全文获取类型
收费全文 | 996篇 |
免费 | 28篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 52篇 |
化学工业 | 211篇 |
金属工艺 | 26篇 |
机械仪表 | 14篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 17篇 |
轻工业 | 89篇 |
水利工程 | 2篇 |
无线电 | 116篇 |
一般工业技术 | 190篇 |
冶金工业 | 218篇 |
原子能技术 | 17篇 |
自动化技术 | 63篇 |
出版年
2023年 | 2篇 |
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 4篇 |
2019年 | 12篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 18篇 |
2015年 | 13篇 |
2014年 | 16篇 |
2013年 | 29篇 |
2012年 | 32篇 |
2011年 | 36篇 |
2010年 | 31篇 |
2009年 | 33篇 |
2008年 | 33篇 |
2007年 | 42篇 |
2006年 | 40篇 |
2005年 | 44篇 |
2004年 | 34篇 |
2003年 | 30篇 |
2002年 | 30篇 |
2001年 | 20篇 |
2000年 | 19篇 |
1999年 | 32篇 |
1998年 | 99篇 |
1997年 | 55篇 |
1996年 | 33篇 |
1995年 | 26篇 |
1994年 | 22篇 |
1993年 | 28篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 3篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有1026条查询结果,搜索用时 15 毫秒
51.
52.
Ryuichi Sugimoto Hideyuki Kaneko Junji Saito Nobuo Kawahara Shingo Matsuo Tomoaki Matsugi 《Polymer Bulletin》2014,71(6):1421-1431
This paper introduces the new synthetic methodology of polyolefin-based block and graft copolymers with polar segments [e.g., polystyrene and poly(meth)acrylates]. Various brominated polyolefins were prepared by bromination of polyolefins with N-bromosuccinimide. The resulting brominated polyolefins were able to initiate the controlled radical polymerization of polar monomers, such as methyl methacrylate, ethyl acrylate, t-butyl acrylate, styrene and 2-(dimethylamino)ethyl acrylate, using a CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine catalyst system, leading to a variety of polyolefin-based copolymers with a different content of the corresponding polar segment. Because of the accessible synthesis of polyolefin macroinitiators, this synthetic methodology is expected to result in the preparation of a wide range of polyolefin-based block and graft copolymers. 相似文献
53.
Polyvinyl borate (PVBO) was prepared by the condensation of poly(vinyl alcohol) (PVA) and boric acid, and used as a precursor for boron carbide. Boron carbide powder was synthesized by the pyrolysis of the PVBO precursor in air at 600 °C for 2 h, followed by heat treatment in Ar flow at 1300 °C for 5 h, which is a relatively low temperature compared with conventional carbothermal methods. Pyrolysis of the PVBO precursor resulted in submicron-size particles of B2O3 dispersed in a carbon matrix. In addition, the pyrolysis temperature governed the carbon content in the pyrolyzed product of the PVBO precursor, which led to the synthesis of crystalline boron carbide powder with little free carbon. 相似文献
54.
Keiichiro Sugimoto Sayaka Sakamoto Kazuya Nakagawa Shuichi Hayashi Naoki Harada Ryoichi Yamaji Yoshihisa Nakano Hiroshi Inui 《Food chemistry》2011
Eucalyptus leaf extract (ELE) is rich in hydrolyzable tannins. We examined the effects of ELE and its constituents on lipopolysaccharide (LPS)-induced liver injury in mice. Mice fed a diet supplemented with 1% ELE were intraperitoneally administered LPS. Six hours later, the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were significantly lower in the ELE-supplemented mice than in the controls; LPS-induced hepatic inducible nitric oxide synthase (iNOS) expression was also suppressed. ELE lowered LPS-stimulated iNOS expression in cultured RAW 264.7 macrophages. Furthermore, the aglycones of hydrolyzable tannins, gallic acid (GA) and ellagic acid (EA), inhibited iNOS induction to a greater extent than did ELE (15-fold higher). When mice were fed a 1% GA or EA diet, the increase in the serum ALT and AST activities and hepatic iNOS expression in response to the LPS challenge were significantly attenuated. Thus, hydrolyzable tannins in ELE ameliorate LPS-induced liver injury. 相似文献
55.
56.
