首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   604篇
  免费   13篇
  国内免费   2篇
电工技术   74篇
综合类   1篇
化学工业   121篇
金属工艺   11篇
机械仪表   9篇
建筑科学   5篇
能源动力   8篇
轻工业   24篇
水利工程   2篇
无线电   51篇
一般工业技术   96篇
冶金工业   165篇
原子能技术   37篇
自动化技术   15篇
  2023年   4篇
  2022年   6篇
  2021年   9篇
  2020年   4篇
  2019年   11篇
  2018年   16篇
  2017年   9篇
  2016年   11篇
  2015年   4篇
  2014年   10篇
  2013年   22篇
  2012年   12篇
  2011年   11篇
  2010年   16篇
  2009年   27篇
  2008年   20篇
  2007年   22篇
  2006年   14篇
  2005年   10篇
  2004年   6篇
  2003年   7篇
  2002年   12篇
  2001年   17篇
  2000年   16篇
  1999年   14篇
  1998年   52篇
  1997年   34篇
  1996年   26篇
  1995年   18篇
  1994年   23篇
  1993年   13篇
  1992年   11篇
  1991年   8篇
  1990年   7篇
  1989年   9篇
  1988年   8篇
  1987年   18篇
  1986年   7篇
  1985年   7篇
  1984年   8篇
  1983年   6篇
  1982年   4篇
  1981年   5篇
  1980年   12篇
  1979年   3篇
  1978年   4篇
  1977年   4篇
  1976年   10篇
  1975年   3篇
  1974年   5篇
排序方式: 共有619条查询结果,搜索用时 15 毫秒
91.
92.
93.
In our search for molecules involved in the process of osteoclast differentiation, we examined the surface phenotypes of the preosteoclast-like cells and osteoclast-like multinucleated cells (MNCs) formed in bone marrow cultures, using monoclonal antibodies recognizing different antigen molecules expressed on hematopoietic cells. Among these cell surface antigens, lymphocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) were highly expressed on mononuclear cells in the cultures for forming preosteoclast-like mononuclear cells. The double detection of these two antigen molecules with osteoclast-specific antigen and with calcitonin receptor, using a fluorescence-activated cell sorter or autoradiography technique, revealed that LFA-1 and ICAM-1 were expressed on the preosteoclasts. The expression of ICAM-1 was detected on both preosteoclasts and osteoclast-like MNCs, whereas the expression of LFA-1 was restricted to preosteoclasts. We designed a peptide with the sequence of the binding site of ICAM-1 against the ligand LFA-1. In the whole bone marrow culture system for forming osteoclast-like MNCs, a significant inhibition of MNC formation was observed by the addition of this peptide. These results strongly suggest the involvement of an LFA-1/ICAM-1-interaction in osteoclastogenesis.  相似文献   
94.
95.
Accumulation of amyloid-β peptide is associated with Alzheimer's dementia. Previously, we reported that sesamin and sesamolin inhibited β-secretase activity in vitro, and each was transported to the serum and brain in mice after oral administration. However, the bioavailability of sesamin and sesamolin was poor in mice. In this study, we aimed to improve the bioavailability of sesamin and sesamolin. We found that the levels of sesamin and sesamolin in mouse serum and brain were higher after the administration of a mixture of sesame extract and turmeric oil (MST) than those after administering sesame extract alone. Serum sesamin and sesamolin contents in the MST-treated group were 23-fold and 15-fold higher, respectively, than those in the sesame extract-treated group. Brain sesamin and sesamolin contents in the MST-treated group were 14-fold and 11-fold higher, respectively, than those in the sesame extract-treated group. These results suggest that turmeric oil is an effective solvent to enhance the bioavailability of sesamin and sesamolin.  相似文献   
96.
To quantitatively investigate the initial crystallization of zeolite beta synthesized by direct heating, the extent of the reaction was precisely evaluated by X-ray diffraction measurements and Rietveld structural refinement, and a kinetic analysis of crystallization was performed using the Avrami-Erofe'ev equation. The activation energy for crystallization was lower than that for hydrothermal synthesis. Reaction and synthesis time curves revealed that the initial zeolite beta crystallization consisted of three stages. The first was an induction period with nucleation by the generation of building units and the formation of an initial coordinated structure. The second stage was crystal growth by a diffusion-controlled reaction, and the third stage involved slowing down of crystallization by the limitation of dehydrocondensation. These stages could be analyzed by calculation of the rate constant and Avrami exponent for each stage.  相似文献   
97.
