全文获取类型
收费全文 | 540篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
化学 | 293篇 |
晶体学 | 7篇 |
力学 | 15篇 |
数学 | 77篇 |
物理学 | 163篇 |
出版年
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 17篇 |
2015年 | 12篇 |
2014年 | 10篇 |
2013年 | 31篇 |
2012年 | 30篇 |
2011年 | 29篇 |
2010年 | 21篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 20篇 |
2006年 | 31篇 |
2005年 | 28篇 |
2004年 | 20篇 |
2003年 | 22篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 14篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1984年 | 7篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 9篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 9篇 |
1969年 | 4篇 |
1968年 | 3篇 |
1963年 | 3篇 |
排序方式: 共有555条查询结果,搜索用时 0 毫秒
551.
Sidorov-Biryukov DA Fernandez A Zhu L Verhoef A Dombi P Pugzlys A Serebryannikov EE Zheltikov AM Knight JC Baltuska A 《Optics letters》2008,33(5):446-448
A linear technique of phase measurement based on spectral interferometry is employed to visualize the fine details in the spectral phase of a soliton produced in a highly nonlinear photonic crystal fiber (PCF) with a resolution better than 0.1 nm. Gigahertz features have been resolved in the spectral phase of the soliton PCF output, allowing the accuracy of time-domain soliton envelope reconstruction to be improved on the timescale of a few femtoseconds. 相似文献
552.
Tanaka Y Takeuchi T Lovesey SW Knight KS Chainani A Takata Y Oura M Senba Y Ohashi H Shin S 《Physical review letters》2008,100(14):145502
Enantiomers, or stereoisomers, have crystal structures that are mirror images of each other and are thus handed, like our right and left hands. The physical properties of enantiomers are identical except for optical activity, which rotates linearly polarized light by equal amounts but in opposite directions. While conventional x-ray Bragg diffraction can determine crystal structures, it does not distinguish between right- and left-handed crystals. We show resonant Bragg diffraction using circularly polarized x rays reveals the handedness of crystals by coupling x-ray helicity to a crystal screw axis. The intensity of resonantly allowed reflection of alpha-quartz is well described by an admixture of a parity-even and a parity-odd process. Our results are of general importance and demonstrate a new method to directly study chiral motifs in structures that include biomaterials, liquid crystals, magnets, multiferroics, etc. 相似文献
553.
As part of a programme to develop a metrological framework for single molecule measurements in biology, we have investigated
the applications of single molecule imaging to genomics. Specifically, we have developed a technique for measuring the frequencies
of single nucleotide polymorphisms (SNPs) in complex or pooled samples of DNA. We believe that this technique has applications
to statistical genotyping—the identification of correlations between SNP frequencies and particular phenotypes—and other areas
where it is desirable to track the frequencies of SNPs in complex DNA populations. 相似文献
554.
Protoglobin-Catalyzed Formation of cis-Trifluoromethyl-Substituted Cyclopropanes by Carbene Transfer
Lucas Schaus Dr. Anuvab Das Dr. Anders M. Knight Dr. Gonzalo Jimenez-Osés Prof. Dr. K. N. Houk Dr. Marc Garcia-Borràs Prof. Dr. Frances H. Arnold Prof. Dr. Xiongyi Huang 《Angewandte Chemie (International ed. in English)》2023,62(4):e202208936
Trifluoromethyl-substituted cyclopropanes (CF3-CPAs) constitute an important class of compounds for drug discovery. While several methods have been developed for synthesis of trans-CF3-CPAs, stereoselective production of corresponding cis-diastereomers remains a formidable challenge. We report a biocatalyst for diastereo- and enantio-selective synthesis of cis-CF3-CPAs with activity on a variety of alkenes. We found that an engineered protoglobin from Aeropyrnum pernix (ApePgb) can catalyze this unusual reaction at preparative scale with low-to-excellent yield (6–55 %) and enantioselectivity (17–99 % ee), depending on the substrate. Computational studies revealed that the steric environment in the active site of the protoglobin forced iron-carbenoid and substrates to adopt a pro-cis near-attack conformation. This work demonstrates the capability of enzyme catalysts to tackle challenging chemistry problems and provides a powerful means to expand the structural diversity of CF3-CPAs for drug discovery. 相似文献
555.
Mario Suwalsky Jaime Tapia Elizabeth Knight Leonora Duk Carmen G. Seguel Fernando Neira 《Macromolecular Symposia》1986,2(1):105-112
Oriented films of three diacylphosphatidylethanolamines containing 12, 14 and 16 methylene groups in their hydrocarbon chains and one 14 carbon chain lecithin were studied by X-ray fiber diffraction. Their molecular conformations, packing arrangement, crystallographic and physico-chemical parameters as a function of hydration were determined. Basically the four phospholipids exhibit a common bilayer structure. However, they also present some interesting differences which might be relevant to their biological functions. 相似文献