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81.
白光横向平顶光束在定向背光式自由立体显示器中有重要应用.本文提出一种采用带蝶形小孔阵列的衍射掩模片获得白光横向平顶光束的方法.根据广义惠更斯-菲涅耳衍射积分和多波长叠加原理,推导出光强分布计算式.设计一套实验装置,数值模拟并实验验证出射光束在不同距离的横向光强分布以及小孔蝶形凹度(蝶形中心高度与边长的比值)对横向光强分布的影响.结果表明:当选择小孔蝶形凹度为0.50—0.66时,可以得到平顶因子F 0.89的白光横向平顶光束,横向平顶光束的宽度随着传输距离的增大而增大,而平顶因子基本不变.实验还发现柱面透镜的折射色散和衍射色散可以互相抵消,使白光横向平顶光束基本无色散. 相似文献
82.
To extend the optical property characterization of metal–Cu2O polyhedra, 50 nm Au@Cu cubic cores are used to fabricate Au@Cu–Cu2O core–shell cubes, octahedra, and rhombic dodecahedra with tunable sizes. Despite the unusually large lattice mismatch of 15.1% between Cu and Cu2O, fine adjustment in the volumes of reagents introduced allows the formation of these heterostructures. To relieve the lattice strain, the metal cores are essentially never found to locate at the particle center, and slight lattice spacing shifts are recorded. Although efforts are made to reduce the heterostructure sizes, the Cu2O shells are generally too thick to reveal surface plasmon resonance (SPR) absorption band from the metal cores. Only the Au@Cu–Cu2O cubes with many cores located near the particle corners show observable SPR band red‐shift, but UV–vis spectra of all particle shapes are still dominated by Cu2O absorption and light scattering bands. Au@Cu–Cu2O cubes consistently show the most red‐shifted absorption bands than those of octahedra resulting from the optical facet effects. 相似文献
83.
从原子核的电四极跃迁强度B(E2)中可以提取出原子核集体性和单粒子性质竞争的重要信息,其中一个重要的观测量是B(E2;41+ →21+)/B(E2;21+ →g.s.)的比值(B4/2)。B4/2一般要大于1,而且对于原子核转动和振动,我们应有B4/2=1.4和2.0,但球形半满壳核一般会有不一样的性质。这些核的性质主要受对关联效应影响。介绍了几种超出我们一般认识的奇特衰变性质。Te同位素的基态带有鲜明的振动特性,但114Te的E2跃迁性质却更符合转动性。这些性质可以通过大规模壳模型计算来描述。对于填充j=9/2轨道的半满壳核,它们的4+和6+显示出很强的辛若数部分守恒性质。这种奇特的部分守恒可以被解析证明。而且我们的计算表明辛若数部分守恒对相关的E2跃迁影响很大。对于N=90附近具有量子相变行为的核素,其B4/2也会也表现出相似的奇异特性。The E2 transition strength, B(E2), gives particularly precise information on the competition between the collective and single-particle degree of freedom. An important observable to study the development of collectivity is the B(E2; 41+ →21+)/B(E2; 21+ →g.s.) (B4/2). The B4/2 ratio is usually greater than unity. These values are 1.4 and 2.0 for an ideal rotor and a vibrator, respectively. Whereas the seniority scheme usually leads to different behaviours. In this contribution I will show examples that contrast with our standard understanding. The yrast spectra of Te isotopes show a vibrational-like equally-spaced pattern but the few known E2 transitions show anomalous rotational-like behaviour, which cannot be reproduced by collective models. Large-scale shell model calculations reproduce well the equally-spaced spectra of those isotopes as well as the constant behaviour of the B(E2) values in 114Te. For nuclei involving protons or neutrons in j=9/2 orbitals, the partial conservation of seniority can lead to dramatic changes to the E2 decay pattern that have never been seen before. The B4/2 ratios in quantum phase transitional nuclei around N=90 also show a similar exotic feature. 相似文献
84.
