全文获取类型
收费全文 | 1180篇 |
免费 | 65篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 44篇 |
化学工业 | 336篇 |
金属工艺 | 34篇 |
机械仪表 | 23篇 |
建筑科学 | 15篇 |
矿业工程 | 1篇 |
能源动力 | 61篇 |
轻工业 | 116篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 49篇 |
一般工业技术 | 202篇 |
冶金工业 | 207篇 |
原子能技术 | 19篇 |
自动化技术 | 131篇 |
出版年
2024年 | 2篇 |
2023年 | 27篇 |
2022年 | 24篇 |
2021年 | 47篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 42篇 |
2017年 | 38篇 |
2016年 | 42篇 |
2015年 | 20篇 |
2014年 | 59篇 |
2013年 | 72篇 |
2012年 | 52篇 |
2011年 | 72篇 |
2010年 | 58篇 |
2009年 | 65篇 |
2008年 | 41篇 |
2007年 | 45篇 |
2006年 | 39篇 |
2005年 | 40篇 |
2004年 | 22篇 |
2003年 | 38篇 |
2002年 | 24篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 26篇 |
1998年 | 62篇 |
1997年 | 42篇 |
1996年 | 37篇 |
1995年 | 16篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1986年 | 1篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 3篇 |
排序方式: 共有1246条查询结果,搜索用时 15 毫秒
101.
Ryo Watada Makoto Ohsaki Yoshihiro Kanno 《Structural and Multidisciplinary Optimization》2011,43(4):459-471
Uniqueness and symmetry of solution are investigated for topology optimization of a symmetric continuum structure subjected
to symmetrically distributed loads. The structure is discretized into finite elements, and the compliance is minimized under
constraint on the structural volume. The design variables are the densities of materials of elements, and intermediate densities
are penalized to prevent convergence to a gray solution. A path of solution satisfying conditions for local optimality is
traced using the continuation method with respect to the penalization parameter. It is shown that the rate form of the solution
path can be formulated from the optimality conditions, and the uniqueness and bifurcation of the path are related to eigenvalues
and eigenvectors of the Jacobian of the governing equations. This way, local uniqueness and symmetry breaking process of the
solution are rigorously investigated through the bifurcation of a solution path. 相似文献
102.
Keiji Tsukada Mitsuteru Yoshioka Yoshihiko Kawasaki Toshihiko Kiwa 《NDT & E International》2010,43(4):323-328
We have developed a magnetic flux leakage (MFL) system using magnetic resistive (MR) sensors for detecting two dimensional magnetic field components, and an induction coil that generates low magnetic field strengths and extremely low frequencies. The signal at each scanned measurement point (i) was divided by the signal strength Mmes,i and phase αi by a lock-in amplifier. Using the strength Mmes,i and phase αi, we calculated the imaginary part of the signal using the common phase β. By optimization of the common phase β to the imaginary part, the analyzed scanning data curve was shown to be effective in estimating the size (depth and diameter) of back-side pits on a ferrous plate. Comparing the two dimensional magnetic field components of leakage, the imaginary part of the y-component parallel to the induced magnetic field was found to be suitable for detecting the back-side pits. 相似文献
103.
Tomohito Kameda Takashi Yamazaki Toshiaki Yoshioka 《Microporous and mesoporous materials》2008,114(1-3):410-415
Mg–Al layered double hydroxides (Mg–Al LDHs) intercalated with benzenesulfonate (BS–) and benzenedisulfonate (BDS2–) ions were prepared by coprecipitation and characterized by X-ray diffraction, FT-IR spectroscopy, and chemical analyses. The intercalated BS– and BDS2– maintained their intrinsic molecular structures within the Mg–Al LDH interlayers. At low intercalation levels, the benzene ring of BS– in BS · Mg–Al LDH was inclined at 30° relative to the plane of the brucite-like layers of Mg–Al LDH. With increasing BS– content, the benzene ring adopted an additional configuration perpendicular to the Mg–Al LDH layers. In BDS-intercalated Mg–Al LDH, the benzene ring of BDS2– was tilted at 26° relative to the plane of the Mg–Al LDH layers. Intercalation levels of BDS2– were smaller than those of BS– despite the greater charge density of BDS2–, which was likely attributable to a greater degree of electrostatic repulsion between intercalated anions. 相似文献
104.
Yuki Matsushita Junko Taniguchi Ryo Toda Hiroki Ikegami Taku Matsushita Mitsunori Hieda Nobuo Wada 《Journal of Low Temperature Physics》2008,150(3-4):342-346
We have studied heat capacities of 4He adsorbed in straight nanopores 1.8, 2.2, and 2.8 nm in diameter. Heat capacities of the 4He fluid film on the solid layer at 0.08–0.4 K show power laws close to T in 1.8 nm pores, close to T
2 in 2.8 nm pores, and a crossover from T to T
2 with increasing temperature in 2.2 nm pores. These heat capacities are explained by a model assuming a phonon dispersion
with continuous one-dimensional (1D) states in the axial direction and discrete energy levels in the azimuthal direction.
By fitting experimental data to the model, the phonon velocity along the pore axis and the energy gap for propagation in the
cross section are derived. At temperatures sufficiently lower than the energy gap, where the thermal wave length of phonons
is much longer than the effective pore diameter, the 4He fluid films show a T-linear heat capacity of 1D phonons propagating only along the pore axis. At higher temperatures, a 1D-2D crossover of phonons
occurs.
