全文获取类型
收费全文 | 1651篇 |
免费 | 82篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 21篇 |
综合类 | 1篇 |
化学工业 | 433篇 |
金属工艺 | 46篇 |
机械仪表 | 56篇 |
建筑科学 | 71篇 |
矿业工程 | 1篇 |
能源动力 | 34篇 |
轻工业 | 351篇 |
水利工程 | 12篇 |
石油天然气 | 17篇 |
无线电 | 47篇 |
一般工业技术 | 276篇 |
冶金工业 | 140篇 |
原子能技术 | 8篇 |
自动化技术 | 220篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 54篇 |
2021年 | 55篇 |
2020年 | 37篇 |
2019年 | 41篇 |
2018年 | 56篇 |
2017年 | 60篇 |
2016年 | 87篇 |
2015年 | 41篇 |
2014年 | 59篇 |
2013年 | 103篇 |
2012年 | 104篇 |
2011年 | 103篇 |
2010年 | 71篇 |
2009年 | 69篇 |
2008年 | 78篇 |
2007年 | 55篇 |
2006年 | 40篇 |
2005年 | 140篇 |
2004年 | 133篇 |
2003年 | 92篇 |
2002年 | 27篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 6篇 |
1998年 | 42篇 |
1997年 | 24篇 |
1996年 | 23篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 8篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1734条查询结果,搜索用时 328 毫秒
91.
92.
Daniel Carlos Guimarães Pedronette Ricardo da S. Torres 《Journal of Visual Languages and Computing》2011,22(6):453-466
This paper presents the Distance Optimization Algorithm (DOA), a re-ranking method aiming to improve the effectiveness of Content-Based Image Retrieval (CBIR) systems. DOA considers an iterative clustering approach based on distances correlation and on the similarity of ranked lists. The algorithm explores the fact that if two images are similar, their distances to other images and therefore their ranked lists should be similar as well. We also describe how DOA can be used to combine different descriptors and then improve the quality of results of CBIR systems. Conducted experiments involving shape, color, and texture descriptors demonstrate the effectiveness of our method, when compared with state-of-the-art approaches. 相似文献
93.
94.
G.A. Pinto E.F. Gomes F.O. Duro C.M.N. Madureira M.M.B.L. Guimares S. Morais 《Hydrometallurgy》2009,98(3-4):224-234
Solvent extraction is considered as a multi-criteria optimization problem, since several chemical species with similar extraction kinetic properties are frequently present in the aqueous phase and the selective extraction is not practicable. This optimization, applied to mixer–settler units, considers the best parameters and operating conditions, as well as the best structure or process flow-sheet. Global process optimization is performed for a specific flow-sheet and a comparison of Pareto curves for different flow-sheets is made. The positive weight sum approach linked to the sequential quadratic programming method is used to obtain the Pareto set.In all investigated structures, recovery increases with hold-up, residence time and agitation speed, while the purity has an opposite behaviour. For the same treatment capacity, counter-current arrangements are shown to promote recovery without significant impairment in purity. Recycling the aqueous phase is shown to be irrelevant, but organic recycling with as many stages as economically feasible clearly improves the design criteria and reduces the most efficient organic flow-rate. 相似文献
95.
Fernanda Lopes Aldina Santiago Luís Simões da Silva Tim Heistermann Milan Veljkovic José Guilherme da Silva 《钢结构国际杂志》2013,13(3):459-472
The reverse channel connection appears to have the best combination of desirable features under fire loading: moderate construction cost, ability to develop catenary action and extremely high ductility through deformation of the web channel (Ding and Wang, 2007). This paper presents the results of an experimental investigation of a reverse channel component conducted at the University of Coimbra as part of the European RFCS COMPFIRE Project, the main focus of which is to characterise the behaviour of steel joints that connect steel beams to concrete-filled tubular columns under natural fire loading. A series of tensile and compressive tests at ambient and elevated temperatures was conducted. The purposes of the experimental tests were to characterise the strength, stiffness and ductility of this joint component and to establish a relationship between force, displacement and temperature. 相似文献
96.
