全文获取类型
收费全文 | 1782篇 |
免费 | 64篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 100篇 |
综合类 | 4篇 |
化学工业 | 489篇 |
金属工艺 | 46篇 |
机械仪表 | 31篇 |
建筑科学 | 36篇 |
矿业工程 | 1篇 |
能源动力 | 64篇 |
轻工业 | 189篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 126篇 |
一般工业技术 | 322篇 |
冶金工业 | 259篇 |
原子能技术 | 27篇 |
自动化技术 | 154篇 |
出版年
2023年 | 11篇 |
2022年 | 19篇 |
2021年 | 31篇 |
2020年 | 19篇 |
2019年 | 18篇 |
2018年 | 42篇 |
2017年 | 32篇 |
2016年 | 52篇 |
2015年 | 40篇 |
2014年 | 51篇 |
2013年 | 83篇 |
2012年 | 77篇 |
2011年 | 102篇 |
2010年 | 86篇 |
2009年 | 89篇 |
2008年 | 96篇 |
2007年 | 83篇 |
2006年 | 61篇 |
2005年 | 53篇 |
2004年 | 44篇 |
2003年 | 48篇 |
2002年 | 53篇 |
2001年 | 42篇 |
2000年 | 33篇 |
1999年 | 45篇 |
1998年 | 114篇 |
1997年 | 68篇 |
1996年 | 49篇 |
1995年 | 51篇 |
1994年 | 42篇 |
1993年 | 20篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1979年 | 4篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1969年 | 7篇 |
1968年 | 3篇 |
1967年 | 5篇 |
排序方式: 共有1854条查询结果,搜索用时 15 毫秒
1.
2.
The World robot summit disaster robotics category – achievements of the 2018 preliminary competition
Satoshi Tadokoro Tetsuya Kimura Masayuki Okugawa Katsuji Oogane Hiroki Igarashi Yoshikazu Ohtsubo 《Advanced Robotics》2019,33(17):854-875
The World Robot Summit is a robot Olympics and aims to be held in a different country every four years from 2020. The concept of the Plant Disaster Prevention challenge is daily inspections, checks, and emergency response in industrial plants, and in this competition, robots must carry out these types of missions in a mock-up plant. The concept of the Tunnel Disaster Response and Recovery challenge is emergency response to tunnel disasters, and is a simulation competition whereby teams compete to show their ability to deal with disasters, by collecting information and removing debris. The Standard Disaster Robotics challenge assesses, in the form of a contest, the standard performance levels of a robot that are necessary for disaster prevention and emergency response. The World Robot Summit Preliminary Competition was held at Tokyo Big Sight in October 2018, and 36 teams participated in the Disaster Robotics Category. UGVs and UAVs contended the merits of new technology for solving complex problems, using core technologies such as mobility, sensing, recognition, performing operations, human interface, autonomous intelligence etc., as well as system integration and implementation of strategies for completing missions, gaining high-level results. 相似文献
3.
M Furuta K Hayakawa S Katano Y Saito Y Nakayama T Takahashi R Imai T Ebara N Mitsuhashi H Niibe 《Canadian Metallurgical Quarterly》1996,26(2):95-98
Vaccination with peptides that induce a specific immune response is a potential prophylactic or therapeutic strategy against viral infections and tumors. Because of the extensive polymorphism of the HLA loci, synthetic peptide vaccines must consist of a cocktail of peptides that bind specifically to different HLA molecules. Such cocktails should be optimized for the target population as each population has its specific HLA gene frequencies. To achieve maximum population coverage with a minimum number of peptides, information is needed on the ranking of the most frequent HLA phenotypes. We introduce the minimal phenotype panel, which is the smallest combination of HLA antigens selected so that the proportion of individuals in a population that express at least one of the antigens in the panel exceeds a desired minimum value. We developed a method for assembling minimal phenotype panels based on known HLA class I gene frequencies. We give an example based on a set of 2446 well-defined HLA-typed, random, healthy, unrelated, Dutch Caucasoid individuals. In addition, we discuss the possibility of assembling minimal phenotype panels based on two-locus haplotypes, which enables the assembly of phenotype panels from the antigens of both loci. 相似文献
4.
