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   1222篇
  免费   12篇
电工技术   12篇
综合类   1篇
化学工业   83篇
金属工艺   10篇
机械仪表   7篇
建筑科学   33篇
能源动力   24篇
轻工业   34篇
水利工程   4篇
石油天然气   2篇
无线电   82篇
一般工业技术   93篇
冶金工业   683篇
原子能技术   21篇
自动化技术   145篇
  2020年   6篇
  2018年   9篇
  2016年   8篇
  2015年   7篇
  2013年   38篇
  2012年   24篇
  2011年   17篇
  2010年   27篇
  2009年   19篇
  2008年   27篇
  2007年   29篇
  2006年   35篇
  2005年   27篇
  2004年   20篇
  2003年   24篇
  2002年   18篇
  2001年   17篇
  2000年   16篇
  1999年   33篇
  1998年   152篇
  1997年   88篇
  1996年   59篇
  1995年   33篇
  1994年   29篇
  1993年   47篇
  1992年   18篇
  1991年   17篇
  1990年   21篇
  1989年   21篇
  1988年   11篇
  1987年   16篇
  1986年   22篇
  1985年   24篇
  1984年   13篇
  1983年   21篇
  1982年   12篇
  1981年   14篇
  1980年   14篇
  1979年   8篇
  1978年   7篇
  1977年   29篇
  1976年   37篇
  1975年   11篇
  1974年   16篇
  1973年   18篇
  1972年   7篇
  1971年   7篇
  1970年   9篇
  1969年   7篇
  1966年   7篇
排序方式: 共有1234条查询结果,搜索用时 15 毫秒
81.
The second harmonic coefficient d36of HgGa2S4has been measured to be 5 times larger than d36(LiNbO3). The birefringence is usefully large.  相似文献   
82.
Under natural growth conditions, bacteria can utilize intricate communication capabilities (e.g. quorum-sensing, chemotactic signalling and plasmid exchange) to cooperatively form (self-organize) complex colonies with elevated adaptability-the colonial pattern is collectively engineered according to the encountered environmental conditions. Bacteria do not genetically store all the information required for creating all possible patterns. Instead, additional information is cooperatively generated as required for the colonial self-organization to proceed. We describe how complex colonial forms (patterns) emerge through the communication-based singular interplay between individual bacteria and the colony. Each bacterium is, by itself, a biotic autonomous system with its own internal cellular informatics capabilities (storage, processing and assessment of information). These afford the cell plasticity to select its response to biochemical messages it receives, including self-alteration and the broadcasting of messages to initiate alterations in other bacteria. Hence, new features can collectively emerge during self-organization from the intracellular level to the whole colony. The cells thus assume newly co-generated traits and abilities that are not explicitly stored in the genetic information of the individuals.  相似文献   
83.
The aim of this study was to evaluate psychosocial quality of life after heart transplantation. We examined 29 patients (25 M and 4 F), average age was 43.5 y (18-62 y). The age at time of heart transplantation was 43 years (17-55 y). The time after heart transplantation was 3.3 year (0.3-9 y). Spielberger's Questionnaire of Anxiety, Knobloch's inventory of neuroticism, Freiburg's Personality Inventory and Quality of Life Inventory were used, 33% of patients demonstrated increasing frequency and 29% of patients increasing intensity of neurotic symptoms. 23% of patients presented increasing levels of anxiety (as a state). The personality dimensions (depression, excitability and low emotional stability) displayed high frequency. The results showed that patients were more satisfied with family support, with sexual activities, and less satisfied with financial situation, social activities, social isolations, sleep, memory, excitability, fatigue. 41.5% of patients returned back to work. The results indicate that these psychosocial factors play an important role in quality of life after heart transplantation. That is why if is necessary to dedicate an increasing attention to them. (Tab. 1, Fig. 6, Ref. 14.)  相似文献   
84.
85.
86.
87.
88.
The 2002 Fusion Summer Study was conducted July 8–19, 2002, in Snowmass, CO, and carried out a critical assessment of major next steps in the fusion energy sciences program in both magnetic fusion energy (MFE) and inertial fusion energy (IFE). The conclusions of this study were based on analysis led by over 60 conveners working with hundreds of members of the fusion energy sciences community extending over eight months. This effort culminated in two weeks of intense discussion by over 250 U.S. and 30 foreign fusion physicists and engineers present at the 2002 Fusion Summer Study. This is the Executive Summary of the study report. Details are posted at http://web.gat.com/snowmass  相似文献   
89.
To quantify the role of failure to request consent as a determinant of the autopsy rate, questionnaires asking whether an autopsy had been requested and the reasons for that decision were distributed to primary physicians after each death in a consecutive series of 75 patient deaths. Autopsies were requested in only 56% of cases. Common reasons to request an autopsy included unanswered medical questions (37%), medical education (22%), research protocol participation (16%), or routine policy (14%). When autopsies were not requested, the most common reason was the belief that there were no outstanding medical questions (64%). Follow-up interviews with 14 oncologists and hematologists revealed that 8 generally request autopsies (usually to contribute to medical education or to discover unexpected findings) and 6 generally do not (usually because no unexpected findings are anticipated). Attempts to increase the current low autopsy rate should address the question of when and why physicians are willing to request this procedure.  相似文献   
90.
Treadmill exercise activates the hypothalamic-pituitary-adrenal axis and evokes metabolic responses proportional to exercise intensity and duration. To determine whether glucocorticoid administration would alter humoral and metabolic regulation during exercise, we administered 4 mg dexamethasone (DEX) or placebo to 11 normal, moderately trained men (19-42 yr old) in a double blinded random fashion 4 h before high intensity intermittent treadmill running. Plasma levels of ACTH, cortisol, arginine vasopressin (AVP), lactate, and glucose were measured before, during, and after exercise. A wide range of ACTH responses were seen in the DEX-treated group and arbitrarily defined as two subsets of individuals according to their responses to dexamethasone: DEX nonsuppressors and DEX suppressors. Exercise-induced increases in heart rate and circulating concentrations of cortisol, AVP, lactate, and glucose were all significantly greater (P < 0.05) in nonsuppressors (n = 4) compared to suppressors (n = 7) after both placebo and DEX administration. Interestingly, heart rate, AVP, and lactate responses were unaltered by DEX alone in both groups. In summary, this study demonstrates that normal individuals exhibit differential neuroendocrine and metabolic responses to exercise and pituitary/adrenal suppression after pretreatment with DEX. These findings reflect marked individual differences in the stress response to exercise that may derive from or lead to differential glucocorticoid negative feedback sensitivity in humans.  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