全文获取类型
收费全文 | 1488篇 |
免费 | 21篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 103篇 |
化学工业 | 426篇 |
金属工艺 | 26篇 |
机械仪表 | 31篇 |
建筑科学 | 27篇 |
矿业工程 | 1篇 |
能源动力 | 60篇 |
轻工业 | 108篇 |
水利工程 | 1篇 |
石油天然气 | 5篇 |
无线电 | 100篇 |
一般工业技术 | 324篇 |
冶金工业 | 92篇 |
原子能技术 | 39篇 |
自动化技术 | 170篇 |
出版年
2023年 | 3篇 |
2022年 | 25篇 |
2021年 | 23篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 15篇 |
2016年 | 24篇 |
2015年 | 13篇 |
2014年 | 36篇 |
2013年 | 70篇 |
2012年 | 53篇 |
2011年 | 89篇 |
2010年 | 55篇 |
2009年 | 57篇 |
2008年 | 83篇 |
2007年 | 75篇 |
2006年 | 61篇 |
2005年 | 52篇 |
2004年 | 56篇 |
2003年 | 61篇 |
2002年 | 48篇 |
2001年 | 40篇 |
2000年 | 26篇 |
1999年 | 34篇 |
1998年 | 65篇 |
1997年 | 48篇 |
1996年 | 35篇 |
1995年 | 28篇 |
1994年 | 22篇 |
1993年 | 24篇 |
1992年 | 15篇 |
1991年 | 22篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 20篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 19篇 |
1984年 | 25篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1976年 | 9篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1968年 | 4篇 |
排序方式: 共有1513条查询结果,搜索用时 15 毫秒
1.
In a plant consisting of parallelized microreactors (MRs), the product quality is lowered because of a lack of flow uniformity among them when blockage occurs. It is not practical to install sensors in every MR from the viewpoint of cost when detecting the blocked MRs. In the previous study, the multiple blockage detection (MBD) method using a small number of sensors was proposed, but its performance became low when the number of sensors decreased. Here, the conventional algorithm for MBD is improved by considering the process behavior on blockage occurrence, and the effectiveness of the improved algorithm is demonstrated through a numerical case study. The effects of flow distributor types and sensor types on the MBD performance are numerically investigated. 相似文献
2.
3.
On an earthspace propagation path with the low elevation angle of 10 deg, the phase between co- and crosspolar signals occasionally showed rapid and irregular fluctuations during fine weather. These fluctuations were generally significant during the daytime, and were strongly in phase with the occurrence of the copolar amplitude scintillations. This could be attributed to the combined effects of the crosspolar phase pattern of the receiving antenna and small fluctuations of the angle of arrival of the radiowaves. 相似文献
4.
Shinya Yamakawa Shela Aboud Marco Saraniti Stephen M. Goodnick 《Journal of Computational Electronics》2003,2(2-4):481-485
A fast full-band device simulator for wurtzite and zincblende GaN using a Cellular Monte Carlo (CMC) approach is reported for wurtzite and zincblende GaN. The full-phonon dispersion relationship including anisotropic polar-optical phonon scattering is taken into account for the wurtzite GaN calculation. In the bulk simulation, the CMC model is about 30–100 times faster than the conventional Ensemble Monte Carlo model at high electric field region. This CMC model is applied to the simulator of MESFET devices, and the calculation speed is significantly improved. 相似文献
5.
Shingo Hirano Akio Kawabata Masaru Yoshinaka Ken Hirota Osamu Yamaguchi 《Journal of the American Ceramic Society》1995,78(5):1414-1416
A compound denoted as (Ce0.75 Zr0.25 )O2 (Ce, ZrO8 ) is formed near room temperature from cerium and zirconium nitrates using hydrazine monohydrate. It has a cubic unit cell with a = 0.5342 nm. Characterization of powders heated to various temperatures at 10°C/min demonstrates that the specific surface area does not decrease below 20 mVg until >1000°C. 相似文献
6.
