全文获取类型
收费全文 | 89230篇 |
免费 | 9926篇 |
国内免费 | 5311篇 |
专业分类
电工技术 | 10523篇 |
技术理论 | 7篇 |
综合类 | 7189篇 |
化学工业 | 10368篇 |
金属工艺 | 7776篇 |
机械仪表 | 6200篇 |
建筑科学 | 8123篇 |
矿业工程 | 4855篇 |
能源动力 | 2942篇 |
轻工业 | 7185篇 |
水利工程 | 2766篇 |
石油天然气 | 5043篇 |
武器工业 | 1088篇 |
无线电 | 8645篇 |
一般工业技术 | 7933篇 |
冶金工业 | 6534篇 |
原子能技术 | 1036篇 |
自动化技术 | 6254篇 |
出版年
2024年 | 465篇 |
2023年 | 1306篇 |
2022年 | 2553篇 |
2021年 | 3075篇 |
2020年 | 3324篇 |
2019年 | 2718篇 |
2018年 | 2641篇 |
2017年 | 3152篇 |
2016年 | 3523篇 |
2015年 | 3634篇 |
2014年 | 5822篇 |
2013年 | 4904篇 |
2012年 | 6737篇 |
2011年 | 6805篇 |
2010年 | 4808篇 |
2009年 | 5056篇 |
2008年 | 4535篇 |
2007年 | 5958篇 |
2006年 | 5349篇 |
2005年 | 4561篇 |
2004年 | 3701篇 |
2003年 | 3511篇 |
2002年 | 3025篇 |
2001年 | 2757篇 |
2000年 | 2242篇 |
1999年 | 1822篇 |
1998年 | 1299篇 |
1997年 | 1039篇 |
1996年 | 913篇 |
1995年 | 707篇 |
1994年 | 577篇 |
1993年 | 383篇 |
1992年 | 325篇 |
1991年 | 255篇 |
1990年 | 201篇 |
1989年 | 167篇 |
1988年 | 130篇 |
1987年 | 96篇 |
1986年 | 57篇 |
1985年 | 60篇 |
1984年 | 38篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 28篇 |
1980年 | 31篇 |
1964年 | 13篇 |
1963年 | 8篇 |
1962年 | 8篇 |
1959年 | 19篇 |
1956年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Why are human observers particularly sensitive to human movement? Seven experiments examined the roles of visual experience and motor processes in human movement perception by comparing visual sensitivities to point-light displays of familiar, unusual, and impossible gaits across gait-speed and identity discrimination tasks. In both tasks, visual sensitivity to physically possible gaits was superior to visual sensitivity to physically impossible gaits, supporting perception-action coupling theories of human movement perception. Visual experience influenced walker-identity perception but not gait-speed discrimination. Thus, both motor experience and visual experience define visual sensitivity to human movement. An ecological perspective can be used to define the conditions necessary for experience-dependent sensitivity to human movement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
43.
44.
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
45.
本文介绍了由西门子S7—226PLC与MM440变频器组成的电气控制系统在光缆护套机速度控制中的应用。并对该系统的控制原理作了详细的阐述。 相似文献
46.
《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
47.
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
48.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
49.
The width of the transition layer between the crystalline and amorphous zones in nylon 1010 was determined by SAXS with point collimation and long-slit collimation, respectively. The width of the transition layer, E, was found to be 1.7 nm. The results show that the width of the transition layer is independent of crystallinity. 相似文献
50.
针对铜鼓县小水电站联网时存在的问题及其不利影响进行了分析,井提出了改进途径,指出小水电站的联网改造应立足安全,争取效益。 相似文献