全文获取类型
收费全文 | 2408篇 |
免费 | 135篇 |
国内免费 | 1篇 |
专业分类
化学 | 1596篇 |
晶体学 | 13篇 |
力学 | 76篇 |
数学 | 228篇 |
物理学 | 631篇 |
出版年
2023年 | 23篇 |
2022年 | 17篇 |
2021年 | 31篇 |
2020年 | 35篇 |
2019年 | 17篇 |
2017年 | 34篇 |
2016年 | 69篇 |
2015年 | 67篇 |
2014年 | 62篇 |
2013年 | 92篇 |
2012年 | 124篇 |
2011年 | 161篇 |
2010年 | 70篇 |
2009年 | 68篇 |
2008年 | 132篇 |
2007年 | 130篇 |
2006年 | 106篇 |
2005年 | 106篇 |
2004年 | 78篇 |
2003年 | 81篇 |
2002年 | 75篇 |
2001年 | 49篇 |
2000年 | 38篇 |
1999年 | 20篇 |
1998年 | 21篇 |
1997年 | 18篇 |
1996年 | 21篇 |
1995年 | 24篇 |
1994年 | 24篇 |
1993年 | 33篇 |
1992年 | 27篇 |
1991年 | 24篇 |
1990年 | 23篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 25篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 23篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 16篇 |
1978年 | 26篇 |
1977年 | 19篇 |
1976年 | 22篇 |
1974年 | 15篇 |
1973年 | 18篇 |
1971年 | 15篇 |
排序方式: 共有2544条查询结果,搜索用时 171 毫秒
121.
Jannik Brückmann Dr. Carolin Müller Ilse Friedländer Dr. Alexander K. Mengele Prof. Kalina Peneva Prof. Benjamin Dietzek-Ivanšić Prof. Sven Rau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(61):e202201931
The ambitious goal of artificial photosynthesis is to develop active systems that mimic nature and use light to split water into hydrogen and oxygen. Intramolecular design concepts are particularly promising. Herein, we firstly present an intramolecular photocatalyst integrating a perylene-based light-harvesting moiety and a catalytic rhodium center ( RhIIIphenPer ). The excited-state dynamics were investigated by means of steady-state and time-resolved absorption and emission spectroscopy. The studies reveal that photoexcitation of RhIIIphenPer yields the formation of a charge-separated intermediate, namely RhIIphenPer ⋅ + , that results in a catalytically active species in the presence of protons. 相似文献
122.
Sebastian Wöllner Timothy Nowak Dr. Gui-Rong Zhang Dr. Nils Rockstroh Dr. Hanadi Ghanem Prof. Dr. Stefan Rosiwal Prof. Dr. Angelika Brückner Prof. Dr. Bastian J. M. Etzold 《ChemistryOpen》2021,10(5):600-606
Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) offers a renewable approach to produce the value-added platform chemical 2,5-furandicarboxylic acid (FDCA). The key for the economic viability of this approach is to develop active and selective electrocatalysts. Nevertheless, a reliable catalyst evaluation protocol is still missing, leading to elusive conclusions on criteria for a high-performing catalyst. Herein, we demonstrate that besides the catalyst identity, secondary parameters such as materials of conductive substrates for the working electrode, concentration of the supporting electrolyte, and electrolyzer configurations have profound impact on the catalyst performance and thus need to be optimized before assessing the true activity of a catalyst. Moreover, we highlight the importance of those secondary parameters in suppressing side reactions, which has long been overlooked. The protocol is validated by evaluating the performance of free-standing Cu-foam, and CuCoO modified with NaPO2H2 and Ni, which were immobilized on boron-doped diamond (BDD) electrodes. Recommended practices and figure of merits in carefully evaluating the catalyst performance are proposed. 相似文献
123.
