全文获取类型
收费全文 | 2101篇 |
免费 | 206篇 |
国内免费 | 4篇 |
专业分类
化学 | 1893篇 |
晶体学 | 16篇 |
力学 | 33篇 |
数学 | 124篇 |
物理学 | 245篇 |
出版年
2023年 | 16篇 |
2022年 | 34篇 |
2021年 | 39篇 |
2020年 | 45篇 |
2019年 | 57篇 |
2018年 | 34篇 |
2017年 | 28篇 |
2016年 | 89篇 |
2015年 | 99篇 |
2014年 | 107篇 |
2013年 | 173篇 |
2012年 | 140篇 |
2011年 | 174篇 |
2010年 | 137篇 |
2009年 | 103篇 |
2008年 | 128篇 |
2007年 | 116篇 |
2006年 | 100篇 |
2005年 | 83篇 |
2004年 | 71篇 |
2003年 | 81篇 |
2002年 | 71篇 |
2001年 | 47篇 |
2000年 | 40篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1958年 | 7篇 |
1957年 | 6篇 |
排序方式: 共有2311条查询结果,搜索用时 15 毫秒
981.
Deconvolution of distinct lithology chemistry through oversampling with the Mars Science Laboratory Alpha Particle X‐Ray Spectrometer
下载免费PDF全文
![点击此处可从《X射线光谱测定》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Scott J. VanBommel Ralf Gellert Jeff A. Berger John L. Campbell Lucy M. Thompson Kenneth S. Edgett Marie J. McBride Michelle E. Minitti Irina Pradler Nicholas I. Boyd 《X射线光谱测定》2016,45(3):155-161
The Alpha Particle X‐Ray Spectrometer (APXS) determines the chemical composition of Martian rocks and soils on‐board both active National Aeronautics and Space Administration (NASA) rovers using X‐ray emission spectroscopy through complementary particle‐induced X‐ray emission (PIXE) and X‐ray fluorescence (XRF) excitation methods. A single APXS spectrum represents the sum of the signals from within the instrument's field of view (FOV). In the past, features smaller than the FOV have been investigated through repeated measurements with stepwise lateral offsets. These lateral offsets allow for empirically extracting, through elemental correlations, distinct compositions of different features. Here, we present a novel analytical method for deconvolving the endmember chemistry of visually distinct components through oversampling and the integrated analysis of the elemental data and supporting images. We discuss specifically the method's application to three targets investigated by the Mars Science Laboratory rover Curiosity during its traverse, as well as the added information that can be gained from this method in the future. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
982.
Richard L. Neitzel Maire S.A. Heikkinen Christopher C. Williams Susan Marie Viet Michael Dellarco 《Applied Acoustics》2016
Knowledge of the auditory and non-auditory effects of noise has increased dramatically over the past decade, but indoor noise exposure measurement methods have not advanced appreciably, despite the introduction of applicable new technologies. This study evaluated various conventional and smart devices for exposure assessment in the National Children’s Study. Three devices were tested: a sound level meter (SLM), a dosimeter, and a smart device with a noise measurement application installed. Instrument performance was evaluated in a series of semi-controlled tests in office environments over 96-h periods, followed by measurements made continuously in two rooms (a child’s bedroom and a most used room) in nine participating homes over a 7-day period with subsequent computation of a range of noise metrics. The SLMs and dosimeters yielded similar A-weighted average noise levels. Levels measured by the smart devices often differed substantially (showing both positive and negative bias, depending on the metric) from those measured via SLM and dosimeter, and demonstrated attenuation in some frequency bands in spectral analysis compared to SLM results. Virtually all measurements exceeded the Environmental Protection Agency’s 45 dBA day–night limit for indoor residential exposures. The measurement protocol developed here can be employed in homes, demonstrates the possibility of measuring long-term noise exposures in homes with technologies beyond traditional SLMs, and highlights potential pitfalls associated with measurements made by smart devices. 相似文献
983.
