全文获取类型
收费全文 | 21265篇 |
免费 | 5269篇 |
国内免费 | 2842篇 |
专业分类
化学 | 9017篇 |
晶体学 | 167篇 |
力学 | 938篇 |
综合类 | 217篇 |
数学 | 2732篇 |
物理学 | 16305篇 |
出版年
2024年 | 60篇 |
2023年 | 291篇 |
2022年 | 653篇 |
2021年 | 758篇 |
2020年 | 777篇 |
2019年 | 648篇 |
2018年 | 626篇 |
2017年 | 669篇 |
2016年 | 880篇 |
2015年 | 883篇 |
2014年 | 1183篇 |
2013年 | 1756篇 |
2012年 | 1317篇 |
2011年 | 1546篇 |
2010年 | 1308篇 |
2009年 | 1377篇 |
2008年 | 1632篇 |
2007年 | 1614篇 |
2006年 | 1497篇 |
2005年 | 1347篇 |
2004年 | 1091篇 |
2003年 | 1081篇 |
2002年 | 995篇 |
2001年 | 794篇 |
2000年 | 812篇 |
1999年 | 662篇 |
1998年 | 573篇 |
1997年 | 444篇 |
1996年 | 345篇 |
1995年 | 272篇 |
1994年 | 236篇 |
1993年 | 189篇 |
1992年 | 180篇 |
1991年 | 145篇 |
1990年 | 100篇 |
1989年 | 125篇 |
1988年 | 70篇 |
1987年 | 62篇 |
1986年 | 48篇 |
1985年 | 69篇 |
1984年 | 44篇 |
1983年 | 23篇 |
1982年 | 42篇 |
1981年 | 27篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
Macromolecule Loading into Spherical,Elliptical, Star‐Like and Cubic Calcium Carbonate Carriers
下载免费PDF全文
![点击此处可从《Chemphyschem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Bogdan V. Parakhonskiy Dr. Alexey M. Yashchenok Dr. Senem Donatan Dr. Dmitry V. Volodkin Dr. Francesco Tessarolo Prof. Renzo Antolini Prof. Helmuth Möhwald Prof. Andre G. Skirtach 《Chemphyschem》2014,15(13):2817-2822
We fabricated calcium carbonate particles with spherical, elliptical, star‐like and cubical morphologies by varying relative salt concentrations and adding ethylene glycol as a solvent to slow down the rate of particle formation. The loading capacity of particles of different isotropic (spherical and cubical) and anisotropic (elliptical and star‐like) geometries is investigated, and the surface area of such carriers is analysed. Potential applications of such drug delivery carriers are highlighted. 相似文献
992.
采用高温固相合成法制备了Er3+,Yb3+双掺杂的GdOCl荧光材料,并研究其荧光性能。该双掺杂体系荧光粉吸收紫外光,发出红色(619 nm)和近红外(~979 nm)荧光。在这些荧光材料中,1个Er3+离子可以有效将其能量转移给2个Yb3+离子。通过改变Yb3+掺杂浓度,对比Gd0.998 5-yOCl∶0.0015Er3+,yYb3+中的Er3+的发射光谱和不同检测波长的荧光寿命变化特点,对Er3+-Yb3+发生量子剪裁的能级进行分析和指认,并计算了能量转化效率(η)和量子效率(Q)。正是由于具备这种荧光性能,该荧光材料体系有望在荧光太阳能收集器以及军事和医学的红外显示和探测技术中获得应用。 相似文献
993.
994.
Ting-Ting Dai ;Lei Liu ;Dong-Liang Tao ;Shi-Gang Li ;HongZhang ;Yu-Min Cui ;Yong-Zhong Wang ;Ji-Tang Chen ;Kun Zhang ;Wen-Zhong Sun ;Xiao-Yun Zhao ;gel Liu 《中国化学快报》2014,25(6):892-896
Absolute quantum yield (Ф) is one of the most important parameters to evaluate the potential of novel materials. Lanthanide complexes EuxGd1-x(TTA)3phens are synthesized with the ratio of Gd3+ dopant concentration ranging from 10% to 90% to improve the absolute quantum yield. EuxGd1-x(TTA)3phens possess similar infrared and ultraviolet spectra, showing that they have similar molecular structures. The absolute emission quantum yields of EuxGd1-x(TTA)3phens are determined using a fluoromax-4 spectrofluorometer equipped with an integrating sphere. The fluorescence lifetimes of the EuxGd1-x(TTA)3phens are measured in the same experiment. It was found that both absolute quantum yields and fluorescence lifetimes of EuxGd1-x(TTA)3phens are of quasi-periodic variation with the change of the Gd3. dopant concentrations. The absolute quantum efficiency and fluorescence lifetime vary with respect to the Gd content in an opposite fashion, indicating that the rate of energy absorption by the EuxGd1-x(TTA)3phens and the conversion to light energy is critical for the absolute quantum efficiency. The radiative rate constant Kr and non-radiative rate constant Knr are calculated. The dependence of Kr and Knr on the Gd3+ dopant concentrations is very similar to that of absolute quantum efficiency. The radiation rate constant Kr and absolute quantum efficiency have a linear relationship. 相似文献
995.
CO2-expanded liquid (CXL) is a mixture of organic solvent with high-pressure CO2 whose volume is increased by CO2 dissolved in it. CXLs have attracted attention as tunable solvents, because the solvent properties can be widely controlled by the pressure. The volume expansion and the solubility of CO2 were measured by near-infrared spectroscopy for 6 CXLs at various pressures up to 55 bar and 40 °C. The molarity of organic solvent was determined from the absorbance of the 3ν and 2ν + δ bands, and that of CO2 was obtained from the area of the 3ν3 band, whose peak shifted to higher frequency with increasing pressure due to a decrease in the molecular interaction around CO2. The expansion coefficient was shown to be an increasing function of the pressure with larger slope at higher pressure, and the mole fraction of CO2 in the liquid phase was an almost linearly increasing function of the pressure. The results were in quantitative agreement with the literature data measured by conventional sampling method, indicating the validity of the spectroscopic method. 相似文献
996.
