首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   38篇
  免费   0篇
化学工业   5篇
机械仪表   1篇
建筑科学   3篇
能源动力   1篇
轻工业   1篇
无线电   7篇
一般工业技术   3篇
冶金工业   15篇
原子能技术   2篇
  2022年   3篇
  2021年   1篇
  2013年   1篇
  2012年   1篇
  2011年   2篇
  2010年   1篇
  2009年   1篇
  2004年   2篇
  2003年   1篇
  1999年   1篇
  1998年   1篇
  1997年   4篇
  1996年   5篇
  1995年   5篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1980年   1篇
  1977年   2篇
  1974年   1篇
排序方式: 共有38条查询结果,搜索用时 0 毫秒
11.
The idea of space solar power proposed by Glaser was explained as a set of a solar power power station in geostationary earth orbit to transmit microwave power and a ground station to receive the microwave power. Most of the ideas and concepts since Glaser used the same context. On the other hand, Collins et al. (Proceedings SPS '91, pp. 132–141, 1991) introduced the concept of microwave “fuel” to assess the commercial relations of power from space, in which space solar power stations are considered to sell microwave power to any unspecified rectenna. This concept changed the theoretical context of “power from space” to an industrial and economic relation of producers and buyers of an industrial product. This new context has been applied to the SPS 2000 conceptual study. As a result, if 2.45 GHz microwave power transmission is used, each rectenna can be planned and engineered independently from the space sector by local users, especially in developing countries, who are familiar with such activities as introducing solar energy systems.  相似文献   
12.
The number of NADPH diaphorase-positive cells in the CA1/CA2 and CA3 regions of Ammon's horn and the subiculum of the hippocampal formation of EL mice, an inbred mutant strain of the ddY mouse susceptible to convulsive seizures, was fewer than that of ddY mice. These findings suggest that smaller numbers of nitric oxide producing cells in the hippocampal formations of EL mice is related to their susceptibility to convulsive seizures.  相似文献   
13.
In airtight houses, it is important to control the ventilation airflow of each room in order to ensure good indoor air quality. Therefore, the mechanical ventilation equipment should be designed carefully, giving due consideration to the ventilation efficiency in rooms. This paper describes the ventilation efficiency of a three-zone scale model with the experiment. The step-down method is applied to clarify the age of air and other indexes of ventilation efficiency. The effects of ventilation airflow volume with no recirculation and of the recirculated airflow volume on ventilation efficiency are investigated.  相似文献   
14.
Degradation of poly(methyl methacrylate) (PMMA) caused by irradiation of flash light from discharged xenon lamp was investigated in a vacuum and in the presence of nitrogen. Degradation products at a sequence of flashes were analysed by a gas chromatograph with hydrogen flame ionization detector after each flash. Among the degradation products of PMMA in vacuum by regular flash light, an amount of monomer was detected with the significant production of methanol and gaseous mixture. The molecular weight of the residual polymer decreased markedly by the first several flashes, showing that chain scission occurred. By filtering the u.v. component of flash light the monomer formation and molecular weight decrease were not observed. From these facts the flash degradation of PMMA in vacuum was concluded to be conducted by a photodegradation mechanism. The absorption of u.v. light by ester groups forms active radicals, which initiate chain scissions and depolymerization of main chains following methanol and monomer formation. At the flash degradation in nitrogen at atmospheric pressure PMMA degraded in the different manner. At the initial several flashes the photodegradation mechanism is also conducted in the polymer matrix and decomposed secondarily at the subsequent flashes to form a significant amount of carbon particles. Thereafter, carbon particles acted as a photoabsorber, and the thermal degradation of the polymer occurred predominantly around the heated carbon particles.  相似文献   
15.
The molecular weights of poly(N‐vinylformamide) [poly(NVF)] obtained by free‐radical polymerization were expanded from being in the range of thousands to hundreds of thousands. Primary amino groups were introduced by the hydrolysis of poly(NVF) under both acidic and basic conditions. After 2 h polyvinylamine [poly(VAm)] was given at 60°C under a 2N NaOH solution. The apparent activation energy of poly(NVF) hydrolysis was 61.8 kJ/mol. Furthermore, alkyl side chains were partly introduced by a polymer modification reaction in poly(VAm) with carboxylic acid, using WSC (water‐soluble carbodiimide) as the activating agent to produce the stimuli‐responsive poly(VAm) derivative. The effects of external stimuli such as temperature and pH on the phase‐transition behavior of the copolymers were then studied. The lower critical solution temperature at pH 12 decreased depending on the alkyl group content. The phase‐transition behavior of the resulting polymers was also found to vary depending on the side‐chain length of the alkyl groups. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1277–1283, 2003  相似文献   
16.
Continuous beds have been used as matrices for cation- and anion-exchange chromatography of proteins on columns with an i.d. in the range of 0.005-0.015 mm. On-tube uv detection is not feasible at low protein concentrations with these narrow-bore columns. Therefore, a more sensitive detection system has been developed based on blotting technique: as the protein zones leave the microcolumn chromatographically they become adsorbed onto a rotating polyvinylidene difluoride blotting membrane. The protein spots can then be visualized by means of Coomassie brilliant blue, immunomethods, and other standard techniques. By using an immunomethod 0.015 ng of human transferrin can easily be detected. The blotting membrane can be washed with water without loss of adsorbed protein. This is an attractive feature because the presence of salts, etc., diminishes the accuracy in the determination of molecular weights of proteins by mass spectrometry. The microcolumns are easy to prepare. A solution of appropriate monomers is sucked into a piece of fused silica tubing. The rod formed upon polymerization contains channels through which the eluent can pass. No supporting frit is required because the polymer rod is anchored by covalent bonds to the tubing wall.  相似文献   
17.
