全文获取类型
收费全文 | 2596篇 |
免费 | 389篇 |
国内免费 | 67篇 |
专业分类
化学 | 2772篇 |
晶体学 | 6篇 |
力学 | 10篇 |
综合类 | 12篇 |
数学 | 7篇 |
物理学 | 245篇 |
出版年
2024年 | 5篇 |
2023年 | 21篇 |
2022年 | 80篇 |
2021年 | 101篇 |
2020年 | 95篇 |
2019年 | 83篇 |
2018年 | 50篇 |
2017年 | 57篇 |
2016年 | 143篇 |
2015年 | 136篇 |
2014年 | 152篇 |
2013年 | 208篇 |
2012年 | 169篇 |
2011年 | 183篇 |
2010年 | 151篇 |
2009年 | 166篇 |
2008年 | 150篇 |
2007年 | 142篇 |
2006年 | 128篇 |
2005年 | 123篇 |
2004年 | 124篇 |
2003年 | 106篇 |
2002年 | 54篇 |
2001年 | 59篇 |
2000年 | 78篇 |
1999年 | 50篇 |
1998年 | 30篇 |
1997年 | 35篇 |
1996年 | 29篇 |
1995年 | 33篇 |
1994年 | 18篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有3052条查询结果,搜索用时 15 毫秒
81.
Qianyu Yu Xiaoteng Ma Yingze Liu Prof. Dr. Hanying Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(72):16712-16717
Protein nanogels have found a wide variety of applications, ranging from biocatalysis to drug/protein delivery. However, in practical applications, proteins in nanogels may suffer from enzymic hydrolysis and denaturation. Inspired by the structure and functionalities of the fowl eggshells, biomimetic mineralization of protein nanogels was studied in this research. Protein nanogels with embedded porcine pancreas lipase (PPL) in the cross-linked nanostructures were synthesized through the thiol–disulfide reaction between thiol-functionalized PPL and poly(N-isopropylacrylamide) with pendant pyridyl disulfide groups. The nanogels were further reacted with reduced bovine serum albumin (BSA) and BSA molecules were coated on the nanogels. Mineralization of BSA leads to the synthesis of biomineralized shells on the nanogels. With the growth of CaCO3 on the shells, the nanogels aggregate into suprastructures. Thermogravimetric analysis, XRD, dynamic light scattering, and TEM were employed to study the mechanism of the biomineralization process and analyze the structures of the mineralized nanogels. The biomineralized shells can effectively protect the PPL molecules from hydrolysis by trypsin; meanwhile, the nanosized channels on the mineralized shells allow the transport of small-molecule substrates across the shells. Bioactivity measurements indicate that PPL in the nanogels maintains more than 80 % bioactivity after biomineralization. 相似文献
82.
83.
Yongho Shin Tae Yeon Kong Jae Cheol Cheong Jin Young Kim Jae Il Lee Hye Suk Lee 《Biomedical chromatography : BMC》2019,33(9)
A liquid chromatography–tandem mass spectrometric method for the simultaneous determination of 75 abuse drugs and metabolites, including 19 benzodiazepines, 19 amphetamines, two opiates, eight opioids, cocaine, lysergic acid diethylamide, zolpidem, three piperazines and 21 metabolites in human hair samples, was developed and validated. Ten‐milligram hair samples were decontaminated, pulverized using a ball mill, extracted with 1 mL of methanol spiked with 28 deuterated internal standards in an ultrasonic bath for 60 min at 50°C, and purified with Q‐sep dispersive solid‐phase extraction tubes. The purified extracts were evaporated to dryness and the residue was dissolved in 0.1 mL of 10% methanol. The 75 analytes were analyzed on an Acquity HSS T3 column using gradient elution of methanol and 0.1% formic acid and quantified in multiple reaction monitoring mode with positive electrospray ionization. Calibration curves were linear (r ≥ 0.9951) from the lower limit of quantitation (2–200 pg/mg depending on the drug) to 2000 pg/mg. The coefficients of variation and accuracy for intra‐ and inter‐assay analysis at three QC levels were 4.3–12.9% and 89.2–109.1%, respectively. The overall mean recovery ranged from 87.1 to 105.3%. This method was successfully applied to the analysis of 11 forensic hair samples obtained from drug abusers. 相似文献
84.
