全文获取类型
收费全文 | 5292篇 |
免费 | 88篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 182篇 |
综合类 | 3篇 |
化学工业 | 950篇 |
金属工艺 | 117篇 |
机械仪表 | 113篇 |
建筑科学 | 109篇 |
矿业工程 | 1篇 |
能源动力 | 130篇 |
轻工业 | 434篇 |
水利工程 | 27篇 |
石油天然气 | 21篇 |
无线电 | 538篇 |
一般工业技术 | 908篇 |
冶金工业 | 1354篇 |
原子能技术 | 129篇 |
自动化技术 | 373篇 |
出版年
2023年 | 22篇 |
2022年 | 52篇 |
2021年 | 78篇 |
2020年 | 47篇 |
2019年 | 52篇 |
2018年 | 65篇 |
2017年 | 46篇 |
2016年 | 92篇 |
2015年 | 49篇 |
2014年 | 98篇 |
2013年 | 247篇 |
2012年 | 151篇 |
2011年 | 243篇 |
2010年 | 162篇 |
2009年 | 177篇 |
2008年 | 189篇 |
2007年 | 165篇 |
2006年 | 176篇 |
2005年 | 152篇 |
2004年 | 141篇 |
2003年 | 159篇 |
2002年 | 138篇 |
2001年 | 99篇 |
2000年 | 93篇 |
1999年 | 139篇 |
1998年 | 499篇 |
1997年 | 349篇 |
1996年 | 256篇 |
1995年 | 138篇 |
1994年 | 134篇 |
1993年 | 145篇 |
1992年 | 62篇 |
1991年 | 59篇 |
1990年 | 61篇 |
1989年 | 54篇 |
1988年 | 49篇 |
1987年 | 34篇 |
1986年 | 55篇 |
1985年 | 58篇 |
1984年 | 40篇 |
1983年 | 42篇 |
1982年 | 40篇 |
1981年 | 44篇 |
1980年 | 40篇 |
1979年 | 28篇 |
1978年 | 17篇 |
1977年 | 28篇 |
1976年 | 48篇 |
1975年 | 13篇 |
1973年 | 13篇 |
排序方式: 共有5389条查询结果,搜索用时 15 毫秒
91.
Fumiaki Mitsugi Yoshihiro Umeda Norihiro Sakai Tomoaki Ikegami 《Thin solid films》2010,518(22):6334-1307
Recently, transparent conducting oxide thin films have attracted attention for the application to transparent conducting electrodes. In this work, we evaluated the uniformity of electrical, optical and structural properties for gallium doped zinc oxide thin films prepared on the 10 × 10 cm2 silica glass substrate by pulsed laser deposition. The resistivity, carrier concentration, mobility, bonding state and atomic composition of the film were uniform along in-plane and depth direction over the 10 × 10 cm2 area of the substrate. The film showed the average transmittance of 81-87%, resistivity of 1.4 × 10− 3 Ω cm, carrier concentration of 9.7 × 1020/cm3 and mobility of 5 cm2/Vs in spite of the amorphous X-ray diffraction pattern. The gradual thickness distribution was found, however, the potential for large-area and low temperature deposition of transparent conducting oxide thin film using pulsed laser deposition method was confirmed. 相似文献
92.
Uniform temperature cooling power measurements of a superfluid Stirling refrigerator are presented for3He-4He molar concentrations of 5.9%, 17% and 36% and for temperatures between 0.37 K and 1.4 K. The results are compared to an ideal Fermi gas model and to a more general thermodynamic model. The Fermi model agrees well with the 5.9% concentration data; however, the more elaborate model is needed for higher concentration mixtures. 相似文献
93.
Wei Zhang Kazuki Tainaka Seongyool Ahn Hiroaki Watanabe Toshiaki Kitagawa 《Advanced Powder Technology》2018,29(10):2322-2330
In this study, an experimental and a numerical investigations are performed to investigate the effect of particle’s shape and size distribution on its dispersion behavior. Firstly, particle dispersion of pulverized coal and spherical polymer particles is observed by Particle Image Velocimetry (PIV) technique in the experiment. Secondly, a simulation is performed to analyze the particle dispersion in detail. Spherical and spheroidal motion models are applied to particle’s movement to investigate the shape effect. Furthermore, monodisperse and polydisperse for particles are applied to investigate the size distribution effect on the dispersion. Experimental results show that in the jet turbulence flow, pulverized coal particles, which have complex shapes and various sizes, have quite different dispersion behavior compared to spherical particles. In terms of the results of the simulation, this difference is mainly caused by the size distribution effect. Although particle’s shape affects the dispersity, it is weakened by the size distribution effect. 相似文献
94.
Underwater vehicle-manipulator systems (UVMS) are expected to play an important role in ocean exploration. It is considered
that UVMS will be operated by both automatic and manual control. We have proposed an automatic control method. In this article,
we propose a master-slave system for a UVMS. The effectiveness of the proposed master-slave control system is demonstrated
by using a floating underwater robot with a 2-link manipulator. 相似文献
95.
A new class of reduced‐order controllers is obtained for the H∞ problem. The reduced‐order controller does not compromise the performance attained by the full‐order controller. Algorithms for deriving reduced‐order H∞ controllers are presented in both continuous and discrete time. The reduction in order is related to unstable transmission zeros of the subsystem from disturbance inputs to measurement outputs. In the case where the subsystem has no infinite zeros, the resulting order of the H∞ controller is lower than that of the existing reduced‐order H∞ controller designs which are based on reduced‐order observer design. Furthermore, the mechanism of the controller order reduction is analysed on the basis of the two‐Riccati equation approach. The structure of the reduced‐order H∞ controller is investigated. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
96.
