全文获取类型
收费全文 | 5033篇 |
免费 | 207篇 |
国内免费 | 33篇 |
专业分类
化学 | 3597篇 |
晶体学 | 17篇 |
力学 | 123篇 |
数学 | 865篇 |
物理学 | 671篇 |
出版年
2023年 | 41篇 |
2022年 | 52篇 |
2021年 | 91篇 |
2020年 | 116篇 |
2019年 | 110篇 |
2018年 | 68篇 |
2017年 | 55篇 |
2016年 | 154篇 |
2015年 | 139篇 |
2014年 | 177篇 |
2013年 | 277篇 |
2012年 | 312篇 |
2011年 | 358篇 |
2010年 | 252篇 |
2009年 | 199篇 |
2008年 | 313篇 |
2007年 | 314篇 |
2006年 | 301篇 |
2005年 | 300篇 |
2004年 | 236篇 |
2003年 | 207篇 |
2002年 | 212篇 |
2001年 | 82篇 |
2000年 | 69篇 |
1999年 | 70篇 |
1998年 | 59篇 |
1997年 | 64篇 |
1996年 | 70篇 |
1995年 | 44篇 |
1994年 | 38篇 |
1993年 | 23篇 |
1992年 | 19篇 |
1991年 | 31篇 |
1990年 | 19篇 |
1989年 | 30篇 |
1988年 | 18篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1982年 | 33篇 |
1981年 | 23篇 |
1980年 | 25篇 |
1979年 | 18篇 |
1978年 | 33篇 |
1977年 | 20篇 |
1976年 | 15篇 |
1975年 | 12篇 |
1974年 | 18篇 |
1973年 | 10篇 |
排序方式: 共有5273条查询结果,搜索用时 15 毫秒
991.
992.
993.
The investigation into the luminescence properties of a lanthanide-binding peptide, derived from the Ca-binding loop of the parvalbumin, and modified by incorporating a 1,8-naphthalimide (Naph) chromophore at the N-terminus is described. Here, the Naph is used as a sensitising antenna, which can be excited at lower energy than classical aromatic amino acids, such as tryptophan (the dodecapeptide of which was also synthesised and studied herein). The syntheses of the Naph antenna, its solid phase incorporation into the dodecapeptide, and the NMR investigation into the formation of the corresponding lanthanide complexes in solution is presented. We also show that this Naph antenna can be successfully employed to sensitize the excited states of both europium and terbium ions, the results of which was used to determined the stability constants of their formation complexes, and we demonstrated that our peptide 'loop' can selectively bind these lanthanide ions over Ca(II). 相似文献
994.
Andreas Helmstedt Marc D. Sacher Aaron Gryzia Alexander Harder Armin Brechling Norbert Müller Ulrich Heinzmann Veronika Hoeke Erich Krickemeyer Thorsten Glaser Samuel Bouvron Mikhail Fonin 《Journal of Electron Spectroscopy and Related Phenomena》2012,184(11-12):583-588
X-ray absorption spectroscopy studies of the [MnIII6CrIII]3+ single-molecule magnet deposited as a microcrystalline layer on gold substrates are presented. The oxidation state of the manganese centers changes from MnIII to MnII due to irradiation with soft X-rays. The influence of the charge-neutralizing anions on the stability of [MnIII6CrIII]3+ against soft X-ray exposure is investigated for the different anions tetraphenylborate (BPh4?), lactate (C3H5O3?) and perchlorate (ClO4?). The exposure dependence of the radiation-induced reduction process is compared for [MnIII6CrIII]3+ with the three different anions. 相似文献
995.
