全文获取类型
收费全文 | 309篇 |
免费 | 9篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 66篇 |
金属工艺 | 1篇 |
机械仪表 | 4篇 |
建筑科学 | 3篇 |
能源动力 | 8篇 |
轻工业 | 9篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 43篇 |
一般工业技术 | 64篇 |
冶金工业 | 77篇 |
原子能技术 | 2篇 |
自动化技术 | 19篇 |
出版年
2023年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 1篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 8篇 |
2012年 | 5篇 |
2011年 | 15篇 |
2010年 | 7篇 |
2009年 | 7篇 |
2008年 | 13篇 |
2007年 | 11篇 |
2006年 | 9篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 2篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 29篇 |
1997年 | 29篇 |
1996年 | 12篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有318条查询结果,搜索用时 15 毫秒
251.
Video abstraction is defined as creating a video abstract which includes only important information in the original video
streams. There are two general types of video abstracts, namely the dynamic and static ones. The dynamic video abstract is a 3-dimensional representation created by temporally arranging important scenes while
the static video abstract is a 2-dimensional representation created by spatially arranging only keyframes of important scenes.
In this paper, we propose a unified method of automatically creating these two types of video abstracts considering the semantic
content targeting especially on broadcasted sports videos. For both types of video abstracts, the proposed method firstly
determines the significance of scenes. A play scene, which corresponds to a play, is considered as a scene unit of sports videos, and the significance of every play scene is
determined based on the play ranks, the time the play occurred, and the number of replays. This information is extracted from
the metadata, which describes the semantic content of videos and enables us to consider not only the types of plays but also their influence
on the game. In addition, user’s preferences are considered to personalize the video abstracts. For dynamic video abstracts,
we propose three approaches for selecting the play scenes of the highest significance: the basic criterion, the greedy criterion,
and the play-cut criterion. For static video abstracts, we also propose an effective display style where a user can easily
access target scenes from a list of keyframes by tracing the tree structures of sports games. We experimentally verified the
effectiveness of our method by comparing our results with man-made video abstracts as well as by conducting questionnaires.
相似文献
Noboru BabaguchiEmail: |
252.
Viscoelastic nonlinearity was examined on uniaxially drawn films of high density and linear low density polyethylenes and their blends using dynamic ultrasonic measurements. It was found that nonlinearity due to plastic deformations, such as slippage and dislocations, occurs in the fibrous structures. Plastic deformations were different from those in corresponding undrawn films. For undrawn films, the formation and/or deformation of crystal defects and voids were caused by the disruption of spherulitic structures. Nonlinearity was smaller for drawn films than for undrawn films, suggesting that the superstructure of drawn films is more uniform and more stable for mechanical deformations. 相似文献
253.
Tomoshige Nitta Shinobu Takeuchi Takashi Katayama 《Chemical engineering science》1974,29(11):2213-2218
The continuous linear association model of the Kretschmer—Wiebe type is used to examine the effects of self-association on liquid-liquid equilibria. The results of the calculation show that the self-association enhances the phase separation and decreases the mole fraction of the self-associating component in a binary mixture at the critical solution point. The application of the theory to the binary systems of methanol—saturated hydrocarbons has yielded good correlations for both the critical solution points and the mutual solubilities at temperatures below the critical. The values of the association constant and enthalpy obtained for methanol are 1030 at 25°C and ?3·5 kcal/mol, respectively. The temperature dependence of the physical interaction parameter for each hydrocarbon is represented by a reduced form. The applicabilities of the theory to both vapour—liquid and liquid—liquid equilibria are better than those of NRTL equation for the systems of methanol—saturated hydrocarbons. 相似文献
254.
When polymer blends are foamed by physical foaming agents, such as CO2 or N2, not only the morphology and viscosity of the blend polymers but also the solubility and diffusivity of the physical foaming agents in the polymers determine the cellular structure: closed cell or open cell and monomodal or bimodal. The foam of poly(ethylene glycol) (PEG)/polystyrene (PS) blends shows a unique bimodal (large and small) cellular structure, in which the large‐size cells embrace a PEG particle. Depending on the foaming condition, the average size of the large cells ranges from 40 to 500 μm, whereas that of small cells becomes less than 20 μm, which is smaller than that of neat PS foams. The formation mechanism of the cellular structure has been investigated from the viewpoint of the morphology and viscosity of the blend polymer and the mass‐transfer rate of the physical foaming agent in each polymer phase. The solubility and diffusivity of CO2, which determine the mass‐transfer rate of CO2 from the matrix to the bubbles, were measured by a gravimetric measurement, that is, a magnetic suspension balance. The solubility and diffusivity of CO2 in PS differed from those in PEG: the diffusion coefficient of CO2 in PEG at 110°C was 3.36 × 10?9 m2/s, and that in PS was 2.38 × 10?10 m2/s. Henry's constant in PEG was 5600 cm3 (STP)/(kg MPa) at 110°C, and that in PS was 3100 cm3 (STP)/(kg MPa). These differences in the transport properties, morphology of the blend, and CO2‐induced viscosity depression are the control factors for creating the unique cellular structure in PEG/PS blends. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1899–1906, 2005 相似文献
255.
