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121.
(trans) 1-Chloro-2-iodoethylene (3), (trans) 1-bromo-2-iodoethylene (4), (trans) 1,2-diiodoethylene (5) and (cis and trans) 1,2-dibromoethylene (11) were reacted under Suzuki, Sonogashira and Negishi cross-coupling conditions using Pd catalysis to obtain mono coupled products. Only olefin template 3 provided the desired coupling products reliably under all reaction conditions. Compound 5 did not provide cross coupled products under any of the reaction conditions used. The Negishi reaction was the only one that worked for templates 4 and 11. Studies indicate that oxidative addition of the most reactive carbon-halogen bond to Pd(0) is followed by elimination of the second halide, when the second halide is a bromide or an iodide. This happens to a much lesser degree when the second halogen is a chloride. 相似文献
122.
Christine GozeDenis V. Kozlov Felix N. CastellanoRaymond Ziessel 《Tetrahedron letters》2003,44(48):8713-8716
The synthesis of novel ruthenium(II) bipyridine or terpyridine complexes bearing an increasing number of pyrene or toluyl moieties is described. The ruthenium complexes are constructed in a first step with ligands bearing the required bromine functions, followed in a second step by stepwise grafting of 1-ethynylpyrene or 4-ethynyltoluene promoted by Pd(0). A complex bearing a protected triethylsilylacetylene function was also prepared. In situ deprotection of this function with K2CO3 and cross-coupling with 1-bromopyrene afforded a soluble complex in which two pyrene moieties are linearly linked via ethynyl spacers to one of the bipyridine ligands. These highly coloured complexes exhibit well defined absorption and emission properties in solution at both rt and 77 K. 相似文献
123.
On the basis of the common feature among the electron transfer process and the ion hydration process as well as the relevant experimental kinetic data of electron transfer reaction,a new accurate hydration potential function scheme for the determination of electron transfer coupling matrix element is presented.The coupling matrix element between two hydrated ions of the reacting system in solution is calculated.The results and the applicability of this scheme are discussed. 相似文献
124.
An investigation of heparinase immobilization 总被引:1,自引:0,他引:1
Bernstein Howard Yang Victor C. Langer Robert 《Applied biochemistry and biotechnology》1987,16(1):129-143
A systematic investigation of the parameters that affect the efficiency of immobilizing heparinase onto cyanogen bromide activated
crosslinked 8% agarose beads was conducted. Two experimental measures, the “fraction bound” and the “fraction retained,” were
used to monitor the coupling efficiency. The fraction bound is the portion of the total initial enzyme that is bound to the
agarose gel. The fraction retained is the fraction of bound enzyme that is active. The product of the two measures indicates
the coupling efficiency. The activity of the immobilized heparinase was measured under conditions free of both internal and
external mass transfer limitations, and thus, the fraction retained represents the true immobilized enzyme activity.
Increasing the degree of activation of the beads results in an increase in the fraction bound, the fraction retained, and
consequently, the coupling efficiency. As the ratio of enzyme solution to gel volume increases from 1.5 to 2.2, the fraction
bound remains constant but the fraction retained decreases (heparinase concentration; 0.15 mg/mL and degree of activation;
9.5 μmol of cyanate esters/g of gel). At volume ratios greater than 2.2, both the fraction bound and the fraction retained
decline continuously. Changing the heparinase concentration in the coupling solution changes the coupling efficiency in a
manner similar to that of the volume ratio change.
When heparin is added during the coupling process, the fraction bound declines as the heparin concentration increases, whereas
the fraction retained increases up to a heparin concentration of 12 mg/mL and decreases thereafter. When arginine, lysine,
and glycine are used to block the unreacted cyanate ester groups after the coupling process, the immobilized heparinase shows
different pH optima of 6.5, 6.9, and 7.2, respectively. Based upon these findings, a protocol to optimize heparinase immobilization
is developed. 相似文献
125.
We present sets of real 3- symbols which correspond to explicitly given irreducible matrix representations for the two double group hierarchies T* C
3
*
and T* C
2
*
. They fit into the formalism exposed in a previous paper [1] on the general theory of 3- symbols and coupling coefficients and illustrate much of the discussion in a subsequent one [2] treating the particular properties of the double groups. 相似文献
126.
A Pyrex glass capillary (0.4 mm internal diameter) microreactor was developed and used for Suzuki coupling reactions. Capillary-microreactors are more attractive than photolithographic microfluidic devices in terms of simplicity, low cost and ease of handling. Compared with the conventional synthesis procedure, our approach of using a capillary-microreactor offers a convenient and highly efficient means to optimize reaction conditions and the performance of catalysts. The procedure exhibits good precision, reproducibility and high reaction yield for a range of reactants investigated. 相似文献
127.
A continuous flow, microwave-assisted, parallel-capillary microreactor has been developed. Libraries of drug candidates were prepared on the milligram scale with this reactor by injecting plugs of reagents from separate syringes into common reaction capillaries, thereby producing discrete compounds in excellent yield and purity. Microwave irradiation provides the necessary energy that existing room-temperature microreactor technology lacks for higher activation barrier transformations, producing the required amounts of desired compounds in minutes or less. 相似文献
128.
Quantum equations of motion describing the energy transfer dynamics via intramolecular anharmonic coupling are presented and solved numerically. Dynamical features of the average excitations of a homogeneous system (SF6) and a heterogeneous system (H/W) are quantitatively discussed in terms of the intramolecular vibrational relaxation (IVR) rates. Possible mechanisms of surface-enhanced desorption via low-power laser radiation are proposed.This work was supported in part by the Office of Naval Research, the Air Force Office of Scientific Research (AFSC), United States Air Force, under Grant AFOSR-82-0046 and the National Science Foundation under Grant No. CHE-8022874Camille and Henry Dreyfus Teacher-Scholar (1975–82) 相似文献
129.
Robert Kolodziuk Mustapha Tollabi Catherine Goux-Henry Denis Sinou 《Journal of organometallic chemistry》2003,687(2):384-391
Carbohydrate-substituted phosphines are easily obtained in quite good yields by coupling of protected or non-protected d-glucosamine with the corresponding diphenylphosphino acid. These neutral ligands, in association with palladium acetate, are very active catalysts in the Suzuki cross-coupling reaction. The polyhydroxy phosphines are more active than the peracetylated phosphines. The process tolerates electron-rich as well as electron-poor substituents. Excellent turnovers, up to 97?000 are observed. 相似文献
130.
Stereochemistry of 7-aryl-1,7,8,8a-tetrahydro-3(2H)-indolizinones was studied by1H and13C NMR. Complete assignment of1H NMR signals and analysis of1H-1H coupling constants were performed using the iterative PANIC program. Values of3
J
6,7,3
J
7,8endo, and4
J
5,7 allow one to unambiguously identify the correspondingexo- andendo-stereoisomers. For stereoisomers with exo-orientation of H(7), complete assignment of13C NMR signals was performed on the basis of analysis of the13C-1H coupling constants using two dimensional heteronuclear shift-correlating spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 591–593, March, 1996. 相似文献