全文获取类型
收费全文 | 4949篇 |
免费 | 93篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 174篇 |
综合类 | 2篇 |
化学工业 | 839篇 |
金属工艺 | 114篇 |
机械仪表 | 109篇 |
建筑科学 | 99篇 |
矿业工程 | 1篇 |
能源动力 | 102篇 |
轻工业 | 395篇 |
水利工程 | 26篇 |
石油天然气 | 7篇 |
无线电 | 522篇 |
一般工业技术 | 854篇 |
冶金工业 | 1349篇 |
原子能技术 | 116篇 |
自动化技术 | 340篇 |
出版年
2023年 | 17篇 |
2022年 | 34篇 |
2021年 | 71篇 |
2020年 | 43篇 |
2019年 | 47篇 |
2018年 | 57篇 |
2017年 | 41篇 |
2016年 | 67篇 |
2015年 | 42篇 |
2014年 | 83篇 |
2013年 | 225篇 |
2012年 | 126篇 |
2011年 | 203篇 |
2010年 | 136篇 |
2009年 | 168篇 |
2008年 | 173篇 |
2007年 | 148篇 |
2006年 | 164篇 |
2005年 | 139篇 |
2004年 | 135篇 |
2003年 | 149篇 |
2002年 | 131篇 |
2001年 | 99篇 |
2000年 | 90篇 |
1999年 | 138篇 |
1998年 | 493篇 |
1997年 | 341篇 |
1996年 | 254篇 |
1995年 | 135篇 |
1994年 | 131篇 |
1993年 | 144篇 |
1992年 | 61篇 |
1991年 | 58篇 |
1990年 | 60篇 |
1989年 | 54篇 |
1988年 | 49篇 |
1987年 | 32篇 |
1986年 | 53篇 |
1985年 | 58篇 |
1984年 | 39篇 |
1983年 | 41篇 |
1982年 | 39篇 |
1981年 | 44篇 |
1980年 | 40篇 |
1979年 | 27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5049条查询结果,搜索用时 15 毫秒
991.
Yoshifuru Mitsui Keiichi Koyama Kazuo Watanabe 《Science and Technology of Advanced Materials》2009,10(1)
A system was developed measuring x-ray powder diffraction in high magnetic fields up to 5 T and at temperatures from 283 to 473 K. The stability of the temperature is within 1 K over 6 h. In order to examine the ability of the system, the high-field x-ray diffraction measurements were carried out for Si and a Ni-based ferromagnetic shape-memory alloy. The results show that the x-ray powder diffraction measurements in high magnetic fields and at high temperatures are useful for materials research. 相似文献
992.
Katsuyoshi Kondoh Junko Umeda Ryuzo Watanabe 《Materials Science and Engineering: A》2009,499(1-2):440-444
The cavitation erosion resistance of P/M aluminum alloy sintered composite with AlN dispersoids, prepared via the in situ synthesis and the conventional premixing process, was evaluated by using a magnetostrictive-vibration type equipment. In situ synthesized AlN particles were effective for the improvement of the erosion resistance of the composite because of their good bonding with the aluminum matrix. The additive AlN by the premixing process were easily detached from the specimen surface due to the insufficient coherence with the matrix, and caused the poor resistance. The cavitation resistance also depended on the porosity of the sintered composite. The continuously opened pores accelerated the wear phenomena by the cavitation due to the high pressure attack on the primary particle boundaries of sintered materials in the collapse of the bubbles. 相似文献
993.
Liwei Lin Hideo Watanabe Masayoshi Fuji Minoru Takahashi 《Advanced Powder Technology》2009,20(2):185-189
Zinc oxide with a diversity of well-defined morphologies was synthesized via a simple aqueous solution route by decomposing ZnxOy(OH)z precursor at suitable reaction conditions. Flower-like ZnO composed of rods was obtained by treating ZnxOy(OH)z precursor in the reaction solution at 90 °C for 6 h. The precipitate of layer-like ZnxOy(OH)z precursor was decomposed by drying at 90 °C for 24 h in air, resulting in the formation of ZnO microtubes. 相似文献
994.
