全文获取类型
收费全文 | 3204篇 |
免费 | 214篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 58篇 |
综合类 | 18篇 |
化学工业 | 797篇 |
金属工艺 | 70篇 |
机械仪表 | 45篇 |
建筑科学 | 170篇 |
矿业工程 | 6篇 |
能源动力 | 143篇 |
轻工业 | 177篇 |
水利工程 | 23篇 |
石油天然气 | 7篇 |
无线电 | 294篇 |
一般工业技术 | 680篇 |
冶金工业 | 261篇 |
原子能技术 | 10篇 |
自动化技术 | 678篇 |
出版年
2023年 | 60篇 |
2022年 | 131篇 |
2021年 | 165篇 |
2020年 | 108篇 |
2019年 | 113篇 |
2018年 | 116篇 |
2017年 | 129篇 |
2016年 | 139篇 |
2015年 | 118篇 |
2014年 | 174篇 |
2013年 | 212篇 |
2012年 | 231篇 |
2011年 | 239篇 |
2010年 | 160篇 |
2009年 | 159篇 |
2008年 | 149篇 |
2007年 | 129篇 |
2006年 | 106篇 |
2005年 | 57篇 |
2004年 | 71篇 |
2003年 | 51篇 |
2002年 | 47篇 |
2001年 | 39篇 |
2000年 | 35篇 |
1999年 | 35篇 |
1998年 | 82篇 |
1997年 | 54篇 |
1996年 | 28篇 |
1995年 | 32篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 26篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 14篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1971年 | 9篇 |
1967年 | 7篇 |
排序方式: 共有3437条查询结果,搜索用时 9 毫秒
1.
2.
3.
4.
Requirements engineering in health care: the example of chemotherapy planning in paediatric oncology
Health care is characterized by highly complex processes of patient care that require unusual amount of communication between different health care professionals of different institutions. Sub-optimal processes can significantly impact on the patient’s health, increase the consumption of services and resources and in severe cases can lead to the patient death. For these reasons, requirements engineering for the development of information technology in health care is a complex process as well: without constant and rigorous evaluation, the impact of new systems on the quality of care is unknown and it is possible that badly designed systems significantly harm patients. To overcome these limitations, we present and discuss an approach to requirements engineering that we applied for the development of applications for chemotherapy planning in paediatric oncology. Chemotherapy planning in paediatric oncology is complex and time-consuming and errors must be avoided by all means. In the multi-hospital/multi-trial-centre environment of paediatric oncology, it is especially difficult and time-consuming to analyse requirements. Our approach combines a grounded theory approach with evolutionary prototyping based on the constant development and refinement of a generic domain model, in this case a domain model for chemotherapy planning in paediatric oncology. The prototypes were introduced in medical centres and final results show that the developed generic domain model is adequate. 相似文献
5.
6.
Focal biomagnetic sources are described as pointlike current dipoles. The dipole parameters, position, and moment coordinates are commonly determined from biomagnetic data using iterative nonlinear optimization algorithms such as the Levenberg-Marquardt algorithm. However, even for single-dipole sources, mislocalizations can occur due to side minima of the cost function or due to a wrong choice of the start vector. This can be shown by introducing a cost function where the independent variables are only the position coordinates instead of position and moment coordinates. This dimensional reduction-which is also possible for multiple dipole sources-is achieved by calculating the cost function at each position with the position and data-dependent, optimum dipole moments. The authors call these dipoles with-in a least squares sense-optimum moments, locally optimal dipoles. The visualization of such a single-dipole cost function and of the iteration steps of the Levenberg-Marquardt algorithm show why mislocalizations cannot be avoided. Therefore, the authors propose an alternative noniterative localization algorithm for single-dipole sources without this drawback. It uses localization probabilities calculated by means of the locally optimal dipoles. Besides the determination of the dipole parameters, the proposed algorithm furnishes a reliable error for each localization. Its effectiveness is shown with simulated and real patient data 相似文献
7.
8.
KP Scholz 《Canadian Metallurgical Quarterly》1993,16(10):395-397
9.
Alan Owens Sebastian M. Pascarelle Neil Gehrels Bonnard J. Teegarden 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1991,310(3):681-684
We have extended the empirical work of Vano et al.[1] relating the slope of the detector efficiency curve to the active volume for Ge detectors. The analysis was carried out using Monte Carlo techniques and covered a wide range of incident energies (200 keV-20 MeV) and active volumes (19.6 cm3–396 cm3). It is shown that the expression of Vano et al.[1] is only valid over the energy range 200 keV-3 MeV for active volumes <50 cm3. The upper bound decreases to 2 MeV for volumes of a few hundred cm3. The usable energy range can, however, be extended to 6 MeV by introducing higher order terms into the polynomial. Above this energy, the shape of the efficiency curve is better described by a non-linear function since linear forms fail simultaneously to fit large active volumes and high energies. We therefore propose a composite function which reduces to the form given in Vano et al. in the low energy/active volume limit. By comparison with the Monte Carlo results, it is estimated that relative efficiencies can be calculated to within 6% over the energy range 200 keV-20 MeV and active volumes 20 cm3–400 cm3. Since the largest errors occur for the smallest volumes, we recommend that for energies <3 MeV a two-fold approach be followed, i.e. using the expression of Vano et al.[1] for active volumes less than 50 cm3 and the proposed non-linear form for larger volumes. For high energy work (E > 3 MeV), we advocate the non-linear form. In this way, average errors can be kept 3%. Finally, we point out that the real power of the expression of Vano et al. lies not in predicting efficiencies, but active volumes. 相似文献
10.