全文获取类型
收费全文 | 168156篇 |
免费 | 1936篇 |
国内免费 | 419篇 |
专业分类
化学 | 94125篇 |
晶体学 | 2548篇 |
力学 | 6420篇 |
综合类 | 3篇 |
数学 | 17264篇 |
物理学 | 50151篇 |
出版年
2021年 | 1245篇 |
2020年 | 1501篇 |
2019年 | 1556篇 |
2018年 | 2084篇 |
2017年 | 2079篇 |
2016年 | 3308篇 |
2015年 | 2162篇 |
2014年 | 2988篇 |
2013年 | 7399篇 |
2012年 | 6173篇 |
2011年 | 7255篇 |
2010年 | 4959篇 |
2009年 | 4944篇 |
2008年 | 6875篇 |
2007年 | 6693篇 |
2006年 | 6439篇 |
2005年 | 5911篇 |
2004年 | 5344篇 |
2003年 | 4805篇 |
2002年 | 4631篇 |
2001年 | 5999篇 |
2000年 | 4384篇 |
1999年 | 3397篇 |
1998年 | 2339篇 |
1997年 | 2422篇 |
1996年 | 2369篇 |
1995年 | 2115篇 |
1994年 | 2150篇 |
1993年 | 1923篇 |
1992年 | 2402篇 |
1991年 | 2474篇 |
1990年 | 2303篇 |
1989年 | 2254篇 |
1988年 | 2222篇 |
1987年 | 2227篇 |
1986年 | 2051篇 |
1985年 | 2576篇 |
1984年 | 2591篇 |
1983年 | 2032篇 |
1982年 | 2037篇 |
1981年 | 1886篇 |
1980年 | 1874篇 |
1979年 | 2120篇 |
1978年 | 2187篇 |
1977年 | 2151篇 |
1976年 | 2055篇 |
1975年 | 1939篇 |
1974年 | 1895篇 |
1973年 | 1939篇 |
1972年 | 1273篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
S. O. Kolusheva B. A. Salakhutdinov T. F. Aripov L. P. Vernon 《Chemistry of Natural Compounds》1994,29(4):523-525
It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993. 相似文献
42.
43.
T. A. Beu 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,27(3):263-266
New analytical formulas for the torsionL-tensor are reported, which are used in molecular normal mode analysis calculations for the nonlinear transformation of the force constants from internal coordinates to normal coordinates. The proposed formalism exhibits a relative simplicity as compared to previous reported results. Sample calculations for methanol and hydrazine are presented. 相似文献
44.
V. Palyok I.A. Szabó D.L. Beke A. Kikineshi 《Applied Physics A: Materials Science & Processing》2002,74(5):683-687
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence
of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in
a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization
can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior
of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism.
Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced
fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process
may be useful for the various optoelectronic applications of photoconductive a-Se layers.
Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001 相似文献
45.
46.
47.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain
a decomposition of continuity. 相似文献
48.
The paper mentioned above is a contribution of the authors to Volume 18 (2002) of this journal, see . Recently, J. Domsta pointed out to us that the proof of Theorem 4.2 in that paper contains an error. The purpose of this
addendum is to present a correct argument for it. 相似文献
49.
Zarubitskii O. G. Budnik V. G. Omel'chuk A. A. Melekhin V. T. Opanasyuk V. P. Zakharchenko N. F. 《Russian Journal of Applied Chemistry》2002,75(4):558-561
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry. 相似文献
50.
Data Envelopment Analysis (DEA) offers a piece-wise linear approximation of the production frontier. The approximation tends to be poor if the true frontier is not concave, eg in case of economies of scale or of specialisation. To improve the flexibility of the DEA frontier and to gain in empirical fit, we propose to extend DEA towards a more general piece-wise quadratic approximation, called Quadratic Data Envelopment Analysis (QDEA). We show that QDEA gives statistically consistent estimates for all production frontiers with bounded Hessian eigenvalues. Our Monte-Carlo simulations suggest that QDEA can substantially improve efficiency estimation in finite samples relative to standard DEA models. 相似文献