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71.
Iterative operations on microdroplets and continuous monitoring of processes within them; determination of solubility diagrams of proteins 总被引:1,自引:0,他引:1
ME Dolega S Jakiela M Razew A Rakszewska O Cybulski P Garstecki 《Lab on a chip》2012,12(20):4022-4025
We demonstrate a technique for controlling the content of multiple microdroplets in time. We use this system to rapidly and quantiatively determine the solubility diagrams of two model proteins (lysozyme and ribonuclease A). 相似文献
72.
Relativistic density functional theory (DFT) calculations of nuclear spin-spin coupling constants and shielding constants have been performed for selected transition metal (11th and 12th group of periodic table) and thallium cyanides. The calculations have been carried out using zeroth-order regular approximation (ZORA) Hamiltonian and four-component Dirac-Kohn-Sham (DKS) theory with different nonrelativistic exchange-correlation functionals. Two recent approaches for representing the magnetic balance (MB) between the large and small components of four-component spinors, namely, mDKS-RMB and sMB, have been employed for shielding tensor calculations and their results have been compared. Relativistic effects have also been analysed in terms of scalar and spin-orbit contributions at the two-component level of theory, including discussion of heavy-atom-on-light-atom effects for (1)J(CN), σ(C), and σ(N). The results for molecules containing metals from 4th row of periodic table show that relativistic effects for them are small (especially for spin-spin coupling constants). The biggest effects are observed for the 6th row where nonrelativistic theory reproduces only about 50%-70% of the two-component ZORA results for (1)J(MeC) and about 75% for heavy metal shielding constants. It is important to employ a full Dirac picture for calculations of heavy metal shielding constants, since ZORA reproduces only 75%-90% of the DKS results. Smaller discrepancies between ZORA-DFT and DKS are observed for nuclear spin-spin coupling constants. No significant differences are observed between the results obtained using mDKS-RMB and sMB approaches for magnetic balance in four-component calculations of the shielding constants. 相似文献
73.
Michal Achmatowicz Agnieszka Szczepańska Daniel T. Gryko Piotr Salański Janusz Jurczak 《Supramolecular chemistry》2013,25(1):93-95
Abstract Bisamidation of oxaloyl chloride using L-amino acid methyl ester hydrochlorides afforded chiral diesters. The following reactions of diesters with 2,2-(ethylene-dioxy)diethylamine, afforded tetramides possessing C2 symmetry. Coupling of N-hydroxysuccinimide ester of N-benzyloxycarbonyl-L-alanine with 1,5-diamino-3-oxapentane, followed by cleavage of protecting groups, afforded an optically active diamine, which was transformed consequently into tetramide via the reaction with diglycolic acid dimethyl ester under high pressure conditions. 相似文献
74.
Y Lv J Willkomm M Leskes A Steiner TC King L Gan E Reisner PT Wood DS Wright 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(38):11867-11870
The solvothermal reactions of Ti(OEt)(4) with LnCl(3) (Ln=La, Ce) produced new Ti(28) Ln cages, in which the Ln(3+) ions are coordinated within a metallocrown arrangement, which represents the highest nuclearity cages of this type. 相似文献
75.
Two approaches have been developed for the enantioselective Reformatsky reaction of ethyl iododifluoroacetate with ketones to form a quaternary carbon centre using (1R,2S)-1-phenyl-2-(1-pyrrolidinyl)-1-propanol as the chiral ligand. Good yields and high enantioselectivities (80-91% ee) were achieved with a range of alkyl aryl ketones in a convenient one-pot protocol using ethyl iododifluoroacetate and diethylzinc to form the difluorinated Reformatsky reagent homogeneously. In the traditional two-step Reformatsky reaction using the preformed Reformatsky reagent generated from ethyl iododifluoroacetate and zinc dust, good yields and good enantioselectivities (75-84% ee) were also obtained. 相似文献
76.
Wahab A Stepp B Douvris C Valášek M Štursa J Klíma J Piqueras MC Crespo R Ludvík J Michl J 《Inorganic chemistry》2012,51(9):5128-5137
Cyclic voltammetry of 31 icosahedral carborane anions 1-X-12-Y-CB(11)Me(10)(-) at a Pt electrode in liquid SO(2) revealed a completely reversible one-electron oxidation even at low scan rates, except for the anions with Y = I, which are oxidized irreversibly up to a scan rate of 5.0 V/s, and the anion with X = COOH and Y = H, whose oxidation is irreversible at scan rates below 1.0 V/s. Relative reversible oxidation potentials agree well with RI-B3LYP/TZVPP,COSMO and significantly less well with RI-BP86/TZVPP,COSMO or RI-HF/TZVPP,COSMO calculated adiabatic electron detachment energies. Correlations with HOMO energies of the anions are nearly as good, even though the oxidized forms are subject to considerable Jahn-Teller distortion. Except for the anion with X = F and Y = Me, the oxidation potentials vary linearly with substituent σ(p) Hammett constants. The slopes (reaction constants) are ~0.31 and ~0.55 V for positions 1 and 12, respectively. 相似文献
77.
