全文获取类型
收费全文 | 687篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 75篇 |
综合类 | 1篇 |
化学工业 | 160篇 |
金属工艺 | 12篇 |
机械仪表 | 13篇 |
建筑科学 | 9篇 |
能源动力 | 9篇 |
轻工业 | 33篇 |
水利工程 | 2篇 |
无线电 | 53篇 |
一般工业技术 | 109篇 |
冶金工业 | 167篇 |
原子能技术 | 39篇 |
自动化技术 | 24篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 13篇 |
2020年 | 4篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 8篇 |
2014年 | 12篇 |
2013年 | 28篇 |
2012年 | 15篇 |
2011年 | 13篇 |
2010年 | 20篇 |
2009年 | 29篇 |
2008年 | 23篇 |
2007年 | 28篇 |
2006年 | 17篇 |
2005年 | 14篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 17篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 54篇 |
1997年 | 36篇 |
1996年 | 27篇 |
1995年 | 19篇 |
1994年 | 27篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 18篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1974年 | 5篇 |
排序方式: 共有706条查询结果,搜索用时 93 毫秒
641.
A scanning ion-conductance microscope (SICM) with a vibrating probe has been recently developed (vSICM). In this system, the amplitude of the AC ionic current is detected by using a lock-in amplifier locked to the vibration frequency of the probe. Such a scheme allows for a better control of the tip position because the AC ionic current is more sensitive to the probe-surface distance than the DC ionic current used previously. In this paper, we demonstrate the utility of this technique to the imaging of topographically rough specimens and high-resolution imaging over selected small areas. We also show that it is possible to record the DC ionic current simultaneously during the scan, which can reveal additional information not apparent in the images obtained with the AC ionic current. 相似文献
642.
We have reacted diaminomaleonitrile with pyruvic aldehyde or pyruvic acid to produce 2, 3-dicyano-5-methylpyrazine and 2, 3-dicyano-6-hydroxy-5-methylpyrazine. Although these compounds showed no fluorescence, condensation with arylaldehyde yielded red to violet coloured styryl-type dyes with strong orange to red fluorescence. We have investigated the tautomerism and fluorescent properties of these new pyrazine dyes by means of computer simulation, and have also investigated their spectral properties using molecular orbital and molecular mechanics calculation techniques. These studies revealed the dyes to have strong intramolecular charge-transfer chromophoric systems and high solvatochromism both in absorption and fluorescence spectra. 相似文献
643.
Y Iwamoto 《Canadian Metallurgical Quarterly》1999,4(1):54-65
Alterations in [Hb], which are mediated through changes in arterial oxygen content, and alterations in BV, which are mediated through changes in cardiac output (Q), have a significant effect on both VO2max and aerobic performance. If BV is held constant, a decrease in [Hb] (anaemia) causes a decrease in VO2max and aerobic performance, while an increase in [Hb] (blood doping) causes an increase in VO2max and aerobic performance. If [Hb] is held constant, an increase in BV can cause and increase in both VO2max and aerobic performance, while a decrease in BV can cause a decrease in VO2max and aerobic performance. In addition, an increase in BV can compensate for moderate reductions in [Hb] through increase in Q, allowing VO2max to remain unchanged or even increase. Also, a large portion of the difference in the enhanced cardiovascular function of endurance athletes is due to their high BV and the resultant enhancement of diastolic function. Hence, optimizing both [Hb] and BV is a very important consideration for endurance performance. 相似文献
644.
645.
Akiyoshi Tanaka Chika Nakagawa Kazuko Kodaira Keishi Senoo Hitoshi Obata 《Journal of Bioscience and Bioengineering》1999,88(6):664
Steady-state kinetic parameters for the hydrolysis of cellooligosaccharides by almond β-glucosidase were evaluated at pH 5.0 and 25°C in relation to the subsite theory (K. Hiromi, Biochem. Biophys. Res. Commun., 40, 1–6, 1970). The value of k0/Km decreased monotonously with increasing degree of polymerization (DP) of the substrates (DP = 2–6). Also, the Km and k0 values for cellotriose were smaller than those for cellobiose. These DP dependencies differ from those of most amylases and glucosidases studied so far, to which the subsite theory has been successfully applied. The subsite parameters could not be consistently obtained, which suggests that one or both of the two basic assumptions of the subsite theory might not be applicable to the hydrolysis of cellooligosaccharides by the enzyme. That is, the intrinsic rate of the hydrolysis may depend on the DP and/or there may be interaction between subsites for binding the glucose residues of a substrate. 相似文献
646.
