全文获取类型
收费全文 | 1819篇 |
免费 | 38篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 83篇 |
综合类 | 1篇 |
化学工业 | 373篇 |
金属工艺 | 47篇 |
机械仪表 | 29篇 |
建筑科学 | 24篇 |
能源动力 | 86篇 |
轻工业 | 173篇 |
水利工程 | 1篇 |
无线电 | 163篇 |
一般工业技术 | 348篇 |
冶金工业 | 384篇 |
原子能技术 | 35篇 |
自动化技术 | 119篇 |
出版年
2023年 | 7篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 6篇 |
2019年 | 22篇 |
2018年 | 22篇 |
2017年 | 21篇 |
2016年 | 20篇 |
2015年 | 14篇 |
2014年 | 26篇 |
2013年 | 79篇 |
2012年 | 76篇 |
2011年 | 77篇 |
2010年 | 57篇 |
2009年 | 68篇 |
2008年 | 62篇 |
2007年 | 74篇 |
2006年 | 53篇 |
2005年 | 50篇 |
2004年 | 52篇 |
2003年 | 66篇 |
2002年 | 46篇 |
2001年 | 49篇 |
2000年 | 37篇 |
1999年 | 38篇 |
1998年 | 145篇 |
1997年 | 80篇 |
1996年 | 73篇 |
1995年 | 52篇 |
1994年 | 52篇 |
1993年 | 53篇 |
1992年 | 24篇 |
1991年 | 31篇 |
1990年 | 24篇 |
1989年 | 21篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1974年 | 6篇 |
1973年 | 5篇 |
排序方式: 共有1866条查询结果,搜索用时 788 毫秒
151.
Transparent lutetium aluminum garnet (Lu3Al5O12, LuAG) was fabricated by reactive spark plasma sintering. The effect of sintering temperature on the crystal phase, microstructure, transparency and mechanical properties of LuAG bodies was investigated. Fully dense and single-phase LuAG bodies were obtained at sintering temperatures 1573–1923 K. The average grain size increased from 0.18 to 0.52 μm with increasing sintering temperature from 1573 to 1773 K, and grain growth became significant at 1823 K. Transmittance showed a maximum value of 77.8% at 2000 nm at a sintering temperature of 1773 K after annealing at 1423 K in air for 43.2 ks. The Vickers hardness increased from 14.2 to 17.2 GPa with decreasing grain size from 7.45 to 0.23 μm. 相似文献
152.
1-Naphthyl isocyanide was polymerized with Ni(II) catalyst in a cholesteric matrix at the liquid crystal (LC) temperature range. The resultant polymers showed optical activity. In this reaction, the structural chirality of cholesteric LC effectively functions to impart one-handed helicity on the corresponding polymers as an optically active atropisomer. 相似文献
153.
Tetsuro Hori Naoki Fukuoka Tetsuya Masuda Yasuo Miyake Hiroyuki Yoshida Akihiko Fujii Yo Shimizu Masanori Ozaki 《Solar Energy Materials & Solar Cells》2011,95(11):3087-3092
Bulk heterojunction solar cells utilizing soluble phthalocyanine derivative, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2) have been investigated. The active layer was fabricated by spin-coating the mixed solution of C6PcH2 and 1-(3-methoxy-carbonyl)-propyl-1-1-phenyl-(6,6)C61 (PCBM). The photovoltaic properties of the solar cell with bulk heterojunction of C6PcH2 and PCBM demonstrated the strong dependence of active layer thickness, and the optimized active layer thickness was clarified to be 120 nm. By inserting MoO3 hole transport buffer layer between the positive electrode and active layer, the FF and energy conversion efficiency were improved to be 0.50 and 3.2%, respectively. The tandem organic thin-film solar cell has also been studied by utilizing active layer materials of C6PcH2 and poly(3-hexylthiophene) and the interlayer of LiF/Al/MoO3 structure, and a high Voc of 1.27 V has been achieved. 相似文献
154.
Akihiko Ito Yu You Hirokazu Katsui Takashi Goto 《Journal of the European Ceramic Society》2013,33(13-14):2655-2661
Ba β-alumina films were prepared by laser chemical vapor deposition. Mostly single-phase Ba β-alumina films were obtained at 1125–1200 K and for an Al/Ba molar ratio of 12.4–16.6. BaAl2O4 and α-Al2O3 were codeposited with Ba β-alumina under Ba- and Al-rich conditions, respectively. The Ba β-alumina films consisted of hexagonal grains, and the (1 1 0)-oriented Ba β-alumina films had a fin-like columnar structure. The highest deposition rate reached 120 μm h?1 at around 1200 K. A thin layer of Ba-rich superstructure was formed on the surface of the (1 1 0)-oriented columnar grains. 相似文献
155.
