全文获取类型
收费全文 | 808篇 |
免费 | 25篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 33篇 |
综合类 | 1篇 |
化学工业 | 330篇 |
金属工艺 | 20篇 |
机械仪表 | 10篇 |
建筑科学 | 29篇 |
能源动力 | 42篇 |
轻工业 | 66篇 |
水利工程 | 1篇 |
无线电 | 25篇 |
一般工业技术 | 158篇 |
冶金工业 | 27篇 |
原子能技术 | 19篇 |
自动化技术 | 74篇 |
出版年
2023年 | 8篇 |
2022年 | 12篇 |
2021年 | 16篇 |
2020年 | 14篇 |
2019年 | 18篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 28篇 |
2015年 | 7篇 |
2014年 | 17篇 |
2013年 | 43篇 |
2012年 | 31篇 |
2011年 | 54篇 |
2010年 | 32篇 |
2009年 | 44篇 |
2008年 | 42篇 |
2007年 | 38篇 |
2006年 | 40篇 |
2005年 | 27篇 |
2004年 | 25篇 |
2003年 | 34篇 |
2002年 | 26篇 |
2001年 | 12篇 |
2000年 | 21篇 |
1999年 | 19篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 10篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有835条查询结果,搜索用时 0 毫秒
91.
92.
93.
The microstructure of spray-dried model granules, comprising silica microspheres and poly (vinylalcohol), was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with an ultramicrotome technique. Disintegration of granules was characterized by a shear method for granular beds, and by a compression test for single granules. The internal structure changed significantly with the pH of the slurry from which the granules were spray-dried. Granules from pH 7 slurry showed the smallest apparent density, and were disintegrated under the smallest applied load. By analysing the relationship between microstructure, apparent density and flow behaviour of the slurries, it was possible to obtain a guideline for preparation of appropriate granules with controlled microstructure and strength. 相似文献
94.
Muneo Hori Toshihiro Kameda Kenji Oguni 《Mechanics of materials : an international journal》1995,21(4):313-323
To explore a possible mechanism of deep earthquakes, this paper analyzes the unstable propagation of a stress-induced phase transition which is initiated in a homogeneous stress field. This Stephen problem is formulated as an initial-value problem for the phase boundary, and the driving force of the boundary is computed by using the solution of the boundary-value problem for a partially transformed material. The propagation of the phase transition under uniform pressure is numerically simulated. It is shown that (1) under lower pressure, the transition is terminated at a certain size, but it can propagate unstably when an initially transformed region is sufficiently large; and (2) when the pressure attains a critical value, the propagation becomes unstable, and goes in a particular direction depending on the initial shape. These results confirm the possibility of the unstable propagation of phase transition, and provide a theoretical basis for the hypothesis that the phase transition of a mantle material can trigger a deep earthquake. 相似文献
95.
Toshihiro Ohtani 《Metallurgical and Materials Transactions A》2005,36(11):2967-2977
We studied the microstructure evolution of an austenitic stainless steel, Type 316L, subjected to tensile creep at 973 K through
the monitoring of shear-wave attenuation and velocity using electromagnetic acoustic resonance (EMAR). Contactless transduction
based on the Lorentz force mechanism is the key to establishing a monitor for microstructural change in the bulk of metals
with high sensitivity. In the short interval, 60 to 70 pct of the creep life, attenuation experiences a peak, independent
of the applied stress. A drastic change in dislocation mobility and rearrangement interrupted this novel phenomenon, as is
supported by observations using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The EMAR
exhibited the potential for the assessment of damage advance and the prediction of the remaining creep life of metals. 相似文献
96.
Yoshifumi Ikoma Kazunori Hayano Kaveh Edalati Katsuhiko Saito Qixin Guo Zenji Horita Toshihiro Aoki David J. Smith 《Journal of Materials Science》2014,49(19):6565-6569
This paper describes fabrication of Si nanograins through allotropic phase transformation by concurrent application of high pressure and intense straining using high-pressure torsion (HPT). Single-crystalline Si(100) wafers were processed by HPT under a pressure of 24 GPa at room temperature. X-ray diffraction and Raman analysis revealed that the HPT-processed samples were composed of metastable Si-III and Si-XII phases and amorphous phases in addition to the original diamond-cubic Si-I phase. It was found that nanograins formed because the Si-I diamond phase had transformed to high-pressure phases (Si-II, Si-XI, and Si-V) having metallic nature, and it then became easier to generate a high density of dislocations to form grain boundaries. The high-pressure phases were further transformed to the Si-XII and Si-III phases via the Si-II phase upon unloading and they existed as metastable phases at ambient pressure. Subsequent annealing at 873 K gave rise to reverse transformation to Si-I but with nanograin sizes. Although no appreciable photoluminescence (PL) peak was observed from the HPT-processed sample, a broad PL peak centered around 600 nm was detected from the annealed sample due to quantum confinement in the Si-I nanograins. 相似文献
97.
