全文获取类型
收费全文 | 3573篇 |
免费 | 108篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 263篇 |
综合类 | 5篇 |
化学工业 | 909篇 |
金属工艺 | 85篇 |
机械仪表 | 86篇 |
建筑科学 | 85篇 |
矿业工程 | 1篇 |
能源动力 | 131篇 |
轻工业 | 363篇 |
水利工程 | 13篇 |
石油天然气 | 10篇 |
无线电 | 254篇 |
一般工业技术 | 624篇 |
冶金工业 | 433篇 |
原子能技术 | 125篇 |
自动化技术 | 304篇 |
出版年
2023年 | 25篇 |
2022年 | 51篇 |
2021年 | 81篇 |
2020年 | 30篇 |
2019年 | 45篇 |
2018年 | 85篇 |
2017年 | 63篇 |
2016年 | 113篇 |
2015年 | 64篇 |
2014年 | 101篇 |
2013年 | 213篇 |
2012年 | 169篇 |
2011年 | 210篇 |
2010年 | 157篇 |
2009年 | 198篇 |
2008年 | 193篇 |
2007年 | 155篇 |
2006年 | 126篇 |
2005年 | 127篇 |
2004年 | 100篇 |
2003年 | 102篇 |
2002年 | 107篇 |
2001年 | 70篇 |
2000年 | 55篇 |
1999年 | 69篇 |
1998年 | 194篇 |
1997年 | 131篇 |
1996年 | 84篇 |
1995年 | 70篇 |
1994年 | 78篇 |
1993年 | 73篇 |
1992年 | 31篇 |
1991年 | 26篇 |
1990年 | 20篇 |
1989年 | 32篇 |
1988年 | 18篇 |
1987年 | 18篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 21篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1979年 | 8篇 |
1978年 | 9篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1974年 | 9篇 |
1973年 | 5篇 |
排序方式: 共有3691条查询结果,搜索用时 15 毫秒
1.
New technologies such as power electronics have made it possible to change continuously the impedance of a power system not only to control power flow but also to enhance stability. A power system incorporating a variable impedance apparatus such as a variable series capacitor (VSrC) and high-speed phase shifter (HSPS) is called VIPS (Variable Impedance Power System) by the authors. This paper proposes a novel control method of VIPS apparatus such as VSrC and HSPS installed at an interconnecting point for stabilizing inter-area unstable and/or oscillatory modes. The proposed design method of the control system is a kind of hierarchical decentralized control method of a large-scale power system based on a Lyapunov function. Under the proposed control scheme, each subsystem can be stabilized independently by local controllers such as AVR, speed governor and PSS, and then the whole interconnected system can be stabilized by VIPS apparatus taking into account interactions between subsystems. The effectiveness and robustness of the VIPS apparatus control are shown by numerical examples with model systems including a large-scale power system. 相似文献
2.
Until now, attention has been focused solely in the drying of squid mantle from an experimental point of view, neglecting the transport phenomenon studies of water in squid muscle. This work studies the drying of squid mantle (Loligo brasiliensis), previously salted and smoked by liquid smoking (hickory extract), using a tubular dryer in closed cycle with a silicagel fixed bed in series. The mass transfer phenomenon during drying was studied, based on the Fick's second law, with the effective diffusivity supposed constant, which enabled an analytical solution to the problem. The drying curve calculated with the resulting equation was compared with experimental data. The model was applied to a hollow cylinder geometry (round squid mantle), with its internal surface isolated from the drying environment by a plastic film. The latter was given a tubular form and introduced inside the mantle cavity (impervious wall boundary condition). 相似文献
3.
This paper presents an efficient method which provides the optimal generation mix and the optimal generation construction process. The approximation method in which the dynamic programming technique and gradient method are combined is applied to determine the optimal generation mix with hydropower generation technologies. The successive approximations dynamic programming (SADP) technique, which is very suitable for high-dimensional multistage decision process problems, is used for obtaining the optimal generation construction process. The effectiveness and feasibility of the developed technique are demonstrated on a practical power system model which has five types of generation technologies including a hydropower generation technology. 相似文献
4.
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
5.
T Yokoyama H Gondo Y Tanaka K Takenaka K Tanimoto M Nakamura Y Niho 《Canadian Metallurgical Quarterly》1996,37(4):358-361
A 62-year-old Japanese man complained of fever, general fatigue, anorexia and watery diarrhea during remission of adult T-cell leukemia-lymphoma. Laboratory examinations showed severe hypoproteinemia (2.9 g/dl). However, neither intestinal lesions associated with ATL nor findings suggesting protein losing gastroenteropathy were observed. Cytomegalovirus (CMV) antigen detection assay using peripheral blood leukocytes revealed that he had an active CMV infection with hemophagocytic syndrome. Treatment with ganciclovir and methylprednisolone led to an improvement of hypoproteinemia. CMV disease and associated hemophagocytic syndrome should be considered as a cause of hypoproteinemia in an immunocompromised host. 相似文献
6.
