首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   134篇
  免费   2篇
电工技术   18篇
化学工业   16篇
金属工艺   4篇
机械仪表   2篇
建筑科学   2篇
能源动力   9篇
轻工业   10篇
水利工程   1篇
无线电   12篇
一般工业技术   17篇
冶金工业   30篇
原子能技术   3篇
自动化技术   12篇
  2023年   2篇
  2021年   3篇
  2018年   1篇
  2017年   2篇
  2016年   4篇
  2015年   1篇
  2014年   5篇
  2013年   9篇
  2012年   9篇
  2011年   3篇
  2010年   1篇
  2009年   5篇
  2008年   5篇
  2007年   3篇
  2006年   12篇
  2005年   3篇
  2004年   7篇
  2003年   1篇
  2002年   4篇
  2001年   6篇
  2000年   1篇
  1999年   1篇
  1998年   15篇
  1997年   8篇
  1996年   5篇
  1995年   3篇
  1994年   4篇
  1992年   4篇
  1991年   1篇
  1986年   1篇
  1985年   2篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
  1976年   1篇
  1975年   1篇
排序方式: 共有136条查询结果,搜索用时 15 毫秒
1.
A BiCMOS logic circuit applicable to sub-2-V digital circuits has been developed. A transiently saturated full-swing BiCMOS (TS-FS-BiCMOS) logic circuit operates twice as fast as CMOS at 1.5-V supply. A newly developed transient-saturation technique, with which bipolar transistors saturate only during switching periods, is the key to sub-2-V operation because a high-speed full-swing operation is achieved to remove the voltage loss due to the base-emitter turn-on voltage. Both small load dependence and small fan-in dependence of gate delay time are attained with this technique. A two-input gate fabricated with 0.3-μm BiCMOS technology verifies the performance advantage of TS-FS-BiCMOS over other BiCMOS circuits and CMOS at sub 2-V supply  相似文献   
2.
This paper presents a single lossless inductive snubber‐assisted ZCS‐PFM series resonant DC‐DC power converter with a high‐frequency high‐voltage transformer link for industrial‐use high‐power magnetron drive. The current flowing through the active power switches rises gradually at a turned‐on transient state with the aid of a single lossless snubber inductor, and ZCS turn‐on commutation based on overlapping current can be achieved via the wide range pulse frequency modulation control scheme. The high‐frequency high‐voltage transformer primary side resonant current always becomes continuous operation mode, by electromagnetic loose coupling design of the high‐frequency high‐voltage transformer and the magnetizing inductance of the high‐frequency high‐voltage transformer. As a result, this high‐voltage power converter circuit for the magnetron can achieve a complete zero current soft switching under the condition of broad width gate voltage signals. Furthermore, this high‐voltage DC‐DC power converter circuit can regulate the output power from zero to full over audible frequency range via the two resonant frequency circuit design. Its operating performances are evaluated and discussed on the basis of the power loss analysis simulation and the experimental results from a practical point of view. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 79–87, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20126  相似文献   
3.
The intercalation reaction of n-alkylamines from methyl- to hexadecylamine into -tin(IV) bis(hydrogenphosphate) has been investigated. The reaction was conducted by mixing the phosphate and solutions of the amines dissolved in water or benzene. The amine/ phosphate molar ratios in the reaction mixtures were 0.43, 0.85, 1.71 and 3.41. The nitrogen/phosphorus atomic ratio in the intercalation compound was not changed by the amine/phosphate molar ratio. The interlayer distances of the intercalates obtained in the reaction mixtures with molar ratios of 3.41 and 1.71 increased with an increase in the number of carbon atoms in the alkyl chain of the amine. The slope of the straight line obtained in plot of interlayer distance versus number of carbon atoms in the alkyl chain of the amine indicates that the amine molecules form a double layer in the interlayer space of the phosphate and are inclined at an approximate angle of 67.7° to the phosphate layer. The interlayer distances of the intercalates of butyl- to nonylamines obtained at the molar ratio of 0.85 are smaller than those of the corresponding compounds from the molar ratios of 3.41 and 1.71, while those of decyl- to hexadecylamine intercalates lie on the previously discussed line. This behaviour is interpreted by assuming kink formation in the short alkyl chains between the phosphate layers.  相似文献   
4.
We carried out77Se NMR measurements on BETS2(Cl2TCNQ) under pressure in order to investigate the magnetic properties of the insulating state which appears above 0.6 GPa. The relaxation rate 1/T1 at 0.7 GPa shows small peak-like anomaly at 20 K, indicating a spin density wave transition as observed in BETS2(Br2TCNQ).  相似文献   
5.
