全文获取类型
收费全文 | 550篇 |
免费 | 16篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 145篇 |
金属工艺 | 20篇 |
机械仪表 | 6篇 |
建筑科学 | 7篇 |
能源动力 | 12篇 |
轻工业 | 32篇 |
水利工程 | 6篇 |
无线电 | 51篇 |
一般工业技术 | 84篇 |
冶金工业 | 141篇 |
原子能技术 | 9篇 |
自动化技术 | 47篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 16篇 |
2013年 | 26篇 |
2012年 | 22篇 |
2011年 | 27篇 |
2010年 | 20篇 |
2009年 | 23篇 |
2008年 | 34篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 61篇 |
1997年 | 41篇 |
1996年 | 21篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1972年 | 2篇 |
排序方式: 共有569条查询结果,搜索用时 15 毫秒
91.
Hsu HC Kikuchi H Yen SK Nishiyama M 《Journal of materials science. Materials in medicine》2007,18(4):605-609
The properties of several different investments were investigated including phosphate bonded, magnesia bonded, and alumina
cement investments. Measurements included the setting expansion, thermal expansion, and compressive strength of investments,
as well as the tensile strength, elongation, Vickers hardness (VHN) and surface roughness of titanium castings. For phosphate
bonded investment, the setting expansion after being mixed with its own mixing solution was 2.10%, which was larger than the
other investments; the thermal expansion was −0.25% at 200°C, the compressive strength 14 and 5 MPa after heating. For titanium
cast in phosphate bonded investment, the hardness on its top surface was 655 Hv, the tensile strength was 379 MPa, the elongation
was 19.4%, and the surface roughness was 2.29 μm. Athough the thermal expansion of phosphate bonded investment is small, the setting expansion is large enough to compensate
for the shrinkage of titanium castings. As its thermal expansion at T ≥ 600°C was constant and its heating-cooling cycle was almost reversible, these two properties can reduce the thermal shock
and thus avoid cracking of the investment. 相似文献
92.
Oishi M Nagasaki Y Nishiyama N Itaka K Takagi M Shimamoto A Furuichi Y Kataoka K 《ChemMedChem》2007,2(9):1290-1297
PEGylated polyplexes (lac-PEGylated polyplexes) composed of poly(L-lysine) and lactosylated poly(ethylene glycol)-small interfering RNA conjugate, which inhibits the RecQL1 gene product, were revealed to show an appreciable growth inhibition of multicellular HuH-7 spheroids (human hepatocarcinoma cell lines) for up to 21 days (IC(50)=6 nM); this system used as an in vitro three-dimensional (3D) model mimicking the in vivo biology of tumors. The PEGylated polyplexes thus prepared had a size of approximately 110 nm with clustered lactose moieties on their periphery as targeting ligands for the asialoglycoprotein-receptor-expressing HuH-7 cells. In contrast, OligofectAMINE/siRNA (cationic lipoplex) was observed to have almost no growth-inhibitory effect against HuH-7 spheroids, even though the lipoplex showed a stronger growth-inhibitory effect than the lac-PEGylated polyplexes on conventional monolayer-cultured HuH-7 cells. The FITC-tagged conjugate in the lac-PEGylated polyplexes showed smooth penetration into the HuH-7 spheroids compared with that in the lipoplexes, as observed by confocal fluorescence-scanning microscopy. This indicates that the small size of approximately 100 nm and the reduced nonspecific interaction due to the nonionic and hydrophilic lactosylated PEG layer contributes to the smooth penetration of the PEGylated polyplexes into the spheroid interior, eventually facilitating their uptake into the cells composing the spheroids. Cellular apoptosis indicating programmed cell death was also observed in the HuH-7 spheroids treated with the PEGylated polyplexes, revealing that the observed growth inhibition was indeed induced by the RNAi of the RecQL1 siRNA. These data suggest that the smart PEGylated polyplexes can indeed penetrate into the multiple cell layers of 3D tumor masses in vivo, exerting therapeutic effects through the RNAi. 相似文献
93.
