全文获取类型
收费全文 | 3476篇 |
免费 | 38篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 50篇 |
综合类 | 4篇 |
化学工业 | 210篇 |
金属工艺 | 10篇 |
机械仪表 | 40篇 |
建筑科学 | 107篇 |
矿业工程 | 2篇 |
能源动力 | 77篇 |
轻工业 | 53篇 |
水利工程 | 9篇 |
无线电 | 376篇 |
一般工业技术 | 254篇 |
冶金工业 | 2079篇 |
原子能技术 | 5篇 |
自动化技术 | 244篇 |
出版年
2022年 | 18篇 |
2021年 | 17篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 10篇 |
2017年 | 18篇 |
2016年 | 25篇 |
2015年 | 19篇 |
2014年 | 31篇 |
2013年 | 93篇 |
2012年 | 43篇 |
2011年 | 67篇 |
2010年 | 57篇 |
2009年 | 75篇 |
2008年 | 49篇 |
2007年 | 70篇 |
2006年 | 67篇 |
2005年 | 64篇 |
2004年 | 52篇 |
2003年 | 42篇 |
2002年 | 47篇 |
2001年 | 55篇 |
2000年 | 40篇 |
1999年 | 101篇 |
1998年 | 706篇 |
1997年 | 386篇 |
1996年 | 284篇 |
1995年 | 148篇 |
1994年 | 133篇 |
1993年 | 143篇 |
1992年 | 43篇 |
1991年 | 52篇 |
1990年 | 44篇 |
1989年 | 50篇 |
1988年 | 45篇 |
1987年 | 25篇 |
1986年 | 40篇 |
1985年 | 47篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 34篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 38篇 |
1976年 | 81篇 |
1975年 | 6篇 |
1973年 | 9篇 |
1972年 | 6篇 |
排序方式: 共有3520条查询结果,搜索用时 15 毫秒
1.
Development of a recurrent Sigma-Pi neural network rainfall forecasting system in Hong Kong 总被引:1,自引:1,他引:0
At the moment, weather forecasting is still an art — the experience and intuition of forecasters play a significant role in determining the quality of forecasting. This paper describes the development of a new approach to rainfall forecasting using neural networks. It deals with the extraction of information from radar images and an evaluation of past rain gauge records to provide shortterm rainfall forecasting. All of the meteorological data were provided by the Royal Observatory of Hong Kong (ROHK). Preprocessing procedures were essential for this neural network rainfall forecasting. The forecast of the rainfall was performed every half an hour so that a storm warning signal can be delivered to the public in advance. The network architecture is based on a recurrent Sigma-Pi network. The results are very promising, and this neural-based rainfall forecasting system is capable of providing a rain storm warning signal to the Hong Kong public one hour ahead. 相似文献
2.
Power distribution systems have been significantly affected by many outage-causing events. Good fault cause identification can help expedite the restoration procedure and improve the system reliability. However, the data imbalance issue in many real-world data sets often degrades the fault cause identification performance. In this paper, the E-algorithm, which is extended from the fuzzy classification algorithm by Ishibuchi to alleviate the effect of imbalanced data constitution, is applied to Duke Energy outage data for distribution fault cause identification. Three major outage causes (tree, animal, and lightning) are used as prototypes. The performance of E-algorithm on real-world imbalanced data is compared with artificial neural network. The results show that the E-algorithm can greatly improve the performance when the data are imbalanced 相似文献
3.
A 78-year-old Chinese woman presented with recurrent postprandial abdominal pain. Computerised tomography revealed a small bowel tumour causing volvulus of a segment of the small bowel. Laparotomy confirmed an extraluminal ileal tumour with partial volvulus of the involved small bowel segment. Small bowel resection was done. Histological and ultrastructural studies confirmed a gastrointestinal autonomic nerve tumour. We review the medical literature on this rare tumour. 相似文献
4.
5.
PURPOSE: The purpose of this study was to assess the value of 3-dimensional sonography in the diagnosis of congenital müllerian duct anomalies, which cause infertility, preterm labor, and first trimester abortion. METHODS: A prospective study was undertaken in which 40 patients with histories of repeated spontaneous abortions or infertility were first examined using conventional 2-dimensional sonography or hysterosalpingography. Three-dimensional transvaginal sonography was then performed. RESULTS: Twenty-eight women had müllerian duct abnormalities, and 12 women had normal uterine anatomy. Müllerian duct defects detected in this study were unicornuate uterus (3), bicornuate uterus (3), complete or partial septate uterus (12), arcuate uterus (9), and didelphic uterus (1). The diagnosis of müllerian duct anomalies in these patients was confirmed by laparoscopic and/or hysteroscopic examinations. Three-dimensional sonography demonstrated all congenital uterine abnormalities with a sensitivity and specificity of 100%. Separate uterus and bicornuate uterus could be correctly diagnosed using 3-dimensional sonography in 11 (92%) of 12 cases and 3 (100%) of 3 cases, respectively. These 2 abnormalities were commonly confused with each other using hysterosalpingography and conventional sonography. CONCLUSIONS: Three-dimensional sonography with image reconstruction is less expensive and less invasive than hysterosalpingography for the assessment of uterine anatomy and diagnosis of müllerian duct abnormalities. The ability to visualize both the uterine cavity and the myometrium on a 3-dimensional scan facilitates the diagnosis of uterine anomalies and enables the differentiation of septate from bicornuate uteri for preoperative surgical planning. 相似文献
6.
7.
This paper studies a particular single-stage power-factor-correction (PFC) switching regulator employing a discontinuous-conduction-mode (DCM) boost-input cell and a continuous-current-mode (CCM) forward output cell. Although this single-stage PFC regulator can provide a reasonably high power factor when its PFC stage is operating in discontinuous mode, substantial reduction in line-current harmonics is possible by applying a suitable frequency-modulation scheme. This paper derives a frequency-modulation scheme and proposes a practical implementation using a simple translinear analog circuit. A quantitative analysis on the total harmonic distortion (THD) of the line current when the circuit is subject to a limited range of frequency variations is presented along with some considerations for practical design. Experimental data obtained from a prototype confirms the effectiveness of the proposed frequency-modulation scheme. The proposed analog translinear circuit allows custom integrated circuit implementation, making it a viable low-cost solution to the elimination of line-current harmonics in switching regulators 相似文献
8.
On smoke control for tunnels by longitudinal ventilation 总被引:2,自引:0,他引:2
W. K. Chow 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》1998,13(3):336
Two aspects of smoke control by longitudinal ventilation systems in tunnels is analysed. The first is the increase in air entrainment rate of the plume after operating the system, and the second is the increase in heat release rate as a consequence of increase in air supply rate for combustion. Computational fluid dynamics (CFD) was applied for verifying the study. Keypoints to consider in the design of longitudinal ventilation systems are noted. 相似文献
9.
10.
Gram-negative shock is thought to result primarily from the effects of endotoxin, a component of the bacterial outer membrane. Accordingly, therapies aimed at inhibiting, neutralizing, or clearing endotoxin have been extensively explored. Despite over 30 years of research, no antiendotoxin approach to the treatment of human septic shock is of proven benefit. In recent randomized clinical trials of monoclonal antibodies against endotoxin, therapeutic efficacy was not convincingly demonstrated. This result, however, does not eliminate the possibility that other antiendotoxin therapies may be effective. The antibodies used in these clinical trials do not appear to neutralize endotoxin in vitro and are not reproducibly protective in animal models of sepsis. Newer agents with well-defined mechanisms of antiendotoxin activity may help clarify the role of endotoxin in septic shock and prove useful therapy for some patients. 相似文献