全文获取类型
收费全文 | 1821篇 |
免费 | 44篇 |
国内免费 | 8篇 |
专业分类
化学 | 983篇 |
晶体学 | 5篇 |
力学 | 96篇 |
综合类 | 2篇 |
数学 | 442篇 |
物理学 | 345篇 |
出版年
2022年 | 24篇 |
2021年 | 40篇 |
2020年 | 29篇 |
2019年 | 18篇 |
2018年 | 29篇 |
2017年 | 18篇 |
2016年 | 44篇 |
2015年 | 43篇 |
2014年 | 53篇 |
2013年 | 82篇 |
2012年 | 87篇 |
2011年 | 100篇 |
2010年 | 80篇 |
2009年 | 67篇 |
2008年 | 75篇 |
2007年 | 101篇 |
2006年 | 97篇 |
2005年 | 71篇 |
2004年 | 58篇 |
2003年 | 57篇 |
2002年 | 52篇 |
2001年 | 35篇 |
2000年 | 30篇 |
1999年 | 19篇 |
1998年 | 28篇 |
1997年 | 23篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 22篇 |
1992年 | 19篇 |
1991年 | 11篇 |
1990年 | 13篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 12篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1975年 | 15篇 |
1974年 | 13篇 |
1973年 | 10篇 |
1970年 | 10篇 |
1969年 | 13篇 |
1916年 | 11篇 |
排序方式: 共有1873条查询结果,搜索用时 31 毫秒
81.
An updated version of the computational package SIMPRE that uses the standard conventions for Stevens crystal field parameters
下载免费PDF全文
![点击此处可从《Journal of computational chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
José J. Baldoví Juan M. Clemente‐Juan Eugenio Coronado Alejandro Gaita‐Ariño Andrew Palii 《Journal of computational chemistry》2014,35(26):1930-1934
The crystal field approach used by SIMPRE is analyzed, verifying the exactness of the results concerning energy levels and magnetic properties calculated by the package. To coincide with the prevailing conventions, we reformulate the presentation of the crystal field parameters, so that the results are now, also from a formal point of view, strictly correct. New calculations are presented to test the influence of neglecting the excited J states, a common but critical approximation employed by SIMPRE. For that, we examine the case of Er(trensal) complex (H3trensal = 2,2′,2″‐tris(salicylideneimino)triethylamine) where the influence of this approximation is found to be minimal. A patched version of the code, SIMPRE 1.1, and an updated version of the user manual are now available. Finally, we comment on “Software package SIMPRE – revisited,” which apparently revisits a software package without inspecting or using the code. © 2014 Wiley Periodicals, Inc. 相似文献
82.
Elisa Michelini Luca Cevenini Maria Maddalena Calabretta Donato Calabria Aldo Roda 《Analytical and bioanalytical chemistry》2014,406(23):5531-5539
Bioluminescence-based analytical tools are suitable for high-throughput and high-content screening assays, finding widespread application in several fields related to the drug discovery process. Cell-based bioluminescence assays, because of their peculiar advantages of predictability, possibility of automation, multiplexing, and miniaturization, seem the most appealing tool for the high demands of the early stages of drug screening. Reporter gene technology and the bioluminescence resonance energy transfer principle are widely used, and receptor binding studies of new agonists/antagonists for a variety of human receptors expressed in different cell lines can be performed. Moreover, bioluminescence can be used for in vitro and in vivo real-time monitoring of pathophysiological processes within living cells and small animals. New luciferases and substrates have recently arrived on the market, further expanding the spectrum of applications. A new generation of probes are also emerging that promise to revolutionize the preclinical imaging market. This formidable toolbox is demonstrated to facilitate the implementation of the three Rs principle in the early drug discovery process, in compliance with ethical and responsible research to reduce cost and improve the reliability and predictability of results. 相似文献
83.
