全文获取类型
收费全文 | 1915篇 |
免费 | 26篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 80篇 |
综合类 | 1篇 |
化学工业 | 286篇 |
金属工艺 | 29篇 |
机械仪表 | 34篇 |
建筑科学 | 22篇 |
能源动力 | 43篇 |
轻工业 | 96篇 |
水利工程 | 3篇 |
无线电 | 440篇 |
一般工业技术 | 295篇 |
冶金工业 | 461篇 |
原子能技术 | 41篇 |
自动化技术 | 111篇 |
出版年
2022年 | 6篇 |
2021年 | 18篇 |
2020年 | 5篇 |
2019年 | 19篇 |
2018年 | 8篇 |
2017年 | 7篇 |
2016年 | 23篇 |
2015年 | 20篇 |
2014年 | 18篇 |
2013年 | 49篇 |
2012年 | 46篇 |
2011年 | 50篇 |
2010年 | 31篇 |
2009年 | 44篇 |
2008年 | 65篇 |
2007年 | 49篇 |
2006年 | 44篇 |
2005年 | 48篇 |
2004年 | 60篇 |
2003年 | 77篇 |
2002年 | 60篇 |
2001年 | 66篇 |
2000年 | 44篇 |
1999年 | 60篇 |
1998年 | 190篇 |
1997年 | 123篇 |
1996年 | 98篇 |
1995年 | 85篇 |
1994年 | 50篇 |
1993年 | 53篇 |
1992年 | 33篇 |
1991年 | 40篇 |
1990年 | 30篇 |
1989年 | 39篇 |
1988年 | 40篇 |
1987年 | 19篇 |
1986年 | 28篇 |
1985年 | 34篇 |
1984年 | 26篇 |
1983年 | 16篇 |
1982年 | 18篇 |
1981年 | 22篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 15篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有1942条查询结果,搜索用时 250 毫秒
61.
A Zeniya M Otaka H Itoh T Kuwabara S Fujimori S Otani Y Tashima O Masamune 《Canadian Metallurgical Quarterly》1995,30(5):572-577
We investigated the expression and changes in the intracellular localization of a 72-kDa heat shock protein (HSP72) in rat gastric pyloric and fundic mucosa before and after water-immersion stress. Severe mucosal damage was found in the fundic mucosal area of the stomach after this stress. However, no mucosal lesion developed in the pyloric mucosal area. HSP72 in both the soluble and insoluble fractions of the pyloric and the fundic mucosal areas was significantly increased after water-immersion stress, peaking 6h after the initiation of the stress. The increase in HSP72 was more significant in the pyloric mucosal area than in the fundic mucosal area under both normal and stress conditions. The increase of HSP72 in the pyloric mucosal cells occurred prior to the formation of the mucosal lesions, whereas the increase of HSP72 in the fundic mucosal cells was observed after ulcer formation. An immunohistochemical study showed that HSP72 was constitutively expressed in the cytoplasm of the gastric mucosal cells, and that the intranuclear induction of HSP72 was remarkably intense in the pyloric mucosal cells, especially in the proliferative zone, compared with the fundic mucosal cells. Our results may suggest that HSP72 has an important cytoprotective function in gastric mucosal cells and that there is a "biophysical" difference between pyloric and the fundic mucosal cells. 相似文献
62.
Xia Cao Wang Dong F. Ono Takahito Itoh Toshihiro Esashi Masayoshi 《Microsystem Technologies》2022,28(11):2443-2453
Microsystem Technologies - In this paper, a system of magnetically coupled oscillators consisting of a Π-shaped horizontal cantilever and a rectangular vertical cantilever with a frequency... 相似文献
63.
