全文获取类型
收费全文 | 13579篇 |
免费 | 2249篇 |
国内免费 | 1439篇 |
专业分类
化学 | 5833篇 |
晶体学 | 108篇 |
力学 | 1051篇 |
综合类 | 110篇 |
数学 | 2615篇 |
物理学 | 7550篇 |
出版年
2024年 | 33篇 |
2023年 | 173篇 |
2022年 | 436篇 |
2021年 | 411篇 |
2020年 | 496篇 |
2019年 | 474篇 |
2018年 | 446篇 |
2017年 | 472篇 |
2016年 | 588篇 |
2015年 | 503篇 |
2014年 | 772篇 |
2013年 | 1176篇 |
2012年 | 819篇 |
2011年 | 898篇 |
2010年 | 691篇 |
2009年 | 825篇 |
2008年 | 860篇 |
2007年 | 904篇 |
2006年 | 789篇 |
2005年 | 654篇 |
2004年 | 590篇 |
2003年 | 515篇 |
2002年 | 535篇 |
2001年 | 426篇 |
2000年 | 380篇 |
1999年 | 318篇 |
1998年 | 302篇 |
1997年 | 240篇 |
1996年 | 213篇 |
1995年 | 192篇 |
1994年 | 155篇 |
1993年 | 154篇 |
1992年 | 119篇 |
1991年 | 95篇 |
1990年 | 85篇 |
1989年 | 83篇 |
1988年 | 64篇 |
1987年 | 39篇 |
1986年 | 43篇 |
1985年 | 49篇 |
1984年 | 45篇 |
1983年 | 24篇 |
1982年 | 39篇 |
1981年 | 26篇 |
1980年 | 24篇 |
1979年 | 25篇 |
1978年 | 18篇 |
1977年 | 9篇 |
1976年 | 14篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Frank H.G.M. Wijnands Charles G. Crookes Paul M. Charles Richard M. Ash Ian F. Lealman Michael J. Robertson Anthony E. Kelly Kevin A. Williams Aeneas B. Massara Richard V. Penty Ian H. White 《Optical and Quantum Electronics》2002,34(10):959-973
An anomalous modulation in the wavelength spectrum has been observed in lasers with spot-size converters. This intensity modulation is shown to be caused by beating between the fundamental lasing mode and radiation modes in the taper. This results in a periodic modulation in the net gain spectrum, which causes wavelength jumps between adjacent net gain maxima, and a drive current dependent spectral width that is expected to affect system performance. The amplitude of this spectral modulation is reduced significantly by either using an angled rear-facet which reflects the beating radiation modes away from the laser axis, or by using a nonlinear, adiabatic taper. 相似文献
62.
P. Paasche T. Valenzuela D. Biswas C. Angelescu G. Werth 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):295-300
We have examined experimentally the motional spectrum of an electron cloud confined in a Penning trap. When the axial oscillation
is excited by a radio frequency field the resonance exhibits a double structure. Both components depend differently on the
number of trapped electrons and have different shape and width. We conclude that one of them corresponds to the excitation
of the individual electrons while the other is the center-of-mass mode of the cloud. The threshold behaviour of the center-of-mass
resonance suggests that it is a parametric instability of a Mathieu type equation of motion.
Received 11 July 2001 and Received in final form 12 November 2001 相似文献
63.
64.
Tatsuo Nakagawa Satoshi Fukura Munenori Nakai Kazumasa Sugiyama Ryohei Kokawa Hiroyuki Kagi 《Optical Review》2006,13(4):269-275
We constructed a scanning near-field optical microscope (SNOM) on a commercially available atomic force microscopy (AFM) apparatus
(SPM-9500J2; Shimadzu Corp.) to measure the stress distribution in ceramic composite materials. Features of our SNOM system
are: (1) a compact SNOM head substituted for the original AFM head; (2) a wide scanning range (125 × 125 μm2) inherited from the original scanner; (3) use of conventional shear-force regulation; (4) an optical system for the illumination-collection
(I-C) mode; (5) excitation by a 488 nm line of an Ar-ion laser, and (6) light detection by photon counting or a polychromator
equipped with an electronically cooled charge coupled device (CCD). This SNOM system was used to measure the surface structure
and stress distribution of an Al2O3/ZrO2 eutectic composite. We simultaneously measured topographic images and fluorescence spectra of an Al2O3/ZrO2 eutectic composite. We estimated its peak intensity, peak position, and peak width from the fluorescence spectrum during
scanning, which respectively correspond to the abundance of Al2O3, stress in the grain, and the anisotropy of that stress. Mapping images showed that the stress and its anisotropy were weaker
in the center of the Al2O3 grain than its boundary between Al2O3 and ZrO2. That observation suggests that Al2O3 underwent intense anisotropic stress induced by volume expansion in the phase transition of ZrO2 from the cubic phase to the monoclinic phase during preparation. 相似文献
65.
