全文获取类型
收费全文 | 1753篇 |
免费 | 39篇 |
国内免费 | 16篇 |
专业分类
化学 | 1138篇 |
晶体学 | 43篇 |
力学 | 62篇 |
数学 | 202篇 |
物理学 | 363篇 |
出版年
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 23篇 |
2020年 | 29篇 |
2019年 | 26篇 |
2018年 | 29篇 |
2017年 | 28篇 |
2016年 | 48篇 |
2015年 | 30篇 |
2014年 | 47篇 |
2013年 | 94篇 |
2012年 | 102篇 |
2011年 | 106篇 |
2010年 | 60篇 |
2009年 | 57篇 |
2008年 | 85篇 |
2007年 | 98篇 |
2006年 | 91篇 |
2005年 | 83篇 |
2004年 | 56篇 |
2003年 | 63篇 |
2002年 | 47篇 |
2001年 | 29篇 |
2000年 | 22篇 |
1999年 | 27篇 |
1998年 | 24篇 |
1997年 | 20篇 |
1996年 | 30篇 |
1995年 | 28篇 |
1994年 | 22篇 |
1993年 | 27篇 |
1992年 | 22篇 |
1991年 | 17篇 |
1990年 | 24篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 16篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1972年 | 9篇 |
排序方式: 共有1808条查询结果,搜索用时 0 毫秒
51.
Archana Sivasubramaniyan Ranganathan Raja Dinesh Murugan Arul Ponnusamy Ponnuswamy Alagusundaram Kalaiselvi Patchaiah Chellammal Subbiah Subramanian Gopalan 《Research on Chemical Intermediates》2017,43(4):2471-2490
Research on Chemical Intermediates - A library of pyrazolinyltriazole hybrids (3a–l, 4a–l) was synthesized via azide–alkyne dipolar (Huisgen) cycloaddition of azidoacetyl... 相似文献
52.
Anand Mohan Yadav Nikkam Suresh Abhishek Sundaram Pravesh Painkra Ashish Kumar Raja Md Arshad 《Journal of Dispersion Science and Technology》2018,39(5):754-764
The high cost of the bridging liquid subdues the implementation and commercialization of oil agglomeration process. To overcome this problem, waste oils from different sectors were used in this present study. The performance of the process was assessed based on the responses like ash rejection and organic matter recovery. The aim of the present study was to investigate the usage of waste oils from different sectors and to optimize and analyze the behavioral pattern showcased by different variables (pulp density, oil dosage, agglomeration time and oil type) using response surface methodology (Box-Behnken design). Experimental investigation shows that the optimum pulp density, oil dosage, agglomeration time and oil type condition obtained as 3%, 15%, 15?min and waste engine oil, respectively. At optimum condition, the % ash rejection and % organic matter recovery obtained as 63.94% and 81.8%, respectively. 相似文献
53.
The thermodynamics of the complexing between hexavalent U and 1-phenyl-3-methyl-4-benzoylpyrazolone-5 (PMBP) have been studied in 70 vol% aqueous—dioxane medium at 25 and 35±0.1°C following the Bjerrum—Calvin pH titration technique, as applied by Van Uitert and Haas. The ligand is mono-protonic. The refinement of results of formation constants has been accomplished by the method of least squares treatment after an algebraic transformation. The formation of 1:1, 1:2 and 1:3 complexes has been observed, the order of stability being log K1 > log K2 > log K3. The stability invariably increases with an increase in temperature both in aqueous as well as aqueous dioxane media. The changes in ΔG0, ΔH0 and ΔS0 at 25 and 35°C for the overall equilibrium constants have also been evaluated. Uranyl complexes of PMBP are entropy stabilized, the values of enthalpy changes being positive. Other factors which affect chelate stability are briefly discussed. 相似文献
54.
55.
Katherine M. Byrd Chitra Subramanian Jacqueline Sanchez Hashim F. Motiwala Weiya Liu Prof. Mark S. Cohen Prof. Jeffrey Holzbeierlein Prof. Brian S. J. Blagg 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6921-6931
Development of heat shock protein 90 (Hsp90) C‐terminal inhibitors has emerged as an exciting strategy for the treatment of cancer. Previous efforts have focused on modifications to the natural products novobiocin and coumermycin. Moreover, variations in both the sugar and amide moieties have been extensively studied, whereas replacements for the coumarin core have received less attention. Herein, 24 cores were synthesized with varying distances and angles between the sugar and amide moieties. Compounds that exhibited good anti‐proliferative activity against multiple cancer cell lines and Hsp90 inhibitory activity, were those that placed the sugar and amide moieties between 7.7 and 12.1 Å apart along with angles of 180°. 相似文献
56.
Extraction behaviour of plutonium (IV) from nitric acid media by two long-chain aliphatic sulphoxides, namely, di-n-hexylsulphoxide
and di-n-octylsulphoxide has been investigated in the presence of several water-miscible organic solvents to study their possible
synergistic effect on metal ion extraction. Methanol, ethanol, n-and iso-propanol, dioxane, acetone as well as as acetonitrile
were used as the organic component of the mixed (polar) phase. These additives affected the extraction to varying degrees.
Thus, extractability of Pu increases 2–3 fold with increasing concentration (upto 20%) of acetonitrile, acetone, methanol
and ethanol while it decreases with increasing concentration of n-and isopropanol. At high concentration of the former, synergism
changes into antagonism. Possible reasons for such behaviour are briefly discussed. Among these organic additives, maximum
enhancement in the extraction of Pu(IV) was observed in the presence of acetonitrile. The relative increase in extraction
was found to be more at lower sulphoxide concentrations. 相似文献
57.
Telalović S Ng JF Maheswari R Ramanathan A Chuah GK Hanefeld U 《Chemical communications (Cambridge, England)》2008,(38):4631-4633
Synergy between Br?nsted acid sites and Lewis acid sites in mesoporous Al-Zr-TUD-1 was demonstrated to exist in Br?nsted acid catalysed reactions, but not in Lewis acid catalysed reactions. 相似文献
58.
pi-Conjugated macrocycles consisting of thiophenes and benzenes exhibit benzenoid features for 4npi macrocycles, whereas (4n + 2)pi macrocycles are annulenoid due to rapid interconversion between quinoid and Kekule canonical forms in the benzene units. 相似文献
59.
Role of aspartic acid in collagen structure and stability: A molecular dynamics investigation 总被引:3,自引:0,他引:3
Raman SS Parthasarathi R Subramanian V Ramasami T 《The journal of physical chemistry. B》2006,110(41):20678-20685
A molecular dynamics (MD) simulation study has been carried out to understand the stability of the triple helical collagen models. The calculations show that the presence of the aspartic acid residue in different positions leads to the local variation in the structure. Analyses of root-mean-square deviation (RMSD), radial distribution function (RDF), puckering effect, dihedral angle variation, hydrogen bond (H-bond), and conformational changes during molecular dynamics simulation reveal that the local perturbation in the sequences, increase in chain flexibility due to removal of five membered rings in the collagen by aspartic acid, change of intermolecular H-bonding pattern, and differences in the association of water are mainly influencing the nature of stabilization of collagen by aspartic acid. 相似文献
60.