全文获取类型
收费全文 | 2127篇 |
免费 | 47篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 94篇 |
化学工业 | 469篇 |
金属工艺 | 71篇 |
机械仪表 | 35篇 |
建筑科学 | 48篇 |
能源动力 | 63篇 |
轻工业 | 148篇 |
水利工程 | 3篇 |
无线电 | 281篇 |
一般工业技术 | 318篇 |
冶金工业 | 399篇 |
原子能技术 | 104篇 |
自动化技术 | 147篇 |
出版年
2023年 | 11篇 |
2022年 | 29篇 |
2021年 | 34篇 |
2020年 | 29篇 |
2019年 | 44篇 |
2018年 | 37篇 |
2017年 | 37篇 |
2016年 | 51篇 |
2015年 | 35篇 |
2014年 | 49篇 |
2013年 | 124篇 |
2012年 | 78篇 |
2011年 | 113篇 |
2010年 | 99篇 |
2009年 | 84篇 |
2008年 | 89篇 |
2007年 | 74篇 |
2006年 | 89篇 |
2005年 | 59篇 |
2004年 | 67篇 |
2003年 | 67篇 |
2002年 | 56篇 |
2001年 | 42篇 |
2000年 | 35篇 |
1999年 | 47篇 |
1998年 | 151篇 |
1997年 | 79篇 |
1996年 | 76篇 |
1995年 | 41篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 31篇 |
1991年 | 19篇 |
1990年 | 20篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 21篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1972年 | 3篇 |
排序方式: 共有2180条查询结果,搜索用时 15 毫秒
61.
Noriyuki Hara Shuichi Nakamura Yasuhiro Funahashi Norio Shibata 《Advanced Synthesis \u0026amp; Catalysis》2011,353(16):2976-2980
The organocatalytic enantioselective decarboxylative addition of malonic acids half thioesters to isatins using a squaramide catalyst afforded the products with high enantioselectivity. These products are key intermediates in the synthesis of 3‐substituted 3‐hydroxy‐2‐oxindole derivatives. The first enantioselective synthesis of (−)‐flustraminol B has been accomplished. 相似文献
62.
Mutsuyo Ohara Shuichi Nakamura Norio Shibata 《Advanced Synthesis \u0026amp; Catalysis》2011,353(18):3285-3289
A direct three‐component reaction of aldehydes, amines and diaryl phosphites was catalyzed by a zinc(II) complex of 1,3‐bis(imidazolin‐2‐ly)pyridine (pybim) giving the corresponding α‐aminophosphonates in good yield with good enantioselectivity. The reaction was applied to a wide variety of aromatic aldehydes to give products with excellent yields (up to 99%) and enantiomeric excesses (up to 93% ee). 相似文献
63.
Tomohiro Isogai Kazuhiro Hirooka Tetsuro Tojo Hitoshi Takebayashi Morihiro Saito Minoru Inaba Akimasa Tasaka 《Electrochimica acta》2011,56(12):4425
Metal fluoride added carbon anodes treated by pre-electrolysis were investigated for electrolytic production of nitrogen trifluoride (NF3) in molten NH4F·KF·4HF at 100 °C. The conditions for pre-electrolysis were first optimized using a graphite sheet anode as a model anode. The formation of fluorine-graphite intercalation compounds (fluorine-GICs) with semi-covalent C–F bonds, (CxF)n, on the MgF2 and CaF2 added carbon anode surface was accelerated by pre-electrolysis at potentials less than 4.0 V. Critical current densities (CCD) on the MgF2 added carbon anodes pre-electrolyzed under various conditions were determined, and the highest CCD was 290 mA cm−2 obtained for that pre-electrolyzed at 3.5 V for 500 C cm−2. This anode was successfully used in the electrolysis at 100 mA cm−2 for 290 h and the maximum NF3 current efficiency was 55%. From these results, it was concluded that the metal fluoride added carbon anode treated by pre-electrolysis has a high potential for electrolytic production of NF3 at higher current density. 相似文献
64.
Hirobumi Shibata Taku Ogura Keishi Nishio Hideki Sakai Masahiko Abe Kazuaki Hashimoto Mutsuyoshi Matsumoto 《SILICON》2011,3(3):139-143
Large-pore mesoporous silica particles were synthesized through a solvent evaporation process using hydrophobic fumed silica
particles and tetraethyl orthosilicate (TEOS) as silica sources. The solvent evaporation of an ethanol solution of fumed silica
particles, TEOS, HCl and triblock copolymer (F127) resulted in mesoporous silica particles with pores with sizes of about
7 nm. In addition, the interplanar spacing of the mesoporous silica particles can be controlled by changing the solvent evaporation
temperatures. 相似文献
65.
Fumihide Shiraishi Naoya Kamikariya Yuichiro Shibata 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(6):852-857
BACKGROUND: The authors (Chem Eng J 148, 234 (2009)) previously demonstrated the excellent performance of a photocatalytic reactor with a parallel array of nine light sources. To enhance the possibility of practical application of this reactor, the present work explores the use of a PET (polyethylene terephthalate) sheet as a new cheap material to support TiO2, as an alternative to glass tubes. A method of coating the hydrophobic PET sheet with a TiO2 film using an aqueous coating solution is investigated and the performance of the TiO2‐PET sheet prepared evaluated. RESULTS: The affinity of the coating solution for the PET sheet is greatly enhanced by addition of 0.01% (w/w) nonionic surfactant (polyoxyethylene lauryl ether). A relatively uniform thin TiO2 film is formed on the entire surface of the PET sheet by applying the coating solution to the PET sheet and drying it at 100 °C. Decomposition experiments of gaseous HCHO indicate that the photocatalytic activity, although initially low, is increased with repeated use. This is because surfactant molecules added interfere initially with the decomposition of HCHO. After their decomposition, the TiO2–PET sheet decomposes HCHO at almost the same rate as does the TiO2–glass tube. CONCLUSION: The photocatalytic reactor with a parallel array of nine light sources can utilize a PET sheet as TiO2 support with a reduction in material cost. Copyright © 2011 Society of Chemical Industry 相似文献
66.
