全文获取类型
收费全文 | 2971篇 |
免费 | 267篇 |
国内免费 | 14篇 |
专业分类
化学 | 2212篇 |
晶体学 | 14篇 |
力学 | 63篇 |
数学 | 420篇 |
物理学 | 543篇 |
出版年
2023年 | 53篇 |
2022年 | 60篇 |
2021年 | 119篇 |
2020年 | 172篇 |
2019年 | 186篇 |
2018年 | 83篇 |
2017年 | 69篇 |
2016年 | 201篇 |
2015年 | 151篇 |
2014年 | 167篇 |
2013年 | 203篇 |
2012年 | 277篇 |
2011年 | 270篇 |
2010年 | 159篇 |
2009年 | 130篇 |
2008年 | 193篇 |
2007年 | 163篇 |
2006年 | 150篇 |
2005年 | 105篇 |
2004年 | 67篇 |
2003年 | 36篇 |
2002年 | 31篇 |
2001年 | 25篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 15篇 |
1997年 | 5篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1932年 | 2篇 |
1916年 | 1篇 |
排序方式: 共有3252条查询结果,搜索用时 15 毫秒
991.
Yuen JD Kumar R Seifter J Valouch S Zakhidov D Moses D Lemmer U Heeger AJ Wudl F 《Journal of the American Chemical Society》2011,133(49):19602-19605
We show that polybis(thienyl)thienodia-thiazolethiophene (PDDTT), a high-performance semiconducting polymer for photodetectors and field-effect transistors, has strong performance dependence on annealing temperature. An unprecedented increase of 3 orders of magnitude is observed in both transistor and photoconductive properties. XRD and AFM evidence points to increased ordering in PDDTT films with annealing. This correlation highlights the importance that order has in determining performance in PDDTT and has possible implications in the design of polymers. 相似文献
992.
Das A Gieb K Krupskaya Y Demeshko S Dechert S Klingeler R Kataev V Büchner B Müller P Meyer F 《Journal of the American Chemical Society》2011,133(10):3433-3443
First members of a new family of heterometallic Mn/Ni complexes [Mn(2)Ni(3)X(2)L(4)(LH)(2)(H(2)O)(2)] (X = Cl: 1; X = Br: 2) with the new ligand 2-{3-(2-hydroxyphenyl)-1H-pyrazol-1-yl}ethanol (H(2)L) have been synthesized, and single crystals obtained from CH(2)Cl(2) solutions have been characterized crystallographically. The molecular structures feature a quasi-linear Mn(III)-Ni(II)-Ni(II)-Ni(II)-Mn(III) core with six-coordinate metal ions, where elongated axes of all the distorted octahedral coordination polyhedra are aligned parallel and are fixed with respect to each other by intramolecular hydrogen bonds. 1 and 2 exhibit quite strong ferromagnetic exchange interactions throughout (J(Mn-Ni) ≈ 40 K (1) or 42 K (2); J(Ni-Ni) ≈ 22 K (1) or 18 K (2)) that lead to an S(tot) = 7 ground state, and a sizable uniaxial magnetoanisotropy with D(mol) values -0.55 K (1) and -0.45 K (2). These values are directly derived also from frequency- and temperature-dependent high-field EPR spectra. Slow relaxation of the magnetization at low temperatures and single-molecule magnet (SMM) behavior are evident from frequency-dependent peaks in the out-of-phase ac susceptibilities and magnetization versus dc field measurements, with significant energy barriers to spin reversal U(eff) = 27 K (1) and 22 K (2). Pronounced quantum tunnelling steps are observed in the hysteresis loops of the temperature- and scan rate-dependent magnetization data, but with the first relaxation step shifted above (1) or below (2) the zero crossing of the magnetic field, despite the very similar molecular structures. The different behavior of 1 and 2 is interpreted in terms of antiferromagnetic (1) or ferromagnetic (2) intermolecular interactions, which are discussed in view of the subtle differences of intermolecular contacts within the crystal lattice. 相似文献
993.
