全文获取类型
收费全文 | 3798篇 |
免费 | 228篇 |
国内免费 | 28篇 |
专业分类
化学 | 2928篇 |
晶体学 | 53篇 |
力学 | 106篇 |
综合类 | 1篇 |
数学 | 355篇 |
物理学 | 611篇 |
出版年
2023年 | 22篇 |
2022年 | 12篇 |
2021年 | 54篇 |
2020年 | 74篇 |
2019年 | 103篇 |
2018年 | 40篇 |
2017年 | 39篇 |
2016年 | 138篇 |
2015年 | 135篇 |
2014年 | 163篇 |
2013年 | 254篇 |
2012年 | 292篇 |
2011年 | 401篇 |
2010年 | 250篇 |
2009年 | 173篇 |
2008年 | 308篇 |
2007年 | 209篇 |
2006年 | 203篇 |
2005年 | 243篇 |
2004年 | 185篇 |
2003年 | 145篇 |
2002年 | 124篇 |
2001年 | 58篇 |
2000年 | 58篇 |
1999年 | 26篇 |
1998年 | 32篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 19篇 |
1994年 | 15篇 |
1993年 | 16篇 |
1992年 | 16篇 |
1991年 | 19篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 13篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1974年 | 6篇 |
1972年 | 5篇 |
1971年 | 5篇 |
排序方式: 共有4054条查询结果,搜索用时 203 毫秒
1.
Gitae Moon Intae Son Chunho Kim Chi Hyeong Cho Eunbi Lee Eun Hyoung Bae 《Molecular Crystals and Liquid Crystals》2019,687(1):60-67
AbstractTo enable recent 3D and moving picture applications, liquid crystal displays (LCD) must exhibit fast response and wide viewing angle characteristics. Pre-tilted vertical alignment layers for high-speed LCD were fabricated using bi-functional photoreactive monomers. The monomers can be confined to the polyimide layer and photo-polymerized by UV exposure under voltage. Response characteristics of photo-controlled alignment films according to the structure were investigated. Vertical alignment properties were evaluated using a polarizing optical microscope, and electro-optical characteristics were compared through the voltage-transmittance curve and response time measurement. Faster response speed could be obtained by using photoreactive monomers having a long alkyl chain. 相似文献
2.
Journal of Statistical Physics - In this paper, we consider the existence problem for a stationary relaxational models of the quantum Boltzmann equation. More precisely, we establish the existence... 相似文献
3.
4.
5.
Quantitative analysis of polyhexamethylene guanidine (PHMG) oligomers via matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry with an ionic‐liquid matrix 下载免费PDF全文
6.
7.
A New Concept for Obtaining SnO2 Fiber‐in‐Tube Nanostructures with Superior Electrochemical Properties 下载免费PDF全文
Young Jun Hong Ji‐Wook Yoon Prof. Jong‐Heun Lee Prof. Yun Chan Kang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):371-376
Tin oxide (SnO2) nanotubes with a fiber‐in‐tube structure have been prepared by electrospinning and the mechanism of their formation has been investigated. Tin oxide‐carbon composite nanofibers with a filled structure were formed as an intermediate product, which were then transformed into SnO2 nanotubes with a fiber‐in‐tube structure during heat treatment at 500 °C. Nanofibers with a diameter of 85 nm were found to be located inside hollow nanotubes with an outer diameter of 260 nm. The prepared SnO2 nanotubes had well‐developed mesopores. The discharge capacities of the SnO2 nanotubes at the 2nd and 300th cycles at a current density of 1 A g?1 were measured as 720 and 640 mA h g?1, respectively, and the corresponding capacity retention measured from the 2nd cycle was 88 %. The discharge capacities of the SnO2 nanotubes at incrementally increased current densities of 0.5, 1.5, 3, and 5 A g?1 were 774, 711, 652, and 591 mA h g?1, respectively. The SnO2 nanotubes with a fiber‐in‐tube structure showed superior cycling and rate performances compared to those of SnO2 nanopowder. The unique structure of the SnO2 nanotubes with a fiber@void@tube configuration improves their electrochemical properties by reducing the diffusion length of the lithium ions, and also imparts greater stability during electrochemical cycling. 相似文献
8.