Theaccumulation strategy consists of generalizing a function over an algebraic data structure by inclusion of an extra parameter, anaccumulating parameter, for reusing and propagating intermediate results. However, there remain two major difficulties in this accumulation strategy.
One is to determinewhere andwhen to generalize the original function. The other, surprisingly not yet receiving its worthy consideration, is how to manipulate
accumulations. To overcome these difficulties, we propose to formulate accumulations ashigher order catamorphisms, and provide several general transformation rules for calculating accumulations (i.e., finding and manipulating accumulations)
bycalculation-based (rather than a search-based) program transformation methods. Some examples are given for illustration.
Zhenjiang Hu, Dr.Eng.: He is an Assistant Professor in Information Engineering at the University of Tokyo. He received his BS and MS in Computer
Science from Shanghai Jiao Tong University in 1988 and 1990 respectively, and his Dr. Eng. degree in Information Engineering
from the University of Tokyo in 1996. His current research concerns programming languages, functional programming, program
transformation, and parallel processing.
Hideya Iwasaki, Dr.Eng.: He is an Associate Professor in Information Engineering at the University of Tokyo. He received the M.E. degree in 1985,
the Dr. Eng. degree in 1988 from the University of Tokyo. His research interests are list processing languages, functional
languages, parallel processing, and constructive algorithmics.
Masato Takeichi, Dr.Eng.: He is Professor in Mathematical Engineering and Information Engineering at the University of Tokyo since 1993. After graduation
from the University of Tokyo, he joined the faculty at the University of Electro-Communications in Tokyo before he went back
to work at the University of Tokyo in 1987. His research concerns the design and implementation of functional programming
languages, and calculational program transformation systems. 相似文献
94.
95.
The corrosion behavior of various austenitic stainless steels and high-alloy steels has been studied in simulated fluidized bed boiler environment to develop a new corrosion resistant austenitic stainless steel for the superheater tube. The superheater is usually not installed within the bed position, which is different from the evaporator installed within the bed position. Therefore, the superheater tubes are exposed to an oxidizing environment; but it is also necessary to estimate the corrosion resistance of the steels in a reducing environment. It is already known that the high temperature corrosion behavior in conditions where CaSO4 is coated on the steels is more important than the erosion of the superheater tubes. The main results in this present study are as follows: The Nb bearing steels and low C steels showed good resistance to high-temperature corrosion in CaSO4/CaO, e.g. 347, 304L and HR3C. The corrosion rate of all steels used increased with increase in temperature, particularly at temperatures higher than 650°C. Internal penetration was not detected at temperatures lower than 550°C, but it was detected at temperatures higher than 600°C, in particular, higher than 650°C. The corrosion thickness loss was almost the same as the internal penetration depth at 700 and 750°C in the 300 series steels placed in CaSO4/CaO, including the fine grained 347 steel, while the internal penetration depth was larger than the corrosion thickness loss in high-alloyed materials such as Alloy 800 and 310 steels. At temperatures higher than 800°C, the same result was also obtained for the fine grained 347 steel. The corrosion during exposure to oxidizing or reducing gases without CaSO4/CaO or CaS was slight, but when the test specimens were placed in CaSO4/CaO or CaS, the corrosion rate sharply increased, regardless of the atmospheric gas composition. Cr, Si, Mn (less than 5 %), Mo and Nb are beneficial elements while C, Cu and Al are harmful elements. From the above results, the following steel was developed for high temperature corrosion resistance in CaSO4/CaO: low C-22/25Cr-17/25Ni-3/5Mn-(2Mo)-Nb-0.08/0.2N-Al-(B). 相似文献
96.
Isao Saeki Yusuke Sugiyama Shigenari Hayashi Akira Yamauchi Takashi Doi Yoshitaka Nishiyama Shoji Kyo Shigeru Suzuki Masugu Sato Shinji Fujimoto 《Corrosion Science》2012
Changes in the crystal structure of type 430 stainless steel and the oxides on its surface were studied in situ at 1373 K using a high-intensity synchrotron X-ray source provided by SPring-8 in Japan. The surface of the steel was initially covered with Cr2O3, which was then converted to FeCr2O4, and finally Fe3O4 and Fe2O3 formed on it. These results indicated that the reason for the breakaway oxidation in type 430 stainless steel is Cr depletion beneath Cr2O3 layer and the subsequent ionisation of Fe, not the simple mechanical failure of Cr2O3. 相似文献
97.