Tetsuya Nanba Shouichi Masukawa Atsushi Ogata Junko Uchisawa Akira Obuchi 《Applied catalysis. B, Environmental》2005,61(3-4):288-296
The catalytic decomposition of acrylonitrile (AN) over Cu-ZSM-5 prepared with various Cu loadings was investigated. AN conversion, during which the nitrogen atoms in AN were mainly converted to N2, increased as Cu loading increased. N2 selectivities as high as 90–95% were attained. X-ray diffraction measurements (XRD) and temperature-programmed reduction by H2 (H2-TPR) showed the existence of bulk CuO in Cu-ZSM-5 with a Cu loading of 6.4 wt% and the existence of highly dispersed CuO in Cu-ZSM-5 with a Cu loading of 3.3 wt%. Electron spin resonance measurements revealed that Cu-ZSM-5 contains three forms of isolated Cu2+ ions (square-planar, square-pyramidal, and distorted square-pyramidal). The H2-TPR results suggested that in Cu-ZSM-5 with a Cu loading of 2.9 wt% and below, Cu+ existed even after oxidizing pretreatment. The activity of AN decomposition over Cu/SiO2 suggested that CuO could form N2, but, independent of the CuO dispersion, nitrogen oxides (NOx) were formed above 350 °C. Cu+ and the square-pyramidal and distorted square-pyramidal forms of Cu2+ showed low activity for AN decomposition. Temperature-programmed desorption of NH3 suggested that N2 formation from NH3 proceeded on Cu2+, resulting in the formation of Cu+. The Cu+ ions were oxidized to Cu2+ at around 300 °C. Thus, high N2 selectivity over Cu-ZSM-5 with a wide range of temperature was probably attained by the reaction over the square-planar Cu2+, which can be reversibly reduced and oxidized. 相似文献
5.
H Toyoda Y Fukuda Y Koyama J Takamatsu H Saito T Hayakawa 《Canadian Metallurgical Quarterly》1997,26(5):975-982
BACKGROUND/AIMS: To study the effects of the immunosuppression caused by the reduction of CD4 activity on the composition of hepatitis C virus (HCV) populations, we analyzed the number of HCV quasispecies clones and the nucleotide diversity of the hypervariable region 1 (HVR1) of HCV in 37 patients with hemophilia with persistent HCV infection, with or without human immunodeficiency virus (HIV). METHODS: The numbers of HCV quasispecies clones were measured by fluorescence single-strand conformation polymorphism analysis. Direct sequencing was used to analyze the degree of diversity of HVR1. We compared these values according to coinfection with HIV, and CD4 counts of patients. RESULTS: There were no differences in either the number of HCV clones or the diversity between patients with and without HIV coinfection. In HIV coinfected patients the diversity decreased in association with the decrease in CD4 count while the number of HCV clones did not. The diversity of HVR1 was 3.64 +/- 5.03% in patients with a CD4 count < 50/microliters and 14.92 +/- 6.03% in patients with a CD4 count > or = 50/microliters; it was significantly lower in the former (p = 0.0002). CONCLUSIONS: A severe reduction in the CD4 count, which is considered to cause a decline in the activity of helper T-lymphocytes, induced changes in the composition of HCV populations; one or a few quasispecies clones are predominant in the HCV population in the serum of individual patients. 相似文献
6.
A cryogenic power cable is expected to be capable of carrying bulk power as a main transmission line in a future metropolitan electric power system. It is important to establish a strategy of how to sustain power supply when such a highly densified power supply route trips from the network due to contingency. It is proposed here that the bulk power transmitted by the cryogenic cable could be distributed into the parallel conventional transmission lines by suitable circuit breaker operations in the system. In this process, power-flow routes are forced to be changed with a remarkable modification in the system configuration. In this paper, the power swings associated with the large power-flow change following contingent faults are analyzed by means of a transient network analyzer. It is found that the proposed system modification could be realized without any harmful power swing if the parameters in generators as well as in control devices have conventional magnitudes. It is shown also by simulations that the margin to occurrence in an unstable power swing is left sufficient even if the parameters deviate somewhat from the present magnitudes. 相似文献
7.
