全文获取类型
收费全文 | 4891篇 |
免费 | 49篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 299篇 |
金属工艺 | 48篇 |
机械仪表 | 91篇 |
建筑科学 | 51篇 |
矿业工程 | 6篇 |
能源动力 | 62篇 |
轻工业 | 69篇 |
水利工程 | 5篇 |
石油天然气 | 9篇 |
无线电 | 216篇 |
一般工业技术 | 398篇 |
冶金工业 | 3398篇 |
原子能技术 | 61篇 |
自动化技术 | 218篇 |
出版年
2023年 | 18篇 |
2022年 | 31篇 |
2021年 | 37篇 |
2020年 | 36篇 |
2019年 | 29篇 |
2018年 | 34篇 |
2017年 | 30篇 |
2016年 | 35篇 |
2015年 | 24篇 |
2014年 | 48篇 |
2013年 | 106篇 |
2012年 | 61篇 |
2011年 | 94篇 |
2010年 | 89篇 |
2009年 | 70篇 |
2008年 | 74篇 |
2007年 | 63篇 |
2006年 | 62篇 |
2005年 | 36篇 |
2004年 | 41篇 |
2003年 | 45篇 |
2002年 | 34篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 91篇 |
1998年 | 958篇 |
1997年 | 573篇 |
1996年 | 423篇 |
1995年 | 267篇 |
1994年 | 191篇 |
1993年 | 208篇 |
1992年 | 40篇 |
1991年 | 62篇 |
1990年 | 58篇 |
1989年 | 48篇 |
1988年 | 46篇 |
1987年 | 40篇 |
1986年 | 34篇 |
1985年 | 37篇 |
1984年 | 26篇 |
1983年 | 25篇 |
1982年 | 44篇 |
1981年 | 46篇 |
1980年 | 47篇 |
1979年 | 20篇 |
1978年 | 21篇 |
1977年 | 150篇 |
1976年 | 288篇 |
1975年 | 15篇 |
1973年 | 10篇 |
排序方式: 共有4950条查询结果,搜索用时 15 毫秒
1.
Bhattacharya Subhayan Sinha Sankhamita Roy Sarbani Gupta Amarnath 《The Journal of supercomputing》2020,76(12):9882-9900
The Journal of Supercomputing - Currently, all online social networks (OSNs) are considered to follow a power-law distribution. In this paper, the degree distribution for multiple OSNs has been... 相似文献
2.
3.
V. Sinha M. J. Mills J. C. Williams 《Metallurgical and Materials Transactions A》2006,37(6):2015-2026
A faceted initiation site is observed in Ti-6242 alloy for both the cyclic and static-loading test conditions. In this experimental
study, the crystallographic orientation of the facets has been determined using the electron backscattered diffraction (EBSD)
technique in conjunction with the quantitative tilt fractography in a scanning electron microscope (SEM). Quantitative tilt
fractography analysis has been used to determine the spatial orientation of fracture facets. The results indicate that the
normal-fatigue (no-dwell) fracture facets are oriented at ∼5 deg with respect to the basal plane; the dwell-fatigue fracture
facets are oriented at ∼10 to 15 deg with respect to the basal plane and the static-loading fracture facets are oriented at
∼20 deg with respect to the basal plane. These crystallographic orientation determinations of the fracture facets at the crack-initiation
site can be used to obtain an idea about the type of loading that produced them. 相似文献
4.
5.
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
6.
Pigmented vulvar lesions were observed in a child during a sexual abuse evaluation. Gross examination of the lesions appeared most consistent with bowenoid papulosis; however, biopsy confirmed the lesions to be pigmented apocrine hamartomas. To our knowledge, these rare and benign tumors have never been described as pigmented, but should be added to the differential diagnosis of pigmented vulvar lesions. 相似文献
7.
8.
9.
10.
SA Khotimchenko VM Kodentsova IA Alekseeva SG Vlaskina OA Vrzhesinskaia AA Sokol''nikov LA Kharitonchik IP Aleshko-Ozhevskií LV Sheviakova 《Canadian Metallurgical Quarterly》1997,43(3):158-164
Gamma delta T-Cells represent a minor subpopulation of T-lymphocytes in man and their role in normal and diseased human skin is unknown. This article is a comprehensive review of T-lymphocytes bearing the gamma delta T-cell receptor in normal and pathological human skin. Firstly, we have documented the occurrence of gamma delta T-cells in normal skin and in a range of reactive and malignant skin conditions. We have then discussed the experimental findings regarding the repertoire used by gamma delta T-cells in normal human skin and in cutaneous disorders with an increased percentage of gamma delta T-cells. 相似文献