Dr. Manuela Leticia Kim Dr. Deicy Barrera Dr. Mutsumi Kimura Prof. Dr. Juan P. Hinestroza Prof. Dr. Karim Sapag Dr. Eugenio Hernán Otal 《化学:亚洲杂志》2021,16(9):1086-1091
We report on a detailed textural analysis of mechanochemically synthesized MOF-199 including N2 adsorption-desorption and CO2 adsorption isotherms data at 77 K and 273 K (up to atmospheric pressure), respectively, and CH4 adsorption data at 298 K (up to 35 bar). We used the isotherm adsorption data to determine the micropore volume of the MOF-199 structures, to establish their methane uptake capacity and to understand how these properties depended on the Ethanol/BTC ratio used during the synthesis. The maximum methane uptake capacity for our specimens was recorded at 130 v/v at 35 bars. These results open an avenue for a better understanding of alternative manufacturing processes of MOF structures for gas storage applications. 相似文献
84.
Imaging the Magnetic Reversal of Isolated and Organized Molecular‐Based Nanoparticles using Magnetic Force Microscopy
下载免费PDF全文
![点击此处可从《Particle & Particle Systems Characterization》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Elena Pinilla‐Cienfuegos Samuel Mañas‐Valero Josep Canet‐Ferrer Laure Catala Talal Mallah Alicia Forment‐Aliaga Eugenio Coronado 《Particle & Particle Systems Characterization》2015,32(6):693-700
In the race towards miniaturization in nanoelectronics, magnetic nanoparticles (MNPs) have emerged as potential candidates for their integration in ultrahigh‐density recording media. Molecular‐based materials open the possibility to design new tailor‐made MNPs with variable composition and sizes, which benefit from the intrinsic properties of these materials. Before their implementation in real devices is reached, a precise organization on surfaces and a reliable characterization and manipulation of their individual magnetic behavior are required. In this paper, it is demonstrated how molecular‐based MNPs are accurately organized on surfaces and how the magnetic properties of the individual MNPs are detected and tuned by means of low‐temperature magnetic force microscopy (LT‐MFM) with variable magnetic field. The magnetization reversal on isolated and organized MNPs is investigated; in addition, the temperature dependence of their magnetic response is evaluated. 相似文献
85.
Cover Picture: Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets (Chem. Eur. J. 6/2014)
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)
86.
Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets
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. Miguel Clemente‐León Prof. Eugenio Coronado Prof. Carlos J. Gómez‐García Dr. Maurici López‐Jordà Dr. Agustín Camón Ana Repollés Dr. Fernando Luis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1669-1676
The insertion of the single‐molecule magnet (SMM) [MnIII(salen)(H2O)]22+ (salen2?=N,N′‐ethylenebis‐(salicylideneiminate)) into a ferromagnetic bimetallic oxalate network affords the hybrid compound [MnIII(salen)(H2O)]2[MnIICrIII(ox)3]2 ? (CH3OH) ? (CH3CN)2 ( 1 ). This cationic Mn2 cluster templates the growth of crystals formed by an unusual achiral 3D oxalate network. The magnetic properties of this hybrid magnet are compared with those of the analogous compounds [MnIII(salen)(H2O)]2[ZnIICrIII(ox)3]2 ? (CH3OH) ? (CH3CN)2 ( 2 ) and [InIII(sal2‐trien)][MnIICrIII(ox)3] ? (H2O)0.25 ? (CH3OH)0.25 ? (CH3CN)0.25 ( 3 ), which are used as reference compounds. In 2 it has been shown that the magnetic isolation of the Mn2 clusters provided by their insertion into a paramagnetic oxalate network of CrIII affords a SMM behavior, albeit with blocking temperatures well below 500 mK even for frequencies as high as 160 kHz. In 3 the onset of ferromagnetism in the bimetallic MnIICrIII network is observed at Tc=5 K. Finally, in the hybrid compound 1 the interaction between the two magnetic networks leads to the antiparallel arrangement of their respective magnetizations, that is, to a ferrimagnetic phase. This coupling induces also important changes on the magnetic properties of 1 with respect to those of the reference compounds 2 and 3 . In particular, compound 1 shows a large magnetization hysteresis below 1 K, which is in sharp contrast with the near‐reversible magnetizations that the SMMs and the oxalate ferromagnetic lattice show under the same conditions. 相似文献
87.
