全文获取类型
收费全文 | 160篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 105篇 |
晶体学 | 8篇 |
力学 | 6篇 |
数学 | 13篇 |
物理学 | 31篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2013年 | 13篇 |
2012年 | 14篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 10篇 |
2007年 | 13篇 |
2006年 | 5篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 3篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有163条查询结果,搜索用时 31 毫秒
51.
Choi KY Matsuda YH Nojiri H Kortz U Hussain F Stowe AC Ramsey C Dalal NS 《Physical review letters》2006,96(10):107202
We report pulsed field magnetization and ESR experiments on a {Cu3} nanomagnet, where antiferromagnetically coupled Cu(2+) (S = 1/2) ions form a slightly distorted triangle. The remarkable feature is the observation of a half step magnetization, hysteresis loops, and an asymmetric magnetization between a positive and a negative field in a fast sweeping external field. This is attributed to an adiabatic change of magnetization. The energy levels determined by ESR unveil that the different mixing nature of a spin chirality of a total S = 1/2 Kramers doublet by virtue of Dzyaloshinskii-Moriya interactions is decisive for inducing half step magnetization. 相似文献
52.
The rate of fracture of Nitinol stents in the superficial femoral artery (SFA) is higher than desirable. Development of more
fracture-resistant stents requires a better understanding of in-vivo loads, how stents deform under these loads, and the influence of the artery on stent deformation. In the work reported here,
testing devices were designed and constructed to measure loads in stents undergoing tensile, bending, and torsional deformations.
Tests to measure mechanical stiffnesses were performed on stents, mock arteries, and stents emplaced in mock arteries. Significant
stent/artery interaction was observed under tension and bending; little interaction occurred under torsion loads. The results
are explained by changes in stent geometry under load. The deformation, load, and stent/artery interaction information will
be useful in validating finite element codes for designing and analyzing stents. 相似文献
53.
Winfried Wendelin Edith Gößnitzer Dalal Abou El Ella 《Monatshefte für Chemie / Chemical Monthly》2000,131(4):353-374
Summary. The cyclization reactions of trans-3a-hexahydro-2-benzimidazolamine with 2-alkylidene- and 2-benzylidenecyclohexanones and α-tetralones, respectively, yield
mixtures of two isomeric condensates each. Thorough high resolution NMR analyses (1H and 13C NMR, HH-COSY, gs-HSQC, gs-HMBC, 1D TOCSY, and 1D NOE difference spectra) revealed that the corresponding isomers are in all cases linearly fused diastereomeric
12α- and 12β-substituted trans-6aα-dodecahydrobenzimidazo[2,1-b]quinazolines and 7α-substituted trans-8aβ- and trans-8aα-decahydrobenzimidazo[2,1-b]benzo[h]quinazolines, respectively. The formation of corresponding angularly fused regioisomers was not observed so far. The stereochemistry
and the tautomerism of some bases and their hydrochlorides as well as the regiospecific course of the cyclization reactions
are discussed. Biological tests showed that the novel compounds don’t exert remarkable antibacterial and antimycotic effects.
Received November 3, 1999. Accepted November 30, 1999 相似文献
54.
55.
56.
57.
Several types of paramagnetic centers have been detected in the room temperature irradiated KH2PO4, KD2PO4, KH2PO4KH2AsO4, KD2PO4KD2AsO4 and in the newly discovered ferroelectric NaTh2(PO4)3. Comparative studies of temperature dependence in the EPR spectra show that as in KH2PO4-type crystals, the ferroelectric phase transition in NaTh2(PO4)3 crystals also seems to be related to the motion of the PO4 units. The results help to clarify some earlier observed anomalies on the effects of γ-irradiation on dielectric properties of KH2PO4 and in particular, show that the extent of the damage can be controlled by changing the impurity content of the unirradiated samples. 相似文献
58.
