全文获取类型
收费全文 | 15087篇 |
免费 | 1097篇 |
国内免费 | 59篇 |
专业分类
电工技术 | 253篇 |
综合类 | 18篇 |
化学工业 | 3486篇 |
金属工艺 | 470篇 |
机械仪表 | 760篇 |
建筑科学 | 344篇 |
矿业工程 | 6篇 |
能源动力 | 717篇 |
轻工业 | 1235篇 |
水利工程 | 55篇 |
石油天然气 | 10篇 |
武器工业 | 2篇 |
无线电 | 2673篇 |
一般工业技术 | 3301篇 |
冶金工业 | 1114篇 |
原子能技术 | 184篇 |
自动化技术 | 1615篇 |
出版年
2024年 | 17篇 |
2023年 | 158篇 |
2022年 | 245篇 |
2021年 | 392篇 |
2020年 | 321篇 |
2019年 | 361篇 |
2018年 | 480篇 |
2017年 | 425篇 |
2016年 | 552篇 |
2015年 | 448篇 |
2014年 | 650篇 |
2013年 | 1008篇 |
2012年 | 913篇 |
2011年 | 1134篇 |
2010年 | 849篇 |
2009年 | 910篇 |
2008年 | 862篇 |
2007年 | 713篇 |
2006年 | 599篇 |
2005年 | 532篇 |
2004年 | 478篇 |
2003年 | 428篇 |
2002年 | 407篇 |
2001年 | 347篇 |
2000年 | 323篇 |
1999年 | 318篇 |
1998年 | 464篇 |
1997年 | 354篇 |
1996年 | 265篇 |
1995年 | 207篇 |
1994年 | 161篇 |
1993年 | 126篇 |
1992年 | 88篇 |
1991年 | 80篇 |
1990年 | 80篇 |
1989年 | 77篇 |
1988年 | 54篇 |
1987年 | 62篇 |
1986年 | 61篇 |
1985年 | 42篇 |
1984年 | 29篇 |
1983年 | 37篇 |
1982年 | 15篇 |
1981年 | 25篇 |
1980年 | 21篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 23篇 |
1976年 | 31篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
In this paper, we propose a computational framework to incorporate regularization terms used in regularity based variational methods into least squares based methods. In the regularity based variational approach, the image is a result of the competition between the fidelity term and a regularity term, while in the least squares based approach the image is computed as a minimizer to a constrained least squares problem. The total variation minimizing denoising scheme is an exemplary scheme of the former approach with the total variation term as the regularity term, while the moving least squares method is an exemplary scheme of the latter approach. Both approaches have appeared in the literature of image processing independently. By putting schemes from both approaches into a single framework, the resulting scheme benefits from the advantageous properties of both parties. As an example, in this paper, we propose a new denoising scheme, where the total variation minimizing term is adopted by the moving least squares method. The proposed scheme is based on splitting methods, since they make it possible to express the minimization problem as a linear system. In this paper, we employed the split Bregman scheme for its simplicity. The resulting denoising scheme overcomes the drawbacks of both schemes, i.e., the staircase artifact in the total variation minimizing based denoising and the noisy artifact in the moving least squares based denoising method. The proposed computational framework can be utilized to put various combinations of both approaches with different properties together. 相似文献
92.
Hyeon Gyu Kim Yoo Hyun Park Yang Hyun Cho Myoung Ho Kim 《Journal of Intelligent Information Systems》2014,43(2):323-347
The join is an important operator in processing data streams. To produce outputs continuously over unbounded data streams, sliding windows are generally used to limit the scope of the join at a certain time. In the existing join algorithms, only a simple type of windows have been considered, which are updated whenever a new data item arrives on any input stream. On the other hand, a more common type of windows have not been addressed yet, whose intervals are updated periodically, i.e., slid by a predefined time interval. In this paper, we consider the time-slide windows in joining multiple data streams. The algorithm for the time-slide window join can vary according to (i) how frequently the join is evaluated and (ii) which structure is used for windowing. Regarding this, possible algorithms are discussed, and experimental results that compare their performances are provided in this paper. 相似文献
93.
Different amounts of K2 CO3 were added to (Ba,Sr)TiO3 -based PTCR (positive temperature coefficient of resistance) ceramics to investigate their influence on the microstructural and electrical properties. Experimental results showed that the incorporation of K acted as an A-site acceptor-type dopant. In addition to enhancing discontinuous grain growth, the increase of K2 CO3 was found to raise the room-temperature resistivity which was dominated by grain-boundary resistance rather than grain resistance. By adjusting to a suitable amount of donor dopant, the inherent contamination of K in raw material can be compensated to achieve a high-quality PTC resistor. 相似文献
94.