Ferhat Sametoglu 《Optical Review》2006,13(5):326-337
Traceability in illuminance measurements at the National Metrology Institute of Turkey (TüBITAK-UME) was established in 2003
with a detector-based realization. The new measurement technique was developed for the determination of illuminance responsivity
and upgrating of the illuminance scale. The unit of the illuminance responsivity, in A/lx, was measured with an expanded uncertainty
of 0.2% (k = 2) by supplying using the developed scanning technique for the calculation of color correction factor. The surface of a
radiometer was scanned using a double-monochromator facility upgraded with an x-y scanning system. The illuminance responsivity
as a function of bandpass and temperature were also investigated in this study.
To use a radiometer in the photometric applications of metrology, a light-sensitive device, a so-called trap detector, was
characterized by measuring the absolute responsivity, the non-linearity, and spatial non-uniformity. 相似文献
66.
3d-metal antimonides: Fe1+x Sb, N+x Sb, Co+x Sb and the (Ni1?y Fe y )Sb solid solution have been studied by the Mössbauer effect method at 57Fe and 119Sn. It was found that the quadrupole interactions at the Fe and Sn nucleus in 3d-metal antimonides are very sensitive to the filling of different crystallographic sites with metal atoms. The metal atoms in trigonal-bipyramidal sites have a strong effect on the quadrupole splitting of 119Sn. They are nearest to anions (Sb or Sn) with the typical axial ratio of c/a = 1.25. The QS(x) dependence of 119 Sn in 3d-metal antimonides in the 0 ≤ x ≤ 0.1 concentration range can be used to determine x – the concentration of transition metal excess relative to the stoichiometric composition. 相似文献
67.
68.
Mark E. Filipkowski Edwin E. Hach III Michael Offenbacker 《Journal of magnetism and magnetic materials》2006
We show, via a straightforward calculation, that it is feasible to detect nuclear spin echoes in a ferromagnetic thin film by electrical means. The detection scheme is based on the deflection of the electronic magnetization when the nuclear magnetization reforms during an echo. This deflection is observed as a time-dependent magnetoresistive signal. 相似文献
69.
Yu. D. Perfiliev V. S. Rusakov L. A. Kulikov A. A. Kamnev K. Alkhatib 《Hyperfine Interactions》2006,167(1-3):881-885
To explain line broadening in emission Mössbauer spectra as compared to the corresponding absorber measurements, the model of trapped electrons has been proposed. Auger electrons (emitted, e.g. after electron capture by 57Co or after the converted isomeric transition of 119mSn), as well as secondary electrons, may be trapped in the proximity to the nucleogenic ion. Electrons captured by lattice traps at different distances from the daughter ion induce an asymmetric distribution of quadrupole splitting in the resulting emission spectra, as shown in a few examples. This model is supported by estimates of quadrupole splitting values which may be caused by such trapped electrons located at specified distances from the nucleogenic atom. 相似文献
70.
用硼氢化钠作还原剂,制备出两种相对稳定的含银纳米颗粒的水溶胶,用透射电镜(TEM)和光学吸收谱对这些颗粒进行了表征.当被还原的银离子较少时,所形成的银纳米颗粒较小,吸收峰呈现二极等离子体共振吸收峰.当被还原的银离子较多时,银纳米颗粒尺寸变大,并出现二极和四极共振吸收峰.在Ag纳米颗粒形成后,对其溶液稀释,发现其峰形保持不变,而峰位会出现红移,最大红移量可达到10 nm.透射电镜研究表明,低浓度溶胶中的Ag纳米颗粒尺寸较为均匀,平均直径12 nm.高浓度溶胶中的纳米颗粒尺寸呈双尺寸分布特点,少量颗粒直径小于14 nm,大部分颗粒直径大于20 nm. 相似文献