全文获取类型
收费全文 | 731篇 |
免费 | 12篇 |
专业分类
化学 | 438篇 |
晶体学 | 4篇 |
力学 | 61篇 |
数学 | 54篇 |
物理学 | 186篇 |
出版年
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2017年 | 4篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 9篇 |
2013年 | 26篇 |
2012年 | 26篇 |
2011年 | 33篇 |
2010年 | 15篇 |
2009年 | 13篇 |
2008年 | 29篇 |
2007年 | 44篇 |
2006年 | 31篇 |
2005年 | 35篇 |
2004年 | 24篇 |
2003年 | 20篇 |
2002年 | 30篇 |
2001年 | 15篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 4篇 |
1997年 | 8篇 |
1996年 | 14篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 23篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 14篇 |
1973年 | 9篇 |
1972年 | 12篇 |
1971年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有743条查询结果,搜索用时 15 毫秒
81.
Challinor VL Hayes PY Bernhardt PV Kitching W Lehmann RP De Voss JJ 《The Journal of organic chemistry》2011,76(17):7275-7280
The absolute stereochemistry of the steroidal saponins bethosides B and C was previously assigned as (22R,25R) on the basis of work that employed Horeau's method. Our studies of helosides A and B created doubt about both the original assignment and consequently our conclusion that relied upon it. The absolute configurations of bethosides B and C are revised to (22S,25R) following X-ray crystallographic analysis of their aglycone. Synthesis and full spectral characterization of both the 22R and 22S aglycones is reported to facilitate future stereochemical assignments in this series of saponins. 相似文献
82.
The bulk structure of the two oldest ionic liquids (ILs), ethylammonium nitrate (EAN) and ethanolammonium nitrate (EtAN), is elucidated using neutron diffraction. The spectra were modelled using empirical potential structure refinement (EPSR). The results demonstrate that EAN exhibits a long-range structure of solvophobic origin, similar to a bicontinuous microemulsion or disordered L(3)-sponge phase, but with a domain size of only 1 nm. The alcohol (-OH) moiety in EtAN interferes with solvophobic association between cation alkyl chains resulting in small clusters of ions, rather than an extended network. 相似文献
83.
Atkin R Borisenko N Drüschler M el-Abedin SZ Endres F Hayes R Huber B Roling B 《Physical chemistry chemical physics : PCCP》2011,13(15):6849-6857
The structure and dynamics of the interfacial layers between the extremely pure air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and Au(111) has been investigated using in situ scanning tunneling microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy measurements. The in situ scanning tunnelling microscopy measurements reveal that the Au(111) surface undergoes a reconstruction, and at -1.2 V versus Pt quasi-reference the famous (22 × √3) herringbone superstructure is probed. Atomic force microscopy measurements show that multiple ion pair layers are present at the ionic liquid/Au interface which are dependent on the electrode potential. Upon applying cathodic electrode potentials, stronger ionic liquid near surface structure is detected: both the number of near surface layers and the force required to rupture these layers increases. The electrochemical impedance spectroscopy results reveal that three distinct processes take place at the interface. The fastest process is capacitive in its low-frequency limit and is identified with electrochemical double layer formation. The differential electrochemical double layer capacitance exhibits a local maximum at -0.2 V versus Pt quasi-reference, which is most likely caused by changes in the orientation of cations in the innermost layer. In the potential range between -0.84 V and -1.04 V, a second capacitive process is observed which is slower than electrochemical double layer formation. This process seems to be related to the herringbone reconstruction. In the frequency range below 1 Hz, the onset of an ultraslow faradaic process is found. This process becomes faster when the electrode potential is shifted to more negative potentials. 相似文献
84.
The microscopic and macroscopic versions of fluid mechanics differ qualitatively. Microscopic particles obey time-reversible ordinary differential equations. The resulting particle trajectories {q(t)} may be time-averaged or ensemble-averaged so as to generate field quantities corresponding to macroscopic variables. On the other hand, the macroscopic continuum fields described by fluid mechanics follow irreversible partial differential equations. Smooth particle methods bridge the gap separating these two views of fluids by solving the macroscopic field equations with particle dynamics that resemble molecular dynamics. Recently, nonlinear dynamics have provided some useful tools for understanding the relationship between the microscopic and macroscopic points of view. Chaos and fractals play key roles in this new understanding. Non-equilibrium phase-space averages look very different from their equilibrium counterparts. Away from equilibrium the smooth phase-space distributions are replaced by fractional-dimensional singular distributions that exhibit time irreversibility. 相似文献
85.
M. Hayes 《Journal of Elasticity》1997,49(3):285-288
A simple direct proof is given of the known result that in any deformation x = x(X), the planes of the central circular sections
of the material strain-ellipsoid at X are deformed into the planes of the spatial strain-ellipsoid at x.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
86.
87.
K.H. Chow Th. Jestädt S.J. Blundell S.R. Dunsiger W. Hayes B. Hitti M.A. Green R.F. Kiefl J.E. Millburn P.A. Pattenden F.L. Pratt M.J. Rosseinsky 《Hyperfine Interactions》1997,104(1-4):55-60
We report μSR measurements on a series of compounds with composition La2-xSrxNiO4+\delta where the net hole concentration x+2\delta is greater than 0.4. A magnetic transition is found in all the samples studied
which occurs at a composition‐dependent temperature TM. Below TM, clear precession signals are observed in zero applied magnetic field. The possible muon sites are discussed within the context
of dipole‐field calculations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
89.
David R. Hayes 《Inventiones Mathematicae》1988,94(3):505-527
Partially supported by NSF grant DMS-8702716 相似文献
90.