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991.
Reactive Oxygen Species (ROS) are an important part of the normal cell growth cycle and play essential roles in many biological functions. Many techniques have been developed to detect and measure the amount of ROS present in cells. These techniques include spectrophotometry, high performance liquid chromatography (HPLC), capillary electrophoresis with laser-induced-fluorescence detector (CE-LIF) and capillary electrophoresis-on-a-chip with LIF. As ROS has a short half-life outside of the cell, various fluorescent probes, such as dihydrorhodamine 123 (DHR 123), that are membrane permeable have been used in the detection of intracellular ROS. In this paper, micellar electrokinetic capillary chromatography (MEKC) was coupled with LIF detector. Fluorescent probe, 3′-(p-aminophenyl)-fluorescein (APF), was used to detect specific ROS in Chinese Hamster Ovary (CHO) suspension cells as well as attached mouse bone marrow-derived dendritic cells (BMDCs). Separation buffer composition was optimized at a concentration of 25?mM tetraborate buffer with 50?mM sodium dodecyl sulfate at pH 9.3 and lysis of the cells was done successfully with a buffer of 70% ethanol and 0.1mM sodium dodecyl sulfate using a cell amount of 1?×?107. ROS in cells was successfully analyzed by MEKC-LIF method developed, with acceptable RSD for time at 1.54% and area at 2.81%. 相似文献
992.
Liu Peng Gu Xiaobin Bian Liang Peng Lihua He Huichao 《Journal of Thermal Analysis and Calorimetry》2019,138(1):359-368
Journal of Thermal Analysis and Calorimetry - Leakage issue and low thermal conductivity largely restrict feasibility of fatty acid in real application of thermal energy storage (TES). In this... 相似文献
993.
994.
Xiqing Bian Meili Shao Huaqi Pan Kaibo Wang Shengdong Huang Xin Wu 《Natural product research》2016,30(2):125-130
A new 2(1H)-pyrazinone ring-containing natural product, paenibacillin A (1), together with five known diketopiperazine derivatives 2–6 and two known isoflavones 7–8, was isolated from the culture of an endophytic bacterium Paenibacillus sp. Xy-2. The structure of compound 1 was elucidated by extensive spectral methods, including UV, IR, HR-ESI-MS, 1D and 2D NMR and ECD experiments. Compound 1 exhibited moderate cytotoxicity against HL-60 cell line with IC50 value of 50.48 μM. 相似文献
995.
Numerical methods for computing variationally optimized molecular orbitals within the Hartree–Fock approximation are augmented to include correlation functionals of the density in the energy and the numerical methods for carrying this out are described. The approach is applied explicitly to the Colle–Salvetti correlation energy functional. It is found that the gradient terms in the Colle–Salvetti functional present numerical problems associated with the low-density behavior, but also that they make a relatively small contribution to the correlation energy. In the three cases considered, HF, H2O and N2, it is found that the Colle–Salvetti correction considerably underestimates the correlation energies obtained in coupled-cluster theory. 相似文献
996.
Ahmed Al-Sheikh Masuma Begum Bian Zhang Richard A. Lewis Nicholas E. E. Allenby Paul G. Waddell Bernard T. Golding 《Molecules (Basel, Switzerland)》2020,25(24)
The synthesis of a molecularly diverse library of tetrasubstituted alkenes containing a barbiturate motif is described. Base-induced condensation of N1-substituted pyrimidine-2,4,6(1H,3H,5H)-triones with 5-(bis(methylthio)methylene)-2,2-dimethyl-1,3-dioxane-4,6-dione gave 3-substituted 5-(methylthio)-2H-pyrano[2,3-d]pyrimidine-2,4,7(1H,3H)-triones (‘pyranopyrimidinones’), regioselectively. A sequence of reactions involving ring-opening of the pyran moiety, displacement of the methylthio group with an amine, re-formation of the pyran ring, and after its final cleavage with an amine, gave tetrasubstituted alkenes (3-amino-3-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)propanamides) with a diversity of substituents. Cleavage of the pyranopyrimidinones with an aniline was facilitated in 2,2,2-trifluoroethanol under microwave irradiation. Compounds were tested against Escherichia coli, Staphylococcus aureus, the yeast Schizosaccharomyces pombe, and the pathogenic fungus Candida albicans. No compounds exhibited activity against E. coli, whilst one compound was weakly active against S. aureus. Three compounds were strongly active against S. pombe, but none was active against C. albicans. 相似文献
997.