Shoji Furukawa Hiroshi Iino Tomohisa Iwamoto Koudai Kukita Shoji Yamauchi 《Thin solid films》2009,518(2):526-529
Dye-sensitized solar cells are expected to be used for future clean energy. Recently, most of the researchers in this field use Ruthenium complex as dye in the dye-sensitized solar cells. However, Ruthenium is a rare metal, so the cost of the Ruthenium complex is very high. In this paper, various dye-sensitized solar cells have been fabricated using natural dye, such as the dye of red-cabbage, curcumin, and red-perilla. As a result, it was found that the conversion efficiency of the solar cell fabricated using the mixture of red-cabbage and curcumin was about 0.6% (light source: halogen lamp), which was larger than that of the solar cells using one kind of dye. It was also found that the conversion efficiency was about 1.0% for the solar cell with the oxide semiconductor film fabricated using polyethylene glycol (PEG) whose molecular weight was 2,000,000 and red-cabbage dye. This indicates that the cost performance (defined by [conversion efficiency]/[cost of dye]) of the latter solar cell (dye: red-cabbage) is larger by more than 50 times than that of the solar cell using Ruthenium complex, even if the effect of the difference between the halogen lamp and the standard light source is taken into account. 相似文献
647.
To prepare silica beads covered with a lysozyme‐imprinted polymer layer, we polymerized acrylamide and acrylic acid or acrylamide and N,N‐dimethylaminopropylacrylamide with (NH4)2S2O8 in a phosphate buffer containing the lysozyme, surface‐modified silica beads, and crosslinkers; the result was the formation of a polymer layer with a lysozyme recognition site on the silica‐bead surface. By quantitative analysis of the supernatant of the solution containing the silica beads, we confirmed that modified silica beads, in contrast to unmodified silica beads, can selectively adsorb lysozymes. The process of binding and releasing the lysozyme to and from the modified silica beads can be repeated several times without degradation of the rebinding ability. A quartz‐crystal microbalance sensor fabricated with a molecularly imprinted polymer layer with a lysozyme recognition site was prepared. When a lysozyme aqueous solution was added to the solution in which the sensor was immersed, a high level of sensitivity and response was observed. High selectivity was also demonstrated by tests with other protein solutions. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3378–3387, 2001 相似文献
648.
Hydrothermal Treatment of a Silica Sand Complex with Lime 总被引:1,自引:0,他引:1
Osamu Watanabe Kazuko Kitamura Hiroki Maenami Hideki Ishida 《Journal of the American Ceramic Society》2001,84(10):2318-2322
The feasibility of using relatively low-purity silica as the starting material for hydrothermal solidification was investigated from the consideration of effective utilization of natural resources. Hydrothermal solidification was performed at 140°–180°C for periods ranging from 2 to 40 h using a mixture of 80% silica sand (containing 67% quartz, 22% clay minerals (mica, clinochlore, and kaolinite), and 7% feldspar) and 20% Ca(OH)2 . Within the range of experimental conditions, the flexural strength of the solidified bodies increased with increased treatment temperature and treatment time, reaching values of up to 20 MPa. The flexural strength was proportional to the amount of, but independent of the type of, reaction products. Hydrogarnet and C-S-H were formed in the initial stages of the reaction; the amount of these phases tended to decrease, and 1.1 nm tobermorite formed as the reaction further progressed. These results indicated that hydrogarnet and C-S-H were precursors of 1.1 nm tobermorite. 相似文献
649.
Tubular carbon membranes were fabricated by the blending of BTDA-TDI/MDI (P84) polyimide with nanocrystalline cellulose in a controlled pyrolysis process, specifically the pyrolysis environment (He, Ar, and N2) and the thermal soak time (30–120 min). The carbon membrane layer on a tubular support is converted to carbon matrix at 800 °C with a heating rate of 3 °C min−1. The effects of these controlled pyrolysis conditions on the gas permeation properties have been investigated. The results revealed that the pyrolysis under Ar gas environment at 120 min of thermal soak time have the best gas permeation performance with the highest CO2/CH4 selectivity of 68.2 ± 3.3 and CO2 permeance of 213.6 ± 2.2 GPU. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46901. 相似文献
650.
The increasingly recognized applicability of infrared thermography has caused developments of remote-sensing diagnoses for various engineering applications. A significant advantage of this technique is that we can diagnose invisible defects nondestructively and safely. For maintaining and managing various structures satisfactorily, it is very important to detect many kinds of invisible defects such as separation, cavity, inclusion and so on. Although the infrared thermography for NDT and E has therefore been examined extensively, few fundamental investigations have addressed the numerical computation to evaluate the detection mechanism and the quantitative limit under various conditions. It is important to discuss them theoretically with the aid of the appropriate numerical computation. In this paper, therefore, we certify them using a series of fundamental numerical computation with the aid of the concerned experimental investigation using the infrared thermography. From the numerical and experimental investigations, the effects of defect's depth and size on the detection are elucidated. In addition to the fact, it is obvious that the applicability of the present NDT and E depends on a heating condition and a relative difference of thermophysical property between the defect and its surrounding. 相似文献