全文获取类型
收费全文 | 6341篇 |
免费 | 50篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 22篇 |
综合类 | 3篇 |
化学工业 | 357篇 |
金属工艺 | 83篇 |
机械仪表 | 39篇 |
建筑科学 | 93篇 |
矿业工程 | 10篇 |
能源动力 | 31篇 |
轻工业 | 195篇 |
水利工程 | 9篇 |
石油天然气 | 26篇 |
无线电 | 244篇 |
一般工业技术 | 373篇 |
冶金工业 | 4627篇 |
原子能技术 | 17篇 |
自动化技术 | 271篇 |
出版年
2021年 | 24篇 |
2019年 | 20篇 |
2018年 | 21篇 |
2016年 | 30篇 |
2015年 | 26篇 |
2014年 | 36篇 |
2013年 | 104篇 |
2012年 | 55篇 |
2011年 | 67篇 |
2010年 | 73篇 |
2009年 | 72篇 |
2008年 | 81篇 |
2007年 | 75篇 |
2006年 | 76篇 |
2005年 | 59篇 |
2004年 | 59篇 |
2003年 | 66篇 |
2002年 | 67篇 |
2001年 | 43篇 |
2000年 | 60篇 |
1999年 | 172篇 |
1998年 | 1307篇 |
1997年 | 732篇 |
1996年 | 536篇 |
1995年 | 289篇 |
1994年 | 297篇 |
1993年 | 303篇 |
1992年 | 75篇 |
1991年 | 87篇 |
1990年 | 111篇 |
1989年 | 91篇 |
1988年 | 100篇 |
1987年 | 100篇 |
1986年 | 87篇 |
1985年 | 57篇 |
1984年 | 39篇 |
1983年 | 51篇 |
1982年 | 50篇 |
1981年 | 43篇 |
1980年 | 75篇 |
1979年 | 38篇 |
1978年 | 39篇 |
1977年 | 110篇 |
1976年 | 239篇 |
1975年 | 35篇 |
1974年 | 14篇 |
1972年 | 20篇 |
1971年 | 14篇 |
1970年 | 21篇 |
1969年 | 12篇 |
排序方式: 共有6400条查询结果,搜索用时 15 毫秒
11.
OBJECTIVE: To investigate if unexpected behaviour of neonatal and paediatric patients connected to syringe pumps could be explained by transient elevation of these devices. DESIGN: Five different commercially available syringe-pumps were set at an infusion rate of 1 ml/h and then subjected to a vertical displacement manoeuvre (height 1 m). The actual delivered infusion volumes in association with the displacement manoeuvre were measured by a high precision weight scale connected to a computer. SETTING: A medical technology laboratory in a university hospital. MEASUREMENTS AND RESULTS: Elevation of the devices resulted in a rapid bolus injection of 0.19-2.28 ml. Returning the devices to their original positions resulted in an aspiration into the system of 0.06-0.34 ml. The times both for bolus injection and for aspiration into the system were less than 1 min in all cases. The updown manoeuvre was followed by a period with zero infusion ranging from 8 to 105 min. CONCLUSIONS: Design flaws in the construction of syringe pumps can expose patients to substantial danger following vertical displacement if potent drugs are being infused. If potent drugs are infused, care should be taken not to change the vertical position of the syringe pump even for short periods of time. Before buying new equipment, the authors recommend that the delivery characteristics of these devices should not only be tested during ordinary bench testing but should also include the reaction to a vertical displacement manoeuvre. 相似文献
12.
13.
14.
15.
16.
17.
KL Gatford TP Fletcher IJ Clarke PC Owens KJ Quinn PE Walton PA Grant BJ Hosking AR Egan EN Ponnampalam 《Canadian Metallurgical Quarterly》1996,74(6):1314-1325
The effects of sex and age on patterns of circulating somatotropin (ST) concentration and plasma IGF-I, IGF-II, insulin, and IGF binding protein-3 (IGFBP-3) were studied in ram, wether, and ewe lambs (n = 7 or 8) sampled at mean ages of 81 (I1) and 158 d (I2). Between 81 and 158 d of age, rams grew more rapidly than wethers (P < .01), and wethers grew more rapidly than ewes (P < .01). The sex differences in growth were reflected in empty body weight at slaughter: rams > wethers > ewes (P < .05). Mean plasma ST concentrations, ST pulse amplitude, and integrated plasma ST concentrations were greater (P < .05) in rams than in ewes at I1 and I2. Characteristics of the ST plasma profile in wethers were generally intermediate between those of rams and ewes. The interpulse interval was greater in ewes than in wethers at I2. The IGF-I and IGFBP-3 concentrations were greater in rams than in ewes at both sampling times. Plasma IGF-II was greater in ewes than in rams at I2. Mean plasma ST was approximately two thirds less at I2 than at I1 regardless of sex. Mean plasma ST and IGF-I at both ages were positively correlated with growth. Mean plasma ST at I2 was negatively correlated with fatness at slaughter. Sex and age significantly affected patterns of circulating ST and concentrations of IGF-I and IGFBP-3 in prepubertal growing lambs, under conditions for which growth rates and composition were also sexually dimorphic. 相似文献
18.
PA DeLuca 《Canadian Metallurgical Quarterly》1996,43(5):1135-1150
Orthopedic management of children with cerebral palsy is best accomplished with a team approach, which generally is effective in the other neuromotor disabilities of childhood, such as myelomeningocele and muscle disease. Because contracture development is inevitable in growing children with spastic musculature or muscle imbalance and is a prime cause of musculoskeletal dysfunction, its control over time using therapy, bracing, and medication is essential. Problems such as severe contracture, joint deformity, and scoliosis interfere with the basic requirement of comfortable seating in children with quadriplegic involvement and frequently require surgery. In ambulatory children, the use of three-dimensional gait analysis has allowed multilevel surgery to be appropriately planned, minimizing exposure to surgery and therapy. 相似文献
19.
Yan R.-H. Lee K.F. Jeon D.Y. Kim Y.O. Park B.G. Pinto M.R. Rafferty C.S. Tennant D.M. Westerwick E.H. Chin G.M. Morris M.D. Early K. Mulgrew P. Mansfield W.M. Watts R.K. Voshchenkov A.M. Bokor J. Swartz R.G. Ourmazd A. 《Electron Device Letters, IEEE》1992,13(5):256-258
The authors report the implementation of deep-submicrometer Si MOSFETs that at room temperature have a unity-current-gain cutoff frequency (f T) of 89 GHz, for a drain-to-source bias of 1.5 V, a gate-to-source bias of 1 V, a gate oxide thickness of 40 Å, and a channel length of 0.15 μm. The fabrication procedure is mostly conventional, except for the e-beam defined gates. The speed performance is achieved through an intrinsic transit time of only 1.8 ps across the active device region 相似文献
20.
This study examines the ways in which therapists function as attachment figures for patients. Patients in long-term psychoanalytic therapy answered questionnaires about their feelings about their therapists and their closest personal relationships. Components of attachment prominent in the therapeutic relationships were looking up to the therapist and feeling the therapist was responsive to emotional needs. Stronger attachment to therapists was associated with greater frequency and duration of therapy, a stronger working alliance, and greater security of the patients' attachment style, as well as with the gender of the patient and therapist. Using attachment theory to understand psychoanalytic relationships emphasizes the unique importance of a therapist to a patient and can offer new perspectives on both therapeutic and attachment processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献