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251.
利用相空间分析方法,系统研究了具有双重指数势的phantom动力学.主要目的在于研究由M理论引起的势,但同时还分析了指数势中系数比为正的所有可能情况.根据宇宙的晚期行为,给出了解的完整分类.与quintessence情形相反,该体系存在异宿轨线解. 相似文献
252.
大椭圆轨道SAR滑动聚束模式设计及斜距模型 总被引:1,自引:0,他引:1
针对大椭圆轨道合成孔径雷达存在大偏心率,时变轨道高度及时变卫星速度等特性,首次开展了大椭圆轨道SAR滑动模式设计研究.对大椭圆轨道SAR滑动聚束模式设计,考虑了不同轨道位置处不同分辨率改善因子、地面波束足迹一致性、天线扫描角度、天线扫描角速度等.对大椭圆轨道SAR滑动聚束模式回波斜距模型研究.仿真分析结果表明大椭圆轨道SAR滑动聚束模式参数需要随轨道位置变化进行调整,为了满足成像需求斜距模型需要展开到三阶. 相似文献
253.
254.
王黑龙 Vanessa J. Murray 钱敏 Donna J. Minton 董爱义 刘建德 武博涵 车丽 Timothy K. Minton 《化学物理学报》2019,32(5):543-552
本文采用激光爆破法高能原子氧束源研究了纳米粘土增强环氧树脂复合材料的抗原子氧性能. 研究了四种样品:纯环氧树脂,纳米粘土含量为1 wt%,2 wt%和4 wt%的纳米粘土增强环氧树脂复合材料,结果表明腐蚀深度随着纳米粘土含量的增加而降低,当掺杂纳米粘土含量为4 wt%时,腐蚀深度为纯环氧树脂腐蚀深度的28%∽37%;X射线光电子能谱(XPS)分析表明原子氧轰击后,材料表面C-C/C-H键比例减少,C-O键、酮类比例增加,表面氧化程度增加,掺杂纳米粘土的材料表面生成了新的碳酸盐,掺杂4 wt%纳米粘土的复合材料表面氧化程度增加最小;扫描电子显微镜(SEM)结果显示含有纳米粘土的复合材料表面被原子氧轰击后在纳米粘土团簇处形成了“块状”物质,掺杂4 wt%纳米粘土的复合材料,“块状”物质尺寸和分布密度最大;综合腐蚀深度,XPS,以及SEM结果表明,虽然所有表面都一定程度地被原子氧腐蚀和氧化,但掺杂纳米粘土的复合材料表面由于生成了“块状”物质,阻挡了原子氧进一步腐蚀其下的材料,提高了抗原子氧性能. 相似文献
255.
Z. Oztas 《Physics letters. A》2019,383(6):504-508
We numerically investigate the localization of Bose Einstein condensate (BEC) with spin orbit coupling in a two dimensional bichromatic optical lattice. We study localization in weakly interacting and non-interacting regimes. The existence of stationary localized states in the presence of spin–orbit and Rabi couplings has been confirmed. We find that spin orbit coupling favors localization, whereas Rabi coupling has a slight delocalization effect. 相似文献
256.
257.
针对3D Lorenz型系统,提出了具有唯一平衡点或两个平衡点的四维超混沌系统,在两种不同平衡点情形下可分别发现超混沌吸引子。通过构造恰当的Lyapunov函数严格证明同宿轨与异宿轨的不存在性,表明此系统的超混沌是非Shil'nikov意义下的混沌;进一步将Lyapunov函数和优化方法有机结合证明超混沌吸引子的最终有界性,并数值模拟验证超混沌吸引子的最终有界;运用相图、Lyapunov指数谱、分岔图和Poincaré映射分析系统随参数变化的复杂动力学。 相似文献
258.
Based on first principle calculation when Ceperley–Alder and Perdew–Burke–Ernzerh type exchange-correlation energy functional were adopted to LSDA and GGA calculation, electronic properties of organometallic honeycomb lattice as a two-dimensional topological insulator was calculated. In the presence of spin–orbit interaction bulk band gap of organometallic lattice with heavy metals such as Au, Hg, Pt and Tl atoms were investigated. Our results show that the organometallic topological insulator which is made of Mercury atom shows the wide bulk band gap of about ∼120 meV. Moreover, by fitting the conduction and valence bands to the band-structure which are produced by Density Functional Theory, spin–orbit interaction parameters were extracted. Based on calculated parameters, gapless edge states within bulk insulating gap are indeed found for finite width strip of two-dimensional organometallic topological insulators. 相似文献
259.
J.J.P. Veerman D. Daescu M.J. Romero-Valls P.J. Torres 《Physica D: Nonlinear Phenomena》2009,238(18):1897-1908
We describe the global behavior of the dynamics of a particle bouncing down an inclined staircase. For small inclinations all orbits eventually stop (independent of the initial condition). For large enough inclinations all orbits end up accelerating indefinitely (also independent of the initial conditions). There is an interval of inclinations of positive length between these two. In that interval the behavior of an orbit depends on its initial condition. In addition to stopping and accelerating orbits, there are also orbits with speeds bounded away from both zero and infinity. A second hallmark of the dynamics is that the orbits going at a finite (but non-zero) average speed tend to have close to constant speed. In the setting of this model these phenomena are robust in the sense that they are independent of the ‘ruggedness’ of the staircase and of the coefficients of restitution that govern the energy loss at each bounce.The behavior just described matches up well with physical observations of single particles falling down a rough slope as well as measurements in laboratory controlled avalanches. This (and the robustness of the results) suggests that many-particle systems (avalanches) behave in similar ways as our low-dimensional model. 相似文献
260.
Wheel-off-loadings and orbital maneuvers of the GEO satellite result in additional accelerations to the satellite itself.
Complex and difficult to model, these time varying accelerations are an important error source of precise orbit determination
(POD). In most POD practices, only non-maneuver orbital arcs are treated. However, for some applications such as satellite
navigation RDSS services, uninterrupted orbital ephemeris is demanded, requiring the development of POD strategies to be processed
both during and after an orbital maneuver. We in this paper study the POD for a maneuvered GEO satellite, using high precision
and high sampling rate ranging data obtained with Chinese Area Positioning System (CAPS). The strategy of long arc POD including
maneuver arcs is studied by using telemetry data to model the maneuver thrust process. Combining the thrust and other orbital
perturbations, a long arc of 6 days’ CAPS ranging data is analyzed. If the telemetry data are not available or contain significant
errors, attempts are made to estimate thrusting parameters using CAPS ranging data in the POD as an alternative to properly
account for the maneuver. Two strategies achieve reasonably good data fitting level in the tested arc with the maximal position
difference being about 20 m.
Supported by the National Natural Science Foundation of China (Grant No. 10703011) and the Science & Technology Commission
of Shanghai Municipality of China (Grant No. 06DZ22101) 相似文献