全文获取类型
收费全文 | 10525篇 |
免费 | 1300篇 |
国内免费 | 477篇 |
专业分类
电工技术 | 2083篇 |
技术理论 | 1篇 |
综合类 | 854篇 |
化学工业 | 724篇 |
金属工艺 | 176篇 |
机械仪表 | 382篇 |
建筑科学 | 1032篇 |
矿业工程 | 337篇 |
能源动力 | 720篇 |
轻工业 | 634篇 |
水利工程 | 2875篇 |
石油天然气 | 155篇 |
武器工业 | 37篇 |
无线电 | 421篇 |
一般工业技术 | 365篇 |
冶金工业 | 642篇 |
原子能技术 | 61篇 |
自动化技术 | 803篇 |
出版年
2024年 | 40篇 |
2023年 | 266篇 |
2022年 | 348篇 |
2021年 | 548篇 |
2020年 | 418篇 |
2019年 | 383篇 |
2018年 | 363篇 |
2017年 | 415篇 |
2016年 | 403篇 |
2015年 | 417篇 |
2014年 | 651篇 |
2013年 | 565篇 |
2012年 | 722篇 |
2011年 | 791篇 |
2010年 | 561篇 |
2009年 | 599篇 |
2008年 | 568篇 |
2007年 | 671篇 |
2006年 | 596篇 |
2005年 | 500篇 |
2004年 | 434篇 |
2003年 | 376篇 |
2002年 | 283篇 |
2001年 | 286篇 |
2000年 | 181篇 |
1999年 | 161篇 |
1998年 | 114篇 |
1997年 | 111篇 |
1996年 | 77篇 |
1995年 | 88篇 |
1994年 | 94篇 |
1993年 | 60篇 |
1992年 | 50篇 |
1991年 | 36篇 |
1990年 | 37篇 |
1989年 | 34篇 |
1988年 | 19篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1966年 | 1篇 |
1958年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
991.
Mindfulness is an attribute of consciousness long believed to promote well-being. This research provides a theoretical and empirical examination of the role of mindfulness in psychological well-being. The development and psychometric properties of the dispositional Mindful Attention Awareness Scale (MAAS) are described. Correlational, quasi-experimental, and laboratory studies then show that the MAAS measures a unique quality of consciousness that is related to a variety of well-being constructs, that differentiates mindfulness practitioners from others, and that is associated with enhanced self-awareness. An experience-sampling study shows that both dispositional and state mindfulness predict self-regulated behavior and positive emotional states. Finally, a clinical intervention study with cancer patients demonstrates that increases in mindfulness over time relate to declines in mood disturbance and stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
992.
JL Montesinos E Dalmau C Casas 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(7):753-761
The yeast Candida rugosa produces multiple extracellular lipases. The production of extra‐ and intracellular lipases was investigated in continuous cultures using a sole or different mixtures of carbon sources. Also, the effect of different C:N ratios was tested. Lipase productivity in continuous cultures increased by 50% compared with data obtained from batch fermentations and depended on the dilution rate applied. Maximum yields relative to consumed substrate were obtained with oleic acid at low dilution rate. It was found that during nitrogen limitation, lipase activity was suppressed. All carbon source mixtures tested allowed both cell growth and lipase production, but extra‐ and intracellular lipase activities were affected by the combination of substrates used. Maximum extracellular lipolytic productivity was attained with lactic and oleic acid mixtures, probably due to the non‐repressor effect of these carbon sources. The chemical composition of the biomass also depended on the type of substrate used and was related to the accumulation of lipidic compounds as intracellular inclusions, which were observed when oleic acid was used as the carbon source. The results obtained were compared with previous data from batch and fed‐batch cultures in order to select the best process strategies for the lipase production with C rugosa. The best lipase yields were obtained in fed‐batch fermentations using oleic acid. Copyright © 2003 Society of Chemical Industry 相似文献
993.
994.
介绍一种利用低电压普通集成稳压器LM317精密稳压的150V直流稳压电路,电路采用两个NPN晶体管实现了LM317输入、输出端之间的限压、稳压和输入端的限流,电路结构简单,工作可靠,并且具有较高的稳压精度。 相似文献
995.
通过汽轮机组调速系统伺服马达不复位、主汽门不动作,反推出电磁阀控制线路接线错误,用人为短路压力开关等手段判断出组合油脱扣器活塞卡涩是造成现场延误开车的根本原因,提出完善大机组开车工作票制度、提高人员素质等措施。 相似文献
996.
