全文获取类型
收费全文 | 109818篇 |
免费 | 19527篇 |
国内免费 | 10589篇 |
专业分类
化学 | 90320篇 |
晶体学 | 1268篇 |
力学 | 5040篇 |
综合类 | 688篇 |
数学 | 11235篇 |
物理学 | 31383篇 |
出版年
2024年 | 244篇 |
2023年 | 1499篇 |
2022年 | 2813篇 |
2021年 | 3139篇 |
2020年 | 4067篇 |
2019年 | 5157篇 |
2018年 | 3441篇 |
2017年 | 3092篇 |
2016年 | 6643篇 |
2015年 | 6894篇 |
2014年 | 7588篇 |
2013年 | 9383篇 |
2012年 | 9477篇 |
2011年 | 8838篇 |
2010年 | 7487篇 |
2009年 | 7216篇 |
2008年 | 7194篇 |
2007年 | 6125篇 |
2006年 | 5482篇 |
2005年 | 5033篇 |
2004年 | 4034篇 |
2003年 | 3444篇 |
2002年 | 4129篇 |
2001年 | 3089篇 |
2000年 | 2720篇 |
1999年 | 1898篇 |
1998年 | 1316篇 |
1997年 | 1174篇 |
1996年 | 1150篇 |
1995年 | 997篇 |
1994年 | 866篇 |
1993年 | 731篇 |
1992年 | 618篇 |
1991年 | 560篇 |
1990年 | 451篇 |
1989年 | 363篇 |
1988年 | 274篇 |
1987年 | 223篇 |
1986年 | 206篇 |
1985年 | 197篇 |
1984年 | 137篇 |
1983年 | 118篇 |
1982年 | 77篇 |
1981年 | 54篇 |
1980年 | 48篇 |
1979年 | 25篇 |
1978年 | 25篇 |
1977年 | 23篇 |
1976年 | 26篇 |
1975年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
902.
Wave properties of an annular periodic multilayer structure containing the single-negative materials
The optical properties of an annular periodic multilayer structure containing two kinds of single-negative materials are theoretically investigated based on the transfer matrix method of the cylindrical waves. At the azimuthal mode number m1 and near the magnetic plasma frequency and the electronic plasma frequency for the TE wave and TM wave, respectively, we find that there is an additional high-reflectance band and some reflection dips exist when the plasma frequency is located in the photonic band gap. These two special features arising from the higher order azimuthal mode of the cylindrical waves are not seen in the planar one-dimensional Bragg reflector consisting of the single-negative materials. Such filtering responses provide a feasible way of designing a narrowband resonator without physically introducing any defect layer in the structure. 相似文献
903.
904.
The robustness of the software-synchronized all-optical sampling for optical performance monitoring is estimated for 10-Gb/s fiber communication systems. It reveals that the software-synchronized algorithm is sensitive to the signal degradation caused by chromatic dispersion and nonlinearity in optical fibers. The influence of timing jitter and amplitude fluctuation of the sampling pulses is also investigated. It is found that stringent requirements are imposed on the quality of the sampling pulse and the tolerance of 1-dB Q penalty is measured. Considering the practically available optical sampling pulse sources, the results indicate that the amplitude fluctuation of the sampling pulses has the dominant impacts on the software-synchronized method. 相似文献
905.
在采用商用的STEMET-1101非晶钎料、温度为710~750°C的真空钎焊下,对CFC/OFC(氯氟烃/无氧铜)复合块与CuCrZr(铬锆铜)的钎焊进行了研究。首先,通过X-射线衍射(XRD)和差式扫描量热分析对钎料的结构和熔化行为进行了表征;然后,通过光学显微镜、电子探针微分析和拉伸试验等方法对焊缝的组织形貌、元素成分分布、相结构和力学性能进行了分析;最后,通过高热负荷装置对CFC/OFC/CuCrZr钎焊模块的热疲劳性能进行测试。结果表明,在710~750°C钎焊温度内焊缝由Cu固溶体、(Cu, Ni)3P和Ni(Cu ,Cr)2P金属间化合物组成,焊缝平整无裂纹;特别是在750°C/15min情况下,抑制了焊缝金属间化合物的连续分布,OFC/CuCrZr的焊接强度大于OFC的抗拉强度,CuCrZr/CuCrZr的结合强度为210MPa,并呈现部分韧性断裂。在750°C/15min情况下制备的CFC/Cu/CuCrZr模块可以承受1000次7MW·m-2的循环热负荷。 相似文献
906.
