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991.
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Emanuel Lörtscher Dr. Mark Elbing Dr. Meinrad Tschudy Carsten von Hänisch Dr. Heiko B. Weber Prof. Dr. Marcel Mayor Prof. Dr. Heike Riel Dr. 《Chemphyschem》2008,9(15):2252-2258
A series of oligophenylene rods of increasing lengths is synthesized to investigate the charge‐transport mechanisms. Methyl groups are attached to the phenyl rings to weaken the electronic overlap of the π‐subsystems along the molecular backbones. Out‐of‐plane rotation of the phenyl rings is confirmed in the solid state by means of X‐ray analysis and in solution by using UV/Vis spectroscopy. The influence of the reduced π‐conjugation on the resonant charge transport is studied at the single‐molecule level by using the mechanically controllable break‐junction technique. Experiments are performed under ultra‐high‐vacuum conditions at low temperature (50 K). A linear increase of the conductance gap with increasing number of phenyl rings (from 260 meV for one ring to 580 meV for four rings) is revealed. In addition, the absolute conductance of the first resonant peaks does not depend on the length of the molecular wire. Resonant transport through the first molecular orbital is found to be dominated by charge‐carrier injection into the molecule, rather than by the intrinsic resistance of the molecular wire length. 相似文献
995.
Lorna Dougan Dr. Ainavarapu Sri Rama Koti Dr. Georgi Genchev Hui Lu Prof. Julio M. Fernandez Prof. 《Chemphyschem》2008,9(18):2836-2847
We present an array of force spectroscopy experiments that aim to identify the role of solvent hydrogen bonds in protein folding and chemical reactions at the single‐molecule level. In our experiments we control the strength of hydrogen bonds in the solvent environment by substituting water (H2O) with deuterium oxide (D2O). Using a combination of force protocols, we demonstrate that protein unfolding, protein collapse, protein folding and a chemical reaction are affected in different ways by substituting H2O with D2O. We find that D2O molecules form an integral part of the unfolding transition structure of the immunoglobulin module of human cardiac titin, I27. Strikingly, we find that D2O is a worse solvent than H2O for the protein I27, in direct contrast with the behaviour of simple hydrocarbons. We measure the effect of substituting H2O with D2O on the force dependent rate of reduction of a disulphide bond engineered within a single protein. Altogether, these experiments provide new information on the nature of the underlying interactions in protein folding and chemical reactions and demonstrate the power of single‐molecule techniques to identify the changes induced by a small change in hydrogen bond strength. 相似文献
996.
Sven Froitzheim Dr. Jannik Junge Christopher Barnehl Dr. Tobias A. Engesser Dr. Jan Krahmer Prof. Dr. Christian Näther Prof. Dr. Felix Tuczek 《欧洲无机化学杂志》2023,26(33):e202300280
Series of linear tridentate PNPhPR-ligands (R=Me, Et, Pln, Ph, Cyp, iPr, Cy, tBu) and molybdenum tricarbonyl complexes [Mo(CO)3PNPhPR] (R=Ph, Et, Cyp, iPr, Cy,) were synthesized and characterized using NMR-, IR-, and Raman spectroscopy as well as X-ray crystallography. The influence of the different phosphine donor groups of the PNPhPR ligands on the bonding and activation of CO ligands is investigated. Importantly, all complexes are found to adopt a fac geometry, both in solution and in the solid state. This is in contrast to analogous complexes supported by PNHP ligands. DFT calculations reveal that the phenyl ring at the central amine function is the cause of the preferred geometry, hindering isomerization to a mer geometry. 相似文献
997.
In this article, we investigate the entanglement degrees of angular momenta of atoms and molecules. We demonstrate theoretically and numerically the guidelines, how to prepare maximally entangled states and how the entanglement of the angular momenta changes by changing the quantum numbers of atoms and molecules. We show that the entanglement degree reduces to the Clebsch–Gordan coefficients frequently encountered in angular momentum theory. The maximally entangled states found in this manner are useful for quantum computers and quantum information science. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
998.
合成了以酯键和醚键相连的苯和联苯作为刚棒B嵌段,以聚合度为7,12和17的聚环氧乙烷为A嵌段及辛基或十六烷基为C嵌段的ABC型三嵌段线团-刚棒-线团分子.通过核磁共振氢谱和基质辅助激光解吸电离时间飞行质谱(MALDI-TOF MS)对其结构进行了表征,利用偏光显微镜(POM)、示差扫描量热法(DSC)和小角X射线散射实验(SAXS)对其本体状态下的自组装行为进行了研究.结果表明,聚环氧乙烷聚合度为7、烷基链分别为辛基和十六烷基的化合物1a和2a在固相和液晶态分别自组装成倾斜柱状结构和矩形柱状结构,而具有长聚环氧乙烷链的化合物2b、2c和1c在固相都自组装成倾斜柱状结构.发现聚环氧乙烷链和烷基链的长度显著地影响线团-刚棒-线团分子体系的自组装行为.通过改变线团-刚棒-线团分子体系中柔性链长度的策略,可以精确地调控刚柔三嵌段共聚物的聚集体结构. 相似文献
999.
1000.
Yaju Zhao Guoqing Deng Xiaohui Liu Liang Sun Hui Li Quan Cheng Kai Xi Danke Xu 《Analytica chimica acta》2016
This paper reports a facile synthesis of molybdenum disulfide nanosheets/silver nanoparticles (MoS2/Ag) hybrid and its use as an effective matrix in negative ion matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The nanohybrid exerts a strong synergistic effect, leading to high performance detection of small molecule analytes including amino acids, peptides, fatty acids and drugs. The enhancement of laser desorption/ionization (LDI) efficiency is largely attributed to the high surface roughness and large surface area for analyte adsorption, better dispersibility, increased thermal conductivity and enhanced UV energy absorption as compared to pure MoS2. Moreover, both Ag nanoparticles and the edge of the MoS2 layers function as deprotonation sites for proton capture, facilitating the charging process in negative ion mode and promoting formation of negative ions. As a result, the MoS2/Ag nanohybrid proves to be a highly attractive matrix in MALDI-TOF MS, with desired features such as high desorption/ionization efficiency, low fragmentation interference, high salt tolerance, and no sweet-spots for mass signal. These characteristic properties allowed for simultaneous analysis of eight different drugs and quantification of acetylsalicylic acid in the spiked human serum. This work demonstrates for the first time the fabrication and application of a novel MoS2/Ag hybrid, and provides a new platform for use in the rapid and high throughput analysis of small molecules by mass spectrometry. 相似文献