全文获取类型
收费全文 | 2614篇 |
免费 | 102篇 |
国内免费 | 7篇 |
专业分类
化学 | 1811篇 |
晶体学 | 72篇 |
力学 | 75篇 |
数学 | 153篇 |
物理学 | 612篇 |
出版年
2024年 | 8篇 |
2023年 | 35篇 |
2022年 | 64篇 |
2021年 | 82篇 |
2020年 | 95篇 |
2019年 | 123篇 |
2018年 | 111篇 |
2017年 | 76篇 |
2016年 | 110篇 |
2015年 | 83篇 |
2014年 | 151篇 |
2013年 | 228篇 |
2012年 | 172篇 |
2011年 | 171篇 |
2010年 | 102篇 |
2009年 | 98篇 |
2008年 | 124篇 |
2007年 | 90篇 |
2006年 | 64篇 |
2005年 | 57篇 |
2004年 | 62篇 |
2003年 | 47篇 |
2002年 | 47篇 |
2001年 | 46篇 |
2000年 | 55篇 |
1999年 | 69篇 |
1998年 | 20篇 |
1997年 | 17篇 |
1996年 | 18篇 |
1995年 | 18篇 |
1994年 | 19篇 |
1993年 | 16篇 |
1992年 | 17篇 |
1991年 | 17篇 |
1990年 | 14篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 16篇 |
1985年 | 21篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1977年 | 14篇 |
1976年 | 7篇 |
1974年 | 7篇 |
1973年 | 8篇 |
排序方式: 共有2723条查询结果,搜索用时 140 毫秒
51.
52.
Baldev Singh Manhas Narinder Kaur Ajaib Singh Dhindsa 《Transition Metal Chemistry》1992,17(4):287-291
New copper(II) acetate complexes with the saturated diheterocyclic bases (L-L): piperazine, 1-methylpiperazine, and 1,4-dimethylpiperazine
and their monohydrochlorides, have been prepared and characterised by physico-chemical and spectroscopic methods. They are
magnetically dilute and antiferromagnetic, with stoichiometries of the type Cu(OAc)2(B)n(B=L-L or L-LHCl and n=2, 1 or 0.5). 相似文献
53.
Singh G. Kapoor I. P. S. Srivastava J. Kaur J. 《Journal of Thermal Analysis and Calorimetry》2002,69(2):681-691
Three dimethylanilinium sulfates (DMAS) have been prepared and characterised by elemental and spectral studies. Thermal decomposition of these salts has been studied by TG and simultaneous TG-DTG technique and kinetic parameters were evaluated from both dynamic and isothermal TG data using mechanism based kinetic equations. The thermal decomposition pathways have also been suggested and it has been found that DMAS salts give dimethyl aminobenzenesulfonic acids (DMABSA) via solid state reaction. The primary step in the thermal decomposition involves proton transfer followed by sulfonation.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
54.
The kinetics of thermal reactions of the photochemically-generated species [W(CN)7OH]4− and [W(CN)6–(CNH)(H2O)]2− with 5–nitro-1,10–phenanthroline
(nitrophen) in basic and acidic media, respectively, were studied in buffer solutions at pH 4.2–10.6 and ionic strength 7.5×10−2kg−1
at 20°C. The quantum yield for the formation of the photoproduct was calculated and found to depend upon pH and the ligand
and [W(CN)8]4− concentrations. The rate constants and quantum yields were less compared with 1,10–phenanthroline due to the
electron-withdrawing inductive effect of the nitro group in nitrophen, which makes the latter a weaker ligand. The pseudo-first-order
rate constant and quantum yield values in acidic media are higher than in basic media and the mechanisms of the photochemical
substitution are different in the two media.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
55.
Chu I Liu F Soares A Kumari P Nomeir AA 《Rapid communications in mass spectrometry : RCM》2002,16(15):1501-1505
Rapid, generic gradient liquid chromatography/tandem mass spectrometry (LC/MS/MS) assays, designed to accelerate sample analyses, have been developed to keep pace with the productivity of advanced synthetic procedures. In this study, LC/MS/MS was combined with an in vitro, cell-based, blood-brain barrier (BBB) model to evaluate the potential of new chemical entities (NCEs) to cross the BBB. This in vitro assay provides the permeability of discovery compounds across a monolayer of a primary culture of bovine brain microvessel endothelial cells in a fraction of the time that is required for in vivo studies (brain/plasma concentrations), using only 2 mg of the compound. The results are consistent with in vivo brain/plasma concentration ratio data. 相似文献
56.
57.
