全文获取类型
收费全文 | 536篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 92篇 |
金属工艺 | 17篇 |
机械仪表 | 10篇 |
建筑科学 | 8篇 |
矿业工程 | 1篇 |
能源动力 | 22篇 |
轻工业 | 32篇 |
水利工程 | 2篇 |
石油天然气 | 2篇 |
无线电 | 65篇 |
一般工业技术 | 110篇 |
冶金工业 | 124篇 |
原子能技术 | 5篇 |
自动化技术 | 33篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 15篇 |
2011年 | 30篇 |
2010年 | 8篇 |
2009年 | 16篇 |
2008年 | 17篇 |
2007年 | 21篇 |
2006年 | 10篇 |
2005年 | 18篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 17篇 |
1998年 | 43篇 |
1997年 | 34篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 15篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1976年 | 5篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有543条查询结果,搜索用时 15 毫秒
101.
The interaction between surge and rotating stall in an axial flow compressor was investigated from the viewpoint of an unsteady inner flow structure. The aim of this study was to identify the key factor that determines the switching phenomenon of a surge cycle. The main feature of the tested compressor is a shock tube connected in series to the compressor outlet through a diaphragm, slits, and a concentric duplex pipe: this system allows surge and rotating stall to be generated by connecting the shock tube with the compressor, or enables the compression plane wave injection. The unsteady characteristics and the internal flow velocity fluctuations were measured in detail, and the stall cell structure was averaged and visualized along the movement of the operation point under a coexisting state of surge. A coefficient of the cell scale fluctuation was calculated using the result of the averaging, and it confirmed that the processes of inner flow structure change differed from each other according to the next cycle of the surge. The result suggests that the key factor that determines the next cycle is the transformation of the internal flow structure, particularly between the stall cell and the entire circumferential stall, in both the recovering and stalling processes. 相似文献
102.
Four acid treatments: acetic acid (FA), citric acid (FC), hydrochloric acid (FH) and lactic acid (FL) were used in this study to extract the pepsin-solubilised collagen (PSC) containing melanin from silky fowl feet. The collagen content, melanin content, electrophoresis and ultraviolet (UV) absorption spectra (200–400 nm) were determined in order to develop a collagen with UV protection. Among four acid extractions, the acetic acid treatment had both the highest extracting yield (7.3%) and collagen content (516.6 mg/g). PSCs obtained from silky fowl feet using four acid extractions exhibited melanin content; whereas no similar observations were found in that of broiler feet by acetic acid extraction (FB). Moreover, the PSC via acetic acid extraction resulted in the significantly highest melanin content (210 mg/g) (P < 0.05), which contributed to UV absorption. In electrophoresis, three subunits were found in PSCs from silky fowl feet using the four acid extractions, which were different from typical type I collagen and assumed that the PSCs obtained from silky fowl feet consisted of more than two types of collagens. 相似文献
103.
Bibhu P. Swain Hidetaka TakatoZhengxin Liu Isao Sakata 《Solar Energy Materials & Solar Cells》2011,95(1):84-88
Surface passivation has been recognized as a crucial step in the evaluation of minority carrier lifetime of photovoltaic materials as well as in the fabrication of high efficient solar cells. Dilute acids of HF and HCl are employed for germanium (Ge) surface passivation. An effective lifetime of passivated Ge wafers has been evaluated by a microwave photoconductive decay (μ-PCD) measurement. Surface recombination velocities, S, of H- and Cl-terminated Ge surfaces are 23 and 37 cm/s, respectively. The stability of passivated Ge surfaces against exposure to air has also been examined. The HCl-passivated Ge surfaces are found to be more robust than HF-passivated surfaces. 相似文献
104.
Tadahiro Kin Takaya Kawagoe Shouhei Araki Yukinobu Watanabe 《Journal of Nuclear Science and Technology》2017,54(10):1123-1130
We conducted a feasibility study for producing a high-purity medical radioisotope 64Cu from natural zinc with accelerator-based neutrons. 64Cu isotopes were produced via the 64Zn(n,p) reaction. The accelerator-based neutrons were generated via the C(d,n) reaction using low-energy deuterons of 9 and 12 MeV on a 1-mm-thick carbon target. First, the production purity was estimated using the evaluated nuclear data library JENDL-4.0 and our previously measured thick target neutron yield. We found that even when natural zinc was used as the starting material, significantly high-purity 64Cu could be obtained. Next, irradiation experiments for producing 64Cu using natural zinc were conducted at Kyushu University Tandem Laboratory, with the amounts of 64Cu isotopes and other gamma-emission nuclides measured by a high-purity germanium detector. As a result, high-purity 64Cu isotopes of 1.11(49) × 100 and 3.70 (17) × 100 Bq/g/μC were produced with incident deuteron energies of 9 and 12 MeV, respectively. 相似文献
105.