A multiwavelength laser source composed of a single semiconductor optical amplifier and a commercially available off-the-shelf wavelength-division multiplexed (WDM) filter is constructed and tested under actively mode-locking operation. Five independent mode-locked wavelength channels are generated simultaneously, with a wavelength spacing of 1.6 nm established by the WDM filter. In addition, to demonstrate the potential of this mixed time-frequency, or hybrid WDM-optical time-division multiplexed, signal, we demonstrate a simple parallel-to-serial wavelength conversion to increase the pulse repetition rate of the mode-locked laser by a number of output wavelengths for applications in high-performance optical sampling applications. 相似文献
256.
257.
Nitta A Shirasuna K Haneda S Matsui M Shimizu T Matsuyama S Kimura K Bollwein H Miyamoto A 《Reproduction (Cambridge, England)》2011,142(6):879-892
The corpus luteum (CL), which secretes large amounts of progesterone and is thus essential for establishing pregnancy, contains various types of immune cells that may play essential roles in CL function by generating immune responses. The lymphatic system is the second circulation system and is necessary for immune function, but the lymphatic system of the bovine CL has not been characterized in detail. We collected bovine CLs on days 12 and 16 of the estrous cycle (C12 and C16) and days 16 and 40 of early pregnancy (P16 and P40). Lymphatic endothelial hyaluronan receptor 1 (LYVE1) protein was detected in the CL by immunohistochemistry and western blotting and increased at P40 compared with C16. The mRNA expression levels of lymphangiogenic factors, such as vascular endothelial growth factor-C (VEGFC), VEGFD, and their common receptor VEGFR3, as well as the lymphatic endothelial cell (LyEC) marker podoplanin, increased in P16 and P40 CLs. Thus, it is suggested that the lymphatic system of the bovine CL reconstitutes during early pregnancy. Interferon tau (IFNT) from the conceptus in the uterus is a candidate for activating luteal lymphangiogenesis during the maternal recognition period (MRP). We found that treatment of LyECs isolated from internal iliac lymphatic vessels with IFNT stimulated LyEC proliferation and significantly increased mRNA expression of VEGFC and IFN-stimulated gene 15. Moreover, both IFNT and VEGFC induced LyECs to form capillary-like tubes in vitro. In conclusion, it is suggested that new lymphangiogenesis in the bovine CL begins during the MRP and that IFNT may mediate this novel phenomenon. 相似文献
258.
Delfyett P.J. Hong Shi Gee S. Nitta I. Connolly J.C. Alphonse G.A. 《Quantum Electronics, IEEE Journal of》1999,35(4):487-500
Joint time-frequency ultrafast measurements using frequency-resolved optical gating (FROG) have been used to provide a fundamental understanding of: (1) ultrashort pulse propagation in semiconductor optical amplifiers; (2) the modelocking dynamics in external cavity semiconductor diode lasers; and (3) correlated multiple-wavelength generation from mode locked semiconductor lasers. The pulse shaping and chirping effects measured by FROG are shown to be attributed to intracavity gain and saturable absorbing dynamics, as well as group velocity dispersion. In addition, the intracavity gain dynamics show a regime of transient unsaturated gain, which can be exploited to allow phase-correlated multiple-wavelength modelocked operation from a single-stripe external-cavity semiconductor diode laser. In this case, FROG techniques are used to understand the underlying mechanisms involved in the phase correlation process 相似文献
259.
High-speed bus circuits are the key to high performance systems with built-in processors. However, conventional bus circuits with low power consumption suffer problems such as ringing and dips caused by reflection and, as a result, the bus transmission rate cannot reach 100 MHz. Lattice diagrams have been used to analyze bus circuits, but these only show the approximate reflection behavior and cannot graphically portray the relation between reflection timing and waveform distortion due to reflection. This paper introduces a bus circuit with non-power-consuming termination that can achieve data transmission speeds over 100 MHz, 2.5 to 3 times faster than conventional low-power bus circuits. The paper also proposes a newly devised lattice diagram that can graphically clarify the relation between reflection timing and waveform distortion due to reflection. A SPICE simulation was carried out to examine the data transmission rate for each bus circuit. It was experimentally confirmed that our bus circuit, with non-power-consuming termination, operates at a 167-MHz data transmission rate. © 1998 Scripta Technica. Electr Eng Jpn, 122(1): 49–59, 1998 相似文献
260.
Yuriko Nitta Tomohiro Fujimatsu Yasuaki Okamoto Toshinobu Imanaka 《Catalysis Letters》1993,17(1-2):157-165
Starting salts used in the co-precipitation of Cu-ZrO2 precursors had marked influence on both activity and selectivity of resulting catalysts for methanol synthesis: chlorides increased the selectivity, suggesting the structure sensitivity of methanol formation reaction, while sulfates much enhanced the activity by affecting the dispersion of Zr species. A simultaneous use of copper chloride and zirconium sulfate greatly improved the activity and selectivity of the catalyst for methanol formation. 相似文献