全文获取类型
收费全文 | 251篇 |
免费 | 18篇 |
国内免费 | 12篇 |
专业分类
化学 | 72篇 |
晶体学 | 3篇 |
数学 | 29篇 |
物理学 | 177篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 12篇 |
2012年 | 4篇 |
2011年 | 15篇 |
2010年 | 7篇 |
2009年 | 14篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 15篇 |
2005年 | 16篇 |
2004年 | 11篇 |
2003年 | 11篇 |
2002年 | 16篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有281条查询结果,搜索用时 328 毫秒
1.
Electronic properties of model quantum-dot structures in zero and finite magnetic fields 总被引:1,自引:0,他引:1
H. Saarikoski E. Räsänen S. Siljamäki A. Harju M.J. Puska R.M. Nieminen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(2):241-252
We have computed electronic structures and total energies of circularly confined two-dimensional quantum dots and their lateral
dimers in zero and finite uniform external magnetic fields using different theoretical schemes: the spin-density-functional
theory (SDFT), the current-and-spin-density-functional theory (CSDFT), and the variational quantum Monte Carlo (VMC) method.
The SDFT and CSDFT calculations employ a recently-developed, symmetry-unrestricted real-space algorithm allowing solutions
which break the spin symmetry. Results obtained for a six-electron dot in the weak confinement limit and in zero magnetic
field as well as in a moderate confinement and in finite magnetic fields enable us to draw conclusions about the reliability
of the more approximative SDFT and CSDFT schemes in comparison with the VMC method. The same is true for results obtained
for the two-electron quantum dot dimer as a function of inter-dot distance. The structure and role of the symmetry-breaking
solutions appearing in the SDFT and CSDFT calculations for the above systems are discussed.
Received 16 October 2001 and Received in final form 17 January 2002 相似文献
2.
Direct Antisite Formation in Electron Irradiation of GaAs 总被引:1,自引:0,他引:1
3.
4.
H. E. Hansen R. Talja H. Rajainmäki H. K. Nielsen B. Nielsen R. M. Nieminen 《Applied Physics A: Materials Science & Processing》1985,36(2):81-92
Molybdenum single crystals are irradiated at 20 K with 6 MeV protons. The radiation damage and lattice defect annealing is studied by positron lifetime spectroscopy in the temperature range from 15 to 720 K. Loss of vacancies due to recombination with mobile interstitials is observed at 40 K (Stage I) in agreement with resistivity measurements. This is the first time Stage I is observed by positrons below 77 K. The implanted hydrogen decorates the vacancies around 100 K, which is consistent with a hydrogen migration energy in molybdenum:E
M
H
= 0.3–0.4 eV. Clustering of spatially correlated vacancies takes place in a wide temperature region below the usual vacancy clustering stage (Stage III). Stage III is observed at rather low temperatures (400–480 K) due to the very high vacancy concentration. Hydrogen bound to vacancies and vacancy clusters is released above 540 K, which puts an upper limit to the hydrogen binding energy:E
B
H
1.4 eV. The present work emphasizes the advantage of employing a vacancy sensitive technique to study hydrogen in metals, where its intrinsic solubility is low. In such metals (as molybdenum) both the effective solubility and the effective mobility of hydrogen are strongly influenced by the presence of vacancies. 相似文献
5.
Foster AS Gal AY Nieminen RM Shluger AL 《The journal of physical chemistry. B》2005,109(10):4554-4560
In this work, we use first principles simulations to provide features of the dynamic scanning force microscopy imaging of adsorbed organic layers on insulating surfaces. We consider monolayers of formic (HCOOH) and acetic (CH(3)COOH) acid and a mixed layer of acetic and trifluoroacetic acids (CF(3)COOH) on the TiO(2)(110) surface and study their interaction with a silicon dangling bond tip. The results demonstrate that the silicon tip interacts more strongly with the substrate and the COO(-) group than the adsorbed acid headgroups, and, therefore, molecules would appear dark in images. The pattern of contrast and apparent height of molecules is determined by the repulsion between the tip and the molecular headgroups and by significant deformation of the monolayer and individual molecules. The height of the molecule on the surface and the size of the headgroup play a large role in determining access of the tip to the substrate and, hence, the contrast in images. Direct imaging of the molecules themselves could be obtained by providing a functionalized tip with attraction to the molecular headgroups, for example, a positive potential tip. 相似文献
6.
