全文获取类型
收费全文 | 6362篇 |
免费 | 166篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 467篇 |
综合类 | 18篇 |
化学工业 | 1668篇 |
金属工艺 | 168篇 |
机械仪表 | 171篇 |
建筑科学 | 208篇 |
矿业工程 | 1篇 |
能源动力 | 281篇 |
轻工业 | 564篇 |
水利工程 | 25篇 |
石油天然气 | 8篇 |
无线电 | 446篇 |
一般工业技术 | 1100篇 |
冶金工业 | 540篇 |
原子能技术 | 249篇 |
自动化技术 | 642篇 |
出版年
2023年 | 33篇 |
2022年 | 51篇 |
2021年 | 115篇 |
2020年 | 60篇 |
2019年 | 69篇 |
2018年 | 89篇 |
2017年 | 74篇 |
2016年 | 137篇 |
2015年 | 94篇 |
2014年 | 177篇 |
2013年 | 377篇 |
2012年 | 230篇 |
2011年 | 352篇 |
2010年 | 306篇 |
2009年 | 316篇 |
2008年 | 356篇 |
2007年 | 294篇 |
2006年 | 249篇 |
2005年 | 252篇 |
2004年 | 198篇 |
2003年 | 188篇 |
2002年 | 188篇 |
2001年 | 133篇 |
2000年 | 118篇 |
1999年 | 131篇 |
1998年 | 235篇 |
1997年 | 163篇 |
1996年 | 147篇 |
1995年 | 85篇 |
1994年 | 110篇 |
1993年 | 104篇 |
1992年 | 64篇 |
1991年 | 85篇 |
1990年 | 65篇 |
1989年 | 92篇 |
1988年 | 82篇 |
1987年 | 50篇 |
1986年 | 82篇 |
1985年 | 69篇 |
1984年 | 62篇 |
1983年 | 59篇 |
1982年 | 66篇 |
1981年 | 54篇 |
1980年 | 43篇 |
1979年 | 43篇 |
1978年 | 44篇 |
1977年 | 38篇 |
1976年 | 35篇 |
1975年 | 19篇 |
1973年 | 20篇 |
排序方式: 共有6556条查询结果,搜索用时 15 毫秒
31.
Keishi Sakamoto Atsushi Kasugai Masaki Tsuneoka Koji Takahashi Yukiharu Ikeda Tsuyoshi Imai Takashi Nagashima Mitsuru Ohta Tsuyoshi Kariya Kenichi Hayashi Yoshika Mitsunaka Yosuke Hirata Yasuyuki Itoh Yukio Okazaki 《Journal of Infrared, Millimeter and Terahertz Waves》1997,18(9):1637-1654
A development of 170GHz/500kW level gyrotron was carried out as R&D work of ITER. The oscillation mode is TE31,8. In a short pulse experiment, the maximum power of 750kW was achieved at 85kV/40A. The efficiency was 22%. In the depressed collector operation, 500kW/36%/50ms was obtained. The maximum efficiency of 40% was obtained at PRF=470kW whereas the power decrease by the electron trapping was observed. Pulse extension was done up to 10s at PRF=170kW with the depressed collector operation. The power was limited by the temperature increase of the output window. 相似文献
32.
Y. Itoh Y. Mitsunaka K. Sakamoto T. Nagashima 《Journal of Infrared, Millimeter and Terahertz Waves》1992,13(9):1353-1359
An experiment was carried out for transforming the 120 GHz-TE12.2 whispering-gallery mode (WGM) into a circularly polarized hollow radiation beam. A hollow beam was formed by reflecting the WGM, which was radiated from a 16 mm radius circular waveguide cut, with an annular mirror having suitable local normal vectors. The experimentally observed field intensity profiles of the reflected wave were in good agreement with calculated results. 相似文献
33.
The oxidation of Fe(II) with dissolved molecular oxygen was studied in sulfuric acid solutions containing 0.2 mol . dm-3 FeSO4 at temperatures ranging from 343 to 363 K. In solutions of sulfuric acid above 0.4 mol . dm-3, the oxidation of Fe (II) was found to proceed through two parallel paths. In one path the reaction rate was proportional
to both [Fe2+]2 and po2, exhibiting an activation energy of 51.6 . kJ mol-1. In another path the reaction rate was proportional to [Fe2+]2, [SO4-], and po2 with an activation energy of 144.6 kJ . mol-1. A reaction mechanism in which the SO4- ions play an important role was proposed for the oxidation of Fe(II). In dilute solutions of sulfuric acid below 0.4 mol
. dm-3, the rate of the oxidation reaction was found to be proportional to both [Fe(II)]2 and Po2, and was also affected by [H+] and [SO2-
4]. The decrease in [H+] resulted in the increase of reaction rate. The discussion was further extended to the effect of Fe (III) on the oxidation
reaction of Fe (II). 相似文献
34.
Deposition rate dependence of perpendicular coercivity Hcl in Cocr evaporated films at the deposition rate ranging from 0.4nm/s to 400nm/s is studied. Hcl increases with decreasing deposition rate as well as with increasing substrate temperature. A High Hcl over 500 Oe, which has ever been obtained only at a substrate temperature over 250°C when deposition rate is high(400nm/s), is obtained at a substrate temperature of 150°C under deposition rate of 2nm/s. "Shoulder" in the hysteresis loop disappears as Hcl exceeds 400 Oe. Therefore to decrease the deposition rate and to increase the substrate temperature have the same effect on Hcl. Saturation magnetization of the films with the same Cr concentration increases with decreasing deposition rate, and it is suggested that the degree of Cr segregation increases with decreasing deposition rate. Hcl is independent of the background pressure when the relative pressure, the quotient of (background pressure/deposition rate), is between 2×10-8and 5×10-6torr/(nm/s). From the results above, it is clarified that the difference of deposition rate between vacuum evaporation and sputtering is one of the major reasons for the difference of Hcl between the two. 相似文献
35.
