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   501704篇
  免费   6823篇
  国内免费   2419篇
电工技术   9711篇
技术理论   5篇
综合类   1312篇
化学工业   79797篇
金属工艺   20685篇
机械仪表   15014篇
建筑科学   12414篇
矿业工程   3229篇
能源动力   11401篇
轻工业   46877篇
水利工程   5561篇
石油天然气   11589篇
武器工业   258篇
无线电   54103篇
一般工业技术   96706篇
冶金工业   90843篇
原子能技术   11570篇
自动化技术   39871篇
  2021年   4242篇
  2019年   3753篇
  2018年   6427篇
  2017年   6378篇
  2016年   6923篇
  2015年   4875篇
  2014年   8074篇
  2013年   21701篇
  2012年   13260篇
  2011年   17755篇
  2010年   14411篇
  2009年   15885篇
  2008年   16859篇
  2007年   16894篇
  2006年   14865篇
  2005年   13409篇
  2004年   12253篇
  2003年   11673篇
  2002年   11780篇
  2001年   11713篇
  2000年   10996篇
  1999年   10995篇
  1998年   25338篇
  1997年   18746篇
  1996年   14522篇
  1995年   11085篇
  1994年   10075篇
  1993年   9810篇
  1992年   7684篇
  1991年   7452篇
  1990年   7306篇
  1989年   7368篇
  1988年   7026篇
  1987年   6059篇
  1986年   6040篇
  1985年   6889篇
  1984年   6639篇
  1983年   6127篇
  1982年   5582篇
  1981年   5892篇
  1980年   5544篇
  1979年   5656篇
  1978年   5622篇
  1977年   6220篇
  1976年   8007篇
  1975年   5071篇
  1974年   4827篇
  1973年   4864篇
  1972年   4180篇
  1971年   3823篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
Reports the death of Roger Todd Davis (1926-2002) and how he contributed to the post-WWII development of primatology and primate laboratories, which are important precursors to the study of modern cognition and cognitive neuroscience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
992.
Hoste  K. Eeckhout  L. 《Micro, IEEE》2007,27(3):63-72
For computer designers, understanding the characteristics of workloads running on current and future computer systems is of utmost importance during microprocessor design a microarchitecture-independent method ensures an accurate characterization of inherent program behavior and avoids the weaknesses of microarchitecture-dependent metrics.  相似文献   
993.
Langmuir films (LFs) of biphenyl and anthracene derivatives on the surface of liquid mercury were studied by surface-specific X-ray and surface tension measurements. Phases of lying-down, side-lying and standing-up molecules were found, some of which exhibit long-range lateral order. The molecular symmetry and the position and nature of the side-, end-, and headgroups are shown to dominate the structural evolution of the LFs with surface coverage.  相似文献   
994.
995.
We have studied the reflectivity spectra of doped GaAs nanowhiskers (NWs) with various morphologies, which were grown by molecular-beam epitaxy. It is established that the character of the reflectivity spectra of NWs is determined by the shape of nanocrystals. NWs with droplike and pointlike vertices differently interact with electromagnetic radiation. Laser radiation produces a spectraly selective action on the NW array, which leads to a change in the NW height and induces “caking” of their vertices, thus modifying the reflectivity of the sample. This phenomenon can be used for the creation of local microstructures with preset characteristics in large NW arrays.  相似文献   
996.
Many zeranol immunoassay test kits cross-react with toxins formed by naturally occurring Fusarium spp. fungi, leading to false-positive screening results. This paper describes the evaluation and application of recently published, dry reagent time-resolved fluoroimmunoassays (TR-FIA) for zeranol and the toxin alpha-zearalenol. A ring test of bovine urine fortified with zeranol and/or alpha-zearalenol in four European Union National Reference Laboratories demonstrated that the TR-FIA tests were accurate and robust. The alpha-zearalenol TR-FIA satisfactorily quantified alpha-zearalenol in urine fortified at 10-30 ng ml(-1). The specificity-enhanced zeranol TR-FIA accurately quantified zeranol in the range 2-5 ng ml(-1) and gave no false-positive results in blank urine, even in the presence of 30 ng ml(-1) alpha-zearalenol. Zeranol TR-FIA specificity was demonstrated further by analysing incurred zeranol-free urine samples containing natural Fusarium spp. toxins. The TR-FIA yielded no false-positive results in the presence of up to 22 ng ml(-1) toxins. The performance of four commercially available zeranol immunoassay test kits was more variable. Three kits produced many false-positive results. One kit produced only one potential false-positive using a protocol that was longer than that of the TR-FIA. These TR-FIAs will be valuable tools to develop inspection criteria to distinguish illegal zeranol abuse from contamination arising from in vivo metabolism of Fusarium spp. toxins.  相似文献   
997.
998.
Jean Poerre 《钢铁》2003,38(Z1):101-103
全球变暖给钢铁工业带来了巨大的挑战,挑战涉及使用碳的多少和能量利用率.低强度生产可以短期内达到减轻排放,使处于京都协议要求的水平.从中期看,更多地使用废钢也有助于减轻排放.但是为了实现更多地减少温室气体GHG的排放,也即等于实现京都协议之后的排放目标,钢铁工业必须设想有一个新的生产面貌,这形成了未来时期对它的最大挑战.碳的收集和吸收,碳使用中的代用剂,工艺流程中绿色来源的电和氢的应用,这些在未来10年中是必须要发展的,希望通过广泛地国际合作加以实现.  相似文献   
999.
This study examined organizational family-responsive policies, perceptions of the organization as family supportive, and supervisor support as issues that may be salient to the experience of conflict between paid employment (work) and family roles. Data were collected from 355 managerial personnel in New Zealand. Although work-family conflict and psychological strain were strongly linked, the availability of organizational policies had no significant association with levels of conflict or strain, whereas policy usage was related only to work-to-family interference and not to family-to-work interference. On the other hand, perceptions of the organization as family supportive and supervisor support for work-family balance displayed significant relationships with key variables, highlighting the importance of these variables for interventions designed to ameliorate the negative impact of work-family conflict on managerial well-being. Implications for the effective implementation of family-responsive interventions are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
1000.
The definition of an empirically supported treatment (EST) arguably embodies 2 untested assumptions: (a) that different manualized renditions of the same therapy are functionally equivalent and (b) that therapies can be reliably applied independently of therapist, setting, and format. These assumptions were tested as applied to cognitive therapy (CT), using process data from a large multisite study (N=235) that included 3 cognitive and 6 alternative therapies. Although the non-CTs were more variable than the CTs on 2 of 4 dimensions studied (directiveness and emotional arousal), there was considerable variation among the 3 CTs, even when implemented in the current context of rigorous training, manualization, and adherence checks. Results are discussed as related to the assumptions underlying EST criteria. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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