Advances in nanotechnology have indicated that the passivant and the inorganic surface play a pivotal role in controlling the structure/function relationship of materials. Beyond standard materials-based methods, bioligands have recently demonstrated the production of unique nanomaterial morphologies for application under ambient conditions for multiple activities, such as catalysis and biosensing. We have recently demonstrated that a biotemplate technique could be employed to produce spherical and linear Pd nanostructures in water using a self-assembling peptide framework. The materials possessed high catalytic reactivity that was controlled by the three-dimensional structure of the composite materials. To investigate the effect of the peptide template on the reactivity of Pd nanostructures, an in depth analysis of the catalytic activity of Pd nanostructures fabricated via truncated templates is presented. The new templates were designed from portions of the original framework, which demonstrated unique synthetic and functionality control. Two different reactions, Stille C-C coupling and 4-nitrophenol reduction, were employed to ascertain the effect of template structure on the reactivity of synthesized Pd nanomaterials via changes in reagent diffusion through the bioscaffold. The results indicate that the peptide framework plays an important role and could be used to tune and optimize the functionality of the final composite materials for the target application. 相似文献
996.
Rosenthal D Widmer R Wagner R Gille P Armbrüster M Grin Y Schlögl R Gröning O 《Langmuir : the ACS journal of surfaces and colloids》2012,28(17):6848-6856
The intermetallic PdGa is a highly selective and potent catalyst in the semihydrogenation of acetylene, which is attributed to the surface stability and isolated Pd atom ensembles. In this context PdGa single crystals of form B with (111) orientation were investigated by means of X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning tunneling microscopy (STM), X-ray photoelectron diffraction (XPD), and low-energy electron diffraction (LEED) to study the electronic and geometric properties of this surface. UPS and thermal desorption spectroscopy (TDS) were used to probe the chemisorption behavior of CO. The PdGa(111) surface exhibits a (1 × 1) LEED and a pronounced XPD pattern indicating an unreconstructed bulk-truncated surface. Low-temperature STM reveals a smooth surface with a (1 × 1) unit cell. No segregation occurs, and no impurities are detected by XPS. The electronic structure and the CO adsorption properties reveal PdGa(111) to be a bulk-truncated intermetallic compound with Pd-Ga partial covalent bonding. 相似文献
997.
Permanent binary phase masks with planar surfaces and high tolerance to laser radiation are recorded in the volume of photo-thermo-refractive glass using the contact copying technique and binary amplitude master masks. Conversion of a Gaussian beam to higher order modes is shown. 相似文献
998.
We present a simple technique for measuring coherence times for stationary light fields using a single detector with tunable time resolution. By measuring the equal-time second-order correlation function at varying instrument response functions it is possible to determine the coherence time and also the shape of the temporal decay without the need to record time-resolved data. The technique is demonstrated for pseudothermal light. Possible applications for dynamic light scattering and photon statistics measurements are discussed. 相似文献
999.
P Orlandi C Ferrari M John Strain A Canciamilla F Morichetti M Sorel P Bassi A Melloni 《Optics letters》2012,37(17):3669-3671
We present the design and the fabrication of compact tunable silicon-on-insulator bandpass filters based on the integration of a Mach-Zehnder interferometer with ring resonators and activated via thermo-optic phase shifters. The proposed architecture provides wide filter bandwidth tunability from 10% to 90% of the free spectral range preserving the filter off-band rejection. Possible applications are channel subset selection in wavelength division multiplexing optical systems, adaptive filtering to signal bandwidth, and reconfigurable filters for gridless networking. 相似文献
1000.
Zwergel C Gaascht F Valente S Diederich M Bagrel D Kirsch G 《Natural product communications》2012,7(3):389-394
Aurones [2-benzylidenebenzofuran-3(2H)-ones] are either natural or synthetic compounds, belonging to the flavonoid family. They are isomeric to flavones and provide a bright yellow color to the plants in which they occur. Today, a literature survey indicates that the related flavonoids have been studied not only for their physiological properties and effects on Nature, but also for their therapeutic potential. Aurones are recently attracting the interest of an increasing number of research groups, and, since the last review, some interesting advances have been made in understanding the aurones. In this review, we report the recent advances made on the synthetic routes towards aurones. We also highlight their activity in different biological areas, as well as applied genetic plant modifications to produce these colored compounds. Their synthesis, structure-activity relationships and the importance of the substitution pattern will also be mentioned. Finally, some aspects regarding the possible development of aurones will be discussed briefly. 相似文献