首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   44639篇
  免费   1050篇
  国内免费   178篇
电工技术   546篇
综合类   631篇
化学工业   5050篇
金属工艺   625篇
机械仪表   875篇
建筑科学   919篇
矿业工程   398篇
能源动力   446篇
轻工业   2268篇
水利工程   627篇
石油天然气   49篇
武器工业   4篇
无线电   2021篇
一般工业技术   3839篇
冶金工业   21430篇
原子能技术   190篇
自动化技术   5949篇
  2024年   57篇
  2023年   200篇
  2022年   128篇
  2021年   140篇
  2019年   72篇
  2018年   536篇
  2017年   753篇
  2016年   1149篇
  2015年   845篇
  2014年   506篇
  2013年   573篇
  2012年   2234篇
  2011年   2550篇
  2010年   776篇
  2009年   859篇
  2008年   702篇
  2007年   726篇
  2006年   637篇
  2005年   3414篇
  2004年   2629篇
  2003年   2101篇
  2002年   913篇
  2001年   748篇
  2000年   303篇
  1999年   631篇
  1998年   6166篇
  1997年   3818篇
  1996年   2526篇
  1995年   1461篇
  1994年   1089篇
  1993年   1116篇
  1992年   257篇
  1991年   317篇
  1990年   311篇
  1989年   279篇
  1988年   298篇
  1987年   223篇
  1986年   203篇
  1985年   183篇
  1984年   73篇
  1983年   88篇
  1982年   134篇
  1981年   182篇
  1980年   196篇
  1979年   70篇
  1978年   102篇
  1977年   614篇
  1976年   1322篇
  1975年   100篇
  1973年   50篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
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   
92.
93.
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   
94.
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   
95.
96.
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   
97.
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   
98.
99.
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   
100.
Controlling and diagnostic processes in the bioengineering artificial clearance systems despite of the procedures applied, their functional use and design seem to occur in the artificial organs, each of them consists of controlling and actuating processors ensuring their homogeneous (material, energy-producing, informational) or combined interaction with the patient's body. Centralized control over artificial clearance is proposed by using universal controlling processes which are informationally connected with the operator, the central computer and other controlling processes of the bioengineering system.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号