全文获取类型
收费全文 | 3811篇 |
免费 | 461篇 |
国内免费 | 468篇 |
专业分类
化学 | 3201篇 |
晶体学 | 48篇 |
力学 | 160篇 |
综合类 | 20篇 |
数学 | 439篇 |
物理学 | 872篇 |
出版年
2024年 | 4篇 |
2023年 | 58篇 |
2022年 | 86篇 |
2021年 | 101篇 |
2020年 | 133篇 |
2019年 | 139篇 |
2018年 | 113篇 |
2017年 | 81篇 |
2016年 | 162篇 |
2015年 | 133篇 |
2014年 | 198篇 |
2013年 | 249篇 |
2012年 | 329篇 |
2011年 | 314篇 |
2010年 | 216篇 |
2009年 | 190篇 |
2008年 | 223篇 |
2007年 | 209篇 |
2006年 | 206篇 |
2005年 | 175篇 |
2004年 | 152篇 |
2003年 | 158篇 |
2002年 | 175篇 |
2001年 | 136篇 |
2000年 | 108篇 |
1999年 | 132篇 |
1998年 | 79篇 |
1997年 | 61篇 |
1996年 | 89篇 |
1995年 | 70篇 |
1994年 | 33篇 |
1993年 | 40篇 |
1992年 | 26篇 |
1991年 | 31篇 |
1990年 | 30篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1970年 | 1篇 |
1963年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有4740条查询结果,搜索用时 140 毫秒
161.
162.
A novel cellulose-based polyampholyte derivative, carboxylethyl quaternized cellulose (CEQC), was homogeneously synthesized by introducing positively charged quaternary ammonium groups and negatively charged carboxyl groups to the backbone of cellulose. The structure and dilute solution properties of CEQCs were characterized with elemental analysis, FTIR, NMR, viscometer, light scattering and zeta-potential measurement. The nitrogen content and total degree of substituent of acylamino and carboxyl groups increased with an increase of the molar ratio of acrylamide to the anhydroglucose unit of quaternized cellulose (QC). The salt-resistance of CEQC was improved remarkably by introducing opposite charged carboxyl to the QC chains. The intrinsic viscosity of the prepared polyampholytes was found to be very sensitive to the pH of the solutions. CEQC-1, the sample with relative low content of carboxyl groups, behaved as a classical cationic polyelectrolyte. However, CEQC-2 and CEQC-3, the samples with higher content of carboxyl groups, displayed typical polyampholyte behavior, and the isoelectric points (IEP) were determined to be 5.0 and 3.8 respectively. This work provided a facile method for the synthesis of novel cellulose-based polyampholytes with different IEP. 相似文献
163.
Structural Chemistry - Three new versatile azido-bridged Schiff base Copper(II) complexes, [Cu2(L1)2(μ1,1-N3)2]·2CH3OH (1), [Cu(L2)(μ1,3-N3)] n (2), and [Cu2(L3)(μ1,1-N3)2(N3)]2... 相似文献
164.
165.
Lin-Feng You Tao Wei Qian-Wang Zheng Jun-Fang Lin Li-Qiong Guo Bing-Hua Jiang Jia-Jun Huang 《Applied biochemistry and biotechnology》2018,186(4):949-959
Taxoid 10β-O-acetyl transferase (DBAT) is a key enzyme in the biosynthesis of the famous anticancer drug paclitaxel, which catalyses the formation of baccatin III from 10-deacetylbaccatin III (10-DAB). However, the activity essential residues of the enzyme are still unknown, and the acylation mechanism from its natural substrate 10-deacetylbaccatin III and acetyl CoA to baccatin III remains unclear. In this study, the homology modelling, molecular docking, site-directed mutagenesis, and kinetic parameter determination of the enzyme were carried out. The results showed that the enzyme mutant DBATH162A resulted in complete loss of enzymatic activity, suggesting that the residue histidine at 162 was essential to DBAT activity. Residues D166 and R363 which were located in the pocket of the enzyme by homology modelling and molecular docking were also important for DBAT activity through the site-directed mutations. Furthermore, four amino acid residues including S31 and D34 from motif SXXD, D372 and G376 from motif DFGWG also played important roles on acylation. This was the first report of the elucidation of the activity essential residues of DBAT, making it possible for the further structural-based re-design of the enzyme for efficient biotransformation of baccatin III and paclitaxel. 相似文献
166.