H. Sakata 《Journal of Modern Optics》2013,60(18):2753-2761
A dual-period grating is proposed that can change the period and the phase difference in the grating structure, allowing the switchable diffraction allocation of transmitted light. Liquid crystal is assumed to be a variable-refractive-index medium confined in the grating grooves. The distribution of the transmitted diffraction efficiencies is analysed using a rigorous diffraction analysis for dual-period gratings and this reveals that the efficiencies can be maximized among the zeroth-, first-, and second-order waves successively according to the refractive index change in the liquid crystal. The analytical model provides insight into the operation of the device and emphasizes its potential application as an optical beam deflector with large deflection angles. 相似文献
106.
The transient plane-stress response of a piezothermoelastic circular disk to axisymmetric heat input is investigated. Solutions to the equations of equilibrium and electrostatics are obtained using a potential function approach. The disk is assumed to exhibit hexagonal material symmetry of crystal class 6 mm. Initially the disk is at zero temperature; thereafter one face is exposed to linear heat transfer, while the opposite face is kept at zero temperature. Both faces are taken to be traction-free. The cylindrical edge of the disk is thermally insulated, electrically charge-free, and constrained against radial deformation. Numerical results are obtained for the induced elastic displacements, stresses, electric potential, and electric displacements in a cadmium selenide disk; and the results are compared with those based on an exact three-dimensional solution. 相似文献
107.
108.
Summary This paper deals with a smart composite disk for control of a thermoelastic deformation resulting from an unknown thermal
load. The disk consists of a structural layer onto which piezoelectric sensor and actuator layers are bonded. First, an unknown
heating temperature distribution is inferred from a sensor output. The thermoelastic displacement on the bottom free surface
is then controlled by applying electric potentials to electrodes on the actuator layers. For a composite disk with one actuator
layer, applied electric potentials are determined by solving a direct optimization problem with and without stress constraints,
respectively. The introduction of the stress constraints leads to a deterioration in the effectiveness of the displacement
control. In order to resolve this issue, an approximate optimum design problem of a composite disk with two actuator layers
is solved under stress constraints. As a result, the thermoelastic displacement is satisfactorily controlled to the desired
distribution.
Dedicated to Professor Franz Ziegler on the occasion of his 70th birthday 相似文献
109.
Suturin SM Sokolov NS Banshchikov AG Kyutt RN Sakata O Shimura T Harada J Tabuchi M Takeda Y 《Journal of nanoscience and nanotechnology》2011,11(4):2990-2996
Surface X-ray diffraction was applied to study structure of the fluorite-silicon interface forming upon epitaxial growth of CaF2 on Si(001) surface kept at 750 degrees C. Samples with CaF2 coverage of 1.5-4 (110)-monolayers were grown and in-situ characterized using synchrotron radiation. The 3 x 1-like surface reconstruction was observed in agreement with the previous studies by electron diffraction. Interestingly, a well pronounced splitting of the fractional x 1/3 reflections was revealed. This splitting was ascribed to the effect of antiphase domain boundaries in the row-like structure of the interface layer. The in-plane integrated intensities were used to reconstruct two-dimensional atomic structure of the high-temperature CaF2/Si(001) interface. 相似文献
110.
H. Nakamura H. Funahashi M. Fujimoto M. Iguchi T. Yamasaki T. Machida T. Kato H. Sakata 《Journal of Superconductivity and Novel Magnetism》2011,24(1-2):271-273
We measured the change of T c with the doping of the magnetic and nonmagnetic impurity in Bi2Sr1.6La0.4CuO6+?? (Bi2201). The reduction of T c is about 20% in samples with Zn (1.1%), Ni (1.0%), and Fe (1.2%), and a slight difference was observed among these samples. We also observed the resonance peak at the Zn-impurity site by scanning tunneling spectroscopy at 4.2 K. The observed resonance peak showed the four-fold symmetry, and appeared at approximately ?1.5 meV. 相似文献