全文获取类型
收费全文 | 609787篇 |
免费 | 7903篇 |
国内免费 | 1988篇 |
专业分类
电工技术 | 11456篇 |
综合类 | 638篇 |
化学工业 | 90511篇 |
金属工艺 | 24188篇 |
机械仪表 | 19913篇 |
建筑科学 | 13506篇 |
矿业工程 | 2982篇 |
能源动力 | 16602篇 |
轻工业 | 46815篇 |
水利工程 | 6208篇 |
石油天然气 | 10609篇 |
武器工业 | 81篇 |
无线电 | 75972篇 |
一般工业技术 | 121341篇 |
冶金工业 | 113200篇 |
原子能技术 | 12922篇 |
自动化技术 | 52734篇 |
出版年
2021年 | 5620篇 |
2020年 | 4246篇 |
2019年 | 5360篇 |
2018年 | 9079篇 |
2017年 | 9175篇 |
2016年 | 9798篇 |
2015年 | 6325篇 |
2014年 | 10375篇 |
2013年 | 28999篇 |
2012年 | 16583篇 |
2011年 | 22482篇 |
2010年 | 17800篇 |
2009年 | 20004篇 |
2008年 | 20718篇 |
2007年 | 20406篇 |
2006年 | 18344篇 |
2005年 | 16425篇 |
2004年 | 15717篇 |
2003年 | 15592篇 |
2002年 | 14734篇 |
2001年 | 14568篇 |
2000年 | 13825篇 |
1999年 | 14388篇 |
1998年 | 35562篇 |
1997年 | 24771篇 |
1996年 | 19285篇 |
1995年 | 14544篇 |
1994年 | 12867篇 |
1993年 | 12836篇 |
1992年 | 9595篇 |
1991年 | 9011篇 |
1990年 | 8831篇 |
1989年 | 8316篇 |
1988年 | 7973篇 |
1987年 | 7024篇 |
1986年 | 6860篇 |
1985年 | 7777篇 |
1984年 | 7171篇 |
1983年 | 6446篇 |
1982年 | 5998篇 |
1981年 | 6163篇 |
1980年 | 5737篇 |
1979年 | 5550篇 |
1978年 | 5398篇 |
1977年 | 6256篇 |
1976年 | 7903篇 |
1975年 | 4796篇 |
1974年 | 4623篇 |
1973年 | 4678篇 |
1972年 | 3822篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
A novel class of narrow-band tunable wavelength filters is proposed and evaluated. Wavelength selectivity of the proposed filters Is derived from the finite time response of an optical nonlinearity. The nonlinearity is gain saturation in semiconductor optical amplifier structures. The filters are shown to have very narrow passbands tunable over the entire semiconductor gain bandwidth. The key to filter implementation is a device configuration in which the wave-mixing products can be isolated from the amplified inputs. Three integrated optics compatible configurations are considered and shown to have high filter throughputs 34 to 180% and subangstrom bandwidths 相似文献
82.
V. A. Arzamastsev N. L. Sardaev A. S. Kochergin 《Metal Science and Heat Treatment》1996,38(11):477-479
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described. 相似文献
83.
A fiber optic ring network, such as fiber distributed data interface (FDDI), can be operated over multiple wavelengths on its existing fiber plant consisting of point-to-point fiber links. Using wavelength division multiplexing (WDM) technology, FDDI nodes can be partitioned to operate over multiple subnetworks, with each subnetwork operating independently on a different wavelength, and inter-subnetwork traffic forwarding performed by a bridge. For this multiwavelength version of FDDI, which we refer to as wavelength distributed data interface (WDDI), we examine the necessary upgrades to the architecture of a FDDI node, including its possibility to serve as a bridge. The main motivation behind this study is that, as network traffic scales beyond (the single-wavelength) FDDI's information-carrying capacity, its multiwavelength version, WDDI, can gracefully accommodate such traffic growth. A number of design choices exist in constructing a good WDDI network. Specifically, we investigate algorithms using which, based on prevailing traffic conditions, partitioning of nodes into subnetworks can be performed in an optimized fashion. Our algorithms partition the nodes into subrings, such that the total traffic flow in the network and/or the network-wide average packet delay is minimized 相似文献
84.
The trends in high density interconnection (HDI) multichip module (MCM) techniques that have the potential to reduce interconnection cost and production time are described. The implementation in laminated dielectric (MCM-L) technology of a workstation processor core illustrates current substrate technology capabilities. The design, routing, layout and thermal management of the processor core are described. Thin-film deposited dielectric (MCM-D) technology is discussed as a cost-effective method for future interconnection applications 相似文献
85.
Many current implementations of protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) are inefficient because data are often accessed more frequently than necessary. Three techniques that reduce the need for memory bandwidth are proposed. The techniques are copy-on-write, page remapping, and single-copy. Afterburner, a network-independent card that provides the services that are necessary for a single-copy protocol stack, is described. The card has 1 MByte of local buffers and provides a simple interface to a variety of network link adapters, including HIPPI and asynchronous transfer mode (ATM). Afterburner can support transfers to and from the link adapter card at rates up to 1 Gbit/s. An implementation of TCP/IP that uses the features provided by Afterburner to reduce the movement of data to a single copy is discussed. Measurements of the end-to-end performance of Afterburner and the single-copy implementation of TCP/IP are presented 相似文献
86.
A distributed problem solving system can be characterized as a group of individual cooperating agents running to solve common problems. As dynamic application domains continue to grow in scale and complexity, it becomes more difficult to control the purposeful behavior of agents, especially when unexpected events may occur. This article presents an information and knowledge exchange framework to support distributed problem solving. From the application viewpoint the article concentrates on the stock trading domain; however, many presented solutions can be extended to other dynamic domains. It addresses two important issues: how individual agents should be interconnected so that their resources are efficiently used and their goals accomplished effectively; and how information and knowledge transfer should take place among the agents to allow them to respond successfully to user requests and unexpected external situations. The article introduces an architecture, the MASST system architecture, which supports dynamic information and knowledge exchange among the cooperating agents. The architecture uses a dynamic blackboard as an interagent communication paradigm to facilitate factual data, business rule, and command exchange between cooperating MASST agents. The critical components of the MASST architecture have been implemented and tested in the stock trading domain, and have proven to be a viable solution for distributed problem solving based on cooperating agents 相似文献
87.
Rapeseed protein concentrate (RC), prepared with 2% hexameta-phosphate, was tested for its functionality and performance in some foods. The RC had good nitrogen solubility, fat absorption, emulsification, and whipping capacities but poor water absorption and gelling properties. It increased the emulsion stability, and protein but lowered the fat content of wieners. It also increased the cooking yield, reduced the shrinkage and tenderized meat patties. Results were similar to soybean isolate except for the poorer color and flavor. The cooking yield of RC supplemented wieners was less than the all-meat control and soybean-supplemented wieners. A 9% RC dispersion mixed with an equal volume of eggwhite produced a meringue of comparable stability and texture to that of eggwhite alone. 相似文献
88.
M. D. Korostash 《Drying Technology》1985,3(4):603-611
The paper presents the results of research in the convection drying of unidirectional glass fibre bobbins on the basis of which the relations are suggested required to calculate the process of drying in the design of drying equipment. 相似文献
89.
A. A. Konstantinov N. V. Kurenkov A. B. Malinin T. E. Sazonova S. V. Sepman 《Atomic Energy》1989,67(3):696-698
Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 215–216, September, 1989. 相似文献
90.