全文获取类型
收费全文 | 1821篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 2篇 |
综合类 | 2篇 |
化学工业 | 60篇 |
金属工艺 | 6篇 |
机械仪表 | 4篇 |
建筑科学 | 25篇 |
矿业工程 | 2篇 |
能源动力 | 5篇 |
轻工业 | 30篇 |
水利工程 | 9篇 |
无线电 | 28篇 |
一般工业技术 | 38篇 |
冶金工业 | 1580篇 |
自动化技术 | 37篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 16篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 14篇 |
2007年 | 19篇 |
2006年 | 7篇 |
2005年 | 13篇 |
2004年 | 7篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1999年 | 55篇 |
1998年 | 510篇 |
1997年 | 280篇 |
1996年 | 167篇 |
1995年 | 92篇 |
1994年 | 91篇 |
1993年 | 93篇 |
1992年 | 23篇 |
1991年 | 28篇 |
1990年 | 23篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1986年 | 21篇 |
1985年 | 14篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 37篇 |
1976年 | 103篇 |
1975年 | 6篇 |
1968年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1828条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Retinopathy of prematurity in Frederiksborg County 1988-1990. A prospective investigation, an update
HC Fledelius 《Canadian Metallurgical Quarterly》1993,(210):59-62
A report is given of retinopathy of prematurity findings in a Danish county (pop. 342,000) for birth years 1988-90. Out of 12,116 liveborn infants 200 were followed with eye controls during (at least) the first 3 months. In 135 gestational age and/or birth weight were below 32 weeks/1750 g. Twenty-five had ROP stage 1-2 with uneventful regression. Out of 5 with at least stage 3 ROP 2 had spontaneous regression. Three had cryotherapy; two acquired unilateral blindness, one myopia of prematurity. As part of an ongoing prospective investigation the visual results denote progress as compared to the serious results from the preceding 6 years (6 blind children). For 1982-90 the pooled ROP blindness rate amounted to 18.7/100,000 liveborn, a frequency only to be surpassed by the neighbouring Copenhagen area. Considering correct timing of cryotherapy close observation of small premature infants is recommended. At present our screening limits are 32 weeks gestational age/1750 g birth weight. 相似文献
5.
6.
7.
BACKGROUND: While monotherapy has significant limitations in bipolar disorder, few published data addressing alternatives exist. Treatment algorithms have been proposed, but none have undergone empirical evaluation. This study provides a systematic prospective, open evaluation of the effectiveness and tolerability of a treatment algorithm for patients with histories of mania. METHOD: Twenty-eight symptomatic outpatients from a public mental health facility who were diagnosed as having either bipolar I or schizoaffective illness, bipolar type, entered the study. Minimum blood levels of lithium and divalproex sodium were defined. Medications were pushed to predetermined levels (as tolerated) before proceeding to the next algorithm step. Clinical symptoms were assessed monthly using the Brief Psychiatric Rating Scale (BPRS, 27 item) and Clinical Global Impressions scale. RESULTS: Pretreatment and posttreatment clinical symptoms were compared. Over 50% of patients attained 30% improvement from baseline BPRS after 4 months. Thirty-six percent of patients (N = 10) became mood stable, 46% (N = 13) remained mood unstable, and 18% (N = 5) dropped out before completing the algorithm. Although patients who finished the algorithm were taking more medication, either dosage and/or drugs, somatic complaints did not increase. CONCLUSION: The potential benefit of a defined treatment algorithm was demonstrated for these complex and persistently ill patients. Despite long treatment histories, patients improved with more frequent visits and addition of medication(s). A randomized controlled trial comparing a similar treatment algorithm with treatment-as-usual is warranted. 相似文献
8.
9.
In the theory of thin fluid sheets, governing equations are derived with specific reference to an assumed simple kinematic structure of the flow. There is a separate set of governing equations associated with each degree of complexity of the kinematic structure, forming a hierarchy of models (Green and Naghdi [3] and Shields and Webster [8]). If one is interested in the velocity profile across the sheet, the kinematic structure can be used again to interpret the variables in the governing equations as an approximate flow. This paper is concerned with the properties of this approximate flow.Two important consequences of the field equations (Euler's equations) in the classical, three-dimensional theory of ideal fluids are: conservation of mechanical energy, and conservation of circulation (Kelvin's theorem). The research reported herein provides a proof that mechanical energy is exactly conserved for the approximate flow in each level in this hierarchy. Two types of circulation are considered in the approximate flow: in-sheet circulation which is computed about circuits lying a fixed fractional distance between the top and bottom surfaces of the sheet, and cross-sheet circulation which is computed about circuits lying in a vertical cylindrical surface. It was found that K moments of the in-sheet circulation and K – 1 weighted moments of the cross-sheet circulation are conserved in the Kth level approximate flow. 相似文献
10.
Kathy Shields 《国际互联网参考资料服务季刊》2013,18(3-4):207-218
In Spring 2012, instruction librarians collaborated with first year composition (FYC) faculty to study students’ research habits as they related to writing. We collected process narratives from students in the introductory FYC course at the beginning and end of the fall semester, and a group of librarians and FYC faculty coded them together. Although we did not achieve one of our initial research goals, we still gained valuable insight into how our students perceive sources and the research process. We applied what we learned to create new instructional materials and developed a valuable relationship with FYC faculty. 相似文献