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921.
A new and highly efficient methodology for the construction of synthetically important highly O-functionalized enantiopure 2,3,4-trisubstituted tetrahydrofurans with three contiguous stereocenters is reported. 相似文献
922.
Datar A Balakrishnan K Yang X Zuo X Huang J Oitker R Yen M Zhao J Tiede DM Zang L 《The journal of physical chemistry. B》2006,110(25):12327-12332
Linearly polarized emission has been observed for the nanobelts fabricated from a perylene diimide molecule through both solution-based and surface-supported self-assembling. The measurement of polarized emission was performed over single nanobelts with use of a near-field scanning optical microscope (NSOM) adapted with emission polarization (by putting a planar polarizer before the detector). Rotating the emission polarizer (from 0 degrees to 180 degrees) changed the emission intensity in a way depending on the relative angle between the long axis of the belt and the polarizer with a minimum of intensity detected at ca. 78 degrees, which is indicative of the tilted stacking of molecules along the belt direction. 相似文献
923.
Ma Q Chakraborty D Faglioni F Muller RP Goddard WA Harris T Campbell C Tang Y 《The journal of physical chemistry. A》2006,110(6):2246-2252
The current work utilizes the ab initio density functional theory (DFT) to develop a molecular level of the mechanistic understanding on the phenol alkylation in the presence of a cation-exchange resin catalyst, Amberlyst-15. The catalyst is modeled with the benzene sulfonic acid, and the effect of this acid on olefins such as isopropene (i-Pr) and tributene (t-Bu) in a phenol solution mimics the experimental condition. A neutral-pathway mechanism is established to account for early-stage high concentration of the phenolic ether observed in experiments. The mechanism involves an exothermic reaction between olefin and the benzene sulfonic acid to form ester followed by three reaction pathways leading to direct O-alkylation, o-C-alkylation, and p-C-alkylation. Our calculations conclude that O-alkylation to form the phenolic ether is the most energetically favorable in the neutral condition. An ionic rearrangement mechanism describes intramolecular migrations of the alkyl group from the phenolic ether to form C-alkylphenols, while the positively charged protonation significantly lowers transition barriers for these migrations. The ionic rearrangement mechanism accounts for high yields of o-C-alkylphenol and p-C-alkylphenol. Competition between the H atom and the alkyl R group at the substitutive site of the protonated ortho configuration is found to be the determining factor to the ortho/para ratio of C-alkylation products. 相似文献
924.
An important problem that arises in the area of grid computing is one of optimally assigning jobs to resources to achieve a business objective. In the grid computing area, however, such scheduling has mostly been done from the perspective of maximizing the utilization of resources. As this form of computing proliferates, the business aspects will become crucial for the overall success of the technology. Hence, we discuss the grid scheduling problem from a business perspective. We show that this problem is not only strongly NP-hard, but it is also non-approximable. Therefore, we propose heuristics for different variants of the problem and show that these heuristics provide near-optimal solution for a wide variety of problem instances. We show that the execution times of proposed heuristics are very low, and hence, they are suitable for solving problems in real-time. We also present several managerial implications and compare the performance of two widely used models in the real-time scheduling of grid computing. 相似文献
925.
S. Acharya S. Sutradhar J. Mandal K. Mukhopadhyay A.K. Deb P.K. Chakrabarti 《Journal of magnetism and magnetic materials》2012
Nanocrystalline BiFeO3 and rare earth ion doped BiFeO3 (Bi0.9R0.1FeO3, R=Er and Tm) were prepared by sol–gel method. Rietveld analysis of the X-ray diffractograms of the samples revealed that small amount of impurity phase of Bi2Fe4O9 was formed together with the desired phase. In the thermal variation of magnetic mass susceptibility (χm) of the samples, one sharp transition below TM (TM∼100 K, 50 K and 30 K for BiFeO3, Bi0.9Er0.1FeO3 and Bi0.9Tm0.1FeO3, respectively) was observed, which clearly hint the change of the domination of the ferromagnetic exchange interaction over the usual antiferromagnetic exchange interaction. Also, static magnetization (M) and susceptibility of each doped sample have been drastically enhanced compared to that of BiFeO3. The values of χm and M measured at different temperatures confirmed that the magnetic behavior of the doped systems has been dominated by the paramagnetic/ferromagnetic clusters below ∼TM. Another phase transition were observed in the χm vs. T curve of the samples at relatively higher temperature TB (∼260 K for BiFeO3, ∼220 K for Bi0.9Er0.1FeO3 and ∼180 K for Bi0.9Tm0.1FeO3), which may be attributed to the charge ordering transition. Ferroelectric hysteresis loops of the samples observed at 100 Hz confirmed the presence of ferroelectric ordering of the samples. Measured values of dielectric constants at 1 kHz of each sample in presence and absence of magnetic field confirmed a substantial magnetoelectric coupling of all the samples. 相似文献
926.
