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991.
D. Hreniak W. Strek A. Opalińska M. Nyk M. Wołcyrz W. Lojkowski J. Misiewicz 《Journal of Sol-Gel Science and Technology》2004,32(1-3):195-200
A sol–gel method for the synthesis of nanosized powders of yttrium disilicate doped with Tb3 + is presented. The influence of grain size and annealing temperature on the structure and luminescence properties of the materials obtained has been investigated. The preparation of glass-ceramic composite has been also described. The effect of incorporating the nanocrystals into sol–gel silica glasses on their physicochemical properties has been shown and discussed. A lack of influence of the annealing above 1300°C on the lifetimes measured for the nanocrystals embedded in the glass, as compared to the Y2Si2O7:Tb3 + powders, has been observed. 相似文献
992.
993.
994.
为了解纸质包装材料中甲醛、乙醛向食品模拟物改性聚苯醚( Tenax)中的迁移行为,建立了一步提取衍生化、超高效液相色谱测定纸质包装材料和Tenax中的甲醛和乙醛的方法。本方法在甲醛和乙醛的测定范围内,线性相关系数R2>0.9999,甲醛检出限为0.03 mg/m2,乙醛检出限为0.04 mg/m2,测定纸样和Tenax的加标回收率为90.1%~108.6%。采用本方法研究不同温度和时间下两种纸质包装材料中甲醛、乙醛向Tenax中的迁移规律。研究表明,甲醛、乙醛迁移行为随时间变化趋势大致相同,均呈现迁移率随迁移时间延长先迅速增大,后又减小达到一个常数;甲醛和乙醛迁移率受温度的影响不同,达到平衡后,甲醛在30℃下迁移率最高,乙醛在70℃和50℃下迁移率高;甲醛和乙醛向Tenax中的迁移率差异较大,达到平衡后,乙醛的迁移率远高于甲醛。 相似文献
995.
本文介绍了气体元素分析样品表面处理的最新研究成果,综述了热导法、红外吸收法、库仑滴定法、飞行时间质谱法和火花源原子发射光谱法等分析方法在无机固态材料气体分析中的应用现状,分析了各自的特点及存在的问题,并展望了气体分析的发展方向(引用文献85篇)。 相似文献
996.
A. M. Garrido Pedrosa M. J. B. Souza D. M. A. Melo A. S. Araujo 《Journal of Thermal Analysis and Calorimetry》2007,87(2):351-355
The thermo-programmed reduction study of
Pt/WOx–ZrO2 materials
prepared with different tungsten loading were performed by thermogravimetry.
The samples were synthesized by impregnation method and calcined at 600, 700
and 800°C. The characterizations of both un-calcined and calcined materials
were carried out using different techniques: thermal analysis (TG and DTA),
X-ray diffraction (XRD) and thermo-programmed reduction (TPR). TG and DTA
analysis of un-calcined were used to determination of calcination temperatures
of the samples. XRD diffractograms were useful to help us in the determination
of phase presents. TPR profiles showed between three and four events at different
temperatures attributed to platinum reduction and the different stages of
tungsten specie reduction. 相似文献
997.
A chemo-electro-mechanical multi-field model, termed the multi-effect-coupling pH-electric-stimuli (MECpHe) model, has been
developed to simulate the response behavior of smart hydrogels subject to pH and electric voltage coupled stimuli when the
hydrogels are immersed in a pH buffer solution subject to an externally applied electric field. The MECpHe model developed
considers multiphysics effects and formulates the fixed charge density with the coupled buffer solution pH and electric voltage
effects, expressed by a set of nonlinear partial differential governing equations. The model can be used to predict the hydrogel
displacement and the distributive profiles of the concentrations of diffusive ionic species and the electric potential and
the fixed charge density in both the hydrogels and surrounding solution. After validation of the model by comparison of current
numerical results with experiment data extracted from the literature, one-dimensional steady-state simulations were carried
out for equilibrium of the smart hydrogels subject to pH and electric coupled stimuli. The effects of several important physical
conditions, including the externally applied electric voltage, on the distributions of the concentrations of diffusive ionic
species, the electric potential, the fixed charge density, and the displacement of the hydrogel strip were studied in detail.
