全文获取类型
收费全文 | 439篇 |
免费 | 27篇 |
专业分类
化学 | 355篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 59篇 |
物理学 | 48篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 17篇 |
2014年 | 13篇 |
2013年 | 30篇 |
2012年 | 20篇 |
2011年 | 30篇 |
2010年 | 22篇 |
2009年 | 16篇 |
2008年 | 25篇 |
2007年 | 20篇 |
2006年 | 24篇 |
2005年 | 20篇 |
2004年 | 20篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1974年 | 2篇 |
1944年 | 1篇 |
1932年 | 1篇 |
1924年 | 1篇 |
排序方式: 共有466条查询结果,搜索用时 0 毫秒
21.
22.
23.
Tamás Hergert Bálint Varga Angelika Thurner Ferenc Faigl Béla Mátravölgyi 《Tetrahedron》2018,74(16):2002-2008
5-Formyl-2-thiopheneboronic acid is a widely used building block for the synthesis of diverse structures, however, due to a significant instability its transformation to 5-arylthiophene-2-carboxaldehydes by CC couplings could be performed only in low yields. Herein, as a solution, a convenient technique is described for the preparation of 1,3-dioxolane-protected 5-arylthiophene-2-carboxaldehydes via a one-pot borylation–copper(I) chloride co-catalyzed Suzuki-Miyaura coupling reaction. The utilization of the in situ prepared 2-thiopheneboronic ester derivative is allowed by the method developed. Elimination of the crucial, acidic liberation step of boronic acid species resulted in improved yields and purities. In addition, comparison of various aryl bromides is shown to demonstrate the high tolerance of the transformation to functional groups. 相似文献
24.
Angelika Jungmann R. Claessen R. Zimmermann Ge Meng P. Steiner S. Hüfner S. Tratzky K. Stöwe H. P. Beck 《Zeitschrift für Physik B Condensed Matter》1995,97(1):25-34
The electronic structure of the layered compounds LaI2 and CeI2 was investigated by photoemission and electron energy loss spectroscopy. From the experimental results we are able to confirm the metallic nature of these compounds, and by using photon energy dependent measurements of the valence band we can identify the orbital character of the conduction band as essentially 5d1-like. A detailed analysis of the Ce 3d and 4f spectra yields a remarkably small 4f-5d hybridization strength, almost completely decoupling the f-electron from the conduction band, which makes CeI2 a somewhat unusual system compared to other metallic Ce compounds. Band structure calculations by Jepsen and Andersen [1] confirm these experimental results. 相似文献
25.
Angelika Betten 《Archiv der Mathematik》1969,20(5):471-480
Ohne Zusammenfassung 相似文献
26.
27.
The Kováts retention indices of all 93 acyclic octenes on polydimethylsiloxane and squalane as stationary phases as well as their mass spectra were measured. The means of gas chromatography-mass spectrometry (GC-MS) were used for confirmation of GC identification as well as for mass spectrometric deconvolution of the majority of gas chromatographic unseparated isomeric octene peaks. The distinction between corresponding E and Z acyclic octenes, that is either difficult or even impossible by means of GC-MS, was obtained on the basis of larger temperature coefficients of retention indices for Z isomeric octenes than for corresponding E isomers. The retention data expressed as homomorphy factors were correlated with the degree of branching, position of double bond, and position of alkyl group with respect to the double bond of acyclic octenes, and the structure-retention relationships were formulated. The 81 acyclic octenes were identified in FCC gasoline. 相似文献
28.
Angelika Bikner-Ahsbahs 《ZDM》2003,35(5):208-223
How does the development of ideal types contribute to an empirically based construction of theories in the interpretative research of mathematics education? Before answering this question I clarify what is meant by the termstheory andideal type. Personal ideal types, ideal types of actions andsituational ideal types are going to be distinguished. Representing research examples. I show that forming ideal types can be considered as a methodical principle for empirically grounded theory construction with common features and different heuristics. 相似文献
29.
30.
Hennig A Hoffmann A Borcherding H Thiele T Schedler U Resch-Genger U 《Chemical communications (Cambridge, England)》2011,47(27):7842-7844
We introduce a method to determine the number of accessible functional groups on a polymer microsphere surface based on the interaction between the macrocyclic host cucurbit[7]uril (CB7) and a guest reacted to the microsphere surface. After centrifugation, CB7 in the supernatant is quantified by addition of a fluorescent dye. The difference between added and detected CB7 affords the number of accessible surface functional groups. 相似文献