全文获取类型
收费全文 | 574篇 |
免费 | 9篇 |
专业分类
化学 | 304篇 |
晶体学 | 12篇 |
力学 | 12篇 |
数学 | 86篇 |
物理学 | 169篇 |
出版年
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 15篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 21篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 6篇 |
2003年 | 14篇 |
2002年 | 12篇 |
2001年 | 18篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 8篇 |
1997年 | 13篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1978年 | 8篇 |
1968年 | 5篇 |
1966年 | 5篇 |
1933年 | 5篇 |
1932年 | 6篇 |
1930年 | 7篇 |
1929年 | 6篇 |
1927年 | 8篇 |
1926年 | 4篇 |
1925年 | 7篇 |
1924年 | 10篇 |
1923年 | 8篇 |
1913年 | 4篇 |
排序方式: 共有583条查询结果,搜索用时 0 毫秒
141.
142.
A critical task for organizations is how to best structure themselves to efficiently allocate information and resources to individuals tasked with solving sub-components of the organization’s central problems. Despite this criticality, the processes by which organizational structures form remain largely opaque within organizational theory, with most approaches focused on how structure is influenced by individual managerial heuristics, normative cultural perceptions, and trial-and-error. Here, we propose that a broad understanding of organizational formation can be aided by appealing to generative entrenchment, a theory from developmental biology that helps explain why phylogenetically diverse animals appear similar as embryos. Drawing inferences from generative entrenchment and applying it to organizational differentiation, we argue that the reason many organizations appear structurally similar is due to core informational restraints on individual actors beginning at the top and descending to the bottom of these informational hierarchies, which reinforces these structures via feedback between separate levels. We further argue that such processes can lead to the emergence of a variety of group-level traits, an important but undertheorized class of phenomena in cultural evolution. 相似文献
143.
R. N. Moser 《Journal of Radioanalytical and Nuclear Chemistry》1993,173(2):283-292
Lead-210 is often used to date recent (100 y) environmental samples. Three different methods for its determination are compared:210Pb -counting with a low level proportional counter,210Pb -spectroscopy and210Po -spectroscopy. Agreement within analytical errors was found for the three methods in two sediment cores from Lake Zurich, Switzerland and in IAEA SD-A-1 deep sea reference material. For210Po -spectroscopy, the detection and determination limit is an order of magnitude lower than these for the other methods. Methods for the determination of226Ra are also discussed. Measurements on low level proportional counters are difficult to interpret and not suitable for routine work. A better way to measure226Ra is -spectroscopy of colloidal Ba(Ra)SO4. 相似文献
144.
Moser C Orthaber A Nieger M Belaj F Pietschnig R 《Dalton transactions (Cambridge, England : 2003)》2006,(32):3879-3885
A facile synthetic access to the homologous series of 1,1'-ferrocenylene bisdihalophosphanes Fc'(PX2)2 (X = F, Cl, Br, I; Fc' = 1,1'-ferrocenediyl = ferrocenylene = -C5H4FeC5H4-) is reported. The 31P NMR spectroscopic data of this series suggest a similar electronic interaction of the -PX(2) unit with the ferrocene system as in monofunctional ferrocenyldihalophosphanes. Crystal structures for Fc'(PCl2)2 and Fc'(PBr2)2 reveal that the nature of the halogen atom within the phosphane unit strongly influences the twist angle of the ferrocene system, while leaving the other structural parameters mostly unaffected. Based on these bisdihalophosphanes, a synthetic access to the first metallocene bridged bisphosphaalkene ((C5H4P=C(t-Bu)OTMS)2Fe) is reported in which the tert-butyl substituents provide sufficient steric pressure to control the E/Z isomeric ratio which leads to the almost exclusive formation of the most stable Z,Z isomer out of the three possible isomers. 相似文献
145.
S. Siles G. Moya X. H. Li J. Kansy P. Moser 《Journal of Radioanalytical and Nuclear Chemistry》1999,240(2):529-530
Lifetime measurement in Positron Annihilation Spectroscopy (PAS) is applied to the study of free-volume collagen characteristics
as a function of concentration. The lifetimes of positrons were measured by a conventional fast-fast coincidence system. All
lifetime data are fitted in three components by using the computer program POSITRON-FIT and resolved. For each concentration,
lifetime distributions were analyzed in order to obtain the different components, thus we have observed three components of
which one long component τ3. This long lived component can be associated with a pick-off annihilation of ortho-positronium (o-Ps) trapped in free volumes
of amorphous region. This investigation shows the potential of positron annihilation spectroscopy in the study of biopolymer
microstructures. 相似文献
146.
147.
The known Euler–Lagrange equation for (intrinsic) biharmonic maps is unsuitable for the study of some of the critical points of the corresponding functional, as it requires too much regularity. We derive and discuss a variant of the equation that does not have this shortcoming. 相似文献
148.
149.
M. Moser D. Klimm S. Ganschow A. Kwasniewski K. Jacobs 《Crystal Research and Technology》2008,43(4):350-354
The quasi‐binary phase diagram lithium oxide – molybdenum(VI) oxide was investigated by differential scanning calorimetry and X‐ray diffraction. The four intermediate phases Li4MoO5, Li2MoO4, Li4Mo5O17, and Li2Mo4O13 show incongruent melting. The system has one eutectic point at 50.5 mol% MoO3 and 49.5 mol% LiO0.5 with a eutectic temperature of 524.6°C. At this point the melt is in equilibrium with Li2MoO4 and Li4Mo5O17. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献