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   3974篇
  免费   21篇
  国内免费   12篇
电工技术   12篇
综合类   15篇
化学工业   34篇
金属工艺   9篇
机械仪表   20篇
建筑科学   23篇
矿业工程   12篇
能源动力   3篇
轻工业   58篇
水利工程   12篇
石油天然气   6篇
武器工业   1篇
无线电   23篇
一般工业技术   20篇
冶金工业   3714篇
原子能技术   10篇
自动化技术   35篇
  2023年   3篇
  2022年   7篇
  2021年   15篇
  2020年   8篇
  2019年   11篇
  2018年   4篇
  2017年   2篇
  2016年   7篇
  2015年   9篇
  2014年   12篇
  2013年   22篇
  2012年   14篇
  2011年   17篇
  2010年   17篇
  2009年   15篇
  2008年   16篇
  2007年   14篇
  2006年   14篇
  2005年   27篇
  2004年   15篇
  2003年   10篇
  2002年   13篇
  2001年   6篇
  2000年   3篇
  1999年   114篇
  1998年   1220篇
  1997年   707篇
  1996年   413篇
  1995年   249篇
  1994年   195篇
  1993年   210篇
  1992年   38篇
  1991年   24篇
  1990年   42篇
  1989年   36篇
  1988年   47篇
  1987年   38篇
  1986年   35篇
  1985年   35篇
  1983年   4篇
  1982年   14篇
  1981年   19篇
  1980年   26篇
  1979年   2篇
  1978年   12篇
  1977年   82篇
  1976年   148篇
  1975年   11篇
  1963年   1篇
  1955年   3篇
排序方式: 共有4007条查询结果,搜索用时 437 毫秒
81.
Meta-analysis applied to eight controlled clinical trials of coenzyme Q10 (CoQ10)-treatment of congestive heart failure revealed a significant improvement a several important cardiac parameters such as ejection fraction (EF), stroke volume (SV), cardiac output (CO), cardiac index (CI) and end diastolic volume index (EDVI). Concerning the improvement in SV and CO the average patient in the CoQ10 group had a higher score than respectively 76% and 73% of the patients in the placebo group. The improvement in CO and SV was also significant when considering of homogeneity. Additional controlled clinical trials seem justified which may strengthen the power of the meta-analyses. However, based on available results, it can not be excluded that CoQ10 may have a future role a adjunctive therapy in a dosage of 100-200 mg/day in the treatment of chronic congestive heart failure.  相似文献   
82.
83.
The involvement of structures in the medial temporal lobe during the encoding of visual associations was studied with functional magnetic resonance imaging. In 11 out of 12 normal healthy volunteers this task resulted in activation in posterior portions of the parahippocampal region, close to the collateral sulcus. In seven subjects activation was encountered in the hippocampal formation. The visual association task as adapted for this study may provide a sensitive measure to study anterograde amnesia prevalent in Alzheimer's disease. Therefore, the present paradigm enables the study of individual changes in learning and memory capacities over time.  相似文献   
84.
85.
Although long-term clinical studies have shown no excessive risk of lymphoma in rheumatoid arthritis (RA) patients treated with methotrexate (MTX), an increasing number of reports of this association continue to appear. We describe two cases, review the cases in the world's literature, and summarize their important characteristics. Possible oncogenic mechanisms are discussed. Most lymphoproliferation cases presented here have features of immunosuppression-associated lymphoma. The immunosuppressed state is attributable to a combination of factors, such as RA itself and the actions of MTX. The risk factors for RA patients to develop lymphoma while on MTX include severe disease, intense immunosuppression, genetic predisposition, and an increased frequency of latent infection with prooncogenic viruses such as Epstein-Barr virus (EBV). The spontaneous remission of lymphomas in eight RA patients after MTX was stopped highlights the likely causative role of the drug in the development of these malignancies. If the clinical situation permits, a period of observation for spontaneous remission after MTX is stopped is advisable. The physicians caring for RA patients on MTX should maintain a high surveillance for signs and symptoms suggestive of lymphoma.  相似文献   
86.
本文叙述了用n-p散射方法刻度快中子探测器效率的基本原理、实验方法和测量结果。400 keV氘束轰击T-Ti靶,由T(d,n)~He反应得到15.2 MeV的中子,散射体是一个圆柱塑料闪烁体(φ2.2×3cm),飞行距离2m,时间分辨率约1.5ns,效率测量的能区范围为1—14MeV,对多次散射和几何条件作了修正,总的误差约2%。  相似文献   
87.
88.
89.
A man with double inlet left ventricle and severe subpulmonary stenosis underwent a Fontan operation at the age of 29 years. Eight years later he developed atrial flutter with complete heart block. To avoid a further thoracotomy, a unipolar carbon tipped electrode was placed into the posterior cardiac vein via the coronary sinus. More than 8 years after implantation of the original lead, and after two generator changes, telemetric thresholds remain between 1.8-2.1 volts. Percutaneous transvenous ventricular pacing via the coronary sinus can produce an excellent long-term result and should be the initial approach of choice after a Fontan-type operation.  相似文献   
90.
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