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91.
Burley GA Avent AG Boltalina OV Drewello T Goldt IV Marcaccio M Paolucci F Paolucci D Street JM Taylor R 《Organic & biomolecular chemistry》2003,1(11):2015-2023
A range of tertiary carbanions XCH(CO2Et)2 of differing sizes have been reacted with C60F18 to assess the steric effect of X on the position of nucleophilic substitution. For X = CO2Et, NO2, P(O)(OMe)2, SO2CH2Ph, the all trans annulenes (trannulenes) were obtained as a result of extended S(N)2' (i.e. S(N)2') substitution; in the case of the phosphorus compound, with reduced amounts of base (DBU) dephosphonylation of one or more P(O)(OMe)2 groups by hydrogen occurred. Trannulene formation did not occur for X = F, CN due to the smaller size of the nucleophile, and in the latter case substitution was shown to take place by an S(N)2' mechanism, resulting in the addend being adjacent to a fluorine addend. Trannulenes (X = CO2Et, Br, Cl) exhibited reversible one-electron reductions at potentials (-0.02 to -0.09 V) significantly more positive than for [60]fullerene. Trannulene (X = NO2) exhibited an irreversible one-electron reduction (0.08 V); the irreversibility may be associated with fluorine loss. Conformational isomerism at temperatures below 298 K was observed for all trannulene derivatives as a result of eclipsing addend-addend interactions. Minimum energy conformations with a rotational energy barrier of 12-15 kcal mol(-1) were observed when these interactions are calculated using molecular mechanics. 相似文献
92.
Alvarez CS Boss SR Burley JC Humphry SM Layfield RA Kowenicki RA McPartlin M Rawson JM Wheatley AE Wood PT Wright DS 《Dalton transactions (Cambridge, England : 2003)》2004,(21):3481-3487
Manganocene, Cp(2)Mn, has been employed as a precursor in the synthesis of a range of Mn(II) dimers of the type [CpMn(micro-X)](2)[X = 8-NHC(9)H(6)N (1), N(Ph)(C(5)H(4)N)(2), N(4-EtC(6)H(4))(C(5)H(4)N)(3) and C[triple bond]CPh (4)] as well as the bis-adduct [Cp(2)Mn[HN=C(NMe(2))(2)](2)](5). The solid-state structures of 1-5 are reported. Variable-temperature magnetic measurements have been used to assess the extent of Mn(micro-X)Mn communication within the dimers of 1-4 as a function of the bridging ligands (X). 相似文献
93.
Vandana Tripathi Lagy T Baby PV Madhusudhana Rao SK Hui R Singh JJ Das P Sugathan N Madhavan AK Sinha 《Pramana》1999,53(3):535-539
The ground state and excited state transfer yields for the 2-neutron pickup channel in the 28Si+68Zn system have been measured explicitly. The recoil mass separator at the nuclear Science Centre, New Delhi was used for the
measurement. A NaI(T1) detector was used for detecting the deexcitation γ’s from the transfer products. The kinematic coincidence technique was employed for the transfer measurement. Simplified coupled
channels calculations show that out of all transfer channels the major contribution to the sub-barrier enhancement comes from
the ground state 2 neutron pickup channel with a ground state Q-value of+1.83 MeV. 相似文献
94.
Bivash R Behera Subinit Roy P Basu M K Sharan S Jena M Satpathy SK Datta L Satpathy ML Chatterjee 《Pramana》1999,53(3):563-566
Time of flight and energy of fission fragments were measured using pulsed beam. Fission fragment mass and energy integrated
angular distributions were extracted. Fission fragment anisotropy was explained in the framework of saddle point model. 相似文献
95.
96.
T Madhusoodhanan Samit Mandal MP Sathyavathiamma Ramani NG Puttaswamy TS Mudhole A Mandal DK Avasthi R Shyam SK Datta 《Pramana》1999,53(3):541-544
The inclusive and exclusive measurements were carried out for 7Li projectile breakup on 27Al target at 48 MeV. In the inclusive data we have observed a broad peak around the beam velocity for alphas and tritons.
The exclusive data for alpha-triton coincidences show good agreement with the post-form DWBA theory of breakup reactions. 相似文献
97.
Measurement of elastic and quasielastic reaction cross sections were done in 16O + 118Sn system at two different energies above the barrier. Attempts are being made to understand the results in the framework
of coupled reaction channel model. 相似文献
98.
Burley GA Avent AG Boltalina OV Gol'dt IV Guldi DM Marcaccio M Paolucci F Paolucci D Taylor R 《Chemical communications (Cambridge, England)》2003,(1):148-149
In a first example of a trannulene-based donor-acceptor dyad visible light photoexcitation generates a long-lived (870 ns) charge-separated state. 相似文献
99.
Square lattice models for the general dimer and trimer problems are considered. A secondary lattice for the dimer problem is constructed, and a double square Kikuchi calculation produces an athermal molecular freedom within 2% of the known exact result. With interactions, departures from ideality of mixing entropy and vapour pressure are calculated at different temperatures, and an asymmetrical phase separation occurs at a reduced temperature 0.08. The general trimer problem is considered in a single square Kikuchi calculation. A single interaction is included. The molecular freedom and thermodynamic non-ideality of rigid linear, rigid angled and flexible trimers are compared. In the rigid linear case a phase separation occurs at reduced temperature 0.04. The molecular freedom of rigid linear trimers is calculated using higher Kikuchi approximations, and the result agrees well with previous estimates. 相似文献
100.
Gierlich J Gutsmiedl K Gramlich PM Schmidt A Burley GA Carell T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(34):9486-9494
We report the combination of "click chemistry" with PCR by using alkyne-modified triphosphates for efficient and homogeneous labeling of DNA. A series of modified PCR products of different lengths (300, 900, and 2000 base pairs) were prepared by using a variety of alkyne- and azide-containing triphosphates and different polymerases. After intensive screening of real-time PCR methods, protocols were developed that allow the amplification of genes by using these modified triphosphates with similar efficiency to that of standard PCR. The click reaction on the highly modified PCR fragments provided conversion rates above 90 % and resulted in the functionalization of hundreds of alkynes on large DNA fragments with superb selectivity and efficiency. 相似文献