全文获取类型
收费全文 | 13123篇 |
免费 | 136篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 116篇 |
综合类 | 4篇 |
化学工业 | 1008篇 |
金属工艺 | 100篇 |
机械仪表 | 145篇 |
建筑科学 | 264篇 |
矿业工程 | 18篇 |
能源动力 | 123篇 |
轻工业 | 502篇 |
水利工程 | 56篇 |
石油天然气 | 7篇 |
武器工业 | 1篇 |
无线电 | 696篇 |
一般工业技术 | 952篇 |
冶金工业 | 8535篇 |
原子能技术 | 70篇 |
自动化技术 | 677篇 |
出版年
2022年 | 37篇 |
2021年 | 43篇 |
2019年 | 41篇 |
2018年 | 79篇 |
2017年 | 59篇 |
2016年 | 68篇 |
2015年 | 73篇 |
2014年 | 101篇 |
2013年 | 261篇 |
2012年 | 161篇 |
2011年 | 198篇 |
2010年 | 146篇 |
2009年 | 157篇 |
2008年 | 201篇 |
2007年 | 205篇 |
2006年 | 202篇 |
2005年 | 196篇 |
2004年 | 181篇 |
2003年 | 166篇 |
2002年 | 147篇 |
2001年 | 145篇 |
2000年 | 152篇 |
1999年 | 349篇 |
1998年 | 2648篇 |
1997年 | 1502篇 |
1996年 | 1019篇 |
1995年 | 581篇 |
1994年 | 483篇 |
1993年 | 547篇 |
1992年 | 171篇 |
1991年 | 153篇 |
1990年 | 157篇 |
1989年 | 152篇 |
1988年 | 145篇 |
1987年 | 146篇 |
1986年 | 143篇 |
1985年 | 165篇 |
1984年 | 106篇 |
1983年 | 88篇 |
1982年 | 106篇 |
1981年 | 121篇 |
1980年 | 127篇 |
1979年 | 73篇 |
1978年 | 84篇 |
1977年 | 224篇 |
1976年 | 441篇 |
1975年 | 53篇 |
1974年 | 43篇 |
1973年 | 53篇 |
1972年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
AE Speckens AM Van Hemert JH Bolk HG Rooijmans MW Hengeveld 《Canadian Metallurgical Quarterly》1996,26(4):745-752
BACKGROUND: Measurement of intracardiac hemodynamic parameters has been limited to brief periods in the acute care setting. We developed and evaluated an implantable hemodynamic monitor that is capable of measuring chronic right ventricular oxygen saturation and pulmonary artery pressure. METHODS AND RESULTS: The device consists of an electronic controller placed subcutaneously and two transvenous leads placed in the right ventricle (reflectance oximeter) and pulmonary artery (variable capacitance pressure sensor). Implantation was performed in 10 patients with severe left ventricular dysfunction. Average implant pulmonary artery pressures were systolic, 52 +/- 16 mm Hg; diastolic, 29 +/- 11 mm Hg; and mean, 40 +/- 12 mm Hg. The mean right ventricular oxygen saturation at implant was 51%. Provocative maneuvers, including postural changes, sublingual nitroglycerin, and bicycle exercise, demonstrated expected changes in measured oxygen saturation and pulmonary artery pressures over time. At follow-up of 0.5 to 15.5 months, there were no significant differences between pulmonary artery pressures or oxygen saturation values transmitted from the device and simultaneous measurement with balloon flotation catheters. Four of the pulmonary artery leads dislodged and three demonstrated sensor drift, whereas two of the oxygen saturation sensors failed. Four patients died and four received transplants. Pathological study did not demonstrate injury to the right ventricular outflow tract or pulmonic valve. CONCLUSIONS: Chronic measurement of hemodynamic parameters in the outpatient setting with implantable sensor technology appears to be feasible. The devices are well tolerated without significant untoward effects, and the sensors generally function well over time, providing reliable information. Clinical usefulness remains to be established. 相似文献
12.
13.
