全文获取类型
收费全文 | 219篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 144篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 48篇 |
物理学 | 31篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 3篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 13篇 |
2011年 | 15篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 18篇 |
2007年 | 16篇 |
2006年 | 7篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1974年 | 2篇 |
1969年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有230条查询结果,搜索用时 15 毫秒
91.
Bent F. Sørensen Stergios Goutianos Torben K. Jacobsen 《International Journal of Solids and Structures》2009,46(3-4):741-761
The fracture of adhesive joints between two glass-fibre laminates was studied by testing double cantilever beam test specimens loaded by uneven bending moments. A large-scale fracture process zone, consisting of a crack tip and a fibre bridging zone, developed. The mixed mode fracture resistance increased with increasing crack length, eventually reaching a steady-state level (R-curve behaviour). The steady-state fracture resistance level increased with increasing amount of tangential crack opening displacement. Cohesive laws, obtained from fracture resistance data, were used for prediction the load carrying capacity of 2-m long “medium size” adhesive joint specimens subjected to four point flexure. Medium size specimens were manufactured and tested. A good agreement was found between the predicted and measured strength values of the medium-size specimens. Thus, the scaling from small specimens to medium-size specimens was successfully achieved. 相似文献
92.
93.
Torben Maack Bisgaard 《Semigroup Forum》2002,64(2):243-264
No abstract.
June 15,1999 相似文献
94.
95.
The ionic conductivity of Li3N crystals doped with various metal ions (magnesium, copper and aluminum) or hydrogen has been investigated. The metal ions have a negative effect on the conductivity whereas hydrogen increases it. The intrinsic Li+ ionic conductivity of pure Li3N is (2·-4)×10-4Ω-1cm-1 at room temperature with an activation energy of 0.26?0.27 eV. Doping with hydrogen to a maximum level of 0.5?1.0 atom% results in a conductivity of 6×10-3Ω-1cm-1 and an activation energy which has been lowered to 0.20 eV. A model is proposed for the action of hydrogen whereby the Li-N bonds next to an NH2- group are weakened thereby facilatating the creation of Li+ Frenkel defects and the vacancy migration. Hydrogen-doped Li3N is termed an enhanced intrinsic conductor. 相似文献
96.
Torben Maack Bisgaard 《Journal of Theoretical Probability》1996,9(3):631-645
If (
j
) is a sequence of measures onR
k
having momentss
n
(
j
) of all ordersnN
0
k
and if for eachnN
0
k
the sequence (s
n
j
))
jN
converges to somet
n
R then some subsequence of (
j
) converges weakly to a measure with moments of all orders satisfyings
n
()=t
n
for allnN0/k
. Thisindeterminate method of moments and the continuity theorems in probability theory suggest a common generalization, dealing with a commutative semigroupS, with involution and a neutral element, and measures on the dual semigroupS
* ofcharacters on S—hermitian multiplicative complex functions not identically zero. In this setting, a continuity theorem holds for measures on the set of bounded characters,(2) and an indeterminate method of moments whenS is finitely generated.(2) The latter result is generalized in the present paper to the case of arbitraryS. This leads to a generalization of Haviland's criterion for theK-moment problem, and to a continuity theorem for the so-called perfect semigroups. 相似文献
97.
Erik Nørby Svendsen Torben Stroyer-Hansen Hendrik F. Hameka 《Chemical physics letters》1978,54(2):217-219
We calculate the various components of the third-order nonlinear electric susceptibility of the benzene molecule, starting from a CNDO wavefunction. Our theoretical result for the space-fixed nonlinear third-order susceptibility is 6.15 × 10?36 esu, the corresponding experimental value is 1.58 × 10?36 esu. We also estimate the contributions from the σ and π electrons to the total susceptibility. 相似文献
98.
I.-M. Stender N. Bech-Thomsen T. Poulsen H. C. Wulf 《Photochemistry and photobiology》1997,66(4):493-496
Abstract— Photodynamic therapy (PDT) with topical application of 8-aminolevulinic acid (ALA) followed by irradiation with visible light (ALA-PDT) is a relatively new and promising experimental treatment of superficial premalignant and malignant skin neoplasms. The purpose of this study was to determine whether ALA-PDT can prevent photocarcinogenesis in hairless mice exposed to solar UV. A total of 140 mice was divided into seven groups of 20 mice each. Group 1: solar-UV exposure. Group 2: solar UV and a cream base + visible light once a week. Group 3: solar UV and ALA-PDT once a week. Group 4: solar UV and ALA-PDT once every second week. Group 5: solar UV and ALA-PDT every fourth week. Group 6: ALA-PDT once a week. Group 7: no treatment. The time to first and to second tumor 1 mm was registered. Predefined endpoints, such as one tumor a 4 mm or an area of small confluent tumors on the back of the mice were criteria for withdrawal from the experiment. The time to first and to second tumor was significantly longer in the ALA-PDT-treated mice than in mice only exposed to solar UV and solar-UV/cream base-visible light (P < 0.005). However, we observed an increased death and accident rate in the ALA-PDT-treated groups compared to the groups not treated with ALA-PDT (chi-square test, P = 0.0250). Significantly more ALA-PDT-treated mice were withdrawn because of a tumor 4 mm ( P = 0.0005). The UV unexposed mice developed no tumors. Repetitive treatments with ALA-PDT delay photoinduced carcinogenesis in mice. 相似文献
99.
Solistatinol, a novel phenolic compactin analogue, has been isolated from Penicillium solitum using a UV-guided strategy. The structure and relative stereochemistry were determined by NMR spectroscopy and mass spectrometry. The absolute stereochemistry was determined by chemical degradation and comparison of CD data with literature data. 相似文献
100.
Hensel V Godt A Popovitz-Biro R Cohen H Jensen TR Kjaer K Weissbuch I Lifshitz E Lahav M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(6):1413-1423
Composite materials of quantum particles (Q-particles) arranged in layers within crystalline powders of pi-conjugated, rodlike dicarboxylic acids are reported. The synthesis of the composites, either as three-dimensional crystals or as thin films at the air-water interface, comprises a two-step process: 1) The preparation of the Cd salts 6 (Cd), 8 (Cd) or Pb salts 6 (Pb), 8 (Pb) of the oligo(p-phenyleneethynylene)dicarboxylic acids 6 (H), 8 (H), in which the metal ions are arranged in ribbons and are separated by the long axis of the organic molecules, as demonstrated by X-ray powder diffraction analysis of the solids and grazing incidence X-ray diffraction analysis of the films on water. 2) Topotactic solid/gas reaction of these salts with H(2)S to convert the metal ions into Q-particles of CdS or PbS embedded in the organic matrix that consists of the acids 6 (H) and 8 (H). These hybrid materials have been characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. 相似文献