全文获取类型
收费全文 | 723篇 |
免费 | 16篇 |
国内免费 | 1篇 |
专业分类
化学 | 459篇 |
晶体学 | 37篇 |
力学 | 11篇 |
数学 | 57篇 |
物理学 | 176篇 |
出版年
2020年 | 6篇 |
2019年 | 8篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 14篇 |
2014年 | 13篇 |
2013年 | 34篇 |
2012年 | 25篇 |
2011年 | 29篇 |
2010年 | 19篇 |
2009年 | 27篇 |
2008年 | 24篇 |
2007年 | 38篇 |
2006年 | 20篇 |
2005年 | 24篇 |
2004年 | 14篇 |
2003年 | 13篇 |
2002年 | 21篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1983年 | 16篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 18篇 |
1977年 | 20篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 10篇 |
1973年 | 8篇 |
1971年 | 11篇 |
1956年 | 5篇 |
1955年 | 6篇 |
1933年 | 4篇 |
排序方式: 共有740条查询结果,搜索用时 281 毫秒
211.
212.
Craig E. Aalseth Anthony R. Day Eric W. Hoppe Todd W. Hossbach Brian J. Hyronimus Martin E. Keillor Kevin E. Litke Esther E. Mintzer Allen Seifert Glen A. Warren 《Journal of Radioanalytical and Nuclear Chemistry》2009,282(1):233-237
High-purity copper has emerged as a preferred construction material for ultra-low-background HPGe spectrometers and offers
excellent bulk radiopurity along with good electrical, thermal, and vacuum properties. Recently, these materials and techniques
have been applied to the construction of low-background internal-source gas proportional counters. This work describes the
design, construction, and testing of an ultra-low-background internal-source gas proportional counter built primarily of high
purity electroformed copper. Energy resolution of ~10% FWHM at 59.5 keV has been achieved, a low-energy threshold of ~3 keV
has been reached, and gas gain stability over a 4-week period has been demonstrated. Progress toward low-background operation
is described. 相似文献
213.
214.
G. Seifert T. Heine P.W. Fowler 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):341-343
The possibility of stable non-carbon fullerenes is discussed for the case of phosphorus fullerene-like cage structures. On
the basis of Density Functional Tight Binding calculations it is shown that many such cages correspond to metastable structures,
but with increasing nuclearity become less stable with respect to separate molecular P4 units. Stability rules, known for carbon fullerenes, such as the “isolated pentagon rule”, do not reflect the different electronic
and steric requirements of the phosphorus atom. The computational results tend to rule out phosphorus fullerenes. 相似文献
215.
Zusammenfassung Aus Scandiummetall und Kohlepulver hergestelltes ScC zersetzt sich bei Lagern an Luft unter Bildung von -ScOOH. Dagegen bleibt ScC, das durch Carburieren aus Sc2O3 erhalten wurde, unter denselben Bedingungen selbst nach mehreren Monaten unverändert. Das gebildete -ScOOH ist sehr gut kristallisiert, viel besser als durch Fällung gewonnene Präparate. Die vonMilligan undMcAtee ermittelte Böhmit-Struktur wird bestätigt; die Gitterkonstanten wurden neu bestimmt. 相似文献
216.
Factors influencing the 18O/16O-ratio in meat juices 总被引:2,自引:0,他引:2
With respect to the question of whether the 18O/16O-ratio of meat water could be used for meat origin analysis, factors influencing its delta18O-value have been examined. The 18O/16O-ratio of meat water differs geographically, similar to known differences in precipitation and ground water. In Great Britain higher enrichments in 18O were found in southern samples and in Germany in northern samples. However, it was not possible to distinguish between British and German beef: their 18O/16O-ratios overlapped. British bovine samples the variation range of delta18O-values was 2.8 per thousand; in porcine samples it was 2.0 per thousand. British meat liquids from beef were enriched in 18O by 1.3 +/- 0.3 per thousand compared with pork. In porcine samples of litter mates with identical breeding and age at slaughter, the range in the delta18O-values among individuals was 2.4 per thousand. Experiments revealed significant influences of the meat's storage and handling conditions on the 18O/16O-ratio. After 10 h at 21.5 or 18.5 degrees C the delta18O-value increased by 0.4 or 0.3 per thousand per h, respectively, in samples (50 g) of chopped meat. The observed magnitude of changes might compensate for the geographical and seasonal differences. A precise origin assignment of the affected specimen on the base of delta18O-values of meat water is hence bound to be impossible. 相似文献
217.
Seifert U 《Physical review letters》2005,95(4):040602
For stochastic nonequilibrium dynamics like a Langevin equation for a colloidal particle or a master equation for discrete states, entropy production along a single trajectory is studied. It involves both genuine particle entropy and entropy production in the surrounding medium. The integrated sum of both Delatas(tot) is shown to obey a fluctuation theorem (exp([-Deltas(tot) = 1 for arbitrary initial conditions and arbitrary time-dependent driving over a finite time interval. 相似文献
218.
T.?SpeckEmail author U.?Seifert 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,43(4):521-527
We study n-dimensional diffusive motion in an externally driven harmonic
potential. For these systems the probability distribution of
the applied work is a Gaussian. We give explicit expressions for its mean
and variance, which are determined by a non-local integral kernel
relating the time-derivatives of the applied forces. As illustrations, we
specialize our results to dragging a colloidal particle through a viscous
fluid and to stretching a Rouse polymer with different protocols. 相似文献
219.
220.
Flink C Feick H McHugo SA Seifert W Hieslmair H Heiser T Istratov AA Weber ER 《Physical review letters》2000,85(23):4900-4903
Concentrations of mobile interstitial copper and precipitated copper in silicon were studied after a high temperature intentional contamination and quench to room temperature. It was found that below a critical contamination the copper predominantly diffuses out to the surface, while for higher initial copper concentrations it mainly precipitates in the bulk. The critical copper contamination equals the acceptor concentration plus 10(16) cm (-3). This behavior can be explained by the electrostatic interaction between the positively charged interstitial copper and the forming copper precipitates. 相似文献