全文获取类型
收费全文 | 9727篇 |
免费 | 269篇 |
国内免费 | 63篇 |
专业分类
化学 | 6522篇 |
晶体学 | 83篇 |
力学 | 260篇 |
数学 | 1101篇 |
物理学 | 2093篇 |
出版年
2022年 | 115篇 |
2021年 | 133篇 |
2020年 | 160篇 |
2019年 | 139篇 |
2018年 | 123篇 |
2017年 | 85篇 |
2016年 | 241篇 |
2015年 | 195篇 |
2014年 | 239篇 |
2013年 | 455篇 |
2012年 | 499篇 |
2011年 | 624篇 |
2010年 | 310篇 |
2009年 | 269篇 |
2008年 | 499篇 |
2007年 | 491篇 |
2006年 | 469篇 |
2005年 | 441篇 |
2004年 | 364篇 |
2003年 | 366篇 |
2002年 | 320篇 |
2001年 | 185篇 |
2000年 | 208篇 |
1999年 | 117篇 |
1998年 | 95篇 |
1997年 | 107篇 |
1996年 | 172篇 |
1995年 | 120篇 |
1994年 | 91篇 |
1993年 | 119篇 |
1992年 | 117篇 |
1991年 | 107篇 |
1990年 | 95篇 |
1989年 | 80篇 |
1988年 | 111篇 |
1987年 | 86篇 |
1986年 | 88篇 |
1985年 | 114篇 |
1984年 | 105篇 |
1983年 | 67篇 |
1982年 | 102篇 |
1981年 | 97篇 |
1980年 | 88篇 |
1979年 | 102篇 |
1978年 | 80篇 |
1977年 | 98篇 |
1976年 | 79篇 |
1975年 | 81篇 |
1974年 | 82篇 |
1973年 | 84篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Healthcare Operational Research (OR) has had limited success in achieving a sufficient level of stakeholder acceptance to lead to implementation of results. This research study is aimed at combining OR methodologies to achieve greater acceptance of results for organizational change. Patient flow delays in the Paediatric intensive care unit (PICU) at Children's Hospital of Wisconsin were identified using case studies. Patient flow was modelled using hard OR (simulation) using case study findings, with active stakeholder participation, and enhanced with outcomes research. Outcomes research allowed achieving greater clinical relevance of OR findings. Results from hard OR, particularly for politically sensitive issues, were persuasive but inadequate to result in change. Soft OR (cognitive mapping) was used to identify new issues and enhance results. Consequently, the planned PICU expansion was deferred, and resources focused on improving staffing strategies identified independently from both hard and soft OR. These findings suggest that: (1) Outcomes research can play a unique role to enhance results in healthcare OR. (2) After obtaining a holistic understanding of the system using hard and soft OR, stakeholders are willing to implement results from each independently, supporting the development of a common form of knowledge, which is consistent with Mixed-Mode Modelling. (3) Hard OR, enhanced with outcomes research, with active stakeholder participation, and combined with soft OR, results in greater acceptance and sustained organizational change. 相似文献
22.
23.
The gas-phase thermal decomposition rate of peroxy-n-butyryl nitrate (n-C3H7C(O)OONO2, PnBN) has been measured at ambient temperature (296 K) and 1 atm of air relative to that of peroxyacetyl nitrate (CH3C(O)OONO2, PAN) using mixtures of PAN (14–19 ppb), PnBN (22–46 ppb), and nitric oxide (1.35–1.90 ppm). The PnBN/PAN decomposition rate ratio was 0.773 ± 0.030. This ratio, together with a literature value of 3.0 × 10?4 s?1 for the thermal decomposition rate of PAN at 296 K, yields a PnBN thermal decomposition rate of (2.32 ± 0.09) × 10?4 s?1. The results are briefly discussed by comparison with data for other peroxyacyl nitrates and with respect to the atmospheric persistence of PnBN. © 1994 John Wiley & Sons, Inc. 相似文献
24.
25.
26.
Ultrasonic wave propagation in cancellous and cortical bone: prediction of some experimental results by Biot's theory. 总被引:1,自引:0,他引:1
J L Williams 《The Journal of the Acoustical Society of America》1992,91(2):1106-1112
Pulse transmission ultrasound was used to determine the longitudinal wave speed along the direction of trabecular alignment in 32 water-saturated anisotropic tibial bovine cancellous bone samples and in one cortical bone sample also from the bovine tibia. These results are compared to published ultrasound wave-speed data obtained from bovine femoral specimens. Nonlinear regression was used to fit Biot's theory to the data. The correlation coefficient for regression analysis between the experimental ultrasound velocities and the velocities predicted by Biot's theory was r = 0.78. 相似文献
27.
28.
M.D. Williams S.C. Williams S.A. Yasharahla N. Jallow 《Applied Surface Science》2007,253(20):8568-8570
Ultraviolet photoemission spectroscopy is used to study the kinetics of the H-Zn complex deactivation in Zn doped InP(1 0 0). Hydrogen injected into the material electronically passivates the local carrier concentration. Reverse-biased anneals of the InP under ultra-high vacuum show a dramatic change in the work function of the material with increasing temperature. Spectral features are also shown to be sensitive to sample temperature. To our knowledge, we show the first view of hydrogen retrapping at the surface using photoemission spectroscopy. A simple photoelectron threshold energy analysis shows the state of charge compensation of the material. 相似文献
29.