全文获取类型
收费全文 | 593篇 |
免费 | 24篇 |
专业分类
电工技术 | 22篇 |
化学工业 | 135篇 |
金属工艺 | 22篇 |
机械仪表 | 20篇 |
建筑科学 | 10篇 |
能源动力 | 30篇 |
轻工业 | 64篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 45篇 |
一般工业技术 | 141篇 |
冶金工业 | 56篇 |
原子能技术 | 11篇 |
自动化技术 | 58篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 14篇 |
2017年 | 7篇 |
2016年 | 25篇 |
2015年 | 6篇 |
2014年 | 31篇 |
2013年 | 41篇 |
2012年 | 29篇 |
2011年 | 33篇 |
2010年 | 26篇 |
2009年 | 21篇 |
2008年 | 26篇 |
2007年 | 27篇 |
2006年 | 23篇 |
2005年 | 26篇 |
2004年 | 33篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有617条查询结果,搜索用时 31 毫秒
71.
The roles of ComFA and ComEC in DNA uptake by competent Bacillus subtilis were analyzed by transformation with DNA in protoplast lysates (LP transformation). Deletion mutants of comFA and comEC and putative Walker A mutants (K152N, K152Q, K152E) of comFA were constructed by fusion polymerase chain reaction. Transformants of comEC mutant with purified DNA and DNA in protoplast lysate were not obtained, which shows a lack of transformation ability and backwards recombination of the mutant. Transformants of the comFA mutant were obtained by LP transformation (1.8 × 10(4) transformants/μg DNA). Low relative efficiency of transformation (RET) of comFA compared to wild type (4.3 × 10(-4)) showed an important role for comFA in DNA uptake. Walker A mutants showed 1.8-19 × 10(-4) RET, suggesting a dependence on ATPase activity for transformation. Co-transformation between short linkages was only detected in comFA mutants. The results demonstrated that ComFA controlled the DNA uptake rate. The interpretation was further supported by analyzing the plasmid used in LP transformation of the comFA mutant. The RET of comFA compared to the wild type was 2.7 × 10(-2), 60-fold higher than that with chromosomal DNA (4.3 × 10(-4)). Following addition of DNA into comFA culture, transformants were obtained after 15 min, with the number of transformants increasing over time. The kinetics strongly suggested that in comFA mutants, formation of another DNA uptake complex without ComFA would be a lengthy process. 相似文献
72.
BACKGROUND: Research investigating the relationship between physical training and trace mineral concentrations has primarily focused on athletes. Few investigations, however, have specifically examined the alterations of trace mineral concentrations occurring in humans exposed to +Gz acceleration. Exercise alters mineral content; G-exposure is a form of exercise; therefore, G-exposure may elicit changes in mineral content. HYPOTHESIS: Exposure to +Gz acceleration may affect the concentrations of the trace minerals zinc, copper, and chromium in human serum and urine. METHODS: Blood samples were obtained from 7 men and 3 women, before and immediately after +Gz acceleration. Urine samples were obtained before, 30 min after, and 2 h after +Gz acceleration. RESULTS: The serum zinc concentration was significantly different after +Gz acceleration, decreasing from 90.6 +/- 21.0 micrograms.dl-1 to 80.8 +/- 14.4 micrograms.dl-1. The serum copper concentration was also significantly altered immediately after +Gz acceleration, decreasing from 111.7 +/- 27.5 micrograms.dl-1 to 98.5 +/- 35.2 micrograms.dl-1. The urinary zinc and copper concentrations, and the serum chromium concentration were not significantly affected by +Gz acceleration. CONCLUSIONS: The circulating levels of these minerals presumably change as they are transported to the tissues requiring greater amounts due to the increased physiological work associated with +Gz acceleration. 相似文献
73.
Hirokazu Kameoka Takuya Nishimoto Shigeki Sagayama 《IEEE transactions on audio, speech, and language processing》2007,15(3):982-994
This paper proposes a multipitch analyzer called the harmonic temporal structured clustering (HTC) method, that jointly estimates pitch, intensity, onset, duration, etc., of each underlying source in a multipitch audio signal. HTC decomposes the energy patterns diffused in time-frequency space, i.e., the power spectrum time series, into distinct clusters such that each has originated from a single source. The problem is equivalent to approximating the observed power spectrum time series by superimposed HTC source models, whose parameters are associated with the acoustic features that we wish to extract. The update equations of the HTC are explicitly derived by formulating the HTC source model with a Gaussian kernel representation. We verified through experiments the potential of the HTC method 相似文献
74.
Yoshihiro Ichikawa Shigeki Obote Kenichi Kagoshima 《Wireless Personal Communications》2005,35(4):353-364
A tapped delayed line adaptive array antenna (TDL-AAA) and a space-temporal simultaneous processing equalizer (ST-SPE) are
proposed as simple space-temporal equalizers based on minimum mean square error (MMSE) criterion. The ST-SPE has a compact
hardware with a small number of taps compared to that of the TDL-AAA. The ST-SPE can reduce the computational complexity of
the space-temporal joint equalization and it works effectively under the minimum phase condition such as appeared at line-of-sight
(LOS) propagation environments at a high antenna height base station. However the ST-SPE cannot work under a non-minimum phase
condition caused under N-LOS (non-line-of-sight). On the other hand, the TDL-AAA whose reference signal is synchronized at
the center tap (TDL-AAAC) can work even in the non-minimum phase condition. In this paper, we propose a dual-mode space-temporal simultaneous processing
equalizer (Dual-mode ST-SPE) which has a simple configuration and also works in non-minimum phase condition. The Dual-mode
ST-SPE can reduce the computational complexity compared to the TDL-AAAC.
