全文获取类型
收费全文 | 436728篇 |
免费 | 6696篇 |
国内免费 | 1862篇 |
专业分类
电工技术 | 8150篇 |
综合类 | 852篇 |
化学工业 | 63019篇 |
金属工艺 | 15033篇 |
机械仪表 | 12345篇 |
建筑科学 | 10906篇 |
矿业工程 | 1416篇 |
能源动力 | 11571篇 |
轻工业 | 41320篇 |
水利工程 | 3744篇 |
石油天然气 | 4770篇 |
武器工业 | 39篇 |
无线电 | 57641篇 |
一般工业技术 | 79560篇 |
冶金工业 | 90202篇 |
原子能技术 | 6536篇 |
自动化技术 | 38182篇 |
出版年
2021年 | 3275篇 |
2020年 | 2380篇 |
2019年 | 3058篇 |
2018年 | 4700篇 |
2017年 | 4706篇 |
2016年 | 5084篇 |
2015年 | 3754篇 |
2014年 | 6275篇 |
2013年 | 19357篇 |
2012年 | 10988篇 |
2011年 | 15375篇 |
2010年 | 12049篇 |
2009年 | 13837篇 |
2008年 | 14548篇 |
2007年 | 14614篇 |
2006年 | 13384篇 |
2005年 | 12335篇 |
2004年 | 12036篇 |
2003年 | 12104篇 |
2002年 | 11660篇 |
2001年 | 12297篇 |
2000年 | 10864篇 |
1999年 | 11767篇 |
1998年 | 31090篇 |
1997年 | 21025篇 |
1996年 | 15977篇 |
1995年 | 11868篇 |
1994年 | 10282篇 |
1993年 | 10191篇 |
1992年 | 7004篇 |
1991年 | 6654篇 |
1990年 | 6381篇 |
1989年 | 6109篇 |
1988年 | 5806篇 |
1987年 | 4655篇 |
1986年 | 4640篇 |
1985年 | 5547篇 |
1984年 | 4900篇 |
1983年 | 4428篇 |
1982年 | 4088篇 |
1981年 | 4268篇 |
1980年 | 3873篇 |
1979年 | 3565篇 |
1978年 | 3393篇 |
1977年 | 4102篇 |
1976年 | 5389篇 |
1975年 | 2884篇 |
1974年 | 2722篇 |
1973年 | 2777篇 |
1972年 | 2173篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Kozhitov L. V. Kiselev B. G. Raykova T. B. Popkova A. V. Kostishin V. G. Muratov D. G. Yakushko E. V. Kosushkin V. G. Bebenin V. G. 《Russian Microelectronics》2019,48(8):599-612
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical... 相似文献
43.
44.
Geetha R. Madhusudhan V. Padmavathy T. Lallithasree A. 《Wireless Personal Communications》2019,108(3):1957-1976
Wireless Personal Communications - The majority of security systems for wireless sensor networks are based on symmetric encryption. The main open issue for these approaches concerns the... 相似文献
45.
46.
Valence M. K. Ndesendo Yahya E. Choonara Leith C. R. Meyer Pradeep Kumar Lomas K. Tomar Charu Tyagi 《Drug development and industrial pharmacy》2015,41(8):1274-1287
Context and objective: The aim of this study was to develop, characterize and evaluate a mucoadhesive caplet resulting from a polymeric blend (polymeric caplet) for intravaginal anti-HIV-1 delivery.Materials and methods: Poly(lactic-co-glycolic) acid, ethylcellulose, poly(vinylalcohol), polyacrylic acid and modified polyamide 6, 10 polymers were blended and compressed to a caplet-shaped device, with and without two model drugs 3′-azido-3′-deoxythymidine (AZT) and polystyrene sulfonate (PSS). Thermal analysis, infrared spectroscopy and microscopic analysis were carried out on the caplets employing temperature-modulated DSC (TMDSC), Fourier transform infra-red (FTIR) spectrometer and scanning electron microscope, respectively. In vitro and in vivo drug release analyses as well as the histopathological toxicity studies were carried out on the drug-loaded caplets. Furthermore, molecular mechanics (MM) simulations were carried out on the drug-loaded caplets to corroborate the experimental findings.Results and discussion: There was a big deviation between the Tg of the polymeric caplet from the Tg's of the constituent polymers indicating a strong interaction between constituent polymers. FTIR spectroscopy confirmed the presence of specific ionic and non-ionic interactions within the caplet. A controlled near zero-order drug release was obtained for AZT (20 d) and PSS (28 d). In vivo results, i.e. the drug concentration in plasma ranged between 0.012–0.332?mg/mL and 0.009–0.256?mg/mL for AZT and PSS over 1–28 d.Conclusion: The obtained results, which were corroborated by MM simulations, attested that the developed system has the potential for effective delivery of anti-HIV-agents. 相似文献
47.
