全文获取类型
收费全文 | 121篇 |
免费 | 24篇 |
国内免费 | 25篇 |
专业分类
化学 | 107篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 2篇 |
物理学 | 54篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 12篇 |
2014年 | 12篇 |
2013年 | 17篇 |
2012年 | 4篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 10篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 10篇 |
2003年 | 3篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有170条查询结果,搜索用时 15 毫秒
41.
利用溶剂热法合成了不同锂含量的MOF-5(x Li-MOF-5,x=0,1,3,5)。在MOF-5结晶过程中,锂离子被合并入其骨架结构中。实验表明,合并入骨架的锂能够改变MOF-5的结构和表面化学性质。不同的x Li-MOF-5能够不同程度降低骨架相互穿插的程度从而导致其吸附分离能力的大幅改变。其中,3Li-MOF-5具有最高的二氧化碳捕获能力(5.47 mmol·g-1),对40%CO2/60%CH4混合气体具有最优吸附选择性。 相似文献
42.
A comparison is made between calculations performed nonrelativistically and relativistically for W, Re, Os, Ir, Pt, Au and Hg as substitutional impurities in silicon. The calculations were carried out using the relativistic extended Hückel method. The direct and indirect relativistic effects upon the 5d-like levels and band-gap levels are analysed. 相似文献
43.
Tsuneyuki Sato Naoki Higashida Tomohiro Hirano Makiko Seno 《Journal of polymer science. Part A, Polymer chemistry》2004,42(7):1609-1617
The copolymerization of divinylbenzene (DVB) and N‐isopropylacrylamide (NIPAm) with dimethyl 2,2′‐azobisisobutyrate of a concentration as high as 0.50 mol/L proceeded homogeneously without any gelation at 80 °C in N,N‐dimethylformamide, where the concentrations of DVB and NIPAm were 0.15 and 0.50 mol/L. The copolymer yield increased with time and leveled off over 50 min. Although DVB was consumed more rapidly than NIPAm, both comonomers were completely consumed in 50 min. The homogeneous polymerization system at 80 °C involved electron spin resonance‐observable propagating polymer radicals, the total concentration of which increased with time. The resulting copolymer was soluble in tetrahydrofuran, chloroform, acetone, ethyl acetate, acetonitrile, N,N‐dimethylformamide, dimethyl sulfoxide, and methanol, but insoluble in benzene, n‐hexane, and water. The copolymer showed an upper critical solution temperature (50 °C on cooling) in a methanol–water [11:3 (v/v)] mixture. Dimethyl 2,2′‐azobisisobutyrate fragments as high as 37–45 mol % were incorporated as terminal groups in the copolymers through initiation and primary radical termination. The contents of DVB and NIPAm were 10–30 mol % and 30–50 mol %, respectively. The intrinsic viscosity of the copolymer was very low (0.09 dL/g) at 30 °C in tetrahydrofuran despite high weight‐average molecular weight (1.2 × l06 by multi‐angle laser light scattering). These results indicate that the copolymer was of hyperbranched structure. By transmission electron microscopy observation, the individual copolymer molecules were visualized as nanoparticle of 6–20 nm. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1609–1617, 2004 相似文献
44.
L. Landi L. Cabrini B. Tadolini T. Fahmi P. Pasquali 《Applied biochemistry and biotechnology》1985,11(2):123-132
The incorporation of Coenzyme Q† homologs into phospholipid vesicles to achieve a concentration close to the quinone content
of mitochondria has been studied with different methods. The results obtained can be summarized as follows: (a) stirring does
not lead to comparable incorporation of the various CoQs tested; (b) ultrasonic irradiation results in a homogeneous incorporation
both of the naturally occurring homologs of Coenzyme Q (polyisoprenoid chainlength ranging from ten to six units) and of the
nonphysiological shorter chain homologs; (c) ethanol injection, which is a simple, rapid, and inexpensive technique, gives
results comparable to those obtained by ultrasonication. 相似文献
45.
Niobium containing aluminophosphate materials with AEL structure were prepared by the hydrothermal method. The chemical composition
of the hydrogel was: 1 DIPA: 1 Al2O3: (1-x) P2O5: x Nb2O5: 80 H2O, with x=0.025, 0.050, 0.075 and 0.100. The crystallization was carried out at temperature of 170°C for 72 h. The materials
obtained were characterized by XRF, DRX, FTIR, TG and measurements of acidity. The characterization of the catalytic active
sites were carried out in the isopropanol dehydration at temperature of 400°C, and WHSV of 1.6, 3.2, 4.8, 6.4 and 8.0 h-1 . The samples showed good catalytic activity with selectivity to propene.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
46.
