全文获取类型
收费全文 | 4393篇 |
免费 | 61篇 |
国内免费 | 14篇 |
专业分类
化学 | 2809篇 |
晶体学 | 13篇 |
力学 | 43篇 |
数学 | 703篇 |
物理学 | 900篇 |
出版年
2020年 | 49篇 |
2019年 | 25篇 |
2016年 | 55篇 |
2015年 | 62篇 |
2014年 | 54篇 |
2013年 | 112篇 |
2012年 | 138篇 |
2011年 | 145篇 |
2010年 | 85篇 |
2009年 | 74篇 |
2008年 | 118篇 |
2007年 | 127篇 |
2006年 | 134篇 |
2005年 | 104篇 |
2004年 | 103篇 |
2003年 | 85篇 |
2002年 | 81篇 |
2001年 | 70篇 |
2000年 | 73篇 |
1999年 | 81篇 |
1998年 | 51篇 |
1997年 | 67篇 |
1996年 | 71篇 |
1995年 | 64篇 |
1994年 | 78篇 |
1993年 | 85篇 |
1992年 | 76篇 |
1991年 | 64篇 |
1990年 | 58篇 |
1989年 | 54篇 |
1988年 | 52篇 |
1987年 | 66篇 |
1986年 | 66篇 |
1985年 | 92篇 |
1984年 | 67篇 |
1983年 | 57篇 |
1982年 | 70篇 |
1981年 | 65篇 |
1980年 | 84篇 |
1979年 | 82篇 |
1978年 | 77篇 |
1977年 | 67篇 |
1976年 | 83篇 |
1975年 | 51篇 |
1974年 | 50篇 |
1973年 | 60篇 |
1972年 | 40篇 |
1971年 | 28篇 |
1970年 | 38篇 |
1967年 | 33篇 |
排序方式: 共有4468条查询结果,搜索用时 6 毫秒
1.
2.
3.
J. Maul I. Strachnov S. Karpuk P. Bernhard A. Oelsner G. Schönhense G. Huber 《Applied Physics A: Materials Science & Processing》2006,82(1):43-47
We report morphologic changes of metallic surfaces at the onset of ablation, starting from gentle ablation to the emergence of ablation craters. The evolution of both observed melting zones and of ablation craters therein are investigated in dependence of the ablation laser fluence for nanosecond ultraviolet laser pulses. Further, consequences of crater formation for cluster synthesis within the released atomic vapor are pointed out. PACS 52.38.Mf; 79.20.Ds; 65.40.De 相似文献
4.
C. Czeranowsky V. M. Baev G. Huber P. A. Khandokhin Ya. I. Khanin I. V. Koryukin E. Yu. Shirokov 《Radiophysics and Quantum Electronics》2004,47(10-11):723-728
Experimental study of low-frequency dynamics of an intracavity frequency-doubled Nd:YAG laser demonstrates the influence of the interaction of orthogonally polarized modes, participating in frequency doubling (type II phase matching), on the stability of the laser output. At a sufficiently low pump rate and low conversion efficiency, the laser shows stable operation with a low noise level at the frequencies of relaxation oscillations. At a high pump power and/or a high conversion efficiency, the laser emission becomes unstable as a result of Hopf bifurcation at the frequencies of relaxation oscillations that are responsible for the anti-phase polarization dynamics of the laser. 相似文献
5.
The pumiceous products of the large-scale explosive eruptions at Santorini show a high grade of similarity in their optical
appearance as well as in their chemical composition. The demand for a clear classification of these eruption products was
raised from archaeological research, where pumice can be interpreted as a “post-eruption” time marker. The aim of this work
was to find elements that underwent significant changes because of geochemical processes and that could be indicative for
a distinction of pumice produced by the five major explosive eruptions. INAA of 25 elements allows a clear classification
and contributes new information to the chemical evolution of Santorini volcano.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Summary In the present paper we study truncated projections for the fanbeam geometry in computerized tomography. First we derive consistency conditions for the divergent beam transform. Then we study a singular value decomposition for the case where only the interior rays in the fan are provided, as for example in region-of-interest tomography. We show that the high angular frequency components of the searched-for densities are well determined and we present reconstructions from real data where the missing information is approximated based on the singular value decomposition.The work of the authors was supported by the Deutsche Forschungsgemeinschaft under grant Lo 310/2-4 相似文献
7.
Employing positive-definiteness arguments we analyse Boson field states, which combine classical and quantum mechanical features (signal and noise), in a constructive manner. Mathematically, they constitute Bauer simplexes within the convex, weak-*-compact state space of the C*-Weyl algebra, defined by a presymplectic test function space (smooth one-Boson wave functions) and are affinely homeomorphic to a state space of a classical field. The regular elements are expressed in terms of weak distributions (probability premeasures) on the dual test function space. The Bauer simplex arising from the bare vacuum is shown to generalize the quantum optical photon field states with positive P-functions. 相似文献
8.
9.
10.
A simple and fast HPLC method for the determination of glycols is described. It is characterized by a reversed-phase separation using water as eluent and a refractive index detection. The method was applied to investigate the biodegradation of glycols in a laboratory activated sludge plant and to determine the content of glycols or alcohols in detergents. The detection limit is 4 mg/l ethylene glycol or propylene glycol in an aqueous sample. 相似文献