Characteristics of sol-gel derived PZT thin films with lead oxide cover layers and lead titanate interlayers 总被引:1,自引:0,他引:1
The sol-gel derived PbZr0.53Ti0.47O3 (PZT) films were fabricated on the bare Pt/Ti/SiO2/Si substrates or the same substrates coated by the PbTiO3 (PT) interlayers. The post-deposition annealing temperature and time were optimized when the PbO cover layers and PbO vapour-containing atmosphere were compared with each other and adopted as the method to diminish the lead-loss problem during the high-temperature post-deposition annealing. The X-ray diffraction patterns, microstructures, and electrical properties such as relative permittivity, r, remanent polarization, P
r, and coercive electrical field, E
c, were investigated in relation to the annealing conditions. The PZT films deposited on the bare Pt/Ti/SiO2/Si substrates under the PbO vapour-containing atmosphere showed better electrical properties. This indicates that the PbO vapour-containing atmosphere may be the better method of lead-loss-prevention to process the lead-containing films rather than the PbO cover layer method. The electrical characteristics of the PZT films, r=1150, a dissipation factor of 0.039, P
r=26 C cm–2, and E
c=40.5 kV cm–1 were measured at 1 kHz. When PZT films were deposited on substrates coated by the PT layers, PZT-PT films with single perovskite phase were derived by post-deposition annealing at 500 °C for 1 h. However, the relative electrical properties are very poor, i.e. E
r=160, P
r=2.0 C cm–2 and E
c=75 kVcm–1. The optimum combination for preparing PZT-PT films is a 40 nm PbTiO3 interlayer and annealing conditions of 6 h at 550 °C in a PbO vapour-containing atmosphere; the derived films exhibit electrical properties of E
r=885, P
r=21.5 C cm–2 and E
c=64 kV cm–1. The combination of inserting a PT interlayer and annealing in a PbO vapour-containing atmosphere can prevent the formation of electrical short paths. In this case, nearly pin-hole-free PZT films can be grown on the PT (interlayer) /Pt/Ti/SiO2/Si substrates. It is believed that it is possible to prepare the PZT films with nano-scale uniformity, reproducible quality, which may be worth considering for commercial applications. 相似文献
64.
We developed a method to improve the quantitative precision of FDG-PET scans in cancer patients. The total-lesion evaluation method generates a correlation coefficient (r) constrained Patlak parametric image of the lesion together with three calculated glucose metabolic indices: (a) the total-lesion metabolic index ("KT-tle", ml/min/lesion); (b) the total-lesion voxel index ("VT-tle", voxels/lesion); and (c) the global average metabolic index ("KV-tle", ml/min/voxel). METHODS: The glucose metabolic indices obtained from conventional region of interest (ROI) and multiplane evaluation were used as standards to evaluate the accuracy of the total-lesion evaluation method. Computer simulations and four patients with metastatic melanoma before and after chemotherapy were studied. RESULTS: Computer simulations showed that the total-lesion evaluation method has improved precision (% s.d. < 0.6%) and accuracy (approximately 10% error) compared with the conventional ROI method (% s.d. approximately 5%; approximately 25% error). The KT-tle and VT-tle indices from human FDG-PET studies using the total-lesion evaluation method showed excellent correlations with the corresponding values obtained from the conventional ROI methods and multiplane evaluation (r approximately 1.0) and CT lesion volume measurements. CONCLUSION: This method is a simple but reliable way to quantitatively monitor tumor FDG uptake. The method has several advantages over the conventional ROI method: (a) less sensitive to the ROI definition, (b) no need for image registration of serial scan data and (c) includes tumor volume changes in the global tumor metabolism. 相似文献
65.
Thermodynamic evaluation of Cu–Cu3P system has been conducted by applying subregular solution model with Gibbs energy of Cu3P formation that was newly determined by means of triple Knudsen cell mass spectrometry. Both the calculated vapor pressure of phosphorus and phase diagram of Cu–P system are excellently consistent with the literature data in the composition range of Cu–Cu3P, indicating that there is no significant thermodynamic inconsistency between the present work based on the Gibbs energy of Cu3P formation determined and the literature data. 相似文献
66.
Takayuki Kobayashi Hedong Zhang Kenji Fukuzawa Shintaro Itoh 《Microsystem Technologies》2016,22(6):1285-1290
A fundamental understanding of the diffusion phenomena of submonolayer polar liquid films is important for achieving reliable lubrication between moving mechanical parts separated by a nanometer-sized gap. To acquire this understanding, we conducted molecular dynamics (MD) simulations of diffusion phenomena of submonolayer polar perfluoropolyether (PFPE) Zdol films on solid surfaces. To improve the accuracy of these simulations, we developed an all-atom model that includes hydrogen-bond potential and refined atomic charges for Zdol molecules and tested it through MD simulations of spreading of step-shaped submonolayer PFPE films. Our MD simulations reproduced the experimentally observed effects of polar end groups on the diffusion speed and molecular conformation of Zdol. We then conducted MD simulations of self-diffusion of submonolayer Zdol films; these simulations demonstrated that as the thickness of the submonolayer Zdol films decreases, molecular conformation becomes flatter and the self-diffusion coefficient decreases. These changes in molecular conformation partially explain our experimental finding that the spreading of step-shaped submonolayer polar PFPE films slows down with decreasing initial thickness. 相似文献
67.
