全文获取类型
收费全文 | 45499篇 |
免费 | 905篇 |
国内免费 | 179篇 |
专业分类
电工技术 | 542篇 |
综合类 | 630篇 |
化学工业 | 4702篇 |
金属工艺 | 588篇 |
机械仪表 | 864篇 |
建筑科学 | 891篇 |
矿业工程 | 393篇 |
能源动力 | 423篇 |
轻工业 | 2140篇 |
水利工程 | 611篇 |
石油天然气 | 50篇 |
武器工业 | 4篇 |
无线电 | 1898篇 |
一般工业技术 | 3494篇 |
冶金工业 | 23480篇 |
原子能技术 | 210篇 |
自动化技术 | 5663篇 |
出版年
2024年 | 55篇 |
2023年 | 191篇 |
2022年 | 125篇 |
2021年 | 119篇 |
2019年 | 64篇 |
2018年 | 467篇 |
2017年 | 687篇 |
2016年 | 1066篇 |
2015年 | 802篇 |
2014年 | 435篇 |
2013年 | 452篇 |
2012年 | 2152篇 |
2011年 | 2473篇 |
2010年 | 698篇 |
2009年 | 785篇 |
2008年 | 635篇 |
2007年 | 645篇 |
2006年 | 586篇 |
2005年 | 3368篇 |
2004年 | 2597篇 |
2003年 | 2072篇 |
2002年 | 856篇 |
2001年 | 757篇 |
2000年 | 289篇 |
1999年 | 685篇 |
1998年 | 6795篇 |
1997年 | 4207篇 |
1996年 | 2762篇 |
1995年 | 1555篇 |
1994年 | 1182篇 |
1993年 | 1240篇 |
1992年 | 266篇 |
1991年 | 336篇 |
1990年 | 328篇 |
1989年 | 303篇 |
1988年 | 319篇 |
1987年 | 242篇 |
1986年 | 233篇 |
1985年 | 201篇 |
1984年 | 72篇 |
1983年 | 90篇 |
1982年 | 140篇 |
1981年 | 193篇 |
1980年 | 210篇 |
1979年 | 61篇 |
1978年 | 109篇 |
1977年 | 647篇 |
1976年 | 1422篇 |
1975年 | 104篇 |
1971年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
Here we present a case of a patient with a massive ossification of annulus fibrosus and longitudinal ligament at the level C3-C4, C4-C5 and C5-C6, also called the Van Swaay bridge. One can observe a propulsion of the pharingeal tissue at the level of the massive Van Swaay bridge between C5 and C6 which caused pressure and dysphagia. 相似文献
93.
94.
Polyarteritis nodosa is a rare disorder and a form of systemic vasculitis. A 48 year-old female was admitted to the hospital because menorrhagia and pelvic pain in February 1993. The patient underwent exploratory laparotomy resulting in a total hysterectomy and bilateral salpingo-oophorectomy for myoma of uterus and a right adnexal cystic mass. Histopathologic examination revealed left ovarian periarteritis nodosa. Further investigation and 9 months follow-up failed to show any systemic involvement. To our knowledge the isolated ovarian polyarteritis nodosa is the first case in the literature. 相似文献
95.
Suggests that it is difficult to get an exact account of gambling behavior in Norway. It appears that gambling behavior in Norway has increased 50% during the observed 5-yr period. Little is known about the prevalence of problematic gambling. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
96.
W Pf?rringer 《Canadian Metallurgical Quarterly》1997,135(4):Oa10-Oa11
97.
DI Timokhin AV Istomin TS Shushkova TG Voronel' IG Mikha?lov 《Canadian Metallurgical Quarterly》1997,(2):19-21
Based on generalization and analysis of instructions and guidelines for therapeutical and prophylactic diets of workers, ways of its optimization were proposed, by using bifide-containing acid dairy products as a preventive agent against possible occupational diseases caused by occupational factors. 相似文献
98.
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
99.
F F?ndrich AM Waaga J Schr?der E Schweizer A Schmid S Jacob HH Wacker P Schroeder 《Canadian Metallurgical Quarterly》1995,27(2):1553-1554
100.
Cortical bone remodeling rates for rib samples from three archaeological populations and a modern autopsy sample were determined using an algorithm developed by Frost (Frost [1987a] Calcif. Tissue Res. 3:211-237). When plotted against the relative antiquities for population samples, histomorphometric variables; i.e., activation frequency (mu rc), net bone formation (netVf,r,t), and mean annual bone formation rate (Vf,r,t), exhibit a concordant trend of increased cortical bone remodeling activity levels over time. Two intensive foraging populations, Windover and Gibson, are similar for all bone remodeling parameters and have the lowest remodeling activity levels among the samples. The more recent Ledders sample, which is reported to practice agricultural subsistence, is consistently intermediate between these and a modern autopsy sample. Although there appear to be differences in bone formation rates among the populations it is concluded that these differences cannot be attributed to differences in bone remodeling rates among the populations, but rather are reflecting different effective ages of adult compacta for their ribs. These findings suggest that the earlier populations, particularly Windsor and Gibson, appear to have reached skeletal maturity at an older age than observed for modern. 相似文献