全文获取类型
收费全文 | 7673篇 |
免费 | 173篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 397篇 |
综合类 | 13篇 |
化学工业 | 1566篇 |
金属工艺 | 213篇 |
机械仪表 | 200篇 |
建筑科学 | 171篇 |
矿业工程 | 9篇 |
能源动力 | 214篇 |
轻工业 | 582篇 |
水利工程 | 38篇 |
石油天然气 | 21篇 |
无线电 | 665篇 |
一般工业技术 | 1336篇 |
冶金工业 | 1806篇 |
原子能技术 | 190篇 |
自动化技术 | 453篇 |
出版年
2023年 | 51篇 |
2022年 | 98篇 |
2021年 | 157篇 |
2020年 | 74篇 |
2019年 | 66篇 |
2018年 | 95篇 |
2017年 | 92篇 |
2016年 | 106篇 |
2015年 | 95篇 |
2014年 | 112篇 |
2013年 | 300篇 |
2012年 | 248篇 |
2011年 | 337篇 |
2010年 | 227篇 |
2009年 | 251篇 |
2008年 | 254篇 |
2007年 | 276篇 |
2006年 | 258篇 |
2005年 | 229篇 |
2004年 | 203篇 |
2003年 | 212篇 |
2002年 | 221篇 |
2001年 | 189篇 |
2000年 | 164篇 |
1999年 | 185篇 |
1998年 | 685篇 |
1997年 | 429篇 |
1996年 | 321篇 |
1995年 | 226篇 |
1994年 | 225篇 |
1993年 | 186篇 |
1992年 | 105篇 |
1991年 | 100篇 |
1990年 | 95篇 |
1989年 | 82篇 |
1988年 | 80篇 |
1987年 | 66篇 |
1986年 | 77篇 |
1985年 | 91篇 |
1984年 | 67篇 |
1983年 | 67篇 |
1982年 | 48篇 |
1981年 | 61篇 |
1980年 | 57篇 |
1979年 | 39篇 |
1978年 | 31篇 |
1977年 | 58篇 |
1976年 | 60篇 |
1975年 | 34篇 |
1973年 | 25篇 |
排序方式: 共有7874条查询结果,搜索用时 15 毫秒
101.
Jiunn Yih Lee Hisashi Tanaka Hideo Takezoe Atsuo Fukuda Eiichi Kuze Hiroshi Iwanaga 《应用聚合物科学杂志》1984,29(3):795-802
A novel method is proposed of preparing thin Ag–Hg alloy on PAAm film surface at room temperature: The film of interest is formed by holding PAAm aqueous solution with AgNO3 in Hg-saturated atmosphere. Two kinds of films, one of which is a conductor and the other an insulator, can be selectively formed with pH-controlled PAAm solution by ammonia. The conducting surface is assigned to the α phase of Ag–Hg alloy by means of X-ray analysis. Potentiometric titration and IR spectral studies suggest the existence of PAAm–Ag+ complexes. On the basis of their structure and the oxidation and reduction potential of Ag+ and Hg2+, the mechanism of film formation is also discussed. 相似文献
102.
An addition reaction of maleic anhydride with polypropylene takes place in the presence of radical reagents or sunlight. The initial rate of the reaction was proportional to the concentration of polypropylene and maleic anhydride, and one-half power of the concentration of the radical reagents. The increase in the temperature from 80 to 120°C increased the rate of the reaction and di-cumyl peroxide was effective as a radical reagent for this reaction. Ionic crosslinked rubber-like polymers were obtained from the reaction of maleic polypropylene with some alkali metal compounds. They showed the characteristic absorption band due to ? COO? in their infrared spectra. 相似文献
103.
Naoto Kimbara Akio Nishijima Toshio Sato Yuji Yoshimura Hiromichi Shimada Nobuyuki Matsubayashi Akinori Yukimura 《Catalysis Letters》1990,6(3-6):409-415
TiN supported molybdenum sulfide catalysts showed much higher activity for cleavage of C-C bonds than oxide supported molybdenum sulfide catalysts, indicating the possibility of a new generation of supports for hydroprocessing catalysts. 相似文献
104.
M. Shimada M. Koizumi A. Tanaka T. Yamada 《Journal of the American Ceramic Society》1982,65(4):c48-c48
Temperature dependence of KIC values for Si3 N4 bodies sintered at high pressures without additives was studied from room temperature to 1400°C. Little change in KK was found in this range. 相似文献
105.
Praphan?Pinsirodom Yomi?Watanabe Toshihiro?Nagao Akio?Sugihara Takashi?Kobayashi Yuji?ShimadaEmail author 《Journal of the American Oil Chemists' Society》2004,81(6):543-547
Production of MAG by a lipase-catalyzed reaction is known to be effective at low temperature. This phenomenon can be explained
by assuming that synthesized MAG are excluded from the reaction system because MAG, which have low m.p., are solidified at
low temperatures. Consequently, MAG are efficiently accumulated and do not serve as the precursor of DAG. If this hypothesis
is correct, the critical temperature for MAG production, defined as the highest temperature at which DAG synthesis is repressed,
should depend on the m.p. of the MAG. Esterification of FFA with glycerol using Candida rugosa, Rhizopus oryzae, and Penicillium camembertii lipases produced MAG efficiently at low temperatures. However, Candida lipase showed very low esterification activity at high temperatures (>20°C), and Rhizopus lipase produced not only MAG but also DAG even at low temperatures. Meanwhile, P. camembertii lipase catalyzed synthesis of MAG only from FFA and glycerol at low temperatures, although the enzyme catalyzed synthesis
of DAG from MAG in addition to synthesis of MAG at high temperatures. We thus studied the effect of temperature on esterification
of C10−C18 FFA with glycerol using Penicillium lipase as a catalyst and determined the critical temperatures for production of MAG. The critical temperature for production
of each MAG showed a linear correlation with m.p. of the MAG, which supported the hypothesis. In addition, because the m.p.
of MAG are estimated from that of the constituent FA, the optimal temperature for production of MAG can be predicted from
the m.p. of the FFA used as a substrate. 相似文献
106.
