全文获取类型
收费全文 | 345篇 |
免费 | 4篇 |
专业分类
化学 | 186篇 |
晶体学 | 2篇 |
力学 | 16篇 |
数学 | 49篇 |
物理学 | 96篇 |
出版年
2020年 | 2篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2014年 | 8篇 |
2013年 | 8篇 |
2012年 | 8篇 |
2011年 | 11篇 |
2010年 | 5篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 12篇 |
2004年 | 13篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 9篇 |
2000年 | 15篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1989年 | 3篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1975年 | 8篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 4篇 |
1968年 | 3篇 |
1965年 | 2篇 |
1932年 | 3篇 |
1913年 | 2篇 |
1902年 | 2篇 |
1884年 | 1篇 |
排序方式: 共有349条查询结果,搜索用时 15 毫秒
1.
E. N. Sobol’ O. I. Baum A. V. Bol’shunov V. I. Sipliviy N. Yu. Ignat’eva O. L. Zakharkina V. V. Lunin A. I. Omel’chenko V. A. Kamenskiy A. V. Myakov 《Laser Physics》2006,16(5):735-740
A new approach to alterations in eye refraction upon nondestructive laser action on the sclera and cornea is studied. It is demonstrated in in vivo experiments on rabbit eyes that sequential laser irradiation of the sclera and cornea yields a significant alteration in the eye refraction. The collagen structure of the sclera and cornea is studied after the nondestructive laser action with noninvasive polarization-sensitive optical coherence tomography. It is demonstrated that collagen fibers that provide for the cornea tension and applanation partially survive in the zone of the local denaturation of sclera. An irradiation mode that corresponds to an increase in the cornea’s plasticity and does not cause visible structural changes is chosen. The simplest theoretical model for alterations in the eye refraction upon the nonablative laser action on sclera is analyzed. The alteration in the cornea curvature upon stretching resulting from the local sclera coagulation and the corresponding decrease in its volume is calculated. The model makes it possible to approximately estimate the laser irradiation modes that provide the desired alterations in eye refraction. 相似文献
2.
Yu You George W. Kattawar Ping Yang Yong X. Hu Bryan A. Baum 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,100(1-3):470-482
Measurements from depolarized lidars provide a promising method to retrieve both cloud and aerosol properties and a versatile complement to passive satellite-based sensors. For lidar observations of clouds and aerosols, multiple scattering plays an important role in the scattering process. Monte Carlo simulations are carried out to investigate the sensitivity of lidar backscattering depolarization to cloud and aerosol properties. Lidar parameters are chosen to be similar to those of the upcoming space-based CALIPSO lidar. Cases are considered that consist of a single cloud or aerosol layer, as well as a case in which cirrus clouds overlay different types of aerosols. It is demonstrated that besides thermodynamic cloud phase, the depolarized lidar signal may provide additional information on ice or aerosol particle shapes. However, our results show little sensitivity to ice or aerosol particle sizes. Additionally, for the case of multiple but overlapping layers involving both clouds and aerosols, the depolarized lidar contains information that can help identify the particle properties of each layer. 相似文献
3.
Intermolecular rhodium-catalyzed [m + n + o] reactions of 1,6-enynes and various pi-components (carbon monoxide, alkynes, 1,3-butadienes, etc.) provide an expeditious approach for the construction of polycyclic fragments that represent important synthons for target-directed synthesis. We present computational and experimental evidence for the existence of a previously undescribed reaction pathway for the rhodium-catalyzed [4 + 2 + 2] reaction involving a 1,6-enyne. This model clearly demonstrates the origin of the excellent diastereoselectivity in this type of reaction and the remarkable tolerance of both (E)- and (Z)-isomers within the 1,6-enyne, which is generally prone to competitive ene-cycloisomerization. 相似文献
4.
5.
