全文获取类型
收费全文 | 929篇 |
免费 | 55篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 80篇 |
综合类 | 4篇 |
化学工业 | 251篇 |
金属工艺 | 23篇 |
机械仪表 | 27篇 |
建筑科学 | 24篇 |
能源动力 | 62篇 |
轻工业 | 76篇 |
水利工程 | 3篇 |
无线电 | 73篇 |
一般工业技术 | 209篇 |
冶金工业 | 23篇 |
原子能技术 | 52篇 |
自动化技术 | 80篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 24篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 27篇 |
2017年 | 30篇 |
2016年 | 25篇 |
2015年 | 23篇 |
2014年 | 25篇 |
2013年 | 64篇 |
2012年 | 63篇 |
2011年 | 82篇 |
2010年 | 61篇 |
2009年 | 38篇 |
2008年 | 58篇 |
2007年 | 49篇 |
2006年 | 35篇 |
2005年 | 34篇 |
2004年 | 31篇 |
2003年 | 34篇 |
2002年 | 25篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 18篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有987条查询结果,搜索用时 15 毫秒
21.
Masayuki Kaneda Michinori Yamamoto Koichi Nakaso Tsuyoshi Yamamoto Jun Fukai 《Precision Engineering》2007,31(2):177-184
The seesaw-oscillation of a small circular pad on a single droplet was studied both numerically and experimentally. The circular pad with a diameter of 2.0–3.8 mm onto a water or glycerol droplet with a volume of 1–10 μL, and a bottom substrate with a smaller diameter than that of the pad were used in the experiment. The pad was then tilted and then the tilting fixture was quickly removed. The pad alternately oscillated and then finally stabilized in a horizontal position. The numerical model considering the surface tension and the viscous force of the droplet was developed and calculated using the same configurations as those in the experiment. The experimental and numerical data showed good agreement not only in terms of the oscillating frequency and damping ratio but the transient motion of the circular pad and instantaneous droplet surface shape. 相似文献
22.
Kazuyuki Kakegawa Tsuyoshi Wakapayashi Yoshinori Sasaki 《Journal of the American Ceramic Society》1986,69(4):82-C-
A solution containing Mg2+ and Ta5+ was added to an aqueous ammonia solution of oxine, resulting in a precipitate. After the precipitate was thermally decomposed and fired, it was mixed with BaCO3 powder and fired again at high temperatures to obtain Ba(Mg1/3 Ta2/3 )O3 (BMT). This method resulted in BMT formation at temperatures lower than those used in the conventional mixed-oxide method, and single-phase BMT formed directly at 1300°C without intermediates. 相似文献
23.
Simultaneous extraction by microwave-irradiation and crystallisation were performed in the same pot of solvent of 70% (v/v) aqueous ethanol for isolation of hesperidin from thinned immature fruit peels of Citrus unshiu as refining of Citrus waste biomass. The hesperidin content in immature fruits peels was about 3.2-fold higher than that of mature fruit. After microwave-assisted extraction (MAE), the yield of hesperidin reached 58.6 mg/g, which was comparable to the amount obtained after extraction using DMSO:methanol (1:1, v/v) as a solvent for 30 min at room temperature. Heating temperature and time for isolation of hesperidin crystallites were optimised as 140 °C and 8 min by using response surface methodology. Under this optimal condition, 86.8% (47.7 mg/g) of total hesperidin was isolable by MAE and low-temperature storage (5 °C, 24 h). 相似文献
24.