Szostak M Collins KD Fazakerley NJ Spain M Procter DJ 《Organic & biomolecular chemistry》2012,10(30):5820-5824
Herein we describe a strategy for the selective, electron transfer reduction of lactones of all ring sizes and topologies using SmI(2)-H(2)O and a Lewis base to tune the redox properties of the complex. The current protocol permits instantaneous reduction of lactones to the corresponding diols in excellent yields, under mild reaction conditions and with useful chemoselectivity. We demonstrate the broad utility of this transformation through the reduction of complex lactones and sensitive drug-like molecules. Sequential electron transfer reactions and syntheses of deuterated diols are also described. 相似文献
78.
Porus M Maroni P Borkovec M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(13):5642-5651
Polyelectrolyte monolayers on solid substrates are studied with optical reflectivity and the quartz crystal microbalance (QCM). In particular, we investigate the adsorption of anionic poly(styrene sulfonate) (PSS) on amino-functionalized silica as well as cationic poly(allylamine hydrochloride) (PAH) and poly-L-lysine (PLL) on bare silica. By comparing the dry and wet masses measured on identical substrates with these two techniques, we obtain information on the layer thickness and water content of these layers. Monolayers typically feature an adsorbed dry mass of about 0.1-2 mg/m(2), a layer thickness of 0.5-2 nm, and a water content of 20-50%. One finds that the layer thickness increases with increasing concentrations of monovalent salts and polyelectrolytes. 相似文献
79.
Dennis Cao Dr. Michal Juríček Zachary J. Brown Dr. Andrew C.‐H. Sue Dr. Zhichang Liu Juying Lei Anthea K. Blackburn Dr. Sergio Grunder Dr. Amy A. Sarjeant Prof. Ali Coskun Prof. Cheng Wang Prof. Omar K. Farha Prof. Joseph T. Hupp Prof. J. Fraser Stoddart 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8457-8465
We report the synthesis of two [2]catenane‐containing struts that are composed of a tetracationic cyclophane (TC4+) encircling a 1,5‐dioxynaphthalene (DNP)‐based crown ether, which bears two terphenylene arms. The TC4+ rings comprise either 1) two bipyridinium (BIPY2+) units or 2) a BIPY2+ and a diazapyrenium (DAP2+) unit. These degenerate and nondegenerate catenanes were reacted in the presence of Cu(NO3)2?2.5 H2O to yield Cu‐paddlewheel‐based MOF‐1050 and MOF‐1051. The solid‐state structures of these MOFs reveal that the metal clusters serve to join the heptaphenylene struts into grid‐like 2D networks. These 2D sheets are then held together by infinite donor–acceptor stacks involving the [2]catenanes to produce interpenetrated 3D architectures. As a consequence of the planar chirality associated with both the DNP and hydroquinone (HQ) units present in the crown ether, each catenane can exist as four stereoisomers. In the case of the nondegenerate (bistable) catenane, the situation is further complicated by the presence of translational isomers. Upon crystallization, however, only two of the four possible stereoisomers—namely, the enantiomeric RR and SS forms—are observed in the crystals. An additional element of co‐conformational selectivity is present in MOF‐1051 as a consequence of the substitution of one of the BIPY2+ units by a DAP2+ unit: only the translational isomer in which the DAP2+ unit is encircled by the crown ether is observed. The overall topologies of MOF‐1050 and MOF‐1051, and the selective formation of stereoisomers and translational isomers during the kinetically driven crystallization, provide evidence that weak noncovalent bonding interactions play a significant role in the assembly of these extended (super)structures. 相似文献
80.
Jana Balintová Medard Plucnara Pavlína Vidláková Dr. Radek Pohl Dr. Luděk Havran Prof. Dr. Miroslav Fojta Prof. Dr. Michal Hocek 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(38):12720-12731
Benzofurazane has been attached to nucleosides and dNTPs, either directly or through an acetylene linker, as a new redox label for electrochemical analysis of nucleotide sequences. Primer extension incorporation of the benzofurazane‐modified dNTPs by polymerases has been developed for the construction of labeled oligonucleotide probes. In combination with nitrophenyl and aminophenyl labels, we have successfully developed a three‐potential coding of DNA bases and have explored the relevant electrochemical potentials. The combination of benzofurazane and nitrophenyl reducible labels has proved to be excellent for ratiometric analysis of nucleotide sequences and is suitable for bioanalytical applications. 相似文献