New designed DNA light switch Ruthenium complexes as DNA photocleavers and Topoisomerase I inhibitors
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xue‐Wen Liu Yang Xiao Wei‐Gen Peng Li‐Jin Zhao You‐Ming Shen Song‐Bai Zhang Ji‐Lin Lu 《应用有机金属化学》2018,32(4)
Two ruthenium complexes containing a new ligand phipz (phipz = 2‐(1,10‐phenanthroline)‐1H‐imidazo[4,5‐b]phenazine) were designed and synthesized. These complexes were found to inhibit the DNA supercoiled relaxation mediated by topoisomerase I (topo I), cleave DNA under irradiation and bind to calf thymus DNA through intercalative mode. Furthermore, complex 2 shows higher photocleavage activity, topo I inhibition activity and DNA affinity than complex 1 . Additionally, introduction of phenazine unit may be the reason that two complexes exhibit DNA ‘light switch’ behavior. The present work shows that two complexes might be potential as new DNA ‘light switches’, DNA photocleavers and topo I inhibitors. 相似文献
167.
Jianhao Wang Zhilan Zhu Wenjing Jia Lin Qiu Yufeng Chang Jie Li Luping Ma Ying You Jianpeng Wang Li Liu Jiang Xia Xiaoqian Liu Yong‐Qiang Li Pengju Jiang 《Electrophoresis》2019,40(7):1019-1026
Despite the numerous techniques developed for the studying nanoparticle and peptide interaction nowadays, sensitive and convenient assay in the process of flow, especially to simulate the self‐assembly of quantum dots (QDs) and peptide inflow in blood vessels, still remains big challenges. Here, we report a novel assay for studying the self‐assembly of QDs and peptide, based on CE using a bending capillary. We demonstrate that the semicircles numbers of the bending capillary affect the self‐assembly kinetics of CdSe/ZnS QDs and ATTO‐D3LVPRGSGP9G2H6 peptide. Moreover, benefitting from this novel assay, the effect of the position on the self‐assembly has also been realized. More importantly, we also demonstrate that this novel assay can be used for studying the stability of the QDs–peptide complex inflow. We believe that our novel assay proposed in this work could be further used as a general strategy for the studying nanoparticle–biomolecule interaction or biomolecule–biomolecule interaction. 相似文献
168.
A practical heterogeneous palladium‐catalyzed carbonylative Suzuki coupling of aryl iodides with arylboronic acids under carbon monoxide gas‐free conditions has been developed using a bidentate phosphino‐functionalized magnetic nanoparticle‐immobilized palladium(II) complex as catalyst. Formic acid was utilized as the carbon monoxide source with dicyclohexylcarbodiimide as the activator, and a wide variety of biaryl ketones were generated in moderate to high yields. The new heterogeneous palladium catalyst can be prepared via a simple procedure and can easily be separated from a reaction mixture by simply applying an external magnet and recycled up to 10 times without any loss of activity. 相似文献
169.
Iseul Jeong Chae Bin Kim Dong‐Gue Kang Kwang‐Un Jeong Se Gyu Jang Nam‐Ho You Seokhoon Ahn Dai‐Soo Lee Munju Goh 《Journal of polymer science. Part A, Polymer chemistry》2019,57(6):708-715
To address tremendous needs for developing efficiently heat dissipating materials with lightweights, a series of liquid crystalline epoxy resins (LCEs) are designed and synthesized as thermally conductive matrix. All prepared LCEs possess epoxies at the molecular side positions and cyanobiphenyl mesogenic end groups. Based on several experimental results such as differential scanning calorimetry, polarized optical microscopy, and X‐ray diffraction, it is found that the LCEs exhibited liquid crystalline mesophases. When LCE is cured with a diamine crosslinker, the cured LCE maintains the oriented LC domain formed in the uncured state, ascribing to a presence of dipole–diploe and π–π interactions between cyanobiphenyl mesogenic end groups. Due to the anisotropic molecular orientation, the cured LCE exhibits a high thermal conductivity of 0.46 W m?1 K?1, which is higher than those of commercially available crystalline or amorphous epoxy resins. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 708–715 相似文献
170.