全文获取类型
收费全文 | 145929篇 |
免费 | 6870篇 |
国内免费 | 3081篇 |
学科分类
工业技术 | 155880篇 |
出版年
2024年 | 282篇 |
2023年 | 1095篇 |
2022年 | 1917篇 |
2021年 | 2709篇 |
2020年 | 2045篇 |
2019年 | 1816篇 |
2018年 | 16204篇 |
2017年 | 15298篇 |
2016年 | 11888篇 |
2015年 | 3271篇 |
2014年 | 3605篇 |
2013年 | 4263篇 |
2012年 | 7627篇 |
2011年 | 14117篇 |
2010年 | 12261篇 |
2009年 | 9407篇 |
2008年 | 10329篇 |
2007年 | 11105篇 |
2006年 | 3334篇 |
2005年 | 3879篇 |
2004年 | 3179篇 |
2003年 | 3056篇 |
2002年 | 2419篇 |
2001年 | 1761篇 |
2000年 | 1538篇 |
1999年 | 1370篇 |
1998年 | 1087篇 |
1997年 | 801篇 |
1996年 | 756篇 |
1995年 | 600篇 |
1994年 | 454篇 |
1993年 | 376篇 |
1992年 | 296篇 |
1991年 | 225篇 |
1990年 | 175篇 |
1989年 | 123篇 |
1988年 | 135篇 |
1987年 | 63篇 |
1986年 | 81篇 |
1985年 | 44篇 |
1984年 | 39篇 |
1968年 | 46篇 |
1967年 | 39篇 |
1966年 | 45篇 |
1965年 | 46篇 |
1959年 | 37篇 |
1958年 | 39篇 |
1957年 | 38篇 |
1955年 | 66篇 |
1954年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
ABSTRACTThis paper proposes the multiple-hypotheses image segmentation and feed-forward neural network classifier for food recognition to improve the performance. Initially, the food or meal image is given as input. Then, the segmentation is applied to identify the regions, where a particular food item is located using salient region detection, multi-scale segmentation, and fast rejection. Then, the features of every food item are extracted by the global feature and local feature extraction. After the features are obtained, the classification is performed for each segmented region using a feed-forward neural network model. Finally, the calorie value is computed with the aid of (i) food volume and (ii) calorie and nutrition measure based on mass value. The experimental results and performance evaluation are validated. The outcome of the proposed method attains 0.947 for Macro Average Accuracy (MAA) and 0.959 for Standard Accuracy (SA), which provides better classification performance. 相似文献
2.
Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted
calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical
composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX
and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite
particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies
by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give
clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse
to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites
could be useful for hyperthermia. 相似文献
3.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method
in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer.
But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results
showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that,
the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic
whereas chloride doped polyaniline films were found to be highly hygroscopic. 相似文献
4.
5.
6.
From its foundation until 2004, ETRI has registered over 1,000 US patents. This letter analyzes the characteristics of these patents and addresses the explanatory factors affecting their citation counts. For explanatory variables, research team related variables, invention specific variables, and geographical domain related variables are suggested. Zero‐altered count data models are used to test the impact of independent variables. A key finding is that technological cumulativeness, the scale of invention, outputs in the electronic field, and the degree of dependence on the US technology domain positively affect the citation counts of ETRI‐invented US patents. The magnitude of international presence appears to negatively affect the citation counts of ETRI‐invented US patents. 相似文献
7.
8.
关于我国钢铁工业发展战略的思考 总被引:2,自引:0,他引:2
21世纪初是世界经济发展的重大战略机遇期,如何抓住机遇加快发展,是中国钢铁行业应认真思考的问题。十一五我国钢铁工业的发展,靠什么来拉动,还能靠大规模的投资吗?目前我们还不能生产的双高产品怎么办,靠花钱能买来技术吗?靠市场能换来核心产品吗?值得深思。当今,我们思考的不仅应考虑个别企业的生存问题,而更应考虑的是钢铁行业整体的长远发展问题,即 相似文献
9.
陈冬梅 《电子产品可靠性与环境试验》2003,(2):61-65
概要介绍了科学的管理技术——项目管理方法,讨论了管理跨度在项目管理中的重要性,并推荐了如何了解管理跨度的方法。 相似文献
10.
A new process for solid phase crystallization (SPC) of amorphous silicon (a-Si) using thin film heater is reported. With this localized Ti silicide thin film heater, we successfully crystallized 500 Å-thick a-Si in a few minutes without any thermal deformation of glass substrate. The size of crystallized silicon grain was abnormally big (30-40 μm). Polycrystalline thin film transistors (TFT) fabricated using this unique thin film heater showed better mobility than those of conventional ones by furnace annealing. 相似文献