全文获取类型
收费全文 | 1494篇 |
免费 | 46篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 51篇 |
综合类 | 3篇 |
化学工业 | 443篇 |
金属工艺 | 44篇 |
机械仪表 | 29篇 |
建筑科学 | 35篇 |
矿业工程 | 1篇 |
能源动力 | 65篇 |
轻工业 | 137篇 |
水利工程 | 6篇 |
石油天然气 | 12篇 |
无线电 | 113篇 |
一般工业技术 | 290篇 |
冶金工业 | 124篇 |
原子能技术 | 35篇 |
自动化技术 | 158篇 |
出版年
2023年 | 9篇 |
2022年 | 24篇 |
2021年 | 29篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 38篇 |
2017年 | 29篇 |
2016年 | 45篇 |
2015年 | 27篇 |
2014年 | 42篇 |
2013年 | 75篇 |
2012年 | 67篇 |
2011年 | 96篇 |
2010年 | 79篇 |
2009年 | 84篇 |
2008年 | 86篇 |
2007年 | 78篇 |
2006年 | 47篇 |
2005年 | 49篇 |
2004年 | 34篇 |
2003年 | 46篇 |
2002年 | 42篇 |
2001年 | 33篇 |
2000年 | 24篇 |
1999年 | 29篇 |
1998年 | 61篇 |
1997年 | 48篇 |
1996年 | 32篇 |
1995年 | 40篇 |
1994年 | 34篇 |
1993年 | 23篇 |
1992年 | 11篇 |
1991年 | 16篇 |
1990年 | 17篇 |
1989年 | 11篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 9篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有1546条查询结果,搜索用时 15 毫秒
61.
The effect of the 2008 Iwate-Miyagi Nairiku earthquake (MJ 7.2), Japan on the Aratozawa dam, which is a 74.4 m high rockfill dam with a central clay core located in the area, was studied with a main focus on the change in the vibration period, shear wave velocity, shear modulus, and pore-water pressure. In a vertical section of the central part of the dam, three sets of 3-component accelerometers and 15 pore water pressure meters were installed. During the main shock, the acceleration exceeded 10 m/s2 at the gallery, inducing large shear strains in excess of 10-3 and a sudden build-up of the excess pore water pressure in the core. Due to the large strains, the shear wave velocity and shear modulus showed a significant decrease from their initial values and the vibration period was elongated. The decreased shear wave velocity gradually recovered toward the end of the main shock, and continued to recover with the passage of time. The full recovery of the wave velocity was found to take at least one year, while the dissipation of the excess pore water pressure proceeded more quickly than the recovery of the wave velocity. 相似文献
62.
The goal of this paper is to augment the ordinal temporal-difference type (TD-type) reinforcement learning model in order to detect the most suitable learning model of the human decision-making process in financial investment tasks. The simplicity and robustness of the TD-type learning model is fascinating. However, the available evidence and our observation suggest the necessity of introducing the nonlinear effect in learning and the possibility that additional factors might play important roles in the investment decision-making process. To extend the ordinal TD-type learning model, we adopt a three-layered perceptron as the basis function and the hierarchical Bayesian method to calibrate the parameter values. The result of the predictive test suggests that the augmented TD-type learning model constructed in this paper can evade the overfitting and can predict people's investment behavior well as compared to other familiar learning models. 相似文献
63.
Katsunori Takeda Tetsuo Hattori Tetsuya Izumi Hiromichi Kawano Shinichi Masuda 《Artificial Life and Robotics》2010,15(4):421-424
Recently, remote monitoring camera systems have been widely used for security. In such systems, one important function is
that the system automatically detects any change in the scenes from the monitoring cameras. In wireless remote monitoring
camera systems, the images of the scenes are generally transmitted as compressed data (e.g., JPEG file), because of the capacity
of the wireless channel. This article shows the automated detection of the change point in time-series data of compressed
JPEG file quantity (Kbytes) from the monitoring camera by applying the sequential probabilistic ratio test (SPRT) and the
Chow test, which is well known as a standard method for detecting structural change in time-series data. 相似文献
64.
