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101.
Lele Wang Huabin Han Lijie Gu Wenjing Zhang Junwei Zhao Qilin Wang 《Chemical science》2021,12(46):15389
Simultaneous deconstructive ring-opening and skeletal reconstruction of an inert, aromatic pyridinium ring is of great importance in synthetic communities. However, research in this area is still in its infancy. Here, a skeletal re-modeling strategy was developed to transform chalcone-based pyridinium salts into structurally intriguing polycyclic isoindolines through a dearomative ring-opening/ring-closing sequence. Two distinct driving forces for the deconstruction of the pyridinium core were involved in these transformations. One was the unprecedented harnessing of the instability of in situ generated cyclic β-aminoketones, and the other was the instability of the resultant N,N-ketals. The desired isoindoline polycycles could undergo the Wittig reaction with various phosphorus ylides to achieve structural diversity and complexity. Notably, by tuning the Wittig conditions by addition of one equivalent of base, an additional bridged ring was introduced. A plausible mechanism was proposed on the basis of control experiments and theoretical calculations.A novel skeletal remodeling strategy to transform chalcone-based pyridinium salts into structurally intriguing polycyclic isoindolines was achieved through a dearomative ring-opening/ring-closing sequence. 相似文献
102.
Amita Singh Archisman Dutta Ashish Kumar Singh Manoj Trivedi Gabriele Kociok-Köhn Mohd. Muddassir Abhinav Kumar 《应用有机金属化学》2020,34(10):e5879
Five new heteroleptic complexes of Cu(I), Ag(I), and Ni(II) having formulae [Cu3(dtc)2(dppf)2]PF6 ( Cu-I ), [Cu3(dtc)2(dppe)2]PF6 ( Cu-II ), [Cu(PPh3)2(dtc)] ( Cu-III ), [Ag3(dtc)2(PPh3)2]NO3 ( Ag-I ), and [Ni(dtc)(dppf)]PF6 ( Ni-I ) (dtc = N-ethanol-N-methylferrocenyl-dithiocarbamate; dppf = 1,1′-bis(diphenylphosphino)ferrocene; dppe = 1,1′-bis(diphenylphosphino)ethane; PPh3 = tripheylphosphine) have been synthesized and characterized using elemental analysis, Fourier-transform infrared, multinuclear nuclear magnetic resonance, UV–Vis spectroscopy, and single-crystal X-ray diffraction. The single-crystal X-ray diffraction studies indicate that Ag-I forms a rare trinuclear cluster in which the geometry around the two silver centers Ag1 and Ag3 is distorted tetrahedral, whereas the third silver center Ag2 shows a distorted trigonal planar geometry. The Ni-I complex has a distorted square-planar geometry around the Ni center. In addition, a side product [Ag2{S2(dppf)2}] ( Ag-II ) was obtained during an attempt to synthesize [Ag(dppf)(dtc)], where the two Ag centers are bridged by two sulfido centers and coordinated with two phosphorus centers of the dppf ligand to give rise to a distorted tetrahedral geometry. The solid-state structures of Ag-I , Ni-I , and Ag-II are stabilized by a variety of weak interactions. The nature of these interactions has been addressed with the help of Hirshfeld surface analyses. In addition, the weak argentophilic interaction in Ag-I and Ag-II have been studied using quantum theory of atoms in molecules and natural bond orbital calculations. The electrochemical properties of the complexes have been investigated using cyclic voltammetry, where Cu-I and Cu-II exhibited two quasi-reversible waves, whereas Cu-III , Ag-I , Ag-II , and Ni-I exhibited only one quasi-reversible peak. 相似文献
103.
The upsurge interest in the development of efficient methodologies for the construction of nitrogen‐containing frameworks via the use of expedient reagents have been creating a renaissance in contemporary organic chemistry. In this perspective, tertbutyl nitrite (TBN) is an emerging building block. Due to its unique structural features, it shows differential reactivity under different reaction conditions. These diverse reactivities have resulted in the construction of a diverse array of complex N‐containing molecules. The primary objective of the present review is to bring the latest findings of TBN in terms of its applications in reactions (oxidation, diazotization, nitrosation, nitration, oximation, N‐synthon, and miscellaneous reactions) into the limelight. For simplicity and brevity, reactions in each section are explained with the mechanism of formation and selected examples are given. 相似文献
104.
Kilby Seth Jin Zhongmin Avachat Ashish Kanies Bryant Woolstenhulme Nicolas Lee Hyoung K. Graham Joseph 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(1):445-446
Journal of Radioanalytical and Nuclear Chemistry - In the original article, Equation 4 was incorrectly published. The correct equation is provided in this correction 相似文献
105.
