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排序方式: 共有841条查询结果,搜索用时 15 毫秒
741.
Madhuri A. Phadke Deepak A. Musale Sudhir S. Kulkarni Sandeep K. Karode 《Journal of Polymer Science.Polymer Physics》2005,43(15):2061-2073
Fourier transform infrared spectroscopy was used to study the interactions among LiCl, ZnCl2, and AlCl3 with N,N‐dimethylformamide (DMF) and poly(acrylonitrile) (PAN). It was observed that all three salts complex with DMF as well as PAN. The strength of the cation interaction with the >C?O oxygen of DMF was found to be higher than that with the ? CN group of PAN. The >C?O stretching frequency of DMF with ZnCl2 was red shifted, indicating stronger complex formation compared with other two cations. With the addition of salt, the salt–DMF pseudo solvent was found to become a θ solvent for PAN compared with neat DMF. This change in PAN solvation power was primarily the result of DMF–salt complexation. As a result of the complexation, Mark‐Houwink constant a, was found to reduce from 0.75 (for pure DMF) to ~0.6 for DMF–salt solvents, indicating decreased PAN chain expansion. Comparison of intrinsic viscosity [η] values indicated that addition of salts to PAN–DMF solutions resulted in: (i) decrease in the DMF solvation power, which causes less expanded polymer coils, and (ii) increased interpolymer chain entanglements via salt‐promoted chain association. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2061–2073, 2005 相似文献
742.
743.
JPC – Journal of Planar Chromatography – Modern TLC - A simple and sensitive method for separation and quantitative determination of antidiabetic drugs in pharmaceutical preparations... 相似文献
744.
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
745.
Madhukar NAVGIRE Ajeet YELWANDE Deepak TAYDE Balasaheb ARBAD Machhindra LANDE 《催化学报》2012,(2):261-266
A MoO3-TiO2 nanocrystalline composite material was prepared by a simple solgel method.The synthesized material was charac-terized by X-ray diffraction,scanning electron microscopy with an electron dispersion spectroscopy,transmission electron microscopy,and Fourier transform infrared spectroscopy.Melanoidin is a dark brown pigment found in wastewater from the sugar industry and it pollutes water.This polluted water is generally referred to as molasses and it undergoes fermentation and is solely responsible for water,soil,and air pollution.The synthesized catalytic material was found to be effective in degrading molasses under UV-visible radiation.Analysis of treated and untreated molasses was carried out by measuring its color,chemical oxygen demand,biological oxygen demand,pH,and total dissolved solid.Results from these analyses indicate the effective photodegradation of the molasses.This methodology has several advantages such as high photocatalytic activity,non-toxicity,cleanliness,and reusability of the catalytic material. 相似文献
746.
Bob Boyd Gareth Brenton Eddie Clayton Jonathan Curtis R. M. Elliott G. A. Errock B. N. Green R. H. Bateman Simon J. Gaskell Iwan Griffiths Zdenek Herman Philip Jonathan Rich Kondrat Mila Laušević Chris Lock Deepak Mathur John F. J. Todd Károly Vékey 《Journal of mass spectrometry : JMS》2016,51(6):385-395
747.
748.
In this work, we examine the strength of various types of individual hydrogen bond (HB) in mixed methanol-water MnWm, (n+m=2 to 7) clusters, with an aim to understand the relative order of their strength, using our recently proposed molecular tailoring-based approach (MTA). Among all the types of HB, it is observed that the OM−H…OW HBs are the strongest (6.9 to 12.4 kcal mol−1). The next ones are OM−H…OM HBs (6.5 to 11.6 kcal mol−1). The OW−H…OW (0.2 to 10.9 kcal mol−1) and OW−H…OM HBs (0.3 to 10.3 kcal mol−1) are the weakest ones. This energetic ordering of HBs is seen to be different from the respective HB energies in the dimer i. e., OM−H…OM (5.0 to 6.0 kcal mol−1)>OW−H…OM (1.5 to 6.0 kcal mol−1)>OM−H…OW (3.8 to 5.6 kcal mol−1)>OW−H…OW (1.2 to 5.0 kcal mol−1). The plausible reason for the difference in the HB energy ordering may be attributed to the increase or decrease in HB strengths due to the formation of cooperative or anti-cooperative HB networks. For instance, the cooperativity contribution towards the different types of HB follows: OM−H…OW (2.4 to 8.6 kcal mol−1)>OM−H…OM (1.3 to 6.3 kcal mol−1)>OW−H…OW (−1.0 to 6.5 kcal mol−1)>OW−H…OM (−1.2 to 5.3 kcal mol−1). This ordering of cooperativity contribution is similar to the HB energy ordering obtained by the MTA-based method. It is emphasized here that, the interplay between the cooperative and anti-cooperative contributions are indispensable for the correct energetic ordering of these HBs. 相似文献
749.
Divya Chopra Marianna Kontopoulou Dimitris Vlassopoulos Savvas G. Hatzikiriakos 《Rheologica Acta》2002,41(1-2):10-24
We investigated the thermo- rheological behavior of high glass transition, high molecular weight and small dynamic asymmetry
blends of poly(styrene-co-maleic anhydride) (SMA) and poly (methyl methacrylate) (PMMA) with varying amounts of maleic anhydride (MA) content, namely
8 wt%, 14 wt% and 32 wt%, in the SMA component. The phase separation (binodal) temperature of each blend was determined rheologically
using a combination of dynamic frequency and temperature sweeps in parallel plate geometry; it was marked by a change in slope
of the elastic modulus and the occurrence of a peak in tan δ in temperature sweeps. Failure of the time-temperature superposition
principle and observation of two peaks in the Cole-Cole plots corroborated these findings. The blends displayed lower critical
solution temperature (LCST) behavior with the critical temperatures exhibiting a non-monotonic dependence on the MA content.
From rheological and thermal measurements it was concluded that SMA/PMMA blends containing 14% MA were more miscible than
those containing 8% or 32% MA, a finding attributed to the compositional dependence of the interplay between SMA-SMA and SMA-PMMA
interactions in the different samples. MA also influenced the dynamic asymmetry and pretransitional concentration fluctuations.
The phase diagrams corresponding to each blend were modeled using a two-parameter temperature dependent interaction parameter,
based on the concept of generalized Gibbs free energy of mixing. The fitted values of interaction parameter were in good agreement
with values calculated explicitly using the Flory-Huggins theory.
Received: 16 February 2001 Accepted: 11 July 2001 相似文献
750.
Indrajeet J. Barve Chan‐Yu Chen Deepak B. Salunke Prof. Wen‐Sheng Chung Prof. Chung‐Ming Sun 《化学:亚洲杂志》2012,7(7):1684-1690
The present article describes the design and synthesis of new biprivileged molecular scaffolds with diverse structural features. Commercially available, simple heterocyclic building blocks such as 4‐fluoro‐3‐nitrobenzoic acid, 2‐chloro‐3‐nitrobenzoic acid, and indoline were utilized for the synthesis of the novel heterocycles. Pictet–Spengler‐type condensation was used as a key step to construct tetracyclic indolo‐benzodiazepines and indolo‐quinoxalines linked with substituted benzimidazoles. Analysis of single crystals of representative compounds showed that these molecular skeletons have the potential to present various substituents with distinct three‐dimensional orientations. 相似文献