Kakimoto S. Nakajima Y. Sakakibara Y. Watanabe H. Takemoto A. Yoshida N. 《Quantum Electronics, IEEE Journal of》1990,26(9):1460-1466
The low threshold current of 9 mA, the high side-mode suppression ratio of more than 45 dB, the extremely narrow spectral linewidth of 1.1 MHz, and the low chirping of 2.8 Å at -20 dB at 2 Gb/s nonreturn to zero (NRZ) modulation have been achieved in the multiple quantum well (MQW) distributed feedback (DFB) p-substrate partially inverted buried heterostructure (PPIBH) laser diode. The spectral linewidth of 1.1 MHz is the narrowest value among 300-μm-length solitary laser diodes. These results suggest that the MQW-DFB laser diodes are a promising light source for longer distance and higher bit-rate optical communication systems and coherent optical communication systems 相似文献
97.
Tomohiko Makiyama Takashi Obama Yuichi Watanabe Hiroyuki Itabe 《International journal of molecular sciences》2022,23(12)
Lipid droplets (LDs) are intracellular organelles that are ubiquitous in many types of cells. The LD core consists of triacylglycerols (TGs) surrounded by a phospholipid monolayer and surface proteins such as perilipin 2 (PLIN2). Although TGs accumulate in the phospholipid bilayer of the endoplasmic reticulum (ER) and subsequently nascent LDs buds from ER, the mechanism by which LD proteins are transported to LD particles is not fully understood. Sar1 is a GTPase known as a regulator of coat protein complex Ⅱ (COPⅡ) vesicle budding, and its role in LD formation was investigated in this study. HuH7 human hepatoma cells were infected with adenoviral particles containing genes coding GFP fused with wild-type Sar1 (Sar1 WT) or a GTPase mutant form (Sar1 H79G). When HuH7 cells were treated with oleic acid, Sar1 WT formed a ring-like structure around the LDs. The transient expression of Sar1 did not significantly alter the levels of TG and PLIN2 in the cells. However, the localization of PLIN2 to the LDs decreased in the cells expressing Sar1 H79G. Furthermore, the effects of Sar1 on PLIN2 localization to the LDs were verified by the suppression of endogenous Sar1 using the short hairpin RNA technique. In conclusion, it was found that Sar1 has some roles in the intracellular distribution of PLIN2 to LDs in liver cells. 相似文献
98.
Shoji Seki Mami Iwasaki Hiroto Makino Yasuhito Yahara Miho Kondo Katsuhiko Kamei Hayato Futakawa Makiko Nogami Kenta Watanabe Nguyen Tran Canh Tung Tatsuro Hirokawa Mamiko Tsuji Yoshiharu Kawaguchi 《International journal of molecular sciences》2022,23(9)
The role of the ligamentum flavum (LF) in the pathogenesis of adolescent idiopathic scoliosis (AIS) is not well understood. Using magnetic resonance imaging (MRI), we investigated the degrees of LF hypertrophy in 18 patients without scoliosis and on the convex and concave sides of the apex of the curvature in 22 patients with AIS. Next, gene expression was compared among neutral vertebral LF and LF on the convex and concave sides of the apex of the curvature in patients with AIS. Histological and microarray analyses of the LF were compared among neutral vertebrae (control) and the LF on the apex of the curvatures. The mean area of LF in the without scoliosis, apical concave, and convex with scoliosis groups was 10.5, 13.5, and 20.3 mm2, respectively. There were significant differences among the three groups (p < 0.05). Histological analysis showed that the ratio of fibers (Collagen/Elastic) was significantly increased on the convex side compared to the concave side (p < 0.05). Microarray analysis showed that ERC2 and MAFB showed significantly increased gene expression on the convex side compared with those of the concave side and the neutral vertebral LF cells. These genes were significantly associated with increased expression of collagen by LF cells (p < 0.05). LF hypertrophy was identified in scoliosis patients, and the convex side was significantly more hypertrophic than that of the concave side. ERC2 and MAFB genes were associated with LF hypertrophy in patients with AIS. These phenomena are likely to be associated with the progression of scoliosis. 相似文献
99.
Hiroshi Saeki Hiroyasu EgoTakahiro Watanabe Katsuya IshibashiTakafumi Satoh Kazuo Miyamoto 《Vacuum》2011,85(10):975-977
A new vacuum seal for a rectangular flange used in r.f. equipments, was developed. The vacuum seal consists of a recess with a flat surface, machined into a rectangular flange, a rectangular metal gasket with a raised projection on one face, and a mating flange with a recess and raised projection. No leak greater than 1 × 10−10 Pa m3/s was found in leak tests, before and after baking cycles (100 °C, 12 h). 相似文献
100.
Satoru TakeshitaTatsuya Watanabe Tetsuhiko Isobe Tomohiro SawayamaSeiji Niikura 《Optical Materials》2011,33(3):323-326
YVO4:Bi3+,Eu3+ nanophosphor synthesized by the citrate route shows the photobleaching behavior, i.e., the decrease in photoluminescence intensity under the continuous irradiation of excitation light. This photobleaching property is remarkably suppressed by the washing post-treatment combined with centrifugation and the hydrothermal post-treatment. A relation between the fraction of photobleach and the amount of citrate ions coordinating to metallic ions at the surface of nanoparticles verifies that the photobleaching behavior of YVO4:Bi3+,Eu3+ nanophosphor originates from the redox reaction between the citrate ions and V5+ in YVO4 host crystal. The long-term light fastness test reveals that the hydrothermally treated YVO4:Bi3+,Eu3+ nanophosphor has sufficient photostability for practical use over 15 years outside. 相似文献