Köhnlein H Purath A Klemp C Baum E Krossing I Stösser G Schnöckel H 《Inorganic chemistry》2001,40(19):4830-4838
A disproportionation process of a metastable AlCl solution with a simultaneous ligand exchange-Cl is substituted by N(SiMe(3))(2)-leads to a [Al(69)[N(SiMe(3))(2)](18)](3-) cluster compound that can be regarded as an intermediate on the way to bulk metal formation. The cluster was characterized by an X-ray crystal structural analysis. Regarding its structure and the packing within the crystal, this metalloid cluster with 4 times more Al atoms than ligands is compared to the [Al(77)N(SiMe(3))(2)](20)](2-) cluster that has been published four years ago. Although there is a similar packing density of the Al atoms in both clusters as well as in Al metal, the X-ray structural analysis shows significant differences in topology and distance proportions. The differences between these-at a first glance almost identical-Al clusters demonstrate that results of physical measuring, e.g., of nanostructured surfaces which carry supposedly identical cluster species, have to be interpreted with great caution. 相似文献
6.
7.
8.
Solvation of the lithium ion by acetone was studied in acetone-nitromethane solutions by Raman, infrared, and7Li and35Cl NMR spectroscopic techniques. It was confirmed that the 390-cm?1 IR acetone band is split by the lithium ion and that a 369-cm?1 IR band, attributed by other authors to Li+-nitromethane vibration, is due to the vibration of acetone in the lithium inner solvation shell. The frequency of the Li+-nitromethane vibrational band is strongly anion dependent due to contact-ion-pair formation. Several different techniques indicate that Li+ is solvated by four acetone molecules, and approximate equilibrium-constant values for the stepwise solvation reaction were calculated. The influence of weak complexing agents on Li+ ClO 4 ? ion-pair formation was investigated. 相似文献
9.
Xiaoyi Wang Mark D. Wilkinson Xiaoyan Lin Ren Ren Keith R. Willison Aleksandar P. Ivanov Jake Baum Joshua B. Edel 《Chemical science》2020,11(4):970
Actin is a key protein in the dynamic processes within the eukaryotic cell. To date, methods exploring the molecular state of actin are limited to insights gained from structural approaches, providing a snapshot of protein folding, or methods that require chemical modifications compromising actin monomer thermostability. Nanopore sensing permits label-free investigation of native proteins and is ideally suited to study proteins such as actin that require specialised buffers and cofactors. Using nanopores, we determined the state of actin at the macromolecular level (filamentous or globular) and in its monomeric form bound to inhibitors. We revealed urea-dependent and voltage-dependent transitional states and observed the unfolding process within which sub-populations of transient actin oligomers are visible. We detected, in real-time, filament-growth, and drug-binding at the single-molecule level demonstrating the promise of nanopore sensing for in-depth understanding of protein folding landscapes and for drug discovery.Nanopipettes were used for real-time investigation into actin dynamics and drug binding at single-molecule resolution, showing promise for a better understanding of the mechanism of protein–protein interactions and drug discovery. 相似文献
10.
Nelson A Belitsky JM Vidal S Joiner CS Baum LG Stoddart JF 《Journal of the American Chemical Society》2004,126(38):11914-11922
A self-assembled pseudopolyrotaxane consisting of lactoside-displaying cyclodextrin (CD) "beads" threaded onto a linear polyviologen "string" was investigated for its ability to inhibit galectin-1-mediated T-cell agglutination. The CDs of the pseudopolyrotaxane are able to spin around the axis of the polymer chain as well as to move back and forth along its backbone to alter the presentation of its ligand. This supramolecular superstructure incorporates all the advantages of polymeric structures, such as the ability to span large distances, along with a distinctively dynamic presentation of its lactoside ligands to afford a neoglycoconjugate that can adjust to the relative stereochemistries of the lectin's binding sites. The pseudopolyrotaxane exhibited a valency-corrected 10-fold enhancement over native lactose in the agglutination assay, which was greater than the enhancements observed for lactoside-bearing trivalent glycoclusters and a lactoside-bearing chitosan polymer tested using the same assay. The experimental results indicate that supramolecular architectures, such as the pseudopolyrotaxane, provide tools for investigating protein-carbohydrate interactions. 相似文献