全文获取类型
收费全文 | 30245篇 |
免费 | 2151篇 |
国内免费 | 401篇 |
专业分类
电工技术 | 864篇 |
综合类 | 520篇 |
化学工业 | 6309篇 |
金属工艺 | 1293篇 |
机械仪表 | 1792篇 |
建筑科学 | 964篇 |
矿业工程 | 191篇 |
能源动力 | 1214篇 |
轻工业 | 2609篇 |
水利工程 | 237篇 |
石油天然气 | 378篇 |
武器工业 | 64篇 |
无线电 | 4723篇 |
一般工业技术 | 5877篇 |
冶金工业 | 1879篇 |
原子能技术 | 415篇 |
自动化技术 | 3468篇 |
出版年
2024年 | 24篇 |
2023年 | 361篇 |
2022年 | 513篇 |
2021年 | 984篇 |
2020年 | 722篇 |
2019年 | 736篇 |
2018年 | 924篇 |
2017年 | 922篇 |
2016年 | 1046篇 |
2015年 | 900篇 |
2014年 | 1434篇 |
2013年 | 1931篇 |
2012年 | 2045篇 |
2011年 | 2478篇 |
2010年 | 1898篇 |
2009年 | 1855篇 |
2008年 | 1744篇 |
2007年 | 1416篇 |
2006年 | 1236篇 |
2005年 | 1133篇 |
2004年 | 928篇 |
2003年 | 869篇 |
2002年 | 891篇 |
2001年 | 802篇 |
2000年 | 636篇 |
1999年 | 606篇 |
1998年 | 849篇 |
1997年 | 536篇 |
1996年 | 474篇 |
1995年 | 343篇 |
1994年 | 238篇 |
1993年 | 206篇 |
1992年 | 160篇 |
1991年 | 129篇 |
1990年 | 98篇 |
1989年 | 113篇 |
1988年 | 88篇 |
1987年 | 71篇 |
1986年 | 57篇 |
1985年 | 49篇 |
1984年 | 49篇 |
1983年 | 37篇 |
1982年 | 38篇 |
1981年 | 38篇 |
1980年 | 34篇 |
1979年 | 16篇 |
1977年 | 24篇 |
1976年 | 35篇 |
1975年 | 20篇 |
1974年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The transmission mode of holographic polymer‐dispersed liquid crystals (HPDLCs) was developed an under electric field. It is reported that orientation of LC molecules under an electric field induces orientation of oligomer molecules giving rise to low off‐state diffraction and small grating shrinkage. Copyright © 2005 Society of Chemical Industry 相似文献
72.
Biodegradable multiblock poloxamers (BMPs) with gel duration of 8 h to several weeks were prepared by varying their molecular weights from 4000 to 40 000 g mol?1. The molecular weight of the BMP was controlled by changing the poloxamer to coupling agent ratio. Assuming a micelle packing model of the BMP gel, as in the case of a poloxamer gel, the micelle properties and critical gel concentration of BMPs were investigated on the basis of the scaling concept. The findings suggest that the control of molecular weight by hydrolyzable groups can be a facile approach to optimize the gel properties for biomedical applications. Copyright © 2005 Society of Chemical Industry 相似文献
73.
Existing location-based routing protocols are not versatile enough for a large-scale ad hoc environment to simultaneously meet all of the requirements of scalability, bandwidth efficiency, energy efficiency, and quality-of-service routing. To remedy this deficiency, we propose an optimal tradeoff approach that: 1) constructs a hybrid routing protocol by combining well-known location-update schemes (i.e., proactive location updates within nodes' local regions and a distributed location service), and 2) derives its optimal configuration, in terms of location-update thresholds (both distance and time-based), to minimize the overall routing overhead. We also build a route-discovery scheme based on an Internet-like architecture, i.e., first querying the location of a destination, then applying a series of local-region routing until finding a complete route by aggregating the thus-found partial routes. To find the optimal thresholds for the hybrid protocol, we derive the costs associated with both location updates and route discovery as a function of location-update thresholds, assuming a random mobility model and a general distribution for route request arrivals. The problem of minimizing the total cost is then cast into a distributed optimization problem. We first prove that the total cost is a convex function of the thresholds, and then derive the optimal thresholds. Finally, we show, via simulation, that our analysis results indeed capture the real behavior. 相似文献
74.
Han-Kyu Lim Deog Kyoon Jeong KyungTae Kim JunMo Park Han-gyoo Kim 《Communications Magazine, IEEE》2005,43(5):141-148
Network direct attached storage (NDAS) is a network storage architecture that allows direct attachment of existing ATA/ATAPI devices to Ethernet without a separate server. Unlike other architectures such as NAS, SAN, and USB mass storage, no server computer intervenes between the storage and the client hosts. We describe an NDAS disk controller (NDC) amenable to low-cost single-chip implementation that processes a simplified L3/L4 protocol and converts commands between ATA/ATAPI and Ethernet, while the remaining complex tasks are performed by remote hosts. Unlike NAS architectures that use TCP/IP, NDAS uses a TCP-like lean protocol that lends itself well to high-performance hardware realization. Thanks to the simple NDAS architecture and protocol, an NDC implemented on a single 4 mm /spl times/ 4 mm chip in 0.18 /spl mu/m CMOS technology achieves a maximum throughput of 55 Mbytes/s on gigabit Ethernet, which is comparable to that of a high-performance disk locally attached to a host computer. 相似文献
75.
JeffJu PravasPradhan 《世界电子元器件》2004,(10):30-31
消费电子和通信产业正见证着I/O解决方案从并行到高速串行的转变:能够降低成本、简化设计,并具备可延展性,满足全新带宽的要求。这类接口I/O技术的市场潜力巨大,包括移动电话、DVD-RW和高清晰度LCD电视机,而低功耗、低电磁干扰(EMI)和高数据吞吐量在这些应用中极为重要。因此,业界一直致力于设计和开发这些串行I/O,以低功耗提供高速的数据速 相似文献
76.
77.
78.
79.
80.