全文获取类型
收费全文 | 61篇 |
免费 | 0篇 |
国内免费 | 4篇 |
专业分类
系统科学 | 2篇 |
教育与普及 | 1篇 |
现状及发展 | 17篇 |
研究方法 | 4篇 |
综合类 | 36篇 |
自然研究 | 5篇 |
出版年
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 5篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1962年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有65条查询结果,搜索用时 31 毫秒
51.
52.
Gaoqing Max Lu 《中国科学基金(英文版)》2011,(1):19-19
I have met Professor Shi Changxu only a few times at meetings in China.One encounter that I can never forget is a meeting held in Beijing late December 2002.I was invited to participate in the inaugural meeting of the Centre for Interfacial Materials of the Institute of Metal Research,Chinese Academy of Sciences, under the CAS program of "Outstanding Overseas Chinese Scientists".Professor Shi was the Chair of the Experts Panel at the meeting.Of course the meeting went very well,and the centre was supported 相似文献
53.
54.
Ordered mesoporous tungsten oxide and titanium oxide
composites and their photocatalytic degradation behavior 总被引:1,自引:0,他引:1
Highly ordered mesoporous WO3/TiO2 (MWTs) composite materials with tunable
chemical compositions were obtained by a surfactant template-assisted evaporation-induced selfassembly
(EISA) processes. The structure properties of the MWT materials were characterized by
small angle XRD, TEM and N2 sorption. The resultant materials showed large amount of ordered
mesopores and high chemical homogeneity. With increasing crystallinity degree, the order degrees
of mesostructure turned worse gradually. The MWT hybrids exhibited excellent visible light
response due to the addition of WO3 with narrow band gap. Photocatalytic performances of the
MWT samples were determined by measuring the photo-degradation of rhodamine B dye and
phenol under simulated solar light irradiation. The effect of material parameters such as surface
area, crystallinity and chemical compositions in the binary heterostructured system on photocatalytic
performance were discussed in details. 相似文献
55.
A kappa-immunoglobulin gene is formed by site-specific recombination without further somatic mutation. 总被引:76,自引:0,他引:76
The active gene for a kappa light chain is formed by a somatic recombination event that joins one of several hundred variable region genes to one of a series of recombination sites (J-segments) encoded close to the kappa constant region gene. The nucleotide sequences of cloned germ line and somatically recombined genes define the precise organisation of these genetic segments and the site and nature of the recombination event that joined them. Apart from somatic recombination, no further alteration of ther germ line sequence has occurred. The J-segment is of special interest as it encodes signals for both DNA and RNA splicing and provides a means of generating further immunoglobulin gene diversity. 相似文献
56.
57.
Ohne Zusammenfassung 相似文献
58.
Most inner main-belt asteroids are primitive rock and metal bodies in orbit about the Sun between Mars and Jupiter. Disruption, through high-velocity collisions or rotational spin-up, is believed to be the primary mechanism for the production and destruction of small asteroids and a contributor to dust in the Sun's zodiacal cloud, while analogous collisions around other stars feed dust to their debris disks. Unfortunately, direct evidence about the mechanism or rate of disruption is lacking, owing to the rarity of the events. Here we report observations of P/2010?A2, a previously unknown inner-belt asteroid with a peculiar, comet-like morphology. The data reveal a nucleus of diameter approximately 120?metres with an associated tail of millimetre-sized dust particles. We conclude that it is most probably the remnant of a recent asteroidal disruption in February/March 2009, evolving slowly under the action of solar radiation pressure, in agreement with independent work. 相似文献
59.
Predicting the consequences of species loss is critically important, given present threats to biological diversity such as habitat destruction, overharvesting and climate change. Several empirical studies have reported decreased ecosystem performance (for example, primary productivity) coincident with decreased biodiversity, although the relative influence of biotic effects and confounding abiotic factors has been vigorously debated. Whereas several investigations focused on single trophic levels (for example, grassland plants), studies of whole systems have revealed multiple layers of feedbacks, hidden drivers and emergent properties, making the consequences of species loss more difficult to predict. Here we report functionally important organisms and considerable biocomplexity in a sedimentary seafloor habitat, one of Earth's most widespread ecosystems. Experimental field measurements demonstrate how the abundance of spatangoid urchins--infaunal (in seafloor sediment) grazers/deposit feeders--is positively related to primary production, as their activities change nutrient fluxes and improve conditions for production by microphytobenthos (sedimentatry microbes and unicellular algae). Declines of spatangoid urchins after trawling are well documented, and our research linking these bioturbators to important benthic-pelagic fluxes highlights potential ramifications for productivity in coastal oceans. 相似文献
60.
S Ruggieri L Lauro S Vincenzetti I Santarelli E Balducci A Vita G Magni P Natalini 《Experientia》1991,47(6):610-612
NAD pyrophosphorylase (ATP:NMN adenylyltransferase) activity has been measured in the skeletal muscle of dystrophic mice. The amount of this enzyme in the dystrophic mice, as determined by three different methods, was about one half of that in the controls. In addition, the concentration of ATP was too low to be detected in crude extracts of dystrophic mouse skeletal muscle, which were prepared using Tris buffer alone or Tris buffer containing either 3 M KCl, or 1 mM PMSF. 相似文献