全文获取类型
收费全文 | 598篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 106篇 |
金属工艺 | 18篇 |
机械仪表 | 5篇 |
建筑科学 | 11篇 |
能源动力 | 26篇 |
轻工业 | 33篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 43篇 |
一般工业技术 | 124篇 |
冶金工业 | 177篇 |
原子能技术 | 11篇 |
自动化技术 | 34篇 |
出版年
2023年 | 3篇 |
2021年 | 10篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 18篇 |
2012年 | 18篇 |
2011年 | 20篇 |
2010年 | 14篇 |
2009年 | 23篇 |
2008年 | 17篇 |
2007年 | 16篇 |
2006年 | 13篇 |
2005年 | 14篇 |
2004年 | 20篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 75篇 |
1997年 | 40篇 |
1996年 | 30篇 |
1995年 | 14篇 |
1994年 | 13篇 |
1993年 | 17篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 3篇 |
1970年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有610条查询结果,搜索用时 531 毫秒
101.
To improve the cathodic performance of olivine-type LiMnPO4, we investigated the optimal annealing conditions for a composite of carbon with cation doping. Nanocrystalline and the cation-doped LiMn1−xMxPO4 (M = Ti, Mg, Zr and x = 0, 0.01, 0.05 and 0.10) was synthesized in aqueous solution using a planetary ball mill. The synthesis was performed at the fairly low temperature of 350 °C to limit particle size. The obtained samples except for the Zr doped one consisted of uniform and nano-sized particles. The performance of LiMnPO4 was much improved by an annealing treatment between 500 and 550 °C with carbon in an inert atmosphere. A small amount of metal-rich phosphide (Mn2P) was detected in the sample annealed at 900 °C. In addition, 1 at.% Mg doping for Fe enhanced the rate capability in our doped samples. The discharge capacity of LiMn0.99Mg0.01PO4/C was 146 mAh/g at 0.1 mA/cm2 and 125 mAh/g even at 2.0 mA/cm2. 相似文献
102.
David D. Kitts Anika Singh Farahnaz Fathordoobady Brenda Doi Anubhav Pratap Singh 《Journal of food science》2019,84(11):3147-3155
103.
In Vivo Simultaneous Analysis of Gene Expression by Dual-Color Luciferases in Caenorhabditis elegans
Both fluorescent and luminescent observation are widely used to examine real-time gene expression patterns in living organisms. Several fluuorescent and luminescent proteins with specific optical properties have been developed and applied for simultaneous, multi-color observation of more than two gene expression profiles. Compared to fluorescent proteins, however, the application of multi-color luminescent imaging in living organisms is still limited. In this study, we introduced two-color luciferases into the soil nematode C. elegans and performed simultaneous analysis of two gene expression profiles. Using a green-emitting luciferase Eluc (emerald luciferase) and red-emitting luciferase SLR (stable luciferase red), the expression patterns of two genes were simultaneously observed in single animals from embryonic to adult stages over its whole life span. In addition, dual gene activities were observed at the single embryo level, with the simultaneous observation of morphological changes. These are the first application of a two-color luciferase system into a whole animal and suggest that precise relationship of expression patterns of multiple genes of interest can be analyzed over the whole life of the animal, dependent on the changes in genetic and/or environmental conditions. 相似文献
104.
The sliding friction coefficients and specific wear of SiC ceramics coated with a silicon thin film (Si/SiC) with and without subsequent Ar+ irradiation against a diamond pin were measured with a pin-on-disk tester at room temperature in laboratory air of approximately 50% relative humidity without oil lubrication for 40 h. The friction coefficient of Ar+-irradiated Si/SiC was about 0.05 with a normal load of 9.8 N and remained almost unchanged during the 40 h test, while that of SiC increased from 0.04 to 0.12 during the test. The silicon deposition also reduced the specific wear of SiC to less than one tenth of that of the uncoated SiC. Effectively no wear was detected in Si/SiC irradiated to doses of over2×1016ions cm−2. 相似文献
105.
Effects of phase changes on reflection and their wavelength dependence in optical profilometry 总被引:1,自引:0,他引:1
The method as well as an appropriate instrumentation for measuring phase changes of reflected light is described. The phase changes on samples of Au, Al, Ag, and Cr evaporated films are measured for five wavelengths (lambda) from 442 to 633 nm, with respect to the phase change at the glass-air interface, where it should be zero. The measured results for the Au film are in fairly good agreement with values calculated by use of optical constants from a handbook or the complex refractive index measured by an ellipsometer. The phase changes for Al and Ag films are different from calculated values by ~5 degrees or a shift length of 4.4 nm at lambda = 633 nm, while those of the Cr film show large shifts as high as 16 degrees or a shift length of 9.8 nm at lambda = 442 nm. 相似文献
106.