Peter SC Chondroudi M Malliakas CD Balasubramanian M Kanatzidis MG 《Journal of the American Chemical Society》2011,133(35):13840-13843
The family of materials RE(4)TGe(8) (RE = Yb, Gd; T = transition metal) exhibits directional zero thermal expansion (ZTE) via a process that is associated with the linking of planar square nets in the third dimension. The Ge square nets in these compounds exhibit commensurate long-range modulations similar to those observed in charge-density-wave compounds. The ZTE is manifested in the plane of the square nets from 10 to 300 K with negligible volume expansion below ~160 K. The specific atomic arrangement in RE(4)TGe(8) enables a Poisson-like mechanism that allows the structure to contract along one direction as it expands only slightly in the perpendicular direction. 相似文献
994.
Arslan HK Shekhah O Wieland DC Paulus M Sternemann C Schroer MA Tiemeyer S Tolan M Fischer RA Wöll C 《Journal of the American Chemical Society》2011,133(21):8158-8161
We report the synthesis of layered [Zn(2)(bdc)(2)(H(2)O)(2)] and [Cu(2)(bdc)(2)(H(2)O)(2)] (bdc = benzdicarboxylate) metal-organic frameworks (MOF) carried out using the liquid-phase epitaxy approach employing self-assembled monolayer (SAM) modified Au-substrates. We obtain Cu and Zn MOF-2 structures, which have not yet been obtained using conventional, solvothermal synthesis methods. The 2D Cu(2+) dimer paddle wheel planes characteristic for the MOF are found to be strictly planar, with the planes oriented perpendicular to the substrate. Intercalation of an organic dye, DXP, leads to a reversible tilting of the planes, demonstrating the huge potential of these surface-anchored MOFs for the intercalation of large, planar molecules. 相似文献
995.
Christoph Diehl Klaus Blaum Martin H?cker Jochen Ketter David B. Pinegar Sebastian Streubel Robert S. Van Dyck Jr. 《Hyperfine Interactions》2011,199(1-3):291-300
The precise determination of the 3He/3H mass ratio, and hence the tritium ??-decay endpoint energy E 0, is of relevance for the measurement of the electron anti-neutrino mass performed by the Karlsruhe Tritium Neutrino experiment (KATRIN). By determining this ratio to an uncertainty of 1 part in 1011, systematic errors of E 0 can be checked in the data analysis of KATRIN. To reach this precision, a Penning Trap Mass Spectrometer was constructed at the University of Washington and has been transferred to the Max Planck Institute for Nuclear Physics in Heidelberg at the end of 2008. Since then it is called MPIK/UW-PTMS. Special design features are the utilization of an external ion source and a double trap configuration. The external Penning ion source efficiently ionizes the helium and tritium gas and can give superior elimination of unwanted ion species compared to the previously utilized in-trap-ionization by electrons from a field-emission point. The design as a double Penning trap allows a faster measurement procedure. This should help to avoid problems resulting from long-term drifts in the experimental conditions. Additionally, the laboratory in Heidelberg was carefully prepared to have very stable environmental conditions. Experimental challenges and the first Heidelberg results with the new spectrometer are presented. 相似文献
996.
Claudius Lenz Jonas Wick Daniel Braga María García‐Altares Gerald Lackner Christian Hertweck Markus Gressler Dirk Hoffmeister 《Angewandte Chemie (International ed. in English)》2020,59(4):1450-1454
Upon injury, psychotropic psilocybin‐producing mushrooms instantly develop an intense blue color, the chemical basis and mode of formation of which has remained elusive. We report two enzymes from Psilocybe cubensis that carry out a two‐step cascade to prepare psilocybin for oxidative oligomerization that leads to blue products. The phosphatase PsiP removes the 4‐O‐phosphate group to yield psilocin, while PsiL oxidizes its 4‐hydroxy group. The PsiL reaction was monitored by in situ 13C NMR spectroscopy, which indicated that oxidative coupling of psilocyl residues occurs primarily via C‐5. MS and IR spectroscopy indicated the formation of a heterogeneous mixture of preferentially psilocyl 3‐ to 13‐mers and suggest multiple oligomerization routes, depending on oxidative power and substrate concentration. The results also imply that phosphate ester of psilocybin serves a reversible protective function. 相似文献
997.