7.
8.
膜的动电特性研究中,往往采用流动电位方法。该方法中,Ag-Ag Cl测试电极的质量是影响测试准确性的关键要素。本文采用正交试验设计和方差分析,着重考察电解法制备Ag-Ag Cl电极过程中,电流强度(I)、氯化时间(t)、电解质溶液浓度(CHCl)、电极来源(n)、烘烤温度(T)、活化电极溶液浓度(CKCl)等因素对Ag-Ag Cl电极稳定性的影响。得到Ag-Ag Cl电极的最优制备参数为:电流密度3.0m A/cm2,氯化时间50min,盐酸浓度0.1mol·L-1,烘烤温度120℃,活化电极溶液(KCl)浓度0.001mol·L-1;最显著影响因素为电极来源,显著影响因素为氯化时间和烘烤温度。对最优条件组合下制备的AgAg Cl电极,进行了稳定性实验,结果表明:制备的电极具有较好的稳定性,24h内电极电位漂移量小于0.10mv,7天内电极电位漂移量小于0.2mv;在聚偏氟乙烯中空纤维超滤膜流动电位测试中,流动电位与流动压差具有良好的线性和可重复性,回归曲线R20.99,变化规律符合Helmholtz-Smoluehowski公式,可以较好满足膜的流动电位测试要求。 相似文献
9.
Annihilation characteristics are calculated for positrons trapped in clean and impurity decorated vacancy clusters in Au. The positron lifetime depends strongly on the structure of the clusters. In a strongly relaxed vacancy cluster, the lifetime can become smaller than the lifetime in a single vacancy. The substitution of some neighbour atoms of a vacancy cluster by Fe atoms has only a minor effect on the positron lifetimes. 相似文献
10.
Katarina Dimic-Misic Antti Puisto Patrick Gane Kaarlo Nieminen Mikko Alava Jouni Paltakari Thaddeus Maloney 《Cellulose (London, England)》2013,20(6):2847-2861
The influence of swelling on the rheological and dewatering properties of high consistency nanocellulose based furnishes is considered. Different consistencies of suspensions (1–4 %) and furnishes (5–15 %) were prepared made of two distinctly different grades of nanocellulose containing, micro fibrillated (MFC) and nanofibrillated (NFC) cellulose, and systematic comparison between the rheological and dewatering parameters was conducted. The characterization of the rheological and dewatering properties was performed with a stress controlled rheometer combined with an immobilization cell in parallel plate geometry, as well as with an independent gravimetric dewatering device. The surface charge of nanofibrillated cellulose was found to influence the rheological and dewatering properties of the evaluated suspensions and furnishes due to its impact on swelling and effectively bound water. Due to the complex behavior of the novel materials, the immobilization times were difficult to determine from the changes in the damping factor, as often used for coating colors. Instead, we propose a modified method for determination of immobilization times based on a rheological analysis adopting the rate of change in viscoelastic loss factor over time, d(tan δ = G′′/G′)/dt, describing the critical point(s) in the ratio of the viscous to elastic stress response moduli. With this approach we show that it is possible to characterize immobilization of these materials incorporating the concept of the combined physical interactions of the components and the non-removable bound water, without requiring a direct measure of the nanocellulose surface swelling. Based on the results, we hypothesize that fibrillar swelling impacts the dewatering of MFC and NFC suspensions, and furnishes containing them, by an interfiber pore connectivity blocking/sealing mechanism, which effectively defines the immobilization of the material matrix at the end point of free water extraction caused by the physical blocking imposed by the remaining bound water. 相似文献