全文获取类型
收费全文 | 2007篇 |
免费 | 41篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 153篇 |
综合类 | 3篇 |
化学工业 | 426篇 |
金属工艺 | 50篇 |
机械仪表 | 35篇 |
建筑科学 | 19篇 |
矿业工程 | 2篇 |
能源动力 | 88篇 |
轻工业 | 152篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 161篇 |
一般工业技术 | 340篇 |
冶金工业 | 482篇 |
原子能技术 | 40篇 |
自动化技术 | 90篇 |
出版年
2023年 | 9篇 |
2022年 | 5篇 |
2021年 | 32篇 |
2020年 | 14篇 |
2019年 | 17篇 |
2018年 | 26篇 |
2017年 | 10篇 |
2016年 | 23篇 |
2015年 | 30篇 |
2014年 | 36篇 |
2013年 | 115篇 |
2012年 | 65篇 |
2011年 | 100篇 |
2010年 | 62篇 |
2009年 | 59篇 |
2008年 | 79篇 |
2007年 | 76篇 |
2006年 | 68篇 |
2005年 | 57篇 |
2004年 | 48篇 |
2003年 | 66篇 |
2002年 | 51篇 |
2001年 | 37篇 |
2000年 | 34篇 |
1999年 | 46篇 |
1998年 | 208篇 |
1997年 | 131篇 |
1996年 | 75篇 |
1995年 | 44篇 |
1994年 | 53篇 |
1993年 | 62篇 |
1992年 | 23篇 |
1991年 | 14篇 |
1990年 | 34篇 |
1989年 | 20篇 |
1988年 | 14篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 15篇 |
1977年 | 10篇 |
1976年 | 29篇 |
1974年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有2049条查询结果,搜索用时 265 毫秒
1.
Effects of Winding Attachment Positions on Output Characteristics of Flux‐Modulating Synchronous Machines 下载免费PDF全文
Hirofumi Aoki Tadashi Fukami Kazuo Shima Toshihiro Tsuda Mitsuhiro Kawamura 《Electrical Engineering in Japan》2015,191(3):40-49
The flux‐modulating synchronous machine (FMSM) is a new type of multipole SM with nonoverlapping concentrated armature and field windings on the stator. This paper compares the output characteristics of two FMSMs through finite element analysis (FEA) and experiments. In both of the FMSMs, the attachment positions of the armature and field windings are swapped. To determine the reason for the discrepancies in their output characteristics, unsaturated inductances were calculated using a d‐‐q equivalent circuit. In addition, the calculated results of the inductances were confirmed through a visualization of the leakage fluxes using FEA. The results of the study show that the synchronous inductance can be reduced by attaching the armature winding to the air‐gap side of the stator teeth and that the reduction leads to an increase in output power. 相似文献
2.
Heterogeneous curable compositions of divalent metal salts of mono(hydroxyethyl) phthalate–anhydride–bisphenol A diglycidyl ether (BADG) systems were prepared by merely mixing these components at room temperature. Stability at room temperature and cure properties at high temperature of the compositions were investigated for evaluating their applicability as one part adhesive. It was found that the systems containing Mg were generally more stable than those containing Ca. Similarly, at 150°C the Ca-containing systems showed generally shorter gelation time than the Mg-containing ones, due to the fact that the Ca salt dissolves more rapidly and enters into the addition reaction with the anhydride, leading to the faster appearance of the catalytic activities of the Ca carboxylate group. Among the various combinations of components, the metal salt–succinic anhydride (SA)–BADG systems were stable at room temperature for more than 6 months and rapidly cured at high temperature, showing excellent adhesive properties. This result indicates that the SA-containing systems should be of interest in applications to one part adhesives. 相似文献
3.
Kazuhiko Miyazaki Hirofumi Kasada Masayuki Ohtsuka 《Journal of Infrared, Millimeter and Terahertz Waves》1994,15(10):1669-1674
We succeeded in observing the continuously tunable, pulsed InSb SFR (Spin-Flip Raman) laser emission in the infrared region of 11~16µm (11.4~16.3µm) from only one InSb device, merely by adjusting the pumping wavelength (11 lines from the infrared NH3 laser) and the applied magnetic field (0~80 kGauss). 相似文献
4.
During a 22-year period, 13 patients with hematologic diseases developed bacteremia caused by the Bacteroides fragilis group, with a frequency which remained almost unchanged. Nine patients (69%) had polymicrobial infections. Acute leukemia was the most common underlying disease. The lower intestinal tract (necrotizing enterocolitis and anorectal abscesses) was the most common source of infection. Prior antibiotic therapy was the most frequent host condition before bacteremia, followed by cancer chemotherapy, neutropenia, thrombocytopenia and hypoproteinemia. Septic shock occurred only in seven patients with polymicrobial infections. Six patients, including five with shock, died within a week of onset, while the other seven survived for at least three weeks. Despite its clinical similarity to aerobic gram-negative infection, bacteremia due to the B. fragilis group may well, therefore, be suspected particularly when neutropenic patients who present with lower intestinal symptomatology develop a persistent fever unresponsive to the initial empiric antibiotic therapy. 相似文献
5.
