全文获取类型
收费全文 | 133篇 |
免费 | 3篇 |
专业分类
化学 | 93篇 |
力学 | 2篇 |
数学 | 1篇 |
物理学 | 40篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2013年 | 3篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1933年 | 2篇 |
1931年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 31 毫秒
71.
We provide a direct demonstration that nonhuman primates spontaneously perceive changes in formant frequencies in their own species-typical vocalizations, without training or reinforcement. Formants are vocal tract resonances leading to distinctive spectral prominences in the vocal signal, and provide the acoustic determinant of many key phonetic distinctions in human languages. We developed algorithms for manipulating formants in rhesus macaque calls. Using the resulting computer-manipulated calls in a habituation/dishabituation paradigm, with blind video scoring, we show that rhesus macaques spontaneously respond to a change in formant frequencies within the normal macaque vocal range. Lack of dishabituation to a "synthetic replica" signal demonstrates that dishabituation was not due to an artificial quality of synthetic calls, but to the formant shift itself. These results indicate that formant perception, a significant component of human voice and speech perception, is a perceptual ability shared with other primates. 相似文献
72.
73.
Although the mammalian larynx exhibits little structural variation compared to sound-producing organs in other taxa (birds or insects), there are some morphological features which could lead to significant differences in acoustic functioning, such as air sacs and vocal membranes. The vocal membrane (or "vocal lip") is a thin upward extension of the vocal fold that is present in many bat and primate species. The vocal membrane was modeled as an additional geometrical element in a two-mass model of the larynx. It was found that vocal membranes of an optimal angle and length can substantially lower the subglottal pressure at which phonation is supported, thus increasing vocal efficiency, and that this effect is most pronounced at high frequencies. The implications of this finding are discussed for animals such as bats and primates which are able to produce loud, high-pitched calls. Modeling efforts such as this provide guidance for future empirical investigations of vocal membrane structure and function, can provide insight into the mechanisms of animal communication, and could potentially lead to better understanding of human clinical disorders such as sulcus vocalis. 相似文献
74.
75.
Kenneth D. Knudsen Philip Pattison Andrew N. Fitch Robert J. Cernik 《Angewandte Chemie (International ed. in English)》1998,37(17):2340-2343
Without any prior knowledge of the molecular structure , all 31 carbon and oxygen atoms of fluorescein diacetate were accurately located based on a high-resolution powder diffraction experiment. Direct methods and Fourier recycling were used. This represents a considerable advance with respect to the size of an organic molecule whose structure can be solved by ab initio methods from measurements on a powder. 相似文献
76.
P. Schobinger-Papamantellos J. Rodríguez-Carvajal K. H. J. Buschow E. Dooryhee A. N. Fitch 《Journal of magnetism and magnetic materials》2000,210(1-3)
High-quality powder XRD data of the compound ErFe4Ge2 collected in the ESRF beam line BM16, are presented for the entire magnetically ordered regime (TN=44 K). The data analysis reveals the occurrence of a double symmetry breaking at the magnetic transition. This experiment has allowed us to distinguish between structural and magnetic satellites, both present in the neutron patterns, and to demonstrate the interdependence of structural and magnetic transitions. The high-temperature (HT) phase disproportionates by a first-order transition into two distinct phases: P42/mnm (Tc, TN=44 K)→Cmmm (majority LT phase)+Pnnm (minority IT Phase) which coexist in proportions varying with temperature down to 4 K. The phase diagram comprises three temperature regions: (a) the HT range with T>TN for the tetragonal P42/mnm phase; (b) the IT (intermediate temperature) range, 20 K<T<TN, where the two phases coexist in strongly variable proportions and the Pnnm phase reaches its highest concentration (≈31%) around 30 K and (c) the LT (low temperature) range, 1.5–20 K, where the Cmmm phase is dominating (up to 95%). We suggests that this phenomenon is the result of competing magneto-elastic mechanisms involving the Er crystal field anisotropy, the Er–Er, Er–Fe and the Fe–Fe exchange interactions and their coupling with the lattice strains. 相似文献
77.
K. Kellermann O. Schließmann G. Scheibe F. Twyman A. A. Fitch A. Harvey G. Haidhausen F. Waibel und O. Findeisen 《Fresenius' Journal of Analytical Chemistry》1933,94(5-6):196-201
Ohne Zusammenfassung 相似文献
78.
Experimental Mechanics - Our research objective was to obtain a fundamental understanding of how ITO thin films layered on flexible polyethylene terephthalate (PET) substrates fail due to tensile,... 相似文献
79.
Abstract Detector systems introduce distortions into acquired data. To obtain accurate angle and intensity information, it is necessary to calibrate, and apply corrections. Intensity non-linearity, spatial distortion, and non-uniformity of intensity response, are the primary considerations. It is better to account for the distortions within scientific analysis software, but often it is more practical to correct the distortions to produce ‘idealised’ data. Calibration methods and software have been developed for single crystal diffraction experiments, using both approaches. For powder diffraction experiments the additional task of converting a two-dimensional image to a one-dimensional spectrum is used to allow Rietveld analysis. This task may be combined with distortion correction to produce intensity information and error estimates. High-pressure experiments can introduce additional complications and place new demands on software. Flexibility is needed to be able to integrate different angular regions separately, and to produce profiles as a function of angle of azimuth. Methods to cope with awkward data are described, and examples of the techniques applied to data from high pressure experiments are presented. 相似文献
80.
Erra L Tedesco C Cipolletti VR Annunziata L Gaeta C Brunelli M Fitch AN Knöfel C Llewellyn PL Atwood JL Neri P 《Physical chemistry chemical physics : PCCP》2012,14(1):311-317
The adsorption properties of a new nanoporous organic zeolite with respect to acetylene and Ar were studied by volumetric adsorption analysis, microcalorimetric experiments, and synchrotron high-resolution X-ray powder diffraction. This allowed us to locate the guest molecules inside the host channels and characterize the host-guest interactions. 相似文献