The buckled structure of silicene provides a feasible pathway to influence its electric and magnetic properties via surface adsorptions. Here, we investigate the magnetic and spin thermoelectric transport properties of dual-hydrogenated zigzag silicene nanoribbons (ZSiNRs) without/with the hydrogen adsorption. The band gaps for two spin channels in ZSiNRs under the hydrogen adsorption are shifted near the Fermi level, leading to the appearance of spin Seebeck effect. Using a temperature difference, one can derive the carriers with the different spin index to flow in the opposite direction. Moreover, a large rectification ratio close to 105 at room temperature is achieved for the spin current, and the charge current exhibits a remarkable negative differential thermoelectric resistance (NDTR) behavior. The results presented here are fascinating potential applications in the fields of silicon-based spin caloritronic devices. 相似文献
907.
An experimentally feasible strong coupling system between a spin ensemble and a superconducting qubit is studied. The coupling strength can be exponentially enhanced by applying the squeezing transformations to the system. By means of the two spin ensembles commonly coupled to a superconducting qubit, a set of universal nonadiabatic holonomic single‐qubit quantum gates can be realized in a decoherence‐free subspace. Furthermore, this proposal is robust with respect to decay of the system parameters, and it is experimentally feasible with currently available technology. 相似文献
908.
909.
Rafal Nowaczynski Marcin Gajc Hancza B. Surma Pawel Osewski Adam Strzep Witold Ryba‐Romanowski Dorota A. Pawlak 《Particle & Particle Systems Characterization》2019,36(1)
Quantum dot (QD)‐based light‐emitting materials are gaining increased attention because of their easily tunable optical properties desired for various applications in biology, optoelectronics, and photonics. However, few methods can be used to manufacture volumetric materials doped with more than one type of QD other than QD‐polymer hybrids, and they often require complicated preparation processes and are prone to luminescence quenching by QD aggregation and separation from the matrix. Here, simultaneous doping of a volumetric glass‐based nanocomposite with two types of QDs is demonstrated for the first time in a single‐step process using the nanoparticle direct doping method. Glass rods doped with CdTe, CdSe/ZnS, or co‐doped with both QDs, are obtained. Photoluminescence and lifetime experiments confirm temperature‐dependent double emission with maxima at 596 and 720 nm with mean lifetimes up to 16 ns, as well as radiative energy transfer from the short wavelength–emitting QDs to the long wavelength–emitting QDs. This approach may enable the simple and cost‐efficient manufacturing of bulk materials that produce multicolor luminescence with cascade excitation pumping. Applications that could benefit from this include broadband optical fiber amplifiers, backlight systems in LCD screens, high‐power LEDs, or down‐converting solar concentrators used to increase the efficiency of solar panels. 相似文献
910.
Aaron McCulloch Lindsey Bennie Jonathan A. Coulter Helen O. McCarthy Brendan Dromey David R. Grimes Paul Quinn Balder Villagomez‐Bernabe Frederick Currell 《Particle & Particle Systems Characterization》2019,36(9)
Studies into the cell nucleus' incorporation of gold nanoparticles (AuNPs) are often limited by ambiguities arising from conventional imaging techniques. Indeed, it is suggested that to date there is no unambiguous imaging evidence for such uptake in whole cells, particularly at the single nanoparticle level. This shortcoming in understanding exists despite the nucleus being the most important subcellular compartment in eukaryotes and gold being the most commonly used metal nanoparticle in medical applications. Here, dual‐angle X‐ray flouresence is used to show individually resolved nanoparticles within the cell nucleus, finding them to be well separated and 79% of the intranuclear population to be monodispersed. These findings have important implications for nanomedicine, illustrated here through a specific exemplar of the predicted enhancement of radiation effects arising from the observed AuNPs, finding intranuclear dose enhancements spanning nearly five orders of magnitude. 相似文献