全文获取类型
收费全文 | 1556篇 |
免费 | 29篇 |
国内免费 | 8篇 |
专业分类
化学 | 813篇 |
晶体学 | 10篇 |
力学 | 11篇 |
数学 | 205篇 |
物理学 | 554篇 |
出版年
2020年 | 21篇 |
2019年 | 15篇 |
2016年 | 30篇 |
2015年 | 23篇 |
2014年 | 24篇 |
2013年 | 45篇 |
2012年 | 36篇 |
2011年 | 56篇 |
2010年 | 42篇 |
2009年 | 30篇 |
2008年 | 43篇 |
2007年 | 61篇 |
2006年 | 52篇 |
2005年 | 38篇 |
2004年 | 41篇 |
2003年 | 39篇 |
2002年 | 34篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 17篇 |
1998年 | 18篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 34篇 |
1994年 | 36篇 |
1993年 | 27篇 |
1992年 | 24篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 24篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 21篇 |
1981年 | 27篇 |
1980年 | 23篇 |
1979年 | 20篇 |
1978年 | 24篇 |
1977年 | 28篇 |
1976年 | 14篇 |
1975年 | 18篇 |
1974年 | 19篇 |
1973年 | 11篇 |
1972年 | 12篇 |
1969年 | 13篇 |
1967年 | 12篇 |
1930年 | 12篇 |
排序方式: 共有1593条查询结果,搜索用时 15 毫秒
991.
Timo D. Stark Angel Angelov Mathias Hofmann Wolfgang Liebl Thomas Hofmann 《Analytical and bioanalytical chemistry》2013,405(30):9843-9848
The major carotenoid species isolated from the thermophilic bacterium Thermus thermophilus HB27 have been identified as zeaxanthin–glucoside–fatty acid esters (thermozeaxanthins and thermobiszeaxanthins). Most of the genes of the proposed T. thermophilus carotenoid pathway could be found in the genome, but there is less clarity about the genes which encode the enzymes performing the final carotenoid glycosylation and acylation steps. To get a further insight into the biosynthesis of thermo(bis)zeaxanthins in T. thermophilus, we deleted the megaplasmid open reading frame TT_P0062 (termed cruC) by both exchanging it with a kanamycin resistance cassette (ΔcruC:kat) and by generating a markerless gene deletion strain (ΔcruC). A fast and efficient electrospray ionization–ion mobility–time-of-flight mass spectrometry method via direct infusion was developed to compare the carotenoid profiles of wild type and mutant T. thermophilus cell culture extracts. These comparisons revealed significant alterations in the carotenoid composition of the ΔcruC mutant, which was found to accumulate zeaxanthin. This is the first experimental evidence that the ORF encodes the glycosyltransferase enzyme necessary for the glycosylation of zeaxanthin in the final modification steps of the thermozeaxanthin biosynthesis in T. thermophilus HB27. Also, the proposed method for direct determination of carotenoid amounts and species in crude acetone extracts represents an improvement over existing methods in terms of speed and sensitivity and may be applicable in high-throughput analyses of other terpenoids as well as other important bacterial metabolites like fatty acids and their derivatives. Figure
? 相似文献
992.
S. Menzel M. Pekar?ikova M. Hofmann T. Gemming K. Wetzig 《Applied Surface Science》2005,252(1):215-217
Material transport in Al/Ti-finger electrodes on LiNbO3 substrates of power-loaded surface acoustic wave (SAW) structures were investigated under microscopic observation with respect to stress-induced material transport. Additionally, investigations were carried out before and after SAW loading during lifetime experiments. For the experiments, a special power SAW test structure was applied realizing travelling SAWs. The results show that the microstructure of the electrodes was damaged by void and hillock formation even at moderate input power. This changes the electrical and acoustical properties of the SAW structures irreversibly. The logarithmic time-to-failure (TTF) of damaged SAW structures depends linearly on loading time and rf power. 相似文献
993.
We show that a suitable quantitative Fatou Theorem characterizes uniform rectifiability in the codimension 1 case.
相似文献994.
Karl Heinrich Hofmann 《Mathematische Zeitschrift》1961,75(1):295-298
Ohne Zusammenfassung 相似文献
995.
996.
Dirk Hofmann 《Applied Categorical Structures》2002,10(6):569-592
A categorical version of the famous theorem of Stone and Weierstrass is formulated and studied in detail. Several applications and examples are given. 相似文献
997.
Alex Chigogidze Karl H. Hofmann John R. Martin 《Transactions of the American Mathematical Society》1997,349(11):4537-4554
Some structure theorems for compact abelian groups are derived and used to show that every closed subset of an infinite compact metrizable group is the fixed point set of an autohomeomorphism. It is also shown that any metrizable product containing a positive-dimensional compact group as a factor has the property that every closed subset is the fixed point set of an autohomeomorphism.
998.
999.
1000.
U. Leinberger E. Berdermann F. Heine S. Heinz O. Joeres P. Kienle I. Koenig W. Koenig C. Kozhuharov A. Schröter H. Tsertos C. Hofmann G. Soff 《The European Physical Journal A - Hadrons and Nuclei》1998,1(3):249-256
We present the first energy and angle resolved measurements of e+e−-pairs emitted from heavy nuclei (Z≥ 40) at rest by internal pair conversion (IPC) of transitions with energies of less than 2 MeV as well as recent theoretical
results using the DWBA method, which takes full account of relativistic effects, magnetic substates and finite size of the
nucleus. The 1.76 MeV E0 transition in 90Zr (90Sr source) and the 1.77 MeV M1 transition in 207Pb (207Bi source) have been investigated experimentally using the essentially improved setup at the double-ORANGE β-spectrometer
of GSI. The measurements prove the capability of the setup to cleanly identify the IPC pairs in the presence of five orders
of magnitude higher β− and γ background from the same source and to yield essentially background-free sum spectra despite the large background.
Using the ability of the ORANGE setup to directly determine the opening angle of the e+e−–pairs (Θe+e−), the angular correlation of the emitted pairs was measured within the range covered experimentally (40°≤Θe+e−≤ 180°). In the 90Zr case the correlation could be deduced for a wide range of energy differences E
Δ of the pairs (−530 keV ≤E
Δ≤ 530 keV). The 90Zr results are in good agreement with recent theory. The angular correlation deduced for the M1 transition in 207Pb is in strong disagreement with theoretical predictions derived within the Born approximation and shows almost isotropic
character. This is again in agreement with the new theoretical results.
Received: 22 April 1997 / Revised version: 16 December 1997 相似文献