全文获取类型
收费全文 | 6193篇 |
免费 | 215篇 |
国内免费 | 16篇 |
专业分类
化学 | 4055篇 |
晶体学 | 63篇 |
力学 | 91篇 |
数学 | 939篇 |
物理学 | 1276篇 |
出版年
2021年 | 62篇 |
2020年 | 91篇 |
2019年 | 106篇 |
2018年 | 62篇 |
2017年 | 64篇 |
2016年 | 148篇 |
2015年 | 149篇 |
2014年 | 152篇 |
2013年 | 272篇 |
2012年 | 268篇 |
2011年 | 310篇 |
2010年 | 228篇 |
2009年 | 169篇 |
2008年 | 272篇 |
2007年 | 258篇 |
2006年 | 234篇 |
2005年 | 229篇 |
2004年 | 209篇 |
2003年 | 156篇 |
2002年 | 183篇 |
2001年 | 114篇 |
2000年 | 141篇 |
1999年 | 111篇 |
1998年 | 103篇 |
1997年 | 99篇 |
1996年 | 94篇 |
1995年 | 98篇 |
1994年 | 120篇 |
1993年 | 119篇 |
1992年 | 89篇 |
1991年 | 86篇 |
1990年 | 80篇 |
1989年 | 61篇 |
1988年 | 51篇 |
1987年 | 60篇 |
1986年 | 70篇 |
1985年 | 81篇 |
1984年 | 69篇 |
1983年 | 66篇 |
1982年 | 55篇 |
1981年 | 51篇 |
1980年 | 77篇 |
1979年 | 50篇 |
1978年 | 66篇 |
1977年 | 69篇 |
1976年 | 54篇 |
1975年 | 61篇 |
1974年 | 47篇 |
1973年 | 63篇 |
1972年 | 37篇 |
排序方式: 共有6424条查询结果,搜索用时 15 毫秒
11.
Ralf Jäger Anatolij I. Saprykin J. Sabine Becker Hans -Joachim Dietze José A. C. Broekaert 《Mikrochimica acta》1997,125(1-4):41-44
The analytical capabilities of a high-resolution mass spectrometer in combination with a 13.56 MHz glow discharge ion source for the analysis of semiconducting materials (silicon carbide and gallium arsenide) were studied. It was shown that single positively charged ions of sample material have about 10 eV higher average energy than the ions of the discharge and residual gas. Therefore effective energy separation of the ions of analyte from the ions of the discharge and residual gas was achieved by adjusting the ion transfer optics (breadth and position of energy slit), which improves the analytical capabilities of the developed method.Some analytical applications are presented to illustrate the performance of r.f. GDMS for the bulk analysis of semiconducting materials. The results of the trace element analysis of gallium arsenide and silicon carbide samples are compared with data of independent methods (LIMS, ICP-AES, SIMS).Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthdayOn leave from the Institute of Inorganic Chemistry, 630090 Novosibirsk, Russia 相似文献
12.
13.
Unusual current‐voltage characteristics of single crystalline and bicrystalline La0.7Ca0.3MnO3 films
The current‐voltage characteristics of single crystalline and bicrystalline La0.7Ca0.3MnO3 films were measured and analyzed. Several epitaxial films, as well as 45° [001]‐tilt grain boundaries, display current‐voltage characteristics which are asymmetric with respect to polarity reversal of the bias current. One epitaxial film has a polarity dependent resistance of ~340kΩ and of ~670kΩ in forward and in reverse direction, respectively. 相似文献
14.
Time-resolved electron transport studies on InGaAs/GaAs-QWIPs 总被引:1,自引:0,他引:1
S. Steinkogler H. Schneider R. Rehm M. Walther P. Koidl P. Grant R. Dudek H. C. Liu 《Infrared Physics & Technology》2003,44(5-6):355-361
Due to the short internal response time, quantum-well infrared photodetectors (QWIPs) are interesting for high-speed applications such as heterodyne spectroscopy or laser pulse monitoring. We studied the photocurrent transients of InGaAs/GaAs-QWIPs after irradiation with infrared laser pulses of 250 fs duration. The excitation wavelength of about 9 μm matches the peak wavelength of the QWIP structure. The photocurrent transient consists of two different dynamical components, representing the fast photoionization in the quantum-wells and the slow injection current that compensates the remaining space charge. The investigations of the different components as a function of temperature and bias voltage were performed on a nanosecond time-scale. The experimental separation of the two photocurrent contributions allows us to determine the photoconductive gain. The Fourier transform of the photocurrent transient was compared with other experimental methods including heterodyne detection and microwave rectification. The quantitative agreement between these different measurement techniques is excellent. 相似文献
15.
16.
Reaction diffusion systems on cylindrical domains with terms that vary rapidly and periodically in the unbounded direction can be analyzed by averaging techniques. Here, using iterated normal form transformations and Gevrey regularity of bounded solutions, we prove a result on exponential averaging for such systems, i.e., we show that traveling wave solutions can be described by a spatially homogenous equation and exponentially small remainders. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
17.
H. Glatzel R. Schneider T. Fauster V. Dose 《Zeitschrift für Physik B Condensed Matter》1992,88(1):53-61
Inverse photoemission spectra were taken for thin epitaxial iron films on Cu(100). For a film thickness of eight monolayers the observed electronic states are characteristic for a fcc(100) surface. Thed-bands of iron show a ferromagnetic exchange splitting of 1.1 eV, considerably smaller than the bulk value of 1.8 eV, which we observe for film thicknesses above 18 monolayers. 相似文献
18.
19.
B. Pümpin H. Keller W. Kündig I. M. Savić J. W. Schneider H. Simmler P. Zimmermann E. Kaldis S. Rusiecki C. Rossel 《Hyperfine Interactions》1991,63(1-4):25-31
A systematic μSR study of the local magnetic field distribution in a series of oxygen deficient YBa2Cu3O
x
samples with 6.5⩽x⩽7.0 is reported. Special attention was given to perform the experiments under the same conditions, so that the oxygen content
of the measured samples was the only parameter varied. The behavior of the depolarization rate σ as a function of the oxygen
contentx was found to have strong similarities with the behavior of the critical temperatureT
c
as a function ofx. In particular, two step-like increases of σ were observed abovex=6.7 and 6.9. The temperature dependence of the normalized depolarization rate σ(T)/σ(0) is well described by the two-fluid model forx⩾6.781(1) and clearly deviates from this behavior forx⩽6.704(1). Our results are compared to those obtained by other groups. 相似文献
20.