全文获取类型
收费全文 | 374篇 |
免费 | 4篇 |
专业分类
化学 | 300篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 2篇 |
物理学 | 65篇 |
出版年
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 16篇 |
2011年 | 12篇 |
2010年 | 9篇 |
2009年 | 7篇 |
2008年 | 15篇 |
2007年 | 21篇 |
2006年 | 20篇 |
2005年 | 21篇 |
2004年 | 16篇 |
2003年 | 11篇 |
2002年 | 15篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 20篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 14篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1968年 | 1篇 |
1965年 | 1篇 |
1962年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有378条查询结果,搜索用时 15 毫秒
91.
Cassiola F Rogers RA Kiyohara PK Joekes I 《Colloids and surfaces. B, Biointerfaces》2005,41(4):277-283
Saccharomyces cerevisiae was supported on chrysotile, crocidolite and lixiviated chrysotile. Samples of the supported cells and free cells were observed by confocal laser scanning microscopy. After 30 days, the free cells showed no viability when stored at 30 °C, and a viability of 40% when stored at 4 °C. Supported cells stored at 30 °C were more viable than the free cells at early times, but showed no viability after 30 days. Samples stored at 4 °C showed that the adhered cells are more viable than the free cells, up to 30 days. Cells supported on chrysotile and lixiviated chrysotile had 80% viability, and on crocidolite 70% viability. Scanning electron microscopy showed that cells supported on lixiviated chrysotile are fully covered by the support, but crocidolite fibers adhere less, since they are stiffer. Fermentation experiments performed after 3 years storage showed that four from the five lixiviated chrysotile samples and one of the three crocidolite samples were active. In all cases, a delay time for the onset of fermentation was observed indicating a state of latency. 相似文献
92.
Keikichi Miyahara 《Microchemical Journal》1974,19(4):416-422
A method is described for the decimilligram determination of nitrogen in organic compounds based on measuring by interpolation the volume of nitrogen collected in a capillary tube. The blank value is determined indentically. 相似文献
93.
Two bacteria exhibiting resistance to toxic arsenic were isolated. These had been contaminated with arsenic in a Chlorella sp. culture medium containing arsenic. The two bacteria were identified as Klebsiella oxytoca and Xanthomonas sp., and grew well in a peptone medium at neutral pH at 30°C, reaching the stationary phase in ca 100h and 70h, respectively. The growth of the bacteria was not affected by arsenic(V) concentrations in the medium as high as 1000mg dm?3. The bacteria bioaccumulated arsenic, a part of the arsenic being methylated. The bioaccumulation exhibited its peak around the turing point from the log phase to the stationary phase. The relative content of methylated arsenic in the excrement was greater than that in the bacterial cells. Adaptation treatment of inorganic arsenic caused an increase in the bioaccumulation of inorganic arsenic by K. oxytoca. Such a situation was not observed in the case of Xanthomonas sp. The bacteria also bioaccumulated methylated arsenic compounds, and demethylation of these species was observed. When the bacteria were killed by ethanol, arsenic was not taken up by the cells. 相似文献
94.
Koji Yamamoto Yu Oya Keiichiro Kagawa Masahiro Nunoshita Jun Ohta Kunihiro Watanabe 《Optical Review》2006,13(2):64-68
A complementary metal oxide semiconductor (CMOS) image sensor for the detection of modulated light under background illumination
has been developed. When an object is illuminated by a modulated light source under background illumination the sensor enables
the object alone to be captured. This paper describes improvements in pixel architecture for reducing fixed pattern noise
(FPN) and improving the sensitivity of the image sensor. The improved 128 × 128 pixel CMOS image sensor with a column parallel
analog-to-digital converter (ADC) circuit was fabricated using 0.35-mm CMOS technology. The resulting captured images are
shown and the properties of improved pixel architecture are described. The image sensor has FPN of 1/28 that of the previous
image sensor and an improved pixel architecture comprising a common in-pixel amp and a correlated double sampling (CDS) circuit.
The use of a split photogate increases the sensitivity of the image sensor to 1.3 times that of the previous image sensor. 相似文献
95.
