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971.
Abstract Evaluation of potential economic consequences of alternative management actions requires an understanding of how the biological stock will be affected by the management action and an understanding of the response of economic systems to changes in the timing, magnitude, and size distribution of harvests and changes in the location and catchability of the biological stock. We use a hybrid structural time series model to represent Pacific halibut (Hippoglossus stenolepis) stock and recruitment dynamics and a system of structural equations to represent supply and demand relationships for Pacific halibut from Alaska and British Columbia. Model simulations explore the economic effects of changes in recruitment success, growth rate, and carrying capacity, and changes in international supplies of halibut. 相似文献
972.
973.
重质油胶体聚集结构的耗散粒子动力学模拟 总被引:1,自引:0,他引:1
重质油是以沥青质为胶核分散于饱和油分中形成的极其复杂的胶体体系.本文采用耗散粒子动力学(DPD)方法研究重质油的胶体结构及其影响因素.根据重质油各组分的分子结构特征,构建了描述重质油组分的粗粒化模型化合物.模拟结果表明,本文构建的粗粒化模型能很好地反映重质油的胶体聚集结构.沥青质分子结构对胶体聚集结构有序性有显著影响,较高稠合程度的芳香环结构将使胶束结构有较高的有序性,烷基侧链则表现出分散作用.重质油中的胶质具有胶溶作用,胶质与沥青质的浓度比存在一个极限,当小于这个极限时,重质油将出现聚沉. 相似文献
974.
应用分子动力学模拟方法研究了海藻糖抑制淀粉质多肽42(Aβ42)构象转变的分子机理.结果表明,海藻糖溶液浓度对Aβ42构象转变具有非常重要的影响.在水和低浓度海藻糖溶液(0.18mol·L-1)中,Aβ42可由初始的α-螺旋结构转变成β-折叠的二级结构;但海藻糖浓度为0.37mol·L-1时即可有效抑制Aβ42的构象转变.这是因为海藻糖利用其优先排阻作用使水分子在多肽周围0.2nm内富集,而其自身却在距离多肽0.4nm的位置附近团聚.另外,海藻糖还可通过降低多肽间的疏水相互作用,减少多肽分子内远距离的接触,有效抑制多肽的疏水塌缩和构象转变.上述分子模拟的结果对于进一步合理设计阿尔茨海默病的高效抑制剂具有非常重要的理论指导意义. 相似文献
975.
977.
To develop and analyze new computational techniques for the Boltzmann equation based on model or approximation adaptivity, it is imperative to have disposal of a compliant model problem that displays the essential characteristics of the Boltzmann equation and that admits the extraction of highly accurate reference solutions. For standard collision processes, the Boltzmann equation itself fails to meet the second requirement for d = 2, 3 spatial dimensions, on account of its setting in 2d, while for d = 1 the first requirement is violated because the Boltzmann equation then lacks the convergence-to-equilibrium property that forms the substructure of simplified models. In this article we present a numerical investigation of a new one-dimensional prototype of the Boltzmann equation. The underlying molecular model is endowed with random collisions, which have been fabricated such that the corresponding Boltzmann equation exhibits convergence to Maxwell–Boltzmann equilibrium solutions. The new Boltzmann model is approximated by means of a discontinuous Galerkin (DG) finite-element method. To validate the one-dimensional Boltzmann model, we conduct numerical experiments and compare the results with Monte-Carlo simulations of equivalent molecular-dynamics models. 相似文献
978.
We characterize size-dependent carrier relaxation dynamics of partial laser structures containing quantum dashes by time-resolved degenerate four wave mixing between 1.2 and 1.6 μm. 相似文献
979.
Photophysical properties of a series of high luminescent europium complexes with fluorinated ligands
Jiangbo Yu 《Journal of luminescence》2011,131(2):328-335
A series of high luminescent europium complexes have been synthesized, such as Eu(TFNB)3phen (1), Eu(PFNP)3phen (2), Eu(HFNH)3phen (3) and Eu(PFND)3phen (4), which have β-diketone ligands containing fluorinated alkyl chains with different lengths and conjugated naphthyl groups, i.e., 4,4,4-trifluoro-1-(2-naphthyl)butane-1,3-dione (TFNB); 4,4,5,5,5-pentafluoro-1-(2-naphthyl)pentane-1,3-dione (PFNP); 4,4,5,5,6,6,6-heptafluoro-1-(2-naphthyl)hexane-1,3-dione (HFNH) and 4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-pentadecafluoro-1-(2-naphthyl)decane-1,3-dione (PFND). And 10-phenanthroline (phen) is coordinated as the neutral second ligand in 1-4. The crystal structures of 1 and 2 have been studied, which are typical and similar to that of 3. The results of TGA-DTA suggest that these Eu complexes have good thermal stabilities. By means of absorption and (time resolved) emission spectroscopy including determination of luminescence quantum yields, energy transfer dynamics and so on, the following results have been obtained: first, these Eu complexes show characteristic pure red color photoluminescence emission with high quantum efficiencies from the central Eu3+ ions through the excitation of the ligands; secondly, photophysical properties of 1, 2, 3 and 4, especially the lifetimes of excited states 5D0 of Eu3+ ions and quantum efficiencies are influenced by the different lengths of fluorinated alkyl chains, though the singlets (S1) and triplets (T1) of the fluorinated ligands are almost the same. 相似文献
980.
We setup an ultrafast noncollinear optical parametric amplification system for fluorescence spectral dynamics study. The simultaneous broadband amplifying ability makes it suitable as an ultrafast spectrometer with femtosecond time-resolution. By real-time fluctuation correction, femtosecond fluorescence spectra are obtained efficiently by a single scan. With this technique, the solvation dynamics of DCM dye in four solvents are measured to demonstrate the performance of the system. We show that this ultrafast time-resolved spectrometer is very useful and efficient in studying ultrafast spectral dynamics. 相似文献