Discontinuous changes of the lattice parameters at the Mott metal-insulator transition are detected by high-resolution dilatometry on deuterated crystals of the layered organic conductor kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Br. The uniaxial expansivities uncover a striking and unexpected anisotropy, notably a zero effect along the in-plane c axis along which the electronic interactions are relatively strong. A huge thermal expansion anomaly is observed near the end point of the first-order transition line enabling us to explore the critical behavior with very high sensitivity. The analysis yields critical fluctuations with an exponent alpha approximately 0.8+/-0.15 at odds with the novel criticality recently proposed for these materials [Kagawa et al., Nature (London) 436, 534 (2005)]. Our data suggest an intricate role of the lattice degrees of freedom in the Mott transition for the present materials. 相似文献
124.
J. Brüning 《The European physical journal. Special topics》2007,145(1):181-189
We describe the main lines of mathematical research dealing
with nodal sets of eigenfunctions since the days of Chladni. We
present the material in a form hopefully suited to a nonspecialized
but mathematically educated audience. 相似文献
125.
We propose what we believe to be a novel, refined model of the angular sensitivity function of artificial apposition compound eyes. Compared with the formerly used Gaussian approximation that was derived for natural compound eyes, our model is better suited to describe the resolution capacity of artificial compound eyes accounting for the cylindrical sensitivity function of technical receptors. It is shown that this analytic model is valid over a broad range of parameters of the optical system, which was not fulfilled by one of the previous models. Finally, an analytic approach is used to derive the modulation transfer function of these multichannel imaging systems. 相似文献
126.
Ekta Mishra Jill L. Worlinsky Christian Brückner Victor Ryzhov 《Journal of the American Society for Mass Spectrometry》2014,25(1):18-29
Free base and cobalt(II) complexes of six meso-tetraphenylporphyrinoids containing nonpyrrolic heterocycles and of three meso-thienylporphyrins were investigated using electrospray ionization tandem mass spectrometry (ESI-MS/MS). Their fragmentation was studied in a quadrupole ion trap as a function of the porphyrinoid macrocycle structure and compared with the fragmentation behavior of the benchmark compound meso-tetraphenylporphyrin. In situ oxidation of the neutral cobalt(II) complexes under ESI conditions produced singly charged cobalt(III) porphyrinoid ions; the free bases were ionized by protonation. For the porphyrinoids with an intact porphyrin core, the major fragmentation pathways observed were the losses of the meso-substituent (for meso-phenyl groups) and characteristic fragmentations of one or more meso-substituents (for the meso-thienyl group). Complex fragmentation pathways were observed for porphyrinoids with modifications to the porphyrin core but chemically reasonable structures could be assigned to most fragments, thus delineating general patterns for the behavior of pyrrole-modified porphyrins under CID conditions. Figure
? 相似文献
127.
Petr Brázda Eva Večerníková Eva Pližingrová Adriana Lančok Daniel Nižňanský 《Journal of Thermal Analysis and Calorimetry》2014,117(1):85-91
Thermal behavior of highly crystalline ε-Fe2O3 nanoparticles of different apparent crystallite sizes was characterized using thermogravimetry, differential thermal analysis, and analysis of evolved gas by mass spectrometry. Phase composition of the samples was monitored ex situ by X-ray powder diffraction. The results show that the thermal stability of this metastable iron oxide polymorph decreases with increasing particle size. For the particle diameter of 19(2) nm, the transformation temperature was equal to 794(5) °C, while for 28(2) nm only 755(10) °C. Surface of the nanoparticles contained adsorbed water and carbon dioxide. Elimination of these species proceeds in two steps. Water is removed at temperatures below 200 °C and CO2 in the temperature range between 200 and 450 °C. 相似文献
128.