Jongeun Kang Eunha Hwang Hyunseung Lee Mi Young Cho Sanu Karan Hak Nam Kim Jong Seung Kim Jonathan L. Sessler Sankarprasad Bhuniya Kwan Soo Hong 《Molecules (Basel, Switzerland)》2021,26(7)
We have synthesized new magnetic resonance imaging (MRI) T1 contrast agents (CA1 and CA2) that permit the activatable recognition of the cellular vicinal thiol motifs of the protein thioredoxin. The contrast agents showed MR relaxivities typical of gadolinium complexes with a single water molecule coordinated to a Gd3+ center (i.e., ~4.54 mM−1s−1) for both CA1 and CA2 at 60 MHz. The contrast agent CA1 showed a ~140% relaxivity enhancement in the presence of thioredoxin, a finding attributed to a reduction in the flexibility of the molecule after binding to thioredoxin. Support for this rationale, as opposed to one based on preferential binding, came from 1H-15N-HSQC NMR spectral studies; these revealed that the binding affinities toward thioredoxin were almost the same for both CA1 and CA2. In the case of CA1, T1-weighted phantom images of cancer cells (MCF-7, A549) could be generated based on the expression of thioredoxin. We further confirmed thioredoxin expression-dependent changes in the T1-weighted contrast via knockdown of the expression of the thioredoxin using siRNA-transfected MCF-7 cells. The nontoxic nature of CA1, coupled with its relaxivity features, leads us to suggest that it constitutes a first-in-class MRI T1 contrast agent that allows for the facile and noninvasive monitoring of vicinal thiol protein motif expression in live cells. 相似文献
9.
Ding Tian Taliehsadat Alebrahim Gregory K. Kline Liwen Chen Haiqing Lin Chulsung Bae 《Journal of polymer science. Part A, Polymer chemistry》2020,58(18):2654-2663
Polymeric membrane-based gas separation technology has significant advantages compared with traditional amine-based CO2 separation method. In this work, SEBS block copolymer is used as a polymer matrix to incorporate triethylene oxide (TEO) functionality. The short ethylene oxide segment is chosen to avoid crystallization, which is confirmed by differential scanning calorimetry and wide-angle X-ray scattering characterizations. The gas permeability results reveal that CO2/N2 selectivity increased with increasing content of TEO functional group. The highest CO2 permeability (281 Barrer) and CO2/N2 selectivity (31) were obtained for the membrane with the highest TEO incorporation (57 mol%). Increasing the TEO content in these copolymers results in an increase in CO2 solubility and a decrease in C2H6 solubility. For example, as the grafted TEO content increased from 0 to 57 mol%, the CO2 solubility and CO2/C2H6 solubility selectivity increased from 0.72 to 1.3 cm3(STP)/cm3 atm and 0.47 to 1.3 at 35°C, respectively. The polar ether linkage in TEO-grafted SEBS copolymers exhibits favorable interaction with CO2 and unfavorable interaction with nonpolar C2H6, thus enhancing CO2/C2H6 solubility selectivity. 相似文献
10.
Prof. Wook Lee Prof. Spiridoula Matsika 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(62):14181-14186
Cyclobutane pyrimidine dimer (CPD) is a photoproduct formed by two stacked pyrimidine bases through a cycloaddition reaction upon irradiation. Owing to its close association with skin cancer, the mechanism of CPD formation has been studied thoroughly. Among many aspects of CPD, its formation involving 5-methylcytosine (5mC) has been of special interest because the CPD yield is known to increase with C5-methylation of cytosine. In this work, high-level quantum mechanics/molecular mechanics (QM/MM) calculations are used to examine a previously experimentally detected pathway for CPD formation in hetero (thymine-cytosine and thymine-5mC) dipyrimidines, which is facilitated through intersystem crossing in thymine and formation of a triplet biradical intermediate. A DNA duplex model system containing a core sequence TmCG or TCG is used. The stabilization of a radical center in the biradical intermediate by the methyl group of 5mC can lead to increased CPD yield in TmCG compared with its non-methylated counterpart, TCG, thereby suggesting the existence of a new pathway of CPD formation enhanced by 5mC. 相似文献