全文获取类型
收费全文 | 1500篇 |
免费 | 35篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 121篇 |
化学工业 | 363篇 |
金属工艺 | 78篇 |
机械仪表 | 49篇 |
建筑科学 | 37篇 |
能源动力 | 60篇 |
轻工业 | 140篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 150篇 |
一般工业技术 | 243篇 |
冶金工业 | 131篇 |
原子能技术 | 44篇 |
自动化技术 | 123篇 |
出版年
2023年 | 5篇 |
2021年 | 18篇 |
2020年 | 8篇 |
2019年 | 15篇 |
2018年 | 22篇 |
2017年 | 21篇 |
2016年 | 20篇 |
2015年 | 18篇 |
2014年 | 32篇 |
2013年 | 87篇 |
2012年 | 64篇 |
2011年 | 95篇 |
2010年 | 53篇 |
2009年 | 90篇 |
2008年 | 88篇 |
2007年 | 54篇 |
2006年 | 55篇 |
2005年 | 47篇 |
2004年 | 52篇 |
2003年 | 59篇 |
2002年 | 36篇 |
2001年 | 25篇 |
2000年 | 31篇 |
1999年 | 38篇 |
1998年 | 61篇 |
1997年 | 46篇 |
1996年 | 37篇 |
1995年 | 29篇 |
1994年 | 35篇 |
1993年 | 32篇 |
1992年 | 20篇 |
1991年 | 27篇 |
1990年 | 13篇 |
1989年 | 21篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 23篇 |
1978年 | 9篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有1544条查询结果,搜索用时 15 毫秒
41.
Koichiro Hirano Masafumi Fukuda Mikio Takano Yoshio Yamazaki Toshiya Muto Sakae Araki Nobuhiro Terunuma Masao Kuriki Mitsuo Akemoto Hitoshi Hayano Junji Urakawa 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2006,560(2):233-239
A multi-bunch photo-cathode RF gun system has been developed as an electron source for the production of intense quasi-monochromatic X-rays based on inverse Compton scattering. The desired multi-bunch beam is 100 bunches/pulse with a total charge of 500 nC and a bunch spacing of 2.8 ns. We modified the gun cavity of a ‘BNL-type IV’ RF gun to allow a CsTe cathode plug in the end plate. The system uses a four-dipole chicane beam line to allow the injection of laser light normal to the cathode surface. We compensate the gun cavity beam loading caused by the high-intensity multi-bunch electron beam by injecting the laser pulse before RF power has filled the cavity. We have achieved a total intensity of 220 nC in 100 bunches with a bunch-to-bunch energy spread under 1.3% (peak-to-peak). This paper concentrates on experiments to generate the high-intensity multi-bunch beam with compensation of the bunch-to-bunch energy spread due to heavy beam loading. 相似文献
42.
Hitoshi Takamura Hiroshi Sugai Masato Watanabe Takehiro Kasahara Atsunori Kamegawa Masuo Okada 《Journal of Electroceramics》2006,17(2-4):741-748
The preparation and oxygen permeation properties of the (Ce0.8Pr0.2)O2−δ − x vol% MnFe2O4 composites, where x = 0 to 35, have been investigated. The samples were prepared by the Pechini method. In the case of Ce0.8Pr0.2O2−δ, an oxygen flux density of 6 μmol⋅cm−2⋅s−1 (L = 0.0247 cm) and the maximum methane conversion of 50% were attained at 1000∘C. Unlike composites consisting of Gd-doped CeO2 and MnFe2O4, the oxygen permeability of the (Ce0.8Pr0.2)O2−δ – x vol% MnFe2O4 composites was almost constant regardless of the volume fraction of MnFe2O4; however, the optimum volume fraction of MnFe2O4 was determined to be 5 to 25 in the context of the chemical and mechanical stabilities under methane conversion atmosphere.
In addition, the surface modification of the (Ce0.8Gd0.2)O2−δ – 15 vol% MnFe2O4 composite was performed by using the FePt nanoparticles. The catalyst loading of 2.8 mg/cm2 on the both side of the 0.3 mm-thick (Ce0.8Gd0.2)O2−δ – 15vol% MnFe2O4 composite increased the oxygen flux density from 0.30 to 0.76 μmol⋅cm−2⋅s−1 in the case of He/air gradients; however, the effect seems to be reduced in the case of high oxygen flux density caused by
a large pO2 gradient. Moreover, the Langmuir-Blodgett film of the FePt nanoparticles were successfully prepared on the tape-cast (Ce0.8Gd0.2)O2−δ – 15vol% MnFe2O4 composite. Hydrophobic treatments for the surface of the composite were crucial to achieve high transfer ratio for the deposition
of the LB film. 相似文献
43.
44.
Quinjiao Wang Kenji Itaka Hideki Minami Hitoshi Kawaji Hideomi Koinuma 《Science and Technology of Advanced Materials》2004,5(5-6):543
La1−xCaxVO3 composition-spread film library was fabricated by combinatorial pulsed laser deposition and their thermoelectric properties were evaluated paralelly by the multi-channel probes of Seebeck coefficient and electric conductivity. Concurrent X-ray analysis verified the formation of solid soluted films in the full composition range (0x1) as judged from the linear variation of the lattice constants. The Seebeck coefficients of La1−xCaxVO3 changed from a large negative value to almost zero with the increase of x, due presumably to the variation of valence in vanadium ions.The power factor in this library was as high as 0.6 μW/cm K2, which was obtained at x=0, i.e. pure LaVO3 grown at 800 °C. 相似文献
45.
