全文获取类型
收费全文 | 2136篇 |
免费 | 128篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 37篇 |
综合类 | 2篇 |
化学工业 | 466篇 |
金属工艺 | 81篇 |
机械仪表 | 62篇 |
建筑科学 | 47篇 |
能源动力 | 68篇 |
轻工业 | 103篇 |
水利工程 | 1篇 |
石油天然气 | 4篇 |
无线电 | 396篇 |
一般工业技术 | 436篇 |
冶金工业 | 228篇 |
原子能技术 | 28篇 |
自动化技术 | 317篇 |
出版年
2023年 | 5篇 |
2022年 | 21篇 |
2021年 | 21篇 |
2020年 | 25篇 |
2019年 | 25篇 |
2018年 | 48篇 |
2017年 | 46篇 |
2016年 | 46篇 |
2015年 | 50篇 |
2014年 | 70篇 |
2013年 | 183篇 |
2012年 | 99篇 |
2011年 | 131篇 |
2010年 | 119篇 |
2009年 | 119篇 |
2008年 | 126篇 |
2007年 | 107篇 |
2006年 | 75篇 |
2005年 | 68篇 |
2004年 | 62篇 |
2003年 | 71篇 |
2002年 | 47篇 |
2001年 | 46篇 |
2000年 | 55篇 |
1999年 | 68篇 |
1998年 | 103篇 |
1997年 | 51篇 |
1996年 | 45篇 |
1995年 | 43篇 |
1994年 | 37篇 |
1993年 | 30篇 |
1992年 | 17篇 |
1991年 | 24篇 |
1990年 | 13篇 |
1989年 | 24篇 |
1988年 | 18篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 6篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 5篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有2276条查询结果,搜索用时 15 毫秒
101.
Shih‐Chien Chou 《中国工程学刊》2013,36(2):323-330
Abstract This paper proposes a label‐based information flow control model to prevent information leakage within object‐oriented systems. It offers the features of: (a) adapting to dynamic object state change, (b) adapting to dynamic role change, (c) preventing indirect information leakage, (d) detailing the control granularity to variables, (e) allowing purpose‐oriented method invocation, (f) controlling method invocation through argument sensitivity, (g) allowing declassification, and (h) allowing only trusted sources to write a variable. 相似文献
102.
Changes during project execution frequently require schedule updating and rescheduling. However, few studies have discussed rescheduling issues or implemented rescheduling solutions for construction projects. This study investigates resource-constrained construction rescheduling issues using concepts associated with manufacturing rescheduling. Based on an initial schedule and actual progress, a novel rescheduling optimization model using Constraint Programming (CP) techniques is developed to reschedule projects. Two rescheduling methods: (1) complete regeneration (CR); and, (2) partial rescheduling (PR) while minimizing overall project variation are implemented in the proposed model to demonstrate the model capability and applications. PR requiring additional treatments to decrease overall project variation is performed using a novel constraint-release mechanism. Finally, using a case study, optimization results obtained using two rescheduling methods are analyzed and discussed. 相似文献
103.
Li-Cheng Jheng Chun-Yen Yang Ming-Tsong Leu Keng-Hao Hsu Jyh-Horng Wu Jrjeng Ruan Kuo-Chen Shih 《Polymer》2012,53(13):2758-2768
For studied blends of amorphous glycol-modified poly(ethylene terephthalate) (PETG) and semicrystalline polyethylene naphthalate (PEN), melt miscibility is understood from the linear variation of a single glass transition temperature (Tg) over the entire composition range. The diluent effect of PETG component severely retarded the crystallization of PEN component within blends. Nevertheless, after being through isothermal stretching at 120 °C, crystallization was able to progress efficiently during heating in a continuous manner. Instead of being thermally relaxed back to amorphous state, parallel sliding motions of stretched PEN segments toward crystallization appear rather dominant. Within stretched blends, the PETG content emerged as a critical factor to the crystallinity increase of PEN fraction and the absence of lattice defect, instead of behaving as a diluent component. Furthermore, as being indicated by in-situ small-angle X-ray experiments, regular lamellar stacking gradually developed within stretched blends through heating, which indicates the involvement of thermally activated self-association of randomly distributed crystalline lamellae. With including a higher fraction of PETG component, these secondary ordering processes including lamellar thickening can be activated at lower temperature. Hence, the accompanied thermal relaxation of flexible PETG segment is inferred able to lubricate the sliding of stretched PEN segments in amorphous regions via lowering encountered frictional hindrance, and thus enhance both primary and secondary ordering processes within stretched blends. 相似文献
104.
105.
Chien-Yin Lai Pai-Hsun Chen Sheng-Wen Shih Yili Liu Jen-Shin Hong 《International journal of human-computer studies》2010,68(1-2):41-56
This article describes computational models based on principles of visual weights to compute the symmetry and balance of text-overlaid images. Two experiments were conducted to investigate the effects of symmetry and balance on the aesthetic appeal of text-overlaid images. In the first experiment, five color photos were used to compose a set of test images overlaid with a paragraph of Chinese texts as the stimuli. Contrastly, the second experiment applied monochrome photos to compute the stimuli. The positions of the text overlay were determined by varying the balance and symmetry in order to validate computational aesthetic quantification algorithms with subjective ratings. The stimuli were rated by 20 subjects in each experiment using the ratio-scale magnitude estimation method against a benchmark image for each photo. Results from both experiments show that subjects are adept at judging symmetry and balance in both the horizontal and vertical directions. Subjects are also adept at judging radial symmetry about the center point of an image. The experiments also established a relationship between a higher averaged visual balance and the aesthetic appeal of text-overlaid images. Symmetry in either direction, however, did not result in any proportional relations to the aesthetic appeal. 相似文献
106.
