全文获取类型
收费全文 | 576篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 67篇 |
化学工业 | 123篇 |
金属工艺 | 14篇 |
机械仪表 | 15篇 |
建筑科学 | 14篇 |
能源动力 | 30篇 |
轻工业 | 26篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 66篇 |
一般工业技术 | 101篇 |
冶金工业 | 68篇 |
原子能技术 | 23篇 |
自动化技术 | 50篇 |
出版年
2023年 | 10篇 |
2022年 | 4篇 |
2021年 | 15篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 27篇 |
2017年 | 11篇 |
2016年 | 16篇 |
2015年 | 9篇 |
2014年 | 18篇 |
2013年 | 42篇 |
2012年 | 25篇 |
2011年 | 42篇 |
2010年 | 29篇 |
2009年 | 30篇 |
2008年 | 33篇 |
2007年 | 19篇 |
2006年 | 21篇 |
2005年 | 12篇 |
2004年 | 4篇 |
2003年 | 14篇 |
2002年 | 18篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 13篇 |
1998年 | 29篇 |
1997年 | 23篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 9篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1972年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有601条查询结果,搜索用时 62 毫秒
51.
A mechanically induced current (MIC) in a polypyrrole/Au-coated membrane (PPy/Au-membrane) composite with various surface morphologies was investigated, and the electrolyte conditions were determined in an electrochemical cell. A MIC was induced on porous PPy/Au-membranes with a thin layer of PPy. Conversely, relatively small MICs were observed in non-highly porous films such as freestanding films and PPy/Au-membranes with thick PPy deposits. A MIC smaller by one order of magnitude was also observed in a Au-membrane without PPy. These results indicated that the MICs was due to a charging phenomenon in both the redox and the double layer capacitances. The MIC also varied with supporting electrolyte and their concentration. The MIC was strongly reduced in solutions with diluted electrolytes and with bulky cationic electrolytes, indicating that the number and the penetration speed of mobile ions limited the magnitude of the MIC. These characteristics indicated that the MIC was essentially a diffusion limited current. A two-electrode MIC cell was also configured to investigate a power generation film in a normal saline solution, which can possibly be utilized for biomedical applications. 相似文献
52.
Three diamensional (3D) measurement method by Scanning Electron Microscope (SEM) has already been proposed by using the principle
of shadow moiré. In the method, the image of original grid in shadow moiré image must be clearly removed in fringe analysis
process in order to perform high resolution analysis. A new method based on the principle of projection moiré is proposed
to solve the trouble concerning the grid. In this paper, the mechanism of producing some shadows of grid on the surface of
the object by back scattering electron beam in the new method is discussed. Fringe image as shadow of grid is analyzed by
Wavelet transform. The precise 3D measurement is realized by using the phenomenon of shadows of grid. Furthermore, a 3D micro
structure on the head of a hard disk is measured. From the comparison of results obtained by Atomic Force Microscope (AFM),
it is confirmed that the proposed method has high-resolution power(about 20nm). 相似文献
53.
Hisato Tokoro Shigeo FujiiYasuhiro Kobayashi Shunsuke Muto 《Journal of Alloys and Compounds》2011,509(5):1378-1383
Magnetic fine particles of metallic Fe coated with graphitic carbon layers were synthesized by annealing Fe2O3 particles with carbon powders at 1673 K in nitrogen atmosphere. For comparison, SiC was added to Fe2O3. X-ray diffraction measurement showed that the lattice constants of Fe changed depending on the Si contents. Mössbauer spectroscopy confirmed that Fe-Si alloys were formed by the Si addition and that the iron carbide disappeared. Electron microscope images revealed that the thickness of carbon coating layers increased from 24 nm to 36 nm as a result of the Si addition. Soaking tests showed that the corrosion resistance of the carbon-coated Fe particles was improved by the addition of Si. The results suggest that Si caused C to leave the Fe cores and move to the surface to form a carbon coating. 相似文献
54.
55.
H Miwa T Murai R Ohkura M Kawabe H Tanaka T Ogihara S Watanabe N Sato 《Canadian Metallurgical Quarterly》1997,2(2):82-85
HIV-associated salivary gland disease (HIV-SGD) includes lymphoepithelial lesions and cysts involving the salivary gland tissue and/or intraglandular lymph nodes, and Sj?gren-like conditions. Three cases of salivary gland disease occurring in HIV-infected patients are reported. Histopathological examination showed squamous epithelium-lined cysts. In the walls of the cysts lymphoid tissue, epitheloid granulomas and giant cells were found. The clinical and histopathological criteria as well as magnetic resonance imaging and therapy are discussed. 相似文献
56.
Common beans are widely utilized as a food source, yet are low in the essential amino acid methionine. As an initial step to overcome this defect the methionine content of the primary bean seed storage protein phaseolin was increased by replacing 20 evolutionarily variant hydrophobic residues with methionine and inserting short, methionine-rich sequences into turn and loop regions of the protein structure. Methionine enhancement ranged from 5 to 30 residues. An Escherichia coli expression system was developed to characterize the structural stability of the mutant proteins. Proteins of expected sizes were obtained for all constructs except for negative controls, which were rapidly degraded in E. coli. Thermal denaturation of the purified proteins demonstrated that both wild-type and mutant phaseolin proteins denatured reversibly at approximately 61 degrees C. In addition, urea denaturation experiments of the wild-type and a mutant protein (with 30 additional methionines) confirmed that the structural stability of the proteins was very similar. Remarkably, these results indicate that the phaseolin protein tolerates extensive modifications, including 20 substitutions and two loop inserts for methionine enhancement in the beta-barrel and loop structures, with extremely small effects on protein stability. 相似文献
57.
