全文获取类型
收费全文 | 818篇 |
免费 | 30篇 |
专业分类
化学 | 605篇 |
晶体学 | 2篇 |
力学 | 12篇 |
数学 | 132篇 |
物理学 | 97篇 |
出版年
2023年 | 4篇 |
2021年 | 4篇 |
2020年 | 21篇 |
2019年 | 17篇 |
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 23篇 |
2015年 | 30篇 |
2014年 | 27篇 |
2013年 | 36篇 |
2012年 | 52篇 |
2011年 | 40篇 |
2010年 | 28篇 |
2009年 | 34篇 |
2008年 | 43篇 |
2007年 | 42篇 |
2006年 | 38篇 |
2005年 | 39篇 |
2004年 | 39篇 |
2003年 | 36篇 |
2002年 | 29篇 |
2001年 | 23篇 |
2000年 | 11篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1984年 | 8篇 |
1982年 | 5篇 |
1976年 | 5篇 |
1959年 | 7篇 |
1957年 | 4篇 |
1956年 | 4篇 |
1955年 | 4篇 |
1942年 | 4篇 |
1937年 | 3篇 |
1935年 | 3篇 |
1934年 | 3篇 |
1933年 | 4篇 |
1922年 | 7篇 |
1920年 | 3篇 |
1919年 | 3篇 |
排序方式: 共有848条查询结果,搜索用时 15 毫秒
51.
Xilin Peng Augusto Morrone Konstantin Nikolaev Mark Kief Mark Ostrowski 《Journal of magnetism and magnetic materials》2009,321(18):2902-2910
In this paper, we investigated the effect of background base pressure, wafer-transferring time between process modules, and stack layer material selection on the current-in-plane giant magneto-resistive (CIP-GMR) interface properties and the resulted CIP-GMR performance. Experimental results showed that seed layer/AFM interface, AFM/pinned layer (PL) interface, pinned layer/Ru interface, and reference layer (RL)/Cu spacer interface are among the most critical ones for a CIP-GMR device. By reducing the background impurity level (water moisture and oxygen), optimizing the wafer process flow sequence, and careful stack-layer material selection, such critical interfaces in a CIP-GMR device can be preserved. Consequently, a much robust GMR performance control can be achieved. 相似文献
52.
53.
The tetxaacetylation of isobutene has been perfomed in AlCl3/AcCl. Treatment of the crude reaction medium with liquid ammonia yields the title compound. 相似文献
54.
For fully developed turbulence in an incompressible fluid described by the Navier-Stokes equations with Gaussian random forces the relation between the energy spectrum and the stirring mechanism is investigated within a variational approach. Therein, the effect of nonlinear mode coupling is approximated by a wave number dependent eddy viscosity determined via a nonlinear integral equation for the energy spectrum. For various stirring spectra analytic approximations are compared with the solution obtained numerically with a cutoff in the integral kernel which ensures in eddy relaxing processes that the stirring forces exert strain only on scales larger than the eddy size. The results are compared with renormalization group calculations and closure approximations. Random forces injecting energy at a ratek
–1 into the wave number banddk aroundk lead to a Kolmogorov distribution of energy. The spectrum of small-scale velocity fluctuations is shown to be universal in the sense that it remains unchanged under variations of the long wavelength stirring spectra. 相似文献
55.
In this research we study the critical dynamics of anisotropic layers in the various transition and crossover regimes associated with a defect unbinding picture of the melting process. We derive dynamic equations of motion for anisotropic solids, smectics and nematics, in the presence of defects and predict the critical behavior of various transport coefficients. The theory is applicable to two-dimensional layers of freely suspended liquid crystals, on which dynamic light-scattering experiments can be performed to test the predictions of the theory. 相似文献
56.
57.
Ihling C Berger K Höfliger MM Führer D Beck-Sickinger AG Sinz A 《Rapid communications in mass spectrometry : RCM》2003,17(12):1240-1246
Fourier transform ion-cyclotron resonance (FTICR) mass spectrometry offers several advantages for the analysis of biological samples, including excellent mass resolution, ultra-high mass measurement accuracy, high sensitivity, and wide mass range. We report the application of a nano-HPLC system coupled to an FTICR mass spectrometer equipped with nanoelectrospray source (nano-HPLC/nano-ESI-FTICRMS) for proteome analysis. Protein identification in proteomics is usually conducted by accurately determining peptide masses resulting from enzymatic protein digests and comparing them with theoretically digested protein sequences from databases. A tryptic in-solution digest of bovine serum albumin was used to optimize experimental conditions and data processing. Spots from Coomassie Blue and silver-stained two-dimensional (2D) gels of human thyroid tissue were excised, in-gel digested with trypsin, and subsequently analyzed by nano-HPLC/nano-ESI-FTICRMS. Additionally, we analyzed 1D-gel bands of membrane preparations of COS-6 cells from African green monkey kidney as an example of more complex protein mixtures. Nano-HPLC was performed using 1-mm reverse-phase C-18 columns for pre-concentration of the samples and reverse-phase C-18 capillary columns for separation, applying water/acetonitrile gradient elution conditions at flow rates of 200 nL/min. Mass measurement accuracies smaller than 3 ppm were routinely obtained. Different methods for processing the raw data were compared in order to identify a maximum number of peptides with the highest possible degree of automation. Parallel identification of proteins from complex mixtures down to low-femtomole levels makes nano-HPLC/nano-ESI-FTICRMS an attractive approach for proteome analysis. 相似文献
58.
McGuinness DS Wasserscheid P Keim W Morgan D Dixon JT Bollmann A Maumela H Hess F Englert U 《Journal of the American Chemical Society》2003,125(18):5272-5273
Cr(III) complexes of tridentate SNS ligands have been prepared and evaluated as catalysts for ethylene trimerization, with several giving very high activity and excellent selectivity toward 1-hexene when activated with methylaluminoxane. The new complexes illustrate the potential of sulfur-based ligands on early transition metals for catalysis. 相似文献
59.
Jorge M. Garcia Ulrich Wurstbauer Antonio Levy Loren N. Pfeiffer Aron Pinczuk Annette S. Plaut Lei Wang Cory R. Dean Roberto Buizza Arend M. Van Der Zande James Hone Kenji Watanabe Takashi Taniguchi 《Solid State Communications》2012,152(12):975-978
The growth of single layer graphene nanometer size domains by solid carbon source molecular beam epitaxy on hexagonal boron nitride (h-BN) flakes is demonstrated. Formation of single-layer graphene is clearly apparent in Raman spectra which display sharp optical phonon bands. Atomic-force microscope images and Raman maps reveal that the graphene grown depends on the surface morphology of the h-BN substrates. The growth is governed by the high mobility of the carbon atoms on the h-BN surface, in a manner that is consistent with van der Waals epitaxy. The successful growth of graphene layers depends on the substrate temperature, but is independent of the incident flux of carbon atoms. 相似文献
60.
Annette Huber 《Mathematische Nachrichten》2008,281(12):1764-1776
We clarify the expected properties of the slice filtration on triangulated motives from the point of view of the generalized Hodge conjecture. In the appendix, J. Ayoub proves unconditionally that the slice filtration does not respect geometric motives. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献