全文获取类型
收费全文 | 943篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 42篇 |
综合类 | 2篇 |
化学工业 | 137篇 |
金属工艺 | 12篇 |
机械仪表 | 15篇 |
建筑科学 | 28篇 |
能源动力 | 20篇 |
轻工业 | 56篇 |
水利工程 | 12篇 |
石油天然气 | 1篇 |
无线电 | 90篇 |
一般工业技术 | 129篇 |
冶金工业 | 320篇 |
原子能技术 | 30篇 |
自动化技术 | 64篇 |
出版年
2022年 | 7篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 8篇 |
2014年 | 18篇 |
2013年 | 27篇 |
2012年 | 31篇 |
2011年 | 35篇 |
2010年 | 17篇 |
2009年 | 23篇 |
2008年 | 28篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 24篇 |
2004年 | 34篇 |
2003年 | 38篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 20篇 |
1999年 | 27篇 |
1998年 | 135篇 |
1997年 | 87篇 |
1996年 | 51篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 10篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1937年 | 1篇 |
1921年 | 1篇 |
排序方式: 共有958条查询结果,搜索用时 15 毫秒
71.
This work is concerned with computing the reliability of redundant systems of three-state (e.g., good, failed-open or failed-short) devices. Allowing for multiple failures, formulas are presented for calculating the reliability of a parallel-series system or a series-parallel system which is formed from three-state, non-DFM (dual failure-mode) devices, and which might require multiple paths to function. The words series and parallel are used in the layout-diagram sense. The formulation encompasses cases which have been analyzed by complex methods in numerous papers on the reliability of three-state DFM device systems. The effects of dominant failure-modes on the relationship between reliability of a series system and that of a parallel system, and on the relationship between the reliability of a parallel-series system and that of series-parallel system are presented 相似文献
72.
Voltage-dependent Ca2+ channels play a central role in controlling neurotransmitter release at the synapse. They can be inhibited by certain G-protein-coupled receptors, acting by a pathway delimited to the membrane. In addition, modulation of Ca2+ channel activity by protein kinases also contributes to the dynamic regulation of neuronal physiology. Recently, differences in these modulations between Ca2+ channel subtypes have been shown in several neuronal preparations. Here we show that two types of presynaptic Ca2+ channel (N-type and Q-type) are differentially regulated by cAMP and G-proteins using a Xenopus oocyte expression system. Treatment to increase cytosolic cAMP concentration with forskolin and 3-isobutyl-1-methylxanthine (IBMX) markedly potentiated Q-type channel current, and the enhancement was reversed by protein kinase A inhibitors. Much smaller enhancement was observed in N-type channel current after the cAMP elevation. When large depolarizing prepulse was applied to the oocytes for evaluation of the tonic inhibition of Ca2+ channels by intrinsic G-protein activity, N-type channel current elicited a large prepulse facilitation but Q-type channels did not. The tonic inhibition of N-type channels was abolished by an intracellular perfusion with a 'cut-open' recording configuration, or by co-expression with G(alpha o). When kappa opioid receptors were co-expressed and stimulated with agonists, depolarization-resistant inhibition was more apparent in Q-type channels than in N-type channels. These results suggest that Q-type channels are more susceptible to the protein kinase A-mediated facilitation than N-type channels, and that activity of N-type channels can be more highly regulated in a voltage-dependent manner by G(betagamma) than that of Q-type channels. These differences may account for the selective regulation of neurotransmitter release by these Ca2+ channels. 相似文献
73.