Yolk–Shell‐Structured Cu/Fe@γ‐Fe2O3 Nanoparticles Loaded Graphitic Porous Carbon for the Oxygen Reduction Reaction 下载免费PDF全文
Meiwen Wang Chao Su Martin Saunders Ji Liang Zongping Shao Shaobin Wang Jian Liu 《Particle & Particle Systems Characterization》2017,34(10)
Core–shell Cu/γ‐Fe2O3@C and yolk–shell‐structured Cu/Fe@γ‐Fe2O3@C particles are prepared by a facile synthesis method using copper oxide as template particles, resorcinol‐formaldehyde as the carbon precursor, and iron nitrate solution as the iron source via pyrolysis. With increasing carbonization temperature and time, solid γ‐Fe2O3 cores are formed and then transformed into Fe@γ‐Fe2O3 yolk–shell‐structured particles via Ostwald ripening under nitrogen gas flow. The composition variations are studied, and the formation mechanism is proposed for the generation of the hollow and yolk–shell‐structured metal and metal oxides. Moreover, highly graphitic carbons can be obtained by etching the metal and metal oxide nanoparticles through an acid treatment. The electrocatalytic activity for oxygen reduction reaction is investigated on Cu/γ‐Fe2O3@C, Cu/Fe@γ‐Fe2O3@C, and graphitic carbons, indicating comparable or even superior performance to other Fe‐based nanocatalysts. 相似文献
85.
In the level schemes of sd shell nuclei, there is generally at relatively low excitation energies, coexistence of normal 0 ?ω positive parity states and of intruder 1 ?ω negative parity states. The aim of the present work is to describe these intruder states in the full p-sd-pf model space with a 4He core allowing one nucleon jump between the major shells. To construct our PSDPF interaction, we first modified the p-sd and sd-pf cross-monopole terms and then applied a fitting procedure to adjust all PSDPF parameters by comparing an extended set of experimental and calculated excitation energies. Results obtained with the new interaction have been finally compared with experimental data for nuclei throughout the sd shell. 相似文献
86.
建立并求解了弹性介质中圆柱壳的径向位移控制方程,考虑边界条件及相容条件,得到了应力波传播及反射过程中圆柱壳的动力屈曲分叉条件.通过计算得到了不同时间段屈曲临界载荷与应力波波阵面到达圆柱壳的位置、弹性介质的刚度、壳体未嵌入弹性介质部分的长度与总长之比的关系.数值计算结果表明,弹性介质中的圆柱壳发生轴对称屈曲和非轴对称屈曲趋势一致;嵌入弹性介质部分越深、弹性介质刚度越大圆柱壳越难屈曲;屈曲临界载荷随着弹性介质刚度的增大经历了增长缓慢、增长迅速以及增长较慢3个阶段;应力波反射前波阵面通过分界面后,屈曲仅发生在应力波传播区域,反射波波阵面通过分界面前,临界载荷较小时屈曲先发生在反射端部,随着轴向阶数增大,屈曲覆盖整个圆柱壳区域,反射波波阵面通过分界面后,壳体发生的屈曲始终覆盖整个圆柱壳区域. 相似文献
87.
轴压加筋圆柱壳Koiter-边界层奇异摄动法 总被引:1,自引:0,他引:1
将Koiter理论和奇异摄动理论中的边界层法相结合,处理加筋圆柱壳无因次化非线性边界层型Karman-Donnell方程由分支点和边界层导致的双重奇异性,提出轴压加筋圆柱壳Koiter-边界层奇异摄动法.对AS-2壳分析表明,本方法具有很好的计算效率和计算精度,与数值解相比更能揭示其内在的影响规律. 相似文献
88.
89.
J Benlliure S Steinhäuser C Böckstiegel A Grewe H-G Clerc A heinz M de Jong A R Junghans J Müller K-H Schmidt M Pfützner 《Pramana》1999,53(3):637-646
Nuclear fission from excitation energies around 11 MeV was studied at GSI, Darmstadt for 76 neutron-deficient actinides and
pre-actinides by use of relativistic secondary beams. The characteristics of multimodal fission of nuclei around 226Th are systematically investigated and related to the influence of shell effects on the potential-energy and on the level
density between saddle point and scission. A systematic view on the large number of elemental yields measured gave rise to
a new interpretation of the enhanced production of even elements in nuclear fission and allowed for a new understanding of
pair breaking in fission. 相似文献
90.