Ashish Jain R. Pankajavalli R. Babu S. Anthonysamy 《Journal of Thermal Analysis and Calorimetry》2014,115(2):1279-1287
The standard Gibbs energies of formation of Nd2TeO6 and M6TeO12 (where M = Nd, Sm) were determined from vapour pressure measurements. The vapour pressure of TeO2(g) was measured by employing thermogravimetry-based transpiration technique. The temperature dependence of the vapour pressure of TeO2(g) over the mixtures Nd2TeO6+Nd6TeO12, generated by the incongruent vapourisation reaction, 3Nd2TeO6(s) → Nd6TeO12(s)+2TeO2(g)+O2(g), was measured in the temperature range 1,408–1,495 K. Similarly, the vapour pressure of TeO2(g) over the mixtures M6TeO12+M2O3 (where M = Nd, Sm), generated by the incongruent vapourisation reaction, M6TeO12(s) → 3M2O3(s)+TeO2(g)+½O2(g), was measured in the temperature range 1,703–1,773 and 1,633–1,753 K for Nd6TeO12(s) and Sm6TeO12(s), respectively. Enthalpy increments of M2TeO6(s) (where M = Nd, Sm) were determined by inverse drop calorimetric method in the temperature range 573–1,273 K. The thermodynamic functions, viz., heat capacity, entropy and free energy functions, were derived from the measured values of enthalpy increments. A mean value of ?2,426.2 ± 0.6 and ?2,417.9 ± 1.1 kJ mol?1 was obtained for $ \Updelta_{\text{f} } H_{298}^{\text{o}} $ (Nd2TeO6, s) and $ \Updelta_{\text{f}} H_{298}^{\text{o}} $ (Sm2TeO6, s), respectively, by combining the value of $ \Updelta_{\text{f}} G^{\text{o}} $ (Nd2TeO6, s) and $ \Updelta_{\text{f}} G^{\text{o}} $ (Sm2TeO6, s) derived from vapour pressure data and the free energy functions derived from the drop calorimetric data. 相似文献
106.
Thermally Responsive Hydrogel Blends: A General Drug Carrier Model for Controlled Drug Release 下载免费PDF全文
Chongbo Ma Ye Shi Danilo A. Pena Lele Peng Prof. Guihua Yu 《Angewandte Chemie (International ed. in English)》2015,54(25):7376-7380
Thermally responsive hydrogels have drawn significant research attention recently because of their simple use as drug carrier at human body temperature. Here we design a hybrid hydrogel that incorporates a hydrophilic polymer, polyethyleneimine (PEI), into the thermally responsive hydrogel poly(N‐isopropylacrylamide) (PNIPAm), as a general drug carrier model for controlled drug release. In this work, on one hand, PEI modifies the structure and the size of the pores in the PNIPAm hydrogel. On the other hand, PEI plays an important role in tuning the water content in the hydrogel and controls the water release rate of the hydrogel below the lower critical solution temperature (LCST), resulting in a tunable release rate of the drugs at human body temperature (37 °C). Different release rates are shown as different amounts of PEI are incorporated. PEI controls the release rate, dependent on the charge characteristics of the drugs. The hydrogel blends described in this work extend the concept of a general drug carrier for loading both positively and negatively charged drugs, as well as the controlled release effect. 相似文献
107.
108.
Lakshmi Chandrasekharan Nair Ashish Awasthi 《Numerical Methods for Partial Differential Equations》2019,35(3):1269-1289
This paper presents a numerical method based on quintic trigonometric B‐splines for solving modified Burgers' equation (MBE). Here, the MBE is first discretized in time by Crank–Nicolson scheme and the resulting scheme is solved by quintic trigonometric B‐splines. The proposed method tackles nonlinearity by using a linearization process known as quasilinearization. A rigorous analysis of the stability and convergence of the proposed method are carried out, which proves that the method is unconditionally stable and has order of convergence O(h4 + k2). Numerical results presented are very much in accordance with the exact solution, which is established by the negligible values of L2 and L∞ errors. Computational efficiency of the scheme is proved by small values of CPU time. The method furnishes results better than those obtained by using most of the existing methods for solving MBE. 相似文献
109.
110.
Jewel Hossain Ramalingam Natarajan Ashish K. Banerjee Swapan Majumdar 《Tetrahedron》2017,73(22):3139-3146
Various symmetrical and unsymmetrical isoxazoline embodied chiral macroheterocycles were synthesized from carbohydrate derived oximes. Our result shows that the mode of cycloaddition is dependent on the length and tether present in alkenyl chain of sugar moiety. Thus in some cases inter- and intramolecular cycloaddition of nitrile oxide were observed with high selectivity. The cycloadducts contains two sugar units linked via macrocycles thus they are considered as pseudo-disacharides. The stereochemistry of the newly formed chiral centers was established by 2D-NMR techniques and X-ray crystallographic studies. 相似文献