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161.
Meng Zhao Dr. Hong-Jie Peng Bo-Quan Li Dr. Xiao Chen Jin Xie Dr. Xinyan Liu Prof. Qiang Zhang Prof. Jia-Qi Huang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):9096-9102
In situ evolution of electrocatalysts is of paramount importance in defining catalytic reactions. Catalysts for aprotic electrochemistry such as lithium–sulfur (Li-S) batteries are the cornerstone to enhance intrinsically sluggish reaction kinetics but the true active phases are often controversial. Herein, we reveal the electrochemical phase evolution of metal-based pre-catalysts (Co4N) in working Li-S batteries that renders highly active electrocatalysts (CoSx). Electrochemical cycling induces the transformation from single-crystalline Co4N to polycrystalline CoSx that are rich in active sites. This transformation propels all-phase polysulfide-involving reactions. Consequently, Co4N enables stable operation of high-rate (10 C, 16.7 mA cm−2) and electrolyte-starved (4.7 μL mgS−1) Li-S batteries. The general concept of electrochemically induced sulfurization is verified by thermodynamic energetics for most of low-valence metal compounds. 相似文献
162.
Two new 1D helical coordination polymers based on polyoxometalate were synthesized by self-assembly of Keggin-type POMs and copper salts in the presence of triangular N-heterocyclic derivatives or long-chain N-containing carboxylate ligand, that are, (H3O)[{Cu(H2tpim)2}{SiMo12O40}] · 0.5H2O [Htpim = 2,4,5-tri(4-pyridyl)-imidazole] ( 1 ) and [Cu2(Hcpp)3(cpp)(H2O)][PMo12O40] · 2H2O [Hcpp = 1-(4-cyanobenzyl)-3–2-yl)pyrazole] ( 2 ). Their structures were determined by single-crystal X-ray diffraction and further characterized by elemental analyses and TG analyses. Compounds 1 and 2 exhibit (1D→2D) interdigitated architectures assembled from 1D helical chains. In compound 1 , the achiral 2D interdigitated nets containing left- and right-handed helixes are further interdigitated with each other to form a 3D supramolecular framework. In compound 2 , adjacent 2D interdigitated layers with opposite chirality are further extended by supramolecular interactions into a 3D supramolecular network, in which non-coordinating Keggin-type POMs as guests are encapsulated. 相似文献
163.
Shan Jin Manman Zhou Xi Kang Xiaowu Li Wenjun Du Xiao Wei Shuang Chen Dr. Shuxin Wang Prof. Manzhou Zhu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):3919-3923
The high-dimensional (that is, three-dimensional (3D)) assembly of nanomaterials is an effective means of improving their properties; however, achieving this assembly at the atomic level remains challenging. Herein, we obtained a novel nanocluster, [Au8Ag57(Dppp)4(C6H11S)32Cl2]Cl (Dppp=1,3-bis(diphenylphosphino)propane) showing a 3D octameric assembly mode involving the kernel penetration of eight complete icosahedral Au@Ag10Au2 units for the first time. The atomically precise structure was determined by single-crystal X-ray diffraction, and further confirmed by thermogravimetric analysis, X-ray photoelectron spectroscopy, and electrospray ionization mass spectrometry measurements. Furthermore, ligand-induced transformation prompted the conversion of [Au8Ag57(Dppp)4(C6H11S)32Cl2]Cl, with complete octameric fusion into [Au8Ag55(Dppp)4(C6H11S)34][BPh4]2, with incomplete octameric fusion. These observations will hopefully facilitate further research on the assembly of M13 nanobuilding blocks. 相似文献
164.
Beddington-DeAngelis型捕食-食饵动力系统的正平衡点及其稳定性 总被引:1,自引:0,他引:1
肖海滨 《高校应用数学学报(英文版)》2006,21(4)
A class of Beddington-DeAngelis' type predator-prey dynamic system with prey and predator both having linear density restriction is considered. By using the qualitative methods of ODE, the existence and uniqueness of positive equilibrium and its global asymptotic stability are analyzed. The direct criterions for local stability of positive equilibrium and existence of limit cycle are also established when inference parameter of predator is small. 相似文献
165.
转移矩阵法在负折射率介质材料平板波导中的应用研究 总被引:3,自引:3,他引:0
利用严格电磁理论,推导出了适用于负折射率介质材料光波导的转移矩阵,分析讨论了转移矩阵的性质和应用.利用转移矩阵方法,推导出导波层为负折射率介质材料、覆盖层和衬底为右手材料的三层对称介质光波导的本征色散方程.用图解法研究了负折射率介质波导中TE波的异常色散特性.在负折射材料介质波导中没有零阶模,最低阶为1阶模,并且有截止频率,只有波导参量满足一定条件的时候才会存在,导模的横向波数可以为实数和纯虚数,而正折射率介质波导导模的横向波数只能为实数. 相似文献
166.
167.
不同溶剂中番茄红素的荧光光谱及其特性研究 总被引:5,自引:5,他引:0
用970CRT荧光光度计测定了番茄红素在正己烷、乙酸乙酯、四氢呋喃、氯仿、丙酮和苯等6种溶剂中的荧光光谱以及番茄红素在四氢呋喃溶液中不同浓度下的荧光光谱。对所测光谱分析得出:6种溶剂中荧光光谱的最大峰值波长(λmax)分别为542.5 nm5、48.2 nm5、55.0 nm、555.7 nm、556.4 nm和565.7 nm,由于溶剂效应,随溶剂极性由小到大,荧光光谱的最大峰值波长(λmax)逐渐红移,由这些峰值波长计算得出相应的番茄红素分子在6种溶剂中的跃迁能ET分别为220.5 kJ/mol2、18.2 kJ/mol2、15.6 kJ/mol2、15.3 kJ/mol2、14.9 kJ/mol和211.5 kJ/mol,可见跃迁能ET也随溶剂极性增大而降低;当番茄红素在四氢呋喃溶液中的质量浓度低于50μg/ml时,溶液的荧光强度随溶液浓度增加而增大,当质量浓度高于50μg/ml时,由于番茄红素的激发态分子与基态分子相互作用,荧光强度反而减小;在浓度低于80μg/ml的溶液中,番茄红素的荧光光谱除最大峰值外还有三个较小峰值,据此计算得出相应的番茄红素分子的跃迁能分别为E(T1)=278.2 kJ/mol、E(T2)=260.2 kJ/mol和E(T3)=239.3 kJ/mol。 相似文献
168.
169.
He-Xia Huang Hui-Jun Tan Zheng-Kang Lin Zi-Jie Li Shu Sun Hao Chen Zhi-Xiang Xiao 《Acta Mechanica Sinica》2021,37(1):156-168
The submerged inlet is an attractive configuration for advanced helicopters due to its high stealth performance and low external drag.In this paper,a submerged ... 相似文献
170.
Nonlinear Dynamics - A robust fixed-time control framework is presented to stabilize flexible spacecraft’s attitude system with external disturbance, uncertain parameters of inertia, and... 相似文献