全文获取类型
收费全文 | 1649篇 |
免费 | 34篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 115篇 |
综合类 | 2篇 |
化学工业 | 458篇 |
金属工艺 | 51篇 |
机械仪表 | 35篇 |
建筑科学 | 26篇 |
能源动力 | 102篇 |
轻工业 | 147篇 |
水利工程 | 12篇 |
石油天然气 | 1篇 |
无线电 | 139篇 |
一般工业技术 | 303篇 |
冶金工业 | 96篇 |
原子能技术 | 47篇 |
自动化技术 | 152篇 |
出版年
2023年 | 6篇 |
2022年 | 15篇 |
2021年 | 23篇 |
2020年 | 17篇 |
2019年 | 24篇 |
2018年 | 17篇 |
2017年 | 18篇 |
2016年 | 30篇 |
2015年 | 20篇 |
2014年 | 52篇 |
2013年 | 106篇 |
2012年 | 90篇 |
2011年 | 90篇 |
2010年 | 81篇 |
2009年 | 100篇 |
2008年 | 85篇 |
2007年 | 73篇 |
2006年 | 69篇 |
2005年 | 62篇 |
2004年 | 45篇 |
2003年 | 55篇 |
2002年 | 49篇 |
2001年 | 26篇 |
2000年 | 39篇 |
1999年 | 48篇 |
1998年 | 56篇 |
1997年 | 23篇 |
1996年 | 43篇 |
1995年 | 21篇 |
1994年 | 26篇 |
1993年 | 26篇 |
1992年 | 28篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有1686条查询结果,搜索用时 843 毫秒
1.
T Akahoshi T Nagaoka R Namai N Sekiyama H Kondo 《Canadian Metallurgical Quarterly》1997,16(6):231-235
The effects of monosodium urate (MSU) crystals on apoptosis of cultured peripheral blood neutrophils were investigated. MSU crystals at low concentrations decreased the rate of spontaneous apoptosis of neutrophils in a dose- and time-dependent manner. The culture supernatant of MSU crystal stimulated neutrophils also promoted a delay in neutrophil apoptosis. MSU crystals at higher concentrations rapidly caused cell lysis. These findings indicated that MSU crystals are capable of amplifying the inflammatory responses of gouty arthritis by decreasing the rates of neutrophil apoptosis at lower concentrations and inducing cell lysis at higher concentrations. 相似文献
2.
Kawahito S. Ueda S. Ishida M. Nakamura T. Usui S. Nagaoka S. 《IEEE transactions on bio-medical engineering》1994,41(4):400-406
A CMOS integrated circuit for a noninvasive biological-signal telemetry system specified for use in medical and physiological studies of the influence of weightlessness in space is presented. The system can monitor multichannel (4 channels maximum) biological signals from multiple subjects (4 subjects maximum) in real time by using time multiplexing. A key technique so-called synchronized multiple-subject telemetry, to achieve multiple-subject telemetry has been proposed. This technique utilizes bidirectional optical transmissions with direct and scattered infrared lights between an observer and each of the subjects. An experimental CMOS IC to give a small light-weight low-power, and smart telemetry instrument for use on animals has been developed. This IC is for evaluating circuit blocks of the implantable monolithic telemetry instrument. The major circuit blocks include CMOS digital circuits for synchronization, subject selection and time multiplexing, analog circuits for pulse interval modulation, and other blocks such as a CMOS optical pulse receiver and an LED driver. A preliminary experimental multichannel telemetry from two subjects has been performed with the implemented IC chips, and the principal operation of the multiple-subject optical biotelemetry has been demonstrated 相似文献
3.
Shijie Zhu Yutaka Kagawa Jian-Wu Cao Mineo Mizuno 《Metallurgical and Materials Transactions A》2004,35(9):2853-2859
Time-dependent deformation in an enhanced SiC/SiC composite has been studied under constant load at high temperatures of 1200
°C, 1300 °C, and 1400 °C. Creep damage evolution was evaluated by a Young’s-modulus change of partial unloading and microscopic
observation. The addition of the glassy phase in the matrix is very effective for protecting the composite from oxidation.
The transient creep is dominant in creep life at all the temperatures. An empirical equation is proposed to describe creep
behavior of the composite. It is found that creep activation energy increases with creep time at stresses lower than matrix
cracking stress, but the activation energy remains constant at stresses higher than the matrix cracking stress. The creep
strain rate of the composite is considered to be controlled by creep of fibers based on examining the time, strain, stress,
and temperature dependencies of creep strain rates. 相似文献
4.