The effects of the ionic strength on the bending deformation of the hydrogels under the solution pH and electric voltage coupled
stimuli are also discussed. 相似文献
998.
Yanfeng Zhao Nengsheng Ye Rongli Zhang Xue Feng Guoan Luo Yiming Wang 《Frontiers of Chemistry in China》2007,2(4):422-427
High-resolution two-dimensional gel electrophoresis (2-DE), followed by computer-assisted image analysis was used to screen
protein patterns of normal and infarcted myocardial tissues for quantitative and qualitative differences in protein expression.
In the gels of pH 5–8 immobilized pH gradient (IPG) strips, 851 protein spots were detected in normal myocardial tissue and
1 032 protein spots were resolved in infarcted myocardial tissue. Thirteen protein spots only expressed in normal myocardial
tissue, and 14 protein spots only expressed in infarcted myocardial tissue. Results also showed that 49 protein spots displayed
quantitative changes in expression between normal and infarcted myocardial tissue. Eleven protein spots were subjected to
mass spectrometry (MS) analysis and seven proteins were identified by peptide mass fingerprinting (PMF). These proteins may
be involved in cardiovascular injury, and could play an important role in the treatment of coronary heart disease.
__________
Translated from Chemical Journal of Chinese Universities, 2006, 8(27): 1467–1471 [译自: 高等学校化学学报] 相似文献
999.
Olejniczak AB Plesek J Leśnikowski ZJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(1):311-318
A general approach to the synthesis of nucleoside conjugates between derivatives of thymidine (T), 2'-O-deoxycytidine (dC), 2'-O-deoxyadenosine (dA), and 2'-O-deoxyguanosine (dG), and metallacarborane complexes is described. Metallacarborane-nucleoside derivatives are prepared by reaction of the dioxane-metallacarborane adduct with a base-activated 3',5'-protected nucleoside. In the case of T and dG a mixture of regioisomers, which is easily separable by chromatographic methods, is obtained, thus yielding a series of modifications containing metallacarborane groups at the 2-O, 3-N, 4-O and 1-N, 2-N, 6-O locations, respectively; dC and dA are alkylated at the exo-amino function. The proposed methodology provides a route for the synthesis and study of nucleic acids modified with metallacarboranes at designated locations and a versatile approach to the incorporation of metals into DNA. 相似文献
1000.
Llabrés i Xamena FX Teruel L Alvaro M Garcia H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(2):515-519
We have used porous anodised Al(2)O(3) membranes as inert matrix for constructing and organizing spatially ternary donor/conductor/acceptor (DCA) systems exhibiting photovoltaic cell activity on the micrometric-length scale. These DCA triads were built stepwise by first growing a conducting polymer inside the membrane pores, thus forming nanorods that completely fill the internal pore space of the membrane. Then, an electron donor and an electron acceptor were adsorbed one on each side of the membrane, so that they were separated by a distance equal to the membrane thickness (ca. 60 microm), but electronically connected through the conductive polymer. When this device was placed between two electrodes and irradiated with visible light, electrons jumped from the donor molecule, crossed the membrane from side to side through the conductive polymer (a journey of about 60 microm!) until they finally reach the acceptor molecule. In so doing, an electric voltage was generated between the two electrodes, capable of maintaining an electric current flow from the membrane to an external circuit. Our DCA device constitutes the proof of a novel concept of photovoltaic cells, since it is based on the spatial organization at the micrometric scale of complementary, but not covalently linked, electron-donor and electron-acceptor organic species. Thus, our cell is based in translating photoinduced electron transfer between donors and acceptors, which is known to occur at the molecular nanometric scale, to the micrometric range in a spatially organised system. In addition our cell does not need the use of liquid electrolytes in order to operate, which is one of the main drawbacks in dye-sensitised solar cells. 相似文献