全文获取类型
收费全文 | 1964篇 |
免费 | 41篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 115篇 |
化学工业 | 393篇 |
金属工艺 | 66篇 |
机械仪表 | 41篇 |
建筑科学 | 26篇 |
矿业工程 | 1篇 |
能源动力 | 70篇 |
轻工业 | 148篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
无线电 | 171篇 |
一般工业技术 | 298篇 |
冶金工业 | 520篇 |
原子能技术 | 44篇 |
自动化技术 | 113篇 |
出版年
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 32篇 |
2020年 | 10篇 |
2019年 | 22篇 |
2018年 | 24篇 |
2017年 | 28篇 |
2016年 | 33篇 |
2015年 | 26篇 |
2014年 | 37篇 |
2013年 | 92篇 |
2012年 | 54篇 |
2011年 | 82篇 |
2010年 | 55篇 |
2009年 | 69篇 |
2008年 | 74篇 |
2007年 | 53篇 |
2006年 | 45篇 |
2005年 | 55篇 |
2004年 | 50篇 |
2003年 | 53篇 |
2002年 | 40篇 |
2001年 | 54篇 |
2000年 | 38篇 |
1999年 | 61篇 |
1998年 | 184篇 |
1997年 | 133篇 |
1996年 | 92篇 |
1995年 | 50篇 |
1994年 | 69篇 |
1993年 | 55篇 |
1992年 | 30篇 |
1991年 | 18篇 |
1990年 | 16篇 |
1989年 | 25篇 |
1988年 | 14篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 30篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1978年 | 7篇 |
1977年 | 21篇 |
1976年 | 20篇 |
1975年 | 5篇 |
1973年 | 6篇 |
1968年 | 4篇 |
排序方式: 共有2010条查询结果,搜索用时 16 毫秒
1.
2.
Eicosapentaenoic acid (EPA) production by an oleaginous fungus Mortierella alpina expressing heterologous the Δ17‐desaturase gene under ordinary temperature 下载免费PDF全文
3.
4.
Masaya Takahashi Akinori Nakata Takashi Haratani Yasutaka Ogawa Heihachiro Arito 《Ergonomics》2004,47(9):1003-1013
A worksite study was conducted to examine whether a 15-min nap during a post-lunch rest period would affect subsequent alertness, performance, and nocturnal sleep in eight factory workers under a 3-week protocol. Subjects were asked to take the nap at 12:30 h on a reclining chair during the nap week, and to remain awake during the no-nap week. The order of these 2 weeks was counterbalanced between the subjects. During the third, follow-up week, each subject determined whether or not she/he would nap. Alertness on the job and nocturnal sleep were assessed using a sleep diary. Wrist activity was also recorded during sleep at night. Choice reaction time task (RT) was performed at 10:00 and 15:00 h every day of the nap week and every other day of the no-nap and follow-up weeks. Perceived alertness was significantly higher in the afternoon after nap than after no nap at the end of the week. Similar effects were observed during the follow-up week where almost half of the subjects napped. No significant differences between the three weeks were found for RT performance or nocturnal sleep. Workers' attitudes toward the nap were favourable. Although further intervention research is required, our results suggest that post-lunch napping may have the potential to promote daytime alertness at work. 相似文献
5.
In recent years, computer technology has made remarkable progress and a computer has become an indispensable tool for both engineers and scientists. In this article, utilization of computers in welding research is briefly summarized. Their use in numerical analysis is particularly discussed and applied to physical phenomena in molten pool, hydrogen diffusion and residual stresses due to welding. A comparison is made between theoretical and experimental results. 相似文献
6.
I Tohnai Y Goto Y Hayashi M Ueda T Kobayashi M Matsui 《Canadian Metallurgical Quarterly》1996,12(1):37-47
This study investigated the impact of Difficulty Level and Type of Suggestion upon the durability of posthypnotic suggestion over an 8-week period. Seventy-eight highly susceptible subjects selected by both the Harvard Group Scale of Hypnotic Susceptibility: Form A (HGSHS:A) and Stanford Hypnotic Scale of Susceptibility: Form C (SHSS:C) were assigned to six groups (two levels of Difficulty x three Types of Suggestion). S's were tested for posthypnotic suggestion at 1, 3, 6, and 8 weeks. A 2 x 3 x 4 (Difficulty x Suggestion x Time) factorial ANOVA was conducted, with Time treated as a repeated-measure. The outcome variable at each time was either pass or fail for relevant suggestion. We found a significant Time effect, a significant Difficulty effect, and a significant Time x Difficulty interaction. Fewer subjects passed the difficult suggestions than passed the easy suggestions; fewer passed suggestions at a latter time; and the decay in pass rate was more pronounced for the easy suggestion condition, due largely to the higher initial pass rate. Type of Suggestion was not significant, nor were any of the other interactions. Clinical implications were discussed. 相似文献
7.
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
8.
The supercharged flap is one which is expected to attain better survival, by anastomosing the distal vessels of the flap to the recipient vessels. An experimental study is reported to determine whether the vessel to be anastomosed should be an artery, a vein, or both. The authors advise anastomosing an artery and a vein, but they believe that arterial inflow is more important than venous drainage. 相似文献
9.
Kenji Nomura Hiromichi OhtaKazushige Ueda Toshio Kamiya Masahiro HiranoHideo Hosono 《Thin solid films》2003,445(2):322-326
We have investigated the characteristics of transparent metal-insulator-semiconductor field-effect transistors (MISFETs) fabricated using InGaO3(ZnO)m (m=integer) single-crystalline thin films as n-channel layers and amorphous alumina as gate insulator films. The MISFETs exhibit good characteristics such as insensitivity to visible light illumination, off-current as low as ∼1 nA with a positive threshold voltage of ∼3 V and on/off current ratio of 105. The field-effect mobility increased from ∼1 to ∼10 cm2 (V s)−1 as the m-value increased. Room temperature Hall mobility also increased. However, unexpectedly these values were lower than the field-effect mobility. It is explained by existence of shallow localized state in the homologous compounds. 相似文献
10.
Preliminary experiments using two chemicals (CaO, a quicklime, and a cationic nitrogen-bearing precipitant, EC-004) to remove silica from geothermal brine were undertaken at the Mokai geothermal plant, New Zealand. The brine was mixed with the reagent (CaO or EC-004). The reaction was studied from the start of the experiment (NRT, 0 min, no retaining time) and after 15 min (15RT) at 90 °C. The concentration of silica in the brine was initially 954 mg/l, and decreased linearly with increasing reagent concentration. When CaO is added, the silica concentration at 15RT was 200 mg/l lower than at NRT and became almost zero on addition of 1.5 g/l. In contrast, when EC-004 is added, the total silica concentration nearly reaches the solubility of amorphous silica at 90 °C. In order to prevent silica scaling in Mokai brines cooled to 90 °C, the CaO and EC-004 added should be individually adjusted to 0.5 g/l and 80 mg/l, respectively. 相似文献