全文获取类型
收费全文 | 1585篇 |
免费 | 30篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 148篇 |
金属工艺 | 13篇 |
机械仪表 | 30篇 |
建筑科学 | 10篇 |
矿业工程 | 2篇 |
能源动力 | 59篇 |
轻工业 | 43篇 |
水利工程 | 1篇 |
无线电 | 99篇 |
一般工业技术 | 162篇 |
冶金工业 | 923篇 |
原子能技术 | 4篇 |
自动化技术 | 109篇 |
出版年
2023年 | 10篇 |
2022年 | 18篇 |
2021年 | 22篇 |
2020年 | 20篇 |
2019年 | 17篇 |
2018年 | 26篇 |
2017年 | 29篇 |
2016年 | 26篇 |
2015年 | 19篇 |
2014年 | 11篇 |
2013年 | 49篇 |
2012年 | 26篇 |
2011年 | 38篇 |
2010年 | 25篇 |
2009年 | 20篇 |
2008年 | 31篇 |
2007年 | 34篇 |
2006年 | 24篇 |
2005年 | 22篇 |
2004年 | 19篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 34篇 |
1998年 | 314篇 |
1997年 | 185篇 |
1996年 | 111篇 |
1995年 | 53篇 |
1994年 | 55篇 |
1993年 | 52篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 17篇 |
1989年 | 14篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1978年 | 4篇 |
1977年 | 32篇 |
1976年 | 66篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有1617条查询结果,搜索用时 0 毫秒
1.
2.
OA al-Swayeh MS al-Humayyd AA Mustafa AS al-Tuwaijri RS al-Rashed AT Ali 《Canadian Metallurgical Quarterly》1997,12(7):481-489
Recent evidence suggests that oxygen-derived free radicals are involved in mediating gastric microvascular and parenchymal cell injuries induced by ischaemia and reperfusion. Therefore, the effect of the locally acting anti-ulcer drug, sucralfate, was studied on ischaemia and reperfusion (e.g. induced gastric lesions, intraluminal bleeding, changes in vascular permeability and non-protein sulfhydryl levels in the rat stomach). Allopurinol was used as a known standard antioxidant drug. Rats were subjected to 30 min of gastric ischaemia in the presence of 100 mmol/L hydrochloric acid and reperfusion periods of 15, 30 or 60 min duration. The gastric lesions were assessed microscopically under an inverted microscope. The vascular permeability was quantified by measuring the extravasated Evans blue in the stomach. There were significantly greater numbers of gastric lesions, intraluminal bleeding and leakage of Evans blue during all reperfusion periods as compared with those of ischaemia, with maximum effects occurring at 60 min following reperfusion. Pretreatment with sucralfate (31.25-250 mg/kg, p.o.) or allopurinol (12.5-50 mg/kg, i.p.) 30 min before the procedure, dose-dependently reduced the gastric lesions, intraluminal bleeding, and decreased the vascular permeability induced by ischaemia and reperfusion. Furthermore, sucralfate dose-dependently reverses the ischaemia and reperfusion-induced depletion of mucosal non-protein sulfhydryl levels and inhibited the superoxide radical production in both cell-free xanthine-xanthine oxidase and in the stimulated polymorphonuclear cellular systems. These results suggest that the protection produced by sucralfate against gastric injury may be due to its antioxidant effects. 相似文献
3.
V. Vassilev S. Thijs P. L. Segura P. Wambacq P. Leroux G. Groeseneken M. I. Natarajan H. E. Maes M. Steyaert 《Microelectronics Reliability》2005,45(2):255-268
This paper describes an approach to design ESD protection for integrated low noise amplifier (LNA) circuits used in narrowband transceiver front-ends. The RF constraints on the implementation of ESD protection devices are relaxed by co-designing the RF and the ESD blocks, considering them as one single circuit to optimise. The method is applied for the design of 0.25 μm CMOS LNA. Circuit protection levels higher than 3 kV HBM stress are achieved using conventional highly capacitive ggNMOS snapback devices. The methodology can be extended to other RF-CMOS circuits requiring ESD protection by merging the ESD devices in the functionality of the corresponding matching blocks. 相似文献
4.
A focus on the importance of leisure in the development of student nurses has been neglected in the 1990s. This study considers 444 prospective nurses on conventional, diploma and degree courses in two areas of England. It examines their activities associated with socializing, their social support networks and their use of clubs, sports and hobbies before entering nursing. It is evident that students enter nurse training with a wide variety of leisure experiences. Changing recruitment patterns and the structure of nurse training has an effect on the leisure needs of prospective nurses which must be addressed. 相似文献
5.
