全文获取类型
收费全文 | 1599篇 |
免费 | 29篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 17篇 |
综合类 | 1篇 |
化学工业 | 136篇 |
金属工艺 | 17篇 |
机械仪表 | 18篇 |
建筑科学 | 22篇 |
矿业工程 | 4篇 |
能源动力 | 16篇 |
轻工业 | 62篇 |
水利工程 | 4篇 |
无线电 | 76篇 |
一般工业技术 | 122篇 |
冶金工业 | 1061篇 |
原子能技术 | 9篇 |
自动化技术 | 66篇 |
出版年
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 13篇 |
2015年 | 7篇 |
2014年 | 8篇 |
2013年 | 55篇 |
2012年 | 28篇 |
2011年 | 28篇 |
2010年 | 27篇 |
2009年 | 22篇 |
2008年 | 24篇 |
2007年 | 26篇 |
2006年 | 20篇 |
2005年 | 23篇 |
2004年 | 19篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 11篇 |
2000年 | 16篇 |
1999年 | 39篇 |
1998年 | 315篇 |
1997年 | 186篇 |
1996年 | 146篇 |
1995年 | 67篇 |
1994年 | 62篇 |
1993年 | 55篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 16篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 34篇 |
1976年 | 72篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1972年 | 5篇 |
1941年 | 3篇 |
排序方式: 共有1631条查询结果,搜索用时 15 毫秒
41.
A progressive fibrous myopathy may result from chronic intramuscular drug abuse. This complication may mimic other rheumatic disorders and early recognition may prevent disability. The patient described here presented with fixed flexion and extension contracture of hips and knees, respectively, after abusing meperidine and other agents for 3 years. Soft tissues of thighs and buttocks were "wood hard," EMG showed absence of action potentials in affected muscles, and biopsy revealed extensive replacement of muscle with dense, acellular fibrous tissue. Possible mechanisms are discussed. 相似文献
42.
43.
Information vendors, buyers, and users often take the approach that the number of employees equals the number of licensed users. Unfortunately, although assuring virtually unlimited usage of the software or database, this approach can also come with an unlimited cost. A typical vendor contract might read something to the effect that "Vendor A agrees to provide unlimited access to database B for all 200 employees of Firm Z," a relatively straightforward approach. However, there is no logical reason to pay for unused information and access. 相似文献
44.
Contaminated dredged material is often placed in confined disposal facilities (CDFs) designed and managed to control environmental impacts of the disposed sediment. This note presents equations for use in a screening procedure to evaluate the impact of a CDF on groundwater. The hydrologic evaluation of leachate production and quality model was used to simulate leachate production and transport through the foundation considering a range of foundation soil characteristics and contaminant properties. The model results were used to develop predictive equations of contaminant attenuation and travel time in the foundation soils. When used with equations to predict dispersion in the aquifer, contaminant exposures at receptor locations can be predicted, which is essential in leachate screening applications. The approach does not consider degradation or permanent sequestration of contaminants. Therefore, the procedure is conservative in that it may overestimate actual leachate concentrations and underestimate actual travel times. 相似文献
45.
F. Stemme M. Bruns H. Ge?wein M. Schroeder M. Sazegar M. D. Drahus R.-A. Eichel F. Paul J. Hau?elt J. R. Binder 《Journal of Materials Science》2012,47(19):6929-6938
The effects of the thermal processing and iron doping on RF magnetron co-sputtered barium strontium titanate thin film properties have been investigated. X-ray diffraction and Raman spectroscopy have been used to determine the structural evolution of the films as a function of the annealing temperature and the amount of iron dopant. X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy were employed to gain information about the chemical binding states and the defect structure. The enhancement of the quality factor Q, as well as the decreasing permittivity and tunability due to iron acceptor doping are demonstrated. 相似文献
46.
47.
Ultrafiltration based purification strategies for surfactin produced by Bacillus subtilis LB5A using cassava wastewater as substrate 下载免费PDF全文
48.
49.
Christian Schroeder Thomas M. Grupp Bernhard Fritz Christoph Schilling Yan Chevalier Sandra Utzschneider Volkmar Jansson 《Journal of materials science. Materials in medicine》2013,24(5):1319-1325
The reduced intraoperative visibility of minimally invasive implanted unicondylar knee arthroplasty makes it difficult to remove bone and cement debris, which have been reported on the surface of damaged and retrieved bearings. Therefore, the aim of this study was to analyze the influence of bone and cement particles on the wear rate of unicompartmental knee prostheses in vitro. Fixed bearing unicompartmental knee prostheses were tested using a knee-wear-simulator according to the ISO standard 14243-1:2002(E) for 5.0 million cycles. Afterwards bone debris (particle size 671 ± 262 μm) were added to the test fluid in a concentration of 5 g/l for 1.5 million cycles, followed by 1.5 million cycles blended with cement debris (particle size 644 ± 186 μm) in the same concentration. Wear rate, knee-kinematics and wear-pattern were analyzed. The wear rate reached 12.5 ± 1.0 mm3/million cycles in the running-in and decreased during the steady state phase to 4.4 ± 0.91 mm3/million cycles. Bone particles resulted in a wear rate of 3.0 ± 1.27 mm3/million cycles with no influence on the wear rate compared to the steady state phase. Cement particles, however, lead to a significantly higher wear rate (25.0 ± 16.93 mm3/million cycles) compared to the steady state phase. The careful removal of extruded cement debris during implantation may help in reducing wear rate. Bone debris are suggested to have less critical influence on the prostheses wear rate. 相似文献