全文获取类型
收费全文 | 21934篇 |
免费 | 1438篇 |
国内免费 | 872篇 |
专业分类
电工技术 | 1364篇 |
综合类 | 1394篇 |
化学工业 | 1225篇 |
金属工艺 | 2571篇 |
机械仪表 | 1801篇 |
建筑科学 | 1725篇 |
矿业工程 | 473篇 |
能源动力 | 354篇 |
轻工业 | 1260篇 |
水利工程 | 234篇 |
石油天然气 | 1853篇 |
武器工业 | 269篇 |
无线电 | 1952篇 |
一般工业技术 | 2841篇 |
冶金工业 | 735篇 |
原子能技术 | 155篇 |
自动化技术 | 4038篇 |
出版年
2024年 | 24篇 |
2023年 | 176篇 |
2022年 | 265篇 |
2021年 | 421篇 |
2020年 | 422篇 |
2019年 | 381篇 |
2018年 | 393篇 |
2017年 | 564篇 |
2016年 | 663篇 |
2015年 | 876篇 |
2014年 | 1286篇 |
2013年 | 1208篇 |
2012年 | 1508篇 |
2011年 | 1630篇 |
2010年 | 1378篇 |
2009年 | 1350篇 |
2008年 | 1359篇 |
2007年 | 1497篇 |
2006年 | 1357篇 |
2005年 | 1209篇 |
2004年 | 992篇 |
2003年 | 887篇 |
2002年 | 758篇 |
2001年 | 672篇 |
2000年 | 524篇 |
1999年 | 449篇 |
1998年 | 374篇 |
1997年 | 268篇 |
1996年 | 248篇 |
1995年 | 210篇 |
1994年 | 160篇 |
1993年 | 120篇 |
1992年 | 106篇 |
1991年 | 89篇 |
1990年 | 74篇 |
1989年 | 47篇 |
1988年 | 36篇 |
1987年 | 19篇 |
1986年 | 15篇 |
1985年 | 30篇 |
1984年 | 24篇 |
1983年 | 30篇 |
1982年 | 30篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1965年 | 18篇 |
1962年 | 7篇 |
1957年 | 5篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Three different ABA‐type triblock copolymers each containing biodegradable aliphatic polycarbonate as the middle block and poly(l ‐lactide) as the outer blocks were synthesized and the influence of the methylene chain length of the aliphatic polycarbonate middle block on various properties of the triblock copolymers was evaluated. Differential scanning calorimetry and wide‐angle X‐ray diffraction studies revealed that the incorporation of the outer blocks reduced the crystallinity of the middle aliphatic polycarbonate block. Variation of methylene chain length of the middle block led to a change in morphology from spherical to cylindrical as evidenced from atomic force microscopy studies. In addition, the mechanical properties of the block copolymers showed semi‐ductile to quasi‐brittle behaviour depending upon the composition of the middle block which was also confirmed using scanning electron microscopy. Dynamic mechanical analysis of the triblock copolymers indicated that storage modulus increased with a decrease in methylene chain length. © 2018 Society of Chemical Industry 相似文献
82.
83.
84.
Victoria R.C. Sieck Fletcher G.W. Christensen 《Quality and Reliability Engineering International》2021,37(7):3018-3033
When developing a product, it is important to consider product performance from a user perspective. This type of evaluation can be done through operational testing—assessing the ability of representative users to satisfactorily accomplish tasks with the product in operationally representative environments. This process can be expensive and time-consuming, but is critical to understanding whether the product can adequately do the job for which it was designed. We show how an existing design of experiments (DOEs) process for operational testing can be leveraged to construct a Bayesian adaptive design. This design, nested within the larger design created by the DOE process, allows interim analyses to stop testing early for success or futility. Representative simulations are presented to demonstrate how these interim analyses can be used in an operational test setting, and reductions in necessary test events are shown. The application of Bayesian-adaptive design methods will allow future operational testing to be conducted in less time and at less expense, on average, without compromising the ability of the existing process to verify the product meets the user's needs. 相似文献
85.
As blockchain technology is gaining popularity in industry and society, solutions for Verification and Validation (V&V) of blockchain-based software applications (BC-Apps) have started gaining equal attention. To ensure that BC-Apps are properly developed before deployment, it is paramount to apply systematic V&V to verify their functional and non-functional requirements. While existing research aims at addressing the challenges of engineering BC-Apps by providing testing techniques and tools, blockchain-based software development is still an emerging research discipline, and therefore, best practices and tools for the V&V of BC-Apps are not yet sufficiently developed. In this paper, we provide a comprehensive survey on V&V solutions for BC-Apps. Specifically, using a layered approach, we synthesize V&V tools and techniques addressing different components at various layers of the BC-App stack, as well as across the whole stack. Next, we provide a discussion on the challenges associated with BC-App V&V, and summarize a set of future research directions based on the challenges and gaps identified in existing research work. Our study aims to highlight the importance of BC-App V&V and pave the way for a disciplined, testable, and verifiable BC development. 相似文献
86.
87.
Carbon Fiber Reinforced Polymers (CFRPs) have been increasingly employed for structural strengthening, and are attached to structures using bonding adhesives. The aim of this work is to characterize defects in the bond between CFRP and concrete (after they are located by pulse infrared thermography), and assign the defects a “numerical value” (ranging from 0 for a complete air–gap to 1 for a fully glued bond). Quantitative characterization is performed by measuring the thermal impedance, and then identifying the thermophysical parameters of the system through fitting the measured impedance to a theoretical model. An inversion procedure is carried out to estimate the unknown parameters, without prior knowledge of sample properties. In particular, it is possible to estimate more accurately both the amount of glue within a defect and the thermal contact resistance. 相似文献
89.
《Journal of the European Ceramic Society》2014,34(10):2575-2584
A new tensile strength test for ceramic rollers (cylinders) is presented, following the idea of the previously published and since that time standardized notched ball test. The specimen is prepared by cutting a long narrow notch along the symmetry plane of the roller, perpendicular to the end faces. By applying compressive forces perpendicular to the notch, tensile stresses are induced in the outer surface region of the roller opposite to the notch, mainly pointing in tangential direction with respect to the roller axis. The stress amplitude is proportional to the applied force and depends also on the test geometry and the Poisson’ ratio, which has been analyzed carefully with FE methods.Strength tests have been performed on two different qualities of commercial silicon nitride rollers of 10 mm diameter and length. According to their specification a significant difference in the strength has been obtained. 相似文献
90.