全文获取类型
收费全文 | 206153篇 |
免费 | 6199篇 |
国内免费 | 3382篇 |
专业分类
电工技术 | 5939篇 |
技术理论 | 2篇 |
综合类 | 5740篇 |
化学工业 | 27925篇 |
金属工艺 | 14217篇 |
机械仪表 | 12516篇 |
建筑科学 | 7653篇 |
矿业工程 | 2925篇 |
能源动力 | 3615篇 |
轻工业 | 7666篇 |
水利工程 | 3217篇 |
石油天然气 | 4916篇 |
武器工业 | 379篇 |
无线电 | 22620篇 |
一般工业技术 | 41980篇 |
冶金工业 | 11809篇 |
原子能技术 | 2249篇 |
自动化技术 | 40366篇 |
出版年
2024年 | 277篇 |
2023年 | 942篇 |
2022年 | 1552篇 |
2021年 | 2276篇 |
2020年 | 1684篇 |
2019年 | 1618篇 |
2018年 | 22039篇 |
2017年 | 21943篇 |
2016年 | 14646篇 |
2015年 | 3198篇 |
2014年 | 3235篇 |
2013年 | 4116篇 |
2012年 | 8844篇 |
2011年 | 20178篇 |
2010年 | 18322篇 |
2009年 | 15253篇 |
2008年 | 15453篇 |
2007年 | 18182篇 |
2006年 | 3825篇 |
2005年 | 7705篇 |
2004年 | 5218篇 |
2003年 | 4713篇 |
2002年 | 3292篇 |
2001年 | 2071篇 |
2000年 | 2042篇 |
1999年 | 1839篇 |
1998年 | 1792篇 |
1997年 | 1403篇 |
1996年 | 1308篇 |
1995年 | 972篇 |
1994年 | 821篇 |
1993年 | 635篇 |
1992年 | 503篇 |
1991年 | 458篇 |
1990年 | 321篇 |
1989年 | 258篇 |
1988年 | 220篇 |
1987年 | 116篇 |
1986年 | 106篇 |
1968年 | 144篇 |
1967年 | 133篇 |
1966年 | 169篇 |
1965年 | 140篇 |
1964年 | 89篇 |
1960年 | 94篇 |
1958年 | 88篇 |
1957年 | 146篇 |
1956年 | 125篇 |
1955年 | 155篇 |
1954年 | 166篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
31.
As the development of cloud computing and the convenience of wireless sensor netowrks, smart devices are widely used in daily life, but the security issues of the smart devices have not been well resolved. In this paper, we present a new NTRU-type public-key cryptosystem over the binary field. Specifically, the security of our scheme relies on the computational intractability of an unbalanced sparse polynomial ratio problem (DUSPR). Through theoretical analysis, we prove the correctness of our proposed cryptosystem. Furthermore, we implement our scheme using the NTL library, and conduct a group of experiments to evaluate the capabilities and consuming time of encryption and decryption. Our experiments result demonstrates that the NTRU-type public-key cryptosystem over the binary field is relatively practical and effective. 相似文献
32.
Oxygen reduction reaction(ORR) plays a critical role in many energy conversion and storage processes.Therein, a comparative study of the electrocatalytic activity for ORR in 0.1 mol/L KOH solution was conducted using layered perovskite-like LaSr_3 Fe_3 O_(10) and LaSr3 Fe_3 O_(10)-graphene oxide(GO) composite as electrodes. Linear sweep voltammetry(LSV) results show that the LaSr3 Fe_3 O_(10)-GO hybrid exhibits higher current density, a more positive onset potential(-0.15 V vs. Hg/HgO) in comparison with LaSr_3 Fe_3 O_(10).The value of the overall transferred electrons for both catalysts implies a dominant two electron process for ORR. Both catalysts under alkalic conditions exhibit a two-step Tafel slope, suggesting a change in the reaction mechanism for ORR. The composite electrode exhibits a higher ORR current density, but inferior durability performances in relative to the LaSr_3 Fe_3 O_(10) electrode. 相似文献
33.
34.
35.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
36.
A. A. Babenko V. I. Zhuchkov L. A. Smirnov A. V. Sychev A. A. Akberdin A. S. Kim M. F. Vitushchenko A. A. Dobromilov 《Steel in Translation》2015,45(11):883-886
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite. 相似文献
37.
38.
39.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials. 相似文献
40.
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