全文获取类型
收费全文 | 567035篇 |
免费 | 19378篇 |
国内免费 | 9950篇 |
专业分类
电工技术 | 17612篇 |
技术理论 | 14篇 |
综合类 | 11827篇 |
化学工业 | 84213篇 |
金属工艺 | 25656篇 |
机械仪表 | 22913篇 |
建筑科学 | 24414篇 |
矿业工程 | 6661篇 |
能源动力 | 15116篇 |
轻工业 | 40033篇 |
水利工程 | 6782篇 |
石油天然气 | 17346篇 |
武器工业 | 1402篇 |
无线电 | 71275篇 |
一般工业技术 | 99713篇 |
冶金工业 | 84579篇 |
原子能技术 | 10714篇 |
自动化技术 | 56093篇 |
出版年
2023年 | 3925篇 |
2022年 | 7524篇 |
2021年 | 10613篇 |
2020年 | 7813篇 |
2019年 | 7584篇 |
2018年 | 9816篇 |
2017年 | 10705篇 |
2016年 | 10427篇 |
2015年 | 10454篇 |
2014年 | 14949篇 |
2013年 | 27811篇 |
2012年 | 21113篇 |
2011年 | 26338篇 |
2010年 | 21400篇 |
2009年 | 22915篇 |
2008年 | 22788篇 |
2007年 | 22582篇 |
2006年 | 21438篇 |
2005年 | 19438篇 |
2004年 | 16203篇 |
2003年 | 15112篇 |
2002年 | 14067篇 |
2001年 | 13922篇 |
2000年 | 13477篇 |
1999年 | 14920篇 |
1998年 | 29940篇 |
1997年 | 21347篇 |
1996年 | 16980篇 |
1995年 | 12897篇 |
1994年 | 11155篇 |
1993年 | 10594篇 |
1992年 | 7437篇 |
1991年 | 6805篇 |
1990年 | 6356篇 |
1989年 | 6029篇 |
1988年 | 5421篇 |
1987年 | 4617篇 |
1986年 | 4562篇 |
1985年 | 4866篇 |
1984年 | 4382篇 |
1983年 | 4025篇 |
1982年 | 3793篇 |
1981年 | 3795篇 |
1980年 | 3656篇 |
1979年 | 3334篇 |
1978年 | 3295篇 |
1977年 | 3693篇 |
1976年 | 5071篇 |
1975年 | 2720篇 |
1974年 | 2659篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Photonic networks based on the optical path concept and wavelength division multiplexing (WDM) technology require unique operation, administration, and maintenance (OAM) functions. In order to realize the required OAM functions, the optical path network must support an effective management information transfer method. The method that superimposes a pilot tone on the optical signal appears very interesting for optical path overhead transfer. The pilot tone transmission capacity is determined by the carrier to noise ratio which depends on the power spectral density of the optical signal. The pilot tone transmission capacity of an optical path network employing WDM technology is elucidated; 4.5 kb/s transmission can be realized when the pilot tone modulation index is set at 3% 相似文献
52.
Uses a Markov process to model a real-time expert system architecture characterized by message passing and event-driven scheduling. The model is applied to the performance evaluation of rule grouping for real-time expert systems running on this architecture. An optimizing algorithm based on Kernighan-Lin heuristic graph partitioning for the real-time architecture is developed and a demonstration system based on the model and algorithm has been developed and tested on a portion of the advanced GPS receiver (AGR) and manned manoeuvring unit (MMU) knowledge bases 相似文献
53.
Implementing a neural network on a digital or mixed analog and digital chip yields the quantization of the synaptic weights dynamics. This paper addresses this topic in the case of Kohonen's self-organizing maps. We first study qualitatively how the quantization affects the convergence and the properties, and deduce from this analysis the way to choose the parameters of the network (adaptation gain and neighborhood). We show that a spatially decreasing neighborhood function is far more preferable than the usually rectangular neighborhood function, because of the weight quantization. Based on these results, an analog nonlinear network, integrated in a standard CMOS technology, and implementing this spatially decreasing neighborhood function is then presented. It can be used in a mixed analog and digital circuit implementation. 相似文献
54.
