全文获取类型
收费全文 | 330976篇 |
免费 | 10243篇 |
国内免费 | 5824篇 |
专业分类
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 |
出版年
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.
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.
K M Cooper L Ribeiro P Alves V Vozikis S Tsitsamis G Alfredsson T L?vgren M Tuomola H Takalo A Iitia S S Sterk M Blokland D G Kennedy 《Food Additives & Contaminants》2003,20(9):804-812
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.
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.
Malik Mary L.; Beutler Larry E.; Alimohamed Shabia; Gallagher-Thompson Dolores; Thompson Larry 《Canadian Metallurgical Quarterly》2003,71(1):150
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
L. M. Lyn’kov V. A. Bogush E. A. Senkovets S. M. Zavadskii 《Technical Physics Letters》2003,29(8):641-642
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.