What is the source of ochratoxin A in wine? 总被引:1,自引:0,他引:1
Cabañes FJ Accensi F Bragulat MR Abarca ML Castellá G Minguez S Pons A 《International journal of food microbiology》2002,79(3):213-215
During a microvinification trial using natural mouldy grapes from a research experimental vineyard, ochratoxin A (OTA) contaminated white wine was obtained. Potential OTA-producing mycobiota of grape samples used in this microvinification process was assessed. Only Aspergillus carbonarius isolates were detected as producers of OTA. Our report is a strong evidence of the contribution of A. carbonarius in the OTA contamination in wine. 相似文献
97.
Simão AG Guimarães LG de Mendonça JP 《Journal of the Optical Society of America. A, Optics, image science, and vision》2002,19(10):2053-2063
A theoretical and numerical investigation is devised for resonant light scattering of an off-axis normally incident Gaussian beam by two parallel nonabsorbing cylinders based on the related beam theory developed in J. Opt. Soc. Am. A 14, 640 (1997). By varying the half-beam width, we show that the multireflection process between the two scatterers can be minimized. Moreover, the study is an attempt to understand the underlying physics present in the process of resonance excitation by evanescent wave coupling. 相似文献
98.
A Guimar?es A Machado S Carvalho H Alaiz L Vieira M Abecasis 《Canadian Metallurgical Quarterly》1998,22(6):595-597
The authors calculated the shunt revision rate for 77 consecutive patients with tumoural obstructive hydrocephalus. At a mean follow up of 23.7 months, the annual revision rate was 0.06 which is significantly lower than the annual revision rate of 0.39 for other hydrocephalic patients treated during the same period. Shunted patients who had total excision of their lesions had a significantly lower revision rate than patients who had a partial excision or a biopsy. It is therefore, suggested that cases with tumoural obstructive hydrocephalus may represent a subset of hydrocephalic patients who are associated with a relatively low risk of shunt complications. The observation has to be addressed when the role of endoscopic third ventriculostomy in these patients is being considered. 相似文献
99.
The authors report a 110 cervical cerclage operations for cervical incompetence. Shirodkar's technique was used and cerclage was carried out between the 9th and 20th week of amenorrhea. Out of 110 patients submitted to the procedure, 98 gave birth to a live infant weighing more than 1000 g which amounts to a success rate of 89%. Duration of pregnancy ranged between 26 and 41 weeks. If only pregnancies having proceeded to 37 weeks of amenorrhea are considered, the success rate amounts to 68%. 相似文献
100.
Olive oil, a major component of the Mediterranean diet, has been associated in some small clinical trials and cross-sectional
studies with a reduction in blood pressure. The objective of this study was to assess the association of olive oil consumption
with the incidence of hypertension in an epidemiologic cohort, the Seguimiento Universidad de Navarra (SUN) study. The SUN
Project is a prospective cohort study whose members are all university graduates. The recruitment and follow-up of participants
is made using mailed questionnaires. Diet was assessed using a semiquantitative food frequency questionnaire previously validated
in Spain, with 136 items. Outcomes of interest were newly diagnosed cases of hypertension, as reported by participants in
the follow-up questionnaires. Logistic regression models were fit to assess the risk of hypertension associated with olive
oil consumption. For the present analysis, we have taken in consideration the first 6,863 participants, with at least 2 yr
of follow-up. After a median follow-up time of 28.5 mon, the cumulative incidence of hypereension was 4.7% in men and 1.7%
in women. A lower risk of hypertension was observed among participants with a higher olive oil consumption at baseline, but
the results were not statistically significant (P=0.13 for the linear trend test in the multivariate model). However, among men, the adjusted odds ratios (OR) (95% confidence
intervals) of hypertension for the second to fifth quintiles of olive oil consumption, compared with the first quintile, were
0.55 (0.28–1.10), 0.75 (0.39–1.43), 0.32 (0.15–0.70), and 0.46 (0.23–0.94), respectively (P=0.02 for linear trend). No association was found between olive oil consumption and the risk of hypertension among women.
In conclusion, in a Mediterranean population, we found olive oil consumption to be associated with a reduced risk of hypertension
only among men. The lack of association observed among women might be attributed to the overall lower incidence of hypertension
found among females and the resulting lower statistical power. 相似文献