Yoshihiro Ichikawa received the B.E. degree in department of communication engineering, in National Defense Academy in 1995, and M.E. and D.E.
degree from Ibaraki University in 2001 and 2004, respectively. He joined the Japan Air Self Defense Force in 1995. His research
interests are an adaptive algorithm, an antenna design, and an adaptive array antenna.
Shigeki Obote received his B.E., M.E. and D.E. degrees in electrical and electronic engineering from Tottori University, Tottori, Japan,
in 1996, 1998 and 2000, respectively. Since 2000, he has been with department of media and telecommunications engineering,
faculty of engineering, Ibaraki University, Ibaraki, Japan, where he is currently a associate professor. His research interests
are in adaptive array antenna and wireless communications systems.
Kenichi Kagoshima received the B.E., M.E. and D.E. degrees in electronics engineering from the Tokyo Institute of Technology, Tokyo, Japan,
in 1969, 1971, and 1974, respectively. He joined the Nippon Telegraph and Telephone Corporation (NTT) Laboratory in 1974 and
researched and developed many kinds of radio communication antennas. Since 1997, he has been a professor at Ibaraki University,
Ibaraki, Japan. Dr. Kagoshima was a Secretary and Treasure, Vice Chairman, and Chairman of the IEEE AP-S Tokyo Chapter in
1992, 1993, and 1994, respectively. He was a chair of antennas and propagation professional group of IEICE in 1999 and 2000.
In 1973, he received the Yonezawa Prize for Young Engineers and 1998, best paper award from IEICE, respectively. 相似文献
75.
Y Ohashi T Akamatsu T Hirata O Uchida M Kuro 《Canadian Metallurgical Quarterly》1996,45(10):1269-1271
The sickle-cell gene is most concentrated in West Central Africa, the northeast corner of Saudi Arabia and East Central India. Sickle cell trait is the heterozygous condition for Hb S gene. Thirty to fifty per cent of their hemoglobin is Hb S and the remainder is Hb A. The sickle-cell crisis is induced by hypoxia, hypercarbia, acidosis, low flow condition, and hypothermia, which leads to vasoocclusion. A 39-year-old black man from Burkina Faso located in West Africa with left ventricular rupture was admitted for operation using cardiopulmonary bypass (CPB). He had been diagnosed as sickle-cell trait. The Hb S concentration was 36.2 per cent before operation with hemoglobin electrophoresis. During CPB, the minimum blood temperature was 31 degrees C and an aortic cross-clamp was not done. Total CPB time was 1 hour 31 minutes. Use of vasodilator and hyperventilation was effective. No neurological sequelae were observed. 相似文献
76.
Inoue M. Yamada T. Kotani H. Yamauchi H. Fujiwara A. Matsushima J. Akamatsu H. Fukumoto M. Kubota M. Nakao I. Aoi N. Fuse G. Ogawa S. Odanaka S. Ueno A. Yamamoto H. 《Solid-State Circuits, IEEE Journal of》1988,23(5):1104-1112
A 16-Mb dynamic RAM has been designed and fabricated using 0.5-μm CMOS technology with double-level metallization. It uses a novel trench-type surrounding high-capacitance cell (SCC) that measures only 3.3-μm2 in cell size with a 63-fF storage capacitance. A novel relaxed sense-amplifier-pitch (RSAP) open-bit-line architecture used on the DRAM achieves a high-density memory cell array, while maintaining a large enough layout pitch for the sense amplifier. These concepts allow the small chip that measures 5.4×17.38 (93.85) mm2 to be mounted in a 300-mil dual-in-line package with 65-ns RAS access time and 35-ns column address access time 相似文献
77.
78.
Shigeki Toyama 《Desalination》1977,20(1-3)
The test module plant which is a quarter fragment of the conceptually designed, desalting plant with capacity of 100,000 m3/d has been operated as an activity of the national project in Japan. The type of the desalting plant is a high flow rate long tube multistage flash evaporator which is designed on the basis of the result achieved by the systematic research of the project. Where, condensing heat transfer tubes of length 33.6 m were successfully installed, and the reinforced concrete shell in the heat rejecting section is practiced without any trouble as a corrosion free vessel. The data acquisition system for the test module deals with 600 data which are classified into the total process, the concrete shell, the test sections and the pretreatment process. In the test section, temperature distribution of the brine flow is intended to measure at an accuracy of the order of 0.01°C. The paper describes these results on the basis of the recent information, and gives a scope for expecting effect on the progress of desalination technology. 相似文献
79.
80.
Shigeki Iyoki Masahito Nakanishi Hiroshi Yoshida Tohru Okuda Tadashi Uemura 《International Journal of Refrigeration》1993,16(4)
The thermodynamic properties (solubility, vapour pressure, density, viscosity, heat capacity and heat of mixing) of the H2O + CH3OH + LiBr + ZnCl2 (9:1 H2O:CH3OH and 1:1 LiBr:ZnCl2 by mass) system using H2O + CH3OH as the working media and LiBr + ZnCl2 as the absorbents were measured. The solubility data were obtained in the temperature range from 270.35 to 389.55 K. The measurements of vapour pressure, density, viscosity and heat capacity were carried out at various temperatures and absorbent concentrations. The differential heat of dilution and differential heat of solution at 298.15 K were measured for solutionw with absorbent concentrations from 0 to 75.2 wt%. The integral heat of mixing data at 298.15 K were obtained from both sets of experimental data. The integral heats of mixing for this quaternary system showed exothermic behaviour. The vapour pressure data were correlated with an Antoine-type equation. An empirical formula for the heat capacity was obtained from experimental data. The experimental data for the basic thermodynamic properties of this quaternary system were compared with those of the basic H2O + LiBr system. 相似文献