全文获取类型
收费全文 | 704篇 |
免费 | 13篇 |
国内免费 | 4篇 |
专业分类
化学 | 212篇 |
晶体学 | 6篇 |
力学 | 7篇 |
数学 | 63篇 |
物理学 | 433篇 |
出版年
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 13篇 |
2012年 | 20篇 |
2011年 | 49篇 |
2010年 | 21篇 |
2009年 | 12篇 |
2008年 | 33篇 |
2007年 | 39篇 |
2006年 | 43篇 |
2005年 | 26篇 |
2004年 | 21篇 |
2003年 | 17篇 |
2002年 | 22篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 32篇 |
1995年 | 30篇 |
1994年 | 21篇 |
1993年 | 28篇 |
1992年 | 24篇 |
1991年 | 13篇 |
1990年 | 17篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 6篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1967年 | 3篇 |
排序方式: 共有721条查询结果,搜索用时 15 毫秒
701.
Aaltonen T Alvarez González B Amerio S Amidei D Anastassov A Annovi A Antos J Apollinari G Appel JA Apresyan A Arisawa T Artikov A Asaadi J Ashmanskas W Auerbach B Aurisano A Azfar F Badgett W Barbaro-Galtieri A Barnes VE Barnett BA Barria P Bartos P Bauce M Bauer G Bedeschi F Beecher D Behari S Bellettini G Bellinger J Benjamin D Beretvas A Bhatti A Binkley M Bisello D Bizjak I Bland KR Blumenfeld B Bocci A Bodek A Bortoletto D Boudreau J Boveia A Brau B Brigliadori L Brisuda A Bromberg C 《Physical review letters》2011,107(27):272001
We present a measurement of the B(s)(0) lifetime in fully and partially reconstructed B(s)(0)→D(s)(-)(?π(-))X decays in 1.3 fb(-1) collected in pp ˉ collisions at √s=1.96 TeV by the CDF II detector at the Fermilab Tevatron. We measure τ(B(s)(0))=1.518±0.041(stat)±0.027(syst) ps. The ratio of this result and the world average B(0) lifetime yields τ(B(s)(0))/τ(B(0))=0.99±0.03, which is in agreement with recent theoretical predictions. 相似文献
702.
Fast Computation of High‐Frequency Dirichlet Eigenmodes via Spectral Flow of the Interior Neumann‐to‐Dirichlet Map 下载免费PDF全文
We present a new algorithm for numerical computation of large eigenvalues and associated eigenfunctions of the Dirichlet Laplacian in a smooth, star‐shaped domain in ?d, d ≥ 2. Conventional boundary‐based methods require a root search in eigenfrequency k, hence take O(N3) effort per eigenpair found, where N = O(kd?1) is the number of unknowns required to discretize the boundary. Our method is O(N) faster, achieved by linearizing with respect to k the spectrum of a weighted interior Neumann‐to‐Dirichlet (NtD) operator for the Helmholtz equation. Approximations to the square roots kj of all O(N) eigenvalues lying in [k ? ?, k], where ? = O(1), are found with O(N3) effort. We prove an error estimate with C independent of k. We present a higher‐order variant with eigenvalue error scaling empirically as O(?5) and eigenfunction error as O(?3), the former improving upon the “scaling method” of Vergini and Saraceno. For planar domains (d = 2), with an assumption of absence of spectral concentration, we also prove rigorous error bounds that are close to those numerically observed. For d = 2 we compute robustly the spectrum of the NtD operator via potential theory, Nyström discretization, and the Cayley transform. At high frequencies (400 wavelengths across), with eigenfrequency relative error 10?10, we show that the method is 103 times faster than standard ones based upon a root search. © 2014 Wiley Periodicals, Inc. 相似文献
703.
Hindson BJ Gutierrez DM Ness KD Makarewicz AJ Metz TR Setlur US Benett WB Loge JM Colston BW Francis PS Barnett NW Dzenitis JM 《The Analyst》2008,133(2):248-255
We present a fully automated DNA purification module comprised of a micro-fabricated chip and sequential injection analysis system that is designed for use within autonomous instruments that continuously monitor the environment for the presence of biological threat agents. The chip has an elliptical flow channel containing a bed (3.5 x 3.5 mm) of silica-coated pillars with height, width and center-to-center spacing of 200, 15, and 30 microm, respectively, which provides a relatively large surface area (ca. 3 cm(2)) for DNA capture in the presence of chaotropic agents. We have characterized the effect of various fluidic parameters on extraction performance, including sample input volume, capture flow rate, and elution volume. The flow-through design made the pillar chip completely reusable; carryover was eliminated by flushing lines with sodium hypochlorite and deionized water between assays. A mass balance was conducted to determine the fate of input DNA not recovered in the eluent. The device was capable of purifying and recovering Bacillus anthracis genomic DNA (input masses from 0.32 to 320 pg) from spiked environmental aerosol samples, for subsequent analysis using polymerase chain reaction-based assays. 相似文献
704.