The moisturizing effect of vesicles formed from monoglycerides on human skin was studied by measurement of conductance on and transepidermal waterloss from the skin surface. Although sonication of the monoglycerides in water with Ca2+ gave multilamellar vesicles, the lamellar structure of the vesicles disappeared during their storage without any other additive. With the addition of poly(vinylpyrrolidone) after the sonication, the stability of the vesicles increased and their lamellar structure was maintained for 3 months at 40 degrees C. These vesicles led to a significantly higher water content of the stratum corneum of human skin compared with non-lamellar monoglyceride, and consequently they improved rough human skin.  相似文献   
6.
A numerical simulation has been performed to clarify the effects of turbulence in a liquid on the deformation of the liquid jet surface into an air flow. The turbulences in the liquid jet were simulated by the Rankin vortices, and the liquid jet surface was tracked numerically by the volume of fluid method. By numerical simulations, the onset of the protrusions on the liquid jet surface is caused by the vortices in the liquid, and the surrounding air flow plays an important role in the amplification of the protrusions. The amplification rate of the trough displacement is proportional to the air‐to‐liquid velocity ratio. At large imposed vortex intensities, the trough displacement increases with the vortex intensity. On the other hand, at small imposed vortex intensities, the amplification of the trough displacement is also affected by factors other than vortex intensity. © 2001 Scripta Technica, Heat Trans Asian Res, 30(6): 473–484, 2001  相似文献   
7.
Endothelin (ET) and its receptor system have been shown to exert various biological effects on different types of cells in addition to their well-known vasoconstrictor activity. Recently ET-1, ET-3 and the ETB receptor have been shown to play an important role in the development of neural crest-derived cells and, in this context, pheochromocytomas have been reported to harbor ET-1. Endothelin-3 or ET receptor subtypes, however, have not been examined in pheochromocytoma and paraganglioma so far. In the present study the immunohistochemical localization of ET-1/big ET-1, ET-3/big ET-3 and the ETA and ETB receptors were investigated to clarify the biological characteristics of these two tumors using 32 pheochromocytomas and 11 extra-adrenal paragangliomas. Endothelin-1/big ET-1 was detected in 19 pheochromocytomas (59%) and eight paragangliomas (72%), while ET-3/big ET-3 was detected in 10 pheochromocytomas (31%) and three paragangliomas (27%). The ETA receptor was found in 21 pheochromocytomas (66%) and in eight paragangliomas (73%), while the ETB receptor was found in 25 pheochromocytomas (78%) and in eight paragangliomas (73%). Normal adrenomedullary cells lacked each antigen examined. Endothelin-immunoreactive tumor cells were distributed focally or in a manner scattered, while receptor-immunostained tumor cells were distributed with a focal pattern for the ETA receptor and with a focal or diffuse pattern for the ETB receptor. Endothelin and its receptor coexisted in the same tumor in 21 of 28 ET-positive pheochromocytomas and in eight of 10 ET-positive paragangliomas. In addition, seven pheochromocytomas and two paragangliomas revealed positivity of the receptor(s) irrespective of the absence of ET-immunoreactivity. In conclusion, ET and its receptor are frequently and concomitantly expressed in the pheochromocytoma and paraganglioma. From the highly frequent expression of this system or the receptor(s), ET-receptor-mediated signal transduction of these tumors concerning growth and/or cell survival is expected, although definite biological significance of this ligand-receptor system in these tumors awaits further investigation.  相似文献   
8.
9.
10.
Bone biopsy is necessary for the diagnosis of ambiguous skeletal lesions. Although several merits of computed tomography (CT)-guided percutaneous needle biopsy have been documented, few radiologists have performed this procedure in Japan. We performed this procedure with a newly introduced bone biopsy needle (OSTYCUT, angiomed, Karlsruhe, Germany) under CT guidance and evaluated the results. CT-guided bone biopsy (pelvic[n = 11]vertebral[n = 10], femoral[n = 1], sternal[n = 1]) was performed in 19 consecutive patients. Seventeen patients were suspected metastatic disease, and the others were suspected primary bone tumor. All biopsies but one were diagnostic. Malignancy was proved in 11 lesions. Three patients with prostatic carcinoma were proved to show no malignancy of bone lesions after a series of hormonal and chemotherapies. In one patient with both malignant mesothelioma and cervical carcinoma, the biopsy specimen from thoracic vertebra proved metastasis from mesothelioma. CT-guided bone biopsy is useful to evaluate the presence of malignancy and the effect of therapy for it, and to determine the primary site.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号