全文获取类型
收费全文 | 6289篇 |
免费 | 207篇 |
国内免费 | 26篇 |
专业分类
化学 | 4433篇 |
晶体学 | 39篇 |
力学 | 176篇 |
数学 | 964篇 |
物理学 | 910篇 |
出版年
2024年 | 6篇 |
2023年 | 57篇 |
2022年 | 187篇 |
2021年 | 201篇 |
2020年 | 161篇 |
2019年 | 157篇 |
2018年 | 114篇 |
2017年 | 116篇 |
2016年 | 253篇 |
2015年 | 213篇 |
2014年 | 223篇 |
2013年 | 331篇 |
2012年 | 398篇 |
2011年 | 492篇 |
2010年 | 280篇 |
2009年 | 258篇 |
2008年 | 388篇 |
2007年 | 361篇 |
2006年 | 364篇 |
2005年 | 334篇 |
2004年 | 306篇 |
2003年 | 244篇 |
2002年 | 207篇 |
2001年 | 78篇 |
2000年 | 69篇 |
1999年 | 75篇 |
1998年 | 48篇 |
1997年 | 52篇 |
1996年 | 77篇 |
1995年 | 48篇 |
1994年 | 46篇 |
1993年 | 39篇 |
1992年 | 48篇 |
1991年 | 39篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 16篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 12篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1906年 | 2篇 |
排序方式: 共有6522条查询结果,搜索用时 0 毫秒
201.
Grazioli C Alfè D Krishnakumar SR Sen Gupta S Veronese M Turchini S Bonini N Dal Corso A Sarma DD Baroni S Carbone C 《Physical review letters》2005,95(11):117201
The occurrence of a noncollinear magnetic structure at a Mn monolayer grown epitaxially on Fe(100) is predicted theoretically, using spinor density-functional theory, and observed experimentally, using x-ray magnetic circular dichroism (XMCD) and linear dichroism (XMLD) spectroscopies. The combined use of XMCD and XMLD at the Mn-absorption edge allows us to assess the existence of ferromagnetic and antiferromagnetic order at the interface, and also to determine the moment orientations with element specificity. The experimental results thus obtained are in excellent agreement with the magnetic structure determined theoretically. 相似文献
202.
A new method, called barrier coupling, for coupling light into ion-implanted waveguides is presented in analogy to prism coupling. Light is coupled by frustrated total reflection at the barrier region of decreased refractive index by proper variation of the incident angle. Effective indices of guided modes are determined by the minima of the non-incoupled reflected light. The method is used for the determination of the effective indices of an ion-implanted waveguide in KNbO3. It is simpler than most other techniques, more accurate, and nondestructive. 相似文献
203.
204.
Forster PM Burbank AR Livage C Férey G Cheetham AK 《Chemical communications (Cambridge, England)》2004,(4):368-369
Five different cobalt succinate materials synthesized from an identical starting mixture using temperature as the only independent variable show increasing condensation and density at higher synthesis temperatures. 相似文献
205.
Andrea Bonfiglioli Ermanno Lanconelli Francesco Uguzzoni 《Transactions of the American Mathematical Society》2004,356(7):2709-2737
We construct the fundamental solutions and for the non-divergence form operators and , where the 's are Hörmander vector fields generating a stratified group and is a positive-definite matrix with Hölder continuous entries. We also provide Gaussian estimates of and its derivatives and some results for the relevant Cauchy problem. Suitable long-time estimates of allow us to construct using both -saturation and approximation arguments.
206.
Using three-dimensional time-domain numerical simulations of the nonlinear dispersive Maxwell equations for a defect microcavity in a photonic crystal wire, we show that the transmission through the bandgap can be all-optically modulated via the generation of transient states associated with the nonlinear splitting of the defect mode. Analytical results based on time-domain coupled-mode theory are derived as well. 相似文献
207.
Modal conversion between the fundamental mode and the first-order (leaky) mode has been experimentally investigated in high-index-contrast integrated-optical bent waveguides. The matched bend condition has been experimentally confirmed on cascaded bends, and the effect of both matched and unmatched bends on Y branches has been investigated. Good agreement between theoretical predictions and experimental results for both monomode and multimode waveguides is achieved. It is demonstrated that, in bent waveguides, the modal conversion between the fundamental mode and the first (leaky) mode can be accurately controlled to avoid additional losses and transfer function impairments. 相似文献
208.
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
209.
The synthesis and self-association of protected oxymethylene-bridged UA analogues are described. 相似文献
210.
Grirrane A Pastor A Galindo A Ienco A Mealli C Rosa P 《Chemical communications (Cambridge, England)》2003,(4):512-513
The compound [Mn(tda)(bipy)] (tda = S(CH2COO)2(2-)) features the first structurally characterized tetra-carboxylate dimanganese antiferromagnetic system with 'copper acetate' core; the binuclear units, completed by bipyridine chelates, are doubly chained by the tda anions that adopt an unprecedented mu,mu'-eta1,eta1,eta1,eta1 coordination mode. 相似文献