The rates which particles from JIS Test Powders 1, Class 2 (silica sand), Class 3 (silica sand), Class 16 (calcium carbonate, heavy), and JIS Test Powder 2, Class GBM-20 (barium titanate glass) settled out of homogenous suspensions were determined using the principles of the buoyancy weighing-bar method as well as a sedimentation balance. Samples were standardized by Japanese Industrial Standard, and the dispersing agent was NaPP or NaHMP, while the viscosity improver was a starch syrup solution. Although constructing a handmade sedimentation balance is difficult, developing a handmade weighing tool capable of measuring particle size distribution is easy. Herein three weighing-bars, which were composed of aluminum, stainless steel, and copper, were used to measure the particle size distribution. However, an aluminum slit-cylinder occasionally replaced the weighing-bars. The weighing data obtained via an analytical balance were controlled by connecting the balance to a personal computer with an RS-232C interface, and the determined particle size agreed well with the data obtained by Andreasen analyses and the sedimentation balance. 相似文献
156.
Previous studies have demonstrated an infiltration of monocytes and increased levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the asthmatic lung. To study the possible effects of this cytokine upon the differentiation and function of these newly recruited monocytes, we have developed a model in which monocytes isolated from human peripheral blood were differentiated into macrophages in serum in the presence or absence of GM-CSF. After 7 days, the macrophages increased in size and granularity, had increased phagocytic activity, and expressed various adhesion molecules, CD14 and major histocompatibility complex (MHC) class II. The effects of GM-CSF on antigen presentation by cultured macrophages on the antigen-specific proliferative response of CD4+ T cells to Dermatophagoides pteronyssinus or purified protein derivative of tuberculin and the mitogen phytohaemagglutinin was determined. CD4+ T-cell proliferation was reduced when either antigen was presented by macrophages cultured in serum alone, compared with the values obtained with freshly isolated monocytes. However, CD4+ cell proliferation was comparable to that observed with monocytes when antigen was presented by macrophages which had been pre-cultured with 50 U/ml GM-CSF. CD4+ T-cell proliferation to phytohaemagglutinin was similar when all three populations were used as accessory cells. High numbers of macrophages partially suppressed CD4+ T-cell proliferation in response to antigen presented by monocytes, but there was no significant difference between macrophages cultured in the presence or absence of GM-CSF. This data suggests that GM-CSF directs monocyte differentiation into macrophages with an antigen-presenting, rather than a suppressive, phenotype. Elevated levels of GM-CSF in the asthmatic lung may therefore maintain recently recruited monocytes in an inflammatory and T-cell activating state. 相似文献
157.
Input energy to mechano-catalytic water-splitting system is transferred partly to organize the frictional electric condenser (FEC) system, which motivates the water-splitting, and partly to rotate the slurry. A part of the rotational energy is regained as a feedback, while the remainder is wasted to the dispersion loss through the viscous motion. The mechanism of the cyclic transfer of charge between the stirrer (Teflon), the vessel wall (Pyrex glass) and the semiconductor particles (NiO, etc.) is discussed. System efficiency, dynamic efficiency, energy conversions and the dispersion processes are analyzed. System design of the cell and the stability of FEC system are discussed as well. 相似文献
158.
Temperature dependencies of the shear viscosity of a Finemet glassy alloy under the heating rates ranging from 0.3 to 100 K/min are obtained. It is shown that isothermal cuts of these dependencies give linear viscosity increase with the inverse heating rate that accords with the flow equation derived within the framework of the directional structural relaxation model. 相似文献
159.
M Ohta N Matsuno K Isobe J Kuyama Y Uchida K Nasu H Ikehira K Uno 《Canadian Metallurgical Quarterly》1997,22(7):494-496
An unusual case of dislocation of the midfoot through the calcaneocuboid and naviculocuneiform joints is presented. The prognosis is excellent for most midfoot dislocations, as long as they are recognized and treated early. 相似文献
160.
T Fujimatsu M Tsunemoto M Shimada Y Ohta S Endo A Ishizawa K Koike M Akagi T Watari J Kobayashi 《Canadian Metallurgical Quarterly》1990,10(1):76-80
This report concerns a 10-month-old infant with subtotal cor triatrium associated with left sided partial anomalous pulmonary venous connection to the innominate vein. In the operation, we found that the fossa ovalis existed between the right atrium and the accessory atrial chamber. We performed a radical operation which consisted of a resection of the intra-left-atrial diaphragma and a anastomosis of the vertical vein to the left atrium. His postoperative course was uneventful, and the result was satisfactory. We have presented and reviewed our case, and then discussed the embryogenesis and the hemodynamics. To our knowledge, our case represents the first successful surgical repair of this combination of defects in Japan. 相似文献