全文获取类型
收费全文 | 2566篇 |
免费 | 17篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 9篇 |
综合类 | 2篇 |
化学工业 | 102篇 |
金属工艺 | 14篇 |
机械仪表 | 36篇 |
建筑科学 | 38篇 |
矿业工程 | 2篇 |
能源动力 | 9篇 |
轻工业 | 47篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
无线电 | 67篇 |
一般工业技术 | 139篇 |
冶金工业 | 2035篇 |
原子能技术 | 5篇 |
自动化技术 | 79篇 |
出版年
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 10篇 |
2014年 | 16篇 |
2013年 | 47篇 |
2012年 | 16篇 |
2011年 | 26篇 |
2010年 | 27篇 |
2009年 | 15篇 |
2008年 | 16篇 |
2007年 | 35篇 |
2006年 | 24篇 |
2005年 | 18篇 |
2004年 | 16篇 |
2003年 | 14篇 |
2002年 | 16篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 61篇 |
1998年 | 657篇 |
1997年 | 374篇 |
1996年 | 214篇 |
1995年 | 149篇 |
1994年 | 117篇 |
1993年 | 127篇 |
1992年 | 17篇 |
1991年 | 37篇 |
1990年 | 30篇 |
1989年 | 35篇 |
1988年 | 37篇 |
1987年 | 32篇 |
1986年 | 29篇 |
1985年 | 26篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 28篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 31篇 |
1976年 | 91篇 |
1975年 | 4篇 |
1973年 | 5篇 |
1970年 | 4篇 |
排序方式: 共有2588条查询结果,搜索用时 625 毫秒
1.
Annette L. West Louise V. Michaelson Elizabeth A. Miles Richard P. Haslam Karen A. Lillycrop Ramona Georgescu Lihua Han Johnathan A. Napier Philip C. Calder Graham C. Burdge 《Lipids》2021,56(2):229-242
The phospholipid composition of lipoproteins is determined by the specificity of hepatic phospholipid biosynthesis. Plasma phospholipid 20:4n-6 and 22:6n-3 concentrations are higher in women than in men. We used this sex difference in a lipidomics analysis of the impact of endocrine factors on the phospholipid class and molecular species composition of fasting plasma from young men and women. Diester species predominated in all lipid classes measured. 20/54 Phosphatidylcholine (PtdCho) species were alkyl ester, 15/48 phosphatidylethanolamine (PtdEtn) species were alkyl ester, and 12/48 PtdEtn species were alkenyl ester. There were no significant differences between sexes in the proportions of alkyl PtdCho species. The proportion of alkyl ester PtdEtn species was greater in women than men, while the proportion of alkenyl ester PtdEtn species was greater in men than women. None of the phosphatidylinositol (PtdIns) or phosphatidylserine (PtdSer) molecular species contained ether-linked fatty acids. The proportion of PtdCho16:0_22:6, and the proportions of PtdEtn O-16:0_20:4 and PtdEtn O-18:2_20:4 were greater in women than men. There were no sex differences in PtdIns and PtdSer molecular species compositions. These findings show that plasma phospholipids can be modified by sex. Such differences in lipoprotein phospholipid composition could contribute to sexual dimorphism in patterns of health and disease. 相似文献
2.
Locke Davenport Huyer Serena Mandla Yufeng Wang Scott B. Campbell Bess Yee Christian Euler Benjamin F. Lai A. Dawn Bannerman Dawn S. Y. Lin Miles Montgomery Kayla Nemr Timothy Bender Slava Epelman Radhakrishnan Mahadevan Milica Radisic 《Advanced functional materials》2021,31(6):2003341
Itaconate (ITA) is an emerging powerhouse of innate immunity with therapeutic potential that is limited in its ability to be administered in a soluble form. A library of polyester materials that incorporate ITA into polymer backbones resulting in materials with inherent immunoregulatory behavior is developed. Harnessing hydrolytic degradation release from polyester backbones, ITA polymers result in the mechanism specific immunoregulatory properties on macrophage polarization in vitro. In a functional assay, the polymer-released ITA inhibits bacterial growth on acetate. Translation to an in vivo model of biomaterial associated inflammation, intraperitoneal injection of ITA polymers demonstrate a rapid resolution of inflammation in comparison to a control polymer silicone, demonstrating the value of sustained biomimetic presentation of ITA. 相似文献
3.
