
59.
Using an approach proposed in [3],we consider some linear and nonlinear problems forviscoelastic rods.Results in [1]for linear case are affirmed more elamentarily and simplyhere.We also treat linear problem with damping term and nonlinear problem with powernonlinearity Pu~3. Some new results are established. 相似文献
60.