Tomoko Akai Hiroshi Yamanaka Hajimu Wakabayashi 《Journal of the American Ceramic Society》1996,79(4):859-864
Copper-ruby glasses were prepared by the sputtering method and the effect of reducing treatment was examined. The reducing was carried out either during sputtering or heat treatment. Optical absorption was related to the growth of copper particles. The results are summarized as follows: (i) the volume fraction of copper particles in the glasses which are heat-treated in air increases with the addition of hydrogen in the sputtering gas. (ii) The copper particles do not grow larger than 8 nm by heat treatment in reducing atmosphere, whereas they grow as large as 12 nm in air. (iii) Reducing during heat treatment gives a pronounced effect only when sputtering was not carried out under reducing conditions. The origin of these phenomena was also discussed, considering the mechanism of nucleation and growth of copper particles. 相似文献
36.
A molecular orbital approach to materials design has recently made great progress. This approach is based on the electronic structure calculations by the DV-Xα cluster method. In this paper recent progress in this approachis reviewed. In particular 相似文献
37.
Highly transparent cellulose hydrogels with physical crosslinkage were prepared from nonaqueous organic cellulose solutions and viscose by coagulating and regenerating cellulose in an aqueous solution containing a water‐miscible organic solvent. Nonaqueous organic cellulose solutions used were LiCl/dimethylacetamide, paraformaldehyde/dimethyl sulfoxide, and triethylammonium chloride/dimethyl sulfoxide. Preparation conditions and physical properties of the transparent cellulose hydrogels were studied. The transparency of the cellulose hydrogels depended on the composition of the aqueous solution containing the organic solvent. Furthermore, transparent cellulose hydrogels from viscose showed high tensile strength. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3020–3025, 2003 相似文献
38.
S Yamada Y Takai K Nemoto Y Ogawa Y Kakuto A Hoshi K Sakamoto 《Canadian Metallurgical Quarterly》1992,31(5):563-567
Prognostic factors in esophageal carcinoma treated with irradiation were examined. The prognosis of 111 patients without metastasis who had received more than 60 Gy was analyzed. Significant associations were found between survival rates and tumor length, stage, radioresponse of the primary tumor and the s.c. X-P classification based on barium contrast radiography; superficial type (tumor limited to the surface of the esophageal wall), tumorous type (solid mass without ulceration), Ul-A type (tumor with shallow ulceration with regular margin), Ul-B type (tumor with deep ulceration or irregular ulcer margin), and funneled type (tumor invading the esophageal wall in a scirrhous pattern). In multiple regression analysis, the X-P classification had the strongest correlation with survival and the survival rates of patients with the superficial type, the tumorous type and the s.c. Ul-A type were significantly higher than those of patients with the other tumor types (p < 0.001). 相似文献
39.
Kyoko Kawagishi Hiroshi Harada Akihiro Sato Atsushi Sato Toshiharu Kobayashi 《JOM Journal of the Minerals, Metals and Materials Society》2006,58(1):43-46
The fourth-generation nickel-based single-crystal superalloys, which contain large amounts of refractory metals for strengthening
and platinum group metals for topologically close-packed phase prevention, show excellent high-temperature strength. However,
these alloying elements seem to decrease high-temperature oxidation resistance. In this study, nickel-based superalloys with
various amounts of tantalum, rhenium, and ruthenium were examined in isothermal and cyclic exposures at 1,100°C to investigate
the effect on the oxide growth rate and resistance to scale spallation. Ruthenium and rhenium were found to degrade the oxidation
resistance by the vaporization of their oxide. Tantalum-rich oxide in the spinel layer acts to stabilize ruthenium and rhenium
oxide in the scale. The addition of hafnium and yttrium is effective in improving the oxidation resistance of ruthenium-containing
nickel-based superalloys. 相似文献
40.
Yoshio Yamashita Hideyuki Jinbo Ryuji Kawazu Takateru Asano Hiroshi Umehara 《Polymer Engineering and Science》1991,31(12):855-859
LMR-UV (“low molecular weight resist for uv lithography”), a naphthoquinone-diazide sulfonic acid ester of a novolak resin, is a negative working resist. The mechanism of insolubilization of LMR-UV is based on the facts that the naphthoquinone-diazide moiety is decomposed to indenecarboxylic acid (polar compound) by photolysis upon UV irradiation and that the irradiated resist film insolubilizes in a non-polar developer. LMR-UV reliably forms 0.6 μm lines and spaces over a reflective substrate with steps by using a g-line stepper having a 0.35 NA lens. 0.6 μm-wide aluminum patterns over topography are obtained by use of g-line exposure and reactive ion etching. By use of an i-line aligner (NA = 0.42), LMR-UV resolves 0.25 μm space patterns with overhang profiles. The profiles are due to the large absorption coefficient of 3.8 μm?1. 0.3 μm wide aluminum patterns are formed by i-line exposure and lift-off metallization. 相似文献