全文获取类型
收费全文 | 1681篇 |
免费 | 28篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 68篇 |
化学工业 | 439篇 |
金属工艺 | 37篇 |
机械仪表 | 31篇 |
建筑科学 | 13篇 |
能源动力 | 58篇 |
轻工业 | 76篇 |
水利工程 | 2篇 |
无线电 | 256篇 |
一般工业技术 | 266篇 |
冶金工业 | 312篇 |
原子能技术 | 51篇 |
自动化技术 | 102篇 |
出版年
2022年 | 20篇 |
2021年 | 22篇 |
2020年 | 12篇 |
2019年 | 18篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 16篇 |
2015年 | 23篇 |
2014年 | 29篇 |
2013年 | 58篇 |
2012年 | 39篇 |
2011年 | 74篇 |
2010年 | 53篇 |
2009年 | 70篇 |
2008年 | 64篇 |
2007年 | 50篇 |
2006年 | 57篇 |
2005年 | 58篇 |
2004年 | 53篇 |
2003年 | 67篇 |
2002年 | 40篇 |
2001年 | 40篇 |
2000年 | 32篇 |
1999年 | 48篇 |
1998年 | 135篇 |
1997年 | 75篇 |
1996年 | 65篇 |
1995年 | 56篇 |
1994年 | 44篇 |
1993年 | 41篇 |
1992年 | 33篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 27篇 |
1988年 | 18篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 24篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 21篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 14篇 |
1976年 | 11篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1966年 | 4篇 |
排序方式: 共有1711条查询结果,搜索用时 46 毫秒
81.
The speckle interferometer based on multi-camera technology using two cameras is applied to a dynamic deformation measurement of the package of an electronic device. To perform high precise measurement by this method, the optimum conditions for measurements are discussed concerning the size of speckle and the frequency of carrier signals. Under the optimum conditions, the deformation process of the package during the operation of an operational amplifier is measured. Then, the local maximum deformation can be estimated as 150 nm from experimental results. From the results, it can be also confirmed that electronic devices are deformed by the stress of a heat by an operation every second during the operating time. 相似文献
82.
Ito M. Nitta K. Ohno K. Saigusa M. Nishida M. Yoshioka S. Irita T. Koike T. Kamei T. Komuro T. Hattori T. Arai Y. Kodama Y. 《Solid-State Circuits, IEEE Journal of》2009,44(1):83-89
Supporting both WCDMA with HSDPA and GSM/GPRS/EDGE, the 9.3 times 9.3 mm2 SoC fabricated in triple-Vth 65 nm CMOS, has three CPU cores and 20 separate power domains. Unused power domains can be powered down to reduce the leakage power. Partial clock activation scheme especially focused on music playback scene dynamically stops a PLL and clock trees when not necessary and reduces power consumption from 33.6 mW to 19.6 mW. IP-MMU translates virtual address to physical address for 18 hardware-IPs and virtual address space can be allocated when necessary and can be freed after its operation, reducing external memory by 43 MB. Video performance of D1 (720 times 520) size with 30 frames per second for MPEG/AVC decoding and encoding can be achieved under mixed virtual and physical address usage. 相似文献
83.
A new GTO current source inverter in which two auxiliary GTO's are added to the basic inverter circuit, which consists of six GTO's and three capacitors, is presented. One of the auxiliary GTO's is connected between the positive line of the inverter and the neutral of three Y-connected capacitors; another is connected between the negative line and the neutral. In the proposed inverter, the charges of three capacitors are controlled at the same time by means of pulsewidth modulation (PWM) to main GTO's and auxiliary GTO's. This inverter can supply both the sinusoidal current and voltage to the motor. The PWM control technique, the operating principle, and the experimental results for 2.2-kW induction motor drives are described. The output current waveform of this inverter is closely sinusoidal, as opposed to trapezoidal in the basic inverter circuit. The steady-state characteristics of the GTO-CSI induction motor drive system are analyzed by the state-variable methods, and a close agreement between the analyzed and the experimental results is obtained. Smooth and noiseless drive of induction motor over a wide range of speed is observed. 相似文献
84.
Saitoh M Asaka K Arai M Kawabata A Kanoh S Kanoh T 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2002,43(4):243-249
In order to evaluate the relationship between nasal carriers of S. aureus and their history of allergic diseases, the total serum IgE titer, the hemogramme pattern, and the titers of specific IgE antibody to Staphylococcal enterotoxins A and B (SEA and SEB) and of specific IgG antibody to SEB were investigated in 98 trade school students. Fifteen (15.3%) of the 98 students were sensitized to SEA and/or SEB (40.0% to SEA and 93.3% to SEB). In this group, 11 subjects were S. aureus carriers (73.0%) and 12 had a history of allergic diseases (80.0%). Low levels of specific IgG antibody to SEB were identified from both S. aureus carriers and non-carriers. The S. aureus carriers had significantly higher levels of total IgE titer than the non-carriers and the individuals with a history of allergic diseases had significantly higher total IgE titer levels than those having no history of allergic diseases (p < 0.01). In the hemogramme patterns of S. aureus carriers, a significant positive correlation was observed between the total IgE antibodies and the eosinophil rate (p < 0.05), and a negative correlation (p < 0.001) was recognized between the neutrophil and the lymphocyte rates. 相似文献
85.
