全文获取类型
收费全文 | 137篇 |
免费 | 13篇 |
国内免费 | 16篇 |
专业分类
化学 | 100篇 |
晶体学 | 1篇 |
力学 | 4篇 |
综合类 | 6篇 |
数学 | 27篇 |
物理学 | 28篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 9篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 7篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有166条查询结果,搜索用时 406 毫秒
21.
Accelerating the coagulation process and preventing wound infection are major challenges in the wound care process. Therefore, new multifunctional wound dressings with procoagulant, antibacterial, and antioxidant properties have enormous potential for clinical application. In this work, biodegradable hydrogels containing herbal extracts are prepared for wound dressings. First, the active ingredients are extracted from Amaranthus spinosus (A. spinosus) and Rubia cordifolia (R. cordifolia) and added to the hydrogels prepared from microcrystalline cellulose (MCC), carrageenan, and sodium alginate. Then the composite hydrogels are air-dried to obtain the wound dressings. The wound dressings prepared in this work have good biocompatibility and moisture retention. The mechanical properties of the wound dressings are further improved with the addition of MCC. Besides, the wound dressings have excellent procoagulant, antibacterial, and antioxidant properties due to the presence of R. cordifolia extract. Overall, the most effective group of wound dressings with different ingredient formulations reduces clotting time by 75% and largely inhibits bacterial growth. The wound dressings perform well in the animal wound models to promote wound healing. These results indicate that the hydrogel wound dressings prepared in this work have great potential for medical applications. 相似文献
22.
Zahoor Ahmad Baba Basharat Hamid Tahir Ahmad Sheikh Saad H. Alotaibi Hesham A. El Enshasy Mohammad Javed Ansari Ali Tan Kee Zuan R. Z. Sayyed 《Molecules (Basel, Switzerland)》2021,26(19)
Soil potassium (K) supplement depends intensively on the application of chemical fertilizers, which have substantial harmful environmental effects. However, some bacteria can act as inoculants by converting unavailable and insoluble K forms into plant-accessible forms. Such bacteria are an eco-friendly approach for enhancing plant K absorption and consequently reducing utilization of chemical fertilization. Therefore, the present research was undertaken to isolate, screen, and characterize the K solubilizing bacteria (KSB) from the rhizosphere soils of northern India. Overall, 110 strains were isolated, but only 13 isolates showed significant K solubilizing ability by forming a halo zone on solid media. They were further screened for K solubilizing activity at 0 °C, 1 °C, 3 °C, 5 °C, 7 °C, 15 °C, and 20 °C for 5, 10, and 20 days. All the bacterial isolates showed mineral K solubilization activity at these different temperatures. However, the content of K solubilization increased with the upsurge in temperature and period of incubation. The isolate KSB (Grz) showed the highest K solubilization index of 462.28% after 48 h of incubation at 20 °C. The maximum of 23.38 µg K/mL broth was solubilized by the isolate KSB (Grz) at 20 °C after 20 days of incubation. Based on morphological, biochemical, and molecular characterization (through the 16S rDNA approach), the isolate KSB (Grz) was identified as Mesorhizobium sp. The majority of the strains produced HCN and ammonia. The maximum indole acetic acid (IAA) (31.54 µM/mL) and cellulase (390 µM/mL) were produced by the isolate KSB (Grz). In contrast, the highest protease (525.12 µM/mL) and chitinase (5.20 µM/mL) activities were shown by standard strain Bacillus mucilaginosus and KSB (Gmr) isolate, respectively. 相似文献
23.
24.
