全文获取类型
收费全文 | 6844篇 |
免费 | 221篇 |
国内免费 | 8篇 |
专业分类
化学 | 4799篇 |
晶体学 | 17篇 |
力学 | 74篇 |
数学 | 1091篇 |
物理学 | 1092篇 |
出版年
2023年 | 47篇 |
2021年 | 62篇 |
2020年 | 133篇 |
2019年 | 103篇 |
2018年 | 60篇 |
2016年 | 152篇 |
2015年 | 133篇 |
2014年 | 132篇 |
2013年 | 192篇 |
2012年 | 262篇 |
2011年 | 318篇 |
2010年 | 158篇 |
2009年 | 170篇 |
2008年 | 240篇 |
2007年 | 234篇 |
2006年 | 236篇 |
2005年 | 177篇 |
2004年 | 191篇 |
2003年 | 139篇 |
2002年 | 143篇 |
2001年 | 110篇 |
2000年 | 106篇 |
1999年 | 101篇 |
1998年 | 89篇 |
1997年 | 75篇 |
1996年 | 59篇 |
1995年 | 88篇 |
1994年 | 96篇 |
1993年 | 84篇 |
1992年 | 82篇 |
1991年 | 85篇 |
1990年 | 72篇 |
1989年 | 80篇 |
1988年 | 80篇 |
1987年 | 80篇 |
1986年 | 77篇 |
1985年 | 107篇 |
1984年 | 96篇 |
1983年 | 88篇 |
1982年 | 94篇 |
1981年 | 71篇 |
1980年 | 86篇 |
1979年 | 98篇 |
1978年 | 77篇 |
1977年 | 88篇 |
1976年 | 86篇 |
1975年 | 61篇 |
1974年 | 52篇 |
1973年 | 55篇 |
1934年 | 50篇 |
排序方式: 共有7073条查询结果,搜索用时 31 毫秒
11.
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
12.
Georg von Georgievics 《Monatshefte für Chemie / Chemical Monthly》1885,6(1):754-759
Ohne ZusammenfassungDiese Untersuchung ist vor mehr als Jahresfrist infolge Eintrittes in die chemische Praxis abgebrochen worden. Äussere Verhältnisse machen die Vollendung der begonnenen Versuche auch weiterhin unmöglich und sehe ich mich desshalb veranlasst, meine Beobachtungen zu veröffentlichen. 相似文献
13.
14.
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
15.
In this Note, we give a necessary and sufficient condition for Lagrangians in a symplectic vector bundle to be deformed stably into transversal Lagrangians. In the case of three Lagrangians, we show that the associated Grothendieck group can be identified with a Hermitian K-theory group. To cite this article: M. Karoubi, M.L. Lapa de Souza, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
16.
Using spatially modulated illumination (SMI) light microscopy it is possible to measure the sizes of fluorescent structures that have an extension far below the conventional optical resolution limit (“subresolution size”). Presently, the sizes are determined as the object extension along the optical axis of the SMI microscope. For this, however, “a priori” assumptions on the fluorochrome distribution (“shape”) within the examined fluorescent structure have to be made. Usually it is assumed that the fluorochrome follows a Gauss-distribution or a spherical distribution. In this report we overcome the necessity to make an assumption on the shape of the fluorochrome distribution. We introduce two new experimentally obtained parameters which allow the determination of a shape measure to describe the spatial distribution of the fluorescent dye. This becomes possible by independent measurements with different excitation wavelengths. As an example, we present shape parameter measurements on individual fluorescent microspheres with a nominal geometrical diameter (“size”) of 190 nm. In the case investigated, the experimental shape correlated well with a homogeneous fluorochrome distribution (“spherical shape”) but not with a variety of other “shapes”. 相似文献
17.
18.
19.
Georg Pólya 《Mathematische Zeitschrift》1923,18(1):96-108
Ohne Zusammenfassung 相似文献
20.