全文获取类型
收费全文 | 5351篇 |
免费 | 106篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 266篇 |
综合类 | 7篇 |
化学工业 | 1020篇 |
金属工艺 | 154篇 |
机械仪表 | 104篇 |
建筑科学 | 74篇 |
矿业工程 | 2篇 |
能源动力 | 108篇 |
轻工业 | 339篇 |
水利工程 | 9篇 |
石油天然气 | 17篇 |
无线电 | 560篇 |
一般工业技术 | 1040篇 |
冶金工业 | 1297篇 |
原子能技术 | 161篇 |
自动化技术 | 318篇 |
出版年
2023年 | 17篇 |
2022年 | 41篇 |
2021年 | 102篇 |
2020年 | 39篇 |
2019年 | 60篇 |
2018年 | 60篇 |
2017年 | 62篇 |
2016年 | 79篇 |
2015年 | 58篇 |
2014年 | 87篇 |
2013年 | 198篇 |
2012年 | 177篇 |
2011年 | 247篇 |
2010年 | 162篇 |
2009年 | 167篇 |
2008年 | 181篇 |
2007年 | 193篇 |
2006年 | 165篇 |
2005年 | 166篇 |
2004年 | 141篇 |
2003年 | 145篇 |
2002年 | 115篇 |
2001年 | 107篇 |
2000年 | 107篇 |
1999年 | 135篇 |
1998年 | 536篇 |
1997年 | 291篇 |
1996年 | 219篇 |
1995年 | 165篇 |
1994年 | 130篇 |
1993年 | 121篇 |
1992年 | 78篇 |
1991年 | 81篇 |
1990年 | 64篇 |
1989年 | 72篇 |
1988年 | 51篇 |
1987年 | 57篇 |
1986年 | 61篇 |
1985年 | 59篇 |
1984年 | 55篇 |
1983年 | 41篇 |
1982年 | 42篇 |
1981年 | 47篇 |
1980年 | 44篇 |
1979年 | 33篇 |
1978年 | 29篇 |
1977年 | 28篇 |
1976年 | 74篇 |
1975年 | 18篇 |
1974年 | 14篇 |
排序方式: 共有5476条查询结果,搜索用时 156 毫秒
121.
M. Takeuchi S. Ueno E. Flöter K. Sato 《Journal of the American Oil Chemists' Society》2002,79(7):627-632
The binary phase behavior of SOS (1,3-distearoyl-2-oleoyl-sn-glycerol) and SLS (1,3-distearoyl-2-linoleoyl-sn-glycerol) was examined by using DSC and conventional and synchrotron radiation X-ray diffraction. The solid-solution phases
were observed in the metastable α and γ forms in all concentration ranges. Results indicated that the miscible γ form did
not transform to the β′ form when the mixtures were subjected to simple cooling from a high-temperature liquid to a low-temperature
solid phase. However, and α-melt-mediated transformation into β′ and β2 resulted in the formation of immiscible phases in concentration ranges of SLS below 30%. By contrast, at SLS concentration
ranges above 30%, the α-melt-mediated transformation caused crystallization of only the γ form, and β′ and β2 crystals did not appear. These results show that the specific interactions between SOS and SLS are operative in the phase
behavior of the mixture states of SOS and SLS. 相似文献
122.
Masayuki Shirai Chandrashekhar V. Rode Eiichi Mine Akiyoshi Sasaki Osamu Sato Norihito Hiyoshi 《Catalysis Today》2006,115(1-4):248-253
Catalytic ring hydrogenations of naphthalene and 1-naphthol were studied over several supported metal catalysts in supercritical carbon dioxide solvent at low temperature. Higher concentration of hydrogen in supercritical carbon dioxide and lower reaction temperature were responsible for higher catalyst activity and selectivities to the desired partial ring hydrogenated products as compared with those observed in organic solvent for the same catalyst. 相似文献
123.
Koji Watari Hiromi Nakano Kimiyasu Sato Kazuyoshi Urabe Kozo Ishizaki Shixun Cao Katsunori Mori 《Journal of the American Ceramic Society》2003,86(10):1812-1814
The thermal conductivity of a SiC ceramic was measured as 270 W·m−1 ·K−1 at room temperature. At low temperatures ( T < 25 K), the decrease in the conductivity was proportional to T 3 on a logarithmic scale, which indicated that the conductivity was controlled by boundaries. The calculated phonon mean free path in the ceramic increased with decreased temperature, but was limited to ∼4 μm, a length almost equal to the grain size, at temperatures below 30 K. We concluded that the thermal conductivity of the ceramic below 30 K was influenced significantly by grain boundaries and grain junctions. 相似文献
124.
A -conjugated polymer, poly(pyridine-2,5-diyl) (PPy) was investigated as a support for CuCl2 in the synthesis of dimethyl carbonate by oxidative carbonylation of methanol. The PPy–CuCl2 adduct had high catalytic activity which was comparable to that of the homogeneous CuCl2 catalyst. The adduct caused corrosion of stainless-steel vessels only to minor extent, compared with the homogeneous CuCl2 catalyst. This PPy–CuCl2 catalyst was easily recycled by filtration and showed a similar catalytic activity in the third time use. The presence of the -conjugated system in PPy, through which electrons can move, may bring about the high catalytic activity for the oxidative carbonylation of methanol, which involves Cu(II)/Cu(I) redox processes. 相似文献
125.