Hirokazu Ikeda Chikara Fukunaga Yutaka Saitoh Masahiro Inoue Junko Yamanaka 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,380(3):618-622
The radiation tolerance for prototype front-end chips designed for a silicon micro-strip detector was examined with a 60Co irradiation source to establish an allowable range of the radiation dose. The irradiated front-end chips were SMA2SH-64A, a 64-channel preamplifier array; SMA2SH-1, a single-channel preamplifier circuit with a comparator; and Control-C, a digital-control chip for the preamplifiers. 相似文献
5.
Yutaka Asako Hisayoshi KamikogaHisashi Nishimura Yoshiyuki Yamaguchi 《International Journal of Heat and Mass Transfer》2002,45(11):2243-2253
Compression is one solution to improve the strength of softwoods. The effective thermal conductivities of compressed Japanese cedars (cryptomeria japonica), which were compressed in the radial direction of the wood, were measured. Both the effective thermal conductivities in the tangential and fiber directions increase proportionally to the density increment due to the compression. However, the thermal conductivity in the radial direction (compression direction) increases slightly with the density increment. Numerical computations were conducted to explain the characteristics of thermal conductivity in the radial direction by using a microscopic heat conduction model for the compressed wood. The numerical results were compared with the measured values. And the physical mechanism of the heat conduction in the compressed woods is discussed. 相似文献
6.
A single loop electrochemical potentiokinetic reactivation test method has been developed for alloy 600 that produces good passivation on all the surfaces, good etching during the reactivation scan and no appreciable pitting. It is able to quantify and discriminate between samples with a wide range of degree of sensitization. The Pa value correlates well with the minimum level of chromium in the depletion regions at the grain boundaries. It has been shown that the width of the attacked regions is much larger than the width of chromium depletion regions and it does not show any direct correlation with either depth or width or with a volume parameter of chromium depletion regions. It has been shown that the chromium carbides are not attacked during the test and that the intragranular regions attacked during the test are the sites of chromium carbides in the grain matrix. A modified Pa parameter is shown to be sensitive down to 7.5 wt% chromium in the depletion regions and indicates that the intragranular carbides have shallower depletion profiles than those at grain boundaries. Comparison of the results of the single loop and the double loop tests showed a good correlation. 相似文献
7.
The effect of Zr on reduction of hardness and microstructure in an FS weld of equal channel angular-pressed Al alloy was investigated. Zr addition to Al suppressed dynamic recovery in the thermomechanically affected zone and enabled retention of the high hardness of the ECA-pressed material throughout the weld. 相似文献
8.
9.
In recent years the requirement for the reduction of energy consumption has been increasing to solve the problems of global warming and the shortage of petroleum resources. For example, in the power generation field, as thermal power generation occupied 60% of the power generation demand, considerable improvement of the thermal efficiency is required. This paper describes the pressure drop characteristics of finned tube banks used for heat exchangers in thermal power generation that were clarified by testing serrated finned tube banks with different fin heights for improved heat transfer and conventional spiral finned tube banks with different fin heights, and an equation to predict pressure drop which is necessary for the heat exchanger design is proposed. © 2006 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(3): 179–193, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20112 相似文献
10.
Nishihori K. Kitaura Y. Hirose M. Mihara M. Nagaoka M. Uchitomi N. 《Electron Devices, IEEE Transactions on》1998,45(7):1385-1392
This paper describes a newly developed GaAs metal semiconductor field-effect transistor (MESFET)-termed p-pocket MESFET-for use as a linear power amplifier in personal handy-phone systems. Conventional buried p-layer technology, the primary technology for microwave GaAs power MESFET's, has a drawback of low power efficiency for linear power applications. The low power efficiency of the buried p-layer MESFET is ascribed to the I-V kink which is caused by holes collected in the buried p-layer under the channel. In order to overcome this problem, we have developed the self-aligned gate p-pocket MESFET which incorporates p-layers not under the channel but under the source and drain regions. This new MESFET exhibited high transconductance and uniform threshold voltage. The problematic I-V kink was successfully removed and an improved power efficiency of 48% was achieved under bias conditions, which resulted in adjacent channel leakage power at 600-kHz offset as low as -59 dBc for 1.9-GHz π/4-shift QPSK modulated input 相似文献