全文获取类型
收费全文 | 2545篇 |
免费 | 442篇 |
国内免费 | 112篇 |
学科分类
工业技术 | 3099篇 |
出版年
2024年 | 14篇 |
2023年 | 64篇 |
2022年 | 101篇 |
2021年 | 136篇 |
2020年 | 135篇 |
2019年 | 93篇 |
2018年 | 114篇 |
2017年 | 152篇 |
2016年 | 123篇 |
2015年 | 172篇 |
2014年 | 209篇 |
2013年 | 201篇 |
2012年 | 225篇 |
2011年 | 190篇 |
2010年 | 119篇 |
2009年 | 100篇 |
2008年 | 111篇 |
2007年 | 138篇 |
2006年 | 121篇 |
2005年 | 105篇 |
2004年 | 93篇 |
2003年 | 69篇 |
2002年 | 67篇 |
2001年 | 57篇 |
2000年 | 40篇 |
1999年 | 39篇 |
1998年 | 28篇 |
1997年 | 13篇 |
1996年 | 22篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 17篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有3099条查询结果,搜索用时 15 毫秒
1.
选煤厂采用模块式钢结构作为设备支架,受设备使用及养护不当造成结构构件严重腐蚀,构件截面削弱,导致结构产生过大振动,通过对结构各层振动响应测试,得到各测点水平向及竖直向振动速度幅值。经分析得出腐蚀后对结构整体刚度影响程度,为后期采取措施及安全生产提供依据。 相似文献
2.
3.
某出口型号交流电力机车牵引控制系统要求变流器控制逻辑具备接触器控制、牵引系统数据交互、变流器故障保护、变流器启动自检等功能。针对以上功能,基于MATLAB中的Simulink/Stateflow可视化编程工具进行牵引控制模型的搭建,遵循模块化编程理念,采用较少的程序代码编写实现复杂的逻辑控制模型,生成逻辑清晰的控制功能流程图,进行半实物仿真测试,增强控制模型的可靠性。通过该变流器产品型式试验检验,验证变流器控制逻辑的功能可以满足控制系统的需求。 相似文献
4.
为进一步分析含柔性直流输电(MMC-HVDC)的交直流混合输电系统的故障特征,基于交直流混合输电系统和模块化多电平换流器(MMC)的拓扑结构,推导了MMC的数学模型,研究了直流系统双极短路的故障机理和故障特征,针对含MMC-HVDC的交直流混合输电系统的双极短路故障,设计了限流电路及闭锁换流站与交流断路器跳闸相结合的故障保护方案。以厦门市柔性直流输电系统为例,在PSCAD/EMTDC中搭建了交直流混合系统,并对保护方案进行了仿真验证。结果表明,提出的保护策略能有效地降低故障电流,提高系统稳定性。 相似文献
5.
6.
Modular Self‐Assembling Peptide Platform with a Tunable Thermoresponsiveness via a Single Amino Acid Substitution 下载免费PDF全文
《Advanced functional materials》2018,28(35)
The introduction of a stimulus‐responsive property is an effective way to increase the applicability of functional materials in the field of nanobiotechnology. Herein, a peptide platform is devised for constructing elastin‐like peptide amphiphiles (ELPAs) that exhibit a temperature‐responsiveness that can be easily tuned via a single N‐terminal amino acid substitution at the final step of peptide synthesis. Due to the modular property of peptides, the platform based on a miniaturized elastin‐like peptide (MELP) can be conjugated with various bioactive peptide sequences in diverse macromolecular topologies. First, the MELP platform is coupled with a short linear RGD peptide. The ELPAs of the peptide conjugates exhibit rapid aggregation (coacervation) and retard disaggregation in response to heating and cooling, respectively. Second, the platform is grafted with an α‐helical guest peptide in a lariat‐type structure, which forms ELPAs that undergo faster disassembly than the ELPAs without the guest peptide in response to temperature increases. Interestingly, the critical temperatures for the thermoresponsive behaviors are commonly dependent on the hydrophobic and aromatic properties of the N‐terminal amino acid residues. These results suggest that this peptide platform possesses great potential for use in the development of smart materials in wide‐ranging applications related to temperature change. 相似文献
7.
A numerical investigation of the different arrangements of porous media in a combustor with annular heat recirculation is conducted.The effect of annular heat recirculation and porous block arrangement on the characteristics of combustion wave propagation is numerically studied.Results show that power input,heat capacity of porous matrix,arrangement of porous blocks,and annular heat recirculation are major factors that influence the propagation of combustion wave.The overall temperature of ceramic porous burner is higher than that of ceramic-metal type burner due to the lower heat storage capacity of the former,especially for the temperature downstream.The flame temperature is higher upstream and lower downstream with metal foams in the annulus than that without metal foams.The flame temperature of uniformity type burner is more uniform than that of gradually-varied and modular type burners.The flame front moves more slowly with metal foams in the annulus than that without metal foams due to the better preheating effect of metal foams.The flame position moves downstream,and the flame temperature gradually decreases and is eventually extinguished due to the low preheating temperature. 相似文献
8.
9.
Stakeholders remain skeptical in adopting modular integrated construction (MiC) because of the associated risks and uncertainties, although its benefits have been extensively documented. The unique business model of MiC nurtures several risks and uncertainties different from those of the conventional construction approach. Despite the growing attention on MiC with its market expansion, no systematic evaluation is in place to monitor its risks research progress. Accordingly, this research reviewed published literature addressing the risks associated with MiC from 1992 to 2019. Analysis reveals that the research publications on risks of MiC witnessed a steady growth, with considerable progress occurring in the last decade. Result implies that the risk of MiC has gained extra attention in the construction engineering and management domain in recent times. Existing empirical studies have focused heavily on perceived implementation risks, supply chain risks, schedule risks, investment risks, structural risks, ergonomic risks, and MiC risk management strategies, which indicate that MiC is associated with a host of risk events. The research further identified the critical risk events (CREs) in the application of MiC based on frequency of occurrence. The identified CREs contributes to the checklists of risk events in the implementation of offsite construction (OSC). The latter may be useful in risk planning, especially where the MiC is less developed, and fewer or no bespoke risk assessment exists. Research gaps in existing studies are highlighted in this research, and areas for further studies are then proposed. Thus, it makes a useful contribution to the scholarly literature on the risk of OSC and may prove useful to offsite construction researchers, industry practitioners, and project managers. 相似文献
10.
Han Bit Lee Young Won Kim Sang Hoon Kim Suk Hee Park Joon‐Phil Choi Clodualdo Aranas Jr. 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(33)
A modular solder system with hierarchical morphology and micro/nanofeatures in which solder nanoparticles are distributed on the surface of template micropowders is reported. A core–shell structure of subsidiary nanostructures, which improved the intended properties of the modular solder is also presented. In addition, polymer additives can be used not only as an adhesive (like epoxy resin) but also to impart other functions. By combining all of these, it is determined that the modular solder system is able to increase reflowability on a heat‐sensitive plastic substrate, oxidation resistance, and electrical conductivity. In this respect, the system could be readily modified by changing the structure and composition of each constituent and adopting backward compatibility with which the knowledge and information attained from a previously designed solder can offer feedback toward further improving the properties of a newly designed one. In practice, In–Sn–Bi nanoparticles engineered on the surface of Sn–Zn micropowders result in pronounced reflowing on a flexible Au‐coated polyethylene terephthalate (PET) substrate even at the low temperature of 110 °C. Depending on their respective concentrations, the incorporation of CuO@CeO2 nanostructures and poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymers increases oxidation resistance and electrical conductivity of the modular solder. 相似文献