全文获取类型
收费全文 | 3796篇 |
免费 | 202篇 |
国内免费 | 123篇 |
专业分类
电工技术 | 80篇 |
综合类 | 203篇 |
化学工业 | 463篇 |
金属工艺 | 41篇 |
机械仪表 | 153篇 |
建筑科学 | 168篇 |
矿业工程 | 33篇 |
能源动力 | 19篇 |
轻工业 | 604篇 |
水利工程 | 7篇 |
石油天然气 | 17篇 |
武器工业 | 22篇 |
无线电 | 531篇 |
一般工业技术 | 281篇 |
冶金工业 | 128篇 |
原子能技术 | 17篇 |
自动化技术 | 1354篇 |
出版年
2024年 | 7篇 |
2023年 | 29篇 |
2022年 | 43篇 |
2021年 | 74篇 |
2020年 | 62篇 |
2019年 | 46篇 |
2018年 | 44篇 |
2017年 | 86篇 |
2016年 | 118篇 |
2015年 | 126篇 |
2014年 | 192篇 |
2013年 | 263篇 |
2012年 | 214篇 |
2011年 | 227篇 |
2010年 | 212篇 |
2009年 | 229篇 |
2008年 | 195篇 |
2007年 | 262篇 |
2006年 | 203篇 |
2005年 | 205篇 |
2004年 | 212篇 |
2003年 | 159篇 |
2002年 | 164篇 |
2001年 | 118篇 |
2000年 | 93篇 |
1999年 | 91篇 |
1998年 | 69篇 |
1997年 | 70篇 |
1996年 | 63篇 |
1995年 | 41篇 |
1994年 | 37篇 |
1993年 | 39篇 |
1992年 | 27篇 |
1991年 | 19篇 |
1990年 | 10篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1973年 | 2篇 |
1965年 | 2篇 |
1963年 | 3篇 |
1961年 | 2篇 |
1955年 | 4篇 |
1954年 | 1篇 |
排序方式: 共有4121条查询结果,搜索用时 15 毫秒
1.
2.
Clip-art image segmentation is widely used as an essential step to solve many vision problems such as colorization and vectorization. Many of these applications not only demand accurate segmentation results, but also have little tolerance for time cost, which leads to the main challenge of this kind of segmentation. However, most existing segmentation techniques are found not sufficient for this purpose due to either their high computation cost or low accuracy. To address such issues, we propose a novel segmentation approach, ECISER, which is well-suited in this context. The basic idea of ECISER is to take advantage of the particular nature of cartoon images and connect image segmentation with aliased rasterization. Based on such relationship, a clip-art image can be quickly segmented into regions by re-rasterization of the original image and several other computationally efficient techniques developed in this paper. Experimental results show that our method achieves dramatic computational speedups over the current state-of-the-art approaches, while preserving almost the same quality of results. 相似文献
3.
Artificial bee colony (ABC) algorithm has several characteristics that make it more attractive than other bio-inspired methods. Particularly, it is simple, it uses fewer control parameters and its convergence is independent of the initial conditions. In this paper, a novel artificial bee colony based maximum power point tracking algorithm (MPPT) is proposed. The developed algorithm, does not allow only overcoming the common drawback of the conventional MPPT methods, but it gives a simple and a robust MPPT scheme. A co-simulation methodology, combining Matlab/Simulink™ and Cadence/Pspice™, is used to verify the effectiveness of the proposed method and compare its performance, under dynamic weather conditions, with that of the Particle Swarm Optimization (PSO) based MPPT algorithm. Moreover, a laboratory setup has been realized and used to experimentally validate the proposed ABC-based MPPT algorithm. Simulation and experimental results have shown the satisfactory performance of the proposed approach. 相似文献
4.
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
5.
Gennaro Costagliola Vincenzo Deufemia Filomena Ferrucci Carmine Gravino 《Information and Computation》2003,187(2):209-245
Drawn symbolic pictures are an extension of drawn pictures obtained by associating a symbol from an alphabet to each point of the picture. In the paper we will address some new interesting issues derived from the introduction of the symbols and we will identify the conditions, which ensure the preservation of properties holding for drawn pictures in the setting of the proposed extension. 相似文献
6.
本文在条状屏彩色显象管校正透镜设计的基础上,提出了蹼状屏彩色显示管校正透镜的优化设计方法并给出了设计实例,通过计算机模拟电子束轨迹和光线追迹,分析了校正透镜面型修正程序的精度。 相似文献
7.
Hugh S. Fairman 《Color research and application》1995,20(1):44-49
In 1993, the American Society for Testing and Materials carried out a field test of newly calculated tristimulus weighting factors. These weighting factors had been calculated by a method proposed by Venable. the test also included a method of correction for bandpass dependence put forth by Stearns. the purpose of the trial was to assess the possible reduction in bandpass dependence introduced by each of these sets of weights. A large number of sets of spectral data were gathered from the cooperators in the field test. Results of integration by the various sets of tristimulus weighting factors were calculated. A total of 15 120 color differences were calculated and statistics were derived to test the probable error resulting from each method of correction. Errors attributable to bandpass dependence were on the order of a few tenths to as much as one CIELAB unit when uncorrected weight sets were used. These errors could be reduced to a few hundreths of a CIELAB unit, and in some cases to a few thousandths of a unit, by employing one correcting strategy or the other. an overall mix of strategies was ultimately chosen to minimize the bandpass dependence over the entire range of weight sets. Utilizing this mixed strategy, the median error introduced into 10-nm integration by bandpass dependence was only 0.004 CIELAB units. © 1995 John Wiley & Sons, Inc. 相似文献
8.
Lennart Sjberg 《Displays》1987,8(4):210-212
A discussion of the factors involved in the subjective perception of television picture quality is presented. Much of the work in this field is cited, and it is concluded that future work needs to consider a broader range of variables than has been looked at so far. 相似文献
9.
Two different generators for ozone were tested, a traditional electrical discharge generator and a generator based upon UV–irradiation of air at 150–180 nm. It was demonstrated that the traditional generator gave slightly higher reductions in levels of color for equivalent ozone dosages. Both gases affected the molecular weight distribution in the way that the bigger molecules were broken down to smaller ones. No significant difference between the molecular weight reduction efficiency of the gases was found. 相似文献
10.