全文获取类型
收费全文 | 235篇 |
免费 | 12篇 |
国内免费 | 4篇 |
专业分类
化学 | 125篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 32篇 |
物理学 | 91篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 11篇 |
2011年 | 9篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 11篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1987年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1972年 | 5篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有251条查询结果,搜索用时 0 毫秒
51.
52.
53.
54.
D M Green Z A Onsan T G Forrest 《The Journal of the Acoustical Society of America》1987,81(3):692-699
Seven experiments on the detectability of intensity changes in complex multitonal acoustic spectra are reported. Two general questions organize the experimental efforts. The first question is how the detectability of a change in a flat (equal energy) spectrum depends on the frequency region where a single intensive change is made. The answer is that frequency region plays a relatively minor role. Frequency changes in the midregion of the spectrum are the easiest to hear, but thresholds increase by only about 5 dB over the range from 200 to 5000 Hz. For all frequencies, the psychometric function is of the form d' = k(delta p), where k is a constant and delta p is the change in pressure. The second question is how can we predict the detectability of complex changes over the entire frequency range from the detectability of change at each separate region. Thresholds for detecting a change from a flat spectrum to a spectrum whose amplitude varies in sinusoidal ("rippled") fashion over logarithmic frequency are measured at different frequencies of ripple. The thresholds are found to be independent of ripple frequency and are 7 dB higher than predicted on the basis of an optimum combination rule. 相似文献
55.
Wilson BJ Forrest K van Teijlingen ER McKee L Haites N Matthews E Simpson SA 《Community genetics》2004,7(1):15-24
Although family communication is important in clinical genetics only a small number of studies have specifically explored the passing on of genetic knowledge to family members. In addition, many of these present exploratory or tentative findings based upon small sample sizes, or data collected only a short time after testing. Nevertheless, if health professionals are to develop effective strategies to help patients' deal with communication issues, we need to know more about what actually happens in families. The aim of this commentary is to identify factors which appear to influence whether patients share information about genetic risk with relatives who are unaware of that risk, with whom they share it and how they go about it. The paper draws upon evidence and thinking from the disciplines of psychology (including family therapy), sociology, medicine and genetic counselling. It is presented under the following headings: disease factors, individual factors, family factors and sociocultural factors. It concludes by highlighting a number of key issues which are relevant for health professionals. 相似文献
56.
57.
We used neutron reflectivity to measure the interfacial width in the immiscible system polystyrene/poly(n‐butyl methacrylate) (PS/PnBMA). Measurements were made on the same samples at temperatures ranging from below the glass‐transition temperature (Tg) of PS to slightly above. We observed significant broadening of the interface at temperatures below the Tg of PS, indicating chain mobility below the bulk Tg value. The interfacial width exhibited a plateau at a value of 20 Å in the temperature range of 365 K < T < 377 K. A control experiment involving hydrogenated and deuterated PS films (hPS/dPS) showed no such broadening over the same temperature region. The results are consistent with a reduction of the Tg of PS in the interfacial region of ~20 K. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2664–2670, 2001 相似文献
58.
Sessler JL Aguilar A Sanchez-Garcia D Seidel D Köhler T Arp F Lynch VM 《Organic letters》2005,7(10):1887-1890
alpha,alpha-Linked oligopyrroles are attractive precursors for both expanded porphyrin and conducting polymer chemistry. We demonstrate facile methods for synthesizing quater-, penta-, and sexipyrroles from more readily available bi- and terpyrrole intermediates. These products demonstrate stability in their brightly colored oxidized forms, while reduction using borohydride reagents gives the corresponding all-pyrrole oligomers, which oxidize readily in air. The oxidized quater- and sexipyrroles were characterized by single-crystal X-ray diffraction analysis. 相似文献
59.
Slow light in semiconductor quantum wells 总被引:2,自引:0,他引:2
Ku PC Sedgwick F Chang-Hasnain CJ Palinginis P Li T Wang H Chang SW Chuang SL 《Optics letters》2004,29(19):2291-2293
We demonstrate slow light via population oscillation in semiconductor quantum-well structures for the first time. A group velocity as low as 9600 m/s is inferred from the experimentally measured dispersive characteristics. The transparency window exhibits a bandwidth as large as 2 GHz. 相似文献
60.
The paper focuses on dismissals of football managers and whether such decisions appear to contribute to organisational goals or else to be fruitless exercises in scapegoating. Its empirical setting is Argentina where incidence of sackings is more than one per season per club. It models 20 years of football match results and detects a tendency for a change of manager to be followed by deterioration in team performance, with adverse effects concentrated in results of matches played away. The evidence is consistent with decisions being driven by fan and media pressure rather than in realistic hope of improving the position of the club. 相似文献