全文获取类型
收费全文 | 115271篇 |
免费 | 9797篇 |
国内免费 | 6260篇 |
专业分类
电工技术 | 8195篇 |
技术理论 | 25篇 |
综合类 | 10195篇 |
化学工业 | 14692篇 |
金属工艺 | 7710篇 |
机械仪表 | 5797篇 |
建筑科学 | 14670篇 |
矿业工程 | 6633篇 |
能源动力 | 3194篇 |
轻工业 | 10366篇 |
水利工程 | 4439篇 |
石油天然气 | 8760篇 |
武器工业 | 1031篇 |
无线电 | 8560篇 |
一般工业技术 | 8670篇 |
冶金工业 | 9375篇 |
原子能技术 | 1035篇 |
自动化技术 | 7981篇 |
出版年
2024年 | 444篇 |
2023年 | 1298篇 |
2022年 | 2724篇 |
2021年 | 3405篇 |
2020年 | 3656篇 |
2019年 | 2900篇 |
2018年 | 2731篇 |
2017年 | 3379篇 |
2016年 | 3819篇 |
2015年 | 3961篇 |
2014年 | 7093篇 |
2013年 | 6181篇 |
2012年 | 8064篇 |
2011年 | 8662篇 |
2010年 | 6553篇 |
2009年 | 6686篇 |
2008年 | 5866篇 |
2007年 | 7713篇 |
2006年 | 7396篇 |
2005年 | 6502篇 |
2004年 | 5557篇 |
2003年 | 5054篇 |
2002年 | 4242篇 |
2001年 | 3764篇 |
2000年 | 3133篇 |
1999年 | 2429篇 |
1998年 | 1756篇 |
1997年 | 1306篇 |
1996年 | 1113篇 |
1995年 | 826篇 |
1994年 | 671篇 |
1993年 | 445篇 |
1992年 | 404篇 |
1991年 | 286篇 |
1990年 | 226篇 |
1989年 | 188篇 |
1988年 | 136篇 |
1987年 | 98篇 |
1986年 | 82篇 |
1985年 | 92篇 |
1984年 | 58篇 |
1983年 | 31篇 |
1982年 | 39篇 |
1981年 | 44篇 |
1980年 | 40篇 |
1979年 | 18篇 |
1964年 | 21篇 |
1963年 | 16篇 |
1959年 | 23篇 |
1955年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
基于DSP+CPLD的高精度信号发生器 总被引:2,自引:0,他引:2
介绍了基于直接数字式频率合成(DDS)原理的全数字信号发生器(DSP),利用DSP芯片快速、高精度的运算优势以及CPLD芯片灵活的编程逻辑、大容量存储功能的特点,采用通用可编程芯片以及数字波形合成技术,形成高稳定、高精度、高动态的数字合成信号.该信号发生器可产生0~25 kHz的正弦波、三角波和方波,输出电压峰峰值为0~5 V,频率步进1 Hz,幅度步进0.001 V. 相似文献
53.
This paper considers the integration of alternative technical systems (TS) belonging to a wider class of competing TS, into a supersystem. The paper introduces the notion of alternative TS, shows the peculiarities of their incorporation into a supersystem, reveals the mechanisms used for such incorporation, and shows areas of application for the suggested method. 相似文献
54.
Learning Organizations in Construction 总被引:1,自引:0,他引:1
The transformation of organizations from production-oriented entities to proactive learning entities that continuously leverage the knowledge of the workforce is a primary objective of management researchers. This focus has significant relevance to the construction industry where production-related research has predominantly overshadowed organizational development research. As one effort to change this emphasis, the writers present a research effort designed to study current organization learning techniques and technologies fielded by organizations both inside and outside of the construction industry. Through a series of exploratory case studies, the writers developed a maturity model together with the Construction Industry Institute that provides construction organizations with a framework for developing a learning organization culture. The maturity model focuses on learning organization characteristics of leadership, processes and infrastructure, communication/collaboration, education, and culture at the organization, community, and individual levels. This paper introduces the results of that effort including a presentation of the learning organization maturity model, framework application, and the overall characteristics of a learning organization. 相似文献
55.
《功能材料信息》2007,(5)
A dream or interesting problem is to obtain more information based on one measurement,for example to obtain all the thermodynamic functions based on specific heat only. We call it“holographic“study.After more than 10 year‘s efforts,we suggest one possibility(or only one)is to solve an inverse problem(specific heat-phonon spectrum inversion,SPI).In this talk we will review recent development of studies of a class of inverse problems,including Dai‘s exact solution and Chen‘s formula and their unification.T... 相似文献
56.
In these times of global change, many facility emphases are competing for limited resources. Competing factors include, but are not limited to, sustainable design or green buildings; security, hardening or force protection; accessibility; historic preservation; aesthetics; and functionality. Yet, unlimited resources are seldom, if ever, available to fulfill all of these competing requirements in private or public construction. The Georgia Institute of Technology designed a decision matrix to allow owners and planners to balance these competing requirements on a project-by-project basis and to document the rationale. 相似文献
57.
中国硬质合金工业现状及发展趋势 总被引:7,自引:2,他引:5
简要总结了中国硬质合金工业所取得的成就及与国外先进水平比较存在的差距,并对国内外硬质合金市场和技术发展趋势进行了分析。 相似文献
58.
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
59.
60.