Cold-rolling texture and partially recrystallized texture of polycrystalline 3 pct Si-Fe were investigated using high-resolution
electron backscattered diffraction (EBSD) method. From the measurement on a deformed grain with {211}〈011〉∼{111}〈011〉 orientations,
deformation bands with {12 4 1}〈014〉 orientation were found. It turned out that the orientation rotation relationship between
deformation bands and surrounding deformed grain can be explained by the activation of the slip system, which has a common
slip plane with an adjacent grain. Oriented nucleation of recrystallized grains with {12 4 1}〈014〉 orientation was observed
in a deformed grain with {211}〈011〉∼{111}〈011〉 orientation. Exactly the same orientation relationship that was observed between
deformed grain and the deformation bands was also observed between the deformed grain and the recrystallized grain. A hypothesis
that recrystallization nuclei are generated directly from the deformation bands formed by an activation of the slip system
that has a common slip plane of neighboring deformed grains was proposed from the present experimental results. 相似文献
8.
The non-hookean stress-strain response of carbon fibres was investigated in relation to changes in crystallite orientation with tensile stress. Various one-dimensional array models and a mosaic model were examined. Amongst these models, only the mosaic model in which the stress of the crystallites can be transmitted in both the transverse and the axial directions showed any quantitative agreement with the measured increases in the tensile modulus and the crystallite orientation with tensile stress. This suggests that deformation of the crystallites is constrained with increasing tensile stress. It was also found that the ratio of the tensile stress of the fibre to that of the crystallites is close to the crystallite volume fraction rather than the ratio of the fibre density to the crystallite density. 相似文献
9.
Tetsuya Suemitsu Yoshino K. Fukai Hiroki Sugiyama Kazuo Watanabe Haruki Yokoyama 《Microelectronics Reliability》2002,42(1):47-52
The reliability of InP-based HEMTs is studied, focussing on how it is affected by the doped layer material and gate recess structure. Bias-and-temperature stress tests reveal that fluorine-induced donor passivation in the recess region, formed adjacent to the gate electrode, causes the source resistance (Rs) to increase at large drain bias voltages. The increase in Rs can be prevented by using InP or InAlP as the carrier supply layer material instead of InAlAs. On the other hand, the increase in the drain resistance (Rd) does not depend on the material of the carrier supply layer, which suggests that a mechanism different from that in the case of Rs should be considered. It is also found that a deep gate recess suppresses the increase in Rd after long-term stressing. 相似文献
10.
T Watanabe H Goto T Arisawa S Hase Y Niwa T Hayakawa J Asai 《Canadian Metallurgical Quarterly》1997,12(9-10):660-665
In order to evaluate the relationship between local immune response to Helicobacter pylori and the diversity of disease, 77 asymptomatic subjects who underwent a health examination were studied. Helicobacter pylori-specific IgG in serum and H. pylori-specific IgA in gastric juice were measured by ELISA, and the measured IgA titre was classified into two grades, low or high. Histological classification of gastritis was performed according to the Sydney system. Cytokines in gastric juice were also measured, and the cytotoxin-associated gene A (cagA) status of H. pylori was tested by PCR. Of the 65 subjects who were positive for H. pylori-specific IgG in serum, 38 (58.5%) were classified as H. pylori-specific IgA low titre in gastric juice and 27 (41.5%) had high titres. In the IgG-positive, IgA-low group, the rate of peptic ulcers (especially duodenal ulcers) in endoscopic findings was higher (P < 0.05); the score of activity and the density of H. pylori were higher (P < 0.001 and P < 0.05, respectively); the score of metaplasia was lower (P < 0.05); and the level of interleukin-1 beta was lower (P < 0.05) than in the IgG-positive, IgA-high group. The positive rate of the cagA gene was 84.4% and there was no significant difference between the two groups. There were differences in endoscopic and histological findings between the IgG-positive, IgA-low and the IgG-positive, IgA-high groups. It is suggested that persons infected with H. pylori can be divided into two different states of disease according to local immune response. 相似文献