全文获取类型
收费全文 | 1801篇 |
免费 | 43篇 |
国内免费 | 2篇 |
专业分类
化学 | 1277篇 |
晶体学 | 10篇 |
力学 | 66篇 |
数学 | 173篇 |
物理学 | 320篇 |
出版年
2022年 | 14篇 |
2021年 | 21篇 |
2019年 | 18篇 |
2018年 | 20篇 |
2016年 | 32篇 |
2015年 | 28篇 |
2014年 | 36篇 |
2013年 | 85篇 |
2012年 | 57篇 |
2011年 | 74篇 |
2010年 | 60篇 |
2009年 | 40篇 |
2008年 | 67篇 |
2007年 | 69篇 |
2006年 | 73篇 |
2005年 | 75篇 |
2004年 | 53篇 |
2003年 | 66篇 |
2002年 | 41篇 |
2001年 | 40篇 |
2000年 | 32篇 |
1999年 | 16篇 |
1998年 | 23篇 |
1997年 | 11篇 |
1996年 | 31篇 |
1995年 | 33篇 |
1994年 | 30篇 |
1993年 | 35篇 |
1992年 | 25篇 |
1991年 | 24篇 |
1990年 | 25篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 30篇 |
1984年 | 24篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1977年 | 19篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1967年 | 16篇 |
1966年 | 20篇 |
1965年 | 39篇 |
1964年 | 45篇 |
排序方式: 共有1846条查询结果,搜索用时 15 毫秒
81.
Marcel Sickert Harald Weinstabl Brendan Peters Xiao Hou Mark Lautens 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(20):5247-5251
A palladium‐catalyzed intermolecular cross‐coupling of two aryl iodides is reported, giving polycyclic ring systems with a high level of convergence and efficiency. 相似文献
82.
Mathematical deconvolution methods can separate co-eluting peaks in samples for which (chromatographic) separation fail. However, these methods often heavily rely on manual user-input and interpretation. This is not only time-consuming but also error-prone and automation is needed if such methods are to be applied in a routine manner. 相似文献
83.
Christian Schönbeck René Holm Peter Westh Günther H. Peters 《Journal of inclusion phenomena and macrocyclic chemistry》2014,78(1-4):351-361
The formation of inclusion complexes of hydroxypropylated β-cyclodextrins (CDs) with three bile salts are investigated to shed light on the role played by the hydroxypropyl (HP) substituents. The HP-chains are situated at the rim of the CD and may thus extend the hydrophobic cavity of the CD. Calorimetric titrations in a broad temperature range and molecular dynamics simulations confirm previous speculations that the HP-chains cause an increase in dehydrated nonpolar surface area upon formation of the complexes. This additional burial of nonpolar surface area, 12–16 Å2 per HP-chain according to the MD simulations, results in more negative values of ΔC p °, which are in quantitative agreement with what is expected for hydrophobic dehydration. Although these observations support the picture of an extended hydrophobic cavity, HPβCD complexes were less stable than their unsubstituted counterparts. This indicates that increased hydrophobic contacts are not always accompanied by increased binding strength. The linear dependence of ΔC p °, ΔH° and ΔS° on the number of HP-chains give rise to isoentropic and isoenthalpic temperatures at which ΔH° and ΔS° are independent of the number of HP-chains on the host CD (but depend on the type of bile salt). Interestingly, these convergence temperatures are close to what is observed for unfolding of proteins and may be a common feature of hydrophobic dehydration. 相似文献
84.
Dr. Marcel Sickert Dr. Harald Weinstabl Brendan Peters Xiao Hou Prof. Dr. Mark Lautens 《Angewandte Chemie (International ed. in English)》2014,53(20):5147-5151
A palladium‐catalyzed intermolecular cross‐coupling of two aryl iodides is reported, giving polycyclic ring systems with a high level of convergence and efficiency. 相似文献
85.
Andreas Wieczorek Hua Yang Brendan Roycroft Frank H. Peters Brian Corbett 《Optical and Quantum Electronics》2013,45(4):365-371
Polarization insensitive optical coupling of a large spot size input waveguide to a small spot size photodiode is achieved by the introduction of a transition waveguide. The coupling efficiency to the photodetector and the related absorption efficiency of the photodiode depend mainly on the refractive indices of the different InGaAsP layers. Waveguide alignments, waveguide widths and the n-contact etch depth do not influence the absorption efficiency relative to a 1-dB tolerance. 相似文献
86.
Dr. Daniel Brodbeck Dr. Sonia Álvarez-Barcia Dr. Jan Meisner Dr. Florian Broghammer Julian Klepp Dr. Delphine Garnier Dr. Wolfgang Frey Prof. Dr. Johannes Kästner Prof. Dr. René Peters 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1515-1524
Asymmetric 1,2-additions of cyanide yield enantioenriched cyanohydrins as versatile chiral building blocks. Next to HCN, volatile organic cyanide sources are usually used. Among them, cyanoformates are more attractive on technical scale than TMSCN for cost reasons, but catalytic productivity is usually lower. Here, the development of a new strategy for cyanations is described, in which this activity disadvantage is overcome. A Lewis acidic Al center cooperates with an aprotic onium moiety within a remarkably robust bifunctional Al–F–salen complex. This allowed for unprecedented turnover numbers of up to 104. DFT studies suggest an unexpected unique trimolecular pathway in which the ammonium bound cyanide attacks the aldehyde, which itself is activated by the carbonyl group of the cyanoformate binding to the Al center. In addition, a novel practical carboxycyanation method was developed that makes use of KCN as the sole cyanide source. The use of a pyrocarbonate as carboxylating reagent provided the best results. 相似文献
87.
88.
Hesam Makki Koen N. S. Adema Elias A. J. F. Peters Jozua Laven Leendert G. J. van der Ven Rolf A. T. M. van Benthem Gijsbertus de With 《Journal of Polymer Science.Polymer Physics》2016,54(6):659-671
In this article we studied the evolution of thermomechanical properties of a polyester‐urethane coating during degradation under different degradation conditions, i.e., aerobic and anaerobic conditions with and without dry/wet cycling during degradation. Dynamic mechanical and thermal analyses show that under aerobic conditions the coatings become stiffer and more brittle in the glassy state. This stiffening is probably due to the increase in the amount of hydrogen bonding and the formation of oxidized groups which increase the polarity of the material and enhance the interactions of the polymer segments. However, oxidation reactions result in a considerable decrease in cross‐link density and stiffness in the rubbery state. Both changes, in the glassy and rubbery states, give rise to development of internal stresses. These stresses increase as the degradation process proceeds. Nevertheless, for samples exposed to anaerobic conditions, the stiffness remains constant in the glassy state and the cross‐link density slightly increases as a result of degradation. This reconfirms the dominance of the effect of oxidation reactions on the mechanical failure of the coatings. Oxygen permeation measurements show a more‐or‐less time‐independent diffusion coefficient and a gradual decrease in solubility of oxygen as a function of exposure time. This results in a slight decrease in oxygen permeation (mainly in the early stage of the degradation) as degradation proceeds. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 659–671 相似文献
89.
Edward N. Peters 《高分子科学杂志,C辑:聚合物评论》2013,53(2):173-208
The need for elastomeric polymers which will maintain their elastic properties at high temperatures has led to a wide interest in inorganic-based polymers [l]. The development of carborane-siloxane polymers in the early 1960s was a breakthrough in the search for a high-temperature elastomer. Incorporation of a carborane moiety into the siloxane backbone significantly enhanced the overall thermal stability [2]. 相似文献
90.