A. Satrusajang P. Snitwongse R. J. Buresh D. K. Friesen 《Nutrient Cycling in Agroecosystems》1991,28(1):55-65
A field experiment was conducted on a poorly-drained Aeric Paleaquult in northeastern Thailand to determine the effect of N and S fertilizers on yield of rainfed lowland rice (Oryza sativa L.) and to determine the fate of applied15N- and35S-labeled fertilizers. Rice yield and N uptake increased with applied N but not with applied S in either sulfate or elemental S (ES) form. Rice yield was statistically greater for deep placement of urea as urea supergranules (USG) than for all other N fertilizer treatments that included prilled urea (PU), urea amended with a urease inhibitor (phenyl phosphorodiamidate), and ammonium phosphate sulfate (16% N, 8.6% P).The applied15N-labeled urea (37 kg N ha–1) not recovered in the soil/plant system at crop maturity was 85% for basal incorporation, 53% for broadcast at 12 days after transplanting (DT), 27% for broadcast at 5–7 days before panicle initiation (DBPI), and 49% for broadcast at panicle initiation (PI). The basal incorporated S (30 kg ha–1) not recovered in the soil/plant system at crop maturity was 37% for sulfate applied as single superphosphate (SSP) and 34% for ES applied as granulated triple superphosphate fortified with S (S/GTSP). Some basal incorporated15N and35S and some broadcast15N at PI was lost by runoff. Heavy rainfall at 3–4 days after basal N incorporation and at 1 day after PI resulted in water flow from rice fields at higher elevation and total inundation of the 0.15-m-high15N and35S microplot borders. Unrecovered15N was only 14% for 75 kg urea-N ha–1 deep placed as USG at transplanting. This low N loss from USG indicated that leaching was not a major N loss mechanism and that deep placement was relatively effective in preventing runoff loss.In order to assess the susceptibility of fertilizer-S to runoff loss, a subsequent field experiment was conducted to monitor35S activity in floodwater for 42 days after basal incorporation of SSP and S/GTSP. Maximum35S recoveries in the floodwater were 19% for SSP after 7 days and 7% for S/GTSP after 1 day. Recovery of35S in floodwater after 14 days was 12% for SSP and 3% for S/GTSP.This research suggests that on poorly drained soils with a low sorption capacity, a sizeable fraction of the fertilizer S and N remains in the floodwater following application. Runoff could then be an important mechanism of nutrient loss in areas with high probability for inundation following intense rainfall. 相似文献
997.
渭河流域水利水保措施减水减沙效益初步分析 总被引:4,自引:1,他引:3
截止1989年底,渭河流域共有水库361座,塘坝2666座,引水有效灌溉面积40.4万公顷,治理总面积8136km~2,治理度17.1%。以1970年为效益计算起始年,并将全流域划分为18个片,分别采用水文法和水保法计算1970~1989年间各项水利水保措施减水减沙量及综合减水减沙效益。水文法算得的综合减水效益为24.1%,减沙效益为30.6%;水保法算得的结果相应为29.9%和30.8%,两者相近。 相似文献
998.
The aim of this study was to apply the cognitive behavioral model of problematic Internet use to the context of online game use to obtain a better understanding of problematic use of online games and its negative consequences. In total, 597 online game playing adolescents aged 12–22 years participated in this study. Results showed that the cognitive behavioral model of problematic Internet use can also be used in the context of online game use. More specifically, preference for online social interaction, mood regulation and deficient self-regulation appeared to play an important role in predicting negative outcomes from problematic online game use. Together, these cognitions and behaviors explained 79% of the variance of negative outcomes scores. These findings can be used to develop strategies that aim at reducing problematic online game behavior and its negative consequences. 相似文献
999.
并网机组的一次调频功能对于电网的稳定性来说至关重要。随着“两个细则”的发布,电网对一次调频功能的考核越来越严格。在此背景下,本文总结了影响一次调频的11个因素并给出了相应的解决措施,具有一定的借鉴意义。 相似文献
1000.
为了克服传统串级调速系统功率因数低的缺点 ,提出了一种新型斩波式串级调速方案。该方案中的逆变电压与逆变电流的夹角可以在 15 0°与 180°之间变动 ,有效地提高了串级调速系统的功率因数 相似文献