全文获取类型
收费全文 | 13077篇 |
免费 | 373篇 |
国内免费 | 45篇 |
专业分类
电工技术 | 704篇 |
综合类 | 29篇 |
化学工业 | 3442篇 |
金属工艺 | 378篇 |
机械仪表 | 307篇 |
建筑科学 | 281篇 |
矿业工程 | 10篇 |
能源动力 | 545篇 |
轻工业 | 1099篇 |
水利工程 | 39篇 |
石油天然气 | 19篇 |
无线电 | 1148篇 |
一般工业技术 | 2301篇 |
冶金工业 | 1806篇 |
原子能技术 | 332篇 |
自动化技术 | 1055篇 |
出版年
2023年 | 65篇 |
2022年 | 109篇 |
2021年 | 316篇 |
2020年 | 129篇 |
2019年 | 160篇 |
2018年 | 195篇 |
2017年 | 153篇 |
2016年 | 247篇 |
2015年 | 194篇 |
2014年 | 323篇 |
2013年 | 605篇 |
2012年 | 523篇 |
2011年 | 677篇 |
2010年 | 570篇 |
2009年 | 596篇 |
2008年 | 652篇 |
2007年 | 542篇 |
2006年 | 483篇 |
2005年 | 423篇 |
2004年 | 383篇 |
2003年 | 427篇 |
2002年 | 372篇 |
2001年 | 284篇 |
2000年 | 284篇 |
1999年 | 280篇 |
1998年 | 784篇 |
1997年 | 501篇 |
1996年 | 372篇 |
1995年 | 263篇 |
1994年 | 260篇 |
1993年 | 241篇 |
1992年 | 156篇 |
1991年 | 169篇 |
1990年 | 100篇 |
1989年 | 154篇 |
1988年 | 92篇 |
1987年 | 120篇 |
1986年 | 111篇 |
1985年 | 138篇 |
1984年 | 113篇 |
1983年 | 110篇 |
1982年 | 115篇 |
1981年 | 100篇 |
1980年 | 82篇 |
1979年 | 79篇 |
1978年 | 80篇 |
1977年 | 87篇 |
1976年 | 104篇 |
1975年 | 39篇 |
1974年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
Toshiro Sakai Yasuhiro Tanaka Tadashi Fukao Tatsuo Takada Takashi Maeno 《Electrical Engineering in Japan》2008,162(2):10-19
Most of the breakdowns in an electric power system are caused by lightning to the tower used for high‐voltage transmission wires. To avoid accidents due to lightning, it would be desirable to develop a measurement system for the spatial electric field distribution around the tower. We have developed a new system that can measure the electric field around the steel tower for electric power transmission by using an optical electric sensor. In conventional methods, the sensor is generally illuminated by light transmitted by optical fibers. On the other hand, the new measurement system illuminates the Pockels sensor directly by using a laser to measure the far electric field. Furthermore, our newly proposed feedback system makes it possible to measure the spatial electric field without concern for the change of Pockels sensor's operation point influenced by temperature change. This system is applicable as a remote sensing system to monitor the spatial electric field around a high‐voltage transmission line. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(2): 10–19, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20552 相似文献
992.
A systematic method of determining carrier frequency assignment is proposed to minimize the cochannel interference in satellite communication systems. For the mathematical treatment of the problem, discrete positioning of carriers is introduced to avoid the nonlinear expression inherent in interference evaluation. The proposed method converts this nonlinear problem into the well-known assignment problem and enables the development of an algorithm based on the branch-and-bound method. Extended models of the proposed method are presented for practical application. To demonstrate the effectiveness of the method, computation results are shown for two typical problems. In both of the examples, cochannel interference is significantly reduced as the result of optimization of frequency assignment 相似文献
993.
Hirano K. Okamura J. Taira T. Sano K. Toyoda A. Ikeda M. 《Semiconductor Manufacturing, IEEE Transactions on》2001,14(3):202-206
Developers used in photolithography contain toxic tetramethylammoniumhydroxide (TMAH) and this creates a problem of how to properly treat developer wastewater. We have developed a TMAH wastewater treatment technique that consists of a combination of two novel decomposition processes: pyrolyzing TMAH to TMA and decomposing TMA to N 2, H2O, and CO2 by means of a selective oxidation catalyst for nitrogenous compounds. We have tested a system using this technique in long-term treatment of the actual wastewater and have found it to be sufficiently practical. The running cost of a treatment system using our technique would be about one-ninth that of disposing of the wastewater as industrial waste but about 2.3 times that of biological treatment. Compared with biological treatment, however, our system is tolerant to many treatment conditions and operation management is much easier. Furthermore, it occupies only about one-sixth the area of a biological treatment system 相似文献
994.
