全文获取类型
收费全文 | 6459篇 |
免费 | 547篇 |
国内免费 | 537篇 |
专业分类
电工技术 | 330篇 |
综合类 | 441篇 |
化学工业 | 586篇 |
金属工艺 | 610篇 |
机械仪表 | 352篇 |
建筑科学 | 399篇 |
矿业工程 | 142篇 |
能源动力 | 110篇 |
轻工业 | 499篇 |
水利工程 | 121篇 |
石油天然气 | 138篇 |
武器工业 | 59篇 |
无线电 | 540篇 |
一般工业技术 | 609篇 |
冶金工业 | 1856篇 |
原子能技术 | 111篇 |
自动化技术 | 640篇 |
出版年
2024年 | 35篇 |
2023年 | 71篇 |
2022年 | 179篇 |
2021年 | 242篇 |
2020年 | 163篇 |
2019年 | 150篇 |
2018年 | 147篇 |
2017年 | 152篇 |
2016年 | 142篇 |
2015年 | 184篇 |
2014年 | 253篇 |
2013年 | 330篇 |
2012年 | 338篇 |
2011年 | 334篇 |
2010年 | 355篇 |
2009年 | 359篇 |
2008年 | 345篇 |
2007年 | 353篇 |
2006年 | 336篇 |
2005年 | 237篇 |
2004年 | 175篇 |
2003年 | 159篇 |
2002年 | 139篇 |
2001年 | 115篇 |
2000年 | 101篇 |
1999年 | 104篇 |
1998年 | 536篇 |
1997年 | 316篇 |
1996年 | 192篇 |
1995年 | 121篇 |
1994年 | 106篇 |
1993年 | 125篇 |
1992年 | 52篇 |
1991年 | 57篇 |
1990年 | 54篇 |
1989年 | 42篇 |
1988年 | 31篇 |
1987年 | 27篇 |
1986年 | 28篇 |
1985年 | 29篇 |
1984年 | 10篇 |
1983年 | 20篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1978年 | 13篇 |
1977年 | 41篇 |
1976年 | 97篇 |
1975年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有7543条查询结果,搜索用时 15 毫秒
41.
42.
43.
T.‐S. Kang B.S. Harrison M. Bouguettaya T.J. Foley J.M. Boncella K.S. Schanze J.R. Reynolds 《Advanced functional materials》2003,13(3):205-210
Near‐infrared‐emitting electroluminescent (EL) devices using blue‐light‐emitting polymers blended with the Yb complexes Yb(DBM)3phen (DBM = dibenzoylmethane), Yb(DNM)3phen (DNM = dinaphthoylmethane), and Yb(TPP)L(OEt) (L(OEt) = [(C5H5)Co{P(O)Et2}3]–) have been studied. EL devices composed of Yb(DNM)3phen blended with PPP‐OR11 showed enhanced near‐IR output at 977 nm when compared to those fabricated with Yb(DBM)3phen/PPP‐OR11 blends. The maximum near‐IR external efficiencies of the devices with Yb(DBM)3phen and Yb(DNM)3phen are, respectively, 7 × 10–5 (at 6 V and at 0.81 mA mm–2) and 4 × 10–4 (at 7 V, and 0.74 mA mm–2). The optimal blend composition for EL device performance consisted of PPP‐OR11 blended with 10–20 mol‐% Yb(DNM)3phen. A device fabricated using Yb‐(TPP)L(OEt)/PPP‐OR11 showed significantly enhanced near‐IR output efficiency, and future efforts will focus on devices fabricated using porphyrin‐based materials. 相似文献
44.
Takes issue with the biological focus of traditional theories of sexuality, drawing on postmodern trends such as hermeneutics and social constructionism. It is argued that traditional theories are characterized by a reductionism that precludes meaningfulness and an individualism that precludes genuine intimacy. The theories thus offer an essentially barren account of what is otherwise a richly meaningful human activity. A more fruitful account of human sexuality begins with acknowledging that sexuality is a fundamentally social and meaningful phenomenon and that it can only be understood in the social, historical, and moral context in which human beings live and act. If the linguistic aspect of sexuality were at the heart of theories, biological information could be given its proper place as context for understanding. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
46.
47.
48.
RM Summers J Andrasko-Bourgeois IM Feuerstein SC Hill EC Jones MK Busse B Wise KE Bove BA Rishforth E Tucker TL Spray JM Hoeg 《Canadian Metallurgical Quarterly》1998,98(6):509-518
Hepatitis C chronically infects approximately 1.5% of Americans and is the most common clinical problem facing hepatologists. Since the virus was initially described in 1989, development of an effective therapy has been challenging. Although several different therapeutic agents have been used, no therapy has been shown to reliably eradicate the virus. Interferon-alpha, a cytokine with immunostimulatory and anti-viral properties, has become the therapy of choice for patients with chronic hepatitis C infection. Trials assessing the efficacy of interferon-alpha have characterized host and viral factors predictive of responses to treatment. A thorough understanding of these predictive factors is requisite to providing cost-effective therapeutic decisions for the patient with chronic hepatitis C infection. 相似文献
49.
PP Reynolds 《Canadian Metallurgical Quarterly》1994,120(7):609-614
OBJECTIVE: To determine the role of the clinical training environment and a medical education community in reaffirming medical professionalism among physicians-in-training and faculty. DATA SOURCES: Published articles on undergraduate and graduate medical education and sociology works on professionalism were identified through research. STUDY SELECTION: Studies were selected that illustrated barriers to professionalism in medical education and patient care and the professional conduct of medical students, residents, and faculty. RESULTS: Factors that undermined the medical education community were the specialization of medicine, the faculty reward systems, and the service demands of residency because of the economics of health care. CONCLUSIONS: Establishment of a firm system with a core teaching faculty, creation of mentoring and role modeling programs, implementation of a longitudinal curriculum on medical professionalism, evaluation of physicians on professional conduct, and evaluation of the clinical training environment are suggested as strategies to re-establish an education community and reaffirm professionalism in medicine. 相似文献
50.
A structural model of science achievement and attitude: An extension to high school. 总被引:1,自引:0,他引:1
A previous structural model of Walberg's theory of educational productivity (A. J. Reynolds and H. J. Walberg, 1991) was tested with a national probability sample of 2,535 10th graders for science achievement and attitude. Using data from the Longitudinal Study of American Youth, a 3-wave design incorporated information from students, teachers, and parents. Results indicate that a revised mediated-effects model fit the data best and accounted for substantial variance in Grade 11 science achievement (56%) and attitude (44%). The variables prior achievement, home environment, exposure to mass media through reading, and instructional time had the greatest total effects on science achievement. Prior attitude, home environment, motivation, and prior achievement made the greatest total contributions to science attitude. Although there were different weightings of the factors between the present study and Reynolds and Walberg (1991), both studies support a mediated-effects model of educational productivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献