全文获取类型
收费全文 | 70321篇 |
免费 | 7509篇 |
国内免费 | 4508篇 |
专业分类
电工技术 | 5842篇 |
技术理论 | 5篇 |
综合类 | 5680篇 |
化学工业 | 9539篇 |
金属工艺 | 4334篇 |
机械仪表 | 5159篇 |
建筑科学 | 5603篇 |
矿业工程 | 2259篇 |
能源动力 | 2071篇 |
轻工业 | 5308篇 |
水利工程 | 1998篇 |
石油天然气 | 3716篇 |
武器工业 | 987篇 |
无线电 | 8483篇 |
一般工业技术 | 6786篇 |
冶金工业 | 2777篇 |
原子能技术 | 968篇 |
自动化技术 | 10823篇 |
出版年
2024年 | 373篇 |
2023年 | 1155篇 |
2022年 | 2271篇 |
2021年 | 3132篇 |
2020年 | 2368篇 |
2019年 | 1835篇 |
2018年 | 2142篇 |
2017年 | 2449篇 |
2016年 | 2197篇 |
2015年 | 3302篇 |
2014年 | 4036篇 |
2013年 | 4691篇 |
2012年 | 5474篇 |
2011年 | 5997篇 |
2010年 | 5302篇 |
2009年 | 4916篇 |
2008年 | 5068篇 |
2007年 | 4876篇 |
2006年 | 4337篇 |
2005年 | 3505篇 |
2004年 | 2404篇 |
2003年 | 1800篇 |
2002年 | 1650篇 |
2001年 | 1482篇 |
2000年 | 1244篇 |
1999年 | 993篇 |
1998年 | 698篇 |
1997年 | 520篇 |
1996年 | 451篇 |
1995年 | 445篇 |
1994年 | 327篇 |
1993年 | 212篇 |
1992年 | 186篇 |
1991年 | 114篇 |
1990年 | 81篇 |
1989年 | 66篇 |
1988年 | 61篇 |
1987年 | 46篇 |
1986年 | 27篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 22篇 |
1979年 | 11篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1959年 | 8篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
Flocculation morphology is a new concept that investigates the morphological characteristics of colloidal particles and coagulants in water during the flocculation process, and the influence that these characteristics have on flocculation process efficiency. This paper is a summary of advances in research on this topic over several years. Morphological characteristics of colloids in natural waters and different kinds of hydrolysed coagulants are investigated, and their effect on colloid stability, flocculation kinetics and efficiency is analysed. It is confirmed that the traditional theory has some deviations in coagulation of nonspherical particles, and these deviations are revised by the flocculation morphology model. Flocculation morphology can not only promote research about flocculation theory, but also instruct the production, application and flocculation control. It can be foreseen that more progress will be made in research and application of flocculation morphology in the near future. 相似文献
94.
This letter presents some further results on the local stability in equilibrium for Internet congestion control algorithm proposed by Low et al., (IEEE/ACM Transactions on Networking, 1999). The propagation delay d(t) is assumed to be time-varying and have maximum and minimum delay bounds (i.e., d/sub m//spl les/d(t)/spl les/d/sub M/), which is more general than the assumption (0相似文献
95.
研究了用固体润滑石墨、碳化硅、二硫化钼等填料改性的聚苯硫醚 (PPS)涂层的耐磨性能。实验结果表明 ,聚苯硫醚复合涂层具有优良的耐磨性 ;加入适量 ( 3 0 % )的石墨、碳化硅等固体润滑剂 (石墨 :碳化硅 =2∶3 ) ,可以有效提高涂层的耐磨性能 ,而二硫化钼和三氧化二铬的减摩效果更佳 相似文献
96.
97.
In this work, we study dynamic provisioning of multicast sessions in a wavelength-routed sparse splitting capable WDM network
with an arbitrary mesh topology where the network consists of nodes with full, partial, or no wavelength conversion capabilities
and a node can be a tap-and-continue (TaC) node or a splitting and delivery (SaD) node. The objectives are to minimize the
network resources in terms of wavelength-links used by each session and to reduce the multicast session blocking probability.
The problem is to route the multicast session from each source to the members of every multicast session, and to assign an
appropriate wavelength to each link used by the session. We propose an efficient online algorithm for dynamic multicast session
provisioning. To evaluate the proposed algorithm, we apply the integer linear programming (ILP) optimization tool on a per
multicast session basis to solve off-line the optimal routing and wavelength assignment given a multicast session and the
current network topology as well as its residual network resource information. We formulate the per session multicast routing
and wavelength assignment problem as an ILP. With this ILP formulation, the multicast session blocking probability or success
probability can then be estimated based on solving a series of ILPs off-line. We have evaluated the effectiveness of the proposed
online algorithm via simulation in terms of session blocking probability and network resources used by a session. Simulation
results indicate that our proposed computationally efficient online algorithm performs well even when a fraction of the nodes
are SaD nodes. 相似文献
98.
Wei Li Zhang Wei Pan Bin Luo Xi Hua Zou Meng Yao Wang 《Photonics Technology Letters, IEEE》2008,20(9):712-714
A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications. 相似文献
99.
Bin Xie Shi X.Q. Han Ding 《Components and Packaging Technologies, IEEE Transactions on》2008,31(2):361-369
In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles used in the ACA assembly are with cracks in the metal coating of the particles after the ACA bonding. This paper introduced the fracture analysis by applying the cohesive elements in the numerical model of the nickel-coated polymer particle and further simulating the cracks initiation and propagation in the nickel coating during the ACA bonding. The simulation results showed that the stress distribution on the nickel-coated particle with cracks was significantly different from that on the nickel-coated particle without crack, indicating that the stress analysis by taking the crack into consideration is very important for the reliability assessment of the ACA interconnection. The stress analysis of cohesive elements indicated that the cracks initiated at the central area of the nickel coating and propagated to the polar area. Furthermore, by the introduction of a new parameter of the virtual resistance, a mathematical model was established to describe the electrical characteristics of the nickel-coated particle with cracks. The particle resistance of the nickel-coated particle with cracks was found to be much higher than that of the particle without crack in the optimized bonding pressure range, indicating that it is necessary to take the crack into consideration for the particle conduction analysis as well. Therefore, the fracture analysis on the conductive particle by taking the crack into consideration could accurately evaluate the reliability of ACA interconnection and avoid serious reliability issues. 相似文献
100.