全文获取类型
收费全文 | 4023篇 |
免费 | 170篇 |
国内免费 | 18篇 |
专业分类
化学 | 2803篇 |
晶体学 | 40篇 |
力学 | 95篇 |
数学 | 336篇 |
物理学 | 937篇 |
出版年
2023年 | 16篇 |
2022年 | 49篇 |
2021年 | 94篇 |
2020年 | 81篇 |
2019年 | 69篇 |
2018年 | 59篇 |
2017年 | 48篇 |
2016年 | 122篇 |
2015年 | 115篇 |
2014年 | 141篇 |
2013年 | 232篇 |
2012年 | 320篇 |
2011年 | 354篇 |
2010年 | 181篇 |
2009年 | 172篇 |
2008年 | 266篇 |
2007年 | 247篇 |
2006年 | 227篇 |
2005年 | 217篇 |
2004年 | 169篇 |
2003年 | 152篇 |
2002年 | 137篇 |
2001年 | 88篇 |
2000年 | 90篇 |
1999年 | 74篇 |
1998年 | 59篇 |
1997年 | 33篇 |
1996年 | 49篇 |
1995年 | 45篇 |
1994年 | 48篇 |
1993年 | 44篇 |
1992年 | 30篇 |
1991年 | 21篇 |
1990年 | 29篇 |
1989年 | 21篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有4211条查询结果,搜索用时 359 毫秒
931.
932.
When the Wolsong 1st CANDU reactor in Korea is reaching the end of its original lifespan, decommissioning has been one of the largest issues faced by the nuclear industry and the government for the estimation of expense. The radioactive sources in the construction stuffs and components of the reactor such as pressure tubes, steam generators must be evaluated for the estimation of the appropriate expense for the decommissioning. Unfortunately we do not have exact information about the initial composition of the pressure tubes. In this study the elemental contents of Nb and Zr in the activated zircaloy pressure tubes was investigated. Nb is one of the important elements that characterize the physical and mechanical properties of the pressure tube and a major source of high radioactivity. The prepared samples were strongly irradiated again in the vertical irradiation channel at the HANARO research reactor in the Korea Atomic Energy Research Institute (KAERI) and then measured by an HPGe detector. 相似文献
933.
Hye-Young Lee You-Jin Choi Eun-Jung Jung Hu-Quan Yin Jung-Taek Kwon Ji-Eun Kim Hwang-Tae Im Myung-Haing Cho Ju-Han Kim Hyun-Young Kim Byung-Hoon Lee 《Journal of nanoparticle research》2010,12(5):1567-1578
Silver nanoparticles (AgNP) are among the fastest growing product categories in the nanotechnology industry. Despite the importance of AgNP in consumer products and clinical applications, relatively little is known regarding AgNP toxicity and its associated risks. We investigated the effects of AgNP on gene expression in the mouse brain using Affymetrix Mouse Genome Arrays. C57BL/6 mice were exposed to AgNP (geometric mean diameter, 22.18 ± 1.72 nm; 1.91 × 107 particles/cm3) for 6 h/day, 5 days/week using the nose-only exposure system for 2 weeks. Total RNA isolated from the cerebrum and cerebellum was subjected to hybridization. From over 39,000 probe sets, 468 genes in the cerebrum and 952 genes in the cerebellum were identified as AgNP-responsive (one-way analysis of variance; p < 0.05). The largest groups of gene products affected by AgNP exposure included 73 genes in the cerebrum and 144 genes in the cerebellum. AgNP exposure modulated the expression of several genes associated with motor neuron disorders, neurodegenerative disease, and immune cell function, indicating potential neurotoxicity and immunotoxicity associated with AgNP exposure. Real-time PCR data for five genes analyzed from whole blood showed good correlation with the observed changes in the brain. Following rigorous validation and substantiation, these genes may assist in the development of surrogate markers for AgNP exposure and/or toxicity. 相似文献
934.
Synthesis of Silicate Zeolite Analogues Using Organic Sulfonium Compounds as Structure‐Directing Agents
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Changbum Jo Sungjune Lee Prof. Sung June Cho Prof. Ryong Ryoo 《Angewandte Chemie (International ed. in English)》2015,54(43):12805-12808
A microporous crystalline silica zeolite of the MEL structure type and three other zeolite analogues composed of germanosilicate frameworks were synthesized using tributylsulfonium, triphenylsulfonium, or tri(para‐tolyl)sulfonium as the structure‐directing agent. The germanosilicates thus obtained had ISV, ITT, or a new zeolite structure depending on the synthesis conditions. The structure of the new germanosilicate was solved using X‐ray powder diffraction data with the aid of a charge‐flipping method. The solution indicated a crystal structure belonging to the P63/mmc space group with cell parameters of a=16.2003 Å and c=21.8579 Å. After calcination, the new germanosilicate material exhibited two types of accessible micropores with diameters of 0.61 and 0.78 nm. 相似文献
935.
936.
937.
938.
Kyo-Hyun Cho Byung-Sik Jang Kyung-Hoon Kim Dae-Won Park 《Reaction Kinetics and Catalysis Letters》2006,88(1):43-50
Summary The performance of pyrophyllite and halloysite clays in the degradation of polystyrene (PS) was investigated. The degradation
was carried out in a semi-batch reactor with a mixture of polystyrene and catalysts at 400-450oC. The catalysts showed good catalytic activity for the degradation of PS with high selectivity to aromatics liquids. Styrene
is the major product, and ethylbenzene is the second most abundant one in the liquid product. The catalytic degradation showed
much less production of styrene dimers and higher selectivity to ethylbenzene than the thermal degradation did. High degradation
temperature favored the production of styrene monomer, but it decreased the ethylbenzene production. 相似文献
939.
Cellulose - Cellulose-based materials, such as cellulose microspheres, have attracted enormous attention because of their widespread applications in water and protein purifications, chromatographic... 相似文献
940.
Yeon Seo Cho Seulbi Kim Prof. Young-Kwan Kim Prof. Sung Giu Jin Ji Hun Park 《化学:亚洲杂志》2021,16(22):3636-3639
Resveratrol (3,4’,5-trihydroxystilbene) is beneficial to human health due to its diverse biological activities including its anti-inflammatory and anti-oxidative effects as confirmed by pharmacokinetic tests. Despite these clinical merits, resveratrol's limited hydrosolubility and chemical vulnerability remain challenging with regard to developing a controlled delivery system with enhanced bioavailability. In this work, we report a resveratrol-β-lactoglobulin (R-BLG) composite nanocoating through a layer-by-layer assembly with Fe(III)-tannic acid nanofilms. The R-BLG composite nanocoating can be formed in planar and particulate substrates, showing excellent film stability under a broad range of pH values and against enzymatic digestion during a weeklong incubation. We envision that the proteinaceous nanocoating herein could be combined with existing pharmaceutical carrier materials (e. g., microcapsules and nanoparticles) to realize advanced drug delivery systems with an expanded repertoire of hydrophobic drugs. 相似文献