High oleic acid oil suppresses lung tumorigenesis in mice through the modulation of extracellular signal-regulated kinase cascade 总被引:2,自引:0,他引:2
Yamaki T Yano T Satoh H Endo T Matsuyama C Kumagai H Miyahara M Sakurai H Pokorny J Shin SJ Hagiwara K 《Lipids》2002,37(8):783-788
This study was undertaken to estimate the effect of dietary high oleic acid oil (OA) on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone
(NNK)-induced lung tumorigenesis in mice. Diet containing 10% oil was fed to mice through experimental periods. On day 30
after NNK injection (100 mg/kg body weight, i.p.), the treatment increased the level of prostaglandin E2 (PGE2) as well as proliferating cell nuclear antigen, a marker of cell proliferation in a high linoleic acid oil (LA)-fed group
but not in an OA-fed group. The NNK treatment also induced the activation of an extracellular signal-regulated kinase (Erk)
cascade (Erk, Mek and Raf-1) in an LA-fed group. On the other hand, OA feeding abolished the NNK-induced activation of the
Erk cascade. In conjugation with these events, OA feeding reduced lung tumor incidence and tumor multiplicity (percentage
of mice with tumors) in mice compared with LA feeding at the 20th experimental week. These results suggest that OA suppresses
lung tumorigenesis and that this suppression is correlated with the inhibition of PGE2 production and inactivation of the Erk cascade. 相似文献
67.
The radical polymerization of N‐isopropylacrylamide was carried out in toluene at low temperatures in the presence of silyl alcohols, such as triethylsilanol. Poly(N‐isopropylacrylamide) with a racemo dyad content of 75% was obtained at ? 80 °C with a 4:1 triethylsilanol to monomer ratio loading. NMR analysis suggests that the mechanism for syndiotactic induction, in the presence of silyl alcohols, may be similar to that observed with alkyl alcohols. In this case, a 1:2 complex formation, via hydrogen bonding interactions, leads to the induction of syndiotactic specificity. Copyright © 2012 Society of Chemical Industry 相似文献
68.
Yuji Tatemoto Yoshiyuki Bando Koji Oyama Keiji Yasuda Masaaki Nakamura Yasuhiro Sugimura Masahito Shibata 《Drying Technology》2001,19(7):1287-1303
The effects of operational conditions on the drying performance in closed superheated steam drying were examined theoretically and experimentally. The vapor generated from the sample was circulated in the drying chamber. In the theoretical analysis, the replacement of air with vapor in drying chamber and the convective vapor transfer in sample were considered. At the start of drying, the drying chamber was filled with air. As the drying proceeded, the air was replaced with the vapor generated from sample. The calculated results explained the characteristics of experimental data. The pore diameter of sample had little effect on the drying characteristics. During the internal evaporation period, the evaporation occurred in the narrow zone, which moved from the surface to the bottom of sample. The convective vapor transfer in sample had a significant influence on the drying performance. The excess increments in temperature and velocity of drying gas hardly contributed to shortening the drying time. 相似文献
69.
The reaction of pyrogallol (PG) and vanillin (VN), both of which are derived from plant resources, in the presence of p‐toluenesulfonic acid gave PG–VN calixarene (PGVNC) mainly composed of guaiacyl pyrogallol[4]arene. After sorbitol polyglycidyl ether (SPE) was mixed with PGVNC in tetrahydrofuran at an optimized epoxy/hydroxy ratio 1/2.65, the obtained SPE/PGVNC solution was mixed with wood flour (WF), prepolymerized at 150°C, and subsequently compressed at 190°C for 3 h to give SPE–PGVNC/WF biocomposites with WF content 0–20 wt%. The tan δ peak temperature of SPE–PGVNC was 148.1°C, which was much higher than that of the SPE cured with petroleum‐based phenol novolac (SPE–PN) at an optimized epoxy/hydroxy ratio 1/1. Although tan δ peak temperature slightly decreased with increasing WF content, the storage moduli of the SPE–PGVNC/WF biocomposites in the rubbery state at more than 150°C were much higher than those of SPE–PGVNC and SPE–PN. Also, the tensile modulus and strength for SPE–PGVNC/WF increased with increasing WF content. Field emission‐scanning electron microscopy analysis of the biocomposites revealed that WF is tightly incorporated into the crosslinked epoxy resins. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers 相似文献
70.
This study investigated whether hydrogels comprising hydrophilic cationic polymers have similar bactericidal effects. Bacteria were seeded on hydrogels and agar and their viability was assessed with time. Cationic hydrogels displayed bactericidal effects upon long-term bacterial contact. Furthermore, we assessed the areal density of cationic monomer unit of the cationic hydrogels, water content, and the initial elastic modulus. We examined correlations between each factor and bacterial death ratios; consequently, the bacterial death ratios were strongly correlated with the areal density of cationic hydrogel monomers. Elastic energy (Wel) generated at the cytomembrane ion-binding region and the cationic hydrogel and the cytomembrane interfacial energy (Wf) were estimated; consequently, Wel exceeded Wf at higher contact areas. The cationic hydrogel may extract cytomembranes with a reasonable adsorption area. Therefore, cationic hydrogels may be used as probes for ultrasonic echo to sterilize medical equipment. 相似文献