Saito M. Yoshitomi T. Hara H. Ono M. Akasaka Y. Nii H. Matsuda S. Momose H.S. Katsumata Y. Ushiku Y. Iwai H. 《Electron Devices, IEEE Transactions on》1993,40(12):2264-2272
A p-MOSFET structure with solid-phase diffused drain (SPDD) is proposed for future 0.1-μm and sub-0.1-μm devices. Highly doped ultrashallow p+ source and drain junctions have been obtained by solid-phase diffusion from a highly doped borosilicate glass (BSG) sidewall. The resulting shallow, high-concentration drain profile significantly improves short channel effects without increasing parasitic resistance. At the same time, an in situ highly-boron-doped LPCVD polysilicon gate is introduced to prevent the transconductance degradation which arises in ultrasmall p-MOSFETs with lower process temperature as a result of depletion formation in the p+-polysilicon gate. Excellent electrical characteristics and good hot-carrier reliability are achieved 相似文献
6.
This paper describes a brushless dc motor system without position or speed sensor. The brushless motor consists of a permanent magnet synchronous motor and a voltage-source inverter capable of controlling the amplitude and frequency of voltage. The rectangular-shaped stator current with a conducting interval of 120° (electrical) is controlled to be in phase with the trapezoidal back electromotive force. This results in producing maximum torque. Variable speed is achieved by adjusting the average motor voltage similarly to chopper control of dc motors. In this paper, two sensorless position detecting methods, i.e., an “indirect method” suited for the lower-speed range and a “direct method” suited for the higher-speed range are proposed. The combination of the two makes it possible to detect the rotor position over a wide-speed range. Furthermore, a speed-sen-sorless PLL control is proposed in applying the principle of the direct method. Experimental results obtained from a prototype brushless dc motor are shown to confirm the validity of the sensorless drive. The starting procedure of the motor also is discussed because it is impossible to detect the rotor position at a standstill. 相似文献
7.
This paper proposes a new belt drive control method for reducing a belt velocity-fluctuation that is caused by a belt thickness-variation in the circumferential direction. A belt driving system performs feedback control with a rotary encoder-output mounted on a driven roller. This proposed method correct the reference value of the feedback control for the purpose of the belt velocity regulation. The correction includes two steps. The first step acquires the encoder-output of the driven roller and calculates the rotational angular velocity-fluctuation with one cycle of the belt rotation. The second step converts from the velocity-fluctuation to the correction value of the feedback reference. The correction value cancels a detection error of the driven roller caused by the belt thickness-variation. After these steps, the belt driving system controls the belt velocity as compensating the belt velocity-fluctuation. Experimental result showed the significant fluctuation reduction on a typical tandem-engine printer. 相似文献
8.
Hara H. Sakurai T. Nagamatsu T. Seta K. Momose H. Niitsu Y. Miyakawa H. Matsuda K. Watanabe Y. Sano F. Chiba A. 《Solid-State Circuits, IEEE Journal of》1992,27(11):1579-1584
BiCMOS standard cell macros, including a 0.5-W 3-ns register file, a 0.6-W 5-ns 32-kbyte cache, a 0.2-W 3-ns table look-aside buffer (TLB), and a 0.1-W 3-ns adder, are designed with a 0.5-μm BiCMOS technology. A supply voltage of 3.3 V is used to achieve low power consumption. Several BiCMOS/CMOS circuits, such as a self-aligned threshold inverter (SATI) sense amplifier and an ECL HIT logic are used to realize high-speed operation at the low supply voltage. The performance of the BiCMOS macros is verified using a fabricated test chip 相似文献
9.
This paper deals with an advanced static Var compensator (ASVC) using quad-series voltage-source PAM inverters. The ASVC consists of four three-phase voltage-source inverters with a common dc capacitor and four three-phase transformers, each primary winding of which is connected in series with each other. Each inverter outputs a square-wave voltage, while the synthesized output voltage of the ASVC has a 24-step wave shape. This results not only in a great reduction of harmonic currents and dc voltage ripples but also in fewer switching and snubbing losses. In this paper, transient analysis is performed with the focus on the response of reactive power and the resonance between the dc capacitor and ac reactors. Experimental results obtained from a small-rated laboratory model of 10 kVA are also shown to verify analytical results based on the p-q transformation. The analytical results help in the design of system parameters such as the capacity of the dc capacitor and feedback gains. 相似文献
10.
Changes in the brain lactate concentration in cerebral extracellular fluid (ECF) during intravenous infusion of glucose and local administration of glucose were investigated in adult, conscious, unrestrained rats, with a microdialysis probe in the posterior hippocampus. The rats were infused intravenously with either 25% sucrose solution or 25% glucose solution at a rate of 16.6 microliters.min-1.100 g-1 for three hours. The blood glucose concentration reached 17.0 +/- 2.6 mM at the end of the glucose infusion, and brain ECF glucose showed a parallel change with the blood glucose concentration and increased to 2.37 +/- 0.30 mM. However, blood and brain ECF glucose concentrations did not change in animals infused with the sucrose solution. On the other hand, the blood lactate concentration in the glucose-infused group also increased from 0.93 +/- 0.18 mM to 2.85 +/- 0.39 mM at the end of the glucose infusion, which was significantly higher than that measured in the sucrose-infused group. The blood lactate level in the glucose-infused group returned to the basal level by the end of the experiment. Brain ECF lactate concentrations increased from 1.21 +/- 0.06 mM to 1.69 +/- 0.11 mM in glucose-infused animals, but did not change in the sucrose-infused animals. The brain ECF lactate concentration showed a positive correlation with the brain ECF glucose concentration in glucose-infused animals. Another group of rats was administered glucose locally for 90 min after substitution of artificial cerebrospinal fluid.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献