Kusaka T Ueno M Miki T Kanenishi K Nagai Y Huang CL Okamoto Y Ogawa T Onodera M Itoh S Akiguchi I Sakamoto H 《Microscopy research and technique》2007,70(7):648-655
We investigated whether beta-amyloid (Abeta)-like immunoreactivity was seen in the brains of newborn piglets. The immunoreactivity for Abeta(1-42) and Abeta(1-40) proteins, but not Abeta precursor protein, was present in CD68-positive perivascular cells of the hippocampus and in parts of the meninges. It was colocalized with immunoreactivity for receptor for advanced glycation end product and tumor necrosis factor-alpha. The protein with a molecular mass of 27 kDa, which was recognized by the Abeta antibodies, was identified as triosephosphate isomerase (TPI) with sequence homology to Abeta peptides by N-terminal amino acid sequencing, mass fingerprint analysis using matrix-associated laser desorption/ionization mass spectrometry, and Western blotting. Western blotting assay also revealed that detectable expression of Abeta proteins were not seen in the piglet brains. These findings indicate that TPI with sequence homology to Abeta peptides accumulates in perivascular cells of the microglia/macrophage lineage located around arterial vessels of the newborn piglet hippocampus. 相似文献
68.
In the present paper, we report results of surveys in 2003 in Japan and Denmark about patients' views about adverse events, focusing on the actions of healthcare staff involved in a medical accident. Results show that patients were more likely to indicate negative expectations to a doctor's reactions after a medical accident when asked in general terms than when asked in relation to concrete case stories. When asked in general terms, 66% (47%) of Japanese (Danish) respondents expected that doctors sometimes hold back on providing information to patients about a medical accident, while 37% (7%) did so when asked about a concrete, mild-outcome case. We examine some possible reasons for the relatively high level of distrust of Japanese patients, and we discuss whether the seemingly lower level of disclosure in Japan than in Denmark and the negative stories in the Japanese press may have an impact. We also suggest some implications for introducing a patient-centred or customer-centred approach to risk management in healthcare and other domains. 相似文献
69.
K. M. Itoh W. L. Hansen J. W. Beeman E. E. Haller J. W. Farmer V. I. Ozhogin 《Journal of Low Temperature Physics》1993,93(3-4):307-312
The temperature dependence of variable range hopping resistivity in neutron transmutation doped (NTD) isotopically enriched70Ge:Ga samples is reported. Five samples with compensation ratios K less than 0.001 and Ga concentrations between 3×1016 and 1.77×1017 cm–3 were studied. All samples investigated show the ln T–1/2 dependence in the temperature range below 1.5K. As thermistor materials NTD70Ge:Ga samples are found to have more than factor of two higher sensitivity than commonly used natural NTD Ge in the temperature range between 0.2K and 1K. Our results are compared with theoretical predictions for variable range hopping conduction. 相似文献
70.
Akira Nakayama Shinji Nambu Masahiro Inagaki Masahiko Miyauchi Nobuyuki Itoh 《Journal of the American Ceramic Society》1996,79(6):1453-1456
Complex permittivity of polycrystalline AlN was measured over the frequency range 100 MHz to 13 GHz using reflection coefficient and cavity resonator methods. Dielectric relaxation peaks of loss tangent were observed in the frequency range 200 MHz to 3 GHz. The maximum value of loss tangent was ∼200 × 10−4 . Relative permittivities decreased by ∼4% with increased frequency at the region of relaxation peaks. It was shown that these dispersion frequencies were inversely proportional to the grain sizes of AlN and independent of purities and processes. Model calculations for elastic vibration of a single-crystal grain of AlN were performed to investigate the origin of the dielectric dispersion due to piezoelectric effect. The calculated results of elastic sphere and 14-faced-polyhedron models showed a good quantitative agreement with the observed dispersion frequencies, which suggested that the dispersion was due to a piezoelectric vibration of a single grain of AlN ceramics at microwave frequencies. 相似文献