Masafumi Itoh Osamu Sakurada Minoru Hashiba Kouichi Hiramatsu Yukio Nurishi 《Journal of Materials Science》1996,31(12):3321-3324
An average shell volume occupied in the adsorption layer on alumina by a polyacrylic acid ammonium salts molecule (PAA) defined as the average area occupied by an adsorbed PAA on alumina multiplied by the average thickness of the water layer at the limit of thickening, has been calculated from the adsorbed amount of PAA and from the flow points of alumina in the presence of PAA of different molecular weights. A steric effect of the PAA dispersant on the dispersion of alumina resulted in a flow with no yield stress. This was due to the change of the extension of PAA in the adsorption shell from a sphere to an ellipsoid with a long axis which exceeded the effective distance that the van der Waals attraction force reaches at a molecular weight for the PAA of between 10 000–20 000. 相似文献
7.
8.
GR Login M Aoki M Yamakawa LO Lunardi EC Digenis N Tanda LB Schwartz AM Dvorak 《Canadian Metallurgical Quarterly》1997,45(10):1379-1391
The subcellular events responsible for release of mediators by mast cells may help to clarify roles for mast cells in health and disease. In this study we show that the granule-associated protease chymase is also within cytoplasmic vesicles in appropriately stimulated rat peritoneal mast cells. Rat peritoneal mast cells were recovered before or 1-10 sec after exposure to the secretogogue compound 48/80 (10 micrograms/ml) and then were examined by radioimmunoassay to quantify histamine release or were processed, using routine methods for postembedding immunoelectron microscopy, to identify the subcellular localization of chymase. In comparison to unstimulated cells, compound 48/80 stimulated cells in two independent experiments showed an increase (15%, 28%) in the surface area of the cell and a decrease (12%, 6%) in the surface area of the total granule compartment before degranulation channel formation. These global cellular changes occurred in a background of transient but significant (p < 0.01) increases in the area and number of chymase-immunoreactive vesicles per microns2 cytoplasm. These changes were detectable at 5 or 7 sec after stimulation with compound 48/80 but returned to near prestimulation levels by 9 or 10 sec after addition of compound 48/80 (total cumulative histamine release was 28% by 8 sec and 47% by 14 sec). These observations suggest that vesicles participate in the early stages of regulated secretion of chymase from rat peritoneal mast cells. 相似文献
9.
Toshimitsu Suzuki Osamu Yamada Yasuhiko Takahashi Yoshihisa Watanabe 《Fuel Processing Technology》1985,10(1):33-43
Hydroliquefaction of low-sulfur Australian coals (Wandoan and Yallourn) was studied using iron carbonyl complexes as catalyst. The addition of Fe(CO)5 (2.8 wt% Fe of coal) increased coal conversion from 48.6 to 85.2% for Wandoan coal, and from 36.7 to 69.7% for Yallourn coal in 1-methylnaphthalene at 425°C under an initial hydrogen pressure of 50 kg cm?2. When molecular sulfur was added to iron carbonyls (Fe(CO)5, Fe2(CO)9 and Fe3(CO)12), higher coal converions ( > 92%) and higher oil yields (>46%) were obtained, along with an increase in the amount of hydrogen transferred to coal from the gas phase (0.2 to 2.8%, d.a.f. coal basis). In the liquefaction studies using a hydrogen donor solvent, tetralin, Fe(CO)5S catalyst increased the amount of hydrogen absorbed from the gaseous phase and decreased the amount of naphthalene dehydrogenated from tetralin. The direct hydrogen transfer reaction from molecular hydrogen to coal fragment radicals seems to be a major reaction pathway. Organic sulfur compounds, dimethyldisulfide and benzothiophene, and inorganic FeS2 and NiS were found to be good sulfur sources to Fe(CO)5. From X-ray diffraction analyses of liquefaction residues, it is concluded that Fe(CO)5 was converted into pyrrhotite (Fe1?xS) when sulfur was present, but into Fe3O4 in the absence of sulfur. 相似文献
10.