AT McCray 《Canadian Metallurgical Quarterly》1998,37(4-5):353-360
This paper considers the nature of lexical knowledge and its role in language and information processing. The lexicon is the central component of language and plays a pivotal role in current linguistic theory [3, 4] and, increasingly, in natural language processing systems [5-7]. The lexicon embodies information about the lexical items of the language and serves as the foundation for morphologic, syntactic, and semantic processing. The differences as well as commonalities among dictionaries, thesauri, and lexicons are discussed, and distinctions between words, lexical items, and terms are drawn. Next, the scope and content of the SPECIALIST lexicon are presented, followed by a discussion of certain writing conventions that can be troublesome for text processing applications. One approach to handling orthographic and other lexical variation is discussed in a section that reports on the design and implementation of the SPECIALIST lexical programs. The paper concludes with a discussion of controlled terminologies for the medical domain. Throughout the discussion, examples are drawn from the SPECIALIST lexicon and from the other UMLS knowledge sources [8, 9]. 相似文献
6.
7.
Hongxuan Zhang Venkatesha S. Minahan R. Sherman D. Oweis Y. Natarajan A. Thakor N.V. 《IEEE engineering in medicine and biology magazine》2006,25(4):39-45
Intraoperative neurological monitoring (INM) is the evaluation of the nervous system within the operating room (OR) environment. In this paper, the INM system is tested in a clinical setting in comparison with conventional somatosensory evoked potential (SEP) monitoring. The study results demonstrate the capability of the INM system in extracting clearer and more stable SEP signals. The high SNR of SEP signals collected in various clinical environments, including the OR, makes the INM system a robust platform for continuous monitoring. While the current use of EP monitoring is limited to intermittent analysis by a highly trained clinical neurophysiologist, the authors believe in changing this paradigm by developing continuous monitoring systems, such as the INM system, capable of automated quantitative EP analysis. This noninvasive monitoring modality will allow for a wider range of use in clinical practice. Based on volunteer and clinical patient studies, the INM monitoring system demonstrates much greater reliability and accuracy via the artifact rejection and denoising strategies. It provides more strategic filtering options for different situations under which the clinical SEP response signal could be greatly contaminated and distorted. Furthermore, the INM system offers a promising approach to signal extraction in real-time monitoring during SEP research. 相似文献
8.
GD Ruth S Smith M Bronson AT Davis RM Wilcox 《Canadian Metallurgical Quarterly》2003,24(5):318-21; discussion 317
Nationally, approximately 10% of child abuse cases involve burning, and up to 20% of pediatric burn admissions involve abuse or neglect. Historically, these cases have been more difficult to prosecute than nonburn cases for multiple reasons. Between 1995 and 1999, there were 285 pediatric (under 18) patients admitted to the Spectrum Health Regional Burn Center. Of these cases, 18 of the alleged perpetrators were legally investigated for suspicion of child abuse, and 7 received punitive sentences. We found that men tended to be prosecuted and convicted more often than women and that cases involving multiple instances of injury tended to be prosecuted more frequently. Similarly, we found that cases involving more severe injuries tended to be prosecuted more successfully. There are many psychological and social factors involved in handling burn abuse cases. However, by successful prosecution of these crimes, victims tend to fare better both socially and psychologically. 相似文献
9.
Fundus reflection densitometry or retinal densitometry is a non-invasive technique to examine the visual photopigment kinetics in living eyes. The technique is based on the comparison of the reflected light from the fundus in a fully light adapted eye (when all visual photopigment has been bleached) with the reflected light following complete dark adaptation (when the retina contains its maximum amount of visual photopigment). The technique provides a measure of the density of visual photopigment, its time constant of regeneration, its distribution and spectral characteristics if measured at a series of wavelengths. Fundus reflection densitometry in the human eye was introduced 40 years ago. Presently, it is the only available technique from which direct and objective insight can be obtained into visual photopigment. This knowledge is particularly relevant in eyes where abnormalities of photoreceptor function are suspected. This paper summarizes the current knowledge of fundus reflection densitometry in the diseased and in the aging human retina, gathered over the last 30 years. Considerable improvements of the instrument for clinical purposes have been obtained, and are also discussed. 相似文献
10.
The behavior and suitability of cold-formed lipped angle members for X-bracing with redundant have been studied. For the purpose, two full-scale panel tests were carried out. The first panel was designed so that the compression member would fail by buckling in flexural mode and the second panel in flexural-torsional mode. The members were designed using ASCE Manual No. 52. Theoretical aspects of least radius of gyration and buckling behavior of this bracing system have been discussed. The investigation on first panel, revealed that the member would buckle only in the flexural-torsional mode although flexural buckling would govern the design. The second panel test result showed that, the buckling mode and strength of the system for lipped angle sections can be predicted reasonably well. 相似文献