Dongyi Liu Dr. Ahmed M. El-Zohry Maria Taddei Clemens Matt Laura Bussotti Dr. Zhijia Wang Prof. Jianzhang Zhao Prof. Omar F. Mohammed Prof. Mariangela Di Donato Prof. Stefan Weber 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11688-11696
We prepared conceptually novel, fully rigid, spiro compact electron donor (Rhodamine B, lactam form, RB)/acceptor (naphthalimide; NI) orthogonal dyad to attain the long-lived triplet charge-transfer (3CT) state, based on the electron spin control using spin-orbit charge transfer intersystem crossing (SOCT-ISC). Transient absorption (TA) spectra indicate the first charge separation (CS) takes place within 2.5 ps, subsequent SOCT-ISC takes 8 ns to produce the 3NI* state. Then the slow secondary CS (125 ns) gives the long-lived 3CT state (0.94 μs in deaerated n-hexane) with high energy level (ca. 2.12 eV). The cascade photophysical processes of the dyad upon photoexcitation are summarized as 1NI*→1CT→3NI*→3CT. With time-resolved electron paramagnetic resonance (TREPR) spectra, an EEEAAA electron-spin polarization pattern was observed for the naphthalimide-localized triplet state. Our spiro compact dyad structure and the electron spin-control approach is different to previous methods for which invoking transition-metal coordination or chromophores with intrinsic ISC ability is mandatory. 相似文献
997.
Kaitlyn A. Perez Cameron R. Rogers Emily A. Weiss 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(33):14195-14199
This Communication describes the use of CuInS2/ZnS quantum dots (QDs) as photocatalysts for the reductive deprotection of aryl sulfonyl-protected phenols. For a series of aryl sulfonates with electron-withdrawing substituents, the rate of deprotection for the corresponding phenyl aryl sulfonates increases with decreasing electrochemical potential for the two electron transfers within the catalytic cycle. The rate of deprotection for a substrate that contains a carboxylic acid, a known QD-binding group, is accelerated by more than a factor of ten from that expected from the electrochemical potential for the transformation, a result that suggests that formation of metastable electron donor–acceptor complexes provides a significant kinetic advantage. This deprotection method does not perturb the common NHBoc or toluenesulfonyl protecting groups and, as demonstrated with an estrone substrate, does not perturb proximate ketones, which are generally vulnerable to many chemical reduction methods used for this class of reactions. 相似文献
998.
Yufei Shu Dr. Xing Lin Dr. Haiyan Qin Zhuang Hu Prof. Yizheng Jin Prof. Xiaogang Peng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22496-22507
This article offers a materials-chemistry perspective for colloidal quantum dots (QDs) in the field of display, including QD-enhanced liquid-crystal-display (QD-LCD) and QD-based light-emitting-diodes (QLEDs) display. The rapid successes of QDs for display in the past five years are not accidental but have a deep root in both maturity of their synthetic chemistry and their unique chemical, optical, and optoelectronic properties. This article intends to discuss the natural match of QD emitters for display and chemical means to eventually bring about their full potential. 相似文献
999.
Dr. Song Jin Youxuan Ni Zhimeng Hao Prof. Kai Zhang Dr. Yong Lu Dr. Zhenhua Yan Dr. Yajuan Wei Dr. Ying-Rui Lu Dr. Ting-Shan Chan Prof. Jun Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22069-22073
A general graphene quantum dot-tethering design strategy to synthesize single-atom catalysts (SACs) is presented. The strategy is applicable to different metals (Cr, Mn, Fe, Co, Ni, Cu, and Zn) and supports (0D carbon nanosphere, 1D carbon nanotube, 2D graphene nanosheet, and 3D graphite foam) with the metal loading of 3.0–4.5 wt %. The direct transmission electron microscopy imaging and X-ray absorption spectra analyses confirm the atomic dispersed metal in carbon supports. Our study reveals that the abundant oxygenated groups for complexing metal ions and the rich defective sites for incorporating nitrogen are essential to realize the synthesis of SACs. Furthermore, the carbon nanotube supported Ni SACs exhibits high electrocatalytic activity for CO2 reduction with nearly 100 % CO selectivity. This universal strategy is expected to open up new research avenues to produce SACs for diverse electrocatalytic applications. 相似文献
1000.
Meng Lv Yang Yu María E. Sandoval-Salinas Prof. Jianhua Xu Dr. Zuhai Lei Prof. David Casanova Prof. Youjun Yang Prof. Jinquan Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(49):22363-22368
Spiro conjugation has been proposed to dictate the efficiency of charge transfer, which could directly affect the spin–orbit charge transfer intersystem crossing (SOCT-ISC) process. However, this process has yet to be exemplified. Herein, we prepared three spirobis[anthracene]diones, in which two benzophenone moieties are locked in close proximity and differentially functionalized to fine-tune the charge transfer state. Its feasibility for SOCT-ISC was theoretically predicted, then experimentally evaluated. Through fine-tuning the spiro conjugation coupling and varying the solvent dielectric constants, ISC rate constants were engineered to vary in a dynamic range of three orders of magnitude, from 7.8×108 s−1 to 1.0×1011 s−1, which is the highest ISC rate reported for SOCT-ISC system to our knowledge. Our findings substantiate the key factors for effective SOCT-ISC and offer a new avenue for the rational design of heavy atom free triplet sensitizers. 相似文献