全文获取类型
收费全文 | 1667篇 |
免费 | 15篇 |
专业分类
电工技术 | 7篇 |
综合类 | 1篇 |
化学工业 | 79篇 |
金属工艺 | 3篇 |
机械仪表 | 13篇 |
建筑科学 | 14篇 |
矿业工程 | 5篇 |
能源动力 | 16篇 |
轻工业 | 57篇 |
水利工程 | 4篇 |
石油天然气 | 2篇 |
无线电 | 68篇 |
一般工业技术 | 99篇 |
冶金工业 | 1179篇 |
原子能技术 | 7篇 |
自动化技术 | 128篇 |
出版年
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 5篇 |
2018年 | 7篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 26篇 |
2012年 | 23篇 |
2011年 | 24篇 |
2010年 | 21篇 |
2009年 | 18篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 16篇 |
2004年 | 19篇 |
2003年 | 17篇 |
2002年 | 12篇 |
2001年 | 10篇 |
2000年 | 12篇 |
1999年 | 39篇 |
1998年 | 309篇 |
1997年 | 192篇 |
1996年 | 137篇 |
1995年 | 77篇 |
1994年 | 72篇 |
1993年 | 79篇 |
1992年 | 14篇 |
1991年 | 24篇 |
1990年 | 25篇 |
1989年 | 28篇 |
1988年 | 37篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 26篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 11篇 |
1981年 | 21篇 |
1980年 | 12篇 |
1978年 | 8篇 |
1977年 | 37篇 |
1976年 | 73篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1963年 | 3篇 |
排序方式: 共有1682条查询结果,搜索用时 15 毫秒
1.
To determine whether there is any correlation between sudden decrease in barometric pressure and onset of labor, a non-experimental, retrospective study at a 948-bed tertiary care hospital was done. Pregnant patients of 36 weeks gestation or more who presented with spontaneous onset of labor during the 48 hours surrounding the 12 occurrences of significant drop in barometric pressure in 1992 were included in the study. Significantly more occurrences of onset of labor were identified in the 24 hours after a drop in barometric pressure than were identified in the 24 hours prior to the drop in barometric pressure (P < 0.05). Therefore, the overall number of labor onsets increased in the 24 hours following a significant drop in barometric pressure. 相似文献
2.
3.
4.
5.
Connecting people across the “digital divide” is as much a social effort as a technological one. We are developing a community-centred
approach to learn how interaction techniques can compensate for poor communication across the digital divide. We have incorporated
the lessons learned regarding social intelligence design in an abstraction and in a device called the SoftBridge. The SoftBridge
allows communication to flow from endpoints through adapters, getting converted if necessary, and out to destination endpoints.
Field trials are underway with two communities in South Africa: disadvantaged Deaf users and an isolated rural community.
Initial lessons learned show that we have to design user interfaces that allow users to understand and cope with delay. We
also learned that social concerns are often more important than the technical issues in designing such systems. 相似文献
6.
7.
8.
At present, the preferred tool for parameter estimation in compartmental analysis is an iterative procedure; weighted nonlinear regression. For a large number of applications, observed data can be fitted to sums of exponentials whose parameters are directly related to the rate constants/coefficients of the compartmental models. Since weighted nonlinear regression often has to be repeated for many different data sets, the process of fitting data from compartmental systems can be very time consuming. Furthermore the minimization routine often converges to a local (as opposed to global) minimum. In this paper, we examine the possibility of using artificial neural networks instead of weighted nonlinear regression in order to estimate model parameters. We train simple feed-forward neural networks to produce as outputs the parameter values of a given model when kinetic data are fed to the networks' input layer. The artificial neural networks produce unbiased estimates and are orders of magnitude faster than regression algorithms. At noise levels typical of many real applications, the neural networks are found to produce lower variance estimates than weighted nonlinear regression in the estimation of parameters from mono- and biexponential models. These results are primarily due to the inability of weighted nonlinear regression to converge. These results establish that artificial neural networks are powerful tools for estimating parameters for simple compartmental models. 相似文献
9.
This study used a pretest-posttest preexperimental design to examine the effect of a 10-week behavioral medicine support group intervention in a sample of persons with HIV. Using Solomon's psychoneuroimmunologic framework, the 10-week behavioral medicine program focused on the mind/body interaction, the relaxation response, coping with illness, hardiness, and nutrition. Pearson correlation coefficients and t tests were performed on the pre- and postintervention measures of hardiness, social support, immune function, and perceived health status. Results of the study indicated that hardiness (preintervention) and CD4 counts (pre- and postintervention) were significantly correlated with health status; however, CD4 counts decreased over the course of the behavioral medicine program. Implications for nursing and recommendations for further research are discussed. 相似文献
10.
KL Hopkins PK Dickson TI Ball RR Ricketts PA O'Shea CR Abramowsky 《Canadian Metallurgical Quarterly》1997,32(10):1476-1479
Fetus-in-fetu is an unusual condition in which a vertebrate fetus is enclosed within the abdomen of another fetus. These occurrences are usually benign. This report describes an instance of malignant recurrence after resection of a fetus-in-fetu. 相似文献