A novel technique is reported for counting the number and the percentage of CD4+ T lymphocytes in a polydimethylsiloxane (PDMS) microchannel. This system integrates optical fluorescence detection with resistive pulse sensing enhanced by a metal oxide semiconductor field effect transistor (MOSFET). The MOSFET signal indicates the total number of the cells passing through the detection channel, while the concurrent fluorescence signal records only the number of cells tagged with a specific fluorescent dye. The absolute count of the CD4+ T cells and its percentage to the total lymphocytes can be analyzed by combining the two counting results, which shows comparable accuracy to those from the commercial flow cytometer. The fastest observed counting rate for a single-channel microchip is 8.5 cells per second. This technique is highly promising as it could greatly reduce the cost for HIV diagnosis and treatment and make it accessible to resource-poor developing countries. 相似文献
705.
706.
Zammit EM Barbante GJ Carlson B Doeven EH Barnett NW Hogan CF Richter MM Francis PS 《The Analyst》2012,137(12):2766-2769
The reaction of various [Os(L)(2)(L')](2+) complexes (where L and L' are phenanthroline, diphosphine or diarsine ligands) and organic reducing agents after chemical or electrochemical oxidation of the reactants produces an emission of light corresponding to MLCT transitions. In certain instances, the emission was greater than that of [Ru(bipy)(3)](2+), but the relative signals were dependent on many factors, including reagent concentration, mode of oxidation, reducing agent and the sensitivity of the photodetector over the wavelength range. 相似文献
707.
At least one third of all proteins are thought to require a metal ion co-factor for their function. Recognition of the importance
of metals in biological systems and major advances in analytical instrumentation and technology have led to the emergence
of the new research area of metalloproteomics in recent years. Despite this progress, the experimental determination of in-vivo
metal cofactors has remained challenging, because this requires elucidation of protein interactions with non-covalently bound
metal ions. This critical review highlights current methodological approaches, focusing, in particular, on issues relating
to the fractionation and separation of the metalloproteome, including recent experience with metalloproteomics for marine
cyanobacteria in our laboratory. Metalloproteomics promises to deliver novel insights into fundamental biological processes
in the future, but it is clear that further methodological advances are necessary to exploit the full potential of this emerging
research area. 相似文献
708.
Abulencia A Acosta D Adelman J Affolder T Akimoto T Albrow MG Ambrose D Amerio S Amidei D Anastassov A Anikeev K Annovi A Antos J Aoki M Apollinari G Arguin JF Arisawa T Artikov A Ashmanskas W Attal A Azfar F Azzi-Bacchetta P Azzurri P Bacchetta N Bachacou H Badgett W Barbaro-Galtieri A Barnes VE Barnett BA Baroiant S Bartsch V Bauer G Beachemin PH Bedeschi F Behari S Belforte S Bellettini G Bellinger J Belloni A Ben-Haim E Benjamin D Beretvas A Beringer J Berry T Bhatti A Binkley M Bisello D 《Physical review letters》2006,97(17):171802
We present the results of a search for new physics in the jets plus missing transverse energy data sample collected from 368 pb(-1) of pp collisions at square root of s = 1.96 TeV recorded by the Collider Detector at Fermilab. We compare the number of events observed in the data with a data-based estimate of the standard model backgrounds contributing to this signature. We observe no significant excess of events, and we interpret this null result in terms of lower limits on the fundamental Planck scale for a large extra dimensions scenario. 相似文献
709.
Abulencia A Acosta D Adelman J Affolder T Akimoto T Albrow MG Ambrose D Amerio S Amidei D Anastassov A Anikeev K Annovi A Antos J Aoki M Apollinari G Arguin JF Arisawa T Artikov A Ashmanskas W Attal A Azfar F Azzi-Bacchetta P Azzurri P Bacchetta N Bachacou H Badgett W Barbaro-Galtieri A Barnes VE Barnett BA Baroiant S Bartsch V Bauer G Bedeschi F Behari S Belforte S Bellettini G Bellinger J Belloni A Ben-Haim E Benjamin D Beretvas A Beringer J Berry T Bhatti A Binkley M Bisello D Bishai M 《Physical review letters》2006,96(4):042003
We report the results of a search for a charged Higgs boson in the decays of top quarks produced in pp collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193 pb-1 collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t-->H+b) for different charged Higgs decay scenarios. In addition, we present in the minimal supersymmetric standard model (mH+/-, tanbeta) plane the first exclusion regions with radiative and Yukawa coupling corrections. 相似文献
710.
Padgett M Whyte G Girkin J Wright A Allen L Ohberg P Barnett SM 《Optics letters》2006,31(14):2205-2207
When light is transmitted along the axis of a rotating glass rod, the polarization of the light is rotated through a small angle [Proc. R. Soc. London, Ser. A349, 423 (1976)]. Under the same conditions, we predict a rotation of the transmitted image by exactly the same angle. The treatment of the two effects in terms of light's spin and orbital angular momentum suggests that they share a common origin. 相似文献