全文获取类型
收费全文 | 537053篇 |
免费 | 6625篇 |
国内免费 | 1521篇 |
专业分类
化学 | 288895篇 |
晶体学 | 7735篇 |
力学 | 23601篇 |
综合类 | 18篇 |
数学 | 62440篇 |
物理学 | 162510篇 |
出版年
2021年 | 4383篇 |
2020年 | 4910篇 |
2019年 | 5278篇 |
2018年 | 6792篇 |
2017年 | 6651篇 |
2016年 | 10348篇 |
2015年 | 6538篇 |
2014年 | 10037篇 |
2013年 | 24381篇 |
2012年 | 18696篇 |
2011年 | 23094篇 |
2010年 | 16130篇 |
2009年 | 16014篇 |
2008年 | 21154篇 |
2007年 | 21106篇 |
2006年 | 19677篇 |
2005年 | 17707篇 |
2004年 | 16295篇 |
2003年 | 14309篇 |
2002年 | 14223篇 |
2001年 | 15985篇 |
2000年 | 12147篇 |
1999年 | 9500篇 |
1998年 | 8024篇 |
1997年 | 7701篇 |
1996年 | 7413篇 |
1995年 | 6691篇 |
1994年 | 6643篇 |
1993年 | 6365篇 |
1992年 | 7168篇 |
1991年 | 7269篇 |
1990年 | 6898篇 |
1989年 | 6730篇 |
1988年 | 6752篇 |
1987年 | 6594篇 |
1986年 | 6241篇 |
1985年 | 8069篇 |
1984年 | 8305篇 |
1983年 | 6683篇 |
1982年 | 6882篇 |
1981年 | 6757篇 |
1980年 | 6315篇 |
1979年 | 6848篇 |
1978年 | 7073篇 |
1977年 | 6867篇 |
1976年 | 6865篇 |
1975年 | 6417篇 |
1974年 | 6459篇 |
1973年 | 6397篇 |
1972年 | 4493篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
In this paper we show that the Boltzmann weights of the three-dimensional Baxter-Bazhanov model give representations of the braid group if some suitable spectral limits are taken. In the trigonometric case we classify all possible spectral limits which produce braid group representations. Furthermore, we prove that for some of them we get cyclotomic invariants of links and for others we obtain tangle invariants generalizing the cyclotomic ones. 相似文献
992.
993.
P. González D. Fernández J. Pou E. García J. Serra B. León M. Pérez-Amor T. Szörényi 《Applied Physics A: Materials Science & Processing》1993,57(2):181-185
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO
x
films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase. 相似文献
994.
L. M. Mironovich 《Chemistry of Heterocyclic Compounds》1994,30(9):1092-1094
3-Hydrazino-6-tert-butyl-1,2,4-triazolo[3,4,c]-1,2,4-triazin-5-one was synthesized by the reaction of a substituted 4-(N,N-dimethylcarbamoyl)-3-thioxo-1,2,4-triazine with hydrazine. The spectral characteristics and the proposed reaction mechanism are discussed.The Sumy State University, Sumy 244007. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1258–1260, September, 1994. Original article submitted September 14, 1994. 相似文献
995.
996.
997.
Vogel N. Heinzinger J. Cichos F. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(6):926-931
The cathode spot formation in air within the first 170 ns was investigated by laser absorption photography and ps-pulse interferometry. The discharge was initiated between electrodes made from Ag or Pd with cathode-anode distance below 300 μm, the arc duration was some milliseconds, and the arc current 5-10 A. Picosecond holographic interferometry and momentary absorption photography yielded spatial-temporal density distributions in the ignition phase of the cathode spot. An absolute electron density value on the order of 4×1026 m-3 has been found. In contrast to vacuum, the cathode spot plasmas broaden little with increasing distance from the cathode, thus narrow plasma channels are observed in the vicinity of the cathode surface having diameters <20 μm 相似文献
998.
999.
A. A. Bormisov E. S. Gudkova F. Kh. Mukminov 《Theoretical and Mathematical Physics》1997,113(2):1418-1430
We consider equations of the form Uxy = U * Ux, where U(x, y) is a function taking values in an arbitrary finite-dimensional algebra T over the field ℂ. We show that every
such equation can be naturally associated with two characteristic Lie algebras, Lx and Ly. We define the notion of a ℤ-graded Lie algebraB corresponding to a given equation. We prove that for every equation under consideration, the corresponding algebraB can be taken as a direct sum of the vector spaces Lx and Ly if we define the commutators of the elements from Lx and Ly by means of the zero-curvature relations. Assuming that the algebra T has no left ideals, we classify the equations of the
specified type associated with the finite-dimensional characteristic Lie algebras Lx and Ly. All of these equations are Darboux-integrable.
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 113, No. 2, pp. 261–275, November, 1997. 相似文献
1000.
The effect of 57Fe hyperfine interaction radiofrequency (rf) modulation by external rotating magnetic field was studied in thin Permalloy foil by means of Mössbauer spectroscopy. The rf effect was investigated as a function of intensity for several rf field frequencies. The experiments show that the external rotating rf field causes considerable changes in the hyperfine pattern. The obtained spectra are in disagreement with those obtained by Perlow [Phys. Rev. 172 (1968) 319]. They also are inconsistent with magnetostriction hypothesis. Proceeding from the Mössbauer spectrum analysis one may conclude that the magnetization of investigated foil changes its direction in a complex manner. However, the undertaken experiments show that the essential number of Mössbauer nuclei experience the rotating magnetic field influence. 相似文献