全文获取类型
收费全文 | 774篇 |
免费 | 49篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 90篇 |
综合类 | 9篇 |
化学工业 | 203篇 |
金属工艺 | 37篇 |
机械仪表 | 23篇 |
建筑科学 | 18篇 |
矿业工程 | 6篇 |
能源动力 | 33篇 |
轻工业 | 51篇 |
水利工程 | 2篇 |
石油天然气 | 20篇 |
武器工业 | 6篇 |
无线电 | 97篇 |
一般工业技术 | 138篇 |
冶金工业 | 31篇 |
原子能技术 | 11篇 |
自动化技术 | 53篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 21篇 |
2021年 | 26篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 20篇 |
2015年 | 25篇 |
2014年 | 33篇 |
2013年 | 74篇 |
2012年 | 34篇 |
2011年 | 54篇 |
2010年 | 40篇 |
2009年 | 48篇 |
2008年 | 37篇 |
2007年 | 24篇 |
2006年 | 36篇 |
2005年 | 16篇 |
2004年 | 20篇 |
2003年 | 25篇 |
2002年 | 29篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 19篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有828条查询结果,搜索用时 19 毫秒
51.
Soichi Kugimiya Takeshi Shimoda Jun Tabata Junji Takabayashi 《Journal of chemical ecology》2010,36(6):620-628
Females of the solitary endoparasitoid Cotesia vestalis respond to a blend of volatile organic compounds (VOCs) released from plants infested with larvae of their host, the diamondback
moth (Plutella xylostella), which is an important pest insect of cruciferous plants. We investigated the flight response of female parasitoids to the
cruciferous plant Brassica rapa, using two-choice tests under laboratory conditions. The parasitoids were more attracted to plants that had been infested
for at least 6 hr by the host larvae compared to intact plants, but they did not distinguish between plants infested for only
3 hr and intact plants. Although parasitoids preferred plants 1 and 2 days after herbivory (formerly infested plants) over
intact plants they also preferred plants that had been infested for 24 hr over formerly infested plants. This suggests that
parasitoids can distinguish between the VOC profiles of currently and formerly infested plants. We screened for differences
in VOC emissions among the treatments and found that levels of benzyl cyanide and dimethyl trisulfide significantly decreased
after removal of the host larvae, whereas terpenoids and their related compounds continued to be released at high levels.
Benzyl cyanide and dimethyl trisulfide attracted parasitoids in a dose-dependent manner, whereas the other compounds were
not attractive. These results suggest that nitrile and sulfide compounds temporarily released from plants under attack by
host larvae are potentially more effective attractants for this parasitoid than other VOCs that are continuously released
by host-damaged plants. 相似文献
52.
Novel transdermal drug delivery system with polyhydroxyalkanoate and starburst polyamidoamine dendrimer 总被引:1,自引:0,他引:1
Wang Z Itoh Y Hosaka Y Kobayashi I Nakano Y Maeda I Umeda F Yamakawa J Kawase M Yag K 《Journal of Bioscience and Bioengineering》2003,95(5):541-543
In search of an efficient transdermal drug delivery system (TDDS), a polyhydroxyalkanoate (PHA)-based system with a polyamidoamine dendrimer was examined. Tamsulosin was used as the model drug. The dendrimer was found to act as the weak enhancer. By adding the dendrimer, the dendrimer-containing PHA matrix achieved the clinically required amount of tamsulosin permeating through the skin model. This is also the first report of the application of PHA and dendrimer to the TDDS. 相似文献
53.
For the diffusion-controlled adsorption, the expression of dynamic surface adsorption Γ(t) was ob-tained by solving the diffusion equation. Two cases, i.e. the short and long time limits, were mainly d... 相似文献
54.
Daisuke Hiramatsu Yoichi Uemura Shinji Uemoto Junji Okumoto Takehiko Imai Mikio Kakiuchi Ken Nagakura Masafumi Fujita Toru Otaka 《Electrical Engineering in Japan》2011,177(3):17-27
Two‐pole large generators are extensively used in power utilities. Growing demand for electric power in recent years has led to substantial increases in the capacity of generators. In line with this trend, our company has manufactured two‐pole turbine generators in the 900,000‐kVA to 1,200,000‐kVA classes. As the capacity of generators becomes larger, equivalent circuits are increasingly expected to improve their precision in estimating operation characteristics. The Park model has been widely used as an equivalent circuit model. The Park model with quadrature axis transient reactance $x_{q}^{\prime}$ is claimed to be useful for accurately estimating the load rejection characteristics of turbine generators. However, it is difficult to measure $x_{q}^{\prime}$, few studies based on measured data have appeared. As one of the few examples, we have conducted a measured data on a 500,000‐kVA‐class generator. Recently, the authors obtained test data on $x_{q}^{\prime}$ of a 900,000‐kVA‐class generator. In this study, based on these data, we studied the effect of $x_{q}^{\prime}$ using the finite element method and a transient analysis program (EMTP‐ATP). © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(3): 17–27, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21099 相似文献
55.