Homma T. Satoh A. Okada S. Itoh M. Yamaguchi M. Takahashi H. 《IEEE transactions on instrumentation and measurement》1998,47(3):698-702
Optical properties of fluorinated silicon oxide (SiOF) films for optical waveguide in optoelectronic devices were investigated. The SiOF films are formed at 25°C by a liquid phase deposition (LPD) technique using a supersaturated hydrofluosilicic acid (H2SiF 6) aqueous solution. Two main absorption peaks corresponding to Si-O and Si-F bonds were observed at the wavenumbers of 1090 and 930 cm-1 in Fourier transform infrared (FTIR) spectrum, respectively. The LPD-SiOF films show very little content of water components such as Si-OH bonds and OH group. Although the transmittance for 600-nm-thick LPD-SiOF film gradually decreased from the wavelength around 700 nm, the relative transmittances to quartz glass are over 98% in the wavelength region from 350-2500 nm. The concentration of fluorine atoms in the LPD-SiOF film was about 5%, and the calculated composition was SiO1.85F0.15. The calculated refractive index from the polarizability for LPD-SiOF film was 1.430, and agrees very well with the measured value at the wavelength of 632.8 nm by ellipsometry. The dispersion of refractive index was evaluated and fitted to a three-term Sellmeier's dispersion equation. The zero dispersion wavelengths for the LPD-SiOF and thermally grown SiO2 films were 1.271 and 1.339 μm, respectively 相似文献
74.
K Kobayashi M Endo H Nishida Y Tomizawa H Satoh H Koyanagi 《Canadian Metallurgical Quarterly》1998,46(9):878-881
The extramammary Paget's disease of anogenital area is rare, and is seen as a precancerous lesion or carcinoma in situ. In most cases, surgical treatment including dissection of regional lymph nodes, skin resection and grafting should be considered first. A 74-year-old male suffered from effort angina and underwent triple coronary artery bypass grafting (CABG) including saphenous vein graft (SVG) harvested from right lower leg. Five years previously he underwent skin grafting for extramammary Paget's disease of both inguinal areas and the perineal area. The postoperative course was uneventful and he was discharged 23 days after the CABG operation. Extramammary Paget's disease is localized in epidermis for years and there has been no report of direct invasion into vessels. Therefore, there appears to be no reason not to use an SVG if there is no luminal thrombus or occlusion. 相似文献
75.
Sanae Shimizu Kazuhiko Yamamoto Caihau Wang Yutaka Satoh Hideki Tanahashi Yoshinori Niwa 《Electrical Engineering in Japan》2005,152(3):29-38
Moving object detection with a mobile image sensor is an important task in robotics and computer vision, when considering the practical use of robotics in human environments. In this paper, we propose a robust method that detects moving objects in the environment using the omnidirectional depth information obtained by a mobile Stereo Omnidirectional System (SOS). In order to detect only the moving objects within the depth image that are obtained by a sensor in motion, we first estimate the ego‐motion of the sensor, and generate a predicted depth image for the current time from the depth obtained at the previous time by only considering the ego‐motion of the sensor. Then the predicted depth image is compared with the actual one obtained at the current time, and the inconsistent regions are detected as moving objects. When the sensor moves, occlusions will occur in the scene and they will cause false detections. However, these false detections can be suppressed by estimating the occlusion regions using the ego‐motion parameters of the sensor and the jump edges in the depth image. The effectiveness of the method is shown with experimental results for a real environment. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(3): 29–38, 2005; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20155 相似文献
76.
T Nagayama T Koshika H Hisa T Kimura S Satoh 《Canadian Metallurgical Quarterly》1997,327(2-3):135-141
Physical activity is defined as skeletal muscle contraction resulting in a quantifiable expenditure of energy, whereas exercise is a specific type of physical activity in which planned, structured, and repetitive bodily movement is done to improve or maintain one or more components of physical fitness. The focus of laboratory studies of the physical activity-breast cancer hypothesis has been on evaluating how various types of physical activity including exercise affect the process of mammary carcinogenesis. A key objective has been the evaluation of the characteristics of physical activity, i.e. intensity, duration, and frequency, required to confer protection against experimentally-induced breast cancer. The results of those studies indicate that exercise rather than physical activity can exert a greater inhibitory effect against experimentally-induced breast cancer, and that the duration of exercise may not be as important as its intensity. This finding differs from evidence that other health benefits attributed to physical activity are proportional to the total amount of activity rather than the manner in which it is obtained. In this review criteria are defined for categorizing laboratory studies into those that investigated the effects of physical activity versus exercise on experimentally-induced mammary carcinogenesis, and the literature is reinterpreted in this context. 相似文献
77.