在溶剂热体系中,以N,N-二乙基乙二胺为结构导向剂,合成了Al/P为3/4的层状磷酸铝[Al6P8O32][(C2H5)2NHCH2CH2NH3]2·[C2H5NH2CH2CH2NH2C2H5]单晶,并通过X射线单晶衍射结构分析.XRD,ICP,元素分析,差热-热重分析等手段进行了表征.该化合物属单斜晶系,P2(1)/c空间群,晶胞参数:a=0.90945(2)nm,b=1.46424(4)nm,c=1.87572(5)nm,β=102.672(2)°,Z=4.其阴离子层由AlO4四面体和PO3(=O)四面体单元交替连接构成,形成四、六、八元环拓扑结构,无机层以ABAB方式堆积,两种质子化的有机胺分子N,N-二乙基乙二胺及其重排产物N,N′-二乙基乙二胺填充在层间.用分子动力学模拟方法,考察了标题化合物中有机胺与无机层间的相互作用,讨论了这两种有机胺的共模板作用. 相似文献
25.
K. Ogura R. C. Patil H. Shiigi T. Tonosaki M. Nakayama 《Journal of polymer science. Part A, Polymer chemistry》2000,38(24):4343-4352
Various protonated poly(o‐anisidine) (PoAN)/poly(vinyl alcohol) (PVA) composites were prepared with different types of acids: sulfuric (SA), p‐toluene sulfonic (TSA), camphor sulfonic (CSA), and p‐dodecylbenzene sulfonic (DBSA). In the visible spectrum of each composite in dimethyl sulfoxide, three absorption peaks were observed at 440, 620, and 860 nm. The peaks at 440 and 860 nm, which were enhanced with the increasing content of acid‐doped PoAN in the PVA matrix, were attributed to the radical cation and localized polaron generated in the conducting polymer. However, the peak at 620 nm was ascribed to the emeraldine base (EB) form of PoAN; that is, a portion of the acid was detached from the conducting polymer to form EB‐PoAN and free acid. The linear dependence of the logarithmic electrical conductivity on the variation of humidity, which was observed for all the composites, was caused by the salt–base transition of the conducting polymer, that is, by the movement of free acid between the active sites of the conducting polymer and the strongly bound water existing in PVA, which in turn depended directly on the environmental humidity. The response time of the composites to humidity was shortened with a decrease in the size of the dopant anions: DBSA > CSA > TSA > SA. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4343–4352, 2000 相似文献
26.
27.
28.
<正>Oversea Chinese Magnetic Resonance Society(OCMRS)is an independent,non-political and non-profit organization dedicated to bridge magnetic resonance scientists overseas and in China by promoting social,intellectual and academic activities.It was found in the 37th Experimental NMR Conference(ENC)at Asilomar,CA,U.S.,in 1996,and officially registered at Boston,MA,U.S.in 2013.It strives to provide opportunities and benefits for its members by exchanging scientific information,stimulating new research ideas and initializing collaborations. 相似文献
29.
Fuzhong Nian 《中国物理 B》2021,30(12):128901-128901
In a certain period, some news will compete for the top news to gain the most attention and influence, and more news will be submerged in the ocean of news and become mediocre. This article deeply studies the evolution process and competition mechanism of the dissemination of Weibo news. In this paper, we innovatively propose a pre-processing scheme for traditional small-world networks and scale-free networks and divide nodes into three roles:fans, passersby, and anti-fans. The competition mechanism of Weibo top news is defined from the aspects of node role and node aggregation degree. A network evolution model is established based on the competition mechanism. The propagation characteristics of the network evolution model are deeply analyzed, and simulation experiments are performed on the small-world network and the scale-free network. Finally, the validity and rationality of the new model are verified through comparative experiments, and a feasible scheme for the propagation of top news on Weibo is given. 相似文献
30.
In this paper we study a dynamic two-player channel where the manufacturer controls the wholesale price and the investment in quality and the retailer chooses the retail price. We consider that the retail price affects both the demand and the perceived quality of the brand and that its variations contribute to the building of an internal reference price. One of the model’s distinctive features is that it accounts for the two meanings of price, i.e., its classical objective measure of the cost of acquiring a particular quantity of the product, and its subjective roles as an assessment of the quality of the product and an evaluation of gains or losses (deal vs. sacrifice) resulting from buying a “cheap” or an “expensive” product. This dual computation is done with respect to the internal reference price. 相似文献