Highly Oriented Polymer Semiconductor Films Compressed at the Surface of Ionic Liquids for High‐Performance Polymeric Organic Field‐Effect Transistors 下载免费PDF全文
98.
We have developed a new calibration technique for multielement determination and U-Pb dating of zircon samples using laser ablation-inductively coupled plasma mass spectrometry (ICPMS) coupled with galvanometric optics. With the galvanometric optics, laser ablation of two or more sample materials could be achieved in very short time intervals (~10 ms). The resulting sample aerosols released from different ablation pits or different solid samples were mixed and homogenized within the sample cell and then transported into the ICP ion source. Multiple spot laser ablation enables spiking of analytes or internal standard elements directly into the solid samples, and therefore the standard addition calibration method can be applied for the determination of trace elements in solid samples. In this study, we have measured the rare earth element (REE) abundances of two zircon samples (Nancy 91500 and Pre?ovice) based on the standard addition technique, using a direct spiking of analytes through a multispot laser ablation of the glass standard material (NIST SRM612). The resulting REE abundance data show good agreement with previously reported values within analytical uncertainties achieved in this study (10% for most elements). Our experiments demonstrated that nonspectroscopic interferences on 14 REEs could be significantly reduced by the standard addition technique employed here. Another advantage of galvanometric devices is the accumulation of sample aerosol released from multiple spots. In this study we have measured the U-Pb age of a zircon sample (LMR) using an accumulation of sample aerosols released from 10 separate ablation pits of low diameters (~8 μm). The resulting (238)U-(206)Pb age data for the LMR zircons was 369 ± 64 Ma, which is in good agreement with previously reported age data (367.6 ± 1.5 Ma). (1) The data obtained here clearly demonstrate that the multiple spot laser ablation-ICPMS technique can become a powerful approach for elemental and isotopic ratio measurements in solid materials. 相似文献
99.
Tahara T Ito K Kakue T Fujii M Shimozato Y Awatsuji Y Nishio K Ura S Kubota T Matoba O 《Applied optics》2011,50(7):B31-B37
We propose an algorithm for compensating the phase-shift error of polarization-based parallel two-step phase-shifting digital holography, which is a technique for recording a spatial two-step phase-shifted hologram. Although a polarization-based system of the technique has been experimentally demonstrated, there had been the problem that the phase difference of two phase-shifted holograms had been changed by the extinction ratio of the micropolarizer array attached to the image sensor used in the system. To improve the performance of the system, we established and formulated an algorithm for compensating the phase-shift error. Accurate spatial phase-shifting interferometry in the system can be conducted by the algorithm regardless of phase-shift error due to the extinction ratio. By the numerical simulation, the proposed algorithm was capable of reducing the root mean square errors of the reconstructed image by 1/4 and 1/5 in amplitude and phase, respectively. Also, the algorithm was experimentally demonstrated, and the experimental results showed that the system employing the proposed algorithm suppressed the conjugate image, which slightly appeared in the image reconstructed by the system not employing the algorithm, even when the extinction ratio was 10:1. Thus, the effectiveness of the proposed algorithm was numerically and experimentally verified. 相似文献
100.
Kobayashi M Ohtsuka K Tamura Y Tomizawa S Kamijo K Iwakoshi K Kageyama Y Nagayama T Takano I 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2011,52(2):121-129
A survey of pesticide residues in 595 imported frozen products on the Tokyo market from April 1989 to March 2008 was carried out. Forty three kinds of pesticides, including organophosphorus, organochlorine, carbamate, pyrethroid and others, were detected between levels of trace (below 0.01 ppm) and 4.6 ppm from 162 samples. Chlorpyrifos, cypermethrin and omethoate were frequently detected in green vegetables (komatsuna leaf and spinach), cypermethrin and methamidophos were detected in pods and seeds (green soybean and string pea), chlorpropham (CIPC) was detected in potato, and captan and carbaryl were detected in berries (blueberry, raspberry and strawberry). The hydrophilic pesticide methamidophos was detected in flesh of lychee. Residue levels of these pesticides were calculated as between less than 0.5% and 30% of their ADI values according to the daily intake of frozen products. Therefore, these frozen products should be safe when they were eaten in customary amounts. 相似文献