Seiichi Suda Koichi Kawahara Mitsunobu Kawano Hiroyuki Yoshida Toru Inagaki 《Journal of the American Ceramic Society》2007,90(4):1094-1100
Matrix-type nickel oxide (NiO)/samarium-doped ceria (SDC) composite particles, in which NiO and SDC nano-particles were homogeneously dispersed, were synthesized by spray pyrolysis (SP) for an anode precursor of intermediate-temperature solid oxide fuel cells (IT-SOFCs). SP of an aqueous solution containing Ni, Ce, and Sm salts resulted in capsule-type composite particles that had NiO enveloped with SDC. The capsule-type composite particles actually prevent Ni aggregation between particles, but they cannot have a large contact area between nickel (Ni) and SDC. A matrix-type composite particle is expected to have a large contact area because the matrix-type composite is comprised of nanometer-sized Ni and SDC particles. An adequate addition of ethylene glycol successfully resulted in matrix-type NiO/SDC composite particles. The matrix-type composite particles also showed higher anode performance than the capsule-type composite particles in these experiments and they were effective as precursors of high-performance IT-SOFC anodes. 相似文献
107.
To improve the damage threshold of hollow optical waveguides for transmitting Q-switched Nd:YAG laser pulses, we optimize the metallization processes for the inner coating of fibers. For silver-coated hollow fiber as the base, second, and third Nd:YAG lasers, drying silver films at a moderate temperature and with inert gas flow is found to be effective. By using this drying process, the resistance to high-peak-power optical pulse radiation is drastically improved for fibers fabricated with and without the sensitizing process. The maximum peak power transmitted in the fiber is greater than 20 MW. To improve the energy threshold of aluminum-coated hollow fibers for the fourth and fifth harmonics of Nd:YAG lasers, a thin silver film is added between the aluminum film and the glass substrate to increase adhesion of the aluminum coating. By using this primer layer, the power threshold improves to 3 MW for the fourth harmonics of a Q-switched Nd:YAG laser light. 相似文献
108.
109.
A Yamamoto E Shimizu E Takeuchi H Houchi H Doi H Bando T Ogura S Sone 《Canadian Metallurgical Quarterly》1999,56(2):129-133
To clarify the host immune response and explore a new serological marker of lung cancer, we examined serum c-Myc antigens and auto-antibodies against c-Myc in 68 lung cancer patients and 30 healthy volunteers using bacterially synthesized glutathione S-transferase c-Myc fusion proteins and immunoblotting. The detection rate of anti-c-Myc antibodies was 13.2% (9/68) in lung cancer patients and 3.3% (1/30) in healthy volunteers. These anti-c-Myc antibodies were directed toward exon 2 alone (4/68), exon 3 alone (1/68), and both exon 2 and exon 3 (4/68) of c-Myc. Circulating c-Myc antigen was not detected in any individuals with lung cancer and normal controls. Age, sex, performance status, histology, stage, smoking history, and prior treatment of the patients with and without anti-c-Myc antibodies were not significantly different. The low incidence of anti-c-Myc antibodies and c-Myc antigens in peripheral blood suggests that these examinations are not useful in the serological diagnosis of lung cancer. 相似文献
110.
BACKGROUND: Overexpression of the 70 kDa heat shock protein (Hsp70) protects myocytes and neural cells from hypoxic injury. In contrast, Hsp70 induction in the kidney after ischemic or thermal preconditioning does not correlate well with protection from hypoxic injury. Herein, we directly tested if Hsp70 overexpression protects LLC-PK1 porcine tubular epithelial cells from hypoxic or thermal injury. METHODS: LLC-PK1 cells were either cotransfected with an Hsp70 and a luciferase expression vector or singly transfected with the luciferase expression vector. Loss of intracellular luciferase activity was used to assess injury after exposure to hypoxia or hyperthermia and after recovery under normal growth conditions. RESULTS: Overexpression of Hsp70 decreased loss of and improved restoration of intracellular luciferase activity in LLC-PK1 cells exposed to hyperthermia. In contrast, Hsp70 overexpression did not decrease the loss of or improve restoration of luciferase activity in cells exposed to hypoxia. CONCLUSIONS: These results suggest that Hsp70 overexpression is sufficient to protect LLC-PK1 proximal tubular cells from hyperthermia but is not sufficient for protection from hypoxia. 相似文献