Dr. Yaroslav Grosu Dr. Mian Li Yun‐Lei Peng Dong Luo Prof. Dan Li Dr. Abdessamad Faik Prof. Jean‐Marie Nedelec Prof. Jean‐Pierre Grolier 《Chemphyschem》2016,17(21):3359-3364
A molecular spring formed by a hydrophobic metal–organic framework Cu2(tebpz) (tebpz=3,3′,5,5′‐tetraethyl‐4,4′‐bipyrazolate) and water is presented. This nanoporous heterogeneous lyophobic system (HLS) has exceptional properties compared to numerous reported systems of such type in terms of stability, efficiency, and operating pressure. Mechanical and thermal energetic characteristics as well as stability of the system are discussed and compared in detail with those of other previously reported HLS. 相似文献
984.
Marie Horká Karel Šlais Pavel Karásek Filip Růžička Jiří Šalplachta Jozef Šesták Vladislav Kahle Michal Roth 《Journal of separation science》2016,39(19):3827-3834
The electro‐osmotic flow, a significant factor in capillary electrophoretic separations, is very sensitive to small changes in structure and surface roughness of the inner surface of fused silica capillary. Besides a number of negative effects, the electro‐osmotic flow can also have a positive effect on the separation. An example could be fused silica capillaries with homogenous surface roughness along their entire separation length as produced by etching with supercritical water. Different strains of methicillin‐resistant and methicillin‐susceptible Staphylococcus aureus were separated on that type of capillaries. In the present study, fused‐silica capillaries with a gradient of surface roughness were prepared and their basic behavior was studied in capillary zone electrophoresis with UV‐visible detection. First the influence of the electro‐osmotic flow on the peak shape of a marker of electro‐osmotic flow, thiourea, has been discussed. An antifungal agent, hydrophobic amphotericin B, and a protein marker, albumin, have been used as model analytes. A significant narrowing of the detected zones of the examined analytes was achieved in supercritical‐water‐treated capillaries as compared to the electrophoretic separation in smooth capillaries. Minimum detectable amounts of 5 ng/mL amphotericin B and 5 μg/mL albumin were reached with this method. 相似文献
985.
Prof. Jesper Bendix Dr. Kensha Marie Clark 《Angewandte Chemie (International ed. in English)》2016,55(8):2748-2752
To survey the noninnocence of bis(arylimino) acenaphthene (BIAN) ligands (L) in complexes with early metals, the homoleptic vanadium complex, [V(L)3] ( 1 ), and its monocation, [V(L)3]PF6 ( 2 ), were synthesized. These complexes were found to have a very rich electronic behavior, whereby 1 displays strong electronic delocalization and 2 can be observed in unprecedented valence tautomeric forms. The oxidation states of the metal and ligand components in these complexes were assigned by using spectroscopic, crystallographic, and magnetic analyses. Complex 1 was identified as [VIV(Lred)(L.)2] (Lred=N,N′‐bis(3,5‐dimethylphenylamido)acenaphthylene; L.=N,N′‐bis(3,5‐dimethylphenylimino)acenaphthenesemiquinonate). Complex 2 was determined to be [VV(Lred)(L.)2]+ at T<150 K and [VIV(L.)3]+ at T>150 K. Cyclic voltammetry experiments reveal six quasi‐reversible processes, thus indicating the potential of this metal–ligand combination in catalysis or materials applications. 相似文献
986.
Dr. Andrei S. Batsanov Prof. Dr. Javier A. Cabeza Dr. Marco G. Crestani Dr. Manuel R. Fructos Dr. Pablo García‐Álvarez Dr. Marie Gille Prof. Zhenyang Lin Prof. Dr. Todd B. Marder 《Angewandte Chemie (International ed. in English)》2016,55(15):4707-4710
Many transition‐metal complexes and some metal‐free compounds are able to bind carbon monoxide, a molecule which has the strongest chemical bond in nature. However, very few of them have been shown to induce the cleavage of its C?O bond and even fewer are those that are able to transform CO into organic reagents with potential in organic synthesis. This work shows that bis(pinacolato)diboron, B2pin2, reacts with ruthenium carbonyl to give metallic complexes containing borylmethylidyne (CBpin) and diborylethyne (pinBC≡CBpin) ligands and also metal‐free perborylated C1 and C2 products, such as C(Bpin)4 and C2(Bpin)6, respectively, which have great potential as building blocks for Suzuki–Miyaura cross‐coupling and other reactions. The use of 13CO‐enriched ruthenium carbonyl has demonstrated that the boron‐bound carbon atoms of all of these reaction products arise from CO ligands. 相似文献
987.
