全文获取类型
收费全文 | 14216篇 |
免费 | 1342篇 |
国内免费 | 733篇 |
专业分类
电工技术 | 558篇 |
技术理论 | 2篇 |
综合类 | 1406篇 |
化学工业 | 2032篇 |
金属工艺 | 161篇 |
机械仪表 | 143篇 |
建筑科学 | 2892篇 |
矿业工程 | 2276篇 |
能源动力 | 824篇 |
轻工业 | 927篇 |
水利工程 | 1622篇 |
石油天然气 | 441篇 |
武器工业 | 24篇 |
无线电 | 387篇 |
一般工业技术 | 360篇 |
冶金工业 | 1260篇 |
原子能技术 | 48篇 |
自动化技术 | 928篇 |
出版年
2024年 | 57篇 |
2023年 | 188篇 |
2022年 | 413篇 |
2021年 | 490篇 |
2020年 | 471篇 |
2019年 | 351篇 |
2018年 | 284篇 |
2017年 | 402篇 |
2016年 | 465篇 |
2015年 | 478篇 |
2014年 | 910篇 |
2013年 | 767篇 |
2012年 | 1056篇 |
2011年 | 1129篇 |
2010年 | 915篇 |
2009年 | 827篇 |
2008年 | 775篇 |
2007年 | 1062篇 |
2006年 | 910篇 |
2005年 | 782篇 |
2004年 | 637篇 |
2003年 | 556篇 |
2002年 | 431篇 |
2001年 | 363篇 |
2000年 | 338篇 |
1999年 | 295篇 |
1998年 | 225篇 |
1997年 | 155篇 |
1996年 | 114篇 |
1995年 | 101篇 |
1994年 | 84篇 |
1993年 | 59篇 |
1992年 | 58篇 |
1991年 | 37篇 |
1990年 | 28篇 |
1989年 | 20篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1957年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
针对公路用地统计繁琐的特点,提出了相关的处理方法。采用AutoCAD VBA编制了处理软件自动生成用地类别及面积。经某项目实际应用证明,该方法具有易于掌握、结果可靠、高效快捷的特点,可推广应用。 相似文献
982.
983.
介绍了中泰化学米东工业园自然循环离子膜电解制碱装置,在二次盐水工序树脂塔再生及32%碱浓缩成片碱过程中.废水综合利用措施。 相似文献
984.
库岸安置点受地质环境条件制约,使建筑场地设计中存在诸多不利因素。本文对库岸垫高安置点在地形地貌、地下水位变化、建筑结构和专业交叉方面的特点进行了分析,并分阶段对上述不利因素给出了应对措施和建议。 相似文献
985.
986.
987.
Some of the limits on fuel cell development include the issues of hydrogen availability and storage. Methanol has many advantages as an alternative fuel for fuel cells but depending on the anode composition, the formation of carbon may be a problem. In this paper, the direct utilization of methanol in solid oxide fuel cells with impregnated Ni/YSZ and Ni-Zr0.35Ce0.65O2−δ (ZDC)/YSZ anodes was investigated at 1073 K. Performance and stability of these anodes, as measured by steady-state polarization and electrochemical impedance spectroscopy, were improved by the presence of ZDC; although, the deposition of carbon, as detected by scanning electron microscopy and temperature-programmed oxidation analysis, was not entirely avoided. The impact of the carbon, however, was different depending on the anode. That is, carbon formation caused the delamination of impregnated Ni/YSZ anodes, while the structural integrity of Ni-ZDC/YSZ anodes was maintained and the cell performance was not negatively impacted. Increasing the fuel utilization decreased coking, as predicted by equilibrium calculations. 相似文献
988.
Woods Douglas W.; Conelea Christine A.; Himle Michael B. 《Canadian Metallurgical Quarterly》2010,41(6):518
The current article describes the phenomenology and empirically supported treatments for Tourette's disorder (TD) and presents data on treatment utilization from two separate national surveys of adults with TD (N = 672) and parents of children with TD (N = 740). Despite a wealth of empirical evidence demonstrating its effectiveness, results suggest that most people with TD do not receive behavior therapy for the condition. Reasons for this include a lack of information about the disorder among consumers and providers, a shortage of providers trained in the treatment, and concern about possible negative effects of behavioral treatment. The article concludes with a discussion about dissemination efforts aimed at making behavior therapy more widely available to children and adults with chronic tics and a review of beliefs about the negative effects of behavior therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
989.
Detection and mapping of long-term land degradation using local net production scaling: Application to Zimbabwe 总被引:3,自引:0,他引:3
Degradation of vegetation and soils in drylands, sometimes called desertification, is thought to be a serious threat to the sustainability of human habitation, but maps of the extent and severity of degradation at country and global scales do not exist. Degraded land, by definition, has suffered a change relative to its previous condition set by its climate, soil properties, topography and expectations of land managers. The local net production scaling (LNS) method, tested here in Zimbabwe, estimates potential production in homogeneous land capability classes and models the actual productivity using remotely-sensed observations. The difference between the potential and actual productivities provides a map of the location and severity of degradation. Six years of 250 m resolution MODIS data were used to estimate actual net production in Zimbabwe and calculate the LNS using three land capability classifications. The LNS maps agreed with known areas of degradation and with an independent degradation map. The principal source of error arose because of inhomogeneity of some land capability classes caused by, for example, the inclusion of local hot-spots of high production and differences in precipitation caused by local topography. Agriculture and other management can affect the degradation estimates and careful inspection of the LNS maps is essential to verify and identify the local causes of degradation. The Zimbabwe study found that approximately 16% of the country was at its potential production and the total loss in productivity due to degradation was estimated to be 17.6 Tg Cyr− 1, that is 13% of the entire national potential. Since the locations of degraded land were unrelated to natural environmental factors such as rainfall and soils, it is clear that the degradation has been caused by human land use, concentrated in the heavily-utilized, communal areas. 相似文献
990.
论述了我国发展节能省地型住宅的必要性,针对在节能省地型住宅的推广过程中存在的问题,给出了一些行之有效的措施,最后指出通过有关各方的通力协作,定能使节能省地型住宅在我国普及,使我国住宅产业进一步走向成熟。 相似文献