全文获取类型
收费全文 | 73400篇 |
免费 | 16797篇 |
国内免费 | 1142篇 |
专业分类
电工技术 | 2333篇 |
技术理论 | 7篇 |
综合类 | 1876篇 |
化学工业 | 22888篇 |
金属工艺 | 1972篇 |
机械仪表 | 2581篇 |
建筑科学 | 3648篇 |
矿业工程 | 841篇 |
能源动力 | 2044篇 |
轻工业 | 9301篇 |
水利工程 | 784篇 |
石油天然气 | 1222篇 |
武器工业 | 171篇 |
无线电 | 12217篇 |
一般工业技术 | 15996篇 |
冶金工业 | 3419篇 |
原子能技术 | 411篇 |
自动化技术 | 9628篇 |
出版年
2024年 | 85篇 |
2023年 | 479篇 |
2022年 | 885篇 |
2021年 | 1493篇 |
2020年 | 2380篇 |
2019年 | 3877篇 |
2018年 | 3910篇 |
2017年 | 4306篇 |
2016年 | 4679篇 |
2015年 | 4944篇 |
2014年 | 5249篇 |
2013年 | 6939篇 |
2012年 | 4743篇 |
2011年 | 4781篇 |
2010年 | 4569篇 |
2009年 | 4442篇 |
2008年 | 4069篇 |
2007年 | 3741篇 |
2006年 | 3374篇 |
2005年 | 2756篇 |
2004年 | 2491篇 |
2003年 | 2543篇 |
2002年 | 2704篇 |
2001年 | 2289篇 |
2000年 | 1900篇 |
1999年 | 1204篇 |
1998年 | 1101篇 |
1997年 | 797篇 |
1996年 | 655篇 |
1995年 | 519篇 |
1994年 | 446篇 |
1993年 | 374篇 |
1992年 | 276篇 |
1991年 | 258篇 |
1990年 | 250篇 |
1989年 | 218篇 |
1988年 | 191篇 |
1987年 | 167篇 |
1986年 | 135篇 |
1985年 | 133篇 |
1984年 | 117篇 |
1983年 | 79篇 |
1982年 | 73篇 |
1981年 | 64篇 |
1980年 | 87篇 |
1979年 | 49篇 |
1978年 | 64篇 |
1977年 | 64篇 |
1976年 | 80篇 |
1975年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
101.
Seong‐Hee Kim 《Quality and Reliability Engineering International》2015,31(6):923-934
We present a distribution‐free tabular cumulative sum chart for monitoring the variability of an autocorrelated process. A quantity known as the asymptotic variance parameter is employed as a measure of the variability, and a distribution‐free tabular cumulative sum chart is applied to variance estimates calculated from batches of nonoverlapping samples. The proposed chart is applicable to a stationary process with a general marginal distribution and a general autocorrelation structure. It also determines control limits analytically without trial‐and‐error simulations. The performance of the proposed chart is tested on stationary processes with both normal and nonnormal marginals with various autocorrelation structures. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
102.
Microsystem Technologies - Recently, nonlinear system identification has received increasingly more attention due to its promising applications in engineering fields. It has become a challenging... 相似文献
103.
Sustainable biocomposites have gained considerable interest as an alternative to conventional composites in recent years due to their cost-effectiveness and environmental friendliness. The aim of this study was to investigate the performance and durability behavior of biocomposites from sustainable biocarbon (BC) as compared to conventional established fillers. The poly(butylene terephthalate) (PBT) and its composites reinforced with BC, talc, and glass fiber (GF) were prepared and the durability performances was investigated. The study showed that BC/PBT biocomposites provided a lighter weight alternative to traditionally used fillers. After undergoes thermo-oxidative aging, the mechanical properties of BC/PBT biocomposite were deteriorated. The GF/PBT showed the most stable in retaining its mechanical properties in comparison to the talc/PBT and BC/PBT. The aging behavior and mechanism of the PBT composites were discussed. This study provides further insight on the durability-related properties progression of biocomposites as compared to traditional used fillers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47722. 相似文献
104.
Li Zhang Huiqun Yuan Sheng-Hung Chang Anthony Lam 《The International Journal of Advanced Manufacturing Technology》2020,107(3):1081-1089
With the continuous development of the Internet of Things technology and the proposal of “Made in China 2025”, the construction of IoT applicat 相似文献
105.
106.
Dong‐Wook Kim 《ETRI Journal》2006,28(1):84-86
This letter presents a small‐sized, high‐power single‐pole double‐throw (SPDT) switch with defected ground structure (DGS) for wireless broadband Internet application. To reduce the circuit size by using a slow‐wave characteristic, the DGS is used for the quarter‐wave (°/4) transmission line of the switch. To secure a high degree of isolation, the switch with DGS is composed of shunt‐connected PIN diodes. It shows an insertion loss of 0.8 dB, an isolation of 50 dB or more, and power capability of at least 50 W at 2.3 GHz. The switch shows very similar performance to the conventional shunt‐type switch, but the circuit size is reduced by about 50% simply with the use of DGS patterns. 相似文献
107.
