全文获取类型
收费全文 | 542248篇 |
免费 | 55330篇 |
国内免费 | 23748篇 |
专业分类
电工技术 | 34266篇 |
技术理论 | 58篇 |
综合类 | 35867篇 |
化学工业 | 94668篇 |
金属工艺 | 29643篇 |
机械仪表 | 34309篇 |
建筑科学 | 42844篇 |
矿业工程 | 16851篇 |
能源动力 | 15759篇 |
轻工业 | 39484篇 |
水利工程 | 10198篇 |
石油天然气 | 31169篇 |
武器工业 | 4863篇 |
无线电 | 63474篇 |
一般工业技术 | 65059篇 |
冶金工业 | 25392篇 |
原子能技术 | 5614篇 |
自动化技术 | 71808篇 |
出版年
2024年 | 1814篇 |
2023年 | 7504篇 |
2022年 | 14060篇 |
2021年 | 20574篇 |
2020年 | 16509篇 |
2019年 | 14630篇 |
2018年 | 16422篇 |
2017年 | 18816篇 |
2016年 | 17428篇 |
2015年 | 23300篇 |
2014年 | 29156篇 |
2013年 | 35174篇 |
2012年 | 36457篇 |
2011年 | 38996篇 |
2010年 | 35238篇 |
2009年 | 33538篇 |
2008年 | 32658篇 |
2007年 | 31292篇 |
2006年 | 30895篇 |
2005年 | 26233篇 |
2004年 | 17715篇 |
2003年 | 15588篇 |
2002年 | 14577篇 |
2001年 | 13239篇 |
2000年 | 12654篇 |
1999年 | 12780篇 |
1998年 | 9827篇 |
1997年 | 8225篇 |
1996年 | 7681篇 |
1995年 | 6427篇 |
1994年 | 5285篇 |
1993年 | 3698篇 |
1992年 | 2983篇 |
1991年 | 2287篇 |
1990年 | 1765篇 |
1989年 | 1462篇 |
1988年 | 1172篇 |
1987年 | 763篇 |
1986年 | 604篇 |
1985年 | 368篇 |
1984年 | 276篇 |
1983年 | 224篇 |
1982年 | 226篇 |
1981年 | 169篇 |
1980年 | 172篇 |
1979年 | 95篇 |
1978年 | 43篇 |
1977年 | 47篇 |
1976年 | 65篇 |
1975年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
201.
Cerebral microbleeds and cognitive decline in a hemodialysis patient: Case report and review of literature
下载免费PDF全文
![点击此处可从《Hemodialysis international. International Symposium on Home Hemodialysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lin Li Mark Fisher Wei‐Ling Lau Hamid Moradi Alexander Cheung Gaby Thai Jason Handwerker Kamyar Kalantar‐Zadeh 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(3):E1-E7
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients. 相似文献
202.
介绍机械制造厂燃煤锅炉的烟尘特点,分析滤料失效的原因,提出一套针对该工况的滤料解决方案。介绍针对复杂工况条件所选用的纤维种类以及复合面层原料成分配比的确定,最终选用针刺工艺加工并对该新产品的基本性能进行了测试分析。 相似文献
204.
Adaptive backstepping repetitive learning control design for nonlinear discrete‐time systems with periodic uncertainties
下载免费PDF全文
![点击此处可从《International Journal of Adaptive Control and Signal Processing》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Qiao Zhu Jian‐Xin Xu Shiping Yang Guang‐Da Hu 《International Journal of Adaptive Control and Signal Processing》2015,29(4):524-535
This paper addresses a tracking problem for uncertain nonlinear discrete‐time systems in which the uncertainties, including parametric uncertainty and external disturbance, are periodic with known periodicity. Repetitive learning control (RLC) is an effective tool to deal with periodic unknown components. By using the backstepping procedures, an adaptive RLC law with periodic parameter estimation is designed. The overparameterization problem is overcome by postponing the parameter estimation to the last backstepping step, which could not be easily solved in robust adaptive control. It is shown that the proposed adaptive RLC law without overparameterization can guarantee the perfect tracking and boundedness of the states of the whole closed‐loop systems in presence of periodic uncertainties. In addition, the effectiveness of the developed controller is demonstrated by an implementation example on a single‐link flexible‐joint robot. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
205.
206.
207.
Mineralization of Para-Chlorobenzoic Acid in Water by Cobalt-Incorporated MCM-41 Catalyzed Ozonation
Cobalt-incorporated MCM-41(Co-MCM-41) was used as a heterogeneous catalyst for the ozonation of para-chlorobenzoic acid (p-CBA) in aqueous solution. Cobalt oxide supported on MCM-41(Co/MCM-41) was synthesized for comparison. Their textural properties were elucidated by various characterization techniques to understand the relationship between surface texture and catalytic activity. TOC removal at 60 min reached 91% with Co-MCM-41, 83% with Co/MCM-41 and only 52% with ozone alone, respectively. Observations from diffuse reflection spectroscopy demonstrated that different metal phases were formed in these cobalt-modified molecular sieves samples. Radical scavenger experiments indicated the formation of hydroxyl radicals that were responsible for the effective degradation of p-CBA. An integrated approach to the catalytic mechanism was proposed by considering the variation of pH in the course of ozonation as well as its subsequent influence on the dissociation of targeted compounds and surface charge of the catalyst. In the reusability experiments, the reused Co-MCM-41 was able to regain the same catalytic capability as the fresh one within 5 cycles. X-ray photoelectron spectroscopy results indicated that a part of Co2+ was oxidized to Co3+ after oxidation reaction. 相似文献
208.
Wan‐Xia Wu 《Polymer International》2019,68(11):1848-1855
A series of novel aliphatic poly(β‐thioether ester)s with various methylene group contents were prepared by direct lipase‐catalyzed polycondensation of the monomer with an acid‐labile β‐thiopropionate group. The polycondensation reaction using immobilized lipase B from Candida antarctica was carried out in diphenyl ether at 90 °C. Poly(β‐thioether ester)s with high molecular weights of 20 500–57 000 Da and narrow polydispersities in the range 1.40–1.48 were obtained. Thermogravimetric analysis, differential scanning calorimetry and wide‐angle X‐ray diffraction were used to investigate the thermal properties and crystal structures of these polyesters. All the poly(β‐thioether ester)s were semicrystalline polymers and thermally stable up to at least 200 °C. In vitro degradation studies showed that they can rapidly degrade under acidic conditions by the hydrolysis of the β‐thiopropionate groups, suggesting their potential as acid‐degradable polymeric materials. © 2019 Society of Chemical Industry 相似文献
209.
微型步进马达线圈组卷线上下料基本靠手动作业,效率低下,同时因工人技术水平的不同造成产品品质不稳定的问题多发.为此专门设计了微型步进马达线圈组自动卷线及上下料设备.通过结合现阶段的先进工业技术,采用振动盘分离区分进料,多机构并联三菱PLC及威纶人机界面触摸屏研发了此微型步进马达线圈组自动上下料及卷线设备.通过该设备实现了微型步进马达因工人不足导致产能减少和品质多发问题,减少企业成本,提升产品品质. 相似文献
210.