全文获取类型
收费全文 | 635篇 |
免费 | 24篇 |
国内免费 | 12篇 |
专业分类
化学 | 499篇 |
晶体学 | 2篇 |
力学 | 11篇 |
数学 | 91篇 |
物理学 | 68篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 28篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 19篇 |
2012年 | 38篇 |
2011年 | 55篇 |
2010年 | 29篇 |
2009年 | 25篇 |
2008年 | 41篇 |
2007年 | 40篇 |
2006年 | 44篇 |
2005年 | 36篇 |
2004年 | 34篇 |
2003年 | 30篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1990年 | 5篇 |
1981年 | 2篇 |
1967年 | 2篇 |
1917年 | 2篇 |
1915年 | 2篇 |
1904年 | 2篇 |
1903年 | 2篇 |
1901年 | 2篇 |
1896年 | 2篇 |
1886年 | 3篇 |
1884年 | 2篇 |
1880年 | 4篇 |
1879年 | 4篇 |
1878年 | 4篇 |
1877年 | 5篇 |
1876年 | 7篇 |
1874年 | 4篇 |
1865年 | 2篇 |
排序方式: 共有671条查询结果,搜索用时 156 毫秒
91.
Min Tu Helge Reinsch Sabina Rodríguez‐Hermida Rhea Verbeke Timothe Stassin Werner Egger Marcel Dickmann Bjorn Dieu Johan Hofkens Ivo F. J. Vankelecom Norbert Stock Rob Ameloot 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2445-2449
Metal–organic frameworks (MOFs) enable the design of host–guest systems with specific properties. In this work, we show how the confinement of anthracene in a well‐chosen MOF host leads to reversible yellow‐to‐purple photoswitching of the fluorescence emission. This behavior has not been observed before for anthracene, either in pure form or adsorbed in other porous hosts. The photoresponse of the host–guest system is caused by the photodimerization of anthracene, which is greatly facilitated by the pore geometry, connectivity, and volume as well as the structural flexibility of the MOF host. The photoswitching behavior was used to fabricate photopatternable and erasable surfaces that, in combination with data encryption and decryption, hold promise in product authentication and secure communication applications. 相似文献
92.
Niels J. Hauwert Tamara A. M. Mocking Daniel DaCostaPereira Ken Lion Yara Huppelschoten Henry F. Vischer Iwan J. P. DeEsch Maikel Wijtmans Rob Leurs 《Angewandte Chemie (International ed. in English)》2019,58(14):4531-4535
Spatiotemporal control over biochemical signaling processes involving G protein‐coupled receptors (GPCRs) is highly desired for dissecting their complex intracellular signaling. We developed sixteen photoswitchable ligands for the human histamine H3 receptor (hH3R). Upon illumination, key compound 65 decreases its affinity for the hH3R by 8.5‐fold and its potency in hH3R‐mediated Gi protein activation by over 20‐fold, with the trans and cis isomer both acting as full agonist. In real‐time two‐electrode voltage clamp experiments in Xenopus oocytes, 65 shows rapid light‐induced modulation of hH3R activity. Ligand 65 shows good binding selectivity amongst the histamine receptor subfamily and has good photolytic stability. In all, 65 (VUF15000) is the first photoswitchable GPCR agonist confirmed to be modulated through its affinity and potency upon photoswitching while maintaining its intrinsic activity, rendering it a new chemical biology tool for spatiotemporal control of GPCR activation. 相似文献
93.
Dongre C Dekker R Hoekstra HJ Pollnau M Martinez-Vazquez R Osellame R Cerullo G Ramponi R van Weeghel R Besselink GA van den Vlekkert HH 《Optics letters》2008,33(21):2503-2505
Using femtosecond laser writing, optical waveguides were monolithically integrated into a commercial microfluidic lab-on-a-chip device, with the waveguides intersecting a microfluidic channel. Continuous-wave laser excitation through these optical waveguides confines the excitation window to a width of 12 microm, enabling high-resolution monitoring of the passage of different types of fluorescent analytes when migrating and being separated in the microfluidic channel by microchip capillary electrophoresis. Furthermore, we demonstrate on-chip-integrated waveguide excitation and detection of a biologically relevant species, fluorescently labeled DNA molecules, during microchip capillary electrophoresis. Well-controlled plug formation as required for on-chip integrated capillary electrophoresis separation of DNA molecules, and the combination of waveguide excitation and a low limit of detection, will enable monitoring of extremely small quantities with high spatial resolution. 相似文献
94.
Theo Scholtes Stefan Woetzel Rob IJsselsteijn Volkmar Schultze Hans-Georg Meyer 《Applied physics. B, Lasers and optics》2014,117(1):211-218
The intrinsic relaxation rates of the vector magnetization of cesium vapor enclosed in microfabricated atomic magnetometer cells are investigated. Two methods—the optically detected magnetic resonance and the ground-state Hanle effect—are used to carry out automated measurements in dependence on cell temperature and nitrogen buffer gas pressure. The experimental results are compared with expected contributions of the different relaxation processes and in this way allow the discrimination between them to help further optimization of cell design. The methods are compared in terms of basic features, data quality, and practical applicability. 相似文献
95.