The scaleup behavior of blends exhibiting phase inversion during compounding in batch mixers was studied. Similar morphological changes were observed during compounding of polystyrene/polyethylene blends of different batch sizes ranging from 12g to 240g. The time to achieve a continuous phase of the major component, polystyrene, was shown to depend on the scale of the mixing device. Based on visual observation of the morphological changes, a constant nominal‐maximum‐shear‐rate scaleup condition was used. Upon a five‐fold increase in batch size the time to phase inversion increased by a factor of 3. This change is explained using a combination of the reduced specific area and reduced mechanical energy input under the experimental conditions. A novel blade design using modular triangular elements was constructed and results from radial and axial scaleup using the new blades are presented. Similarities between the triangular and roller blades are used to highlight the importance of the high‐shear region in determining the softening rate of the polystyrene pellets. The flexibility of the blade design was exploited to study the effect of blade configuration on the time to phase inversion. A relative stagger parameter is introduced to explain the observed dependence. Increasing the relative stagger decreased the stress transfer to the batch and increased the time to phase inversion. Implications of these results for mixing in the kneading sections of twin‐screw extruders is discussed. 相似文献
107.
Moon Gi Cho Sung K. Kang Sun-Kyoung Seo Da-Yuan Shih Hyuck Mo Lee 《Journal of Electronic Materials》2009,38(11):2242-2250
The effects of the addition of Zn to Sn-0.7Cu solders are investigated. The study is focused on the interfacial reactions,
microstructures, and mechanical properties after reaction with Ni-P under bump metallurgies (UBMs). The Zn contents in Sn-0.7Cu-xZn are varied as 0.2, 0.4, and 0.8 (in wt.% unless otherwise specified). In the reaction with Ni-P UBM during thermal aging
at 150°C for 1000 h, (Cu,Ni)6Sn5 intermetallic compounds (IMCs) are formed at the Sn-0.7Cu/UBM interface, whereas Zn is incorporated into IMCs to form (Cu,Ni,Zn)6Sn5 in the Zn-doped solders. As the Zn content increases, the interfacial IMC thickness is reduced. A total reduction of about
40% in IMC thickness was observed for the 0.8% Zn-doped Sn-Cu. The same IMC particles are also observed in the matrix of each
solder. In Sn-0.7Cu, (Cu,Ni)6Sn5 particles are coarsened during aging, while (Cu,Ni,Zn)6Sn5 particles in the Zn-added solders are less coarsened and remain much smaller than (Cu,Ni)6Sn5. The growth rate of (Cu,Ni)6Sn5 during thermal aging is significantly suppressed by the addition of Zn. Consequently, after reaction with Ni-P UBM, the Zn-doped
solders exhibit a thermally stable microstructure as measured by hardness and shear strength. 相似文献
108.
Chun-Kuo Liu Chia-Te Hu Yu-Hsiang Yang Yee-Shyi Chang Han C. Shih 《Diamond and Related Materials》2009,18(2-3):345-350
In this work, high-quality SWCNTs were synthesized by pyrolysis of ethanol at 900 °C in a tubular furnace. The catalyst was manufactured by depositing Fe and Mo metal on the surface of sol–gel MgO nanopowder. The SWCNTs produced by sol–gel MgO nanopowder have better yield, higher purity, and smaller diameters than those produced by commercial milling MgO powder. The lengths of SWCNTs are up to several microns with diameters in the range of 0.73–1.40 nm. The extremely small turn-on field Eto (0.01 V/μm) and threshold field Eth (0.07 V/μm) show that the SWCNTs have potential applications in field emission displays (FEDs). 相似文献
109.
Ashish C Gandhi Hsuan-Jung Hung Po-Hsun Shih Chia-Liang Cheng Yuan-Ron Ma ShengYun Wu 《Nanoscale research letters》2010,5(3):581-586
In this work, we succeeded in preparing in-plane zinc oxide nanowires using a Ti-grid assisted by the chemical vapor deposition method. Optical spatial mapping of the Confocal Raman spectra was used to investigate the phonon and geometric properties of a single ZnO nanowire. The local optical results reveal a red shift in the non-polar E2 high frequency mode and width broadening along the growth direction, reflecting quantum-confinement in the radial direction. 相似文献
110.
Chia-Te Hu Chun-Kuo Liu Meng-Wen Huang Sen-Hong Syue Jyh-Ming Wu Yee-shyi Chang Jien-W. Yeh Han-C. Shih 《Diamond and Related Materials》2009,18(2-3):472-477
Carbon nanotubes (CNTs) have been fabricated by microwave plasma-enhanced chemical vapor deposition for detecting the presence of ethanol vapor. The conductance of the CNTs decreases when the sensors are successively exposed to ethanol vapor at room temperature. The surface of the CNTs was modified in oxygen plasma to elevate the detection sensitivity for ethanol. Successful utilization of CNTs in gas sensors may open a new window for the development of novel nanostructure gas devices. 相似文献