It is essential in the simulation of power electronics applications to model magnetic components accurately. In addition to modeling the nonlinear hysteresis behavior, eddy currents and winding losses must be included to provide a realistic model. In practice the losses in magnetic components give rise to significant temperature increases which can lead to major changes in the component behavior. In this paper a model of magnetic components is presented which integrates a nonlinear model of hysteresis, electro-magnetic windings and thermal behavior in a single model for use in circuit simulation of power electronics systems. Measurements and simulations are presented which demonstrate the accuracy of the approach for the electrical, magnetic and thermal domains across a variety of operating conditions, including static thermal conditions and dynamic self heating 相似文献
14.
15.
16.
Networks are one of the most significant developments in computing and a hallmark of modern society. However, along with increasing efficiency and productivity, both at home and in the workplace, networks have costs. One cost is the additional energy that electronic devices consume when attached to networks. Power management, a standard feature of modern PCs, was primarily developed to increase battery lifetime in laptop PCs, which historically were not network-connected when using battery power. Today, however, many laptops are connected to a network - typically a Wi-Fi network - as are the majority of desktop computers. Three key drivers of energy use are induced consumption by devices prevented by network connections from entering low-power states, increasing link data rates that inherently consume more energy for the network interfaces, and proliferation of network-connected displays that actively update and display data when no one is present. 相似文献
17.
Studies of elemental distributions within discrete coal macerals: Use of secondary ion mass spectrometry and X-ray photoelectron spectroscopy 总被引:3,自引:0,他引:3
N.Stewart Mclntyre Ronald R. Martin William J. Chauvin C.Gordon Winder James R. Brown J.Anthony MacPhee 《Fuel》1985,64(12):1705-1712
Secondary ion mass spectrometry has been used to measure qualitatively the distributions of many trace and minor elements within some well-characterized coal macerals: vitrinite, fusinite and exinite. Complementary information was obtained by using X-ray photoelectron spectroscopy. Within the vitrinite specimens studied, a widely-dispersed largely inorganic aluminosilicate phase was identified, which contained a number of other trace elements. By contrast, within the organic-rich phase of this macerai, titanium was detected in a very even distribution; this suggests that some titanium may be bonded in an organic complex. The fusinite was shown to contain elevated concentrations of calcium, magnesium and fluorine, dispersed over a large portion of the maceral. The high fluorine content could be identified as an organo-fluoro compound using XPS. Exinite was found to contain lower concentrations of most elements, compared to other macerals. The organic composition of this maceral was significantly different from that of surrounding macerals; this could be seen from the enhanced emission of the C2H2-secondary ion and images of this ion thus clearly outlined the position of such macerals. 相似文献
18.
Brown Michael T.; White Michael J.; Gerstein Lawrence H. 《Canadian Metallurgical Quarterly》1989,36(2):183
Examined the association between self-monitoring and occupational preferences. 237 undergraduates completed Snyder and Gangestad's (1986) revised self-monitoring scale and Holland's (1977) Vocational Preference Inventory (VPI). Regression analyses showed that men who valued congruence between their beliefs and behavior (i.e., low self-monitors) preferred social occupations. Men who were inclined to modify their behavior to fit social situations (i.e., high self-monitors) preferred enterprising occupations. In contrast, high self-monitoring women preferred artistic occupations. It is argued that these gender-neutral occupations permit high self-monitoring women to use their social skills but without the constraints found in male dominated enterprising occupations. Results support the assumption that people prefer occupations compatible with their social skills. Implications for career counseling and further research are noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
20.
Paraquat (1,1'-dimethyl-4,4'-dipyridylium) is an herbicide associated with both accidental and intentional ingestion, leading to severe and often fatal toxicity. Prognosis is largely dependent on the amount of paraquat absorbed. Rapid identification of the symptoms of paraquat toxicity (burns or ulceration at the site of ingestion or injection, acute respiratory distress, and renal failure) can facilitate early treatment intervention to limit absorption. We report a case of a 71-year-old man with a suicidal ingestion of paraquat 2 days prior to presentation. Serum paraquat levels, time elapsed since ingestion, and clinical symptoms all indicated poor prognosis. The patient developed severe respiratory distress and progressive renal failure, and died 6 days after admission to the hospital. 相似文献