1,6-Diazacyclododecane-7,12-dione (C10H18N2O2),M
r
=198.27, monoclinic, one molecule in the asymmetric unit,P21/c;a=9.802(4),b=12.966(6),c=9.20(1) Å,V=1083(1) Å3,Z=4,D
x
=1.215(2) Mg·m–3, (CuK)=1.54184 Å,=6.5 cm–1,F(000)=432,R=0.062 for all 866 unique observed reflection data. The molecules form hydrogen bonded stacks with two hydrogen bonds between each pair of succeeding molecules. The stacks consist of molecules with two alternating orientations, as in A-B-A-B. No strong intermolecular contacts exist between adjacent stacks, this results in a partial two-fold positional disorder of the stacks in the direction of thea-axis: two adjacent stacks can slide over half a unit cell along thea-axis without severely affecting the packing. This disorder results in very broad reflectionsh2n, which could only be discerned on a rotation photograph. The 12-membered ring which forms the basis of the structure has a pseudo two-fold axis through the bonds C(8)-C(10) and C(9)-C(11). 相似文献
96.
Sadar MD Williams DE Mawji NR Patrick BO Wikanta T Chasanah E Irianto HE Soest RV Andersen RJ 《Organic letters》2008,10(21):4947-4950
The new chlorinated peptides sintokamides A to E (1-5) have been isolated from specimens of the marine sponge Dysidea sp. collected in Indonesia. Their structures were elucidated by a combination of spectroscopic and single-crystal X-ray diffraction analyses. Sintokamide A (1) is an inhibitor of N-terminus transactivation of the androgen receptor in prostate cancer cells. 相似文献
97.
Jongejan A Lim HD Smits RA de Esch IJ Haaksma E Leurs R 《Journal of chemical information and modeling》2008,48(7):1455-1463
A three-dimensional homology model of the human histamine H 4 receptor was developed to investigate the binding mode of a series of structurally diverse H 4-agonists, i.e. histamine, clozapine, and the recently described selective, nonimidazole agonist VUF 8430. Mutagenesis studies and docking of these ligands in a rhodopsin-based homology model revealed two essential points of interactions in the binding pocket, i.e. Asp3.32 and Glu5.46 (Ballesteros-Weinstein numbering system). It is postulated that Asp3.32 interacts in its anionic state, whereas Glu5.46 interacts in its neutral form. The hypothesis was tested with the point mutations D3.32N and E5.46Q. For the D3.32N no binding affinity toward any of the ligands could be detected. This is in sharp contrast to the E5.46Q mutant, which discriminates between various ligands. The affinity of histamine-like ligands was decreased approximately a 1000-fold, whereas the affinity of all other ligands remained virtually unchanged. The proposed model for agonist binding as well as ab initio calculations for histamine and VUF 8430 explain the observed differences in binding to the H 4R mutants. These studies provide a molecular understanding for the action of a variety of H 4 receptor-ligands. The resulting H 4 receptor model will be the basis for the development of new H 4 receptor-ligands. 相似文献
98.
Fluorescent sensor array in a microfluidic chip 总被引:1,自引:0,他引:1
Basabe-Desmonts L Benito-López F Gardeniers HJ Duwel R van den Berg A Reinhoudt DN Crego-Calama M 《Analytical and bioanalytical chemistry》2008,390(1):307-315
Miniaturization and automation are highly important issues for the development of high-throughput processes. The area of micro total analysis systems (muTAS) is growing rapidly and the design of new schemes which are suitable for miniaturized analytical devices is of great importance. In this paper we report the immobilization of self-assembled monolayers (SAMs) with metal ion sensing properties, on the walls of glass microchannels. The parallel combinatorial synthesis of sensing SAMs in individually addressable microchannels towards the generation of optical sensor arrays and sensing chips has been developed. [figure: see text] The advantages of microfluidic devices, surface chemistry, parallel synthesis, and combinatorial approaches have been merged to integrate a fluorescent chemical sensor array in a microfluidic chip. Specifically, five different fluorescent self-assembled monolayers have been created on the internal walls of glass microchannels confined in a microfluidic chip. 相似文献
99.
Factors that determine the chirality of supramolecular helical tapes formed by a backbone-modified amylin(20-29) depsipeptide and inverso-depsipeptide, were studied by Fourier transform infrared spectroscopy, circular dichroism and transmission electron microscopy. Although β-sheet propensity was absent in both peptides, it was found that the l-depsipeptide formed left-handed and the enantiomeric d-depsipeptide right-handed helical tapes. Moreover, the backbone-modified depsipeptides, showed a certain degree of cross-recognition between both enantiomers, which might have implications in designing amyloid formation inhibitors. 相似文献
100.
A high-yielding and concise preparation of N(G)-substituted L-arginine analogues, suitably protected for use in solid phase peptide synthesis, is reported. The synthesis of each analogue employed an activated thiourea intermediate that was converted under mild conditions to the desired L-arginine analogue (10 examples, each in near quantitative yield). Subsequent allyl group removal provided each analogue in a form ideally suited for use in solid phase peptide synthesis. 相似文献