Load testing of applications is an important and costly activity for software provider companies. Classical solutions are very difficult to set up statically, and their cost is prohibitive in terms of both human and hardware resources. Virtualized cloud computing platforms provide new opportunities for stressing an application's scalability, by providing a large range of flexible and less expensive (pay‐per‐use model) computation units. On the basis of these advantages, load testing solutions could be provided on demand in the cloud. This paper describes a Benchmark‐as‐a‐Service solution that automatically scales the load injection platform and facilitates its setup according to load profiles. Our approach is based on: (i) virtualization of the benchmarking platform to create self‐scaling injectors; (ii) online calibration to characterize the injector's capacity and impact on the benched application; and (iii) a provisioning solution to appropriately scale the load injection platform ahead of time. We also report experiments on a benchmark illustrating the benefits of this system in terms of cost and resource reductions. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
48.
Lecture capture with real‐time rearrangement of visual elements: impact on student performance 下载免费PDF全文
The primary goal of this study is to create and test a lecture‐capture system that can rearrange visual elements while recording is still taking place, in such a way that student performance can be positively influenced. The system we have devised is capable of integrating and rearranging multimedia sources, including learning content, the instructor and students' images, into lecture videos that are embedded in a website for students to review after school. The present study employed a two‐group experimental design, with 153 participants (145 females and 8 males) making up an experimental group in which lecture courses were recorded using the new lecture‐capture system, and 149 participants (140 females and 9 males) forming a control group whose lectures were recorded by traditional means. All participants were in the freshman college and studying Introduction to Computer and Information Science in one of six classes, and were randomly assigned to one of the two groups. The participants' midterm examination and final examination scores were collected as indicators of their academic performance, with their mathematics entrance scores used as a pre‐test. The findings obtained from analysis of covariance (ANCOVA) suggest that appropriate rearrangement of visual elements in lecture videos can significantly impact students' learning performance. 相似文献
49.
A. M. Mirzabaev V. P. Kanonerov T. A. Makhkamov O. R. Sytdykov Sh. M. Mirzabekov 《Applied Solar Energy》2018,54(3):224-226
The data on the use of solar photovoltaic plants (PVPs) for providing a reliable and guaranteed power supply to telecommunication systems and cellular communication systems in the conditions prevalent in Uzbekistan are given. The research-based structures developed by OOO MIR SOLAR and the selection of PVP elements ensuring their reliable operation are described. The main influencing factors are discussed, and the use of effective combinations of different types of panels (from monocrystalline and polycrystalline silicon) and a specially developed controller are considered. 相似文献
50.
C. G. Prosgolitis S. G. Lambrakos A. D. Zervaki 《Journal of Materials Engineering and Performance》2018,27(10):5102-5113
This work presents simulation of microstructure evolution in the nugget zone (NZ) of a AZ31-Mg-alloy friction stir weld. The process parameters (tool geometrical characteristics, rotational speed, travel speed, applied load) have been correlated with the resulting microstructural features in the NZ of the weld (grain size and population) with the aid of the MICRESS software, which provides the ability to simulate both nucleation and grain growth during dynamic recrystallization phenomena evolving in the NZ during the weld thermal cycle. The input parameters of the developed model include the tool geometry, the welding conditions as well as the recrystallization energy, the grain boundary mobility and specific material properties. NZ microstructure obtained by simulation shows good agreement with experimental measurements for both grain population and size. 相似文献