采用等离子体增强化学气相沉积技术(PECVD)通过改变NH3流量制备出不同含氮量N型富硅氮化硅硅薄膜。利用Raman散射、红外吸收、紫外-可见光分光光度计及暗态I-V测量等技术分析了氮掺入对薄膜微观结构以及光电特性的影响。结果显示,随着NH3的增加,薄膜由微晶硅向纳米硅结构转变,薄膜中晶粒尺寸减少,晶化度降低,微观结构有序性降低,所对应薄膜光学带隙增大,而带尾分布变窄。同时,红外吸收谱分析表明,Si—N键合密度增加,P掺杂受阻。暗态I-V测量显示,薄膜电导率随着NH3掺入整体较微晶硅降低,但随NH3增加,电导率受到迁移率和载流子浓度等特征共同作用先降低后变大,揭示了影响薄膜电导率的机制存在一定的竞争,然而过高的非晶网络结构将增大载流子的复合导致薄膜电导率显著降低。 相似文献
47.
半导体激光准直仪及其激光束漂移补偿研究 总被引:1,自引:0,他引:1
半导体激光器和线阵CCD是进行准直测量的关键部件,半导体激光束的漂移是影响测量精度的一个因素.采用双激光束合并补偿和平面镜反射方法,缩短了激光束在空气中的传播途径,降低了空气扰动对激光漂移的影响,使得激光准直仪精度提高50%. 相似文献
48.
Puromycin Analogues Capable of Multiplexed Imaging and Profiling of Protein Synthesis and Dynamics in Live Cells and Neurons 下载免费PDF全文
Dr. Jingyan Ge Dr. Cheng‐Wu Zhang Xue Wen Ng Bo Peng Sijun Pan Shubo Du Danyang Wang Prof. Dr. Lin Li Dr. Kah‐Leong Lim Prof. Dr. Thorsten Wohland Prof. Dr. Shao Q. Yao 《Angewandte Chemie (International ed. in English)》2016,55(16):4933-4937
Newly synthesized proteins constitute an important subset of the proteome involved in every cellular process, yet existing chemical tools used to study them have major shortcomings. Herein we report a suite of cell‐permeable puromycin analogues capable of being metabolically incorporated into newly synthesized proteins in different mammalian cells, including neuronal cells. Subsequent labeling with suitable bioorthogonal reporters, in both fixed and live cells, enabled direct imaging and enrichment of these proteins. By taking advantage of the mutually orthogonal reactivity of these analogues, we showed multiplexed labeling of different protein populations, as well as quantitative measurements of protein dynamics by fluorescence correlation spectroscopy, could be achieved in live‐cell environments. 相似文献
49.
50.
Jincemon Cyriac Rahul Mundiyaniyil Thankachan B. Raneesh D. Sanyal Nandakumar Kalarikkal 《哲学杂志》2015,95(35):4000-4022
The replacement of cations at the B-sites in the spinel ferrite ZnFe2O4 by Mn3+ ions brings in several interesting changes, the most striking among them being a transformation from the spinel cubic structure to a body-centered tetragonal one. Concomitantly, there are variations in the nanocrystallite sizes and also in the lattice parameters. These are examined through high-precision X-ray diffraction measurements and transmission electron microscopic analysis. A more interesting aspect is the success of positron annihilation spectroscopy comprising of the measurements of positron lifetime and coincidence Doppler broadening measurements in understanding the effects of cation replacement and the resultant generation of vacancy-type defects. There are definite changes in the positron lifetimes and intensities which show positron trapping in trivacancy-type defect clusters and the nanocrystallite surfaces. The presence of ortho-positronium atoms within the extended intercrystallite region is also identified, although in small concentrations. The cubic to tetragonal transformation is indicated through definite decrease in the values of the positron lifetimes. We also performed a model analysis to predict the expected effect of substitution on the positron lifetime in the bulk of the sample and the experimentally obtained positron lifetimes significantly differed, indirectly hinting at the possibility of a structural transformation. Finally, Mössbauer spectroscopic studies have indicated a ferromagnetic nature for one of the samples, i.e. the one with Mn3+ doping concentration x = 0.4, which incidentally had the lowest crystallite size ~10 nm. 相似文献