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   330976篇
  免费   10243篇
  国内免费   5824篇
电工技术   9581篇
技术理论   6篇
综合类   8035篇
化学工业   52978篇
金属工艺   14840篇
机械仪表   12182篇
建筑科学   11488篇
矿业工程   3278篇
能源动力   7486篇
轻工业   32074篇
水利工程   4334篇
石油天然气   8769篇
武器工业   787篇
无线电   36165篇
一般工业技术   56554篇
冶金工业   50153篇
原子能技术   6585篇
自动化技术   31748篇
  2022年   2914篇
  2021年   4510篇
  2020年   3282篇
  2019年   3569篇
  2018年   4933篇
  2017年   5140篇
  2016年   5453篇
  2015年   5253篇
  2014年   7904篇
  2013年   15365篇
  2012年   12444篇
  2011年   15327篇
  2010年   12982篇
  2009年   13459篇
  2008年   14250篇
  2007年   14174篇
  2006年   12926篇
  2005年   11169篇
  2004年   9776篇
  2003年   9009篇
  2002年   9589篇
  2001年   9253篇
  2000年   7895篇
  1999年   7295篇
  1998年   13776篇
  1997年   10299篇
  1996年   7970篇
  1995年   6129篇
  1994年   5520篇
  1993年   5275篇
  1992年   4200篇
  1991年   3945篇
  1990年   3989篇
  1989年   3872篇
  1988年   3635篇
  1987年   3096篇
  1986年   3082篇
  1985年   3452篇
  1984年   3361篇
  1983年   3103篇
  1982年   2716篇
  1981年   2921篇
  1980年   2659篇
  1979年   2852篇
  1978年   2743篇
  1977年   2850篇
  1976年   3707篇
  1975年   2463篇
  1974年   2296篇
  1973年   2323篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
201.
The introduction of multiple, independent production lines has helped many firms to increase their production flexibility, provide for redundancy when equipment breaks down, reduce idle time and labor costs, and achieve many other benefits. This paper introduces and formalizes the multiple U-line balancing problem. Optimal solution methodologies are provided for Type I (minimize the number of stations for a given cycle time), Type II (minimize the cycle time for a given number of stations), and cost-minimization line-balancing problems. A branch-and-bound algorithm is also developed for the situation in which equipment requirements are dependent on the line configuration and the task assignment to stations. Computational results indicate that the greatest benefit of exploiting multiple lines occurs for smaller cycle-time problems that require higher output.  相似文献   
202.
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   
203.
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   
204.
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   
205.
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   
206.
曹红梅 《山西建筑》2003,29(18):34-35
介绍了阳泉市煤矿采空区对公路建设所造成的危害,对其上覆岩层变形破坏的地质因素及其破坏机理作了分析,指出应该采取各种措施减少对公路的破坏。  相似文献   
207.
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   
208.
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   
209.
Thin-film nickel coatings on fiber materials   总被引:1,自引:0,他引:1  
Vacuum deposition of thin films onto fiber materials is a promising method of obtaining electromagnetic screens. We have studied the structure and the electromagnetic properties of machine-knitted fabric coated with nickel by means of magnetron sputtering. When the fabric is irradiated from the metal-coated side, the reflection coefficient is higher by a factor of 1.4 as compared to the case when the same source of electromagnetic radiation is situated on the opposite side (facing the uncoated surface), while the absorption coefficient in both cases is the same.  相似文献   
210.
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