Peter B. Weber Raphael Hellwig Tobias Paintner Dr. Marie Lattelais Mateusz Paszkiewicz Pablo Casado Aguilar Peter S. Deimel Dr. Yuanyuan Guo Dr. Yi‐Qi Zhang Dr. Francesco Allegretti Dr. Anthoula C. Papageorgiou Dr. Joachim Reichert Dr. Svetlana Klyatskaya Prof. Dr. Mario Ruben Prof. Dr. Johannes V. Barth Dr. Marie‐Laure Bocquet Dr. Florian Klappenberger 《Angewandte Chemie (International ed. in English)》2016,55(19):5754-5759
Organocobalt complexes represent a versatile tool in organic synthesis as they are important intermediates in Pauson–Khand, Friedel–Crafts, and Nicholas reactions. Herein, a single‐molecule‐level investigation addressing the formation of an organocobalt complex at a solid–vacuum interface is reported. Deposition of 4,4′‐(ethyne‐1,2‐diyl)dibenzonitrile and Co atoms on the Ag(111) surface followed by annealing resulted in genuine complexes in which single Co atoms laterally coordinated to two carbonitrile groups undergo organometallic bonding with the internal alkyne moiety of adjacent molecules. Alternative complexation scenarios involving fragmentation of the precursor were ruled out by complementary X‐ray photoelectron spectroscopy. According to density functional theory analysis, the complexation with the alkyne moiety follows the Dewar–Chatt–Duncanson model for a two‐electron‐donor ligand where an alkyne‐to‐Co donation occurs together with a strong metal‐to‐alkyne back‐donation. 相似文献
988.
Paulus W Schober H Eibl S Johnson M Berthier T Hernandez O Ceretti M Plazanet M Conder K Lamberti C 《Journal of the American Chemical Society》2008,130(47):16080-16085
SrFeO(2.5) and SrCoO(2.5) are able to intercalate oxygen in a reversible topotactic redox reaction already at room temperature to form the cubic perovskites Sr(Fe,Co)O(3), while CaFeO(2.5) can only be oxidized under extreme conditions. To explain this significant difference in low temperature oxygen mobility, we investigated the homologous SrFeO(2.5) and CaFeO(2.5) by temperature dependent oxygen isotope exchange as well as by inelastic neutron scattering (INS) studies, combined with ab initio (DFT) molecular dynamical calculations. From (18)O/(16)O isotope exchange experiments we proved free oxygen mobility to be realized in SrFeO(x) already below 600 K. We have also evidence that low temperature oxygen mobility relies on the existence of specific, low energy lattice modes, which trigger and amplify oxygen mobility in solids. We interpret the INS data together with the DFT-based molecular dynamical simulation results on SrFeO(2.5) and CaFeO(2.5) in terms of an enhanced, phonon-assisted, low temperature oxygen diffusion for SrFeO(3-x) as a result of the strongly reduced Fe-O-Fe bond strength of the apical oxygen atoms in the FeO(6) octahedra along the stacking axis. This dynamically triggered phenomenon leads to an easy migration of the oxide ions into the open vacancy channels and vice versa. The decisive impact of lattice dynamics, giving rise to structural instabilities in oxygen deficient perovskites, especially with brownmillerite-type structure, is demonstrated, opening new concepts for the design and tailoring of low temperature oxygen ion conductors. 相似文献
989.
Bazin L Gressier M Taberna PL Menu MJ Simon P 《Chemical communications (Cambridge, England)》2008,(40):5004-5006
A method for silica-coating at the nanoscale by electrophoretic deposition is presented here, using raw or grafted silica dispersions. 相似文献
990.