全文获取类型
收费全文 | 801篇 |
免费 | 17篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 43篇 |
综合类 | 2篇 |
化学工业 | 274篇 |
金属工艺 | 32篇 |
机械仪表 | 22篇 |
建筑科学 | 9篇 |
能源动力 | 39篇 |
轻工业 | 40篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 49篇 |
一般工业技术 | 156篇 |
冶金工业 | 28篇 |
原子能技术 | 60篇 |
自动化技术 | 65篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 10篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 23篇 |
2013年 | 53篇 |
2012年 | 42篇 |
2011年 | 56篇 |
2010年 | 34篇 |
2009年 | 27篇 |
2008年 | 54篇 |
2007年 | 37篇 |
2006年 | 35篇 |
2005年 | 29篇 |
2004年 | 28篇 |
2003年 | 25篇 |
2002年 | 29篇 |
2001年 | 21篇 |
2000年 | 23篇 |
1999年 | 21篇 |
1998年 | 17篇 |
1997年 | 20篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有822条查询结果,搜索用时 15 毫秒
61.
Factors that affect the efficiency of in vitro synthesis of mutant proteins that contain nonnatural amino acids were investigated. The process of the nonnatural mutagenesis consists of chemical aminoacylation of a tRNA that contains a 4-base anticodon, followed by in vitro synthesis in the presence of an mRNA that contains the corresponding 4-base codon. Detailed studies on the time courses of the synthesis revealed two major factors that suppress the yield of nonnatural mutants compared with the wild-type protein. First, a cyclic tRNA that exists as a by-product of the chemical aminoacylation inhibits the protein synthesis. Second, the very short lifetime of a tRNA aminoacylated with a nonnatural amino acid limits the protein yield. As a simple and practical way of surmounting these factors, aminoacyl tRNA was added into the in vitro system at 5 min after the start of the synthesis. The addition increased the protein yield up to the level of conventional proteins in the in vitro system. 相似文献
62.
A novel sample extraction technique for polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) analysis using microwave-heating device is developed. In this study, microwave-assisted extraction (MAE) and steam distillation techniques were combined. Desorption of the anatytes from solid matrixes was accelerated with water vapor which was generated by microwave irradiation. A sample holder in a commercial microwave extraction cell kept the sample from direct contact with the organic solvent for analytes trapping during the treatment process. Therefore, relatively clean extracts were obtained with small amount of solvents. Without any cleanup steps, the obtained extract could be analyzed with gas chromatograph/mass spectrometers (GC/MS). Six PCB congeners (PCB15, 28, 70, 101, 180, 194, 209) and three OCPs (gamma-HCH, 4,4'-DDE, 4,4'-DDD) in two marine sediment samples (a sediment collected from a bay of Kyusyu Island, Japan, and a certified reference material NIST SRM1944) were analyzed by using this microwave-assisted steam distillation (MASD) technique and another extraction method (exhaustive steam distillation, MAE, and Soxhlet extraction); and comparisons of the results are shown in this report. Although recovery yields of highly chlorinated biphenyls (PCB180, 194, 209) and relatively polar OCPs (gamma-HCH, 4,4'-DDD) were low (30-60%) compared with other analytes (PCB15, 28, 70, 101, 4,4'-DDE; recovery, 80-100%), use of isotope labeled internal standards for the MASD technique gave comparable results with the values obtained by other extraction methods and the certified values in the samples. 相似文献
63.
Kazuya Nakata Keizo Udagawa Tsuyoshi Ochiai Hideki Sakai Taketoshi Murakami Masahiko Abe Akira Fujishima 《Materials Chemistry and Physics》2011
TiO2-polydimethylsiloxane (TiO2-PDMS) composite films are prepared using the sol–gel method from a Ti(OBu)4–benzoylacetone solution containing PDMS. The prepared films are cured by irradiation with ultraviolet (UV) light. Structural changes in the films after UV irradiation are confirmed by UV–vis absorption experiments, which show that an absorption band characteristic of the benzoylacetonate chelate rings disappears. This finding is ascribed to structural changes associated with the dissociation of the chelate rings. The IR spectra of the thin films exhibit a broad absorption band after UV irradiation, indicating that a Ti–O–Ti network forms in the thin film. Contact angles are measured for the TiO2-PDMS thin films, showing wettability conversion from hydrophobic to superhydrophilic states by irradiation with oxygen plasma for 1 s. This phenomenon is explained by XPS experiments which reveal that the number of carbon atoms decreases, whereas the number of oxygen atoms increases on the surface of the TiO2-PDMS composite films. Finally, hydrophobic–superhydrophilic patterns are fabricated based on a patterned TiO2-PDMS composite film. The film displays a rapid change to superhydrophilicity over the whole film surface upon plasma irradiation for 1 s, which means that the wettability patterns are rapidly erasable. 相似文献
64.
Summary Cationic polymerization of CH2=CH-O-CH2CH2C(COOC2H5)3, a vinyl ether with three pendent esters, initiated by the HI/I2 system in toluene at –40 °C afforded living polymers with a controlled molecular weight (
= 103–104) and a narrow molecular weight distribution (
= 1.1–1.2). The number-average molecular weight of the polymers was directly proportional to monomer conversion and the monomer-to-initiator (HI) feed ratio. The polymers obtained with BF3O(C2H5)2 had a fairly high molecular weight (
105,
5 × 104) and a broad molecular weight distribution. The triester vinyl ether was similar in reactivity to alkyl counterparts and one order of magnitude more reactive than the corresponding mono- and diester vinyl ethers. 相似文献
65.
