全文获取类型
收费全文 | 4360篇 |
免费 | 76篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 36篇 |
综合类 | 4篇 |
化学工业 | 673篇 |
金属工艺 | 83篇 |
机械仪表 | 52篇 |
建筑科学 | 189篇 |
矿业工程 | 13篇 |
能源动力 | 134篇 |
轻工业 | 352篇 |
水利工程 | 24篇 |
石油天然气 | 12篇 |
无线电 | 309篇 |
一般工业技术 | 497篇 |
冶金工业 | 1627篇 |
原子能技术 | 36篇 |
自动化技术 | 399篇 |
出版年
2022年 | 23篇 |
2019年 | 36篇 |
2018年 | 30篇 |
2017年 | 39篇 |
2016年 | 49篇 |
2015年 | 37篇 |
2014年 | 46篇 |
2013年 | 174篇 |
2012年 | 95篇 |
2011年 | 133篇 |
2010年 | 107篇 |
2009年 | 112篇 |
2008年 | 120篇 |
2007年 | 115篇 |
2006年 | 107篇 |
2005年 | 119篇 |
2004年 | 94篇 |
2003年 | 93篇 |
2002年 | 99篇 |
2001年 | 65篇 |
2000年 | 69篇 |
1999年 | 90篇 |
1998年 | 346篇 |
1997年 | 251篇 |
1996年 | 163篇 |
1995年 | 133篇 |
1994年 | 145篇 |
1993年 | 102篇 |
1992年 | 63篇 |
1991年 | 72篇 |
1990年 | 67篇 |
1989年 | 59篇 |
1988年 | 63篇 |
1987年 | 48篇 |
1986年 | 60篇 |
1985年 | 72篇 |
1984年 | 70篇 |
1983年 | 49篇 |
1982年 | 56篇 |
1981年 | 66篇 |
1980年 | 49篇 |
1979年 | 44篇 |
1978年 | 35篇 |
1977年 | 72篇 |
1976年 | 89篇 |
1975年 | 61篇 |
1974年 | 33篇 |
1973年 | 42篇 |
1972年 | 42篇 |
1970年 | 32篇 |
排序方式: 共有4440条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Removal of gold from basic solutions containing [Au(CN)2]? has been demonstrated using the inherently conducting polymer polypyrrole. Polymers containing sulfonated aromatic dopants have been found to display a significant ability to remove gold from such solutions. Experiments performed in solutions containing both gold and copper cyanide complexes indicate that the recovery process is not highly selective. However, the polypyrroles used display significantly faster rates of gold recovery than activated carbon. © 2003 Society of Chemical Industry 相似文献
5.
A semiconductor laser rate equation theory is presented that describes sideband injection locking under both weak optical injection and current modulation. By simultaneous optical injection and current modulation, control of both the phase and the frequency of a semiconductor laser is demonstrated. The phase-locked semiconductor laser operates at a different frequency to the optical injection source, with a frequency-difference given by the current modulation frequency. This method can be used to produce broadband sources, such as those producing ultrashort pulses and those required for coherent control, or to create high-frequency electronic oscillator sources with phase control by interference beating 相似文献
6.
BACKGROUND: The enterococci have become important nosocomial pathogens. They can cause multiple site infections and enterococcal bacteremia becomes more frequently associated with a high mortality rate. Previous studies of enterococcal bacteremia showed a variety of results. To establish the significance and importance of enterococci as nosocomial pathogens in this hospital, to characterize their clinical pictures and to search for the risk factors for mortality, this retrospective study was performed. METHODS: There were 208 cases of enterococcal bacteremia which occurred from 1988 to 1992. Twenty-seven cases had no medical charts, dismissing possibility of evaluation. Finally, 181 cases of enterococcal bacteremia were analysed. RESULTS: One hundred and eighteen episodes were nosocomial infections. Polymicrobial bacteremia occurred in 68.5% of the patients and the most common co-isolate was Pseudomonas aeruginosa. Those patients (78.5%) with underlying diseases and malignancies were the most common underlying problems. The portal of entry could be found in 69.6 percent of patients, with the gastrointestinal tract the most common sources. Antimicrobial susceptibility testing showed high gentamicin resistance rate (89.5%), and ampicillin still had about 80 percent sensitivity rate. The group who received specific antibiotic therapy for enterococcus showed lower mortality (36.4% versus 47.6%). Only one case had infective endocarditis. Forty-nine patients suffered from septic shock, the cause of 30 deaths. Totally 75 patients died during hospitalization. Besides sepsis, another major cause of death was their underlying diseases itself. CONCLUSIONS: Enterococci have no doubt become important nosocomial pathogens and enterococcal bacteremia were associated with high mortality, especially in elderly patients with underlying diseases such as malignancy or diabetes. When clinically dealing with sepsis from the gastrointestinal or biliary tract, especially when previous cephalosporins therapy showed no response, the possibility of enterococcal bacteremia should always be considered. 相似文献
7.