Disseminated intra-abdominal cystic lymphangiomatosis with severe intestinal bleeding. A case report
A Iwabuchi M Otaka A Okuyama M Jin S Otani S Itoh H Sasahara M Odashima H Kotanagi M Satoh H Masuda O Masamune 《Canadian Metallurgical Quarterly》1997,25(1):383-386
We describe cystic lymphangiomatosis with intestinal bleeding developing multiple lymphangiomas in the small intestine, mesentery, mesocolon, omentum, retroperitoneum, and spleen. Small intestinal fluorography showed multiple polypoid lesions, mainly in the jejunum. Ultrasonography, computed tomography, and magnetic resonance imaging showed diffuse cystic tumors in the mesentery and spleen. Cystic lymphangiomatosis was proved by histologic findings of the biopsied specimen at laparotomy. 相似文献
78.
Yamanaka K. Nagata Y. Nakano S. Koda T. Nishino H. Tsukahara Y. Cho H. Inaba M. Satoh A. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1995,42(3):381-386
We present principle and application of a novel noncontact velocity measurement of surface acoustic waves (SAW) on crystals and thin films using laser interference fringes scanned at the phase velocity of SAW. The scanning interference fringes (SIF) are produced by intersecting two laser beams with a frequency difference. The SAW velocity within the laser beam spot is measured as the ratio of observed SAW frequency and predetermined wave number of the SIF. The frequency measurement can be quite precise because of a large number of generated SAW carriers and amplitude enhancement effect. The SAW velocity measurement is free from the water loading effect accompanying the leaky SAW measurements. This principle was successfully applied to evaluate Si 3N4 and SiO2 films deposited on Si (001) surface 相似文献
79.
High temperature stable GHz-range low-loss wide band transducersand filter using SiO2/LiNbO3, LiTaO3
Yamanouchi K. Satoh H. Meguro T. Wagatsuma Y. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1995,42(3):392-396
GHz-range low-loss transducers and filters are required for communication systems, especially mobile telephone communication systems. Many types of low insertion-loss transducers and filters utilizing the high electromechanical coupling coefficient (K2) materials such as LiNbO3 and LiTaO3 have been developed. Unfortunately, these materials have large temperature coefficients of the frequency (TCF). In this paper, SAW substrates with high coupling coefficients and low propagation attenuations and small temperature coefficient of frequency in the GHz-range are theoretically and experimentally investigated. The experimental results show very low propagation loss of 0.02 dB/λ 0 and larger K2 than those of the substrates of LiNbO3 and LiTaO3 at the TCF of below -5 ppm/°C at 1~2 GHz-range. The low-loss filter results using internal reflection types of IDT show the insertion loss of about 2.9 dB at 1 GHz and 4.9 dB at 2 GHz under the TCF's of 0 and +20 ppm/°C. These materials are applicable for devices at GHz-range because SiO2 thickness is very thin such as below 1 μm and the center frequency shift of the filter versus SiO2 thickness is very small 相似文献
80.
S Matsukawa JH Suh Y Hashimoto M Kato D Satoh S Saito K Endo T Saishu 《Canadian Metallurgical Quarterly》1997,181(4):471-473
In children with immune thrombocytopenic purpura (ITP), bone marrow lymphocytes can express the common acute lymphoblastic leukemia antigen (CALLA) pattern with no evidence of leukemia or lymphoma. Bone marrow lymphocytes from 23 children and 20 adults affected with ITP were studied to determine the incidence and the clinical impact of lymphocytes with the immature B-cell phenotype and CD34+ cell expression. In this investigation we identified a group consisting of 52% of the children who showed the immature B phenotype, while the remaining 48%, similarly to adult ITP displayed an increase of T-cell antigens. CD34 was positive in 53% of children, but it was present in only half of the patients with the immature B phenotype and it was always absent in adults. IgH genes disclosed a germline configuration in all six patients in the immature B phenotype group. No difference was found in the two groups of children in terms of age, presentation of the disease or final outcome. Finally, no patient in either children's group has developed an acute lymphoproliferative disorder. 相似文献