Naoyuki UenoKouji Nakanishi Toshiaki OhtaYasuyuki Egashira Norikazu Nishiyama 《Thin solid films》2012,520(13):4291-4296
Well-aligned zinc oxide (ZnO) nanorods were synthesized using a low-temperature hydrothermal method employing a zinc/sodium dodecyl sulfate (Zn/SDS) composite as a seed layer. The results of X-ray diffraction measurements indicate that the Zn/SDS composite has a lamellar structure with an interlayer distance of 3.12 nm, which is shorter than that of the lamellar structure of SDS (3.82 nm) due to ion exchange between Zn and Na. The results of X-ray absorption fine structure analyses suggest that ZnO crystals start to grow after an induction period of 20-30 min. The length of nanorods and the aspect ratio of ZnO nanorods could be controlled by altering the molarity of ammonium and zinc nitrate in the growth solutions. 相似文献
98.
Uota M Hayashi Y Ohyama K Takemoto H Iriki R Kishishita T Shimoda M Yoshimura T Kawasaki H Sakai G Kijima T 《Journal of nanoscience and nanotechnology》2010,10(9):5790-5795
Platinum/carbon (Pt/C) composite materials were prepared by the hydrazine reduction of H2PtCl6 confined to a mixed surfactant lytropic liquid crystal (LC)/C mixture with varying amounts of water. The reaction at relatively low water contents successfully yielded cross-linked Pt nanowires with wire-widths of 2-5 nm. The novel Pt nanostructure is believed to be from poorly hydrated hexagonal domains formed together with layered domains by the phase separation of the precursory LC mixture in the presence of carbon. Electrochemical measurements using cyclic volutammetry and membrane electrode assemblies revealed that the cross-linked nanowired Pt/C composite exhibits fairly high electrocatalytic activity for oxygen reduction reaction, as well as a high performance as the cathode material for polymer electrolyte fuel cells. 相似文献
99.
Hosomi Ryota Otsuka Ren Arai Hirofumi Kanda Seiji Nishiyama Toshimasa Yoshida Munehiro Fukunaga Kenji 《Food science and biotechnology》2016,25(1):107-112
In an effort to clarify whether the lipid-lowering effect of hemoglobin is due to globin protein or heme, this study investigated the effects of dietary porcine hemoglobin (PH) and porcine globin (PG) on lipids contents of serum, liver, and feces in rats. Five-week-old male Wistar rats were divided into 3 dietary groups of 7 rats each, with one group receiving a control diet and the other groups receiving diets containing 1.25% (w/w) PH or 1.18% (w/w) PG for 4 weeks. The PH diet decreased triacylglycerol content in serum and cholesterol in serum and liver, whereas the PG diet reduced triacylglycerol content in serum and cholesterol in liver. Fecal lipid excretion in the PH group was significantly higher than in the PG group. Therefore, PH affected lipid excretion to feces due to globin protein as well as heme. 相似文献
100.
Takahiro Kozawa Hideya Hattori Shuhei Ogo Yusuke Ide Yoshikazu Suzuki 《Journal of Materials Science》2013,48(22):7969-7973
A simple and mild synthetic route via a hydrothermal treatment of Mg2TiO4 has been developed to prepare brookite-type TiO2. The hydrothermal conversion of Mg2TiO4 to brookite proceeded in 1 M HCl solution even at 100 °C. The converted brookite grains were composed of the angular particles covered on the textured surface, leaving the original morphology of Mg2TiO4 grains. Compared with the commercially available TiO2 catalysts (rutile, anatase, and P25), the brookite obtained in this study showed a good photocatalytic activity toward the oxidation of benzyl alcohol to benzaldehyde under a simulated sunlight irradiation. 相似文献