全文获取类型
收费全文 | 180987篇 |
免费 | 2708篇 |
国内免费 | 711篇 |
专业分类
电工技术 | 3337篇 |
综合类 | 104篇 |
化学工业 | 29160篇 |
金属工艺 | 7823篇 |
机械仪表 | 5228篇 |
建筑科学 | 4540篇 |
矿业工程 | 882篇 |
能源动力 | 4851篇 |
轻工业 | 17018篇 |
水利工程 | 1739篇 |
石油天然气 | 3151篇 |
武器工业 | 2篇 |
无线电 | 20180篇 |
一般工业技术 | 34043篇 |
冶金工业 | 33295篇 |
原子能技术 | 4318篇 |
自动化技术 | 14735篇 |
出版年
2021年 | 1502篇 |
2019年 | 1390篇 |
2018年 | 2274篇 |
2017年 | 2244篇 |
2016年 | 2372篇 |
2015年 | 1725篇 |
2014年 | 2951篇 |
2013年 | 8171篇 |
2012年 | 4877篇 |
2011年 | 6728篇 |
2010年 | 5282篇 |
2009年 | 6125篇 |
2008年 | 6065篇 |
2007年 | 6045篇 |
2006年 | 5155篇 |
2005年 | 4807篇 |
2004年 | 4578篇 |
2003年 | 4220篇 |
2002年 | 4191篇 |
2001年 | 4166篇 |
2000年 | 3970篇 |
1999年 | 4103篇 |
1998年 | 10442篇 |
1997年 | 7427篇 |
1996年 | 5687篇 |
1995年 | 4307篇 |
1994年 | 3646篇 |
1993年 | 3592篇 |
1992年 | 2620篇 |
1991年 | 2559篇 |
1990年 | 2434篇 |
1989年 | 2462篇 |
1988年 | 2389篇 |
1987年 | 2145篇 |
1986年 | 2082篇 |
1985年 | 2381篇 |
1984年 | 2200篇 |
1983年 | 2018篇 |
1982年 | 1892篇 |
1981年 | 1951篇 |
1980年 | 1805篇 |
1979年 | 1818篇 |
1978年 | 1778篇 |
1977年 | 2112篇 |
1976年 | 2691篇 |
1975年 | 1559篇 |
1974年 | 1552篇 |
1973年 | 1610篇 |
1972年 | 1351篇 |
1971年 | 1262篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Pedro Lavrador Marco R. Esteves Vítor M. Gaspar João F. Mano 《Advanced functional materials》2021,31(8):2005941
The complex tissue-specific physiology that is orchestrated from the nano- to the macroscale, in conjugation with the dynamic biophysical/biochemical stimuli underlying biological processes, has inspired the design of sophisticated hydrogels and nanoparticle systems exhibiting stimuli-responsive features. Recently, hydrogels and nanoparticles have been combined in advanced nanocomposite hybrid platforms expanding their range of biomedical applications. The ease and flexibility of attaining modular nanocomposite hydrogel constructs by selecting different classes of nanomaterials/hydrogels, or tuning nanoparticle-hydrogel physicochemical interactions widely expands the range of attainable properties to levels beyond those of traditional platforms. This review showcases the intrinsic ability of hybrid constructs to react to external or internal/physiological stimuli in the scope of developing sophisticated and intelligent systems with application-oriented features. Moreover, nanoparticle-hydrogel platforms are overviewed in the context of encoding stimuli-responsive cascades that recapitulate signaling interplays present in native biosystems. Collectively, recent breakthroughs in the design of stimuli-responsive nanocomposite hydrogels improve their potential for operating as advanced systems in different biomedical applications that benefit from tailored single or multi-responsiveness. 相似文献
72.
Lisichkin S. E. Rubin O. D. Pashchenko F. A. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(3):373-379
Power Technology and Engineering - The experimental results on retaining reinforced-concrete walls reinforced with anchor ties and carbon composite materials on the face side of hydraulic... 相似文献
73.
74.
Radiochemistry - Azathioprine, an antitumor agent, was labeled with 99mTc using stannous chloride dihydrate as a reducing agent. Factors such as the amounts of the reducing agent and substrate, pH,... 相似文献
75.
76.
A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process. 相似文献
77.
Technical Physics Letters - Using the method of DC magnetron sputtering, nonstructured amorphous metal coatings of Zr75Pd25 composition were obtained with an average deposition rate of 1.3 nm/s at... 相似文献
78.
This study aims to evaluate the tribological behaviour of 3Y-TZP/Ta (20 vol%) ceramic-metal composites and 3Y-TZP monolithic ceramic prepared by spark plasma sintering (SPS) against ultrahigh molecular weight polyethylene (UHMWPE). According to the results of pin (UHMWPE)-on-flat wear test under dry conditions, the UHMWPE – 3Y-TZP/Ta system exhibited lower volume loss and friction coefficient than the UHMWPE – monolithic ceramic combination due to the presence of an autolubricating layer that provides sufficient lubrication for reducing the friction. Owing to the lubrication of the liquid media, under wet conditions obtained using simulated body fluid (SBF), similar behaviour is observed in both cases. Additionally, the ceramic and biocomposite materials were subjected to a low temperature degradation (LTD) process (often referred to as “ageing”) to evaluate the changes in the tribological behaviour after this treatment. In this particular case, the wear properties of the UHMWPE-biocomposite system were found to be less influenced by ageing in contrast to the case of the UHMWPE-zirconia monolithic material. In addition to their exceptional mechanical performance, 3Y-TZP/Ta composites also showed high resistance to low temperature degradation and good tribological properties, making them promising candidates for biomedical applications, especially for orthopaedic implants. 相似文献
79.
Yachao Dong Christos T. Maravelias Norman F. Jerome 《Optimization and Engineering》2018,19(4):937-976
We study a maritime inventory routing problem, in which shipments between production and consumption nodes are carried out by a fleet of vessels. The vessels have specific capacities and can be chartered under different agreements. The inventory levels of all consumption nodes and some production nodes should be maintained within specified bounds; for the remaining production nodes, orders should be picked up within pre-defined time windows. We propose a discrete-time mixed-integer programming model. In the face of new information and uncertainty, this optimization model has to be re-solved, as the horizon is rolled forward. We discuss how to account for different sources of uncertainty. We present a rolling-horizon reoptimization framework that allows us to study different policies that impact the quality of the implemented solution, so we can identify the optimal set of policies. 相似文献