Hitoshi Iyatomi Author Vitae Masafumi Hagiwara Author Vitae 《Pattern recognition》2004,37(10):2049-2057
An adaptive fuzzy inference neural network (AFINN) is proposed in this paper. It has self-construction ability, parameter estimation ability and rule extraction ability. The structure of AFINN is formed by the following four phases: (1) initial rule creation, (2) selection of important input elements, (3) identification of the network structure and (4) parameter estimation using LMS (least-mean square) algorithm. When the number of input dimension is large, the conventional fuzzy systems often cannot handle the task correctly because the degree of each rule becomes too small. AFINN solves such a problem by modification of the learning and inference algorithm. 相似文献
46.
Application of an ultrahigh-resolution scanning electron microscope (UHS-T1) to biological specimens
Keiichi Tanaka Akira Mitsushima Yuzuru Kashima Takashi Nakadera Hitoshi Osatake 《Microscopy research and technique》1989,12(2):146-154
In 1985 we developed an ultrahigh-resolution scanning electron microscope with a resolution of 0.5 nm. It is equipped with a field emission gun and an objective lens with a very short focal length. In this study we report a survey of some different preparation techniques and biological specimens using the new scanning electron microscope. Intracellular structures such as cell organelles were observed surprisingly sharper than those observed by ordinary scanning electron microscopes. However, at magnifications over 250,000 X, platinum particles could be discerned as scattered pebbles on the surface of all structures in coated materials. Using an uncoated but conductively stained specimen, we successfully observed ribosomes on a rough endoplasmic reticulum at a direct magnification of 1 million. In these images some protrusions were recognized on the ribosomes. Ferritin and immunoglobulin G were used as samples of biological macromolecules. These samples were observed without metal coating and conductive staining. The ferritin particles appeared as rounded bodies without any substructure on the surface and immunoglobulin G as complexes of three-unit bodies. In the latter the central body might correspond to the Fc fragment and two side ones to Fab fragments. We assume that ultrahigh-resolution scanning electron microscopy is an effective means for observation of the cell fine structures and biological macromolecules. It will open a new research field in biomedicine. 相似文献
47.
Relationship between particle erosion and lamellar microstructure for plasma-sprayed alumina coatings 总被引:5,自引:0,他引:5
The lamellar structure determines mechanical properties of a thermal spray coating. A model for the erosion of thermally sprayed ceramic coatings resulting from the debonding of flattened ceramic particles is proposed based on the examination of the erosion mechanism. The relationship between erosion rate and microstructural parameters is established both experimentally and theoretically to reveal main lamellar structural parameters controlling erosion of thermally sprayed ceramic coating. The microstructural parameters include the mean bonding ratio between lamellae and thickness of the lamellae. The erosion rate of plasma-sprayed Al2O3 coatings was measured at impact angle of 90° under the fixed erosion test conditions. The correlation of theoretical model with the observed structural parameters and erosion data of alumina coatings was examined. It is revealed that the theoretical relationship agreed well with the observed relation. The results clearly revealed that the erosion of plasma-sprayed ceramic coating was inversely proportional to the mean lamellar bonding ratio. The influences of spray parameters on erosion effected mainly through their influences on the lamellar bonding. The erosion resistance of a thermally sprayed ceramic coating was controlled by coating fracture toughness. 相似文献
48.
Estimations have been made, resulting in a general method for the prediction of the incubation time for cavitation erosion using various cavitating conditions and materials. From a single erosion test, the incubation time can be estimated for various conditions and materials by plotting the mass loss as a function of exposure time to cavitation on a log–log scale. 相似文献
49.
Takayoshi Yokoya Rikiya Yoshida Yuki Utsumi Koji Tsubota Hiroyuki Okazaki Takanori Wakita Yoshikazu Mizuguchi Yoshihiko Takano Takayuki Muro Yukako Kato Hiroshi Kumigashira Masaharu Oshima Hisatomo Harima Yoshihiro Aiura Hitoshi Sato Akihiro Ino Hirofumi Namatame Masaki Taniguchi Masaaki Hirai Yuji Muraoka 《Science and Technology of Advanced Materials》2012,13(5)
We have characterized the electronic structure of FeSe1−xTex for various x values using soft x-ray photoemission spectroscopy (SXPES), high-resolution photoemission spectroscopy (HRPES) and inverse photoemission spectroscopy (IPES). The SXPES valence band spectral shape shows that the 2 eV feature in FeSe, which was ascribed to the lower Hubbard band in previous theoretical studies, becomes less prominent with increasing x. HRPES exhibits systematic x dependence of the structure near the Fermi level (EF): its splitting near EF and filling of the pseudogap in FeSe. IPES shows two features, near EF and approximately 6 eV above EF; the former may be related to the Fe 3d states hybridized with chalcogenide p states, while the latter may consist of plane-wave-like and Se d components. In the incident electron energy dependence of IPES, the density of states near EF for FeSe and FeTe has the Fano lineshape characteristic of resonant behavior. These compounds exhibit different resonance profiles, which may reflect the differences in their electronic structures. By combining the PES and IPES data the on-site Coulomb energy was estimated at 3.5 eV for FeSe. 相似文献
50.