Europium doped glass-ceramics containing BaF2 nano-crystals have been prepared by using the controlled crystallization of melt-quenched glasses. X-ray diffraction and
transmission electron microscopy have confirmed the presence of cubic BaF2 nano-crystalline phase in glass matrix in the ceramized samples. Incorporation of rare earth ions into the formed crystalline
phase having low phonon energy of 346 cm−1 has been demonstrated from the emission spectra of Eu3+ ions showing the transitions from upper excitation states 5DJ (J = 1, 2, and 3) to ground states for the glass-ceramics samples. The presence of divalent europium ions in glass and glass-ceramics
samples is confirmed from the dominant blue emission corresponding to its 5d-4f transition under an excitation of 300 nm. Increase in the reduction of trivalent europium (Eu3+) ions to divalent (Eu2+) with the extent of ceramization is explained by charge compensation model based on substitution defect mechanisms. Further,
the phenomenon of energy transfer from Eu2+ to Eu3+ ion by radiative trapping or re-absorption is evidenced which increases with the degree of ceramization. For the first time,
the reduction of Eu3+ to Eu2+ under normal air atmospheric condition has been observed in a BaF2 containing oxyfluoride glass-ceramics system. 相似文献
927.
Katharigatta N. Venugopala Pottathil Shinu Christophe Tratrat Pran Kishore Deb Raquel M. Gleiser Sandeep Chandrashekharappa Deepak Chopra Mahesh Attimarad Anroop B. Nair Nagaraja Sreeharsha Fawzi M. Mahomoodally Michelyne Haroun Mahmoud Kandeel Syed Mohammed Basheeruddin Asdaq Viresh Mohanlall Nizar A. Al-Shari Mohamed A. Morsy 《Molecules (Basel, Switzerland)》2022,27(9)
Alteration of insect growth regulators by the action of inhibitors is becoming an attractive strategy to combat disease-transmitting insects. In the present study, we investigated the larvicidal effect of 1,2,3-triazolyl-pyrimidinone derivatives against the larvae of the mosquito Anopheles arabiensis, a vector of malaria. All compounds demonstrated insecticidal activity against mosquito larvae in a dose-dependent fashion. A preliminary study of the structure–activity relationship indicated that the electron-withdrawing substituent in the para position of the 4-phenyl-pyrimidinone moiety enhanced the molecules’ potency. A docking study of these derivatives revealed favorable binding affinity for the sterol carrier protein-2 receptor, a protein present in the intestine of the mosquito larvae. Being effective insecticides against the malaria-transmitting Anopheles arabiensis, 1,2,3-triazole-based pyrimidinones represent a starting point to develop novel inhibitors of insect growth regulators. 相似文献
928.
Mohammed F. Arshad Aftab Alam Abdullah Ayed Alshammari Mohammed Bader Alhazza Ibrahim Mohammed Alzimam Md Anish Alam Gulam Mustafa Md Salahuddin Ansari Abdulelah M. Alotaibi Abdullah A. Alotaibi Suresh Kumar Syed Mohammed Basheeruddin Asdaq Mohd. Imran Pran Kishore Deb Katharigatta N. Venugopala Shahamah Jomah 《Molecules (Basel, Switzerland)》2022,27(13)
929.
Bhawna Kaushik Pooja Rana Deepti Rawat Kanika Solanki Pooja Rana Shallu Sachdeva Dhanaji R. Naikwadi Ankush V. Biradar Rakesh K. Sharma 《应用有机金属化学》2023,37(1):e6936
Construction of an effective heterojunction for unimpeded flow of photogenerated charges and their prolonged separation is imperative for environmental photocatalysis. Herein, we have designed an efficient magnetic ZnO/BiVO4 type-II heterostructure, which was employed for proficient degradation of persistent methyl violet dye with an efficiency of 97.6% in 90 min and a hazardous organic pollutant, namely, bisphenol A. UV-DRS and photoluminescence studies demonstrated that the fabricated nanocomposite exhibited effective light absorption and prolonged charge separation, thereby resulting in high photocatalytic efficacy under visible light irradiation. The efficacy of developed magnetic ZnO/BiVO4 was also compared with pristine BiVO4 and undoped magnetic ZnO, which indicated that the constructed heterostructure displayed approximately threefold and sixfold activity in contrast with bare BiVO4 and undoped magnetic ZnO nanoparticles, respectively. Radical trapping studies, ESR analysis along with GC-MS analysis were conducted to elucidate the mechanistic pathway during the photodegradation process. This work provides a rational technical approach and research ideas for photocatalytic degradation of harmful organic pollutants in an environment-friendly manner by employing energy-efficient LEDs. Besides, good recyclability of catalyst makes it a promising candidate for large-scale applications. 相似文献
930.
In this work, the anion-responsive conduct of a Ru(II)-bipyridine complex incorporating pyrazolyl-bis (benzimidazole) ligand is thoroughly investigated in acetonitrile and water via absorption and emission spectroscopy as well as by square-wave voltammetry (SWV). Substantial alteration of the photo-redox behavior of the complex is observed in the presence of the selected anions. The free form of the complex exhibits emission indicating the “on-state”, while inclusion of anions leads to quenching of emission and represents the “off-state”. The restoration of the initial state of the complex is feasible in the presence of acid and the process is reversible and can be recycled. In essence, the complex functions as anion- and acid-responsive molecular switches. Additionally, we applied herein neural network based deep learning methodologies, viz. Artificial Neural Networks (ANNs) and Adaptive Neuro-Fuzzy Inference System (ANFIS)} for thorough analysis and fully understand the multi-channel anion sensing behavior of the complex. 相似文献