全文获取类型
收费全文 | 622314篇 |
免费 | 8861篇 |
国内免费 | 2335篇 |
专业分类
电工技术 | 11787篇 |
综合类 | 1154篇 |
化学工业 | 91603篇 |
金属工艺 | 25206篇 |
机械仪表 | 19517篇 |
建筑科学 | 14244篇 |
矿业工程 | 2938篇 |
能源动力 | 16528篇 |
轻工业 | 49429篇 |
水利工程 | 6019篇 |
石油天然气 | 8977篇 |
武器工业 | 24篇 |
无线电 | 73486篇 |
一般工业技术 | 118955篇 |
冶金工业 | 127743篇 |
原子能技术 | 12148篇 |
自动化技术 | 53752篇 |
出版年
2021年 | 5092篇 |
2020年 | 3771篇 |
2019年 | 4907篇 |
2018年 | 8611篇 |
2017年 | 8741篇 |
2016年 | 9671篇 |
2015年 | 6471篇 |
2014年 | 9779篇 |
2013年 | 28548篇 |
2012年 | 17090篇 |
2011年 | 22938篇 |
2010年 | 17211篇 |
2009年 | 19375篇 |
2008年 | 19985篇 |
2007年 | 19817篇 |
2006年 | 17954篇 |
2005年 | 18837篇 |
2004年 | 17328篇 |
2003年 | 16854篇 |
2002年 | 15254篇 |
2001年 | 15044篇 |
2000年 | 13594篇 |
1999年 | 14639篇 |
1998年 | 40025篇 |
1997年 | 27668篇 |
1996年 | 21244篇 |
1995年 | 15506篇 |
1994年 | 13544篇 |
1993年 | 13524篇 |
1992年 | 9396篇 |
1991年 | 9044篇 |
1990年 | 8726篇 |
1989年 | 8309篇 |
1988年 | 8016篇 |
1987年 | 6997篇 |
1986年 | 6827篇 |
1985年 | 7768篇 |
1984年 | 7012篇 |
1983年 | 6350篇 |
1982年 | 5940篇 |
1981年 | 6099篇 |
1980年 | 5698篇 |
1979年 | 5358篇 |
1978年 | 5348篇 |
1977年 | 6711篇 |
1976年 | 9543篇 |
1975年 | 4599篇 |
1974年 | 4311篇 |
1973年 | 4340篇 |
1972年 | 3655篇 |
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
71.
Wojciech Jó?wicki Anna A. Bro?yna Jerzy Siekiera Andrzej T. Slominski 《International journal of molecular sciences》2015,16(2):3783-3803
RCAS1 is a protein that participates in regulation of the tumor microenvironment and its immune responses, all in order to evade the immune system. The aim of this study was to analyze RCAS1 expression in urothelial bladder cancer cells (and in fibroblasts and macrophages of the tumor stroma) and its relationship with the histological pattern of malignancy. Eighty-three postcystectomy patients were enrolled. We analyzed the histological maturity (grade), progress (pT stage), tissue invasion type (TIT), nonclassic differentiation number (NDN), and the ability to metastasize (pN). The expression of RCAS1 protein was analyzed by immunohistochemistry. Indicators of histological malignancy were observed solely in association with the RCAS1 expression in cells in the border parts (BPs) of the tumor. Histological malignancy of the tumor, indicated by the pT and pN, and metastasis-free survival time, correlated significantly with RCAS1 expression in tumor neoplastic cells, whereas malignancy determined by grade, TIT, and NDN correlated with RCAS1 expression in fibroblasts and macrophages in the tumor microenvironment. These findings suggest that the increased RCAS1 expression depends on its cellular source and that RCAS1 expression itself is a component of various signaling pathways. The immune escape occurs within the tumor BPs, where the increase in the RCAS1 expression occurs within tumor cells and stromal cells in its microenvironment. We conclude that the histological pattern of tumor malignancy, indicated by grade, TIT, NDN, pT, and pN is a morphological indicator of immune escape. 相似文献
72.
73.
74.
75.
Strength of Materials - The use of a damping system is one of the seismic protection systems that improve the seismic response of structures. The proposed methodology estimates the location (which... 相似文献
76.
Loboda P. I. Minitsky A. V. Byba Ye. G. Sysoev M. O. Radchuk S. V. 《Powder Metallurgy and Metal Ceramics》2020,58(11-12):651-656
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was... 相似文献
77.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献
78.
Wireless Personal Communications - In the fusion experiment, sensitive radio frequency signal diagnostic instruments need to be protected against high power stray radiation coming from the Electron... 相似文献
79.
Sustainable and efficient food supply chain has become an essential component of one’s life. The model proposed in this paper is deeply linked to people's quality of life as a result of which there is a large incentive to fulfil customer demands through it. This proposed model can enhance food quality by making the best possible food quality accessible to customers, construct a sustainable logistics system considering its environmental impact and ensure the customer demand to be fulfilled as fast as possible. In this paper, an extended model is examined that builds a unified planning problem for efficient food logistics operations where four important objectives are viewed: minimising the total expense of the system, maximising the average food quality along with the minimisation of the amount of CO2 emissions in transportation along with production and total weighted delivery lead time minimisation. A four objective mixed integer linear programming model for intelligent food logistics system is developed in the paper. The optimisation of the formulated mathematical model is proposed using a modified multi-objective particle swarm optimisation algorithm with multiple social structures: MO-GLNPSO (Multi-Objective Global Local Near-Neighbour Particle Swarm Optimisation). Computational results of a case study on a given dataset as well as on multiple small, medium and large-scale datasets followed by sensitivity analysis show the potency and effectiveness of the introduced method. Lastly, there has been a scope for future study displayed which would lead to the further progress of these types of models. 相似文献