Cage B Cotton FA Dalal NS Hillard EA Rakvin B Ramsey CM 《Journal of the American Chemical Society》2003,125(18):5270-5271
Cu3(O2C16H23)6.1.2C6H12, containing a Cu36+ core in an equilateral triangle geometry, has been found to be a versatile model system for investigating the spin-frustration phenomenon in a triangular lattice. It affords well-resolved EPR spectra from both of the two possible (Stotal = 1/2 and 3/2) spin states of the Cu36+ core. From 295 to 100 K, the spectra consist of a triplet, but with the central line overlapped by an additional, sharp peak, which replaces the triplet at 30 K and below. The triplet was thus assigned to the excited state with Stotal = 3/2, located at 324 +/- 5 K ( approximately 225 cm-1), with the zero-field parameters D = -535 G, E = 0, g parallel = 2.209 and g perpendicular = 2.057. The singlet was attributed to the Stotal = 1/2 state, with gxx = 2.005, gyy = 2.050, gzz = 2.282, and, surprisingly, a hyperfine splitting arising from a single Cu2+ nucleus, with Azz = 157 G. The detailed magnetic measurements on a three-electron, equilateral triangular system, and the observation of symmetry lowering in the doublet ground state, should be of broad theoretical and experimental interest in molecular magnetism. 相似文献
59.
Bi LH Kortz U Nellutla S Stowe AC van Tol J Dalal NS Keita B Nadjo L 《Inorganic chemistry》2005,44(4):896-903
The iron(III)-substituted tungstogermanate [Fe6(OH)3(A-alpha-GeWO34(OH)3)2]11- (1) has been synthesized and characterized by IR, elemental analysis, SQUID magnetometry, electron paramagnetic resonance (EPR), and electrochemistry. Single-crystal X-ray analysis was carried out on Cs4Na7[Fe6(OH)3(A-alpha-GeW9O34(OH)3)2] x 30H2O, which crystallizes in the monoclinic system, space group C2/m, with a = 36.981(4) A, b = 16.5759(15) A, c = 16.0678(15) A, beta = 95.311(3) degrees, and Z = 4. Polyanion 1 consists of two (A-alpha-GeW9O34) Keggin moieties linked via six Fe3+ ions, leading to a double-sandwich structure. The equivalent iron centers represent a trigonal prismatic Fe6 fragment, resulting in virtual D3h symmetry for 1. Electrochemistry studies revealed that 1 is stable in solution from pH 3 to at least pH 7. In pH = 3 media the reduction of the six Fe3+ centers was featured by a single voltammetric wave for most supporting electrolytes used. In that case, whatever the scan rate from 1000 mV x s(-1) down to 2 mV x s(-1), no splitting of the single Fe-wave of 1 was observed. The acetate medium induced a partial splitting of the wave, and this separation is enhanced with increasing pH. Remarkable efficiency of 1 in the electrocatalytic reduction of nitrite, nitric oxide, and nitrate is demonstrated. Magnetic susceptibility (chi) measurements indicate a diamagnetic (S(T) = 0) ground state, with an average J = -12 cm(-1) and g = 2.00. EPR studies confirm that the ground state is indeed diamagnetic, since the EPR signal intensity steadily decreases without any line broadening as the temperature is lowered and becomes unobservable below about 50 K. The signal is a single broad peak at all frequencies (90-370 GHz), ascribed to the thermally accessible excited states. Its g(iso) is 1.992 51, as expected for a high-spin Fe3+-containing species, and supports the chi data analysis. 相似文献
60.
Conformational switching of the prion protein into the abnormal form involves the formation of (obligatory) molten‐oligomers that mature into ordered amyloid fibrils. The role of water in directing the course of amyloid formation remains poorly understood. Here, we show that the mobility of the water molecules within the on‐pathway oligomers is highly retarded. The water relaxation time within the oligomers was estimated to be ≈1 ns which is about three orders of magnitude slower than the bulk water and resembles the characteristics of (trapped) nano‐confined water. We propose that the coalescence of these obligatory oligomers containing trapped water is entropically favored because of the release of ordered water molecules in the bulk milieu and results in the sequestration of favorable inter‐chain amyloid contacts via nucleated conformational conversion. The dynamic role of water in protein aggregation will have much broader implications in a variety of protein misfolding diseases. 相似文献