全文获取类型
收费全文 | 2288篇 |
免费 | 281篇 |
国内免费 | 135篇 |
专业分类
化学 | 1581篇 |
晶体学 | 3篇 |
力学 | 178篇 |
综合类 | 47篇 |
数学 | 225篇 |
物理学 | 670篇 |
出版年
2024年 | 8篇 |
2023年 | 44篇 |
2022年 | 154篇 |
2021年 | 155篇 |
2020年 | 121篇 |
2019年 | 105篇 |
2018年 | 59篇 |
2017年 | 96篇 |
2016年 | 120篇 |
2015年 | 111篇 |
2014年 | 132篇 |
2013年 | 153篇 |
2012年 | 105篇 |
2011年 | 125篇 |
2010年 | 118篇 |
2009年 | 129篇 |
2008年 | 103篇 |
2007年 | 105篇 |
2006年 | 129篇 |
2005年 | 110篇 |
2004年 | 93篇 |
2003年 | 84篇 |
2002年 | 59篇 |
2001年 | 46篇 |
2000年 | 51篇 |
1999年 | 34篇 |
1998年 | 24篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有2704条查询结果,搜索用时 15 毫秒
71.
O. Takahashi Y. Masuda A. Muroya T. Furuya 《SAR and QSAR in environmental research》2013,24(5-6):547-558
In general, the docking scoring tends to have a size dependence related to the ranking of compounds. In this paper, we describe a novel method of parameter optimization for docking scores which reduce the size dependence and can efficiently discriminate active compounds from chemical databases. This method is based on a simplified theoretical model of docking scores which enables us to utilize large amounts of data of known active and inactive compounds for a particular target without requiring large computational resources or a complicated procedure. This method is useful for making scoring functions for the identification of novel scaffolds using the knowledge of active compounds for a particular target or a customized scoring function for an interesting family of drug targets. 相似文献
72.
A.K. Gupta S.S. Bhunia V.M. Balaramnavar 《SAR and QSAR in environmental research》2013,24(3-4):239-263
A pharmacophore model has been developed using diverse classes of epidermal growth factor receptor (EGFR) tyrosine kinase (TK) inhibitors useful in the treatment of human tumours. Among the top 10 generated hypotheses, the second hypothesis, with one hydrogen bond acceptor, one ring aromatic and three hydrophobic features, was found to be the best on the basis of Cat Scramble validation as well as test set prediction (r training?=?0.89, r test?=?0.82). The model also maps well to the external test set molecules as well as clinically active molecules and corroborates the docking studies. Finally, 10 hits were identified as potential leads after virtual screening of ZINC database for EGFR TK inhibition. The study may facilitate the designing and discovery of novel EGFR TK inhibitors. 相似文献
73.
Ayoung Pyo Sudeok Kim Manian Rajesh Kumar Aleum Byeun Min Sik Eom Min Su Han Sunwoo Lee 《Tetrahedron letters》2013
Paraformaldehyde was employed as a hydride source in the palladium-catalyzed hydrodehalogenation of aryl iodides and bromides. High throughput screening using a paper-based colorimetric iodide sensor (PBCIS) showed that Pd(OAc)2 and Cs2CO3 were the best catalyst and base, respectively. Aryl iodides and bromides were hydrodehalogenated to produce the reduced arenes using Pd(OAc)2 and Pd(PPh3)4 catalyst. This catalytic system showed good functional group tolerance. In addition, it was found that paraformaldehyde is the hydride source and the reducing agent for the formation of palladium nanoparticles. 相似文献
74.
Pretransitional fluctuations in the isotropic phase of liquid crystalline and non‐liquid crystalline alkyl cyanobiphenyls have been investigated using light scattering and magnetic birefringence measurements. We find evidence for a virtual isotropic‐nematic phase transition in short‐chain alkyl cyanobiphenyls with no observable nematic phase. The measured temperature dependence of fluctuations is well‐described by mean‐field theory. Virtual phase transition temperatures extrapolated from separate light scattering and magnetic birefringence experiments are in good agreement. Landau–de Gennes model parameters for the compounds investigated are calculated from the experimental results. 相似文献
75.
