全文获取类型
收费全文 | 4657篇 |
免费 | 408篇 |
国内免费 | 234篇 |
专业分类
电工技术 | 241篇 |
技术理论 | 1篇 |
综合类 | 308篇 |
化学工业 | 551篇 |
金属工艺 | 175篇 |
机械仪表 | 545篇 |
建筑科学 | 68篇 |
矿业工程 | 46篇 |
能源动力 | 160篇 |
轻工业 | 629篇 |
水利工程 | 36篇 |
石油天然气 | 231篇 |
武器工业 | 37篇 |
无线电 | 392篇 |
一般工业技术 | 417篇 |
冶金工业 | 141篇 |
原子能技术 | 20篇 |
自动化技术 | 1301篇 |
出版年
2024年 | 19篇 |
2023年 | 79篇 |
2022年 | 186篇 |
2021年 | 206篇 |
2020年 | 160篇 |
2019年 | 132篇 |
2018年 | 128篇 |
2017年 | 122篇 |
2016年 | 147篇 |
2015年 | 199篇 |
2014年 | 222篇 |
2013年 | 286篇 |
2012年 | 305篇 |
2011年 | 308篇 |
2010年 | 231篇 |
2009年 | 267篇 |
2008年 | 252篇 |
2007年 | 279篇 |
2006年 | 240篇 |
2005年 | 255篇 |
2004年 | 200篇 |
2003年 | 177篇 |
2002年 | 155篇 |
2001年 | 126篇 |
2000年 | 115篇 |
1999年 | 105篇 |
1998年 | 79篇 |
1997年 | 61篇 |
1996年 | 49篇 |
1995年 | 46篇 |
1994年 | 30篇 |
1993年 | 17篇 |
1992年 | 21篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1975年 | 2篇 |
1963年 | 1篇 |
1958年 | 2篇 |
1957年 | 1篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有5299条查询结果,搜索用时 15 毫秒
1.
系统备份及其误区分析 总被引:1,自引:0,他引:1
张军华 《微电子学与计算机》2002,19(9):34-35
文章对系统备份的几个主要方面进行了讨论,并在此基础上,对系统备分的若干认识误区进行了分析。 相似文献
2.
The author tested the hypothesis that a history of drug-induced antagonism of alcohol impairment would enhance alcohol tolerance in humans. Groups of participants (N = 21) repeatedly performed a psychomotor task under different drug treatments: 0.65 g/kg alcohol, 4 mg/kg caffeine, or both drugs combined. Tolerance to a 0.65 g/kg alcohol dose challenge was then tested. Results showed that a history of combined alcohol and caffeine administrations increased alcohol tolerance compared with an exposure history to either drug alone. The findings contribute to the understanding of the complexities of polydrug use history and provide a useful model to examine how alcohol tolerance might be affected by a history of coadministration with other drugs (e.g., cocaine and nicotine). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
J Strother Moore 《Formal Aspects of Computing》1994,6(1):60-91
We present a formal model of asynchronous communication between two digital hardware devices. The model takes the form of a function in the Boyer-Moore logic. The function transforms the signal stream generated by one processor into that consumed by an independently clocked processor, given the phases and rates of the two clocks and the communications delay. The model can be used quantitatively to derive concrete performance bounds on communications at ISO protocol level 1 (physical level). We use the model to show that an 18-bit/cell biphase mark protocol reliably sends messages of arbitrary length between two processors provided the ratio of the clock rates is within 5% of unity. 相似文献
4.
Objective To study on the role of thymus transplantation for heart allograft in rats. Methods Vascularized heart-thymus combined transplantation was performed with microsurgical technique. Graft survival, histopathology,
level of IL-2, IL-4 and its mRNA expression in serum and cardiac grafts were investigated. Results Heart-thymus combined transplantation achieved effect in the prolongation of cardiac graft survival with short-term administration
of cyclosporine. Conclusions Vascularized thymus transplantation induced immune tolerance in thymectomized rats. 相似文献
5.
J. R. He G. C. I. Lin 《The International Journal of Advanced Manufacturing Technology》1992,7(4):210-217
A computerised trace method has been developed for determining the relationships of assembly requirements with design dimensions
and tolerances of the components in an assembly, and the relationships of design specifications and machining allowance requirements
with manufactured dimensions and tolerances of the component in a process plan. This method traces from the proposed components
or planned operations only the dimensions and tolerances that affect the given requirement, and therefore the equations for
design or for manufacture can be established simultaneously and accurately. Hence it is possible to establish constraints
for the optimisation of dimensions and tolerances for design or for manufacture. 相似文献
6.
