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   43841篇
  免费   970篇
  国内免费   186篇
电工技术   544篇
综合类   632篇
化学工业   4948篇
金属工艺   610篇
机械仪表   895篇
建筑科学   844篇
矿业工程   392篇
能源动力   457篇
轻工业   2107篇
水利工程   603篇
石油天然气   61篇
武器工业   4篇
无线电   1952篇
一般工业技术   3532篇
冶金工业   21504篇
原子能技术   198篇
自动化技术   5714篇
  2023年   206篇
  2022年   147篇
  2021年   144篇
  2019年   79篇
  2018年   513篇
  2017年   725篇
  2016年   1093篇
  2015年   810篇
  2014年   465篇
  2013年   487篇
  2012年   2194篇
  2011年   2478篇
  2010年   716篇
  2009年   799篇
  2008年   635篇
  2007年   652篇
  2006年   580篇
  2005年   3361篇
  2004年   2569篇
  2003年   2058篇
  2002年   864篇
  2001年   745篇
  2000年   286篇
  1999年   630篇
  1998年   6171篇
  1997年   3824篇
  1996年   2520篇
  1995年   1458篇
  1994年   1078篇
  1993年   1115篇
  1992年   256篇
  1991年   313篇
  1990年   315篇
  1989年   294篇
  1988年   301篇
  1987年   234篇
  1986年   212篇
  1985年   176篇
  1984年   83篇
  1983年   89篇
  1982年   139篇
  1981年   187篇
  1980年   204篇
  1979年   66篇
  1978年   102篇
  1977年   614篇
  1976年   1330篇
  1975年   104篇
  1973年   49篇
  1971年   53篇
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
181.
The effects of physical training on elderly, fragile patients with rheumatoid arthritis (RA) who are on low-dose steroids were investigated. The controlled study included 24 patients who had been treated with low-dose steroids for 2 years. Each patient was assigned either to a treatment group receiving training or to an untrained control group. The training took place over a 3-month period and was based on a protocol using progressive interval training consisting of bicycle exercises, heel lifts, and step-climbing. The exercises were performed twice weekly for 45 minutes. Comparison of the two groups showed that disease activity did not increase in the trained group and that fewer, but not significantly fewer, swollen joints were observed in this group (p = 0.06). No significant changes were noticed in erythrocyte sedimentation rate, tender joints, or morning stiffness. The work capacity of the trained patients were doubled and the numbers of repetitions increased 76%. Individually adapted exercise programs can therefore be recommended for elderly rheumatoid arthritis patients on steroid treatment.  相似文献   
182.
183.
The purpose of this study was to examine the role of sleep problems in the etiology of nursing caries. Two-hundred mothers of children (104 with nursing caries and 96 caries free) from ages 2 to 4.5 years were surveyed to determine whether difficulty with child sleep and ensuing sleep-associated feeding might be related to the presence of nursing caries. Differences were noted between these two groups regarding: average number of nights the child slept through the night (P < 0.001); total hours of sleep per night (P < 0.05); frequency of night waking episodes (P < 0.01); feeding on demand upon waking (P < 0.01); using a bottle to assist with falling asleep at night (P < 0.001); and feeding in association with nap time (P < 0.001). Differences also were noted in regard to average age of weaning (P < 0.001). Our findings suggest that sleep problems among young children are a behavioral risk factor for night-time bottle use and early childhood caries.  相似文献   
184.
The most important postweaning factorial diseases are at least partly caused by E. coli. The term postweaning coli complex can be subcategorized into the following manifestations: postweaning diarrhoea, edema disease, postweaning wasting and hemorrhagic gastroenteritis. In the presented study the effect of prophylactic zootechnique alone and zoo- and biotechnique in combination was evaluated during the first weeks postweaning. The results showed that combined zoo- and biotechnique is superior to simple zootechnique regarding food conversion (1.41 kg versus 1.73 kg), average daily weight gain (390 g versus 325 g) and postweaning piglet mortality (3.1% versus 4.9%). It is the opinion of the authors that combined postweaning zoo- and biotechnique should be performed in such pig production units where ETEC and/or SLTEC are present.  相似文献   
185.
186.
Budd Chiari syndrome (liver vein thrombosis) may be a diagnostic and therapeutic problem. On the basis of four different cases we review the major diagnostic and therapeutic principles involved. Imaging techniques are necessary in order to establish the diagnosis. Ultrasound examination with Duplex doppler is usually sufficient, but MR angiography is also useful. Treatment options are thrombolysis, surgery or liver transplantation. What treatment is selected will depend on the clinical situation and the prognosis.  相似文献   
187.
188.
The mortality rate after traumatic brain injury in children ranges between 2.5% and 21%. Standardized diagnostic procedures and therapeutic strategies for the management of traumatic brain damage are presented in this article. Children with traumatic cerebral lesions have a better clinical outcome than head-injured adults. Optimized medical management and intensive rehabilitation may help to reduce the frequency of mental retardation and physical disability following such injuries in children.  相似文献   
189.
The effect of serotonin and the serotonin antagonists ketanserin, methiotepine and ICS-205-930 on the migration of leucocytes was studied by using the sealed capillary migration technique. The migration of mononuclear leucocytes was inhibited by serotonin at 10(-4) and 10(-6)-10(-10)mol/l. An inhibition of the mononuclear leucocyte migration was also caused by ICS-205-930 at 10(-4)mol/l, ketanserin at 10(-4) and 10(-8)-10(-10)mol/l and methiotepine at 10(-4) and 10(-6)-10(-8)mol/l. No inhibiting effects of serotonin or the serotonin antagonists were found on the migration of polymorphonuclear leucocytes. Thus, both serotonin and serotonin antagonists may inhibit mononuclear leucocyte migration.  相似文献   
190.
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