4号强热带风暴“碧利斯”造成突如其来的特大暴雨,降雨范围广,强度大,总量多,时间长,在宜章创下了之最,而且在湖南省也是罕见的。文章对“7·15”特大洪灾雨水情、灾情、抢险救灾存在的问题进行了分析和反思,并提出了防汛抢险的措施和对策。 相似文献
108.
Frequency Insertion Strategy for Channel Assignment Problem 总被引:1,自引:0,他引:1
This paper presents a new heuristic method for quickly finding a good feasible solution to the channel assignment problem
(CAP). Like many other greedy-type heuristics for CAP, the proposed method also assigns a frequency to a call, one at a time.
Hence, the method requires computational time that increases only linear to the number of calls. However, what distinguishes
the method from others is that it starts with a narrow enough frequency band so as to provoke violations of constraints that
we need to comply with in order to avoid radio interference. Each violation is then resolved by inserting frequencies at the
most appropriate positions so that the band of frequencies expands minimally. An extensive computational experiment using
a set of randomly generated problems as well as the Philadelphia benchmark instances shows that the proposed method perform
statistically better than existing methods of its kind and even yields optimum solutions to most of Philadelphia benchmark
instances among which two cases are reported for the first time ever, in this paper.
Won-Young Shin was born in Busan, Korea in 1978. He received B.S. in industrial engineering from Pohang University of Science and Technology
(POSTECH) in 2001 and M.S in operation research and applied statistics from POSTECH in 2003. Since 2003 he has been a researcher
of Agency for Defense Development (ADD) in Korea. He is interested in optimization of communication system and applied statistics.
Soo Y. Chang is an associate professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH),
Pohang, Korea. He teaches linear programming, discrete optimization, network flows and operations research courses. His research
interests include mathematical programming and scheduling. He has published in several journals including Discrete Applied
Mathematics, Computers and Mathematics with Application, IIE Transactions, International Journal of Production Research, and
so on. He is a member of Korean IIE, and ORMSS.
Jaewook Lee is an assistant professor in the Department of Industrial Engineering at Pohang University of Science and Technology (POSTECH),
Pohang, Korea. He received the B.S. degree in mathematics with honors from Seoul National University, and the Ph.D. degree
from Cornell University in applied mathematics in 1993 and 1999, respectively. He is currently an assistant professor in the
department of industrial engineering at the Pohang University of Science and Technology (POSTECH). His research interests
include nonlinear systems, neural networks, nonlinear optimization, and their applications to data mining and financial engineering.
Chi-Hyuck Jun was born in Seoul, Korea in 1954. He received B.S. in mineral and petroleum engineering from Seoul National University in
1977, M.S. in industrial engineering from Korea Advanced Institute of Science and Technology in 1979 and Ph.D. in operations
research from University of California, Berkeley, in 1986. Since 1987 he has been with the department of industrial engineering,
Pohang University of Science and Technology (POSTECH) and he is now a professor and the department head. He is interested
in performance analysis of communication and production systems. He has published in several journals including IIE Transactions,
IEEE Transactions, Queueing Systems and Chemometrics and Intelligent Laboratory Systems. He is a member of IEEE, INFORMS and
ASQ. 相似文献
109.
110.
Li D. You-Song Gu Xiang-Rong Chang Fu-Shen Li Li-Jie Qiao Zhong-Zhuo Tian Fang G.-D. Qing-Shan Song 《IEEE transactions on magnetics》2003,39(6):3554-3558
We deposited Fe-Ti-N magnetic films with a high sputtering power of 7 W/cm/sup 2/. When the composition of the films was in the range of Fe-Ti(3.9 at.%)-N(8.8 at.%) to Fe-Ti(3.3 at.%)-N(13.5 at.%), the films were composed of /spl alpha/' and Ti/sub 2/N precipitates. With the addition of nitrogen, 4/spl pi/M/sub s/ became higher than that of pure iron, reaching a maximum of 23.8 kG. At the same time, H/sub c/ was reduced to a minimum of 1.12 Oe. The best films can meet the needs of the recording head in dual-element giant magnetoresistive/inductive heads, yielding high storage density (10 Gb/in/sup 2/). The incorporation of N in /spl alpha/-Fe brought about the /spl alpha/' phase with its higher saturation magnetization. Ti additions inhibited the equilibrium decomposition /spl alpha/'/spl rarr//spl alpha/+/spl gamma/'. Because H/sub C//sup D//spl prop/D/sup 6/, where D is average grain diameter, grain size control is very important. The nitrogen induces severe distortion of the /spl alpha/' lattice, which can cause the grains to break into pieces and reduce the grain size. High sputtering power also led to the formation of fine grains, with diameter in the order of 14 nm. Probably Ti/sub 2/N is preferentially precipitated on the grain boundary, pinning the grain boundary and stabilizing the grain size during high-temperature heat treatment. The temperature limit for stability of the structure and its associated low coercivity was not less than 520/spl deg/C. 相似文献