Gonzalo Abellán Jose A. Carrasco Eugenio Coronado Helena Prima-García 《Journal of Sol-Gel Science and Technology》2014,70(2):292-299
Pure and highly crystalline FeNi3 alloy nanoparticles (NPs) were synthesized via sol–gel route with benzyl alcohol, using hydrazine as a reduction reagent without the usage of additional surfactant molecules nor further annealing processes. The structural studies revealed that the particle size is of ca. 200 nm, whose structure consisted on aggregation of small crystallites of about 13 nm. The magnetic properties of the as-synthesized NPs were similar to the bulk with a saturation magnetization of 95 emu g?1. Moreover, the coercive field was ca. 50 G, exhibiting a M r /M s ratio of 0.03, indicative of soft ferromagnetism. The electrical transport in the temperature range 2–300 K exhibits a typical ferromagnetic metallic behaviour. Finally, similar FeNi3 NPs were synthesized in EtOH/H2O mixtures in the presence of sodium dodecyl sulphate molecules as surfactant for comparative purposes, exhibiting a typical half hard magnetic behaviour, highlighting the interest of the reported benzylic route. 相似文献
88.
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
89.
Viktor Pajer Ferenc Rárosi Lajos Kolozsvári Béla Hopp Antal Nógrádi 《Photochemistry and photobiology》2020,96(4):826-833
The purpose of the present study was to determine the age dependence of the ultraviolet (UV) absorption of the different parts of the human crystalline lens. Cryostat sections of human cadaveric lenses (60 μm) were cut. The UV absorbance of nine samples, derived from different parts of the lens, was determined using a Shimadzu scanning spectrophotometer. The absorbance of the anterior and posterior lens capsules was measured separately. The absorption coefficients were calculated from the measured absorbance and values taken at 280 as well as at 360 nm were compared statistically. ANCOVA analysis of the values taken at 280 and at 360 nm wavelengths shows that correlation between the absorption coefficients and age can be found only in the case of the posterior layers. These results suggest a differential age-dependent increase of the UV absorption of the posterior layers compared to the anterior ones and can be related to the differential protein expression in the anterior and posterior parts. Posterior crystalline lens capsules have higher absorption coefficients than the anterior ones regardless of age. 相似文献
90.
Dr. Luka Ðorđević Cataldo Valentini Dr. Nicola Demitri Cécile Mézière Magali Allain Prof. Dr. Marc Sallé Dr. Andrea Folli Prof. Dr. Damien Murphy Samuel Mañas-Valero Prof. Dr. Eugenio Coronado Prof. Dr. Davide Bonifazi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):4135-4143
Herein we report an efficient synthesis to prepare O-doped nanographenes derived from the π-extension of pyrene. The derivatives are highly fluorescent and feature low oxidation potentials. Using electrooxidation, crystals of cationic mixed-valence (MV) complexes were grown in which the organic salts organize into face-to-face π-stacks, a favorable solid-state arrangement for organic electronics. Variable-temperature electron paramagnetic resonance (EPR) measurements and relaxation studies suggest a strong electron delocalization along the longitudinal axis of the columnar π-stacking architectures. Electric measurements of single crystals of the MV salts show a semiconducting behavior with a remarkably high conductivity at room temperature. These findings support the notion that π-extension of heteroatom-doped polycyclic aromatic hydrocarbons is an attractive approach to fabricate nanographenes with a broad spectrum of semiconducting properties and high charge mobilities. 相似文献