Yasuda K Nakamoto T Yasuhara M Okada H Nakajima T Kanzaki H Hori M Ozaki H 《Reproduction (Cambridge, England)》2007,133(4):797-806
To assess the role of protein kinase Cbeta (PKCbeta) in human myometrial contractions during pregnancy, we evaluated the effect of a PKCbeta inhibitor (LY333531) on the pregnant and nonpregnant myometrial contractions and compared the level of PKCbeta in the pregnant myometrium with that in the nonpregnant myometrium. The effects of LY333531 on the myometrial contractions were examined by measuring contractile activity (frequency and amplitude). PKCbeta in human myometrium was assessed at mRNA level using real-time PCR method. The characteristics of contractile activity were different between the pregnant and the nonpregnant myometrium. The amplitude of rhythmic contractions in the preterm and term myometrium was increased 2- to 2.5-fold when compared with that in the nonpregnant myometrium, but the frequency of rhythmic contractions was decreased by about half. LY333531 (10(-6) M) reduced the increased amplitude in the preterm and term myometrium by about 50%, and the inhibitory effects of LY333531 in the pregnant myometrium were significantly greater than that in the nonpregnant myometrium (about 50 vs 25%). However, the frequency in the pregnant and nonpregnant myometrium was not influenced by LY333531. Real-time PCR revealed a significant, five- to sevenfold increase in the expression of PKCbeta mRNA in the preterm and term myometrium when compared with the nonpregnant myometrium. These findings suggest that the increased amplitude of human myometrial contractions during pregnancy is related to the increased level of PKCbeta. A PKCbeta inhibitor may reduce preterm uterine contractions and prevent preterm delivery. 相似文献
25.
Hayashi A Aoyagi H Yoshimura T Tanaka H 《Journal of Bioscience and Bioengineering》2007,103(4):358-367
It is becoming increasingly difficult to isolate novel useful microorganisms from the natural environment using conventional screening methods based on pure culture techniques. A novel method for screening microorganisms in symbiotic association with insects was developed. This method involves the following two steps. In the first step, the existence of desired microorganisms that grow well by degrading difficult-to-degrade materials in the gut of insects is detected using the survivability of insects as an indicator. In the second step, the desired microorganisms are selected from the surviving insects. The second step is based on an idea that the guts of insects act as continuous-culture systems whereby microorganisms that cannot degrade diet components are washed out whereas those that can degrade diet components are retained and made to multiply in the gut. Coptotermes formosanus Shiraki was fed with an artificial diet containing phenol as a model of lignin-derived and difficult-to-degrade compound. Each C. formosanus feeding on an artificial diet containing 100 mg/l phenol had different levels of adaptation to the toxicity of phenol. About 20% of C. formosanus fed with an artificial diet containing 100 mg/l phenol died within a few days whereas others survived for more than 10 d. The structure of the intestinal microorganisms of the surviving C. formosanus fed with the 100 mg/l phenol artificial diet gradually changed and was very different from that of the bacterial communities obtained from the enrichment culture of wood-feeding C. formosanus using an artificial medium containing phenol as a sole carbon source. Furthermore, Only three species (as DGGE band) were detected from the gut of wood-feeding C. formosanus, whereas 200 times more phenol-degrading microorganisms were detected in the gut of C. formosanus feeding on a phenol artificial diet. Out of these nine species (as DGGE band) of phenol-degrading microorganisms were isolated. The screening method developed in this study can also be applied to various insects, leading to the isolation of various microorganisms that can degrade difficult-to-degrade compounds. 相似文献
26.
Cationic surfactants containing a thioether group in the hydrophobic chain were prepared by the reaction of alkanethiol and bromocholine bromide. The aqueous solution properties of the thio-surfactants were investigated and compared with conventional cationic surfactants. The Krafft temperatures of the thio-surfactants were lower than that of alkyltrimethylammonium bromide. The critical micelle concentrations were determined by the conductivity method, and pyrene and SPQ fluorescence probe methods. A linear relation was observed for the plots of cmc vs. chain length. However, the cmc of the thio-surfactants depended on the position of the thioether group in the hydrophobic alkyl chain. It was found that the thioether group exhibited quenching ability toward SPQ fluorescence. The variation of the surfactant monomer concentration in equilibrium with micelles can be estimated from Stern-Volmer plots. 相似文献
27.
We prepared a fluorinated gemini surfactant containing a disulfide bond in its spacer chain, [C?F??(CH?)?N(CH?)?CH?CH?SSCH?CH?N(CH?)?(CH?)?C?F??]2Cl, and its analogue with a hexamethylene spacer. Monomeric thiol surfactant, [C?F??(CH?)?N(CH?)?CH?CH?SH]Cl, was readily produced by the cleavage of the gemini surfactant using dithiothreitol in water. The critical micelle concentration was determined using surface tension, conductivity, and fluorescence probe methods. The critical micelle concentration of the monomeric surfactant was significantly larger than that of the gemini surfactant. The surface tension of aqueous solution for the cleaved monomeric thiol surfactant returned gradually to the original value through the formation of the disulfide bond via air oxidation. 相似文献
28.
