全文获取类型
收费全文 | 4245篇 |
免费 | 66篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 199篇 |
综合类 | 5篇 |
化学工业 | 1046篇 |
金属工艺 | 152篇 |
机械仪表 | 133篇 |
建筑科学 | 75篇 |
矿业工程 | 1篇 |
能源动力 | 246篇 |
轻工业 | 233篇 |
水利工程 | 15篇 |
石油天然气 | 10篇 |
无线电 | 398篇 |
一般工业技术 | 733篇 |
冶金工业 | 682篇 |
原子能技术 | 82篇 |
自动化技术 | 325篇 |
出版年
2023年 | 22篇 |
2022年 | 49篇 |
2021年 | 84篇 |
2020年 | 38篇 |
2019年 | 38篇 |
2018年 | 51篇 |
2017年 | 44篇 |
2016年 | 56篇 |
2015年 | 43篇 |
2014年 | 75篇 |
2013年 | 194篇 |
2012年 | 131篇 |
2011年 | 221篇 |
2010年 | 158篇 |
2009年 | 163篇 |
2008年 | 181篇 |
2007年 | 157篇 |
2006年 | 127篇 |
2005年 | 117篇 |
2004年 | 107篇 |
2003年 | 152篇 |
2002年 | 113篇 |
2001年 | 97篇 |
2000年 | 69篇 |
1999年 | 113篇 |
1998年 | 349篇 |
1997年 | 210篇 |
1996年 | 132篇 |
1995年 | 91篇 |
1994年 | 120篇 |
1993年 | 93篇 |
1992年 | 59篇 |
1991年 | 53篇 |
1990年 | 57篇 |
1989年 | 50篇 |
1988年 | 43篇 |
1987年 | 44篇 |
1986年 | 50篇 |
1985年 | 50篇 |
1984年 | 37篇 |
1983年 | 47篇 |
1982年 | 29篇 |
1981年 | 24篇 |
1980年 | 38篇 |
1979年 | 32篇 |
1978年 | 23篇 |
1977年 | 20篇 |
1976年 | 24篇 |
1975年 | 13篇 |
1974年 | 14篇 |
排序方式: 共有4335条查询结果,搜索用时 15 毫秒
41.
Y Ota Y Nakano H Yamaguchi K Yoshida T Shirafuji A Adachi 《Canadian Metallurgical Quarterly》1993,20(8):1055-1057
In a 63-year-old male patient with gastric cancer having multiple liver metastases, the metastatic lesions responded well to postoperative staggered intraarterial infusion therapy with MTX and 5-FU. The intraarterial infusion therapy was administered once a week. A total of 5 courses of this therapy produced marked regression of liver metastases and remarkable necrosis. The effect was thus rated as PR. The patient is healthy and has been successfully rehabilitated. His dose is oral 5-FU (200 mg x 2). 相似文献
42.
H. Azuma A. Takeuchi T. Ito H. Fukushima T. Motohiro M. Yamaguchi 《Solar Energy Materials & Solar Cells》2002,74(1-4)
The pulsed KrF excimer laser annealing of silicon films for solar cell with EBEP-CVD and LP-CVD was studied theoretically and experimentally. Three-dimensional thermal diffusion equation for microcrystalline and amorphous silicon was solved by using the finite difference methods. The results of our heat-flow simulation of laser re-crystallization in a laser irradiation with 50 ns pulse duration almost agree with the experimental results in re-crystallization depth of 0.7 μm for microcrystalline silicon (EBEP-CVD) and 0.4 μm for amorphous silicon (LP-CVD) in a single pulse excimer laser annealing. 相似文献
43.
Y Kato S Yamaguchi H Sano Y Ogura K Katada G Takeshita F Imai T Kanno M Abe 《Canadian Metallurgical Quarterly》1996,39(4):113-115
A patient with subacute bacterial endocarditis and a peripheral mycotic aneurysm is presented. We used a combined multi-slice surface anatomy scanning (SAS) and contrast-enhanced MR angiography image to determine the exact location of the small lesion by applying a skin marker on the scalp and visualizing the relationship of the marker to the brain surface structures and to the lesion. This technique was useful for the removal of a small peripheral aneurysm using only a limited craniotomy. 相似文献
44.
