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991.
本文给出一类型如P(x,D)=D14+x14D24-(i1/2+(-i)1/2)D12D2+4x1D1D22-i(i1/2-(-i)1/2)x12D23+(1+2i)D22+C 或更一般地p(x,D)=LtL(x,D)+C(L为无解算子)的多重特征算子。指出包括零阶项在内的低阶项对局部可解性能具有决定性影响。具体地说,在原点邻域上面所给算子p(x,D)的主部D14+x14D24为可解算子,当C=0时P(x,D)为不可解算子。但当C>0时又变为局部可解算子。类似地讨论了算子附加零阶项的一些情况。文章最后证明了当自由项f具形|x1|ψ'(x2)(ψ为实函数)时,在原点邻域有古典解的充要条件为ψ(x2)解析。 相似文献
992.
镧系元素钨硅杂多配合物异构体的合成与表征 总被引:5,自引:0,他引:5
关于[Ln(XM_(11)O_(39))_2]~(n-)类配合物合成有一些报道,但它们均未指出其中配体及所得配合物的构型,本文以α-和β_2-SiW_(11)O_(39)~(8-)为配体,首次合成了双-(11-钨硅酸根)合镧系元素钾盐的异构体并进行了结构表征。 1 实验部分 1.1 仪器和试剂 pHS-2型酸度计;883型笔录式极谱仪,384B型极谱分析仪,阿尔法 相似文献
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Dr. Kai‐Yang Niu Prof. Dr. Liang Fang Rong Ye Dr. Dennis Nordlund Dr. Marca M. Doeff Prof. Dr. Feng Lin Dr. Haimei Zheng 《Angewandte Chemie (International ed. in English)》2016,55(46):14272-14276
Controlled synthesis of transition‐metal hydroxides and oxides with earth‐abundant elements have attracted significant interest because of their wide applications, for example as battery electrode materials or electrocatalysts for fuel generation. Here, we report the tuning of the structure of transition‐metal hydroxides and oxides by controlling chemical reactions using an unfocused laser to irradiate the precursor solution. A Nd:YAG laser with wavelengths of 532 nm or 1064 nm was used. The Ni2+, Mn2+, and Co2+ ion‐containing aqueous solution undergoes photo‐induced reactions and produces hollow metal‐oxide nanospheres (Ni0.18Mn0.45Co0.37Ox) or core–shell metal hydroxide nanoflowers ([Ni0.15Mn0.15Co0.7(OH)2](NO3)0.2?H2O), depending on the laser wavelengths. We propose two reaction pathways, either by photo‐induced redox reaction or hydrolysis reaction, which are responsible for the formation of distinct nanostructures. The study of photon‐induced materials growth shines light on the rational design of complex nanostructures with advanced functionalities. 相似文献
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Core-shell surface molecular imprinting technology represents a rather new trend in analytical sciences. In this kind of material, the imprinting sites are located on the surface of the cores or shells of nanoparticles (NPs). This material can improve the capability of recognizing target molecules (analytes), reduce nonspecific adsorption, increase the relative adsorption capacity and selectivity, and accelerate the rate of mass transfer. This review (with 158 references) focuses on recent trends in core-shell MIPs. Following an introduction into the field, a first main section covers common core-materials including silica, magnetic NPs, quantum dots (including semiconductor quantum dots and carbon dots), gold and silver nanoclusters, and up-conversion materials. A further section covers the materials and reagents required for preparing MIPs (with subsections on templates, functional monomers, cross-linkers, initiators, and effects of solvent). A next main section covers synthetic approaches such as precipitation polymerization, emulsion polymerization, and grafting approach. A final section gives examples for applications of core-shell MIPs in analytical assays and in sensing. 相似文献
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Five inorganic–organic hybrid vanadates based on tetravanadate cores, transition metals and N-donor ligands have been designed and synthesized under hydrothermal conditions, namely, [Zn(eIM)_3]_2V_4O_(12)(1), [Zn(pIM)_3]_2V_4O_(12)H_2O(2), [Zn(ipIM)_3]_2V_4O_(12)(3), [Co(e IM)_3]_2V_4O_(12)H_2O(4), [Cu(eIM)_2(H+2O)]_2V_4O_(12)(_5)(eIM = 1-ethylimidazole, p IM = 1-propylimidazole, ip IM = isopropylimidazole). All compounds were fully characterized by single-crystal XRD, powder XRD, elemental analysis, TGA, and FT-IR spectroscopy.The hybrid zinc vanadates(1–3) and cobalt vanadate(4) exhibit interesting 2D folded structures and the hybrid copper vanadate(5) presents a 1D chain configuration. All compounds can catalyze olefin epoxidation reactions when using TBHP(TBHP = tert-butyl hydroperoxide) as an oxidant in acetonitrile.The introduction of transition metal ions into tetravanadate cores not only improved the catalytic activity but also fulfilled the heterogeneous catalytic behavior. 1–5 all exhibit extraordinary efficiency in converting olefins to the corresponding epoxides with high conversion and selectivity(particularly,conv. up to 97.1%, sele. up to 100% for 1). Leaching test was also carried out to prove the heterogeneous behavior. 相似文献
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Giant Hollow Heterometallic Polyoxoniobates with Sodalite‐Type Lanthanide–Tungsten–Oxide Cages: Discrete Nanoclusters and Extended Frameworks 下载免费PDF全文
Lu Jin Dr. Xin‐Xiong Li Yan‐Jie Qi Ping‐Ping Niu Prof. Dr. Shou‐Tian Zheng 《Angewandte Chemie (International ed. in English)》2016,55(44):13793-13797
The first series of niobium–tungsten–lanthanide (Nb‐W‐Ln) heterometallic polyoxometalates {Ln12W12O36(H2O)24(Nb6O19)12} (Ln=Y, La, Sm, Eu, Yb) have been obtained, which are comprised of giant cluster‐in‐cluster‐like ({Ln12W12}‐in‐{Nb72}) structures built from 12 hexaniobate {Nb6O19} clusters gathered together by a rare 24‐nuclearity sodalite‐type heterometal–oxide cage {Ln12W12O36(H2O)24}. The Nb‐W‐Ln clusters present the largest multi‐metal polyoxoniobates and a series of rare high‐nuclearity 4d‐5d‐4f multicomponent clusters. Furthermore, the giant Nb‐W‐Ln clusters may be isolated as discrete inorganic alkali salts and can be used as building blocks to form high‐dimensional inorganic–organic hybrid frameworks. 相似文献
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Xiaohui Liu Ting Dong Yu Zhou Prof. Dr. Niu Huang Prof. Dr. Xiaoguang Lei 《Angewandte Chemie (International ed. in English)》2016,55(46):14330-14334
Glycolipids are important structural components of biological membranes and perform crucial functions in living systems, including signaling transduction and interaction with extracellular environment. However, the mechanistic exploration of glycolipids in vivo is challenging because they are not genetically encoded. Herein, we designed and synthesized a series of bifunctional monogalactosyldiacylglycerol (MGDG) probes as a model by introducing diazirine and terminal alkyne moieties on an aliphatic chain. In combination with proteome profiling and molecular modeling, we have demonstrated that MGDG alleviates inflammation by antagonizing TLR4. 相似文献
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