Vineet Aniya Alka Kumari Rupesh Reddy B. Satyavathi 《Journal of solution chemistry》2017,46(6):1177-1201
2-Methylpropan-2-ol, an important fine chemical, may be dehydrated during extractive distillation with glycols as entrainer. Experimental isobaric phase equilibrium studies were carried out on binary mixtures of 2-methylpropan-2-ol with ethane-1,2-diol, as an entrainer, at the local atmospheric pressure of 94.99 kPa and at sub-atmospheric pressures of 19.99, 39.99, 59.99, 78.79 kPa using a Sweitoslawski-type ebulliometer. The Wilson and NRTL activity coefficient models were used to correlate the experimental results and the binary interaction parameters were obtained using the Generalized Reduced Gradient optimization technique. UNIFAC was also used to predict the deviations in bubble temperatures. Moreover, the variation in density, refractive index values and other derived properties (excess molar volumes, partial molar volumes and deviations in molar refractivity) were explored at 303.15, 313.15, 323.15 and 333.15 K to understand the shift of equilibrium with the variation in the mixture composition for the conformational state of the molecules. The Redlich–Kister polynomial equation was used to correlate the excess molar volumes and deviations from molar refractivity. Different theoretical mixing rules (Lorentz–Lorenz, Wiener, Heller, Gladstone–Dale and Arago–Biot) are investigated and reported in terms of average percentage deviation. Furthermore, the Prigogine–Flory–Patterson theory was used to predict the trend of the dependence of excess molar volumes on composition for the present system. 相似文献
58.
Meena Kumari Upendra Kumar Singh Abbul Bashar Khan Maqsood Ahmad Malik 《Journal of Dispersion Science and Technology》2018,39(10):1462-1468
The effect of bovine serum albumin on the surface properties of IL-type gemini surfactant ([C10-4-C10im]Br2), have been investigated by surface tension method. The critical micelle concentration (CMC) as a function of BSA concentrations at various temperatures was investigated. The CMC of [C10-4-C10im]Br2 increases with increasing the concentration of BSA as well as the temperature of the system. The interfacial parameters viz; maximum surface excess concentration (Γmax), the minimum area per molecule (Amin), and surface pressure at CMC (Πcmc) were calculated. In addition, thermodynamic parameters of adsorption and micellization were evaluated by using surface tension data. The results indicated that the binding of [C10-4-C10im]Br2 to BSA is spontaneous and exothermic in nature. The process is entropy driven and hydrophobic interactions are the major driving forces. 相似文献
59.
Navkiran Kaur Mansimran Khokhar Vaibhav Jain P. V. Bharatam Rajat Sandhir Rupinder Tewari 《Applied biochemistry and biotechnology》2013,171(2):417-436
Emergence of the multidrug-resistant pathogens has rendered the current therapies ineffective thereby, resulting in the need for new drugs and drug targets. The accumulating protein sequence data has initiated a drift from classical drug discovery protocols to structure-based drug designing. In the present study, in silico subtractive genomics approach was implemented to find a set of potential drug targets present in an opportunist bacterial pathogen, Acinetobacter baumannii (A. baumannii). Out of the 43 targets identified, further studies for protein model building and lead-inhibitor identification were carried out on two cell-essential targets, MurA and MurB enzymes (of A. baumannii designated as MurAAb and MurBAb) involved in the peptidoglycan biosynthesis pathway of bacteria. The homology model built for each of them was further refined and validated using various available programs like PROCHECK, Errat, ProSA energy plots, etc. Compounds showing activity against MurA and MurB enzymes of other organisms were collected from the literature and were docked into the active site of MurAAb and MurBAb enzymes. Three inhibitors namely, T6361, carbidopa, and aesculin, showed maximum Glide score, hydrogen bonding interactions with the key amino acid residues of both the enzymes and acceptable ADME properties. Furthermore, molecular dynamics simulation studies on MurAAb–T6361 and MurBAb–T6361 complexes suggested that the ligand has a high binding affinity with both the enzymes and the hydrogen bonding with the key residues were stable in the dynamic condition also. Therefore, these ligands have been propsed as dual inhibitors and promising lead compounds for the drug design against MurAAb and MurBAb enzymes. 相似文献
60.
Jatinder Kaur Atul Bhardwaj Frank Wuest 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(10):3326-3337
Live-cell imaging with fluorescent probes is an essential tool in chemical biology to visualize the dynamics of biological processes in real-time. Intracellular disease biomarker imaging remains a formidable challenge due to the intrinsic limitations of conventional fluorescent probes and the complex nature of cells. This work reports the in cellulo assembly of a fluorescent probe to image cyclooxygenase-2 (COX-2). We developed celecoxib-azide derivative 14 , possessing favorable biophysical properties and excellent COX-2 selectivity profile. In cellulo strain-promoted fluorogenic click chemistry of COX-2-engaged compound 14 with non/weakly-fluorescent compounds 11 and 17 formed fluorescent probes 15 and 18 for the detection of COX-2 in living cells. Competitive binding studies, biophysical, and comprehensive computational analyses were used to describe protein-ligand interactions. The reported new chemical toolbox enables precise visualization and tracking of COX-2 in live cells with superior sensitivity in the visible range. 相似文献