Lead content of rice collected from various areas in the world 总被引:1,自引:0,他引:1
ZW Zhang CS Moon T Watanabe S Shimbo M Ikeda 《Canadian Metallurgical Quarterly》1996,191(1-2):169-175
Rice samples consumed by local populations were collected between 1990 and 1995 in 17 areas in the world, mostly from Asia (10 areas), but also from 7 areas outside of Asia. In total, 1528 samples were obtained (about one half from Japan) and were analyzed for lead (Pb) by electrothermal atomic absorption spectrometry. When the Pb contents in rice samples were classified into 10 areas in Asia, the highest and the lowest geometric means (GMs) were for Indonesia (38 ng/g) and Australia (2 ng/g), respectively. Among 7 regions outside Asia, the GM was highest for Spain (58 ng/g) and the lowest for the USA. (3 ng/g). Moreover, inter-regional differences were significant, when more than 100 samples from one area were divided into 3-9 regions and GMs for regions were compared. There was a marked difference in Pb contents in rice by areas and regions in the world. Nevertheless, comparison by area of the present results with those reported in literature show that there has been no substantial reduction in Pb in rice in the past decade either in Japan or elsewhere in the world. 相似文献
4.
5.
A failed effort to implement new technology is always a failure to understand and adequately manage the change process. IS professionals are now in the change business and must become experts in managing organizational and human change. 相似文献
6.
Pre-transplant nephrectomy was done in a 25-year-old man for calculous pyelonephritis using a retroperitoneal laparoscopic approach with a newly devised ligature applicator-dissector- kidney retractor. 相似文献
7.
E Bazopoulou-Kyrkanidou P Neou CS Bartsocas S Kyrkanides I Fanourakis 《Canadian Metallurgical Quarterly》1995,6(3):227-232
PURPOSE: To select ideal radiologic projections for mapping and ablation of tachycardias of right ventricular outflow tract (RVOT). METHODS: Ten hearts from human corpses were studied utilizing radiopaque material to identify the pulmonary valve and three distinct sites on this valve: septal anterior (A), septal posterior (P) and free-wall (L). Next, the hearts were filmed in the frontal plane and in oblique projections with 15 degrees increments to the right and to the left. The projections in which the sites were lateralized on the valve, eased radiologic interpretation and were considered ideal for mapping and ablation. Depending on the proximity of the sites to the lateral extremes of the pulmonary valve, the projections were considered ideal ( ), intermediary (++) and inadequate (+). RESULTS: Projections [table: see text] CONCLUSION: The A site of RVOT was best indicated in the 60 and 45 degrees left anterior oblique projections; the 0 degree postero anterior projection was best for mapping the P site; the L region was best explored in the 60 degrees right anterior oblique projection. 相似文献
8.
9.
Knowledge elicitation is accepted as being one of the most problematic areas in the creation of a knowledge-based system.A large amount of research has already concentrated on finding more efficient and effective techniques for eliciting knowledge from an individual expert. However, little attention has been given to the involvement of more than one source of expertise in knowledge-based system development.This paper is based on the authors' practical experience gained when developing a knowledge-based system for the conceptual design of bridges. It shows that the use of more than one expert throughout the knowledge elicitation process can improve both the efficiency of the approach and the quality of the knowledge acquired. 相似文献
10.
Mark Taylor John Miles Dino Bouchlaghem Chimay Anumba 《Canadian Metallurgical Quarterly》2007,21(1):59-62
IT systems for engineers are becoming more numerous and complex and will further proliferate in the future. It is infeasible to expect users to be trained to work with a plethora of systems, especially as many of them will only see occasional use. Therefore, in the near future, systems will need user interfaces that allow intuitive access and usage. This paper examines a new style of user interface based on virtual reality. 相似文献