陈国龙 《计算机辅助设计与图形学学报》1994,6(2):136-142
本文介绍了一种在微机上实现的印制板自动布线方法──多级线探索法及其编程方法。这种方法是基于完备布线算法的概念,通过分析李氏算法和传统线探索法的不足之处而得到的。虽然它也是一种线探索法,但有较传统线探索法更强的探索能力,不需要结合李氏算法而能单独完成布线任务,是一种较理想的算法,通过实验获得了较为满意的效果。 相似文献
55.
56.
Fuzzy controller design by using neural network techniques 总被引:2,自引:0,他引:2
Cheng-Liang Chen Wen-Chih Chen 《Fuzzy Systems, IEEE Transactions on》1994,2(3):235-244
This paper investigates the relationship between the piecewise linear fuzzy controller (PLFC), in which the membership functions for fuzzy variables and the associated inference rules are all in piecewise linear forms, and a Gaussian potential function network based controller (GPFNC), in which the network output is a weighted summation of hidden responses from a series of Gaussian potential function units (GPFU's). Systematic procedures are proposed for transformation from a PLFC to its GPFNC counterpart, and vice versa. Based on these transformation principles, a series of systematic and feasible steps is presented for the design of an optimized PLFC (PLFC*) by using neural network techniques. In the design procedures, the simplified PLFC is used as the initial controller structure, then a GPFNC, which gives the approximate control response to the initially given PLFC, is found for further optimization. A neutralization process is used to demonstrate the feasibility and the potential applicability of these intelligent controllers on the regulation of highly nonlinear chemical processes 相似文献
57.
实验研究了以工业硫酸亚铁及废硫酸为原料,分别采用NaClo_3、KClO_3、H_2O_2及(o_2+NaNO_2)为氧化剂成聚硫酸铁的条件。在以(O_2+NaNO_2)为氧化剂的合成过程中,发现添加微量助催化剂(型号为HG-1、HG-2和HG-3),对提高合成速度及反应过程的稳定性具有重大作用。 相似文献
58.
Robben J.; der Schueren J.Van; Verhasselt P.; Aert R.; Volckaert G. 《Protein engineering, design & selection : PEDS》1995,8(2):159-165
The deletion of nine residues from the C-terminus of the bacterialchloramphenicol acetyltransferase (CAT) results in depositionof the mutant protein in cytoplasmic inclusion bodies and lossof chloramphenicol resistance in Escherichia coli. This foldingdefect is relieved by C-terminal fusion of the polypeptide withas few as two residues. Based on these observations, efficientpositive selection for the cloning of DNA fragments has beendemonstrated. The cloning vector encodes a C-terminally truncatedCAT protein. Restriction sites in front of the stop codon allowthe insertion of target DNA, resulting in the production ofproperly folded CAT fusion proteins and regained chloramphenicolresistance. The positive selection of recombinants is accomplishedby growth of transformants on chloramphenicol-containing agarplates. The method appears particularly convenient for the cloningof DNA fragments amplified by the PCR because minimal informationto restore CAT folding can be included in the primers. The cloningof random sequences shows that the folding defect can be relievedby fusion to a wide variety of peptides, providing great flexibilityto the positive selection system. This vector may also contributeto the determination of the role of the C-terminus in CAT folding. 相似文献
59.
Schottky diodes of aluminium/poly(3-octylthiophene)(P30T)/indium-tin oxide with large active area are prepared by using the proposed new casting technique. Their rectifying behavior and junction characteristics are dependent on whether the P30T is doped and on the storage time, but independent of the thickness of the P30T layer. The present technique can also be applied in a fabrication of electronic devices with other soluble conjugated polymers. 相似文献
60.
This paper presents a model of heterogenous diffusion in capillary porous materials during the process of drying. The governing heat and mass transfer equations have been established using the liquid as well as vapor flow. Two models have been presented. Model 1 does not consider the heat conduction while the model 2 has been established by considering the conduction. The developed models and the numerical solutions of the resulting differential equations can take into account the moisture and temperature dependent thermophysical properties of the product. All equations have been established in spherical coordinates but the programme written for the purpose of calculations can be used for other geometries also. Numerical calculations have been performed for gas concrete and tiles using model 1, while model 2 has been used for gas concrete only because of the lack of data for thermophysical properties of the tile. For gas concrete it was seen that conduction has only marginal effect on the drying process and the numerical predictions of the drying process were reasonably accurate. 相似文献