全文获取类型
收费全文 | 4916篇 |
免费 | 525篇 |
国内免费 | 210篇 |
专业分类
电工技术 | 312篇 |
技术理论 | 1篇 |
综合类 | 285篇 |
化学工业 | 974篇 |
金属工艺 | 294篇 |
机械仪表 | 258篇 |
建筑科学 | 314篇 |
矿业工程 | 95篇 |
能源动力 | 150篇 |
轻工业 | 504篇 |
水利工程 | 76篇 |
石油天然气 | 249篇 |
武器工业 | 51篇 |
无线电 | 573篇 |
一般工业技术 | 660篇 |
冶金工业 | 236篇 |
原子能技术 | 75篇 |
自动化技术 | 544篇 |
出版年
2024年 | 19篇 |
2023年 | 82篇 |
2022年 | 194篇 |
2021年 | 283篇 |
2020年 | 213篇 |
2019年 | 160篇 |
2018年 | 157篇 |
2017年 | 205篇 |
2016年 | 170篇 |
2015年 | 218篇 |
2014年 | 289篇 |
2013年 | 340篇 |
2012年 | 356篇 |
2011年 | 400篇 |
2010年 | 328篇 |
2009年 | 323篇 |
2008年 | 288篇 |
2007年 | 229篇 |
2006年 | 252篇 |
2005年 | 184篇 |
2004年 | 142篇 |
2003年 | 95篇 |
2002年 | 122篇 |
2001年 | 90篇 |
2000年 | 64篇 |
1999年 | 91篇 |
1998年 | 77篇 |
1997年 | 61篇 |
1996年 | 44篇 |
1995年 | 45篇 |
1994年 | 32篇 |
1993年 | 23篇 |
1992年 | 13篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有5651条查询结果,搜索用时 20 毫秒
31.
32.
Coating of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (PMN–PT) relaxor ferroelectrics by a sol–gel method is followed by growth of epitaxial SrRuO3 (SRO) metallic oxide electrodes on SrTiO3 (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN–PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN–PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed. 相似文献
33.
34.
Scaffold‐guided tissue engineering based on synthetic and natural occurring polymers has gained many interests in recent year. In this study, the development of a chitosan‐heparin artificial extracellular matrix (AECM) is reported. Three‐dimensional, macroporous composite AECMs composed of heparin (Hep) and chitosan (Chito) were prepared by an interpolyelectrolyte complex/lyophilization method. The Chito‐Hep composite AECMs were, respectively, crosslinked with glutaraldehyde, as well as cocrosslinked with N,N‐(3‐dimethylaminopropyl)‐N′‐ethyl carbodiimide (EDC/NHS) and N‐hydroxysuccinimide (NHS). The crosslinking reactions were examined by FT‐IR analysis. In physiological buffer solution (PBS), the EDC/NHS‐crosslinked Chito‐Hep composite AECM showed a relative lower water retention ratio than its glutaraldehyde‐crosslinked counterparts. The EDC/NHS‐crosslinked Chito‐Hep composite AECMs showed excellent biocompatibility, according to the results of the in vitro cytotoxic test. This result suggested that the EDC/NHS‐crosslinked Chito‐Hep composite AECMs might be a potential biomaterial for scaffold‐guided tissue engineering applications. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
35.
OBJECTIVE: To know the variability in the interpretation (normal/pathological) of posteroanterior view chest radiograph and the associated factors between a medical primary care community and a Gold Standard (GS) from 3 reference radiologists. DESIGN: Crossover study. SETTING: Primary care. Teaching health centers of Elche. METHODS: Interobserver percentage agreement (IPA) and Kappa statistic (K) were used to analyse the interobserver agreement (IA) between the GS and every of the participants in interpretation of 100 radiographs. Intraobserver variability was assessed with a second review. Using uni and multivariant analysis some possibly associated factors were studied. RESULTS: Overall IPA and K were 71.3% (CI 95%: 69.2-73.3) and 0.41 (CI 95%: 0.36-0.46) respectively. Time employed in radiographs reading and time passed after medicine studies finished were independently and significantly associated to higher and lower interobserver agreement results respectively, whereas recent professional experience, permanent job and age were not associated. Professional training is the variable that most explain the inter and intraobserver variability. CONCLUSIONS: Overall IA is acceptable. The IA showed by the participants trained under the MIR system is good but the IA achieved by the rest of participants is not acceptable. It is necessary a training which increase the clinical competence, as it does MIR training. 相似文献
36.
Investigation of the Microstructure of Rolled Semi—Solid Steel 总被引:3,自引:0,他引:3
In this paper,spring steel-60Si2Mn and stainless steel-1Cr18Ni9Ti were rolled one pass in semi-solid state.The microstructural evolution during rolling of the steels with different solid fraction was investigated.The experimental results showed that the manner of liquid and solid phases flowing and deforming was different.During rolling,most of solid phases remained in the center of the rolled specimens,while liquid phase flowed to the edge,which resulted in the macrosegregation of liquid and solid phases.Only the amount of solid fraction reached a certain value,were the solid phases deformed and flattened. 相似文献
37.
最优励磁控制与一般比例励磁调节具有明显的优点,它可提高系统的微动稳定性和微动态稳定功率极限,且可改善系统的动态品质。文章简要推导了最优励磁控制采用二次型目标的控制式,论述了如何利用该控制式采用最优励磁控制提高系统稳定性。 相似文献
39.
40.
针对站内25 Hz相敏轨道电路分路不良问题,通过系统分析,建立轨道电路预警模型,采用模糊模式识别方法实现轨道电路调整电压、现场温湿度以及故障次数的预警,并详细论述了轨道电路模糊模式识别模型的建立,同时给出了预警系统的实现方案;模拟实验及仿真结果表明,模糊模式识别在轨道电路分路不良预警中具有较高的准确性和应用价值,对解决轨道电路分路不良问题提供了有效的技术支持,为轨道电路日常维护和故障的及时发现处理创造了条件. 相似文献