全文获取类型
收费全文 | 2804篇 |
免费 | 564篇 |
国内免费 | 270篇 |
专业分类
电工技术 | 292篇 |
综合类 | 224篇 |
化学工业 | 255篇 |
金属工艺 | 71篇 |
机械仪表 | 106篇 |
建筑科学 | 144篇 |
矿业工程 | 57篇 |
能源动力 | 74篇 |
轻工业 | 58篇 |
水利工程 | 25篇 |
石油天然气 | 67篇 |
武器工业 | 20篇 |
无线电 | 231篇 |
一般工业技术 | 196篇 |
冶金工业 | 55篇 |
原子能技术 | 6篇 |
自动化技术 | 1757篇 |
出版年
2024年 | 26篇 |
2023年 | 61篇 |
2022年 | 102篇 |
2021年 | 90篇 |
2020年 | 131篇 |
2019年 | 96篇 |
2018年 | 90篇 |
2017年 | 93篇 |
2016年 | 118篇 |
2015年 | 138篇 |
2014年 | 187篇 |
2013年 | 193篇 |
2012年 | 201篇 |
2011年 | 227篇 |
2010年 | 173篇 |
2009年 | 196篇 |
2008年 | 205篇 |
2007年 | 208篇 |
2006年 | 160篇 |
2005年 | 149篇 |
2004年 | 122篇 |
2003年 | 93篇 |
2002年 | 96篇 |
2001年 | 90篇 |
2000年 | 55篇 |
1999年 | 58篇 |
1998年 | 67篇 |
1997年 | 52篇 |
1996年 | 40篇 |
1995年 | 26篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有3638条查询结果,搜索用时 890 毫秒
1.
ABSTRACTThis paper presents an empirical assessment of four state-of-the-art risk-averse approaches to deal with the capacitated lot-sizing problem under stochastic demand. We analyse two mean-risk models based on the semideviation and on the conditional value-at-risk risk measures, and alternate first and second-order stochastic dominance approaches. The extensive computational experiments based on different instances characteristics and on a case-study suggest that CVaR exhibits a good trade-off between risk and performance, followed by the semideviation and first-order stochastic dominance approach. For all approaches, enforcing risk-aversion helps to reduce the cost-standard deviation substantially, which is usually accomplished via increasing production rates. Overall, we can say that very risk-averse decision-makers would be willing to pay an increased price to have a much less risky solution given by CVaR . In less risk-averse settings, though, semideviation and first-order stochastic dominance can be appealing alternatives to provide significantly more stable production planning costs with a marginal increase of the expected costs. 相似文献
2.
《Displays》2015
Multi-projector displays allow the realization of large and immersive projection environments by allowing the tiling of projections from multiple projectors. Such tiled displays require real time geometrical warping of the content that is being projected from each projector. This geometrical warping is a computationally intensive operation and is typically applied using high-end graphics processing units (GPUs) that are able to process a defined number of projector channels. Furthermore, this limits the applicability of such multi-projector display systems only to the content that is being generated using desktop based systems. In this paper we propose a platform independent FPGA based scalable hardware architecture for geometric correction of projected content that allows addition of each projector channel at a fractional increase in logic area. The proposed scheme provides real time correction of HD quality video streams and thus enables the use of this technology for embedded and standalone devices. 相似文献
3.
Greenish yellow organic light-emitting diodes (GYOLEDs) have steadily attracted researcher's attention since they are important to our life. However, their performance significantly lags behind compared with the three primary colors based OLEDs. Herein, for the first time, an ideal host-guest system has been demonstrated to accomplish high-performance phosphorescent GYOLEDs, where the guest concentration is as low as 2%. The GYOLED exhibits a forward-viewing power efficiency of 57.0 lm/W at 1000 cd/m2, which is the highest among GYOLEDs. Besides, extremely low efficiency roll-off and voltages are achieved. The origin of the high performance is unveiled and it is found that the combined mechanisms of host-guest energy transfer and direct exciton formation on the guest are effective to furnish the greenish yellow emission. Then, by dint of this ideal host-guest system, a simplified but high-performance hybrid white OLED (WOLED) has been developed. The WOLED can exhibit an ultrahigh color rendering index (CRI) of 92, a maximum total efficiency of 27.5 lm/W and a low turn-on voltage of 2.5 V (1 cd/m2), unlocking a novel avenue to simultaneously achieve simplified structure, ultrahigh CRI (>90), high efficiency and low voltage. 相似文献
4.
5.
DGPSL:A DISTRIBUTED GRAPHICS LIBRARY 总被引:1,自引:0,他引:1
DGPSL:ADISTRIBUTEDGRAPHICSLIBRARYShiJiaoying;PanZhigeng;ZhengWentingDGPSL:ADISTRIBUTEDGRAPHICSLIBRARY¥ShiJiaoying;PanZhigeng;... 相似文献
6.
7.
Second-law-based thermodynamic analysis of two-stage and mechanical-subcooling refrigeration cycles 总被引:1,自引:0,他引:1
Thermodynamic analysis of HFC-134a vapor-compression refrigeration cycles is investigated by both the first and second laws of thermodynamics. Second-law analysis is carried out for both two-stage and mechanical-subcooling refrigeration cycles. The analysis is performed on each of the system components to determine their individual contribution to the overall system irreversible losses. It is found that most of the losses are due to a low compressor efficiency. Irreversibilities of expansion valves and condenser are also significant. In addition, it is shown that the optimum inter-stage pressure for two-stage and mechanical-subcooling refrigeration systems is very close to the saturation pressure corresponding to the arithmetic mean of the refrigerant condensation and evaporation temperatures. These results are compared with the existing practice in the industry. Furthermore, theoretical results of a two-stage refrigeration system performance are also compared with experimental values for a CFC-22 system. 相似文献
8.
Inverse surface design problems from light transport behavior specification usually represent extremely complex and costly processes, but their importance is well known. In particular, they are very interesting for lighting and luminaire design, in which it is usually difficult to test design decisions on a physical model in order to avoid costly mistakes. In this survey, we present the main ideas behind these kinds of problems, characterize them, and summarize existing work in the area, revealing problems that remain open and possible areas of further research. 相似文献
9.
10.
Roy S. Berns 《Color research and application》2007,32(4):334-335
The term “color gamut” historically has been associated with color output such as optimal color stimuli and additive and subtractive imaging systems. Recently, this term has been used with input devices such as scanners and digital cameras. It is proposed that the term “color‐gamut rendering” should be used instead of input devices. This clarifies the distinction between input (analysis) and output (synthesis) color systems in terms of the effect of an input system on defining the colorimetric properties of an output system. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 334–335, 2007 相似文献