全文获取类型
收费全文 | 136篇 |
免费 | 8篇 |
国内免费 | 42篇 |
专业分类
化学 | 131篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 37篇 |
物理学 | 15篇 |
出版年
2024年 | 1篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 4篇 |
2013年 | 15篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 4篇 |
2009年 | 14篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 2篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1985年 | 3篇 |
排序方式: 共有186条查询结果,搜索用时 15 毫秒
61.
62.
近年来,全钒氧化还原液流电池(VRFB)作为一种新型的储能电池备受关注,作为VRFB的核心材料,电极的活化一直都是研究的热点。碳素类材料,如碳毡和石墨毡,以其低成本和高性能被广泛用作钒电池电极。通过活化处理增加碳素类电极表面的含氧、含氮官能团或引入各种催化剂可以显著提高V(Ⅴ)/V(Ⅳ)和V(Ⅲ)/V(Ⅱ)电对氧化还原反应的电化学活性和可逆性,进而提高VRFB的总体性能,最终促进VRFB的商业化进程。本文综述了VRFB碳素类电极的氧化活化法、掺杂活化法和碳纳米催化剂活化法等几种常用活化方法的研究进展,并对VRFB碳素类电极的进一步研究和应用前景进行了展望。 相似文献
63.
Xiaojiang He Yufeng Ji Yu Jin Suli Kan Haidong Xia Jia Chen Bingqi Liang Hao Wu Kai Guo Zhenjiang Li 《Journal of polymer science. Part A, Polymer chemistry》2014,52(7):1009-1019
The ring‐opening polymerization (ROP) of trimethylene carbonate (TMC) using imidodiphosphoric acid (IDPA) as the organocatalyst and benzyl alcohol (BnOH) as the initiator has been investigated. The polymerization proceeded without decarboxylation to afford poly(trimethylene carbonate) (PTMiC) with controlled molecular weight and narrow polydispersity. 1H NMR, SEC, and MALDI‐TOF MS measurements of the obtained PTMC clearly indicated the quantitative incorporation of the initiator at the chain end. The controlled/living nature for the IDPA‐catalyzed ROP of TMC was confirmed by the kinetic and chain extension experiments. A bifunctional activation mechanism was proposed for IDPA catalysis based on NMR and FTIR studies. Additionally, 1,3‐propanediol, 1,1,1‐trimethylolpropane, and pentaerythritol were used as di‐ol, tri‐, and tetra‐ol initiators, producing the telechelic or star‐shaped polycarbonates with narrow polydispersity indices. The well‐defined diblock copolymers, poly(trimethylene carbonate)‐block‐poly(δ‐valerolactone) and poly(trimethylene carbonate)‐block‐poly(ε‐caprolactone), have been successfully synthesized by using the IDPA catalysis system. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1009–1019 相似文献
64.
Hu Peizhuo Liu Tonghuan Zhou Gen Duan Xiaojiang Wu Wangsuo 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(1):65-73
Preparing glass to be used as a radioactive waste immobilizer from municipal waste is the aim of this paper. Up to 90 wt% of municipal waste was obtained by burning the raw waste at 700 °C for 5 h; this were successfully vitrified into borosilicate and sodium borate glasses at ~1,200 °C. The long term behavior of such glass is one of the most important factors, which is determined by their durability in aqueous solution. Experimental durability data of the prepared glass immersed in ground water together with γ-irradiation was found to be affected according to the different irradiation doses. In addition, thermal analysis and glass surface morphology were investigated. The evolution of the damage on the studied properties was correlated to the changes in the glass network depending on their composition and irradiation dose. The results showed that glass matrix containing higher amount of municipal waste possess high durability and low thermal expansion after being gamma irradiated. The results showed that glass containing higher amount of municipal waste possess high durability and low thermal expansion after irradiation. 相似文献
65.
66.
Xiaojiang Tan 《数学学报(英文版)》1995,11(3):232-246
LetX be a generic smooth irreducible complex projective curve of genusg withg4. In this paper, we generalize the existence theorem of special divisors to high dimensional indecomposable vector bundles. We give a necessary and sufficient condition on the existence ofn-dimensional indecomposable vector bundlesE onX with det(E)=d, dimH
0(X,E)h. We also determine under what condition the set of all such vector bundles will be finite and how many elements it contains.Project partly supported by the National Natural Science Foundation of China. 相似文献
67.
A comparison of polyacetylenes (PA) prepared with rare earth(Ln) and titanium(Ti) basedcatalyst systems in regard to the isomerization rate, conductivity and doping behaviour is presented.It is found that PA synthesized with Ln-catalyst showed the lower isomerization rate than Ti-PA.Room temperature conductivity of I_2-doped Ln-PA is higher than that of Ti-PA under the sameconditions, this might related to the uniform conjugation length of Ln-PA. The difference in thedoping behaviors was observed for cis and trans PA films. and the complicated doping behavioursof cis-PA could be attributed to the simultaneously occurring isomerization reaction during doping. 相似文献
68.
69.
Zhao P Bai L Ma J Zeng Y Li L Zhang Y Lu C Dai H Wu Z Li Y Wu X Chen G Hao X Shen Y Deng Z Floss HG 《Chemistry & biology》2008,15(8):863-874
Ansamitocins are potent antitumor maytansinoids produced by Actinosynnema pretiosum. Their biosynthesis involves the initial assembly of a macrolactam polyketide, followed by a series of postpolyketide synthase (PKS) modifications. Three ansamitocin glycosides were isolated from A. pretiosum and fully characterized structurally as novel ansamitocin derivatives, carrying a beta-D-glucosyl group attached to the macrolactam amide nitrogen in place of the N-methyl group. By gene inactivation and complementation, asm25 was identified as the N-glycosyltransferase gene responsible for the macrolactam amide N-glycosylation of ansamitocins. Soluble, enzymatically active Asm25 protein was obtained from asm25-expressing E. coli by solubilization from inclusion bodies. Its optimal reaction conditions, including temperature, pH, metal ion requirement, and Km/Kcat, were determined. Asm25 also showed broad substrate specificity toward other ansamycins and synthetic indolin-2-ones. To the best of our knowledge, this represents the first in vitro characterization of a purified antibiotic N-glycosyltransferase. 相似文献
70.
Gang Chen Jiao Lin Jie Zhang Ya Wu Xuefan Gu Xiaojiang Hao Yu Zhang 《Comptes Rendus Chimie》2018,21(5):471-474
In this study, a series of 3-ethyl-3-hydroxy-indole-2-ones were synthesized through the addition reaction of Et2Zn and N-substituted isatin by an autocatalytic process. The synthesized compounds were characterized by NMR spectroscopy and mass spectrometry, and the reaction mechanism was discussed. The antitumor and neuroprotection activities of these compounds were evaluated. The results showed that several compounds display protection activity on H2O2-induced apoptosis of PC12 cells, which are more effective than that of (±)-α-tocopherol Vitamin E (VE). Moreover, these compounds also show antitumor activity against A549 and P388 cell lines. 相似文献