Natural objects often contain vivid color distribution with wide variety of colors. Conventional colorization techniques, on the other hand, produce colors that are relatively flat with little color variation. In this paper, we introduce a randomized algorithm which considers not only the value of target color but also the distribution of target color. In essence, our algorithm paints a color distribution to a region which synthesizes color distribution of a natural object. Our approach models the correlation between intensity and color in HSV color space in terms of H – S, H – V and S – V joint histogram. During the colorization process, we randomly swap and reassign color of a pixel to minimize a cost function that measures color consistency to its neighborhood and intensity‐to‐color correlation captured in the joint histogram. We tested our algorithm extensively on many natural objects and our user study confirms that our results are more vivid and natural compared to results from previous techniques. 相似文献
95.
Yong K. Park Ho K. Lee Nong M. Hwang Houk C. Kwon Jong C. Park Duk N. Yoon 《Journal of the American Ceramic Society》1988,71(6):297-C
Microstructures of Y-Ba-Cu-O superconductor were observed using a polarized microscope. Orthorhombic and tetragonal phases were easily distinguished by the optical etching with cross-polarized light. In the specimen cooled rapidly in oxygen, it was possible to see the path of oxygen diffusion by observing the variation of the twin concentration. At the boundary between transformed and untransformed materials, evidence for diffusion-driven transformation could be clearly seen. 相似文献
96.
Some earlier observations on the influence of molecular weight, plasticizer, and irradiation on the thermal conductivity of polymers is reviewed. Also some new data on polystyrene and some new calculations based on the theory of Hansen and Ho are presented. These data show almost a two fold increase in the thermal conductivity of polystyrene as the molecular weight goes from 900 to 100,000. Data on the moleculer weight effect on thermal conductivity appear to be consistent with the theoretical calculations. 相似文献
97.
Summary Isothermal cure kinetics ofEPON HPT 1071/DDS system have been performed by means of differential scanning calorimetry. The maximum cure rate and the extent of conversion at various DDS concentrations were studied as a function of cure temperature. Maximum cure rate increases with increasing cure temperature and DDS concentration. At various DDS concentrations, the maximum cure rate occured between 19–22% conversion. In order to evaluate the kinetic parameters, numerical calculations by means of a Newton-Raphson technique and experimental results obtained from the peak of reaction rate curve were undertaken. 相似文献
98.
PdOx/MnO2 has been examined as a catalyst for CO oxidation using a conventional flow reactor at reaction temperatures between 50 and 150°C. In the reaction conditions of GHSV (gashourlyspacevelocity) of 1.22 × 105/h and CO concentration of 2000 ppm, PdOx/MnO2 showed higher catalytic activity compared with PdOx/Mn2O3, which had been previously reported as an effective catalyst due to the cooperative action of Pd and Mn2O3 for this reaction. The reason for higher activity of PdOx/MnO2 than PdOx/Mn2O3 has been investigated using TPR (temperatureprogrammed reduction) and XPS studies. TPR showed that PdOx/MnO2 could be reduced by CO at much lower temperature than PdOx/Mn2O3. During the experiment of reduction and oxidation, XPS showed that the valence of Mn in the PdOx/MnO2 was between 4+ and 3+, which is higher than that of Mn in the PdOx/Mn2O3 catalyst of which the valence has been reported to be between 3+ and 2+. It is known that in this catalyst system the support supplies oxygen onto Pd, where the oxidation occurs with adsorbed CO, and the ability of the support to provide oxygen improves the performance of the catalyst. Therefore, it was concluded that the readiness of MnO2 to be reduced with maintaining a higher oxidation state showed higher CO oxidation activity than Mn2O3 as support for PdOx. 相似文献
99.
Summary New biodegradable hydrophobic polyurethane (PU)/hydrophilic poly (ethylene glycol) diacrylate (PEGDA) IPN was simultaneously synthesized with changing the molecular weight of PEGDA to investigate the effect of crosslinking density on the degree of phase separation. PU was modified using biodegradable poly(-caprolactone)diol and the hydroxy group of PEG was substituted to crosslinkable acrylate group having double bond, which induce photo-polymerization. The sturucture of PEGDA was confirmed by NMR. Because the reaction rate of PEGDA was faster than that of PU, the continuous matrix of the micro-separated PU/PEGDA IPNs having amphiphilic character was made of hydrophilic PEGDA-rich phase. All IPNs have sea-island morphology resulting from the suppressed phase separation. The effect of the degree of phase separation on blood compatibility was investigated. 相似文献
100.
Qinyun Chen Huang Shi Chi-Tang Ho 《Journal of the American Oil Chemists' Society》1992,69(10):999-1002
Rosemary (Rosemarinus officinalis L.) leaves were extracted with three different solvents, namely hexane, acetone and methanol. A reverse-phase high-performance
liquid chromatography system in combination with a mass detector was used to quantitate the content of carnosol, carnosic
acid and ursolic acid in the rosemary extracts. All rosemary extracts showed strong inhibitory effects on lipid oxidation
and soybean lipoxygenase activity. 相似文献