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991.
Yuehua Dou Stephen Haswell John Greenman Jay Wadhawan 《Electrochemistry communications》2009,11(10):1976-1981
The detection of hydrogen peroxide is detailed using horseradish peroxidase and anthraquinone. Both species are immobilized on a glassy carbon electrode substrate. This dual immobilization gives rise to lower detection limits compared with the situation when either of the species is immobilized. Detection limits of 40 nM are reported within physiologically-relevant media. 相似文献
992.
A method is proposed to rapidly predict the hydrogen bond cooperativity in N‐methylacetamide chains. The parameters needed are obtained from the fittings to the hydrogen bonding energies in the formamide chains containing 2 to 8 monomeric units. The scheme is then used to calculate the individual hydrogen bonding energies in N‐methylacetamide chains containing 2 to 7 monomeric units. The cooperativity predicted is in good agreement with those obtained from MP2/6‐31+G** calculations by including the BSSE correction. Our scheme is further employed to predict the individual hydrogen bonding energies in larger N‐methylacetamide chains containing up to 200 monomeric N‐methylacetamide units, to which the MP2 method cannot be applied. Based on our scheme, a cooperative effect of over 170 % of the dimer hydrogen bonding energy in long N‐methylacetamide chains is predicted. The method is also applied to heterogeneous chains containing formamide, acetamide, N‐methylformamide, and N‐methylacetamide. The individual hydrogen bonding energies in these heterogeneous chains are also in good agreement with those obtained from MP2 calculations with the BSSE correction, further demonstrating that our method is reasonable. 相似文献
993.
We address asymptotic analysis of option pricing in a regime switching market where the risk free interest rate, growth rate and the volatility of the stocks depend on a finite state Markov chain. We study two variations of the chain namely, when the chain is moving very fast compared to the underlying asset price and when it is moving very slow. Using quadratic hedging and asymptotic expansion, we derive corrections on the locally risk minimizing option price. 相似文献
994.
Falk M. Hante Günter Leugering Thomas I. Seidman 《Applied Mathematics and Optimization》2009,59(2):275-292
We consider networked transport systems defined on directed graphs: the dynamics on the edges correspond to solutions of transport
equations with space dimension one. In addition to the graph setting, a major consideration is the introduction and propagation
of discontinuities in the solutions when the system may discontinuously switch modes, naturally or as a hybrid control. This
kind of switching has been extensively studied for ordinary differential equations, but not much so far for systems governed
by partial differential equations. In particular, we give well-posedness results for switching as a control, both in finite
horizon open loop operation and as feedback based on sensor measurements in the system. 相似文献
995.
In this work, the structure of the ionic liquid [emim]OH and the influence of water molecules on this ionic liquid were studied
by the DFT theory at the B3LYP/6-311++G** level. The calculation results indicate that [emim]OH cannot exist in the form of
ion pairs, rather it is inclined to exist the form of water and imidazole carbene. Further studies showed that water mainly
influences the anion: it can disperse the negative charge of the O atom of the OH− anion and form hydroxyl–water clusters with the anion. When there are two water molecules in the ionic liquid, the system
is most likely to exist in the form of ion-pairs that are composed of hydroxyl–water clusters and cations. Configurations
formed near the C2-H fragment of imidazole were favored, and hydrogen bonding interaction plays an important role in the ionic liquid system. 相似文献
996.
Xiao‐Ning Zhang Dong‐Sheng Li Prof. Dr. Ji‐Jiang Wang Jun Zhao Cai‐Xia Meng Ya‐Pan Wu Yao‐Yu Wang 《无机化学与普通化学杂志》2009,635(15):2622-2626
Two new compounds, [Ag(Hppdb)]n ( 1 ) and {[Ag2(Hppdb)2(bpe)] · 5.5H2O}n( 2 ) [H2ppdb = [2,3‐f]pyrazino[1,10]phenanthroline‐2,3‐dicarboxylic acid, bpe = trans‐1,2‐bis(4‐pyridyl)ethylene], were synthesized and characterized. In 1 , Hppdb– ions link AgI cations to form an infinite 1D [–Ag–(Hppdb)–Ag–]n chain, furthermore, the dimensionality is extended to 2D layers through synergistic π–π stacking, hydrogen‐bonding and weak Ag ··· O interactions. Correspondingly, the dimeric [(Ag)(Hppdb)]2 subunits in 2 are connected by bpe ligands to generate a loop‐link‐shaped 1D chain motif, which is further joined through a R22(18)C–H ··· O hydrogen‐bonding ring to afford interesting diagonal/diagonal inclined catenation 2D + 2D → 3D supramolecular architectures. In addition, solid‐state properties such as photoluminescence and thermal stability of the two compounds were studied. 相似文献
997.
Anion recognition by 1,3-disiloxane-1,1,3,3-tetraols has been elucidated by 1H NMR titrations and ESI-MS in organic solvents. The association constants of the receptors for halide anions are larger than those of silanediol and 1,3-disiloxane-1,3-diol due to the cooperative hydrogen bonds by four silanol hydroxy groups of 1,3-disiloxane-1,1,3,3-tetraols. 相似文献
998.
