全文获取类型
收费全文 | 22643篇 |
免费 | 1768篇 |
国内免费 | 765篇 |
专业分类
电工技术 | 379篇 |
技术理论 | 1篇 |
综合类 | 1711篇 |
化学工业 | 4656篇 |
金属工艺 | 685篇 |
机械仪表 | 2406篇 |
建筑科学 | 668篇 |
矿业工程 | 339篇 |
能源动力 | 207篇 |
轻工业 | 3627篇 |
水利工程 | 93篇 |
石油天然气 | 720篇 |
武器工业 | 88篇 |
无线电 | 1067篇 |
一般工业技术 | 3414篇 |
冶金工业 | 1561篇 |
原子能技术 | 332篇 |
自动化技术 | 3222篇 |
出版年
2024年 | 117篇 |
2023年 | 387篇 |
2022年 | 886篇 |
2021年 | 961篇 |
2020年 | 669篇 |
2019年 | 627篇 |
2018年 | 614篇 |
2017年 | 656篇 |
2016年 | 771篇 |
2015年 | 695篇 |
2014年 | 1096篇 |
2013年 | 1371篇 |
2012年 | 1367篇 |
2011年 | 1353篇 |
2010年 | 1266篇 |
2009年 | 1344篇 |
2008年 | 1258篇 |
2007年 | 1434篇 |
2006年 | 1321篇 |
2005年 | 1207篇 |
2004年 | 1025篇 |
2003年 | 947篇 |
2002年 | 773篇 |
2001年 | 649篇 |
2000年 | 476篇 |
1999年 | 393篇 |
1998年 | 250篇 |
1997年 | 230篇 |
1996年 | 177篇 |
1995年 | 150篇 |
1994年 | 121篇 |
1993年 | 99篇 |
1992年 | 80篇 |
1991年 | 62篇 |
1990年 | 57篇 |
1989年 | 54篇 |
1988年 | 35篇 |
1987年 | 37篇 |
1986年 | 31篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1966年 | 5篇 |
1964年 | 4篇 |
1963年 | 6篇 |
1961年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Ahmadreza Momeni Amir G. Aghdam 《International Journal of Adaptive Control and Signal Processing》2007,21(10):885-910
Most of the existing switching control techniques are developed specifically for finite-dimensional linear time-invariant (LTI) systems. In many practical applications, however, it is essential to take time delay into consideration in the modelling as the control system can be highly sensitive to delay. In this paper, a multi-model switching control algorithm is proposed for retarded time-delay systems. It is assumed that the plant is represented by a family of known multi-input multi-output, observable, LTI models with multiple delays in the states, and that corresponding to each model in the known family, there exists a high-performance finite-dimensional LTI controller. In addition, it is supposed that a bound on the magnitude of the external inputs and disturbances is available. It is then shown that the proposed switching controller can stabilize the uncertain system, and that under some mild conditions, output tracking can be achieved in the given problem setting. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
42.
43.
Interfacial hybridization kinetics of oligonucleotides immobilized onto fused silica surfaces 总被引:3,自引:0,他引:3
Jiang Zeng Amer Almadidy James Watterson Ulrich J. Krull 《Sensors and actuators. B, Chemical》2003,90(1-3):68-75
Fused silica optical fibers have been used in an intrinsic mode optical configuration as biosensors for fluorescence based detection of hybridization of nucleic acids. In this work, the kinetics of hybridization of single-stranded oligonucleotides that were covalently immobilized were studied. The probe DNA was dT20, and the target was Fluorescein-labeled non-complementary (dT20) or complementary (dA20) oligonucleotide. Chronofluorimetric monitoring of the adsorption and hybridization processes was used to investigate oligonucleotide films of different density, in different salt concentrations, at temperatures of 25 and 40 °C, with the concentration of the target DNA being 0.005–0.1 μM. Mathematical models based on first- and second-order Langmuir adsorption have been examined to describe both the adsorption and the hybridization processes. Experimental data were processed using the models, and the hybridization kinetics were calculated. Hybridization kinetics on these optical fiber DNA sensors was found to be up to three orders faster than results presented for a number of other experiments using different immobilization chemistries. 相似文献
44.
45.
1 Introduction Acquiring knowledge is constantly encountered in the mechanical product evaluation process, such as during setting up evaluation index system and determining evaluation knowledge. The most useful expression form of knowledge is production rule whenever concerning the field knowledge or decision knowledge. How to effectively acquire and express the knowledge becomes the issue that the evaluation work must solve at first. One of an important application of the rough set theory is … 相似文献
46.
芳烃抽提装置技术改造 总被引:3,自引:0,他引:3
由于中国石化锦西石化分公司600kt/a连续重整装置的建设,芳烃抽提装置的原料由原来的脱戊烷油变为Ce组分。为此,对抽余油水洗塔和芳烃分离部分的苯塔塔盘,以及苯塔塔顶和塔底抽出部分进行了改造,更换部分机泵和增加变频泵,并将常规仪表改为DCS控制。改造后装置实现一次开车成功,生产出合格产品。抽余油中总芳烃含量小于0.1%,苯回收率达到99%以上。 相似文献
47.
分析了当前家装存在的破坏结构,一味追求奢华,施工质量差等种种误区,提出了搞好家庭装修的关键环节,对促进家装行业健康发展有积极的意义。 相似文献
48.
采用电子表格软件EXCEL5.0可以方便地解决许多选煤生产中的线性规划问题。本文通过选煤过程线性规划实例介绍EXCEL5.0在此领域的应用方法。 相似文献
49.
During the day, there are considerable variations in the climatic factors prevailing in these regions. This is especially so during the 24-hour daily cycle of the long, hot and dry summer (mid-May to midOctober). Such climatic conditions have had a considerable impact on the daily living pattern of family life in the same season, particularly in the urban areas. During the same 24-hour cycle, they have compelled the inhabitants to shift their living activities both vertically in section and horizontally in plan; they do this in pursuit of more acceptable, if not, desirable internal thermal environmental ambience. 相似文献
50.
Directional solidification studies of gelatinized corn starch-water mixtures were undertaken in order to examine, in situ, the freezing behavior of this food model. The solidification rate was controlled by varying sample cell velocity as it moved from a 25°C hot stage to a -25°C cold stage. While freezing at cell velocities ≤7.5 μm/sec, starch granules were alternately pushed or entrapped by the advancing solid-liquid interface producing a segregated structure consisting of alternating high-starch and low-starch bands. At a cell velocity of 10 μm/sec, the frozen product was homogeneous. The relationship between the solid-liquid interface velocity and segregation behavior was quantified and compared to an existing model of particle-interface interactions. 相似文献