Hideki Tanaka Daisuke Noguchi Akiko Yuzawa Tetsuya Kodaira Hirofumi Kanoh Katsumi Kaneko 《Journal of Low Temperature Physics》2009,157(3-4):352-373
We have investigated the applicability of simulations and theoretical techniques for exploring the selectivities of hydrogen isotopes. We have simulated the adsorption isotherms of H2 in an idealized carbon slit pore at 77 K by using the grand canonical Monte Carlo simulations with the Feynman-Hibbs effective potential (FH-GCMC) and the rigorous path integral method (PI-GCMC), and we obtained good agreement between the isotherms from both simulations. This suggests that FH-GCMC, which uses the approximative Feynman-Hibbs treatment, is as useful as PI-GCMC for exploring H2 adsorption at 77 K. Moreover, we show that the ideal adsorption solution theory (IAST) can predict the selectivity of D2 over H2 in the interstices of single-wall carbon nanotube (SWNT) bundles at 77 K (below 0.1 MPa) very well by comparing the obtained results with the mixture adsorption FH-GCMC simulations. This indicates that IAST is also applicable to the estimation of the selectivity of D2 over H2 at moderate pressures and at 77 K from experimental single-component adsorption isotherms. We also demonstrate that the FH-GCMC simulation can reproduce the experimental adsorption isotherms of H2 and D2 in aluminophosphate AlPO4-5 at 77 K. Finally, we analyze the selectivity of D2 over H2 by IAST with the experimental single-component adsorption isotherms of H2 and D2 at 77 K for a variety of adsorbents: AlPO4-5, activated carbon fibers (ACFs), HiPco SWNT, and SWNHs. The selectivities predicted by the experimental adsorption data based on the results from the FH-GCMC simulations are presented and discussed. 相似文献
65.
Crack tip opening displacement (CTOD) has been calculated using the plastic hinge model with an assumed rotational center since the British Standards Institution (BS) standardized BS5762 in 1979. The American Society for Testing and Materials (ASTM) accepted the plastic hinge model and standardized E1290 in 1989. However, ASTM revised E1290 in 2002, and has proposed a conversion from J to CTOD. CTOD-based fracture toughness evaluation has been widely used for the defect assessment of many welded structural components, and two different CTOD calculations could lead to confusion for Fitness-for-Service. In this study, the effects of CTOD testing methodologies on CTOD values were investigated according to round robin tests conducted by the Japan Welding Engineering Society (WES), and the concept of CTOD as a fracture parameter is discussed. 相似文献
66.
Nanoparticles of Pd-Sn were prepared under various conditions by applying ultrasonic irradiation, and their electrocatalytic activity for oxygen reduction was evaluated in 0.5 M KOH. The average size of Pd-Sn nanoparticles thus prepared was about 3-5 nm. The Pd in Pd-Sn nanoparticles was found to be mostly in the metallic state. The electrocatalytic activity of the Pd-Sn nanoparticles for the oxygen reduction reaction (ORR) is greater than Pt or Pd nanoparticles in alkaline media. The molar ratio of Pd to Sn metal ions in the synthesizing solution, their initial concentrations, the concentration of ethanol, which increases primary hydrogen radicals during sonolysis, and the concentration of citric acid were found to affect the size distribution of the Pd-Sn nanoparticles, and therefore, those factors controlled the electrocatalytic activity for ORR. Particularly, the concentration of citric acid was found to be important for controlling the surface property on Pd-Sn particles to adjust the electrocatalytic activity for ORR. 相似文献
67.
