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排序方式: 共有891条查询结果,搜索用时 218 毫秒
881.
Atmospheric nanoparticles (<0.050 microm) have caused great concern recently due to their potential to affect human health. However, little is known about the chemical composition, sources, and atmospheric behavior of atmospheric nanoparticles. Although gas chromatography/mass spectrometry (GC/MS) after solvent extraction is a commonly used and powerful method for the identification of nonpolar organic compounds in particles, solvent-extraction methods are difficult to apply to nanoparticles because nanoparticles are present in small masses in spite of their high number concentrations. Therefore, we made an attempt to apply thermal desorption-GC/MS (TD-GC/MS), which was expected to be more sensitive than solvent-extraction methods, to atmospheric nanoparticles. A commercial pyrolyzer was used for TD. Prior to the application, the optimum TD-GC/MS conditions for atmospheric particles and diesel exhaust particles (DEP) collected on filters were investigated. Various TD parameters, including desorption time and temperature, were investigated using these test samples and a n-alkanes standard solution. The optimum TD conditions were as follows: ramped desorption from 50 degrees C to 450 degrees C at 50 degrees C min(-1) and then hold for 2 min. Desorption was incomplete at temperatures of 250 degrees C or lower, and considerable pyrolysis occurred at temperatures of 550 degrees C or higher. The TD-GC/MS performance, including the linearity of the calibration curves, repeatability, detection and quantification limits, and sample recovery, under the optimized conditions was evaluated for n-alkanes. It was found that the TD-GC/MS could be applied to extremely small amount of particles (e.g., 5 microg for DEP). The TD-GC/MS was applied to the size-resolved particles, including the nanoparticle fraction (0.0290-0.0580 microm), from roadside atmosphere, and the concentrations of C18-C33 n-alkanes in the particles were determined. The chromatogram pattern of the roadside 0.102-0.163 microm (major size range for DEP) particles was similar to that of the DEP sample. The chromatogram pattern of the roadside nanoparticles was similar to that of diesel lubricating oil, although the proportion of less volatile compounds was slightly larger in the nanoparticles. It is suggested that lubricating oil strongly contributed to the nonpolar organic composition of the roadside nanoparticles, and that more volatile organic compounds in the nanoparticles evaporated in the atmosphere. It was shown that the TD-GC/MS is effective for characterization of atmospheric nanoparticles. 相似文献
882.
883.
Kobayashi S Kawai W Wakayama S 《Journal of materials science. Materials in medicine》2006,17(11):1089-1093
Hydroxyapatite (HA) is known to be biocompatible and osteoconductive, and can be synthesized chemically. The objective of
the present study is to clarify the effect of pressure during sintering on the mechanical properties of HA. HA was sintered
using a hot press system at a uniaxial pressure ranging from 7.81 to 62.5 MPa at a maximum temperature of 1200∘C with a heating rate of 10∘C/min. The density of the HA increased with increasing pressure and peaked at the sintering pressure of 31.2 MPa. Four-points
bending tests and fracture toughness measurements with indentation method were conducted to clarify the effect of sintering
pressure. Bending strength decreased at the pressure > 31.2 MPa. This result indicates that residual stress generated during
sintering process became larger with increasing pressure. Fracture toughness were also lower with high density HA. 相似文献
884.
Jones matrix imaging of biological samples by a polarization-sensitive Fourier-domain optical coherence tomography has been demonstrated using a two-dimensional CCD camera to obtain two spectra corresponding to the orthogonal polarization components simultaneously. The measurement results of a quarter-wave plate are compared between the two incident polarization sets, H-V linear and R-L circular polarization. Jones matrix imaging of the bovine tendon is demonstrated. Measured Jones matrix images are converted to equivalent Müller matrix images. Local polarization properties are obtained by longitudinal differentiation of Jones matrix components. The layered structure of the bovine tendon and birefringence are revealed. 相似文献
885.
Kurniawan KH Lie TJ Suliyanti MM Hedwig R Pardede M Kurniawan DP Kusumoto Y Kagawa K 《Analytical chemistry》2006,78(16):5768-5773
It was proved that the analysis of deuterium can be conducted using laser-induced plasma spectroscopy. By selecting the appropriate surrounding gas, its pressure, and gating time of the detection system, it was shown that the emission lines of both hydrogen (H(alpha)) and deuterium (D(alpha)), separated by only 0.179 nm, can be fully resolved. A linear calibration curve was also obtained, indicating that this technique has the potential for quantitative analysis of deuterium. The minimum detection limit achieved in this stage of research was estimated to be 50 ppm. We have also shown that this technique can be used as a simple and rapid method for D and H analysis in solid samples. 相似文献
886.
Shota Yamamoto Hiroki Noguchi Asuka Takeda Ryosuke Arakaki Maimi Uchishiba Junki Imaizumi Saki Minato Shuhei Kamada Tomohiro Kagawa Atsuko Yoshida Takako Kawakita Yuri Yamamoto Kanako Yoshida Masafumi Kon Nobuo Shinohara Takeshi Iwasa 《International journal of molecular sciences》2022,23(15)
Polycystic ovary syndrome (PCOS) is frequently seen in females of reproductive age and is associated with metabolic disorders that are exacerbated by obesity. Although body weight reduction programs via diet and lifestyle changes are recommended for modifying reproductive and metabolic phenotypes, the drop-out rate is high. Thus, an efficacious, safe, and continuable treatment method is needed. Recent studies have shown that oxytocin (OT) reduces body weight gain and food intake, and promotes lipolysis in some mammals, including humans (especially obese individuals), without any adverse effects. In the present study, we evaluated the changes in endogenous OT levels, and the effects of acute and chronic OT administration on body weight changes, food intake, and fat mass using novel dihydrotestosterone-induced PCOS model rats. We found that the serum OT level was lower in PCOS model rats than in control rats, whereas the hypothalamic OT mRNA expression level did not differ between them. Acute intraperitoneal administration of OT during the dark phase reduced the body weight gain and food intake in PCOS model rats, but these effects were not observed in control rats. In contrast, chronic administration of OT decreased the food intake in both the PCOS model rats and control rats. These findings indicate that OT may be a candidate medicine that is efficacious, safe, and continuable for treating obese PCOS patients. 相似文献
887.
888.
介绍了自行研制的可以施加横向磁场中的垂直Bridgman法晶体生长装置,该装置磁场强度可在0-0.6T范围内连续调节,生长区温度梯度达40-70℃/cm,不同磁场强度下进行了HgCdTe晶体生长实验,通过测量分析, 轴赂和径向组分分布的变化与磁场的关系,实验结果表明,由于磁场对熔体中热对流以的作用,尤其是横向磁场怀流甩的相互作用,在一定程度上改变生长界面的形状,从而改善HgCdTe晶体径向组分分布 相似文献
889.
890.
Naoki Fujieda Shuichi Ichikawa 《IEEJ Transactions on Electrical and Electronic Engineering》2015,10(5):592-602
The instruction register file (IRF) shortens and obfuscates instruction sequences by compressing multiple instructions into a packed instruction. The IRF could improve its efficiency by parameterization, but the previously proposed parameterization techniques did not extract the similarity of instructions well. In this paper, we propose an XOR‐based parameterization to utilize the limited capacity of the IRF more efficiently. According to our evaluation, with an improved algorithm of instruction selection, our approach makes 20.2% more dynamic instructions IRF‐resident than the previous techniques. It also reduces the number of instruction fetches from the cache by 6.3% on average. We also confirmed that the hardware overhead of our parameterization was about a quarter of the previous one. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献