We propose a new function of the two-dimensional lens array that is composed of many gradient-index lenses. The array forms three-dimensional (3D) images. The characteristics of the 3D images depend on the length of the gradient-index lens. Especially, if the length of the lens is an odd-integer multiple of the half period of the optical path, 3D images are pseudoscopic with a reversed depth. The two lens arrays are positioned at a suitable distance, so that orthoscopic 3D images with the correct depth are formed in front of the lens array. 相似文献
86.
Daisuke Nagamatsu Masanori Maeda Keisuke Hashimoto Kenji Okumoto Hiroshi Kageyama Yasuhiko Shirota 《Journal of the Society for Information Display》2005,13(5):399-404
Abstract— A novel emitting vinyl polymer, poly[4‐(7‐{4‐[N,N‐bis(9,9‐dimethylfluoren‐2‐yl)amino]phenyl}‐2,1,3‐benzothiadiazol‐4‐yl)phenylethylene] (PVFABT), was designed and synthesized. The new vinyl polymer was found to form smooth amorphous films with a high glass‐transition temperature of 199°C. The polymer possesses bipolar character with both electron‐donating and accepting properties. It undergoes reversible anodic oxidation and cathodic reduction to give stable cation and anion radicals. It exhibits intense orange fluorescence in solution and as film. A multilayer organic electroluminescent device using PVFABT as an emitting material emitted orange light, exhibiting high performance. 相似文献
87.
Arai M. Kondo T. Matsutani A. Miyamoto T. Koyama F. 《IEEE journal of selected topics in quantum electronics》2002,8(4):811-816
We carried out the growth of highly strained GaInAs-GaAs quantum wells (QWs) on a patterned substrate for extending emission wavelength on a GaAs substrate. We examined the shift of photoluminescence wavelength of the QWs and showed a large wavelength shift due to the spatial modulation in well thickness and indium composition. We demonstrated a single-mode multiple-wavelength vertical-cavity surface-emitting laser (VCSEL) array on a patterned GaAs substrate covering a new wavelength window of 1.1-1.2 /spl mu/m. By optimizing pattern shape, we achieved multiple-wavelength operation with widely and precisely controlled lasing wavelengths. The maximum lasing span is as large as 77 nm. We carried out a data transmission experiment through 5-km of single-mode fiber with a 2.5 Gb/s/channel. The total throughput reaches 10 Gb/s. The VCSEL-based wavelength-division-multiplexing (WDM) source would be a good candidate for WDM-LAN beyond 10 Gb/s. 相似文献
88.
Tetragonal to monoclinic phase transformation of yttria-stabilized zirconia, namely plasma-sprayed coatings and sintered bodies containing 4–8 mass % Y2O3 during hydrothermal aging was investigated with respect to Y2O3 distribution using 1 m area from electron probe microanalysis (EPMA) and 20 nm area from transmission electron microscopy (TEM) analysis. Phase transformation at 473 K was prevented only in plasma-sprayed coatings having more than 6.7 mass % Y2O3 in 20 nm microscopic area. Furthermore, it was confirmed influence of Y2O3 distribution on the rate constants of this phase transformation was observed at 368 K. 相似文献
89.
The linewidth enhancement factor, α, in the Ga1-xInxAs/GaInAsP/InP strained-quantum-well system was calculated and analyzed using density-matrix theory taking into account the effects of band-mixing on both the valence subbands and the transition dipole moments. As a result of numerical calculation, it was found that a reduced linewidth enhancement factor of 1.1 at the gain peak wavelength can be obtained in the tensile strained-quantum-well structure for TM-mode operation. This is due to the higher differential gain and a negligible free carrier plasma effect in the TM-mode compared to that of the TE-mode operating in the compressively strained-quantum-well structure. This calculation agrees with previously reported experimental results 相似文献
90.
In manufacturing facilities, shipping and receiving traditionally have been concentrated in one or two areas of the building. The widespread introduction of just-in-time shipping policies in US manufacturing companies during the past 15 years, as well as the common use of decentralized receiving in the Japanese automobile industry, has motivated the consideration (and occasionally the adoption) of dock configurations to support decentralized receiving (also known as perimeter receiving). By providing multiple access points along the perimeter of the building, decentralized receiving generally reduces the time and cost associated with moving purchased parts to the locations within the facility where they are used, but also results in increased cost of construction, maintenance, and operation for docks and associated truck access/egress, as well as additional interior floorspace requirements. We develop an optimization-based procedure to determine which of several possible dock areas to construct, how many doors or gates each should have, how many unloading and internal material handling staff should be assigned to each group, and which inbound materials each group should handle. We consider the amortized cost of constructing and equipping the docks, the amortized cost of material handling equipment to support the unloaders and material handlers, the cost of operating the material handling equipment, and labor costs for both unloading and internal material handling. 相似文献