Makoto Hino Minoru Hiramatsu Koichi Akiyama Hitoshi Kawasaki Masato Tsujikawa Makoto Kawamoto 《Materials and Manufacturing Processes》1997,12(1):37-46
A high powered YAG laser with kaleidoscope for surface modification was applied to the surface hardening of carbon steels containing 0. 18-0.54 wt% C without the absorbents, and the relationships between laser processing and surface hardening were investigated by hardness and microstructure. The structure of the hardened zone underwent complete martensitic transformation in all of the carbon steels tested, and its hardness increased with greater carbon content. Under identical irradiated conditions, the hardened zone expanded with increasing carbon content. A hardened zone extending from the surface to a depth of 1.0 mm was obtained at a laser power of 1.0 kW and a scanning speed of 1 mm/sec. It was found that in the surface hardening of carbon steels, a high powered YAG laser can be used to control the hardened zone by selecting the appropriate irradiation conditions, however, the hardened zone was affected by the assistant gas and the flow rate. 相似文献
45.
In the first half of the paper, various types of processing pertaining to a polygon, using the 4×4 determinant theories are explained along with a new containment test algorithm of a point in a polygon. In the latter half of the paper, a general-purpose geometric processor, the POLYGON ENGINE, is presented which can deal with various types of interference problems, such as Boolean operations in solid modelling, hidden line and surface eliminations, ray tracing and so on. It is, a successor of the TRIANGLE PROCESSOR and is also based upon the 4×4 determinant theories [4–6]. While the TRIANGLE PROCESSOR processes a triangulated polygon on a triangle-by-triangle basis, the POLYGON ENGINE can treat a polygon without triangulation. The latter is expected to be more functional, more efficient and easier to use. 相似文献
46.
Far-infrared reflection spectra of dielectric ceramics, BaSm2 Ti5 O14 , BaTi4 O9 , and some pcrovskites such as Ba(Zn1/3 Nb2/3 )O3 , have been measured at room temperature using a Fourier transform infrared spectrometer in order to investigate the effect of the crystal structure on the dielectric properties. As for perovskites, Sr(Zn1/3 Nb2/3 )O3 and Sr(Mg1/3 Nb2/3 )O3 , in which B site ions are ordered, were also measured. Reflectance data were analyzed by means of a factorized form of dielectric functions instead of the classical dispersion theory, and all of the spectra were well fitted. The values of dielectric constants and tan δ calculated from the reflectance data were in good agreement with resonant cavity measurements at 5 GHz. Furthermore, results of this study have shown that the main contribution to the microwave dielectric properties is caused by low-frequency optically active modes located at 50 to about 300 cm−1 , and for perovskite structures it is suggested that the ordering of B site ions is significant in obtaining low dielectric losses. 相似文献
47.
48.
Rabinzohn P.D. Usagawa T. Mizuta H. Yamaguchi K. 《Electron Devices, IEEE Transactions on》1991,38(2):222-231
The bipolar/FET characteristics of the 2DEG-HBT are analyzed extensively by a two-dimensional numerical simulator based on a drift-diffusion model. For bipolar operations at high collector current densities, it is confirmed that the cutoff frequency f T is determined mainly by the collector transit time of holes and by the charging time of the extrinsic base-collector capacitance C bcEXT. The charging times of the emitter and base regions and the base transit time are shown to be negligible. A high cutoff frequency F T (88 GHz) and current gain h FE (760) are obtained for an emitter size of 1×10 μm2, and undoped collector thickness of 150 nm, and a collector current density J c of 105 A/cm2. The FET operation of the same 2DEG-HBT structure shows a threshold voltage V th of 0.74 V, the transconductance G mmax of 80 mS/mm, and maximum cutoff frequency F Tmax of 15 GHz. The dependence of the device performance on material parameters is analyzed extensively from a device design point of view 相似文献
49.
The wide scattering in tool life of natural mono-crystalline diamond tools is considered to depend on intrinsic crystalline defects due to nitrogen impurities in raw diamond. In this paper, the correlation was investigated between the amounts and types of the impurity evaluated by infrared absorption (IRA) and the crater wear and chipping resistances. As a result, diamonds including less total amount of impurity show larger wear resistance and that with larger amount of B2-aggregates show larger chipping resistance. This suggests that the inspection by IRA can be a useful method for screening of raw diamond for highly durable cutting tools. 相似文献
50.
Kiyoaki Imoto Kohshin Takahashi Takahiro Yamaguchi Teruhisa Komura Jun-ichi Nakamura Kazuhiko Murata 《Solar Energy Materials & Solar Cells》2003,79(4):459-469
Here, we reported that a new carbon electrode prepared with an activated carbon was superior to a Pt sputtered electrode as the counter electrode of dye-sensitized solar cells. The photovoltaic performance was largely influenced by the roughness factor of carbon electrode. The open-circuit voltage increased by about 60 mV using the carbon counter electrode compared to the Pt counter electrode because of positive shift of the formal potential for I3−/I− couple. 相似文献