Tsugio Sato Kenji Dosaka Toshiaki Yoshioka Akitsugu Okuwaki Kazuo Torii Yoshiro Onodera 《Journal of the American Ceramic Society》1992,75(3):552-556
Amorphous CeO2 –ZrO2 gels were prepared by coprecipitation in ammonia solutions. The onset of crystallization of the gels, from calcining in air, was 420°C, while 200° to 250°C in the presence of water and organic solvents such as methanol and ethanol. The sintering behaviors of CeO2 –ZrO2 powders were sensitive to the crystallizing conditions, since hard agglomerates formed when the precipitated gels were crystallized by normal calcination in air, whereas soft agglomerates formed when they were crystallized in water or organic solvents. CeO2 –ZrO2 powders crystallized in methanol and water at 250°C were sintered to full theoretical density at 1150° and 1400°C, respectively, whereas that crystallized by calcination in air at 450°C was sintered to only 95.2% of theoretical density, even at 1500°C. 相似文献
126.
The present study was carried out to examine if the positional distribution of medium-chain fatty acid (MCF) in dietary synthetic
fat influences lymphatic transport of dietary fat and the chemical composition of chylomicrons in rats with permanent cannulation
of thoracic duct. Four types of synthetic triacylglycerol were prepared: (i) sn-1(3) MCF-sn 2 linoleic acid, (ii) interesterified sn-1(3) MCF-sn 2 linoleic acid, (iii) sn-2 MCF-sn-1(3) linoleic acid, and (iv) interesterified sn-2 MCF-sn-1(3) linoleic acid. A purified diet composed of equal amounts of the synthetic fat and cocoa butter was given to rats with
permanent lymph duct cannulation. The positional distribution of MCF in the dietary fat had no significant effect on the lymph
flow, triacylglycerol output, phospholipid output, lipid composition of chylomicrons, or the particle size. The positional
distribution of MCF in the synthetic triacylglycerol was maintained in the chylomicron triacylglycerol. These results showed
that MCF in the dietary triacylglycerol is transported into lymphatics and the positional distribution is well preserved in
chylomicron triacylglycerol. 相似文献
127.
Hitoshi Masuda Chiyoshi Kamizawa Kunio Hata Kingo Yokota Tomoo Sakai Mitsuhiro Sato 《Desalination》1978,25(1):89-97
The evaporation drain of sulfite pulp spent liquor contains few volatile fatty acids, most of which is acetic acid. The main objective of this study is to recover acetic acid as the concentrated solution (about 4%), which could be used as a culture medium of the yeast. As acetic acid can easily pass through the cellulose acetate membrane, SP drains neutralized by NaOH, NH4OH and Ca(OH)2 were used as the feed solutions. In all cases, concentration by reverse osmosis was successfully carried out provided the appropriate pretreatment was employed. The recovery of acetic acid was 95.6, 90.5 and 98.2% for Na-, NH4-, and Ca-drain, respectively. In addition, the recovered (permeated) water may be used as an industrial one. 相似文献
128.
Seiichi Suenaga Masako Nakahashi Miho Maruyama Takayuki Fukasawa 《Journal of the American Ceramic Society》1997,80(2):439-444
Wetting and brazing studies of sputtering-deposited, submicrometer thin film filler metal in an Ag—Cu—Ti/Al2 O3 system were performed. The interfacial reaction layer between the filler metal and Al2 O3 was investigated. It is possible to make a brazing joint even with a reaction layer of less than 100 nm thickness. Different types of interfacial reaction layers were observed when the Ti content in the filler metal was varied. The Cu—Ti—O system compounds were observed in the samples with high wetting capabilities, but not in the sample with low wetting characteristics. It was found that these compounds are substances that promote effective brazing. 相似文献
129.
Kunihito Koumoto Shunji Takeda Chul Hoon Pai Takayori Sato Hiroaki Yanagida 《Journal of the American Ceramic Society》1989,72(10):1985-1987
Structural images of the stacking faults in β-SiC were obtained with a high-resolution electron microscope. Stacking faults initially present in β-SiC powder particles were eliminated as grain growth proceeded at elevated temperatures. 相似文献
130.
Single crystals of β1 and polycrystals of β2 of POP and SOS were obtained from acetonitrile solution. The crystallization behavior of the two polymorphs was almost the
same in POP and SOS; rapid cooling of the solution preferentially crystallized the metastable β2 form, and the most stable β1 form crystallized in a very low solute concentration at the expense of β2, via solution-mediated transformation. The single crystal of β2 revealed needle-like irregular shape, whereas well-defined slender rhombic shape was observed in β1. The solubilities of the β1 forms of POP and SOS in tetradecane solution were precisely measured in a temperature range of 10∼20°C. This study showed
that the solvent crystallization was the single way to grow the β1 crystal, since melt-cooling and melt-mediated transformation did not crystallize β1 both in POP and SOS.
Presented at 1988 AOCS Annual Meeting at Phoenix. 相似文献