Tohru Morii Hiroyuki Hamada Muriel Desaeger Akihiko Gotoh Atsushi Yokoyama Ignaas Verpoest Zen-ichiro Maekawa 《Composite Structures》1995,32(1-4):133-139
This study deals with the impact property and damage tolerance of matrix hybrid composite laminates with different laminate constitution. The matrix hybrid composite laminates consisted of the laminae with a conventional epoxy resin and the laminae with a flexible epoxy resin modified from the conventional resin to avoid the interlaminar delamination. The impact energy absorption ratio greatly depended on the matrix resin placed at the impact face. The energy absorption was almost constant if the conventional resin was placed at the impact surface layer, while it increased exponentially with the increasing fraction of the flexible resin if the flexible resin was placed at the impact face. The impact energy was absorbed by the damage development and propagation in the laminate with conventional resin laminae as the impacted face, while it was absorbed by both the recoverable deformation of the flexible resin and the damage propagation in the laminate with flexible resin laminae as the impacted face. 相似文献
7.
O Yokoyama Y Ishiura C Seto T Uchibayashi M Ohkawa 《Canadian Metallurgical Quarterly》1996,155(6):1882-1886
PURPOSE: We assessed the usefulness of and indications for endoscopic treatment of vesicoureteral reflux in myelodysplasia patients. MATERIALS AND METHODS: A total of 26 patients treated with intermittent catheterization was divided into 11 (16 ureters) with and 15 without vesicoureteral reflux. In 9 patients (13 ureters) endoscopic correction was performed with 3% atelo-collagen and without anesthesia at the outpatient clinic. In each ureter we obtained the sum of scores for 4 risk factors for upper urinary tract deterioration: bladder compliance less than 10 ml./cm. water, grade 2 to 3 bladder deformity, detrusor-sphincter dyssynergia and urethral closure pressure 50 cm. water or greater. RESULTS: No reflux was demonstrated immediately after the initial collagen injection but cystography 3 to 6 months later showed recurrent reflux in 5 ureters (38%). Repeat injection cured the reflux, with results persisting for an average of 17 months. Mean risk factor score for patients without vesicoureteral reflux was significantly lower than that for patients with reflux. In patients treated with intermittent catheterization and anticholinergic agents the mean score for ureters with an increased or unchanged reflux grade was significantly greater than for those with a decreased grade. CONCLUSIONS: Endoscopic treatment of reflux appears to be safe and useful in patients with myelodysplasia. The treatment is preferable in those with high risk factor scores due to the possibility of increased reflux grade in such patients. 相似文献
8.
The integral experiment on beryllium with D-T neutrons for verification of tritium breeding 总被引:1,自引:0,他引:1
Yury Verzilov Satoshi Sato Kentaro Ochiai Masayuki Wada Axel Klix Takeo Nishitani 《Fusion Engineering and Design》2007,82(1):1-9
A clean benchmark experiment on beryllium was performed with D-T neutrons at the FNS facility of the Japan Atomic Energy Agency. The main objective was to verify the integral data related to the tritium production on lithium isotopes. Tritium production rates, as well as activation reaction rates were measured inside the beryllium assembly that was shaped as a pseudo-cylindrical slab with an area-equivalent diameter of 628 mm and a thickness of 355 mm. Experimental results were analyzed with a three-dimensional Monte Carlo transport code MCNP-4C and FENDL/MC-2.0, JENDL-3.2/3.3 neutron transport libraries. Evaluation of reaction rates was based on the cross section data taken from the JENDL Dosimetry File and ENDF B-VI data libraries. Analysis shows that all calculation combinations (transport and activation cross section libraries) used for evaluation of reaction rates give data that is agreeable with measured values within 10%. 相似文献
9.
Criteria for evaluating flexibility of a generation mix are presented, and an efficient computational algorithm for determining a flexible generation mix considering uncertainties in the power system expansion planning is developed. The flexible generation mix problem is formulated as a multiobjective optimization problem and solved by the dynamic programming technique in which type of generation plant is selected as a stage and generation capacity is selected as a state. The proposed method can treat easily not only the uncertainties but also many constraints of generation planning such as integer solutions of generation capacities, reliability constraints, and so on. The effectiveness and feasibility of the proposed method are demonstrated on a typical power system model 相似文献
10.
M Mitani Y Yokoyama S Ichikawa H Sawada T Matsumoto K Fujimori M Kosugi 《Canadian Metallurgical Quarterly》1994,9(6):355-361
The chemiluminescence of the Cypridina luciferin analogue, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]pyrazin++ +-3-one (MCLA) was observed at 462 nm in the presence of horseradish peroxidase (HRP) and the total spectrum of light emitted was found to depend linearly on HRP concentration. Methods for the determination of HRP concentration using the chemiluminescence was investigated. HRP could be detected in the range from 100 pmol/L to 100 nmol/L under the optimum condition, H2O2 (10 mmol/L) and MCLA (10 mumol/L) at pH 5.8. 相似文献