Mono‐ and Bis(pyrrolo)tetrathiafulvalene Derivatives Tethered to C60: Synthesis,Photophysical Studies,and Self‐Assembled Monolayers
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Marta Vico Solano Dr. Eduardo Antonio Della Pia Dr. Martyn Jevric Christina Schubert Xintai Wang Dr. Cornelia van der Pol Prof. Dr. Anders Kadziola Prof. Dr. Kasper Nørgaard Prof. Dr. Dirk M. Guldi Prof. Dr. Mogens Brøndsted Nielsen Prof. Dr. Jan O. Jeppesen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(32):9918-9929
A series of mono‐ (MPTTF) and bis(pyrrolo)tetrathiafulvalene (BPTTF) derivatives tethered to one or two C60 moieties was synthesized and characterized. The synthetic strategy for these dumbbell‐shaped compounds was based on a 1,3‐dipolar cycloaddition reaction between aldehyde‐functionalized MPTTF/BPTTF derivatives, two different tailor‐made amino acids, and C60. Electronic communication between the MPTTF/BPTTF units and the C60 moieties was studied by a variety of techniques including cyclic voltammetry and absorption spectroscopy. These solution‐based studies indicated no observable electronic communication between the MPTTF/BPTTF units and the C60 moieties. In addition, femtosecond and nanosecond transient absorption spectroscopy revealed, rather surprisingly, that no charge transfer from the MPTTF/BPTTF units to the C60 moieties takes place on excitation of the fullerene moiety. Finally, it was shown that the MPTTF–C60 and C60–BPTTF‐C60 dyad and triad molecules formed self‐assembled monolayers on a Au(111) surface by anchoring to C60. 相似文献
129.
Steffen M. Brülls Dr. Valentina Cantatore Zhenping Wang Dr. Pui Lam Tam Dr. Per Malmberg Jessica Stubbe Prof. Dr. Biprajit Sarkar Prof. Dr. Itai Panas Prof. Dr. Jerker Mårtensson Prof. Dr. Siegfried Eigler 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(29):6694-6702
Hybridizing graphene and molecules possess a high potential for developing materials for new applications. However, new methods to characterize such hybrids must be developed. Herein, the wet-chemical non-covalent functionalization of graphene with cationic π-systems is presented and the interaction between graphene and the molecules is characterized in detail. A series of tricationic benzimidazolium salts with various steric demand and counterions was synthesized, characterized and used for the fabrication of graphene hybrids. Subsequently, the doping effects were studied. The molecules are adsorbed onto graphene and studied by Raman spectroscopy, XPS as well as ToF-SIMS. The charged π-systems show a p-doping effect on the underlying graphene. Consequently, the tricationic molecules are reduced through a partial electron transfer process from graphene, a process which is accompanied by the loss of counterions. DFT calculations support this hypothesis and the strong p-doping could be confirmed in fabricated monolayer graphene/hybrid FET devices. The results are the basis to develop sensor applications, which are based on analyte/molecule interactions and effects on doping. 相似文献
130.
Xinmin You Michael Maschek Niels Harmen H. van Dijk Ekkes Brück 《Entropy (Basel, Switzerland)》2022,24(1)
The phase diagram of the magnetocaloric MnxFe2−xP1−ySiy quaternary compounds was established by characterising the structure, thermal and magnetic properties in a wide range of compositions (for a Mn fraction of 0.3 ≤ x < 2.0 and a Si fraction of 0.33 ≤ y ≤ 0.60). The highest ferromagnetic transition temperature (Mn0.3Fe1.7P0.6Si0.4, TC = 470 K) is found for low Mn and high Si contents, while the lowest is found for low Fe and Si contents (Mn1.7Fe0.3P0.6Si0.4, TC = 65 K) in the MnxFe2−xP1−ySiy phase diagram. The largest hysteresis (91 K) was observed for a metal ratio close to Fe:Mn = 1:1 (corresponding to x = 0.9, y = 0.33). Both Mn-rich with high Si and Fe-rich samples with low Si concentration were found to show low hysteresis (≤2 K). These compositions with a low hysteresis form promising candidate materials for thermomagnetic applications. 相似文献