全文获取类型
收费全文 | 368907篇 |
免费 | 2224篇 |
国内免费 | 1099篇 |
专业分类
化学 | 166514篇 |
晶体学 | 4974篇 |
力学 | 20171篇 |
综合类 | 6篇 |
数学 | 74126篇 |
物理学 | 106439篇 |
出版年
2020年 | 2042篇 |
2019年 | 2336篇 |
2018年 | 18921篇 |
2017年 | 19347篇 |
2016年 | 12702篇 |
2015年 | 3861篇 |
2014年 | 4310篇 |
2013年 | 10000篇 |
2012年 | 13805篇 |
2011年 | 27564篇 |
2010年 | 16793篇 |
2009年 | 17161篇 |
2008年 | 22749篇 |
2007年 | 27592篇 |
2006年 | 8362篇 |
2005年 | 14222篇 |
2004年 | 10717篇 |
2003年 | 10664篇 |
2002年 | 7941篇 |
2001年 | 6409篇 |
2000年 | 5337篇 |
1999年 | 3725篇 |
1998年 | 3324篇 |
1997年 | 3286篇 |
1996年 | 3260篇 |
1995年 | 2611篇 |
1994年 | 2647篇 |
1993年 | 2705篇 |
1992年 | 2796篇 |
1991年 | 2852篇 |
1990年 | 2753篇 |
1989年 | 2723篇 |
1988年 | 2669篇 |
1987年 | 2640篇 |
1986年 | 2544篇 |
1985年 | 3268篇 |
1984年 | 3448篇 |
1983年 | 2778篇 |
1982年 | 3056篇 |
1981年 | 2948篇 |
1980年 | 2757篇 |
1979年 | 2951篇 |
1978年 | 3084篇 |
1977年 | 2995篇 |
1976年 | 3008篇 |
1975年 | 2854篇 |
1974年 | 2823篇 |
1973年 | 3016篇 |
1972年 | 1975篇 |
1967年 | 1906篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
A. Puiu G. Giubileo G. Addolorato L. Revelli G. Gasbarrini R. Bellantone A. D’Amore C. P. Lombardi C. Carrozza 《Laser Physics》2007,17(4):448-452
Nowadays, there is high demand for sensitive gas sensors both for human and environmental monitoring. This paper deals with a high-resolution (0.2 ppb) laser-based photoacoustic spectroscopic system realized at ENEA Frascati, Italy, applied for monitoring stress in scuba divers during sustained immersion by analyzing breath samples. Blood tests and psychometric tests for scuba divers were performed at Catholic University in Rome. Results will be reported and discussed. 相似文献
993.
M. I. Kurkin 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(11):1607-1609
The conditions of compatibility of the magnetic sublattice hypothesis with the requirements of quantum theory have been derived. These conditions imply the presence of (even weak) magnetic anisotropy and a macroscopic number of spins in the sublattice. 相似文献
994.
Microstructure and oxygen stoichiometry of YBaCuO films manufactured by laser ablation are investigated. Dependence of the specific electrical resistivity and superconducting
parameters of films on microstructure and oxygen stoichiometry is demonstrated. Conditions of deposition are determined, under
which films with minimum microstructure defects and good conducting properties are formed.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 41–45, February, 2007. 相似文献
995.
The growth mechanism of the peritectic η phase involving the peritectic reaction and peritectic transformation in Cu-70%Sn alloy was investigated under directional
solidification. The results show that a major growth mechanism in thickening of the peritectic η-layer is not the peritectic reaction but the peritectic transformation. The transformation temperature and isothermal time
play crucial roles in determining the volume fraction and the thickness of the peritectic η phase. With the increase of the temperature and isothermal time, the volume fraction of the peritectic η phase increases. The regressed data show that the relationship between the thickness of η phase (Δx) and the transformation temperature (T) meets the following equation In Δx=6.5−1673 1 / T. Additionally, there exists a relationship between the thickness of the η phase (Δx) and the isothermal time (t) at the 9 mm solidification distance below the peritectic reaction interface, Δx=0.72t
1/2, which is consistent with the theoretical model.
Supported by the National Science Foundation of China (Grant No. 50395102) 相似文献
996.
Alvaro P. Raposo Hans J. Weber David E. Alvarez-Castillo Mariana Kirchbach 《Central European Journal of Physics》2007,5(3):253-284
We briefly review the five possible real polynomial solutions of hypergeometric differential equations. Three of them are
the well known classical orthogonal polynomials, but the other two are different with respect to their orthogonality properties.
We then focus on the family of polynomials which exhibits a finite orthogonality. This family, to be referred to as the Romanovski
polynomials, is required in exact solutions of several physics problems ranging from quantum mechanics and quark physics to
random matrix theory. It appears timely to draw attention to it by the present study. Our survey also includes several new
observations on the orthogonality properties of the Romanovski polynomials and new developments from their Rodrigues formula. 相似文献
997.
This paper reports a successful achievement of laser-induced biological cell fusion using an excimer laser excited dye laser. To our knowledge, we examined for the first time the dependence of fusion rate on laser pulse energy, number of laser pulses, and laser wavelength. Maximum fusion rate of approximately 50% was obtained by this laser fusion technology. 相似文献
998.
Trubetskov D. I. Koronovsky A. A. Khramov A. E. 《Radiophysics and Quantum Electronics》2004,47(5-6):305-331
We present the results of studying the phenomenon of synchronization in distributed electron–wave self-oscillatory systems with a counterpropagating wave. General laws governing the appearance of the classical synchronization in distributed systems are revealed. We propose methods for increasing the synchronization bandwidth by using the distributed input of a signal to the interaction space by means of coupled waveguide structures. Transient processes in nonautonomous self-oscillation regimes are studied. In particular, the effect of ultrafast synchronization is found. The possibility of chaotic synchronization in a gyro-oscillator with a counterpropagating wave under the action of a deterministic chaotic signal is shown. Mutual oscillation regimes in a system of two distributed oscillators with coupled waveguide systems are studied. 相似文献
999.
The use of liquid fuels such as kerosene is of interest for the pulse detonation engine (PDE). Within this context, the aim
of this work, which is a preliminary study, was to show the feasibility to initiate a detonation in air with liquid-fuel pyrolysis
products, using energies and dimensions of test facility similars to those of PDEs. Therefore, two liquids fuels have been
compared, JP10, which is a synthesis fuel generally used in the field of missile applications, and decane, which is one of
the major components of standard kerosenes (F-34, Jet A1, ...). The thermal degradation of these fuels was studied with two
pyrolysis processes, a batch reactor and a flow reactor. The temperatures varied from 600°C to 1,000°C and residence times
for the batch reactor and the flow reactor were, respectively, between 10–30 s and 0.1–2 s. Subsequently, the detonability
of synthetic gaseous mixtures, which was a schematisation of the decomposition state after the pyrolysis process, has been
studied. The detonability study, regarding nitrogen dilution and equivalence ratio, was investigated in a 50 mm-diameter,
2.5 m-long detonation tube. These dimensions are compatible with applications in the aircraft industry and, more particularly,
in PDEs. Therefore, JP10 and decane were compared to choose the best candidate for liquid-fuel PDE studies.
This paper was based on work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive
Systems, Montreal, Canada, July 31 – August 5, 2005. 相似文献
1000.
Based on the results of fracture in polymethyl methacrylate and a spheroplastic using a magnetic-pulse setup, the specific work of the formation of a new surface is estimated, which is similar to Griffith’s surface energy for quasi-static tests. The value obtained is greater than the corresponding value determined from the quasi-static tests by an order of magnitude and tends to increase as the loading time decreases. 相似文献