Bopindolol and its two metabolites (18-502 and 20-785) were examined for their affinity to a beta 2-adrenoceptor in the bovine mesenteric artery using the radioligand binding assay method with [3H]CGP12177 as a radioligand. The Scatchard analysis of the data demonstrated a uniphasic plot with Kd and Bmax values of 0.86 +/- 0.16 nM, and 13.34 +/- 1.11 fmol/mg protein, respectively. The pKi values of bopindolol and its two metabolites for beta 2-adrenoceptors in the bovine mesenteric artery were 7.70 +/- 0.13, 8.07 +/- 0.13, 8.20 +/- 0.24, respectively, with 20-785 showing the highest values among these drugs. The present findings indicate that the bovine mesenteric artery membrane is predominantly beta 2-adrenoceptor tissue, and that bopindolol and its two metabolites were potent for beta 2-adrenoceptors in the bovine mesenteric artery.  相似文献   
18.
D-Ala and D-Ser were detected in the sera of both normal subjects and patients with renal dysfunction, and their concentrations were higher in the patients than in the normal subjects. A positive correlation between the concentration of D-Ala or D-Ser and that of creatinine (r = 0.733, p < 0.001 or r = 0.634, p < 0.001) or blood urea nitrogen (BUN) (r = 0.449, p < 0.05 or r = 0.629, p < 0.001) was observed in sera from 20 patients with renal dysfunction. The fraction (%D) of D-Ala in the total Ala in serum ([D/(D+L)] x 100) correlated well with the concentration of creatinine (r = 0.811, p < 0.001), suggesting that it is a candidate as a marker for renal proximal tubular dysfunction. The correlations of %D of Ser with creatinine and BUN levels were 0.796 (p < 0.001) and 0.919 (p < 0.001), respectively, indicating that %D of Ser may reflect protein turnover or catabolism in certain tissues as well as renal proximal tubular dysfunction.  相似文献   
19.
We report a 55-year-old woman who developed symptoms resembling parkinsonism. Her psychiatric symptoms in the early stage, cervical dystonia and tremor increasing on movement were consistent with manganese poisoning. Manganese levels were elevated to 1.5 micrograms/l in the serum (normal; 0.3-1.1 micrograms/l) and to 1.4 micrograms/l in the urine (normal; less than 1.2 micrograms/l). Intravenous infusion of calcium disodium editate (CaEDTA; chelating agent) was followed by the marked excretion of manganese (27.3 micrograms/l) in the urine. These findings support manganese poisoning. Manganese poisoning is a disease which results from chronic exposure to manganese, but the source of manganese exposure remained obscure in this patient. T1-weighted MRI of the brain showed symmetric high signal intensity in the globus pallidus without any abnormality on T2-weighted images. There is a report that manganese induced brain lesions in Macaca fascicularis as revealed by MRI and the fascicularis developed signs of unsteady gait and hypoactivity. The patient responded to treatment with CaEDTA and the second MRI demonstrated regression of abnormal signal intensity. This may be due to enhanced manganese excretion. To our knowledge, this is the first case of probable manganese-induced human parkinsonism whom changes in MRI were noted after treatment with CaEDTA.  相似文献   
20.
Recent studies noted the contribution of alpha42Tyr to the T-R-dependent UV resonance Raman (UVRR) spectral changes of HbA [Nagai, M., et al. (1996) J. Mol. Struct. 379, 65-75; Huang, S., et al. (1997) Biochemistry 36, 6197-6206], but the observed UVRR changes of the Tyr residue cannot be fully interpreted with alpha42Tyr alone. To identify the remaining contributions, the 235 nm-excited UVRR spectra of Tyr mutant Hbs at alpha140, beta35, and beta145 were investigated here. The Fe-His stretching mode demonstrated that all of these mutant Hbs take the T structure in the deoxy form under these experimental conditions. The UVRR change of the Trp residue of these mutants upon the T-R transition was the same as that in HbA, indicating that the T-R-dependent UVRR change of beta37Trp is not due to stacking with Tyr residues but is due to the formation or destruction of a hydrogen bond. The recombinant Hbs beta35Tyr --> Phe and beta35Tyr --> Thr both exhibited UVRR spectra identical with that of HbA, meaning that beta35Tyr is not responsible. In the spectra of des(beta146His,beta145Tyr)Hb with inositol hexaphosphate, the frequency shift of the Tyr RR bands was the same as that in HbA but the intensity enhancement in the CO form was small, suggesting that beta145Tyr contributes to a part of the intensity change, but scarcely relates to the frequency shift. In the spectra of Hb Rouen (alpha140Tyr --> His), the frequency shifts of bands at 1617 (Y8a) and 1177 (Y9a) cm-1 following ligation were half of those in HbA, while the intensity enhancement was not detected. This result means that alpha140Tyr is responsible for both the frequency shift and the intensity changes. It is suggested that the frequency shift of the Tyr RR bands upon the T --> R transition is due to changes in the hydrogen bonding state of alpha42- and alpha140Tyr and that the intensity enhancement is due to changes in the environment of the penultimate Tyr in both alpha and beta subunits (alpha140 and beta145). These alterations in the vibrational spectra clearly demonstrate which tyrosine residues are involved in the T-R transition as a result of modification of their local environments.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号