Andreas Meyer Sebastian Dechert Surjendu Dey Claudia Hbartner Marina Bennati 《Angewandte Chemie (International ed. in English)》2020,59(1):373-379
Spectroscopic and biophysical methods for structural determination at atomic resolution are fundamental in studies of biological function. Here we introduce an approach to measure molecular distances in bio‐macromolecules using 19F nuclear spins and nitroxide radicals in combination with high‐frequency (94 GHz/3.4 T) electron–nuclear double resonance (ENDOR). The small size and large gyromagnetic ratio of the 19F label enables to access distances up to about 1.5 nm with an accuracy of 0.1–1 Å. The experiment is not limited by the size of the bio‐macromolecule. Performance is illustrated on synthesized fluorinated model compounds as well as spin‐labelled RNA duplexes. The results demonstrate that our simple but strategic spin‐labelling procedure combined with state‐of‐the‐art spectroscopy accesses a distance range crucial to elucidate active sites of nucleic acids or proteins in the solution state. 相似文献
998.
Luca Laraia Guillaume Garivet Daniel J. Foley Nadine Kaiser Sebastian Müller Sarah Zinken Thomas Pinkert Julian Wilke Dale Corkery Axel Pahl Sonja Sievers Petra Janning Christoph Arenz Yaowen Wu Raphaël Rodriguez Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2020,59(14):5721-5729
Chemical proteomics is widely applied in small‐molecule target identification. However, in general it does not identify non‐protein small‐molecule targets, and thus, alternative methods for target identification are in high demand. We report the discovery of the autophagy inhibitor autoquin and the identification of its molecular mode of action using image‐based morphological profiling in the cell painting assay. A compound‐induced fingerprint representing changes in 579 cellular parameters revealed that autoquin accumulates in lysosomes and inhibits their fusion with autophagosomes. In addition, autoquin sequesters Fe2+ in lysosomes, resulting in an increase of lysosomal reactive oxygen species and ultimately cell death. Such a mechanism of action would have been challenging to unravel by current methods. This work demonstrates the potential of the cell painting assay to deconvolute modes of action of small molecules, warranting wider application in chemical biology. 相似文献
999.
Denis S. Krylov Sebastian Schimmel Vasilii Dubrovin Fupin Liu T. T. Nhung Nguyen Lukas Spree Chia‐Hsiang Chen Georgios Velkos Claudiu Bulbucan Rasmus Westerstrm Micha Studniarek Jan Dreiser Christian Hess Bernd Büchner Stanislav M. Avdoshenko Alexey A. Popov 《Angewandte Chemie (International ed. in English)》2020,59(14):5756-5764
Magnetic hysteresis is demonstrated for monolayers of the single‐molecule magnet (SMM) Dy2ScN@C80 deposited on Au(111), Ag(100), and MgO|Ag(100) surfaces by vacuum sublimation. The topography and electronic structure of Dy2ScN@C80 adsorbed on Au(111) were studied by STM. X‐ray magnetic CD studies show that the Dy2ScN@C80 monolayers exhibit similarly broad magnetic hysteresis independent on the substrate used, but the orientation of the Dy2ScN cluster depends strongly on the surface. DFT calculations show that the extent of the electronic interaction of the fullerene molecules with the surface is increasing dramatically from MgO to Au(111) and Ag(100). However, the charge redistribution at the fullerene‐surface interface is fully absorbed by the carbon cage, leaving the state of the endohedral cluster intact. This Faraday cage effect of the fullerene preserves the magnetic bistability of fullerene‐SMMs on conducting substrates and facilitates their application in molecular spintronics. 相似文献
1000.
Sebastian Pomplun Christopher R. Shugrue Adeline M. Schmitt Carly K. Schissel Charlotte E. Farquhar Bradley L. Pentelute 《Angewandte Chemie (International ed. in English)》2020,59(28):11566-11572
Capture and release of peptides is often a critical operation in the pathway to discovering materials with novel functions. However, the best methods for efficient capture impede facile release. To overcome this challenge, we report linkers based on secondary amino alcohols for the release of peptides after capture. These amino alcohols are based on serine (seramox) or isoserine (isoseramox) and can be incorporated into peptides during solid‐phase peptide synthesis through reductive amination. Both linkers are quantitatively cleaved within minutes under NaIO4 treatment. Cleavage of isoseramox produced a native peptide N‐terminus. This linker also showed broad substrate compatibility; incorporation into a synthetic peptide library resulted in the identification of all sequences by nanoLC‐MS/MS. The linkers are cell compatible; a cell‐penetrating peptide that contained this linker was efficiently captured and identified after uptake into cells. These findings suggest that such secondary amino alcohol based linkers might be suitable tools for peptide‐discovery platforms. 相似文献