Kikuo Maekawa Makoto Yamazaki Toshinobu Ogiso Takehiko Maruyama Hideki Ogura Wakako Kashino Hanae Koiso Masaya Yamaguchi Makiro Tanaka Yasuharu Den 《Language Resources and Evaluation》2014,48(2):345-371
The balanced corpus of contemporary written Japanese (BCCWJ) is Japan’s first 100 million words balanced corpus. It consists of three subcorpora (publication subcorpus, library subcorpus, and special-purpose subcorpus) and covers a wide range of text registers including books in general, magazines, newspapers, governmental white papers, best-selling books, an internet bulletin-board, a blog, school textbooks, minutes of the national diet, publicity newsletters of local governments, laws, and poetry verses. A random sampling technique is utilized whenever possible in order to maximize the representativeness of the corpus. The corpus is annotated in terms of dual POS analysis, document structure, and bibliographical information. The BCCWJ is currently accessible in three different ways including Chunagon a web-based interface to the dual POS analysis data. Lastly, results of some pilot evaluation of the corpus with respect to the textual diversity are reported. The analyses include POS distribution, word-class distribution, entropy of orthography, sentence length, and variation of the adjective predicate. High textual diversity is observed in all these analyses. 相似文献
107.
Tetsuya Tanigami Kanna Kai Koji Tanaka Shuji Matsuzawa 《Journal of Inorganic and Organometallic Polymers》2003,13(4):237-253
Poly[bis(-phenoxyethoxy)phosphazene] [PBPEP] had been shown in our previous paper to be a very useful polymer for investigating the crystallization mechanism of polymers, as the crystallization rate of PBPEP is extraordinarily small when isothermally crystallized from the melt. The crystallization of the low molecular weight oligomers of PBPEP was first studied in comparison to the high molecular weight polymers. The oligomer-rich fraction was obtained by fractionation of the as-polymerized sample, which had a broad molecular weight distribution. The fractions thus obtained were characterized by solution viscometry and size exclusion chromatography. The melting temperature and the growth rate of the spherulite from the melt were investigated by differential scanning calorimetry and optical microscopy. The growth rate was one or two orders of magnitude smaller in the oligomer-rich fraction than in the other high molecular weight fractions. A collapsed spherulite appeared in the oligomer-rich fraction at high crystallization temperatures. It is speculated that in the oligomer-rich fraction there is an excess free energy due to defects in the crystal phase. This defect is considerably larger in the oligomer-rich fraction than in the other fractions because a large quantity of short length chains is present. 相似文献
108.
This paper presents a new maritime lifesaving multiple-effect solar still design where several extended wicks feed seawater to their evaporating areas by capillary force, and the resulting water vapor diffuses and condenses on facing wicks with the condensate flowing through the wicks into storage bags. A theoretical analysis showed that a temperature drop through diffusion layers between evaporating and condensing wicks slowly increases in the main evaporating areas and rapidly near salt depositions whereas the evaporation rate decreases slowly in the main area and rapidly near salt depositions. These changes are caused by increases in salt concentrations and resulting boiling point elevation. With steady-state transfer analysis, the proposed still is predicted to produce about 15 kg m −2d−1 fresh water on a sunny day of 22 MJm−2d−1 solar radiation, showing a potential to be a maritime lifesaving desalinator. 相似文献
109.
The diffusion and adsorption of C.I. Direct Yellow 12 and Blue 15 in water-swollen ordinary cellophane sheets were examined at various ionic strengths. The concentration dependence of apparent diffusion coefficients, Dc, for these dyes was obtained from the diffusion profiles in the substrate, which were measured by the use of the cylindrical film roll method. The decrease of apparent porosity with an increase in the amounts of adsorption was observed. To explain the diffusion/adsorption behaviors of these systems, a variable porosity model was proposed and was applied to analyze the concentration dependence of Dc's. The diffusion/adsorption behaviors of these dyes could be quantitatively described by this model at relatively low ionic strengths. At higher ionic strengths and/or lower values of C, i.e., at the large values of Cim/Cm, where the C's are the concentrations of immobilized (suffix im) and mobile (suffix m) species, it needed to introduce the concept of dynamic equilibria which occurred simultaneously with diffusion but deviated from the true equiliblia measured by the adsorption experiments. 相似文献
110.
The diffusion and adsorption of CO2 inside the pores of Li, Na, and K ion-exchanged X-type zeolites were simulated by molecular dynamics and Monte Carlo calculations. Carbon dioxide diffused inside the zeolites pores while it was colliding with pore walls. Then it stayed in a super cage of zeolites. Inside the pore of Li + ion-exchanged X-type zeolite (Li-X), the electrostatic potential term was −570 kcal/mol, this value was considerably smaller than those of CO2 inside the pores of Na-X and K-X. On the other hand, from Monte Carlo calculations, CO2 was found to strongly absorb near the 3B site for Li + ions. When CO2 passed through the pores of alkali ion-exchanged X-type zeolites, the interaction between the CO2 molecule and the 3B site for Li cation was fairly large. 相似文献