Dr. Mark Feyand Milan Köppen Prof. Dr. Gernot Friedrichs Prof. Dr. Norbert Stock 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(37):12537-12546
A systematic investigation of the systems Bi3+/carboxylic acid/HNO3 for the tri‐ and tetracarboxylic acids pyromellitic acid (H4Pyr), trimellitic acid (H3Tri) and trimesic acid (H3BTC) acid led to the discovery of five new bismuth carboxylates. Structural characterisation allowed the influence of the linker geometry and the Bi3+:linker molar ratio in the starting solution on the crystal structure to be determined. The crystallisation of three selected compounds was investigated by in situ energy‐dispersive X‐ray diffraction. Three new crystalline intermediates were observed within minutes, and two of them could be isolated by quenching of the reaction mixture. Their crystal structures were determined from laboratory and synchrotron X‐ray powder diffraction data and allowed a possible reaction pathway to be established. In depth characterisation of the luminescence properties of the three bismuth pyromellate compounds was carried out. Fluorescence and phosphorescence could be assigned to (mainly) ligand‐ and metal‐based transitions. The polymorphs of Bi(HPyr) exhibit different luminescence properties, although their structures are very similar. Surprisingly, doping of the three host structures with Eu3+ and Tb3+ ions was only successful for one of the polymorphs. 相似文献
76.
77.
A method for enantiodiscrimination of α-chiral aldehydes is reported. The method utilizes circular dichroism (CD) spectroscopy and a sensing ensemble composed of 2-(1-methylhydrazinyl) pyridine (1) and Fe(II)(TfO)2. Aldehydes react rapidly with hydrazine (1) to form chiral imines, which form complexes with Fe(II). By monitoring the CD bands above 320 nm, one can determine the enantiomeric excess (ee) values of α-chiral aldehydes with an average absolute error of ±5%. The analysis was fast, and thus can have potential applications in high-throughput screening (HTS) of catalytic asymmetric induction. 相似文献
78.
利用三维(3D)细胞反应器模拟体内微环境,建立了一种与肿瘤细胞作用的活性分子的筛选和分析方法.利用药物与三维细胞反应器中活肿瘤细胞和固化肿瘤细胞分别作用后的HPLC生物指纹谱峰面积之间有无显著性差异,建立了与细胞结合的活性成分的筛选识别模型.已知抗肿瘤药物紫杉醇和白藜声醇的谱峰均具有显著性差异,而非抗肿瘤药物酮洛芬和青霉素G的谱峰均没有显著性差异,证明利用该模型筛选识别与细胞结合的活性成分是可行的.此外,应用该模型从中草药桃儿七提取物中筛选出了7种可作用于Lovo细胞的活性成分.此研究提供了一种模拟体内微环境下与肿瘤细胞作用的活性成分的筛选和分析方法,在药物发现环节,特别是中草药活性成分研究中具有潜在的应用价值. 相似文献
79.
FAN RuoJing ZHANG Fang WANG HaoYang ZHANG Li ZHANG Jing ZHANG Ying YU ChongTian GUO YinLong 《中国科学:化学(英文版)》2014,57(5):669-677
The widespread use of pesticides induces heavy adverse effects on human health,especially for the pregnant women and the newborns.In this study,a screening method has been developed for the determination of multi-pesticides in maternal and umbilical cord sera.All pesticides in sera were collected using solid phase extraction(SPE),and analyzed by gas chromatography-quadrupole time of flight mass spectrometry(GC-QTOF MS).To set up the quality criteria,a database of 50 pesticides was created and the accurate masses of 3 up to 5 representative ions with their intensity ratios were included for each pesticide.In addition,a novel"identification points"(IPs)system relying on the accurate MS1 and MS2 spectra was used to interpret the data for each suspected pesticide.The methodology was then applied to a pair of maternal and umbilical cord sera.A total of six pesticide residues were screened out successfully.In conclusion,GC-QTOF MS combined with an accurate mass database seemed to be one of the most efficient tools for systematic pesticide analysis. 相似文献
80.
Dr. Jinsuo Gao Xueying Zhang Dr. Shutao Xu Dr. Jian Liu Prof. Feng Tan Prof. Xinyong Li Prof. Zhenping Qu Prof. Yaobin Zhang Prof. Xie Quan 《化学:亚洲杂志》2014,9(3):908-914
Pharmaceutical antibiotics, as emerging contaminants, are usually composed of several functional groups that endow them with the ability to interact with adsorbents through different interactions. This makes the preparation of adsorbents tedious and time‐consuming to screen appropriate functionalized materials. Herein, we describe the synthesis of clickable SBA‐15 and demonstrate its feasibility as a screening material for the adsorption of antibiotics based on similar adsorption trends on materials with similar functional groups obtained by a click reaction and cocondensation/grafting methods. 相似文献