Lu Yu Yongyun Zhou Xin Xu Sifeng Li Jianbin Xu Baomin Fan Chengyuan Lin Zhaoxiang Bian Albert S.C. Chan 《Tetrahedron letters》2014
As an efficient catalyst, the [Ir(COD)Cl]2/NMDPP complex has been successfully applied to promote the asymmetric ring opening reaction of oxabenzonorbornadienes with various amines, which afforded the corresponding products in good yields (72–98%) with good enantioselectivities (80–90% ee). 相似文献
998.
Studies on the catalytic reaction mechanism of L-lactate dehydrogenase have been carried out by using quantum chemical ab
initio calculation at HF/6-31G* level. It is found that the interconversion reaction of pyruvate to L-lactate is dominated
by the hydride ion Hr transfer, and the transfers of the hydride ionH
r and protonH
r are a quasi-coupled process, in which the energy barrier of the transition state is about 168.37 kJ/mol. It is shown that
the reactant complex is 87.61 kJ/mol lower, in energy, than the product complex. The most striking features in our calculated
results are that pyridine ring of the model cofactor is a quasi-boat-like configuration in the transited state, which differs
from a planar conformation in some previous semiempirical quantum chemical studies. On the other hand, the similarity in the
structure and charge between theH
r transfer process and the hydrogen bonding with lower barrier indicates that the Hr transfer process occurs by means of an unusual manner. In addition, in the transition state the electrostatic interaction
between the substrate and the active site of LDH is quite strong and the polarization of the carbonyl in the substrate is
gradually enhanced accompanying the formation of the transition state. These calculated results are well in accord with the
previous experimental studies, and indicate that the charge on the hydride ion Hr is only +0.13e in the transition state, which is in agreement with the reported semiempirical quantum chemical calculations. 相似文献
999.
A series of four novel 8-hydroxyquinoline-substituted boron-dipyrromethene derivatives, namely 4,4-difluoro-8-(5-(8-hydroxyquinoline))-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (1), 4,4-difluoro-8-(5-(8-hydroxyquinoline))-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (2), 4,4-difluoro-8-(5-azastyryl-(8-hydroxyquinoline))-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (3), and 4,4-difluoro-8-(5-azastyryl-(8-hydroxyquinoline))-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (4), have been synthesized and characterized by a series of spectroscopic methods. The molecular structures of 1 and 2 have been determined by single-crystal X-ray diffraction analyses. The two methyl substituents attached at C-1 and C-7 positions of boron-dipyrromethene (Bodipy) in compound 2 was revealed to prevent the free rotation of the 8-hydroxyquinoline (8-HQ) moiety, resulting in an almost vertical 8-HQ-Bodipy configuration of this compound. This is obviously different from those for 1 with the dihedral angle between 8-hydroxyquinoline and Bodipy moieties of 65.44 and 66.79° due to the lack of methyl substituents in the latter compound. The intense fluorescence from the Bodipy subunit of these compounds was revealed to gradually get diminished along with either decreasing or increasing the pH value under acidic and basic conditions, respectively, in particular for 1, 2, and 4 because of the photoinduced intramolecular electron transfer from excited Bodipy moiety to 8-HQ unit and just an opposite process. This renders these compounds the first OFF-ON-OFF type of pH-dependent fluorescent sensors. Nevertheless, both the intrinsic fluorescence of these compounds and their fluorescent quenching properties along with the change in the pH value have been found to depend on the steric configuration as well as the linking group between 8-hydroxyquinoline and Bodipy moieties, revealing the effect of molecular structure on their fluorescence properties. 相似文献
1000.
A method has been developed for the qualitative and quantitative analysis of pharmacologically active astragalosides isolated from several species of the genus Astragalus by high performance liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry. Seven astragalosides in Radix Astragali and their commercial pharmaceutical preparations were analyzed using the developed method. The extracted ion current chromatograms were obtained from the total ion current chromatogram using the m/z of [M+Na]+ ions produced by target compounds for peak determination. The limits of detection and limits of quantification were in the range of 0.10-0.22 ng and 0.22-0.52 ng in full scan mode, respectively. All calibration curves showed good linear regression (r2 > or = 0.9965) within the test range. The overall intra- and inter-day precision was less than 2.86% for peak area and the accuracy was higher than 92.9% on using ginsenoside I as internal standard. The assay was successfully utilized to analyze the major biologically active astragalosides in six samples of Astragalus membranaceus (Fisch.) Bge var. mongholicus (Bge.) Hsiao. and eight commercial preparations. The overall results demonstrate that this method is simple, selective, and suitable for the quality control of Chinese medicine and their preparation in the low nanogram range. 相似文献