全文获取类型
收费全文 | 3318篇 |
免费 | 166篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 17篇 |
综合类 | 4篇 |
化学工业 | 802篇 |
金属工艺 | 40篇 |
机械仪表 | 29篇 |
建筑科学 | 140篇 |
矿业工程 | 4篇 |
能源动力 | 53篇 |
轻工业 | 519篇 |
水利工程 | 29篇 |
石油天然气 | 19篇 |
武器工业 | 1篇 |
无线电 | 172篇 |
一般工业技术 | 537篇 |
冶金工业 | 657篇 |
原子能技术 | 30篇 |
自动化技术 | 433篇 |
出版年
2023年 | 19篇 |
2022年 | 80篇 |
2021年 | 121篇 |
2020年 | 61篇 |
2019年 | 51篇 |
2018年 | 62篇 |
2017年 | 90篇 |
2016年 | 92篇 |
2015年 | 86篇 |
2014年 | 120篇 |
2013年 | 168篇 |
2012年 | 169篇 |
2011年 | 213篇 |
2010年 | 160篇 |
2009年 | 140篇 |
2008年 | 179篇 |
2007年 | 175篇 |
2006年 | 156篇 |
2005年 | 115篇 |
2004年 | 98篇 |
2003年 | 104篇 |
2002年 | 77篇 |
2001年 | 74篇 |
2000年 | 49篇 |
1999年 | 65篇 |
1998年 | 89篇 |
1997年 | 72篇 |
1996年 | 56篇 |
1995年 | 37篇 |
1994年 | 46篇 |
1993年 | 49篇 |
1992年 | 41篇 |
1991年 | 25篇 |
1990年 | 31篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 25篇 |
1984年 | 12篇 |
1983年 | 20篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 19篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 16篇 |
1976年 | 14篇 |
1974年 | 7篇 |
1973年 | 8篇 |
排序方式: 共有3486条查询结果,搜索用时 15 毫秒
1.
2.
McWayne Christine M.; Fantuzzo John W.; McDermott Paul A. 《Canadian Metallurgical Quarterly》2004,40(4):633
The present concurrent study combined developmental and ecological considerations to examine the unique contribution of multiple preschool competencies to an indicator of early academic success. Participants included 195 Head Start children from 32 classrooms representative of a large, urban Head Start program. Dimensional (variable-centered) analyses revealed 3 distinct classroom competency dimensions (i.e., General Classroom Competencies, Specific Approaches to Learning, and Interpersonal Classroom Behavioral Problems). The first 2 of these dimensions were found to be uniquely associated with early academic success. Findings from typological (person-centered) analyses supported the dimensional findings. Typological analyses revealed 7 profiles of classroom competency distinguished by high scores on the dimensions of General Competencies and Approaches to Learning, and these profiles were found to relate differentially to the indicator of early academic success. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
Christine B. Tayntor 《Information Systems Management》1994,11(1):81-83
For many companies, productivity improvements are the watchwords of the 1990s. IS organizations are having to demonstrate increased productivity on an annual basis. For the end-user computing (EUC) department, this requirement often comes in addition to the request to quantify the services it provides, presenting the EUC manager with the proverbial nightmare of juggling two number-one priorities. Which should receive the highest attention? The savvy manager recognizes that the correct answer is both. 相似文献
4.
Letters to the editor 总被引:6,自引:0,他引:6
5.
Third generation mobile radio systems are currently being deployed in different regions of the world. Future systems beyond the third generation are already under discussion in international bodies and forums such as ITU, WWRF and R&D programmes of the European Union and in other regions. These systems will determine the research and standardisation activities in mobile and wireless communication in the next years. Based on experience of the third generation, future systems will be developed mainly from the user perspective with respect to potential services and applications including traffic demands. Therefore, the Wireless World Research Forum was launched in 2001 as a global and open initiative of manufacturers, network operators, SMEs, R&D centres and the academic domain. WWRF is focused on the vision of such systems - the Wireless World-and potential key technologies. This paper describes the international context of activities on systems beyond third generation, the goals, objectives and structure of WWRF, the user perspective as the starting point for a future system design and the key enabling technologies for the Wireless World. 相似文献
6.
In the power industry, current has to be measured for metering and protection purposes. Conventional sensor setups need two transformers to realize the high dynamic range. By the described mixed analog/digital signal processing algorithm, the inherent low photonic noise of the input signals was maintained up to the full sensor output. The system design is based on a rigorous investigation and optimization of the error sources in the signal processing chain. The results are proved by a demonstrator, achieving a dynamic range from 0.05 to 100 times the rated current and a ratio root mean square error of less than 0.5%. 相似文献
7.
8.
T Tillmann K Kamino C Dasenbrock H Ernst M Kohler G Morawietz E Campo A Cardesa L Tomatis U Mohr 《Canadian Metallurgical Quarterly》1997,49(3-4):197-200
An experiment using 4279 CBA/J mice of two generations was carried out to investigate the influence of parental preconceptual exposure to X-ray radiation or to chemical carcinogens. Microchips were implanted subcutaneously in the dorsolateral back for unique identification of each animal. The animals were kept for lifespan under standard laboratory conditions. In 36 mice a circumscribed neoplasm occurred in the area of the implanted microchip. Females were significantly more frequently affected than male mice. An influence of age or different treatment on the s.c. tumour incidence in two mice generations could not be observed. Macroscopically, firm, pale white nodules up to 25 mm in diameter with the microchip in its center were found. Microscopically, soft tissue tumours such as fibrosarcoma and malignant fibrous histiocytoma were detected. 相似文献
9.
In a conceptual replication of A. Biglan et al (see record 1989-39898-001), 288 Ss rated their emotional and behavioral responses to aggressive, distressed, and neutral behaviors. The stimulus behaviors occurred in the context of casual relationships and were portrayed by male and female actors. Consistent with Biglan et al, it was found that aggressive behaviors evoked angry emotions and negative behavioral responses; distressed behaviors evoked both angry and concerned emotions and supportive behavioral responses. However, in contrast to the original results, evidence was also found of negative (primarily avoidant) behavioral responses to distressed behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
Kreppner Jana M.; Rutter Michael; Beckett Celia; Castle Jenny; Colvert Emma; Groothues Christine; Hawkins Amanda; O'Connor Thomas G.; Stevens Suzanne; Sonuga-Barke Edmund J. S. 《Canadian Metallurgical Quarterly》2007,43(4):931
Longitudinal analyses on normal versus impaired functioning across 7 domains were conducted in children who had experienced profound institutional deprivation up to the age of 42 months and were adopted from Romania into U.K. families. Comparisons were made with noninstitutionalized children adopted from Romania and with nondeprived within-U.K. adoptees placed before the age of 6 months. Specifically, the validity of the assessment, the degree of continuity and change in levels of functioning from 6 to 11 years, and the factors in the pre- and postadoption environment accounting for heterogeneity in outcome were examined. Pervasive impairment was significantly raised in children experiencing institutional deprivation for ≥6 months of life, with a minority within this group showing no impairment. There was no additional significant effect of duration of deprivation beyond the 6-month cutoff, and few other predictors explained outcome. The pattern of normality/impairment was mainly established by 6 years of age, with considerable continuity at the individual level between 6 and 11 years. The findings are discussed in terms of the possibility of a sensitive period for development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献