995.
H Kataoka A Tsuda Y Tsuda A Baba H Yoshida R Hirasawa Y Tobimatsu M Nishiguchi M Semma Y Ito 《Canadian Metallurgical Quarterly》1997,20(6):714-716
We found that an antigen-specific anaphylaxis was induced by antigen challenge to the abdominal wall, ear auricle, or subcutaneous tissue in mice sensitized 9 days previously with antigen and adjuvant. The anaphylactic reaction was detected by vascular permeability at the injected site 7 minutes after challenge, which was the best time for estimation. A novel method (AW method) for induction and detection of the anaphylactic reaction in mice was established using the abdominal wall as the challenge site. This method could detect the anaphylactic response in mice 1 to 3 weeks after sensitization. The increase in vascular permeability was completely inhibited by administration of diphenhydramine. 相似文献
996.
The catalytic decomposition of nitrous oxide to nitrogen and oxygen has been studied over Al2O3-supported and zeolite-supported Rh catalysts. The activities of Rh/Al2O3 and Rh/USY (ultrastable Y zeolite) catalysts prepared from Rh(NO3)3 were higher than those of Rh/ZSM-5 and Rh/ZnO reported in the literature, while the activity of a Rh/Al2O3 catalyst prepared from RhCl3 was suppressed severely in spite of the high H/Rh and CO/Rh values. The catalytic activity of N2O decomposition was sensitive not only to the Rh dispersion but also to the preparation variables such as the Rh precursors
and the supports used.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
997.
Y Toyoda S Yoshie T Fujita Y Ito T Nonogaki I Miwa 《Canadian Metallurgical Quarterly》1997,415(3):281-284
The effects of electrical stimulation, applied to the superior salivatory nucleus (SSN) or the cervical sympathetic nerve, on vascular permeability in nasal mucosa were studied in 16 cats. Plasma extravasation was quantified by using Evans blue. Vascular permeability in the cat nasal mucosa was increased by the electrical stimulation of SSN. Plasma extravasation induced by SSN stimulation was reduced by administration of nitric oxide synthase (NOS) antagonist, N(omega)-nitro-L-arginine methyl ester (L-NAME). Administration of atropine did not affect increased vascular permeability by SSN stimulation. We conclude that neurogenic plasma extravasation in cat nasal mucosa evoked by the parasympathetic nerve is not mediated by cholinergic fibers but rather by nitric oxide. 相似文献
998.
Yoshiharu Hatakeyama Mitsuo Umetsu Masahiro Minami Satoshi Ohara Seiichi Takami Tadafumi Adschiri 《Journal of Materials Science》2008,43(7):2426-2430
The DNA, which forms a double helical conformation by the highly selective base-pairing rule with the width of 2 nm, is one
of the polymers utilized as a template for nanoparticle assembly. Then, holiday junction structure, where two different DNA
double strands intersect and replace each complement strand, is an important artificial motif for forming two-dimensional
mesh-like DNA morphology. In this study, the two-dimensional sheet with the mesh-like conformation is formed and the growth
of the DNA morphology is controlled by changing the temperature in the formation process. The influence of the cooling procedure
on the formation process of the two-dimensional DNA sheet is observed by atomic force microscope, and the formation of double
strands in the process is traced by absorption spectra. The spectroscopic results demonstrate that the two-dimensional DNA
sheet is strongly dependent on the correlation between the applied cooling process and the melting temperature of double helical
conformation, and that the growth of the two-dimensional DNA sheet can be manipulated by the cooling procedure. Further, we
will show the size control of the DNA sheet by mixing the designed DNA which inhibits the growth of the DNA sheet. 相似文献
999.
Ichiro Shimizu Takeji Abe Takayoshi Nosho Masahiro Wakayama 《Metals and Materials International》1998,4(4):939-943
Roughening behavior of the free surface of polycrystalline iron during plane strain compression is investigated experimentally.
The changes in the shape of the free surface, which is roughened during plastic deformation, are observed in the three-dimensions.
It is found that the mountains and the valleys of the roughened shape tend to elongate in the constrained direction for the
specimen with isotropic grain shape. The shapes of the roughness curves in the loading direction and in the constrained direction
are compared. The normalized height distribution of the roughness curve in the constrained direction is symmetric, while that
of the roughness curve in the loading direction is asymmetric and positively skew during plane strain compression. Based on
a simple simulation of the roughness curves by a random midpoint displacement method, this difference is supposed to be caused
by the constraint of the material flow under plane strain condition. 相似文献
1000.