Masayuki Itagaki Akihiro Taya Kunihiro Watanabe Kazuhiko Noda 《Analytical sciences》2002,18(6):641-644
The electrochemical impedance of an iron electrode often shows the capacitive and inductive loops on the complex plane. The capacitive loop originates from the time constant of the charge transfer resistance and the electric double layer capacitance. The inductive loop is explained by Faradaic processes involving the reaction intermediate. In some cases, these loops deviate from a true semicircle. In this paper, the origins and curve-fitting methods for the deviated loops of electrochemical impedance are discussed. The constant phase element (CPE) was used to present the deviation of the capacitive loop instead of electric double layer capacitance. The reaction rate constants, which are a function of the frequency, are proposed for the Faradaic impedance to present the deviated inductive loop. 相似文献
96.
We synthesized some 4,4'- and 2,2'-dihydroxytriphenylmethane derivatives 3a--e and 4a--c by condensation of phenol 1 and aromatic aldehyde 2 in moderate to good yields (30--83%). Most of them showed significant antiviral activity against herpes simplex virus type 1 (anti-HSV-1 activity) in a plaque reduction assay. The most potent antiviral activity (EC(50)=0.79 microg/ml) was observed in the 4,4'-dihydroxytriphenylmethane derivative 3b. This compound 3b showed lower cytotoxicity (CC(50)=30.2 microg/ml), compared to that of the prototype 3a. 相似文献
97.
Kubo M Matsuoka K Takahashi A Shibasaki-Kitakawa N Yonemoto T 《Ultrasonics sonochemistry》2005,12(4):263-269
The degradation of phenol by ultrasonic irradiation in the presence of TiO2 was investigated in complete darkness. The effects of amount of TiO2 and the combination of TiO2 addition with gas (air or oxygen) supply on the degradation kinetics of phenol and the formation of the reaction products were examined. The degradation rate of phenol increased with the amount of TiO2. As the dissolved oxygen concentration increased by supplying oxygen, the degradation rate of phenol also increased. A kinetic model for the disappearance of phenol was proposed. The model takes into account the OH radical formation by direct water degradation, indirect degradation by oxygen atom and indirect degradation by TiO2 catalysis. The calculated results explained well the fact that a higher amount of TiO2 and dissolved oxygen concentration gave faster disappearance rate. 相似文献
98.
Kunihiro Hamada Toshiro Iijima Ralph McGregor 《Journal of Polymer Science.Polymer Physics》1987,25(6):1299-1310
The rotational mobility of anionic spin probes in water-containing nylon 6 film was investigated by means of electron spin resonance (ESR) measurements for comparison with the results for nonionic spin probes reported previously. The extrema separation of the ESR spectra, 2Az′ increased with time owing to the evaporation of water. In the higher temperature region, 2Az′ increased steeply with time at first, and then more slowly, whereas for the nonionic spin probes, 2Az′ increased gradually and monotonically with time. This fact suggests that the anionic probe molecules are more strongly affected by water than the nonionic ones, i.e., the former probes are located in hydrophilic regions and the latter in hydrophobic regions. T50G, which can be empirically correlated with the glass transition temperature of the polymer Tg decreased with increasing water content. The decreasing tendency for the anionic spin probes was stronger than that for the nonionic ones. This fact also indicates that the local environment around the probe molecules varies from probe to probe. The rotational correlation time τR decreased markedly with an increase in water content. The Arrhenius plots of τR showed two crossover points. The crossover points in the higher temperature region Tn decreased greatly with increasing water content. The difference in Tn between dried and water-containing films was larger than that for T50G. The activation energy for rotation, E, also decreased with increasing water content. It is suggested that water concentrates around the anionic spin probes and makes their rotation much easier. 相似文献
99.
100.
A new method for handling hygroscopic and volatile samples for decimilligram determination of organic nitrogen by the sealed-tube method was described. It involves the use of a copper-foil capsule in which hygroscopic and volatile samples can be dried to constant weight and weighed. Satisfactory results were obtained with this method. 相似文献