Nobuhisa Ochi Shigetaka Okano Masahito Mochizuki Junji Shimamura Nobuyuki Ishikawa 《Welding International》2013,27(3):174-183
In recent years, in order to reduce the costs of transportation and construction of pipelines, which are often constructed using multiple-electrode submerged arc welding (SAW), higher joint performance is required. Therefore, there has arisen the need to understand theoretically and control appropriately metallurgical and mechanical characteristics in heat-affected zone (HAZ), which has a significant influence on the strength and toughness of welded joints. Commonly, metallurgical phenomena in HAZ are evaluated based on the highest temperature and the cooling rate. Therefore, in order to control metallurgical and mechanical characteristics in HAZ by means of the welding conditions, evaluating the temperature distribution and the temperature history near the melted zone is essential. However, a detailed investigation of the temperature distribution for multiple-electrode SAW has not yet been carried out enough. In this study, in order to investigate the temperature distribution and histories during multiple-electrode SAW, the experimental results are compared with the theoretical results. In the theoretical analysis, the temperature rise equation in multiple heat sources welding is developed using the method of summation. Furthermore, on temperature distribution during welding, the effects of multiple heat sources, such as the number of heat sources and the distance between each electrodes, are considered quantitatively through the thermal conduction theoretical analysis. As the result, the distance between lead heat source and final heat source primally influences the area with the difference between a single heat source welding and multiple heat sources welding. Based on the results, it is expected to control temperature distribution near melted zone by more appropriate heat input characteristics, which is depended on heat source arrangement. 相似文献
56.
Ruthenium-oxide nanosheet (RuO2ns) crystallites with thickness less than 1 nm were prepared via chemical exfoliation of a layered potassium ruthenate and deposited onto carbon supported platinum (Pt/C) as a potential co-catalyst for fuel cell anode catalysts. The electrocatalytic activity towards carbon monoxide and methanol oxidation was studied at various temperatures for different RuO2ns loadings. An increase in electrocatalytic activity was evidenced at temperatures above 40 °C, while little enhancement in activity was observed at room temperature. The RuO2ns modified Pt/C catalyst with composition of RuO2:Pt = 0.5:1 (molar ratio) exhibited the highest methanol oxidation activity. CO-stripping voltammetry revealed that RuO2ns promotes oxidation of adsorbed CO on Pt. In addition to the enhanced initial activity, the RuO2ns modified Pt/C catalyst exhibited improved stability compared to pristine Pt/C against consecutive potential cycling tests. 相似文献
57.
In the post-weld heat treatment process, the reheat cracking which might occur in the weldments of low-alloy steels has been a serious problem. So, it is considered to be important to predict the possibility of occurrence of reheat cracking in these steels. It is however recognized as a time-consuming procedure to evaluate quantitatively the susceptibility to this type of cracking. In the present study, a new quantitative evaluation method of reheat cracking susceptibility by in situ observation and measurement using a laser confocal microscope has been proposed. Through this new method, the reheat cracking susceptibility of any kind of steels can be evaluated with the same standard. Moreover, because the position of the initial crack can be focused and the critical ductility to initiate the crack is measured by in situ observation, the reheat cracking susceptibility can be evaluated using only one specimen. So the newly developed method can provide efficient quantitative assessment of the reheat cracking sensitivity with high accuracy. 相似文献
58.
59.
J. Saida A. D. Setyawan H. Kato A. Inoue 《Metallurgical and Materials Transactions A》2011,42(6):1450-1455
Cooling process in the production of Zr65Al7.5Ni10Cu17.5-based bulk metallic glasses (BMGs) was investigated in various chamber atmospheres in Cu mold casting. Two different cooling
modes, consisting of the direct heat transfer between the melt and Cu mold in the high temperature and indirect transfer via cavity in the low-temperature regions, are suggested. In the later case, the cooling effect should depend on the chamber
atmosphere, which results in the formation of glassy structure with large relaxation enthalpy casting under the ambient Ar
and He atmospheres due to a good thermal conductivity. The less relaxed BMGs produced by an improved cooling effect are also
expected to contain a large amount of free volume for significant deformability. Actually, it is clarified that the compressive
plastic deformation is improved with an increase of the relaxation enthalpy. The present study indicates a necessity of development
of the glassy structure, i.e., relaxation state, and provides a new technique of the formation of less relaxed glassy structure for the improvement of
plasticity in BMGs. 相似文献
60.
Yong-Jin Pu Makoto Yoshizaki Takahiro Akiniwa Ken-ichi Nakayama Junji Kido 《Organic Electronics》2009,10(5):877-882
3,5-Dipyrenylpyridine (PY1) and 2,6-dipyrenylpyridine (PY2) were synthesized to achieve not only efficient electron injection from cathode but also high electron mobility. The both of compounds showed much higher electron mobilities than that of Alq3, and have a similar ionization potential and electron affinity. However, the barrier height of electron injection from cathode to PY1 in an organic light emitting device was much smaller than that to PY2, probably due to the steric hindrance to the central pyridine group. These results suggest that the chemical affinity of electron-transporting materials with cathode is more important than their own electron affinity to improve the electron injection. 相似文献