全文获取类型
收费全文 | 886篇 |
免费 | 11篇 |
国内免费 | 3篇 |
专业分类
化学 | 601篇 |
晶体学 | 9篇 |
力学 | 14篇 |
数学 | 168篇 |
物理学 | 108篇 |
出版年
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 6篇 |
2018年 | 7篇 |
2016年 | 14篇 |
2015年 | 12篇 |
2014年 | 9篇 |
2013年 | 55篇 |
2012年 | 27篇 |
2011年 | 32篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 18篇 |
2007年 | 28篇 |
2006年 | 28篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 39篇 |
2002年 | 28篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1998年 | 6篇 |
1997年 | 19篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1985年 | 18篇 |
1984年 | 31篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 25篇 |
1980年 | 22篇 |
1979年 | 13篇 |
1978年 | 22篇 |
1977年 | 22篇 |
1976年 | 15篇 |
1975年 | 13篇 |
1974年 | 13篇 |
1973年 | 40篇 |
1972年 | 7篇 |
1970年 | 8篇 |
1969年 | 7篇 |
1968年 | 8篇 |
1934年 | 9篇 |
排序方式: 共有900条查询结果,搜索用时 15 毫秒
891.
Pujals S Fernandez-Carneado J Kogan MJ Martinez J Cavelier F Giralt E 《Journal of the American Chemical Society》2006,128(26):8479-8483
The results presented here show that elementary design enhancements have led to a 20-fold increase in the cellular uptake properties of a Pro-rich cell-penetrating peptide. These results are relevant not only due to the increasing interest in using CPPs as molecular shuttles for intracellular drug delivery but also because they illustrate the power of combining conformational analysis with rational design to modulate the behavior of biologically active compounds. 相似文献
892.
893.
The ability to quantify and visualize submicrometer-scale oscillatory motions of objects in three dimensions has a wide range of application in acoustics, materials sciences, and medical imaging. Here we demonstrate that volumetric snapshots of rapid periodic motion can be captured using optical coherence tomography (OCT) with subnanometer-scale motion sensitivity and microsecond-scale temporal resolution. This technique, termed OCT vibrography, was applied to generate time-resolved volumetric vibrographs of a miniature drum driven acoustically at several kilohertz. 相似文献
894.
895.
Thermotropic poly(2,2′-oxydiethylene fumarate)-block-poly(2-methyl-1,4-phenylene fumarate) C is synthesized by interfacial polycondensation of α,ω-dichlorocarbonyl-poly(2,2′-oxydiethylene fumarate) and fumaroyl chloride with 2-methyl-1,4-dihydroxybenzene. A study of each block is carried out on the corresponding homopolymers as models of flexible A and rigid B blocks. Copolymer C and models are characterized by 1H and 13C NMR, I.R. spectroscopy, SEC, DSC, TGA, X-Ray diffractometry and electron microscopy. A phase segregation is observed in C when B content is above 50%. Copolymer C exhibits a nematic mesophase and can be crosslinked. 相似文献
896.
Andrei A. Tolmachev Sergei I. Dovgopoly Aleksandr N. Kostyuk Ernest S. Kozlov Aleksei O. Pushechnikov Wolfgang Holzer 《Heteroatom Chemistry》1999,10(5):391-398
1,3,3‐Trimethyl‐2‐(1‐R‐3‐methyl‐5‐pyrazolyliminoethylidene)indolines were shown to undergo phosphorylation with phosphorus(III) halides at the two nucleophilic carbon centers to give fused 1,4‐azaphosphinine ring systems. Chemical properties of the synthesized compounds were characterized. For some representative compounds, detailed NMR spectroscopic investigations were performed, including the determination of 31P, 1H and 31P, 13C coupling constants. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 391–398, 1999 相似文献
897.
898.
The synthesis of aromatic copolyamidethioethers by reaction of dichlorobenzanilides with Na2S has been studied. The reactivity of chlorine atoms is strongly dependent on the nature of the substituent in para position. It is related to the 13C NMR shifts of the relative carbons-the more deshielded, the more reactive-and hence to charge densities, agreing with aromatic nucleophilic substitution mechanisms. The results are discussed in relation to the various mechanisms which have been put forward for the reaction of Na2S with 1, 4-dichlorobenzene (PPS synthesis). 相似文献
899.
Yicheng Li Dr. Ernest Pahuyo Delmo Guoyu Hou Xianglong Cui Prof. Ming Zhao Prof. Zhihong Tian Prof. Yu Zhang Prof. Minhua Shao 《Angewandte Chemie (International ed. in English)》2023,62(49):e202313522
Electrochemical carbon dioxide reduction reaction (CO2RR) to produce valuable chemicals is a promising pathway to alleviate the energy crisis and global warming issues. However, simultaneously achieving high Faradaic efficiency (FE) and current densities of CO2RR in a wide potential range remains as a huge challenge for practical implements. Herein, we demonstrate that incorporating bismuth-based (BH) catalysts with L-histidine, a common amino acid molecule of proteins, is an effective strategy to overcome the inherent trade-off between the activity and selectivity. Benefiting from the significantly enhanced CO2 adsorption capability and promoted electron-rich nature by L-histidine integrity, the BH catalyst exhibits excellent FEformate in the unprecedented wide potential windows (>90 % within −0.1–−1.8 V and >95 % within −0.2–−1.6 V versus reversible hydrogen electrode, RHE). Excellent CO2RR performance can still be achieved under the low-concentration CO2 feeding (e.g., 20 vol.%). Besides, an extremely low onset potential of −0.05 VRHE (close to the theoretical thermodynamic potential of −0.02 VRHE) was detected by in situ ultraviolet-visible (UV-Vis) measurements, together with stable operation over 50 h with preserved FEformate of ≈95 % and high partial current density of 326.2 mA cm−2 at −1.0 VRHE. 相似文献
900.
Andrew A. Tolmachev Alexander A. Yurchenko Ernest S. Kozlov Anatoliy S. Merkulov Marina G. Semenova Aleksander M. Pinchuk 《Heteroatom Chemistry》1995,6(5):419-432
The reaction of phosphorus(III) halides with imidazo[1,2-a]pyridines in the presence of bases leads to the formation of 3-phosphorylated imidazo[1,2-a]pyridines. The reaction proceeds in high yield and requires no catalysts. In the compounds obtained, in contrast to phosphorylated indolizines, the phosphorus–heterocycle bond is stable and not cleaved by dry hydrogen chloride, alcohols, or water. Imidazo[1,2-a]pyridines with the phosphinic and phosphinous groups can be alkylated both at the phosphorus and at the nitrogen atom of the heterocycle, the alkylation direction being dependent on the strength of the alkylation reagent used. © 1995 John Wiley & Sons, Inc. 相似文献