K. Hara T. Sato R. Katoh A. Furube T. Yoshihara M. Murai M. Kurashige S. Ito A. Shinpo S. Suga H. Arakawa 《Advanced functional materials》2005,15(2):246-252
Novel conjugated organic dyes that have N,N‐dimethylaniline (DMA) moieties as the electron donor and a cyanoacetic acid (CAA) moiety as the electron acceptor were developed for use in dye‐sensitized nanocrystalline‐TiO2 solar cells (DSSCs). We attained a maximum solar‐energy‐to‐electricity conversion efficiency (η) of 6.8 % under AM 1.5 irradiation (100 mW cm–2) with a DSSC based on 2‐cyano‐7,7‐bis(4‐dimethylamino‐phenyl)hepta‐2,4,6‐trienoic acid (NKX‐2569): short‐circuit photocurrent density (Jsc) = 12.9 mA cm–2, open‐circuit voltage (Voc) = 0.71 V, and fill factor (ff) = 0.74. The high performance of the solar cells indicated that highly efficient electron injection from the excited dyes to the conduction band of TiO2 occurred. The experimental and calculated Fourier‐transform infrared (FT‐IR) absorption spectra clearly showed that these dyes were adsorbed on the TiO2 surface with the carboxylate coordination form. A molecular‐orbital calculation indicated that the electron distribution moved from the DMA moiety to the CAA moiety by photoexcitation of the dye. 相似文献
58.
A 63-year-woman who complained of sensorimotor disturbance of the lower extremities and urinary disturbance was presented. She noted loss of superficial sensation in both feet and foot ulcers at the age of 20 years. Her illness was initially diagnosed as hereditary sensory neuropathy type 1 (HSN1). The foot ulcers were so intractable that she had to have her right leg amputated at the age of 48 years. She had a severely impaired superficial sensation in the lower extremities and buttock, distal weakness of the left leg, and dysuria at the age of 60 years. The neurological examination revealed that she had segmental sensorimotor disturbance below the levels of the 5th lumbar segment. MRI demonstrated tethered cord with a lumbosacral lipoma. Adult onset tethered cord syndrome (TCS) that presents with HSN 1-like symptoms as initial clinical features has not yet been reported. Foot ulcers are often seen in child onset TCS in which the degree of tethered cord is severer than adult onset cases. It is reported that release of the tethered cord promotes healing of the foot ulcers. We recommend MRI for the study of the lumbosacral cord of patients with HSN 1-like symptoms, because there is a possibility that such patients may have TCS and early surgical treatment is effective for TCS. 相似文献
59.
S Takashima T Saeki I Adachi T Watanabe Y Sasaki H Murai T Tabei M Ogita M Sano K Kanda M Shimoyama 《Canadian Metallurgical Quarterly》1997,27(5):325-330
In a previous study, we found that oral chromium nicotinate overcame sucrose-induced hypertension in spontaneously hypertensive rats (SHR). Accordingly, we examined more chromium compounds to determine if others were more or less effective in regulating blood pressure (BP) of SHR. Since chromium is postulated to be an antioxidant, we also assessed the ability of different chromium compounds to alter free radical formation measured by determining thiobarbituric acid reactive substances (TBARS). The control group of SHR ingested a diet low in chromium, and 5 other groups ate the same diet with various chromium compounds added at 5 ppm-chloride, acetate, nicotinic acid-glycine-cysteine-glutamic acid (NA-AA), picolinate, and nicotinate. Following this, the rats were challenged with drinking water containing 5% and 10% w/v sucrose. Except for NA-AA, all chromium compounds inhibited the sucrose-induced elevation of systolic BP; and acetate, picolinate, and nicotinate chromium compounds lowered HbAIC below control. Only chromium acetate and nicotinate significantly lowered both hepatic and renal TBARS. Chromium picolinate lowered hepatic TBARS, and chromium chloride and NA-AA lowered neither. We conclude that chromium, rather than a specific ligand, plays a major role in ameliorating sucrose-induced BP elevations and can act as an antioxidant. 相似文献
60.
Nishino T. Hatano M. Hasegawa H. Murai F. Kure T. Hiraiwa A. Yagi K. Kawabe U. 《Electron Device Letters, IEEE》1989,10(2):61-63
A superconducting field-effect transistors (FET) with a 0.1-μm-length gate electrode was fabricated and tested at liquid-helium temperature. Two superconducting electrodes (source and drain) were formed on the same Si substrate surface with an oxide-insulated gate electrode by a self-aligned fabrication process. Superconducting current flowing through the semiconductor (Si) between the two superconducting electrodes (Nb) was controlled by a gate-bias voltage 相似文献