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   2858篇
  免费   17篇
  国内免费   1篇
电工技术   17篇
综合类   1篇
化学工业   253篇
金属工艺   52篇
机械仪表   16篇
建筑科学   18篇
矿业工程   2篇
能源动力   11篇
轻工业   110篇
水利工程   12篇
石油天然气   2篇
无线电   66篇
一般工业技术   221篇
冶金工业   1971篇
原子能技术   25篇
自动化技术   99篇
  2023年   8篇
  2021年   11篇
  2018年   7篇
  2016年   8篇
  2014年   21篇
  2013年   40篇
  2012年   37篇
  2011年   47篇
  2010年   38篇
  2009年   35篇
  2008年   37篇
  2007年   31篇
  2006年   35篇
  2005年   32篇
  2004年   39篇
  2003年   36篇
  2002年   30篇
  2001年   21篇
  2000年   22篇
  1999年   71篇
  1998年   587篇
  1997年   340篇
  1996年   234篇
  1995年   126篇
  1994年   140篇
  1993年   130篇
  1992年   32篇
  1991年   52篇
  1990年   46篇
  1989年   38篇
  1988年   39篇
  1987年   40篇
  1986年   38篇
  1985年   46篇
  1984年   14篇
  1983年   14篇
  1982年   22篇
  1981年   22篇
  1980年   15篇
  1979年   12篇
  1978年   12篇
  1977年   48篇
  1976年   102篇
  1975年   10篇
  1974年   15篇
  1973年   14篇
  1972年   8篇
  1971年   7篇
  1970年   7篇
  1966年   8篇
排序方式: 共有2876条查询结果,搜索用时 259 毫秒
1.
Some individuals are able to determine the weekday of a given date in a few seconds (finding for instance that June 12, 1900, was a Tuesday). This ability has fascinated scientists for many years because it is predominantly observed in people with limited intelligence and may appear very early in life. Exceptional visual memory, exceptional concentration abilities, or privileged access to lower levels of information not normally available through introspection have been advanced to explain such phenomena. In the present article, the authors show that a simple cognitive model can explain all aspects of the performance of Donny, a young autistic savant who is possibly the fastest and most accurate calendar prodigy ever described. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
2.
3.
Tumor cells from eight freshly isolated cervical cancers (i.e., four adenocarcinomas and four squamous carcinomas) were analyzed for their production of the immune-inhibitory cytokine transforming growth factor-beta (TGF-beta) in vitro. All fresh adenocarcinomas secreted significant levels of TGF-beta (mean 397, range between 207 and 782 pg/ml/10(5) cells/48 hr). In contrast, no detectable TGF-beta was present in the supernatants from the four fresh squamous carcinoma cultures (P < 0.001). These data suggest that major differences in the secretion of the immunoinhibitory cytokine TGF-beta exist between squamous cell carcinomas and adenocarcinomas of the uterine cervix. Furthermore, these findings suggest that at least some of the differences in the natural biologic behavior, as well as in the response to radiation treatment, between these two histologic types of cervical cancer could be related to differences in secretion of this immune-inhibitory cytokine.  相似文献   
4.
5.
6.
7.
8.
In this work the Al85Ni9Nd4Co2 alloy was used as a starting point for examining the possibility of forming bulk glassy Al-based materials by combining rapid quenching and ball milling techniques. Fine glassy powders were obtained by ball milling melt-spun amorphous ribbons using a severe cryogenic processing regime. The thermal stability data of the powders as obtained by constant-rate heating and isothermal DSC experiments together with viscosity measurements are discussed with respect to feasible consolidation conditions. The powder compaction was done by two methods (uni-axial hot pressing and extrusion) at 513 K for up to 15 min. Only the uni-axial hot pressing led to bulk Al85Ni9Nd4Co2 samples with similar glassy structure and Vickers microhardness values comparable to those of the initial melt-spun ribbons.  相似文献   
9.
The Metaflow architecture, a unified approach to maximizing the performance of superscalar microprocessors, is introduced. The Metaflow architecture exploits inherent instruction-level parallelism in conventional sequential programs by hardware means, without relying on optimizing compilers. It is based on a unified structure, the DRIS (deferred-scheduling, register-renaming instruction shelf), that manages out-of-order execution and most of the attendant problems. Coupling the DRIS with a speculative-execution mechanism that avoids conditional branch stalls results in performance limited only be inherent instruction-level parallelism and available execution resources. Although presented in the context of superscalar machines, the technique is equally applicable to a superpipelined implementation. Lightning, the first implementation of the Metaflow architecture, which executes the Sparc RISC instruction set is described  相似文献   
10.
There is no better place to test life-saving resuscitation interventions than in the prehospital setting. Patients rarely survive cardiac arrest if resuscitation techniques have failed before leaving the scene. Also, paramedics are usually very experienced in key initial resuscitative techniques, and they routinely operate under strict paramilitary protocol, resulting in better study compliance. In addition, the large study populations that are derived from emergency medical services (EMS) systems lead to faster study completion and statistically stronger data. Most important, by reinforcing standardized care, rigidly scrutinized trials improve patient care, regardless of the effect of the study intervention. The success of productive EMS research centers requires routine communication between hospital and EMS administrators and their medical directors, designation of mutually acceptable data collectors who guarantee confidentiality, reciprocal exchange of study data provided as educational seminars to the hospitals, commitments to support the budget requests of an EMS program and appropriate system modifications, inclusion of EMS personnel in study design from the very beginning, prospective education of the medical community and media before protocol implementation, an authoritative grassroots medical director, and a paramedic supervisor 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