全文获取类型
收费全文 | 1434篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 69篇 |
综合类 | 1篇 |
化学工业 | 275篇 |
金属工艺 | 42篇 |
机械仪表 | 22篇 |
建筑科学 | 34篇 |
能源动力 | 43篇 |
轻工业 | 77篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 164篇 |
一般工业技术 | 258篇 |
冶金工业 | 328篇 |
原子能技术 | 35篇 |
自动化技术 | 101篇 |
出版年
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 13篇 |
2016年 | 16篇 |
2015年 | 12篇 |
2014年 | 31篇 |
2013年 | 42篇 |
2012年 | 33篇 |
2011年 | 42篇 |
2010年 | 43篇 |
2009年 | 52篇 |
2008年 | 61篇 |
2007年 | 44篇 |
2006年 | 37篇 |
2005年 | 35篇 |
2004年 | 37篇 |
2003年 | 35篇 |
2002年 | 39篇 |
2001年 | 38篇 |
2000年 | 23篇 |
1999年 | 22篇 |
1998年 | 124篇 |
1997年 | 83篇 |
1996年 | 89篇 |
1995年 | 47篇 |
1994年 | 41篇 |
1993年 | 39篇 |
1992年 | 21篇 |
1991年 | 24篇 |
1990年 | 27篇 |
1989年 | 23篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 4篇 |
1980年 | 22篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 12篇 |
1976年 | 14篇 |
1973年 | 7篇 |
1970年 | 4篇 |
排序方式: 共有1454条查询结果,搜索用时 11 毫秒
991.
T. Sekiguchi H. Yamane M. Aoki T. Aoki M. Shimada 《Science and Technology of Advanced Materials》2013,14(2):91-94
Luminescence properties of hexagonal (h-) and cubic (c-) GaN freestanding single crystals were studied by means of cathodoluminescence spectroscopy. The h-GaN crystals of about 0.2–2 mm in dimension were synthesized at 750 °C by the reaction of Ga and N2 in a Na flux, while c-GaN crystals of about 0.3 mm or less in a K flux. The h-GaN showed rather strong band edge emission at room temperature compared with the crystal grown by using NaN3 as a nitrogen source. At 20 K, the band edge emission of h-GaN was split into four peaks. The main energy peak position was 3.478 eV, which was assigned as the A-free exciton emission. The energy position of the main peak of c-GaN was 3.268 eV. Assuming the binding energies of excitons in h- and c-GaN as 25 and 26 meV, respectively, the energy difference of bandgap between h-and c-GaN is estimated to be 209 meV. Since these crystals are free from strain from the substrates, the peak energies are reliable for the intrinsic GaN crystals. The full widths at half maximum of the emission of c-GaN were much broader than those of h-GaN, suggesting that the cubic phase is much defective compared with the hexagonal one. 相似文献
992.
Glycation and phosphorylation of α-lactalbumin by dry heating: Effect on protein structure and physiological functions 总被引:2,自引:0,他引:2
α-Lactalbumin (α-LA) was glycated with maltopentaose (MP) through the Maillard reaction (MP-α-LA) and subsequently phosphorylated by dry heating in the presence of pyrophosphate to investigate its structure and physiological functions. Glycation occurred effectively, and the sugar content of α-LA increased by approximately 22.3% through the Maillard reaction. The phosphorylation of MP-α-LA was enhanced with an increase in the dry-heating time from 1 to 5 d, and the phosphorous content of MP-α-LA increased by approximately 1.01% by dry heating at pH 4.0 and 85°C for 5 d in the presence of pyrophosphate. The electrophoretic mobility of α-LA increased with an increase in the phosphorylation level. The circular dichroism spectra showed that the change in the secondary structure of the α-LA molecule by glycation and subsequent phosphorylation was slight. However, the Trp fluorescence intensity was increased by phosphorylation after glycation. In addition, the differential scanning calorimetry thermograms of α-LA showed that the denaturation temperature of MP-α-LA was decreased by phosphorylation. These results indicated that molten (partially unfolded) conformations of α-LA were formed by dry heating in the presence of pyrophosphate after glycation. The anti-α-LA antibody response was significantly reduced by glycation and subsequent phosphorylation. The suppressive effect of α-LA on the production of proinflammatory cytokines such as IL-6 and tumor necrosis factor-α from THP-1 cells after stimulation with lipopolysaccharide was significantly enhanced by glycation with MP and was further enhanced by phosphorylation after glycation. The Ca phosphate-solubilizing ability of α-LA was enhanced by phosphorylation. The apoptotic activity of α-LA was reduced by glycation and subsequent phosphorylation. These results suggest that phosphorylation by dry heating in the presence of pyrophosphate after glycation with MP through the Maillard reaction is a useful method for improvement of the physiological functions of α-LA. 相似文献
993.
