全文获取类型
收费全文 | 993篇 |
免费 | 21篇 |
国内免费 | 6篇 |
专业分类
化学 | 601篇 |
晶体学 | 7篇 |
力学 | 19篇 |
数学 | 107篇 |
物理学 | 286篇 |
出版年
2020年 | 13篇 |
2019年 | 9篇 |
2016年 | 18篇 |
2015年 | 20篇 |
2014年 | 13篇 |
2013年 | 19篇 |
2012年 | 32篇 |
2011年 | 42篇 |
2010年 | 31篇 |
2009年 | 32篇 |
2008年 | 26篇 |
2007年 | 38篇 |
2006年 | 41篇 |
2005年 | 46篇 |
2004年 | 36篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 24篇 |
2000年 | 11篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 14篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1989年 | 11篇 |
1987年 | 9篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1978年 | 10篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1943年 | 12篇 |
1933年 | 11篇 |
1931年 | 8篇 |
1930年 | 9篇 |
1926年 | 7篇 |
1924年 | 8篇 |
1923年 | 10篇 |
1902年 | 7篇 |
1881年 | 7篇 |
排序方式: 共有1020条查询结果,搜索用时 15 毫秒
31.
L. Fuentes K. Feldmann K. Walther L. P. Drechsler I. Doerfel E. N. Vlassova V. I. Matorin M. Betzl 《Crystal Research and Technology》1987,22(3):449-454
In the present work the connection between magnetic properties and texture of two samples of the tetragonal Mn Al phase is investigated. The specimens have been prepared by different cold deformation methods to get various texture types. For texture analysis neutron time-of-flight technique has been applied. Some aspects of the mathematical treatment of experimental data has been discussed. The main texture components in the inverse pole figures are inclined with respect to the direction of easy magnetization. Therefore, improved magnetic properties of the material can be expected using more optimal preparation techniques. 相似文献
32.
33.
Kummerlöwe G Grage SL Thiele CM Kuprov I Ulrich AS Luy B 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(1):19-30
The successful measurement of anisotropic NMR parameters like residual dipolar couplings (RDCs), residual quadrupolar couplings (RQCs), or residual chemical shift anisotropy (RCSA) involves the partial alignment of solute molecules in an alignment medium. To avoid any influence of the change of environment from the isotropic to the anisotropic sample, the measurement of both datasets with a single sample is highly desirable. Here, we introduce the scaling of alignment for mechanically stretched polymer gels by varying the angle of the director of alignment relative to the static magnetic field, which we call variable angle NMR spectroscopy (VA-NMR). The technique is closely related to variable angle sample spinning NMR spectroscopy (VASS-NMR) of liquid crystalline samples, but due to the mechanical fixation of the director of alignment no sample spinning is necessary. Also, in contrast to VASS-NMR, VA-NMR works for the full range of sample inclinations between 0° and 90°. Isotropic spectra are obtained at the magic angle. As a demonstration of the approach we measure 13C-RCSA values for strychnine in a stretched PDMS/CDCl? gel and show their usefulness for assignment purposes. In this context special care has been taken with respect to the exact calibration of chemical shift data, for which three approaches have been derived and tested. 相似文献
34.
Alwin Walther 《Monatshefte für Mathematik》1933,40(1):444-457
Ohne Zusammenfassung 相似文献
35.
Cremer Sauer Strubecker Walther Durand Kuntzmann Stiefel 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1957,8(5):425-427
Ohne Zusammenfassung 相似文献
36.
One-atom maser 总被引:2,自引:0,他引:2
37.
Dr. Alexey S. Kiryutin Dr. Grit Sauer Dr. Daniel Tietze Martin Brodrecht Stephan Knecht Prof. Dr. Alexandra V. Yurkovskaya Prof. Dr. Konstantin L. Ivanov Dr. Olga Avrutina Prof. Dr. Harald Kolmar Prof. Dr. Gerd Buntkowsky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(16):4025-4030
Two-dimensional NMR spectroscopy is one of the most important spectroscopic tools for the investigation of biological macromolecules. However, due to the low sensitivity of NMR spectroscopy, it takes usually from several minutes to many hours to record such spectra. Here, the possibility of detecting a bioactive derivative of the sunflower trypsin inhibitor-1 (SFTI-1), a tetradecapeptide, by combining parahydrogen-induced polarization (PHIP) and ultrafast 2D NMR spectroscopy is shown. The PHIP activity of the inhibitor was achieved by labeling with O-propargyl-l -tyrosine. In 1D PHIP experiments a signal enhancement of a factor of approximately 1200 compared to standard NMR was found. This enhancement permits measurement of 2D NMR correlation spectra of low-concentrated SFTI-1 in less than 10 seconds, employing ultrafast single-scan 2D NMR detection. As experimental examples PHIP-assisted ultrafast single-scan TOCSY spectra of SFTI-1 are shown. 相似文献
38.
Marcos Juanes Rizalina T. Saragi Prof. Dr. Walther Caminati Prof. Dr. Alberto Lesarri 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(49):11402-11411
In the last decade, experiment and theory have expanded our vision of non-covalent interactions (NCIs), shifting the focus from the conventional hydrogen bond to new bridging interactions involving a variety of weak donor/acceptor partners. Whereas most experimental data originate from condensed phases, the introduction of broadband (chirped-pulse) microwave fast-passage techniques has revolutionized the field of rotational spectroscopy, offering unexplored avenues for high-resolution studies in the gas phase. We present an outlook of hot topics for rotational investigations on isolated intermolecular clusters generated in supersonic jet expansions. Rotational spectra offer very detailed structural data, easily discriminating the isomeric or isotopic composition and effectively cancelling any solvent, crystal, or matrix bias. The direct comparison with quantum mechanical predictions provides insight into the origin of the inter- and intramolecular interactions with much greater precision than any other spectroscopic technique, simultaneously serving as test-bed for fine-tuning of theoretical methods. We present recent examples of rotational investigations around three topics: oligomer formation, chiral recognition, and identification of halogen, chalcogen, pnicogen, or tetrel bonds. The selected examples illustrate the benefits of rotational spectroscopy for the structural and energetic assessment of inter-/intramolecular interactions, which may help to move from fundamental research to applications in supramolecular chemistry and crystal engineering. 相似文献
39.