全文获取类型
收费全文 | 4323篇 |
免费 | 139篇 |
国内免费 | 9篇 |
专业分类
化学 | 2855篇 |
晶体学 | 29篇 |
力学 | 123篇 |
综合类 | 5篇 |
数学 | 451篇 |
物理学 | 1008篇 |
出版年
2023年 | 29篇 |
2022年 | 98篇 |
2021年 | 133篇 |
2020年 | 113篇 |
2019年 | 136篇 |
2018年 | 133篇 |
2017年 | 94篇 |
2016年 | 187篇 |
2015年 | 136篇 |
2014年 | 157篇 |
2013年 | 286篇 |
2012年 | 297篇 |
2011年 | 327篇 |
2010年 | 232篇 |
2009年 | 241篇 |
2008年 | 285篇 |
2007年 | 257篇 |
2006年 | 199篇 |
2005年 | 150篇 |
2004年 | 127篇 |
2003年 | 93篇 |
2002年 | 103篇 |
2001年 | 75篇 |
2000年 | 60篇 |
1999年 | 40篇 |
1998年 | 43篇 |
1997年 | 33篇 |
1996年 | 25篇 |
1995年 | 19篇 |
1994年 | 39篇 |
1993年 | 33篇 |
1992年 | 36篇 |
1991年 | 20篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 13篇 |
1985年 | 11篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 21篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有4471条查询结果,搜索用时 15 毫秒
141.
Dr. Teng Zhang Dr. Yuichi Kitagawa Ryoma Moriake Pedro Paulo Ferreira da Rosa Dr. Md. Jahidul Islam Dr. Tomoki Yoneda Prof. Yasuhide Inokuma Dr. Koji Fushimi Prof. Yasuchika Hasegawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(58):14438-14443
In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent LnIII-silica nanomaterials. A novel EuIII-silica hybrid nanoparticle was developed by using a doubly binding TPPO−Si(OEt)3 (TPPO: triphenyl phosphine oxide) linker. The TPPO−Si(OEt)3 was confirmed by 1H, 31P, 29Si NMR spectroscopy and single-crystal X-ray analysis. Luminescent Eu(hfa)3 and Eu(tfc)3 moieties (hfa: hexafluoroacetylacetonate, tfc: 3-(trifluoromethylhydroxymethylene)camphorate) were fixed onto TPPO−Si(OEt)3-modified silica nanoparticles, producing Eu(hfa)3(TPPO−Si)2-SiO2 and Eu(tfc)3(TPPO−Si)2-SiO2, respectively. Eu(hfa)3(TPPO−Si)2−SiO2 exhibited the higher intrinsic luminescence quantum yield (93 %) and longer emission lifetime (0.98 ms), which is much larger than those of previously reported EuIII-based hybrid materials. Eu(tfc)3(TPPO−Si)2−SiO2 showed an extra-large intrinsic emission quantum yield (54 %), although the emission quantum yield for the precursor Eu(tfc)3(TPPO−Si(OEt)3)2 was found to be 39 %. These results confirmed that the TPPO−Si(OEt)3 linker is a promising candidate for development of EuIII-based luminescent materials. 相似文献
142.
Luiz Carlos Domingos Batista Thiago Izidoro Silva Santos José E. Lima Santos Djalma Ribeiro da Silva Carlos A. Martínez-Huitle 《Electroanalysis》2021,33(1):57-65
MOF-235 is presented as an orange powder, with crystals of the octahedral formation. It was already used as adsorbent to remove different compounds from water; however, no attempts have been published about the exploration of the MOF-235 application as electrochemical sensor for organic compounds yet. MOF-235 was synthetized and after that, it was characterized by SEM, XRD and FTIR. Graphite electrodes (GEs) were modified with different MOF-235 ratio (5 %, 7 %, 10 %, 12 % and 14 %) and these modified GEs were characterized by cyclic voltammetry (CV) measurements in order to determine the effect of MOF-235 concentration on the current response. Results indicated that, a significant improvement on the current response was attained at MOF-235(10 %)/GE respect to unmodified GE. This behavior is related to the pore structure and multiple active sites on the MOF surface. The performance of the MOF-235(10 %)/GE as electrochemical sensor for detecting catechol was assessed by differential pulse voltammetry (DPV). Catechol detection response of MOF-based sensor provided a detection limit of about 12.79 μmol L−1 with a correlation coefficient (R2) of about 0.9928 ranging from 12 to 514 μmol L−1. Finally, MOF-235(10 %)/GE was used to determine catechol in real water matrixes. 相似文献
143.
144.
Denise Tofanello Gimenes Polyana Fernandes Pereira Rafael Rodrigues Cunha Rodrigo Amorim Bezerra da Silva Rodrigo Alejandro Abarza Munoz Eduardo Mathias Richter 《Electroanalysis》2012,24(9):1805-1810
In this study, we describe for the first time the application of an internal standard method to compensate for random errors associated with the injection procedure in batch injection analysis (BIA) systems with multiple pulse amperometric detection. A sequence of potential pulses was selected in such a way that the internal standard (IS) compound was detected individually at one potential pulse and both the IS and analyte, were detected at another potential pulse. The current ratio (IIS+analyte/IIS) was used in the construction of the calibration curve and then to compensate for random errors. The use of disposable syringes or manual pipettes in BIA systems increases the robustness of the method and dispenses with skilled operators. 相似文献
145.
146.
147.
148.
149.
150.
Jaume Llibre Paulo R. da Silva Marco A. Teixeira 《Journal of Dynamics and Differential Equations》2012,24(1):1-12
In this article we establish an interaction between non-smooth systems, geometric singular perturbation theory and synchronization
phenomena. We find conditions for a non-smooth vector fields be locally synchronized. Moreover its regularization provide
a singular perturbation problem with attracting critical manifold. We also state a result about the synchronization which
occurs in the regularization of the fold-fold case. We restrict ourselves to the 3-dimensional systems (ℓ = 3) and consider the case known as a T-singularity. 相似文献