全文获取类型
收费全文 | 1409篇 |
免费 | 23篇 |
专业分类
化学 | 1224篇 |
晶体学 | 9篇 |
力学 | 4篇 |
数学 | 30篇 |
物理学 | 165篇 |
出版年
2020年 | 8篇 |
2016年 | 9篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 22篇 |
2012年 | 25篇 |
2011年 | 26篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 43篇 |
2007年 | 26篇 |
2006年 | 31篇 |
2005年 | 24篇 |
2004年 | 20篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 13篇 |
1993年 | 20篇 |
1991年 | 13篇 |
1989年 | 16篇 |
1987年 | 11篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1978年 | 14篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1969年 | 10篇 |
1968年 | 31篇 |
1967年 | 59篇 |
1966年 | 72篇 |
1965年 | 64篇 |
1964年 | 57篇 |
1963年 | 33篇 |
1962年 | 48篇 |
1961年 | 12篇 |
1960年 | 27篇 |
1959年 | 27篇 |
1958年 | 17篇 |
1957年 | 20篇 |
1956年 | 69篇 |
1955年 | 135篇 |
1954年 | 81篇 |
1920年 | 7篇 |
排序方式: 共有1432条查询结果,搜索用时 15 毫秒
21.
Dr. Santiago Alonso-Gil Dr. Kamil Parkan Dr. Jakub Kaminský Dr. Radek Pohl Dr. Takatsugu Miyazaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(14):e202200148
The conformational changes in a sugar moiety along the hydrolytic pathway are key to understand the mechanism of glycoside hydrolases (GHs) and to design new inhibitors. The two predominant itineraries for mannosidases go via OS2→B2,5→1S5 and 3S1→3H4→1C4. For the CAZy family 92, the conformational itinerary was unknown. Published complexes of Bacteroides thetaiotaomicron GH92 catalyst with a S-glycoside and mannoimidazole indicate a 4C1→4H5/1S5→1S5 mechanism. However, as observed with the GH125 family, S-glycosides may not act always as good mimics of GH's natural substrate. Here we present a cooperative study between computations and experiments where our results predict the E5→B2,5/1S5→1S5 pathway for GH92 enzymes. Furthermore, we demonstrate the Michaelis complex mimicry of a new kind of C-disaccharides, whose biochemical applicability was still a chimera. 相似文献
22.
Annika Pohl Gunnar Westin Kjell Jansson 《Journal of Sol-Gel Science and Technology》2003,26(1-3):257-260
The first purely alkoxide-based sol-gel route to nano-phase powders and thin films of perovskite La0.75Sr0.25MnO3 is described. The phase and microstructure evolution on heat treatment of free gel films to form the target nano-phase oxide were investigated by TGA, IR spectroscopy, powder XRD, SEM and TEM-EDS. The xerogel consisted of a hydrated oxo-carbonate, without remaining alkoxo groups or solvent. Heating at 5°C·min–1 decomposed the carbonate groups and yielded the pure perovskite La0.75Sr0.25MnO3 at 760°C. The cell dimensions were virtually unchanged from the first observation of perovskite at 680°C, to 1000°C, 4 h. The monoclinic cell of La0.75Sr0.25MnO3 obtained at 1000°C, 4 h, had the dimensions a = 5.475(1), b = 5.504(2), c = 7.771(1) Å, = 90.50(2), fitting the literature data quite well. Crack-free, homogenous, 150 nm thick La0.75Sr0.25MnO3 films were prepared by spin-coating Si/SiO2/TiO2/Pt and polycrystalline -Al2O3 substrates with a 0.6 M alkoxide solution, followed by heating at 5°C·min–1 to 800°C, 30 min. 相似文献
23.
US Environmental Protection Agency Method 300.0 specifies the use of an IonPac AS4A anion-exchange column with a carbonate-hydrogencarbonate eluent and suppressed conductivity detection for the determination of inorganic anions in environmental waters by ion chromatography. Hydroxide eluents have not typically been used for the routine analysis of common inorganic anions due to the lack of an appropriate hydroxide selective column and the difficulty in preparing contaminant free hydroxide eluents. The use of ion chromatography with a hydroxide-selective IonPac AS17 column, automated eluent generation and potassium hydroxide gradient represents a new approach to the routine determination of inorganic anions in environmental waters. This new approach, which is a modification of Method 300.0, allows equivalent method performance with improved linearity, precision, and method detection limits. The AS17 column provides superior retention of fluoride from the column void volume and improved resolution from small organic acids, such as formate and acetate, compared to the AS4A column. Quantitative recoveries were obtained for all the common inorganic anions spiked into typical environmental waters using this new approach, and the Performance Based Measurement System Tier 1 method validation quality control acceptance criteria are well within the acceptable ranges defined by Method 300.0. In addition, the EG40 eluent generator eliminates the need to manually prepare eluents, increasing the level of automation and ease-of-use of the ion chromatography system. 相似文献
24.
Interface Engineering of MoS2/Ni3S2 Heterostructures for Highly Enhanced Electrochemical Overall‐Water‐Splitting Activity 下载免费PDF全文
Dr. Jian Zhang Dr. Tao Wang Dr. Darius Pohl Dr. Bernd Rellinghaus Dr. Renhao Dong Dr. Shaohua Liu Dr. Xiaodong Zhuang Prof. Xinliang Feng 《Angewandte Chemie (International ed. in English)》2016,55(23):6702-6707
To achieve sustainable production of H2 fuel through water splitting, low‐cost electrocatalysts for the hydrogen‐evolution reaction (HER) and the oxygen‐evolution reaction (OER) are required to replace Pt and IrO2 catalysts. Herein, for the first time, we present the interface engineering of novel MoS2/Ni3S2 heterostructures, in which abundant interfaces are formed. For OER, such MoS2/Ni3S2 heterostructures show an extremely low overpotential of ca. 218 mV at 10 mA cm?2, which is superior to that of the state‐of‐the‐art OER electrocatalysts. Using MoS2/Ni3S2 heterostructures as bifunctional electrocatalysts, an alkali electrolyzer delivers a current density of 10 mA cm?2 at a very low cell voltage of ca. 1.56 V. In combination with DFT calculations, this study demonstrates that the constructed interfaces synergistically favor the chemisorption of hydrogen and oxygen‐containing intermediates, thus accelerating the overall electrochemical water splitting. 相似文献
25.
26.
A novel approach for the syntheses of carbene adduct 4 is reported. A ring-enlargement strategy was employed for the synthesis of precursors 5 and 6 and established the mechanism of the formation of azulene derivative 6. Synthesis of target precursor 13, a novel precursor for the synthesis of new mesogenic materials, and its various halogenated derivatives (14–16) was carried out. 相似文献
27.
Jana Balintová Medard Plucnara Pavlína Vidláková Dr. Radek Pohl Dr. Luděk Havran Prof. Dr. Miroslav Fojta Prof. Dr. Michal Hocek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12720-12731
Benzofurazane has been attached to nucleosides and dNTPs, either directly or through an acetylene linker, as a new redox label for electrochemical analysis of nucleotide sequences. Primer extension incorporation of the benzofurazane‐modified dNTPs by polymerases has been developed for the construction of labeled oligonucleotide probes. In combination with nitrophenyl and aminophenyl labels, we have successfully developed a three‐potential coding of DNA bases and have explored the relevant electrochemical potentials. The combination of benzofurazane and nitrophenyl reducible labels has proved to be excellent for ratiometric analysis of nucleotide sequences and is suitable for bioanalytical applications. 相似文献
28.
29.
30.