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   253篇
  免费   2篇
电工技术   31篇
化学工业   38篇
金属工艺   2篇
机械仪表   5篇
建筑科学   5篇
能源动力   3篇
轻工业   9篇
水利工程   2篇
无线电   34篇
一般工业技术   23篇
冶金工业   83篇
原子能技术   4篇
自动化技术   16篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2019年   2篇
  2016年   2篇
  2014年   1篇
  2013年   6篇
  2012年   7篇
  2011年   8篇
  2010年   4篇
  2009年   2篇
  2008年   9篇
  2007年   7篇
  2006年   2篇
  2005年   5篇
  2004年   4篇
  2003年   5篇
  2002年   6篇
  2001年   6篇
  2000年   6篇
  1999年   11篇
  1998年   31篇
  1997年   25篇
  1996年   11篇
  1995年   8篇
  1994年   6篇
  1993年   20篇
  1992年   4篇
  1991年   3篇
  1990年   6篇
  1988年   3篇
  1987年   5篇
  1986年   5篇
  1985年   1篇
  1984年   5篇
  1983年   3篇
  1982年   4篇
  1981年   1篇
  1980年   4篇
  1979年   1篇
  1977年   1篇
  1976年   2篇
  1968年   1篇
  1967年   3篇
  1966年   2篇
  1965年   2篇
排序方式: 共有255条查询结果,搜索用时 9 毫秒
71.
A 90° sector type spin rotator was developed for measurement of the z-direction component of a spin polarization, which is parallel to the emitter axis. The rotator enables us to measure all components of electron spins field-emitted from a single crystalline magnetite. In-plane component of spin polarization dominated of field-emitted electrons from single crystalline magnetite whisker, thus it is suggested that the magnetization of the magnetite whisker results from the anisotropy of crystalline structure rather than its shape.  相似文献   
72.
Sticker systems with complex structures   总被引:3,自引:0,他引:3  
 In this paper, we propose a variant of sticker systems which uses molecules with complex structures. Since the original sticker systems (Paun et al. (1998) [2, 8]) working on double strands of DNA have been studied as a formal model for self-assembly in DNA computing, we extend the sticker systems to working on more complex (higher-order) structures of DNA molecules. The advantage of sticker systems with complex structures is that augmented with weak codings we can obtain the characterization of recursively enumerable languages by using only sticking (hybridization) operations for complex molecules, while the usual sticker systems require more complicated operations such as the simultaneous use of couples of dominoes or coherent computations besides morphisms.  相似文献   
73.
The structure of endothelin-1 (ET-1), an endothelial cell-derivedpeptide with vasoconstricting activity, was determined in anaqueous solution by means of a combination of NMR and distancegeometry calculations. The resulting structure is characterizedby an -helical conformation in the sequence region, Lys9-Cys15.Furthermore, an extended structure and a turn structure existin the Cys1-Ser4 and Ser5-Asp8 regions respectively, and nopreferred conformation was found for the C-terminal part ofthe peptide which was not uniquely constrained by the NMR data.These structural elements, the -helical structure in the sequenceportion, Cys-X-X-X-Cys, and the extended structure in Cys-X-Cys,are homologous to those found commonly in several neurotoxicpeptides.  相似文献   
74.
A high-gain and high-efficiency slotted waveguide planar antenna is developed in the millimeter-wave band. Forty-five degree inclined polarization is required for automotive radar systems. In the design of slotted waveguide array for arbitrarily linear polarization, slot spacing is one guide wavelength which is larger than a wavelength in free space. Consequently, grating lobes appear in the radiation pattern. So, we developed a slotted waveguide planar antenna composed of post-loaded narrow-wall slots and a single-layer alternating-phase feeding circuit. A planar antenna with suppressed grating lobes has been fabricated and its RF performance has been measured. The measured gain is 33.2 dBi and antenna efficiency is 56% at 76 GHz. Grating lobe level is -28.6 dB lower than main lobe level. Since the proposed structure remains simple, the antenna is expected to be manufactured by metal injection molding for low cost  相似文献   
75.
The effects of ultrasonic irradiation during milk fermentation have been investigated in terms of the cell viability, β-galactosidase activity, the pH value of the culture medium, the degree of lactose hydrolysis and glucose content. The results showed that the ultrasonic irradiation caused the intracellular β-galactosidase to be released from the lactic acid bacteria cells. The released β-galactosidase showed a higher lactose hydrolysis activity than that in the cells. The β-galactosidase that was released to the medium has been more effectively used in pH-controlled fermentation. The results also showed that the continuous sonication caused the cell viability to decrease, but the viable cell count was again increased with static incubation after sonication. High degrees of lactose hydrolysis and high cell viabilities were obtained with the combination of pH-controlled sonicated fermentation and static incubation.  相似文献   
76.
77.
It has been reported that the capture effect can improve the performance of slotted ALOHA systems. Further improvement can be expected when the number of base stations is increased. The performance of such slotted ALOHA systems with multiple base stations is analyzed with the aid of the equilibrium point analysis. Not only the capture effect but also the packet dropping due to the finite number of retransmission trials are taken into account. The numerical results indicate that the finite number of retransmission trials mainly contributes to the improvement of the packet dropping probability in the range of the light input traffic, while the number of base stations mainly contributes to the improvement of the overall throughput and the average transmission delay in the range of the heavy input traffic  相似文献   
78.
In order to survey patients' views on disease and treatment information that should be provided at hospitals, an anonymous self-administered questionnaire was distributed to patients at Aichi Cancer Center Hospital in 1995. All eligible first-visit outpatients (97 persons), randomly selected revisit outpatients (99 persons; about one in ten refused), and all except six eligible inpatients in good condition at discharge (97 persons) responded. Out of 293 patients (115 males, 174 females and 4 unspecified), 74% answered that they wanted to be informed of their diagnosis irrespective of circumstances, 20% answered that they would want to be informed only in certain circumstances, and 2% did not want to be informed at all. There were no significant differences in response among the three sources of patients. Inpatients wanted more (81%) to be explained about recommended therapy than either first-visit outpatients (67%) or revisit outpatients (67%). The majority considered that about a 30-minute explanation was needed using pamphlet-like written materials or video. When asked what information was needed when choosing a cancer hospital, 71% specified information on the specialty of the hospital, 57% the content of the care provided, 23% the name and specialty of the doctors, 20% the waiting period before scheduled admission, 13% the average admission period, 11% the number of patients with the same disease, 10% the waiting time at the outpatient clinic, 6% the meal menu, and 4% the number of private wards. Forty-three percent wanted an information service covering all hospitals in the region through an information center. The results revealed that patients at this cancer hospital required information on their disease, treatment, and hospital specialty.  相似文献   
79.
A slotted waveguide planar array using a single-layer feed circuit is proposed for high-frequency and high-gain antennas. The high efficiency of 75.6% and the gain of 35.9 dBi are obtained in the 22 GHz band, which confirms the potential of this type of antenna. The antenna consists of only two components, a slotted plate and a groove feed structure, and can be mass produced  相似文献   
80.
A 1.3 ?m InGaAsP/InP buried crescent laser diode has been fabricated on p-InP substrate. The laser diode has a low threshold current, as low as 10 mA. It operates at the output power of 5 mW under CW condition at temperatures higher nary aging test at 70°C with a constant light output of 5 mW, the lasers have been operating stably for more than 1000 h.  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