全文获取类型
收费全文 | 406205篇 |
免费 | 19901篇 |
国内免费 | 10586篇 |
专业分类
化学 | 214291篇 |
晶体学 | 6055篇 |
力学 | 21974篇 |
综合类 | 546篇 |
数学 | 55899篇 |
物理学 | 137927篇 |
出版年
2022年 | 3431篇 |
2021年 | 5040篇 |
2020年 | 5906篇 |
2019年 | 5990篇 |
2018年 | 14190篇 |
2017年 | 14826篇 |
2016年 | 12524篇 |
2015年 | 7825篇 |
2014年 | 9609篇 |
2013年 | 17117篇 |
2012年 | 20211篇 |
2011年 | 30181篇 |
2010年 | 19392篇 |
2009年 | 19211篇 |
2008年 | 24214篇 |
2007年 | 27051篇 |
2006年 | 12811篇 |
2005年 | 17612篇 |
2004年 | 12536篇 |
2003年 | 11287篇 |
2002年 | 8878篇 |
2001年 | 8745篇 |
2000年 | 7043篇 |
1999年 | 5907篇 |
1998年 | 4829篇 |
1997年 | 4631篇 |
1996年 | 4788篇 |
1995年 | 4175篇 |
1994年 | 4012篇 |
1993年 | 3519篇 |
1992年 | 4068篇 |
1991年 | 3890篇 |
1990年 | 3636篇 |
1989年 | 3407篇 |
1988年 | 3323篇 |
1987年 | 3235篇 |
1986年 | 3093篇 |
1985年 | 3769篇 |
1984年 | 3697篇 |
1983年 | 2874篇 |
1982年 | 2949篇 |
1981年 | 2910篇 |
1980年 | 2648篇 |
1979年 | 2979篇 |
1978年 | 2982篇 |
1977年 | 3013篇 |
1976年 | 2904篇 |
1975年 | 2632篇 |
1974年 | 2580篇 |
1973年 | 2569篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
991.
The ferromagnetic shape memory alloy with nominal composition Ni54Fe19Ga27 is investigated by Ac susceptibility and resistivity measurements. The alloy shows long-range ferromagnetic order below 290 K. The anomaly due to the martensitic transition is observed in the susceptibility and resistivity data in the temperature range around 220 K, which is associated with clear thermal hysteresis. Minor hysteresis loop technique was used to investigate the phase coexistence across the martensitic transition, and our analysis indicate that both martensite and austenite phases mutually coexist in the region of hysteresis. 相似文献
992.
993.
K. S. Birdi 《Colloid and polymer science》1997,275(6):561-566
The surface tension versus temperature data of homologous series of n-alkanes and n-alkenes is analyzed. Critical temperatures are shown to be predicted from these data, with a very high precision, after some
corrections are made. The corrections are shown to arise from the effect of the critical pressure on the extrapolated data
to surface tension approaching zero.
Received: 29 October 1996 Accepted: 13 December 1996 相似文献
994.
The acoustoelectromagnetic interaction is examined in a regime where three mechanisms must be taken into account simultaneously:
photoelasticity, quadratic photoelasticity, and elastic nonlinearity. It is shown that beyond the critical conditions, acoustic
solitary waves are formed at harmonic and subharmonic frequencies in a crystal. Including damping and nonideal reflection
at the boundaries does not lead to the establishment of any sort of stationary state: a soliton spatial-temporal dynamic develops.
Fiz. Tverd. Tela (St. Petersburg) 39, 1101–1104 (June 1997) 相似文献
995.
In a previous study, a mathematical model relating surface and bulk behaviours of metals in aqueous solution has been developed. The model was established based on principles of holographic interferometry for measuring microsurface dissolution, i.e. mass loss, and on those of electrochemistry for measuring the bulk electronic current, i.e. corrosion current. In the present work, an optical corrosion meter was built based on the above model. The corrosion meter consists of an electrochemical cell in which the sample is immersed in aqueous solution. Furthermore, the corrosion meter has a holographic camera with a thermoplastic film for in situ processing of holograms in order to obtain real-time holographic interferoms of the sample in the electrochemical cell. Results of the present work indicate that optical holography is a very useful technique for measuring the corrosion current density of different alloys in aqueous solutions. As a result, the corrosion current density of aluminium, stainless steel, and low-carbon steel in 1 M KCl, 1 M NaCl, and 1 M NaOH solutions were obtained. A comparison between the corrosion data of samples showed that the corrosion current density of the stainless steel in 1 M NaCl is nearly three-folds higher than that of the aluminium in 1 M KCl and the low-carbon steel in 1 M NaOH. 相似文献
996.
Auluck S.K.H. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(1):37-41
The validity of the snowplow model of plasma sheath propagation in a plasma focus (PF) and the localization of the magnetic field in the low density region behind the dense plasma sheath are two well-established experimental facts. It is shown that, when taken together, these two imply a deficiency in the momentum balance. The hypothesis that the current-carrying plasma layer is rotating while the dense plasma layer is not rotating is shown not only to resolve this momentum balance anomaly (MBA), but also to explain many observed phenomena in a unified manner 相似文献
997.
Gopalakrishna K. Bhat 《Optics and Lasers in Engineering》1997,26(1):43-58
An electro-optic holographic technique (also called electronic speckle pattern interferometry or TV holography) for the measurement of displacements and strains on three-dimensional object surfaces is presented. The three components of the displacement vector, in a fixed coordinate system, are separated using four independent illumination beams. The interferometric phase for each illumination beam is extracted using the phase stepping technique. Displacements in the fixed coordinate system are projected on to the object surface using the tensor transformation law. Equations for the computation of surface strains using the projected displacements and the surface geometry are developed. The technique is applied for the measurement of strains on the surface of a cylindrical vessel subjected to internal pressure. 相似文献
998.
An all-optical fiber nonlinear Fabry-Perot resonator is proposed. The steady-state model for describing this resonator is developed. The transmission and refection bistabilities are shown numerically. Our results show that the bistability in this system is similar to that in a normal nonlinear Fabry-Perot etalon, except that the characteristics of the bistability can be changed not only by the cavity length but also by the phase shifts of the fiber loop mirrors. 相似文献
999.
T. K. Solovykh 《Journal of Applied Spectroscopy》1997,64(5):654-657
The role of impurity ions in formation of the optical properties of rare-earth orthoferrites is investigated. Optical spectra
of the substituted against unsubstituted orthoferrites are presented. The influence of different isovalent substitutions on
the optical absorption of orthoferrites that are promising for magnetooptics is studied.
Institute of Solid-State and Semiconductor Physics of the Academy of Sciences of Belarus, 17, P. Brovka St., Minsk, 220072,
Belarus. Translated from zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 5, pp. 642–645, September–October, 1997. 相似文献
1000.
Matrix extensions and eigenvalue completions, the generic case 总被引:2,自引:0,他引:2
William Helton Joachim Rosenthal Xiaochang Wang 《Transactions of the American Mathematical Society》1997,349(8):3401-3408
In this paper we provide new necessary and sufficient conditions for the so-called eigenvalue completion problem.