Tsuyoshi OchiaiYuichi Iizuka Kazuya NakataTaketoshi Murakami Donald A. TrykAkira Fujishima Yoshihiro KoideYuko Morito 《Diamond and Related Materials》2011,20(2):64-67
The electrochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) was achieved by the use of a boron-doped diamond (BDD) electrode. The PFOA decomposition follows pseudo-first-order kinetics, with an observed rate constant (k1) of 2.4 × 10− 2 dm3 h− 1. Under the present reaction conditions, k1 increased with increasing current density and saturated at values over 0.60 mA cm− 2. Therefore, the rate-limiting step for the electrochemical decomposition of PFOA was the direct electrochemical oxidation at lower current densities. In the proposed decomposition pathway, direct electrochemical oxidation cleaves the C-C bond between the C7F15 and COOH in PFOA and generates a C7F15 radical and CO2. The C7F15 radical forms the thermally unstable alcohol C7F15OH, which undergoes F− elimination to form C6F13COF. This acid fluoride undergoes hydrolysis to yield another F− and the perfluorocarboxylic acid with one less CF2 unit, C6F13COOH. By repeating these processes, finally, PFOA was able to be totally mineralized to CO2 and F−. Moreover, whereas the BDD surface was easily fluorinated by the electrochemical reaction with the PFOA solution, medium pressure ultraviolet (MPUV) lamp irradiation in water was able to easily remove fluorine from the fluorinated BDD surface. 相似文献
29.
Daisuke Tashima Eri Yamamoto Nanami Kai Daisuke Fujikawa Go Sakai Masahisa Otsubo Tsuyoshi Kijima 《Carbon》2011,(14):4848-4857
Micro-mesoporous bimodal carbon nanospheres with high surface areas were synthesized by a combined use of surfactant templating technique and BaO2 chemical activation one. Starting spherical nanopolymer/surfactant composites were prepared by the NaOH-catalyzed reaction of resorcinol (R) and formaldehyde (F) in the presence of cetyltrimethylammonium bromide (CTAB) as a core template and 1,3,5-trimethylbenzene (TMB) and tert-butanol (t-BuOH) as cosurfactants. After pretreatment with hydrochloric acid, the composite materials were calcined at 1000 °C in N2 coexistent with varying weight ratios of BaO2 to RF polymer ranging from 0 to 11. It produced micro-mesoporous bimodal carbon nanospheres of 124–143 nm diameter, with specific surface areas as high as 1884 m2 g−1 or up to 3301 m2 g−1, in contrast to microporous ones with smaller surface areas obtained at low BaO2-loadings. The electrochemical double layer capacitance of the resulting nanocarbons in 0.5 M H2SO4 showed a marked increase with specific surface areas, up to as high as 219 F g−1 for the highest surface area carbon material. 相似文献
30.
Keiji Uchiyama Hideyuki Hara Junji Chida Agriani Dini Pasiana Morikazu Imamura Tsuyoshi Mori Hanae Takatsuki Ryuichiro Atarashi Suehiro Sakaguchi 《International journal of molecular sciences》2021,22(21)
Prion diseases are a group of fatal neurodegenerative disorders caused by accumulation of proteinaceous infectious particles, or prions, which mainly consist of the abnormally folded, amyloidogenic prion protein, designated PrPSc. PrPSc is produced through conformational conversion of the cellular isoform of prion protein, PrPC, in the brain. To date, no effective therapies for prion diseases have been developed. In this study, we incidentally noticed that mouse neuroblastoma N2a cells persistently infected with 22L scrapie prions, termed N2aC24L1-3 cells, reduced PrPSc levels when cultured in advanced Dulbecco’s modified eagle medium (DMEM) but not in classic DMEM. PrPC levels remained unchanged in prion-uninfected parent N2aC24 cells cultured in advanced DMEM. These results suggest that advanced DMEM may contain an anti-prion compound(s). We then successfully identified ethanolamine in advanced DMEM has an anti-prion activity. Ethanolamine reduced PrPSc levels in N2aC24L1-3 cells, but not PrPC levels in N2aC24 cells. Also, oral administration of ethanolamine through drinking water delayed prion disease in mice intracerebrally inoculated with RML scrapie prions. These results suggest that ethanolamine could be a new anti-prion compound. 相似文献