ABSTRACT

The thermal-neutron capture cross-section (σ0) and resonance integral (I0) were measured for the 135Cs(n,γ)136Cs reaction by an activation method and mass spectrometry. Because of difficulty in the preparation of pure 135Cs samples, we used 135Cs contained as an impurity in a normally available 137Cs standard solution. An isotope ratio of 135Cs and 137Cs in a standard 137Cs solution was measured by mass spectrometry to quantify 135Cs. Cesium-135 impurity along with the 137Cs standard solution was irradiated at the hydraulic conveyer of the research reactor in the Institute for Integral Radiation and Nuclear Science, Kyoto University. Wires of Co/Al and Au/Al alloys were used as neutron monitors to measure thermal-neutron fluxes and epi-thermal Westcott’s indices at an irradiation position. A gadolinium filter was used to measure the σ0, and a value of 0.133 eV was taken as the cut-off energy. Gamma-ray spectroscopy was used to measure induced activities of 137Cs, 136Cs and monitor wires. On the basis of Westcott’s convention, the σ0 and I0 values were derived as 8.57 ± 0.25 barn, and 45.3 ± 3.2 barn, respectively. The value of σ0 obtained in the present study agreed within the limits of uncertainties with the past-reported value of 8.3 ± 0.3 barn.  相似文献   
98.
In this study, the effect of core bar inserted into weld faying part to obtain an ideal pipe joint with nongenerating inner flash via friction welding is described. A steel pipe with inner and outer diameters corresponding to 8.0 mm and 13.5 mm was used, and the weld faying surface was machined to a groove shape of a flat (butt) type. The core bar of various materials was inserted in the weld faying part of the pipes, and those pipes were welded with a friction speed of 27.5 s-1 and friction pressure of 30 MPa. The core bars did not decrease inner flash when joints were fabricated with a core bar of some metallic materials with melting points below that of steel; thus, they were melted during the welding process. The joint with an alumina core bar did not decrease inner flash and was crushed by generating an inner flash. However, a commercially pure tungsten (CP-W) core bar was successfully achieved for decreasing the inner flash. Additionally, all joints with a CP-W core bar did not exhibit the tensile strength of the base metal and a fracture in the base metal, when they were fabricated during the same time, the friction torque reached the initial peak. The joint exhibited a fracture in the base metal when it was fabricated with a CPW core bar and a taper groove shape that was proposed in the previous study. Furthermore, the core bars were easily removed from the joints; thus the joint with almost no inner flash was successfully obtained. To reduce the inner flash of pipe joints, they should be fabricated with a CP-W core bar inserted into the weld faying part with a taper groove shape.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00319-w  相似文献   
99.
A 20Li4SiO4·80Li2WO4 glass was prepared by the rapid quenching technique, and its structure was investigated by X-ray diffraction (XRD) and Raman scattering. The coordination number of the oxygen atoms around a tungsten atom, NO/W, was determined to be 4.8 by XRD and 4.6 by Raman scattering. The deviation of NO/W from 4 resulted from the coexistence of condensed structural units, such as WO6, Si2O6−7 ions containing bridging oxygens, WO2−4 ions, and SiO4−4 ions.  相似文献   
100.
The electrical properties of poly(p-phenylene vinylene) (PPV) Langmuir-Blodgett (LB) films were investigated, wherein transparent indium-tin oxide (ITO) and aluminum (Al) were used as the electrodes. Their I–V characteristics depended strongly on the thickness of PPV LB film, and the electric conductivity of the PPV LB film was in the range of 10−2–10−15 (S/cm). Their C–V characteristics showed that the capacitance was reversibly proportional to the thickness of PPV LB film and was kept constant when the applied voltage changed from −1.0 V to +1.0 V. These results indicated that PPV LB film was an insulator in this range of applied voltage without doping. Under forward bias, yellow-green light emission was observed in PPV LB film based light emitting diodes (LEDs), the highest light emission reached more than 100 cd/m2 in the case that PPV LB film was deposited for 80 layers, i.e. a ITO/PPV(80L)/Al device.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号