A novel vertical submerged membrane bioreactor (VSMBR) composed of anoxic and oxic zones in one reactor was developed in an attempt to reduce the problems concerning effective removal of pollutants from synthetic wastewater including glucose as a sole carbon source as well as membrane fouling. The optimal volume ratio of anoxic zone/oxic zone was found as 0.6. The desirable internal recycle rate and hydraulic retention time (HRT) for effective nutrient removal were 400% and 8h, respectively. Under these conditions, the average removal efficiencies of total nitrogen (T-N) and total phosphorus (T-P) were 75% and 71%, respectively, at the total chemical oxygen demand (T-COD)/T-N ratio of 10. In addition, the VSMBR showed high specific removal rates of nitrogen and phosphorus while the biomass growth yield from the reactor was about 20% of the conventional activated sludge process. 相似文献
995.
M.WATANABE M.YANAGIHARA T.EJIMA M.TOYODA Y.KONDO T.HATANO T.TSURU M.YAMAMOTO 《核技术(英文版)》2005,16(3):129-138
Microscopes in vacuum ultraviolet and soft X-ray regions using a normal incidence type of Schwarzschild objective are reviewed. The objective consists of a concave mirror and a convex mirror coated with a high reflectance multilayer, having a large numerical aperture comparing with other objectives. The microscopes have been used to diagnose inertia-confinement-fusion plasmas, and to investigate small samples or microstructures of inorganic and organic materials by imaging them using laboratory light sources. Synchrotron radiation has been also used to obtain a microbeam for a photoelectron scanning microscope with a spatial resolution of 0.1 μm. The structure and performance of two laboratory microscopes developed at Tohoku University are demonstrated. One of them is a soft X-ray emission imaging microscope, An image of an artificial pattern made of W and SiO2 on Si wafer by focusing Si L emission was presented, The other is an ultraviolet photoelectron scanning microscope using a He (helium) gas discharge lamp. The valence band spectra of a microcrystal of FeWO4 were presented, Furthermore other applications such as demagnifying optics for lithography and optics to gather fluorescence for emission spectroscopy are introduced. 相似文献
996.
Norihiko Shinomiya Toshio Koide Hitoshi Watanabe 《International Journal of Circuit Theory and Applications》2001,29(4):367-379
This paper presents a new circuit theoretical concept based on the principal partition theorem for distributed network management focusing on loops of an information network. To realize a simple network management with the minimum number of local agents, namely the topological degrees of freedom of a graph, a reduced loop agent graph generated by contracting the minimal principal minor is proposed. To investigate the optimal distribution of the loop agents, a theory of tie‐set graph is proposed. Considering the total processing load of loop agents, a complexity of a tie‐set graph is introduced to obtain the simplest tie‐set graph with the minimum complexity. As for the simplest tie‐set graph search, an experimental result shows that the computational time depends heavily on the nullity of the original graph. Therefore, a tie‐set graph with the smallest nullity is essential for network management. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
997.
Photosensitivity in a perfluoropolymer (CYTOP) optical fibre is investigated. Significant diffraction has been observed from transmission gratings made from the fibre. A maximum diffraction efficiency of 1.6% has been achieved, corresponding to an index change ≃3×10-4. The study demonstrates for the first time the existence of significant photosensitivity and the feasibility of writing a Bragg grating in a CYTOP fibre 相似文献
998.
Masaru Watanabe Makoto Mochiduki Shuhei Sawamoto Tadafumi Adschiri Kunio Arai 《The Journal of Supercritical Fluids》2001,20(3):2612
In this study, we show the results of partial oxidation experiments of n-hexadecane (n-C16) and polyethylene (PE) in supercritical water (SCW). The experiments were carried out at 673 or 693 K of reaction temperature and 5 or 30 min of reaction time using a 6 cm3 of a batch type reactor. Water density ranged from 0.1 to 0.52 g/cm3 (water pressure: 20–40 MPa). The loaded amount of oxygen was set to 0.3 of the ratio of oxygen atom to carbon atom. Some experiments were made using CO instead of oxygen for the partial oxidation of n-C16 and PE to explore the effect of water gas shift reaction. In the results of partial oxidation of n-C16, the yield of CO and some compounds containing oxygen atoms, such as aldehydes and ketones increased with increasing water density. Moreover, 1-alkene/ n-alkane ratio in the products decreased with increasing water density. The 1-alkene/n-alkane ratio was lower than that of pyrolysis in SCW. Also for the case of PE experiments, in dense SCW (0.42 g/cm3), the 1-alkene/n-alkane ratio in partial oxidation was lower than that in SCW pyrolysis. In the case of CO experiments for n-C16 and PE, 1-alkene/n-alkane ratio was a little lower than that of pyrolysis in SCW. These results show that the yield of n-alkane, which is a hydrogenated compound, was higher through water gas shift reaction in SCW and also through partial oxidation in SCW. Therefore, these results suggest the possibility of hydrogenation of hydrocarbon through partial oxidation followed by the water gas shift reaction. 相似文献
999.
