全文获取类型
收费全文 | 1820篇 |
免费 | 33篇 |
专业分类
电工技术 | 9篇 |
综合类 | 2篇 |
化学工业 | 158篇 |
金属工艺 | 7篇 |
机械仪表 | 17篇 |
建筑科学 | 30篇 |
矿业工程 | 2篇 |
能源动力 | 14篇 |
轻工业 | 81篇 |
水利工程 | 2篇 |
无线电 | 179篇 |
一般工业技术 | 140篇 |
冶金工业 | 1103篇 |
原子能技术 | 18篇 |
自动化技术 | 91篇 |
出版年
2022年 | 8篇 |
2021年 | 15篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 15篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 24篇 |
2012年 | 35篇 |
2011年 | 37篇 |
2010年 | 28篇 |
2009年 | 31篇 |
2008年 | 26篇 |
2007年 | 29篇 |
2006年 | 25篇 |
2005年 | 28篇 |
2004年 | 27篇 |
2003年 | 18篇 |
2002年 | 22篇 |
2001年 | 18篇 |
2000年 | 18篇 |
1999年 | 51篇 |
1998年 | 297篇 |
1997年 | 179篇 |
1996年 | 124篇 |
1995年 | 87篇 |
1994年 | 72篇 |
1993年 | 81篇 |
1992年 | 27篇 |
1991年 | 25篇 |
1990年 | 31篇 |
1989年 | 30篇 |
1988年 | 26篇 |
1987年 | 28篇 |
1986年 | 15篇 |
1985年 | 28篇 |
1984年 | 6篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 24篇 |
1980年 | 20篇 |
1979年 | 11篇 |
1978年 | 17篇 |
1977年 | 29篇 |
1976年 | 78篇 |
1975年 | 13篇 |
1973年 | 7篇 |
1971年 | 7篇 |
排序方式: 共有1853条查询结果,搜索用时 15 毫秒
81.
82.
F Picó Aracil J Garcia Garcia E Jaén Armand JV Campos Peris JA Ruiz Ros J Salas Nieto P Rodriguez Ruiz JA Ruipérez Abizanda 《Canadian Metallurgical Quarterly》1980,75(5):203-206
In eleven patients with isolated mitral stenosis and regular sinus rhythm a right cardiac catheterization was performed and the wedged pulmonary capillary pressure recorded at rest and during electrical pacing of the right atrium at successive frequencies of 100, 120, 140, and, occasionally, 160 and 180 beats/min, while cardiac output was estimated by the Fick's principle. In all cases a significant elevation of pulmonary capillary pressure with a simultaneous reduction in cardiac output was obtained. The rise of wedged pulmonary pressure was proportional to the increment in cardiac frequency and related also to the calculated area of the mitral valve. The influence of active atrial contraction upon pulmonary pressure and cardiac output is discussed and comparisons with other studies are made. Emphasis is made on the value of atrial pacing as a diagnostic method in mitral stenosis, especially in cases in whom classical effort manoeuvres can not be applied or are insufficient to rise cardiac frequency. 相似文献
83.
Voltammetric data are reported for a series of fluoroaromatic hydrocarbons in fluorosulphonic acid containing a base, acetic acid (0·1 M). In this medium and at room temperature, all but one of the compounds show an initial one electron oxidation to form a cation radical which is stable on the timescale of cyclic voltammetry; with the exception of the cation radical of octafluoronapthalene, none are stable indefinitely and approximate half lives are reported.Experiments at low temperatures or in solutions in this solvent where the supporting electrolyte is the acid, antimony pentafluoride, show that conditions may be defined where the cation radicals are stable indefinitely.Some preliminary preparative results are reported and these show that fluorosulphonate esters may be prepared. 相似文献
84.
J. R. Coleman 《Journal of Applied Electrochemistry》1971,1(1):65-71
The preparation of lead chloride cathodes, and their discharge in magnesium-lead chloride batteries, is described. The lead chloride blended with graphite is pasted on grids of expanded copper, using urea formaldehyde solutions as the binder. One-, five-, and fifteen-cell batteries were discharged at temperatures between –40°C and +45°C, at low current drains. For five-cell batteries energy densities in the range 10–30 Wh/lb were obtained. Mechanical properties of the cathode, so far as investigated, were excellent. The main difficulty was cathode softening during prolonged runs at high temperatures. At –40°C the battery attained working voltage in about 5 minutes; although slower than the Mg-AgCl system, the Mg-PbCl2 system should meet many applications at this temperature. 相似文献
85.
86.
Infra-red and Raman spectra of poly (1,1,2,2-tetrachlorobutane), a model polymer for head-to-head poly(vinylidene chloride), are presented. Mutual exclusion of the infra-red and Raman spectra is observed and the polymer appears to be highly ordered. The preferred conformation of the polymer chain is inferred to be most probably in the form of a planar zigzag. 相似文献
87.
88.
An electromyographic study of nonmimetic skeletal muscles was carried out in 8 normal adults and 4 patients with spastic hemiparesis during all stages of sleep for a total of 21 nights. All normal subjects showed absence of tonic electromyographic activity in all nonmimetic skeletal muscles in all stages of sleep. Also, during quiet, relaxed wakefulness, tonic muscle discharges disappeared in the normal subjects. Three patients with upper motor neuron spasticity demonstrated results during sleep similar to those obtained in the normal subjects. In the fourth patient, tonic muscle discharges persisted into stage 2 non-REM sleep, disappeared within 30 to 240 seconds following the onset of stage 2 sleep, and were absent during stages 3 and 4 sleep and REM sleep. 相似文献
89.
Thyroid carcinoma after high-dose external radiotherapy for Hodgkin's disease: report of three cases
IR McDougall CN Coleman JS Burke W Saunders HS Kaplan 《Canadian Metallurgical Quarterly》1980,45(8):2056-2060
Three patients (two female and one male), who had received mantle irradiation for Hodgkin's disease eight, ten, and twelve years previously, developed papillary thyroid carcinoma. The radiation doses to the necks overlying the site of thyroid cancers were 3000, 4000, and 4100 rads, respectively. It has been stated that there is no risk of developing thyroid cancer with such high doses of external irradiation but apparently this complication will be encountered in a small number of patients. 相似文献
90.
Coleman SJ Coronado PR Maxwell RS Reynolds JG 《Environmental science & technology》2003,37(10):2286-2290
Aqueous solutions of 100 parts per billion (ppb) uranium at pH 7 were treated with granulated activated carbon (GAC) that had been modified with various formulations of hydrophobic aerogels. The composite materials were found to be superior in removing uranium from a stock solution compared to GAC alone evaluated by a modified ASTM D 3860-98 method for batch testing. The testing results were evaluated using a Freundlich adsorption model. The best performing material has parameters of n = 287 and Kf = 1169 compared to n = 1.00, and Kf = 20 for GAC alone. The composite materials were formed by mixing (CH3O)4Si with the hydrophobic sol-gel precursor, (CH3O)3SiCH2CH2CF3 and with specified modifiers, such as H3PO4, Ca(NO3)2, and (C2H5O)3SiCH2CH2P(O)(OC2H5)2, elation catalysts, and GAC in a supercritical reactor system. After gelation, supercritical extraction, and sieving, the composites were tested. Characterization by FTIR and 31P NMR indicate the formation of phosphate in the case of the H3PO4 and Ca(NO3)2 composites and phosphonic acid related compounds in the phosphonate composite. These composite materials have potential application in the clean up of groundwater at DOE and other facilities. 相似文献