相似文献
105.
A Study was made on certain properties of the cation-exchange membranes obtained by the preirradiation grafting of α,β,β-trifluorostyrene (TFS) noto poly(ethylene-tetrafluoroethylene) (ETFE), followed by sulfonation and hydrolysis of the grafted film. Swelling, water uptake, electric conductivity, and transport number of the membranes were measured as a function of ino-exchange capacity. Thermal and chemical stability were also investigated. These properties were found to be mainly dependent on ion-exchange capacity. The stable membrane properties were established due to a homogeneous ion-exchange group distribution in the membrane, as confirmed by x-ray imcroscopy analysis of the membrane cross sections. In addition, the membranes showed good electrochemical, thermal, and chemical properties, and were found to be scceptable for practical use as cation-exchange membranes. 相似文献
106.
Ryo Sakamaki Bo Cheng Jingnan Cai Yuan-Hua Lin Ce-Wen Nan Jinliang He 《Journal of the European Ceramic Society》2010,30(1):95-99
TiO2-enriched CaCu3(Mn0.1Ti3.9)O12 (CCMTO) ceramics have been prepared by a two-step method. X-ray diffraction (XRD) and TEM results indicate that TiO2 particles were partially coated on the surface of CCMTO powders. The dielectric spectra of TiO2-enriched CCMTO samples showed that the dielectric constant was almost independent of the measured frequency and the dielectric loss was markedly suppressed by increasing the addition of TiO2. The grain activation energy was calculated and an increase in energy was observed with the addition of TiO2. This transformation gave influence to grain charge mobility and resulted in transformed dielectric behaviors. 相似文献
107.
Shingo Maeda Yusuke Hara Ryo Yoshida Shuji Hashimoto 《International journal of molecular sciences》2010,11(1):52-66
Many kinds of stimuli-responsive polymer and gels have been developed and applied to biomimetic actuators or artificial muscles. Electroactive polymers that change shape when stimulated electrically seem to be particularly promising. In all cases, however, the mechanical motion is driven by external stimuli, for example, reversing the direction of electric field. On the other hand, many living organisms can generate an autonomous motion without external driving stimuli like self-beating of heart muscles. Here we show a novel biomimetic gel actuator that can walk spontaneously with a worm-like motion without switching of external stimuli. The self-oscillating motion is produced by dissipating chemical energy of oscillating reaction. Although the gel is completely composed of synthetic polymer, it shows autonomous motion as if it were alive. 相似文献
108.
109.
Yang Gao Junya Iihama Daiki Hamana Ryo Iwasaki Sawao Honda Toru Asaka Munni Kumari Tomokatsu Hayakawa Samuel Bernard Philippe Thomas Yuji Iwamoto 《International Journal of Applied Ceramic Technology》2023,20(2):768-779
A series of β-SiAlON:Eu2+ phosphors were synthesized from single-source precursors, perhydropolysilazane chemically modified with Al(OCH(CH3)2)3, AlCl3, and EuCl2. The single-source precursors were converted to β-SiAlON:Eu2+ phosphors by pyrolysis under flowing N2 or NH3 at 1000°C, followed by heat treatment at 1800°C under an N2 gas pressure at 980 kPa. By varying the molar ratio of the chemical modifiers, β-SiAlON:Eu2+ with the compositions close to the theoretical ones expressed as Si6−zAlzOz−2yN8−z+2y:yEu2+ were synthesized, where the z values and Eu2+ contents were controlled in the ranges of .44–.78 and .35–1.48 mol%, respectively. The polymer-derived β-SiAlON:Eu2+ phosphors exhibited green emission under excitation at 460 nm attributed to the 4f7–4f6(7f3)5d1 transition of dopant Eu2+. High-angle annular dark-field-scanning transmission microscopy analysis confirmed that the doped-Eu2+ existed interstitially within the channels along the c axis of host β-SiAlON. Compared with the conventional powder metallurgy route, the polymer-derived ceramic route in this study offers some advantages in the grain growth of host β-SiAlON and photoluminescence properties in terms of green emission intensity under excitation at 460 nm, and the highest intensity was achieved for the polymer-derived β-SiAlON:Eu2+ with z = .64 and .37 mol% Eu2+. 相似文献
110.
The industrially important yeast Candida utilis is widely used in production of food and medical materials, but its host-vector system has not been well developed. We screened for compact and efficient ARSs to construct practically useful vectors. The C. utilis strain AHU3053 was found to be efficiently transformed by the conventional lithium acetate method and was used as the host. The C. utilis IAM4264 genomic library was constructed by inserting the partial Sau3AI digests in pRI51, which has a kanMX gene expressible in C. utilis. By examining 98 C. utilis G418-resistant transformants, five plasmids had the highest ARS activity. By trimming of the inserts, the 1490 and 552 bp fragments with transformation activity of over 10(3)/microg DNA were obtained from ARS3 and ARS4, respectively. Although several sequences identical to S. cerevisiae ARS consensus sequences (ACSs) were found in ARS3 and ARS4, our deletion analysis indicated that these were not essential for the activity. Because the minimal functional ARS fragment was also several-fold larger than that of S. cerevisiae, the C. utilis ARSs have some unique characteristics resembling the Sz. pombe ARSs. These ARSs were functional in other C. utilis strains tested and useful for constructing practical vectors. 相似文献