Koichi Minagawa Kazuhiro Suga Masanori Kikuchi Shigeru Aoki 《International Journal of Mechanics and Materials in Design》2012,8(1):81-87
The present paper proposes an efficient inverse analysis to detect corrosion in concrete structures including multilayered
rebar using the observation accuracy as prior information. The proposed method can efficiently detect the corrosion profile,
including factors such as the number, shape, and location of multiple corroded areas from a potential distribution on a concrete
surface using the boundary element method and a genetic algorithm. The detectable are of rebar corrosion is estimated for
each rebar layer. The estimation can effectively limit a solution space to detect corrosion. Numerical simulations are performed
in order to demonstrate the validity and efficiency of the proposed method. 相似文献
994.
A major breakthrough in in vivo cellular imaging has been the clinical/preclinical use of magnetic resonance imaging (MRI) with contrast agent. Superparamagnetic iron oxide (SPIO) is a promising candidate for the development of smart MRI probes for cell-tracking. In the present study, we describe biodegradable probes made of giant vesicles (GVs; closed lipid membranes with diameters >1 μm) that encapsulate SPIO for use as an MRI contrast agent. These SPIO-containing GVs (SPIO-GVs) exhibited excellent contrast enhancement in the single cell of medaka fish (Oryzias latipes) embryos immediately after their microinjection, and this enhancement disappeared when the GV membranes were destroyed. Our results demonstrate that SPIO-GVs are useful MRI probes for single cell-tracking that have minimum cytotoxicity and will greatly improve clinical/preclinical in vivo cellular imaging techniques. 相似文献
995.
Saburi Masahisa Niki Kazuhisa Kobayashi Suguru Aiakwa Sadao 《IEEE transactions on bio-medical engineering》1983,(6):341-346
A multimicroelectrode system is described in which the microelectrodes are individually magnetized and coupled to one another by the magnetic force acting on each microelectrode. This arrangement increases the mechanical strength of the fine microelectrodes, and also restricts the bending of each microelectrode wire. This Multimicroelectrode structure allows independent and parallel penetration of many fine microelectrodes within local neural tissue areas. 相似文献
996.
H. Shinozaki T. Oguchi S. Suzuki K. Aoki T. Sako S. Morishita 《Drug development and industrial pharmacy》2013,39(7):877-891
ABSTRACTRapid expansion of supercritical solutions (RESS) was applied to tolbutamide and barbital. The solubility in supercritical CO2 was determined to estimate the extraction efficiency roughly by a simple method and accurately by a direct spectrophotometric technique. The latter revealed that the solubility of tolbutamide was a function of applied pressure and temperature and was proportional to the pressure. No significant difference in solubility between polymorphic Forms I and II of tolbutamide was detected. Tolbutamide and barbital particles produced by the RESS were characterized by size distribution measurement, polymorph identification and morphological evaluation. Significant size reduction to micron or sub-micron level with narrow size distribution was achieved, while conventional mechanical grinding had only slight effect. The particle size was greatly affected by both extraction and expansion conditions. The lower the extraction temperature was, the smaller was the mean particle size. Higher extraction pressure resulted in smaller mean particle size when compared at the same extraction temperature. The mean particle size was reduced by lowering the spray nozzle temperature, by lowering the expansion chamber temperature, by increasing the CO2 amount per spray, and by increasing the exhaust gas flow rate. The RESS processing realized the polymorphic conversion as well. As for tolbutamide, three polymorphs (Forms I, II, and IV) out of four could be produced by changing the extraction conditions, and in the case of barbital, one polymorph (Form II) out of three was produced consistently. 相似文献
997.
Laser emission and amplification have been studied in the 1.3 mu m spectral region on the /sup 4/F/sub 3/2/-/sup 4/I/sub 13/2/ transition in Nd/sup 3+/-doped fluorophosphate singlemode fibres. Pumping at 800 nm yields an extracted laser power of 10 mW at 1.323 mu m. A gain higher than 3 dB was obtained at the same wavelength in the amplifier experiment.<> 相似文献
998.