T Mukasa Y Khoroku T Tsukahara MY Momoi I Kimura T Momoi 《Canadian Metallurgical Quarterly》1997,232(1):192-197
P19 EC cells undergoes apoptosis during neuronal differentiation induced by retinoic acid. Two CPP32-like proteases, CPP32 and Mch-3, are expressed in untreated and retinoic acid-treated P19 EC cells. CPP32-like activity is remarkably increased in apoptosis during neuronal differentiation of P19 EC cells. Inhibition of CPP32-like proteases prevents apoptosis, suggesting that activation of CPP32-like proteases play central roles in the apoptosis during neuronal differentiation of P19 EC cells. Wortmannin, PI-3K inhibitor, enhances the CPP32-like activity of the retinoic acid-treated P19 EC cells. PI-3K may be involved in the apoptosis during neuronal differentiation as negative regulator. 相似文献
8.
The human 4 hour patch test provides an opportunity to identify substances with significant skin irritation potential without recourse to the use of animals. The protocol is designed to avoid the production of more than mild irritant reactions and meets the highest ethical standards. This paper provides the background to the development of the method and comments on its performance in the light of recent intra- and inter-laboratory investigations. In particular, the value of the method in providing 'gold standard' data for the identification of those substances (or preparations) which should, or should not, be classified as irritant to skin in European legislation is discussed. On the basis of the published data and supplementary investigations, recommendations are made on both the conduct and interpretation of the human 4 hour patch test. Finally, the lack of any necessity for formal validation of this assay is addressed. 相似文献
9.
John C. Hart Gordon W. Lescinsky Daniel J. Sandin Thomas A. DeFanti Louis H. Kauffman 《The Visual computer》1993,9(7):346-355
The pipelined architecture and parallel organization of the AT&T Pixel Machine image computer are described and demonstrated with applications for the visualization of multidimensional fractals, particularly linear fractals and quaternion/ stacked Julia sets. Techniques for pushing the Pixel Machine to its peak abilities are described and apply to more recent parallel image computers as well. 相似文献
10.
Biodegradation of chlorpyrifos was studied in liquid culture media amended with either single or combined eight different plant pathogenic fungi isolated from the continuous cropping wheat fields. The average recovery of chlorpyrifos from the liquid media was found to be 86.1%. The detection limit of chlorpyrifos by the analytical method used was 19 ppb. Data showed that the growth of mixed fungi at concentrations up to 200 ppm of chlorpyrifos was higher than in the control treatment. Chlorpyrifos concentrations declined in the medium of combined fungi more than it did in the medium of any single fungus with increase in the incubation period. The amount of chlorpyrifos recovered was 79.8 ppm (39.9%) in the combined fungal cultures after 21 days. However, those recovered from the media of Fusarium graminearum, F. oxysporum, Rhizoctonia solani, Cladosporium cladosporiodes, Cephalosporium sp., Trichoderma viridi, Alternaria alternata, and Cladorrhinum brunnescens, ranged from 48.0 to 74.8%. The half-life value (T1/2) for chlorpyrifos was 15.8 day in the medium amended with mixed fungi. However, for the single cultures it ranged from 19.3 to 33.0 day. 相似文献