Open dumping site in Asian developing countries: a potential source of polychlorinated dibenz-p-dioxins and polychlorinated dibenzofurans 总被引:1,自引:0,他引:1
Nguyen HM Tu BM Watanabe M Kunisue T Monirith I Tanabe S Sakai S Subramanian A Sasikumar K Pham HV Bui CT Tana TS Prudente MS 《Environmental science & technology》2003,37(8):1493-1502
Open landfill dumping areas for municipal wastes in Asian developing countries have recently received particular attention with regard to environmental pollution problems. Because of the uncontrolled burning of solid wastes, elevated contamination by various toxic chemicals including dioxins and related compounds in these dumping sites has been anticipated. In this study, concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) were determined in soils from dumping sites in the Philippines, Cambodia, India, and Vietnam. Residue concentrations of PCDD/Fs and coplanar PCBs in dumping site soils were apparently greater than those in soils collected in agricultural or urban areas far from dumping sites, suggesting that dumping sites are potential sources of PCDD/Fs and related compounds. Observed PCDD/F concentrations in soils from dumping sites in the Philippines and Cambodia were comparable or higher than those reported for dioxin-contaminated locations in the world (e.g., near the municipal waste incinerators and open landfill dumping sites). Homologue profiles of PCDD/Fs in dumping site soils from the Philippines and, to a lesser extent, from Cambodia and India reflected patterns of samples representing typical emissions, while profiles of agricultural or urban soils were similar to those of typical environmental sinks. This result suggests recent formation of PCDD/Fs in dumping site areas and that open dumping sites are a potential source of dioxins in Asian developing countries. Uncontrolled combustions of solid wastes by waste pickers, generation of methane gas, and low-temperature burning can be major factors for the formation of dioxins in dumping sites. Elevated fluxes of PCDD/Fs to soils in dumping sites were encountered in the Philippines, Cambodia, India, and Vietnam-Hanoi, and these levels were higher than those reported for other countries. Considerable loading rates of PCDD/Fs in the dumping sites of these countries were observed, ranging from 20 to 3900 mg/yr (0.12-35 mg TEQ/yr). PCDD/F concentrations in some soil samples from the Philippines, Cambodia, India, and Vietnam-Hanoi exceeded environmental guideline values, suggesting potential health effects on humans and wildlife living near these dumping sites. The estimated intakes of dioxins via soil ingestion and dermal exposure for children were higher than those for adults, suggesting greater risk of dioxin exposure for children in dumping sites. To our knowledge, this is the first comprehensive study on PCDD/Fs contamination in open dumping sites of Asian developing countries. On the basis of the result of this study, we have addressed a new environmental issue that open dumping sites are potential sources of PCDD/Fs and related compounds, and dioxin contamination in dumping sites may become a key environmental problem in developing countries. 相似文献
1000.
Goto S Takahashi H Kawasaki S Kimura B Fujii T Nakatsuji M Watanabe I 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2004,45(1):25-28
To simplify the labor-intensive conventional routine testing of samples to detect Leuconostoc at a meat processing plant, we developed polymerase chain reaction (PCR) primers specific for Leuconostoc from 16S rRNA gene sequences. These primers did not detect other common lactic acid bacteria such as Lactobacillus plantarum, Lact. sake, Lact. fermentum, Lact. acidophilus and Weissella viridescens. PCR with this primer detected all Leuconostoc species tested (Leu. mesenteroides subsp. mesenteroides, Leu. pseudomesenteroides, Leu. carnosum, Leu. lactic, Leu. citreum, Leu. amelibiosum, Leu. gelidum), except for Leu. fallax, and no other lactic acid bacteria on agarose gel electrophoresis. The method could identify areas contaminated with Leuconostoc in a large-scale industrial meat processing plant. Of 69 samples analyzed, 34 were positive for Leuconostoc according to the conventional culture method (isolation of LAB producing dextran) and PCR, whereas 29 were negative according to both. Six samples were culture-negative but positive by PCR. No false negative results were generated by PCR. The method is rapid and simple, is useful for routinely monitoring areas contaminated with Leuconostoc in meat processing plants, and could help to prevent the spoilage of meat products. 相似文献