7.
Sugarcane can be very susceptible to damage by freezes. Freeze-deteriorated cane can cause problems in processing and sometimes leads to a factory shut-down. This study was undertaken during the 2000/2001 harvest season to assess the cold tolerance performance of six commercial sugarcane varieties and to establish new and more sensitive criteria to measure cold tolerance. Two varieties CP 70-321 and CP 79-318, with known cold tolerance, were planted in the study as controls. The other varieties included LHo 83-153, LCP 85-384, HoCP 85-845 and HoCP 91-555. Freezing temperatures occurred on 20 December 2000 when the min. field temperature was −4.4 °C, and again on 21 December, 30 December through 5 January 2001, 9–10 January and 20–21 January. The lowest field temperature recorded was −5.6 °C on 4 January. Freezing conditions prevailed for 8–15 h during each freeze incident. Stalks of all varieties were frozen to the ground following the initial freeze, with freeze cracks evident only after the 4 January freeze. For this study, samples were taken on the date of the first freeze, 20 December, and subsequently again at 7, 14, 22 and 30 days after the first freeze. Criteria used to measure overall stalk cold-tolerance included changes in pH, Brix, dextran (ASI-II method), sucrose, glucose, and fructose concentrations. Mannitol, ethanol and the oligosaccharides, palatinose, leucrose, iso-maltotriose and 1-kestose, were simultaneuously measured using IC-IPAD. Marked differences were observed in most criteria for all varieties, particularly 22 and 30 days after the first freeze. Mannitol was strongly correlated (r2=0.84) with dextran, confirming its use as an indicator for cane dextran deterioration. In comparison, ethanol was only weakly correlated (r2=0.55) with dextran and did not always predict cane dextran deterioration. Iso maltotriose was the most sensitive oligosaccharide indicator of freeze deterioration, although both leucrose and palatinose could be used to confirm whether severe dextran formation (>1500 ppm/Brix) has occurred in cane. Isomaltotriose was strongly correlated (r2=0.89) with dextran and pH (r2=−0.83); pH was also a strong indicator of both dextran (r2=−0.85) and mannitol (r2=−0.92) formation. Four of the varieties, CP 79-318, LCP 85-384, HoCP 85-845 and HoCP 91-555, were shown to be susceptible to other sources of microbial and enzymic deterioration as well as dextran deterioration from Leuconostoc bacteria, especially 30 days after the first freeze. This was indicated by increased glucose/fructose ratios, ethanol formation, changes in 1-kestose concentration, and further sucrose losses. 相似文献
8.
Allen M. Johnson Michael A. Schoenfelder David J. Lebold 《Quality and Reliability Engineering International》1993,9(1):55-62
The Rainbow net simulation technique is applied to modelling the impact of system load and fault handling on the availability of a fault-tolerant multiprocessor architecture. Rainbow nets are described along with the motivation for creating this modelling technique. A Rainbow net fault-handling model is created for the fault-tolerant multiprocessor architecture and the topology is shown to remain constant in size, independent of the number of processor, memory and I/O elements configured in the system. Simulation is performed with a varying load in terms of the number of active jobs the system must support. Results are given showing how the fault-tolerant capability varies with load. Two new metrics for evaluating fault tolerance are introduced; namely full fault-tolerability and partial fault-tolerability. They are based on simple observations in the model. 相似文献
9.
疏水缔合型聚丙烯酰胺的合成与性能评价 总被引:1,自引:0,他引:1
为了提高高相对分子质量的聚丙烯酰胺的抗温抗盐性能,利用自制的两亲表面活性单体与丙烯酰胺共聚合成了疏水缔合型聚丙烯酰胺并进行室内评价。结果表明,在高温、高盐、高钙条件下,合成的疏水缔合型聚丙烯酰胺具有良好的增粘性和较强的热稳定性;克服了疏水缔合型聚合物在盐水中溶解性差的问题,可用各种矿化度的盐水和油田产出污水配制;具有良好的无机盐增粘性能和抗温性能。 相似文献
10.
In this paper, genetic algorithm is used to help improve the tolerance of feedforward neural networks against an open fault. The proposed method does not explicitly add any redundancy to the network, nor does it modify the training algorithm. Experiments show that it may profit the fault tolerance as well as the generalisation ability of neural networks. 相似文献