Eduard N. Chikvaidze Tamar M. Partskhaladze Temur V. Gogoladze 《Magnetic resonance in chemistry : MRC》2014,52(7):377-382
The definition of the concentration of pheomelanin in the skin is an issue of great interest because in the case of being influenced by UV radiation, it manifests itself as a prooxidant, causing various skin disorders including melanoma that might help to explain the relatively high incidence of skin cancer among individuals with red hair. The ESR spectra of red hair samples were investigated. It was found that at low microwave power, they are characterized by two types of spectra. Red hair ESR signals result from a superposition of two spectral shapes, a singlet spectrum as a result of the existence of eumelanin and a triplet spectrum as a result of the existence of pheomelanin. At high microwave power, only triplet spectra shape was detected, caused by saturation of the eumelanin singlet. Using different concentration ratios of black to red hair, we measured ESR spectra and plotted the ratio values in each sample against a measured ‘g‐factor’ (experimental). We found that there is a linear relationship between these two parameters. So, it is evident that using these results, the concentration ratio of pheomelanin to eumelanin in a sample of hair can be easily determined by an almost noninvasive method. This can be considered a potential advantage for many practical activities compared with other invasive methods. The concentration dependence curve of pheomelanin (µg/mg) on gexp‐factor in an ESR spectrum of hair has been designed, which allows the determination of the amount of pheomelanin in hair of any color. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
85.
Dr. Marco Marazzi Dr. Hugo Gattuso Dr. Maria Fumanal Dr. Chantal Daniel Dr. Antonio Monari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(10):2519-2526
A computational investigation of the triplet excited states of a rhenium complex electronically coupled with a tryptophan side chain and bound to an azurin protein is presented. In particular, by using high-level molecular modeling, evidence is provided for how the electronic properties of the excited-state manifolds strongly depend on coupling with the environment. Indeed, only upon explicitly taking into account the protein environment can two stable triplet states of metal-to-ligand charge transfer or charge-separated nature be recovered. In addition, it is also demonstrated how the rhenium complex plus tryptophan system in an aqueous environment experiences too much flexibility, which prevents the two chromophores from being electronically coupled. This occurrence disables the formation of a charge-separated state. The successful strategy requires a multiscale approach of combining molecular dynamics and quantum chemistry. In this context, the strategy used to parameterize the force fields for the electronic triplet states of the metal complex is also presented. 相似文献
86.
87.
Structural and Dynamic Characterization of the Molecular Hub Early Region 1A (E1A) from Human Adenovirus 下载免费PDF全文
Marcela Oliveira Nogueira Michele Salvi Dr. Talita Duarte Pagani Prof. Isabella C. Felli Prof. Roberta Pierattelli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13010-13013
The small‐DNA human adenovirus encodes one of the most versatile molecular hubs, the E1A protein. This protein is essential for productive viral infection in human cells and a vast amount of biologically relevant data are available on its interactions with host proteins. Up to now, however, no high‐resolution structural and dynamic information on E1A is available despite its important biological role. Among the different spliced variants of E1A, two are expressed at high level in the early stage of infection. These are 243 and 289 residues isoforms. Herein, we present their NMR characterization, showing that they are both highly disordered, but also demonstrate a certain heterogeneous behavior in terms of structural and dynamic properties. Furthermore, we present the characterization of the isolated domain of the longer variant, known as CR3. This study opens the way to understanding at the molecular level how E1A functions. 相似文献
88.
89.
Tadaomi TAKENAWA 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2010,86(5):509-523
The mechanism by which cell and cell membrane shapes are created has long been a subject of great interest. Among the phosphoinositide-binding proteins, a group of proteins that can change the shape of membranes, in addition to the phosphoinositide-binding ability, has been found. These proteins, which contain membrane-deforming domains such as the BAR, EFC/F-BAR, and the IMD/I-BAR domains, led to inward-invaginated tubes or outward protrusions of the membrane, resulting in a variety of membrane shapes. Furthermore, these proteins not only bind to phosphoinositide, but also to the N-WASP/WAVE complex and the actin polymerization machinery, which generates a driving force to shape the membranes. 相似文献