全文获取类型
收费全文 | 225795篇 |
免费 | 19907篇 |
国内免费 | 14334篇 |
专业分类
电工技术 | 16612篇 |
技术理论 | 77篇 |
综合类 | 23734篇 |
化学工业 | 24713篇 |
金属工艺 | 8366篇 |
机械仪表 | 18543篇 |
建筑科学 | 36197篇 |
矿业工程 | 9066篇 |
能源动力 | 9247篇 |
轻工业 | 14917篇 |
水利工程 | 9725篇 |
石油天然气 | 10138篇 |
武器工业 | 2741篇 |
无线电 | 12203篇 |
一般工业技术 | 21351篇 |
冶金工业 | 9070篇 |
原子能技术 | 2679篇 |
自动化技术 | 30657篇 |
出版年
2024年 | 913篇 |
2023年 | 2852篇 |
2022年 | 5354篇 |
2021年 | 6444篇 |
2020年 | 6784篇 |
2019年 | 5470篇 |
2018年 | 5376篇 |
2017年 | 6590篇 |
2016年 | 8034篇 |
2015年 | 8487篇 |
2014年 | 15496篇 |
2013年 | 14134篇 |
2012年 | 16649篇 |
2011年 | 18268篇 |
2010年 | 13565篇 |
2009年 | 13852篇 |
2008年 | 13007篇 |
2007年 | 15722篇 |
2006年 | 13818篇 |
2005年 | 11852篇 |
2004年 | 10092篇 |
2003年 | 8456篇 |
2002年 | 6702篇 |
2001年 | 5478篇 |
2000年 | 4695篇 |
1999年 | 3834篇 |
1998年 | 3130篇 |
1997年 | 2650篇 |
1996年 | 2184篇 |
1995年 | 1781篇 |
1994年 | 1551篇 |
1993年 | 1150篇 |
1992年 | 1049篇 |
1991年 | 744篇 |
1990年 | 620篇 |
1989年 | 533篇 |
1988年 | 450篇 |
1987年 | 300篇 |
1986年 | 249篇 |
1985年 | 235篇 |
1984年 | 278篇 |
1983年 | 255篇 |
1982年 | 209篇 |
1981年 | 105篇 |
1980年 | 105篇 |
1979年 | 74篇 |
1978年 | 55篇 |
1977年 | 49篇 |
1976年 | 43篇 |
1959年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
针对竣工资料核查工作中遇到的一些常见和普遍存在的问题进行了分析、探讨,指出单位工程竣工资料的核查应以核查基建程序资料、综合管理资料及质量保证资料为重点。 相似文献
182.
综述了近年来超分子主体化合物在分析化学领域的应用研究与进展。分别以冠醚、环糊精、杯芳烃、卟啉4类超分子为主体功能化合物的研究进行了详细的评述,并对这几类主体化合物在分析化学中的应用研究进行了展望。 相似文献
183.
This study tested a partial version of R. W. Lent, S. D. Brown, and G. Hackett's (1994) social-cognitive career theory model. Among 204 high school girls who attended science, math, and engineering (SME) career conferences, the authors used a 4-year longitudinal design to predict the choice of an SME college major and SME self-efficacy and outcome expectations in college. In addition, among students who had declared SME majors, variables assessed in high school and college were used to predict aspirations to become leaders in SME fields. The results generally provided empirical validation of the model. Regression analyses revealed that college SME outcome expectations were associated with plans to become a leader in an SME field. Implications for research and interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
184.
185.
金堆城钼精选尾矿选铜技术进展 总被引:1,自引:0,他引:1
系统介绍了陕西华光实业有限责任公司有色金属选矿厂17年来围绕提高选铜技术经济指标进行的技术改造和科研攻关实践及取得的效果。 相似文献
186.
This paper describes an effective analysis of magnetic shielding based on homogenization. The analyses become time‐consuming if the problems include the magnetic substances having fine structure. The homogenization of the structure makes it possible to analyze effectively the magnetic fields. The authors introduce a method to estimate the effective permeability of the homogenized substance. This method can be applied to any periodic structure made of magnetic substance. The magnetic shielding effects by the structures against direct‐current (DC) fields generated by electric railways are analyzed by using the present method. As a result, it is found that the overhead way and the protective fence near the railway work as a magnetic shield, whose effects can be improved by appropriate arrangement of those constructions. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 7–15, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20310 相似文献
187.
反拍卖采购:一种新的采购模式 总被引:6,自引:0,他引:6
反拍卖采购技术以其新的理念和对信息技术的融合,能够使企业采购成本大幅度降低。通过对我国传统采购模式与反拍卖采购模式的对比分析,可以了解到反拍卖采购技术的应用前景。 相似文献
188.
Measurements of gel time of the epoxy system DGEBA(n=0)/m-XDA were carried out using rheometry and dielectric analysis with the objective of checking the validity of Mangion-Johari equation (DEA) and Harran-Laudouard criterium (rheometry) for gel time determination. In this work, gel times obtained by rheometry and dielectric analysis are compared and conversions at gel time calculated. From the experimental results obtained for gel times it was found a reasonable agreement between the two techniques that lead to gel conversion values very close to those obtained using Flory equation. 相似文献
189.
Present-day computer-aided design (CAD) packages play only a small part in the area of mechanical engineering design, which involves the synthesis and embodiment of physical components to perform a pre-determined function without unwanted side effects. The computer cannot properly help the designer in this task until it is able to capture and process the function requirements of the design. This paper describes the computer system being developed for this purpose at the Engineering Design Centre at Cambridge University Engineering Department. The paper also explores some of the geometrical and programming implications raised. 相似文献
190.
Scale selection using three different representations for images 总被引:1,自引:0,他引:1
J. Martinez-Baena J. A. García J. Fdez-Valdivia Rosa Rodriguez-Sanchez 《Pattern recognition letters》1997,18(14):1453-1467