Masahiko Nakase Yuto Matsuzawa Kenji Takeshita 《Journal of Nuclear Science and Technology》2013,50(11):1317-1323
Reprocessing of spent nuclear fuels generates high-level liquid waste (HLLW) which undergoes vitrification into borosilicate glass before final geological disposal. To ensure the quality of the glass, control of the concentration of chemical species such as molybdenum (Mo), which has an adverse impact on the vitrification process, is critical. Also, zirconium (Zr) can cause crud in washing process and Zr-93 is a long-lived fission product needed to be separated. In this study, a liquid–liquid countercurrent centrifugal contactor with Taylor–Couette flow (TC contactor) was applied to practical multi-species cases. Continuous separation of Mo and Zr from a simulated HLLW with bis(2-ethylhexyl) phosphoric acid (HDEHP) as extractant has been performed. Among a variety of metals in simulated HLLW, Mo, Zr, Y, and Fe are extractable, Mo and Zr were separated from HLLW by equilibrium, and Fe/Y separation was achieved by the effect of non-equilibrium state in TC contactor. Addition of tributyl phosphate could improve extraction of Mo. This study has expanded the scope of the TC contactor to multi-species separation processes. 相似文献
66.
Shoichi Nasu Takaaki Tanifuji Katsuya Uchida Kenji Noda Toshimasa Kurasawa Tadashi Takahashi Masahiko Isshiki Takejiro Miyauchi Kohji Tanuma Fumio Sasajima 《Journal of Nuclear Materials》1980,91(1):121-126
The center temperature of Li2O pellets under neutron irradiation was measured using an encapsuled pin. The surface temperatures of the pellets and the pellet/cladding heat transfer coefficients were estimated on the basis of the well-known conductivity integral. 相似文献
67.
Muhammad Rizaal Kunihisa Nakajima Takumi Saito Masahiko Osaka Koji Okamoto 《Journal of Nuclear Science and Technology》2020,57(9):1062-1073
ABSTRACT The interaction of cesium hydroxide and a calcium silicate insulation material was experimentally investigated at high-temperature conditions to evaluate the possibility of unprecedented cesium retention under severe accident of boiling water reactor. The temperature where the interactions occurred and chemical species of cesium after the interaction were examined in this study. A thermogravimetry equipped with differential thermal analysis was used to analyze thermal events in the samples of mixed calcium silicate and cesium hydroxide under oxidizing and reducing atmospheric conditions with a maximum temperature of 1100°C. Before being mixed with cesium hydroxide, a part of calcium silicate was pretreated at high temperature to evaluate the effect of possible structural changes of this material due to a preceding thermal history and also for the sake of thermodynamic evaluation. It was found that for the original material, as xonotlite (Ca6Si6O17(OH)2) crystal, the endothermic reaction with cesium hydroxide occurred over the temperature range 575–730°C; meanwhile, for heat-treated material, which varied the crystal phase of original material to wollastonite (CaSiO3), the interaction occurred over the temperature range 700–1100°C. The X-ray diffraction analyses have indicated that both types of calcium silicates regardless of the atmospheric conditions, cesium aluminum silicate, CsAlSiO4, was formed with aluminum in the samples as an impurity or adduct. The insolubility of this formed cesium suggested the potency of cesium localization in the primary containment vessels on other structural materials that possess similar elements to that of calcium silicate insulation; hence, an effective decommissioning process could be developed. 相似文献
68.
Nagatoshi Nishiwaki Tomoya Konishi Shiro Tsukamoto Masahiko Shimoda 《Journal of Inorganic and Organometallic Polymers and Materials》2010,20(4):873-876
A palladium catalyst supported on a semiconductor plate underwent the Heck reaction effectively to afford a coupling product. The catalytic plate was easily recovered from the reaction mixture with tweezers and reused several times without any special treatment. Comparison of reusability, durability, and treatability of seven kinds of commercially available solid-supported palladium catalysts and the semiconductor-supported catalyst plate was studied. 相似文献
69.
70.
Ramon delos Santos Valynn Mag-usara Anthony Tuico Vernalyn Copa Arnel Salvador Kohji Yamamoto Armando Somintac Kazuyoshi Kurihara Hideaki Kitahara Masahiko Tani Elmer Estacio 《Journal of Infrared, Millimeter and Terahertz Waves》2018,39(6):514-520
The influence of crystal thickness of metal-coated <100>-cut GaAs (M-G-M) on Cherenkov-phase-matched terahertz (THz) pulse detection was studied. The M-G-M detectors were utilized in conjunction with a metallic tapered parallel-plate waveguide (TPPWG). Polarization-sensitive measurements were carried out to exemplify the efficacy of GaAs in detecting transverse magnetic (TM)- and transverse electric (TE)-polarized THz waves. The reduction of GaAs’ thickness increased the THz amplitude spectra of the detected TM-polarized THz electro-optic (EO) signal due to enhanced electric field associated with a more tightly-focused and well-concentrated THz radiation on the thinner M-G-M. The higher-fluence THz beam coupled to the thinner M-G-M improved the integrated intensity of the detected THz amplitude spectrum. This trend was not observed for TE-polarized THz waves, wherein the integrated intensities were almost comparable. Nevertheless, good agreement of spectral line shapes of the superposed TM- and TE-polarized THz-EO signals with that of elliptically polarized THz-EO signal demonstrates excellent polarization-resolved detection capabilities of M-G-M via Cherenkov-phase-matched EO sampling technique. 相似文献