Adrenomedullin (AM) was originally characterized in extracts of an adrenal medullary tumor. Since this original finding the peptide and its mRNA have also been found in the adrenal cortex, specifically, in the cells of the aldosterone-secreting zona glomerulosa. It is clear that the synthesis of AM is actively regulated in both cortex and medulla. Much research effort has been focused on identifying a role for AM in the adrenal gland. To date, no consistent effect on medullary catecholamine biosynthesis has been demonstrated. In the cortex the actions of AM are controversial and appear to depend on both the tissue preparation used and on the specific receptor population expressed in the individual gland. The results of further studies on the long-term actions of AM on adrenal growth and differentiation are awaited with interest. 相似文献
68.
Scaling of land surface temperature using satellite data: A case examination on ASTER and MODIS products over a heterogeneous terrain area 总被引:4,自引:0,他引:4
Land surface temperature (LST) is a key parameter in numerous environmental studies. Surface heterogeneity induces uncertainty in pixel-wise LST. Spatial scaling may account for the uncertainty, however, different approaches lead to differences in scaled values. Satellite-retrieved LST may be representative of the pixel-wise LST and useful for scaling analysis, but the limited accuracy of retrieved values adds uncertainty into the scaled values. Based on the Stefan-Boltzmann (S-B) law, this study proposed scaling approaches for LST over flat and relief areas to explore the combined uncertainties in scaling using satellite-retrieved data. To take advantage of simultaneous, multi-resolution observations at coincident nadirs by the Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) and the MODerate-resolution Imaging Spectroradiometer (MODIS), LST products from these two sensors were examined for part of the Loess Plateau in China. 90-m ASTER LST data were scaled up to 1 km using the proposed approaches, and variation in the LST was generally reduced after scaling. Amongst the sources of uncertainties, surface heterogeneity (emissivity) and different scaling approaches resulted in very minor differences, with a maximum difference of 0.2 K for the upscaled LST. Terrain features, taken as an areal weighting factor, had negligible effects on the upscaled value. Limited accuracy of the retrieved LST was the major uncertainty. The overall LST increased 0.6 K on average with correction for terrain-induced angular effect and 0.4 K for both angular and adjacency effects over the study area. Accounting for terrain correction in scaling is necessary for rugged areas. With terrain correction, the upscaled ASTER LST achieved an agreement of − 0.1 ± 1.87 K and a root mean square error (RMSE) of 1.87 K overall with the 1-km MODIS LST rectified by Wan et al.'s approach [Wan, Z., Zhang, Y., Zhang Q., Li, Z.-L. (2002b), Validation of the land-surface temperature products retrieved from Terra Moderate Resolution Imaging Spectroradiometer data. Remote Sensing of Environment, 83, 163-180]. Refining the rectification approach resulted in a better agreement of − 0.2 ± 1.57 K and a RMSE of 1.58 K. 相似文献
69.
Yoshino T Sotome I Ohtani T Isobe S Oshita S Maekawa T 《Journal of electron microscopy》2000,49(3):483-486
Barley cells cut from a sprout were exposed to either air or high-pressure xenon gas for 3 days and the surface of those cells was observed by atomic force microscopy (AFM) to examine the effect of the gas treatment. This method enabled the direct observation of the fresh surface of the barley cells in solution at high resolution. The cuticle layer was preserved on the primary cell wall of 0.48 MPa xenon gas-treated barley cells, while air-treated barley cells lost the cuticle layer from the primary cell wall. These findings indicate that the high-pressure xenon gas treatment is effective to preserve the cuticle layer attached to the primary cell wall. AFM is a powerful tool for the observation of the surface structure of living plant cells in solution. 相似文献
70.
Takami Tohyama Susumu Nagai Yasumasa Shibata Sadamichi Maekawa 《Journal of Low Temperature Physics》1999,117(3-4):211-215
We investigate the electronic states of underdoped La
2–x
Sr
x
CuO
4
(LSCO) by using a microscopic model, i.e., t-t-t-J model, containing charge stripes. The numerically exact diagonalization calculation is employed on small clusters. The physical properties observed in the angle-resolved photoemission and optical conductivity experiments are consistently explained in the model with vertical stripes, but not diagonal ones. These results demonstrate a crucial role of the vertical stripes in underdoped LSCO. 相似文献