Induction-motor torque is not accurately controlled when the estimated secondary resistance of an induction-motor model in a vector controller differs from the true secondary resistance. An algorithm which identifies the secondary resistance on-line is developed. The motor operating condition for secondary resistance identification, the stable identifier organization, and the experimental investigation confirming the identification algorithm performance are presented. The algorithm is based on the theory of model reference adaptive systems (MRAS). The proposed algorithm stably identifies the secondary resistance under any load and any speed when a sinusoidal signal is injected into the flux axis primary current. The vector controller adopting this algorithm controls motor torque accurately under any load and any speed. 相似文献
57.
Ryuichi Masutomi Yoshitomo Karaki Hidehiko Ishimoto 《Journal of Low Temperature Physics》2002,126(1-2):241-246
We have measured the low temperature magnetization of submonolayer 3He on three layers of HD preplated graphite. NMR measurement has been performed by progressively adding 4He to the system, to prevent 3He atoms from being trapped in substrate heterogeneities and to change the areal density of 3He. The exchange constant (J) is found to have a similar density dependence to that for two layers of HD preplated one. The magnetization in the antiferromagnetic region increases gradually down to 100 K and shows no evidence corresponding to a spin gap. 相似文献
58.
Victor Efimov Ken Obara Daigo Ueno Akira Yamaguchi Hidehiko Ishimoto 《Journal of Low Temperature Physics》2002,126(1-2):121-126
The behaviour of
4
He impurities has been investigated through positive ion mobility measurements in liquid
3
He at milliKelvin temperatures. In spite of the enormous surface area of the cell, the influence of
4
He lasted for hundreds of hours at temperatures of 20 mK. However below 10 mK, the
4
He impurities were quickly frozen out on the cell walls and we were free from the impurity problem. Nevertheless the multiple ion signal occasionally appeared even at a few mK, although it disappeared for a number of ionization pulses. 相似文献
59.
一种用于PWM逆变器的非对称T型滤波器的设计方法 总被引:4,自引:5,他引:4
针对以体积最小为目的的PWM逆变器用非对称T型滤波器的参数设计中会出现高次多元方程,难以获得有用的解析解的实际问题,提出了一种采用三维数据可视化技术的设计方法:在保证低通滤波器衰减特性的前提下,分别绘出纯电阻负载和阻感负载时系统功率因数的曲面,再依次考量电力电子器件中的电流负担、电压应力等因素,从空间曲面到空间曲线,再到平面曲线,逐步地缩小取值范围。最后对电感器的结构进行了优化设计。实验验证了该方法的正确性和实用价值。 相似文献
60.
M Kushiro K Shikata H Sugimoto Y Shikata N Miyatake J Wada M Miyasaka H Makino 《Canadian Metallurgical Quarterly》1998,53(5):1314-1320
Prostacyclin (PGI2) is known to have a relaxative action on vascular smooth muscle, an inhibitory action against platelet activation and neutrophil function. Previous studies showed the preventive effects of PGI2 on lupus nephritis and Thy-1 nephritis, although the mechanism has not been clarified. Glomerular endothelial expression of intercellular adhesion molecule-1 (ICAM-1) is up-regulated in experimental and human glomerular diseases, and is known to facilitate leukocyte infiltration into the glomeruli, which ultimately induces the various glomerular injuries. In the present study, we evaluated the therapeutic effects of PGI2 on a rat model for crescentic glomerulonephritis and investigated its putative mechanism in relation to ICAM-1-mediated leukocyte recruitment. Wistar-Kyoto (WKY) rats were injected with nephrotoxic serum and received continuous intraperitoneal infusion of PGI2. PGI2 dramatically decreased proteinuria (123.0 +/- 18.8 vs. 31.6 +/- 4.5), crescent formation and deposition of fibrinogen in the glomeruli, while the deposition of rabbit IgG, rat IgG and rat C3 along the capillary walls was not changed. Furthermore, intraglomerular expression of ICAM-1 and infiltration of macrophages were significantly suppressed by administration with PGI2. In contrast, influx of CD4 or CD8 positive cells was not altered. The present results suggest that PGI2 shows the preventive effects on experimental crescentic glomerulonephritis by inhibiting intraglomerular coagulation and ICAM-1-mediated macrophage-glomerular endothelial cell adhesive pathway. 相似文献