Urita K Seki S Utsumi S Noguchi D Kanoh H Tanaka H Hattori Y Ochiai Y Aoki N Yudasaka M Iijima S Kaneko K 《Nano letters》2006,6(7):1325-1328
We present significant electrical conductivity responses of the pelletized as-prepared and oxidized (ox-) single-wall carbon nanohorns (SWNHs) on adsorption of CO(2) and O(2). The morphological and pore structures of both pelletized SWNHs were examined by transmission electron microscopy (TEM) and nitrogen adsorption isotherm, leading to explicit evidences of the formation of nanoscale windows on the wall by oxidation. The SWNH and ox-SWNH induced a semiconducting behavior, strongly responded to CO(2) and O(2) adsorptions, and each exhibited n-type- and p-type-like conductivities. The electrical conductivity increase and decrease for CO(2) and O(2) adsorption, respectively, were observed for SWNH, whereas ox-SWNH showed a marked electrical conductivity drop on CO(2) adsorption and almost no change on O(2) adsorption. The dramatically different electrical conductivity response of ox-SWNH is presumed to be ascribed to the annihilation of pentagons in the single graphene wall by oxidation. 相似文献
999.
Hidenao Sugawara Shigeru Sato Tsuneaki Miyahara Akito Kakizaki Yumio Morioka Yasuo Iguchi Ichiro Nagakura Masami Ando Toshiaki Ohta Sadao Aoki 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,228(2-3):549-555
Reflectance spectra have been measured for many materials in the wavelength range from 90 Å to 400 Å. The angle of incidence ranged from 20° to 85°. The samples were chemical-vapor-deposited silicon carbide (CVD-SiC), a single crystal of silicon with (100) surface, fused quartz, zerodur, pyrex, gold, platinum, copper and two kinds of steel. To obtain reflectances for surfaces for practical use, measurements were made on surfaces sufficiently exposed to air. Reflectances for s-polarized light (Rs) were measured for all samples. On CVD-SiC, gold and platinum, reflectances for p-polarized light (RP) were also observed. At short wavelengths and large angles of incidence, the difference between Rs and RP is small, and RP happened to exceed Rs in contrast to the result from the Fresnel equation. This may be due to the deviation of the present surfaces of mirrors from an ideal plane. Reflectance spectra of surfaces prepared by some feasible techniques are also presented. 相似文献
1000.
Y Nimura S Yokoyama M Fujimori T Aoki W Adachi T Nasu M He YM Ping F Iida 《Canadian Metallurgical Quarterly》1997,80(5):852-857
OBJECTIVES: Patients with cirrhosis and ascites have high plasma levels of atrial natriuretic peptide (ANP). Pharmacological doses of this hormone usually worsen systemic hemodynamics of cirrhotic patients. We assessed whether ANP influences cardiovascular homeostasis and renal function in patients with compensated cirrhosis at plasma levels comparable to those observed in patients with cirrhosis and ascites. METHODS: Radionuclide angiocardiography was performed in eight compensated cirrhotic patients during placebo (three periods of 15 min each) and ANP infusion (2, 4, and 6 pmol/kg.min for 15 min each), together with appropriate blood and urine sampling, to evaluate left ventricular diastolic, systolic, and stroke volume, heart rate, cardiac output, arterial pressure, peripheral vascular resistance, creatinine clearance, urinary sodium excretion, plasma renin activity, plasma aldosterone, norepinephrine and hematocrit. RESULTS: The infusion increased plasma ANP up to levels (52.03 +/- 2.29 pmol/L) comparable with those observed in 35 patients with ascites (46.42 +/- 1.57 pmol/ L). This increment was associated with significant reductions in left ventricular end diastolic volume, stroke volume, cardiac index (from 3.7 +/- 0.7 to 3.1 +/- 0.5 L/min.m2, p < 0.05) and mean arterial pressure (from 96.7 +/- 6.5 to 88.5 +/- 9.5 mmHg, p < 0.05), while heart rate and hematocrit significantly increased. Peripheral vascular resistance did not change. These hemodynamic effects occurred despite significant increases in plasma renin activity and norepinephrine. ANP also induced increases in creatinine clearance, urinary sodium excretion, and fractional sodium excretion. CONCLUSIONS: Low-dose ANP affected cardiovascular homeostasis and renal sodium handling in compensated cirrhosis, suggesting that this hormone may be involved in the pathophysiology of systemic hemodynamic and renal functional abnormalities of cirrhosis. 相似文献