Xiao‐Xu Li Ning Wang Shan‐Tang Yue Prof. Dr. Zhao‐Yang Li Hong‐Yan Wu Ying‐Liang Liu 《无机化学与普通化学杂志》2009,635(15):2648-2652
Self‐assembly of the rigid organic ligand 2‐propyl‐4,5‐dicarboxy‐1H‐imidazole ( L ) with different metal ions (Zn2+, Ni2+, Cu2+, Cd2+) led to four new complexes, namely, [M( L )(phen)] [M = Zn ( 1 ); Ni ( 2 ); Cd ( 3 )] and [Cu( L )( 4 )] (phen = 1,10‐phenanthroline). Their structures were determined by single‐crystal X‐ray diffraction analyses, and they were further characterized by elemental analysis, IR spectroscopy, and thermogravimetric analysis. Whereas compounds 1 , 2 , and 3 are discrete units, hydrogen‐bonding interactions play a vital role in these complexes. Compounds 1 and 2 form one‐dimensional (1D) and two‐dimensional (2D) structures through hydrogen‐bondinginteractions with helical character. In 1 , the hydrogen bonds (O–H ··· O) alternately bridge the MII cations of the discrete units to form a one‐dimensional (1D) infinite helical chain. Complex 2 forms a 2D helical layer through parallel hydrogen bonds (N/O–H ··· O/N) between two adjacent helical chains. In 3 , the hydrogen bonds (N–H ··· O) connect adjacent discrete units into a ten‐membered ring with extension into a one‐dimensional double‐chain supramolecular structure. Complex 4 is a two‐dimensional gridlike (4,4) topological layer which is extended to a 3D network by hydrogen bonding. The solid‐state fluorescence spectrum of complex 3 was determined. 相似文献
999.
Johannes Schwöbel Ralf‐Uwe Ebert Ralph Kühne Gerrit Schüürmann 《Journal of computational chemistry》2009,30(9):1454-1464
A quantum chemical model is introduced to predict the H‐bond donor strength of monofunctional organic compounds from their ground‐state electronic properties. The model covers ? OH, ? NH, and ? CH as H‐bond donor sites and was calibrated with experimental values for the Abraham H‐bond donor strength parameter A using the ab initio and density functional theory levels HF/6‐31G** and B3LYP/6‐31G**. Starting with the Morokuma analysis of hydrogen bonding, the electrostatic (ES), polarizability (PL), and charge transfer (CT) components were quantified employing local molecular parameters. With hydrogen net atomic charges calculated from both natural population analysis and the ES potential scheme, the ES term turned out to provide only marginal contributions to the Abraham parameter A, except for weak hydrogen bonds associated with acidic ? CH sites. Accordingly, A is governed by PL and CT contributions. The PL component was characterized through a new measure of the local molecular hardness at hydrogen, η(H), which in turn was quantified through empirically defined site‐specific effective donor and acceptor energies, EEocc and EEvac. The latter parameter was also used to address the CT contribution to A. With an initial training set of 77 compounds, HF/6‐31G** yielded a squared correlation coefficient, r2, of 0.91. Essentially identical statistics were achieved for a separate test set of 429 compounds and for the recalibrated model when using all 506 compounds. B3LYP/6‐31G** yielded slightly inferior statistics. The discussion includes subset statistics for compounds containing ? OH, ? NH, and active ? CH sites and a nonlinear model extension with slightly improved statistics (r2 = 0.92). © 2008 Wiley Periodicals, Inc. J Comput Chem 2009 相似文献
1000.
Xiaocong Gong Qingling Li Kehua Xu Xin Liu Hongmin Li Zhenzhen Chen Lili Tong Bo Tang Hongbo Zhong 《Electrophoresis》2009,30(11):1983-1990
A new method using MCE with LIF detection was developed for the determination of hydrogen peroxide (H2O2). Bis(p‐methylbenzenesulfonyl)dichlorofluorescein, a new fluorogenic reagent synthesized by our laboratory was employed as a labeling reagent, the derivatization reaction was performed in 0.10 M HEPES buffer (pH 7.4) for 30 min at 37°C. The detection of H2O2 was accomplished in 55 s, using a 40 mM HEPES buffer, 20% mannitol, pH 7.4, on a glass microchip. The RSDs of migration time and peak area were 1.8 and 3.7%, respectively. Method validation showed the linear response ranging from 0.50 to 50 μM with an LOD (S/N=3) of 0.20 μM (19.1 amol). The proposed method was applied to determine H2O2 in phorbol myristate acetate‐stimulated RAW264.7 macrophages, the concentration of H2O2 was found to be 1.86±0.05 μM; recoveries for macrophage samples were from 96.7 to 97.8%, within‐days and between‐days accuracies were 4.5% (n=5) and 6.8% (n=5), respectively. 相似文献