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991.
Mohit L. Deb Bhaskar Deka Iftakur Rahman Pranjal K. Baruah 《Tetrahedron letters》2018,59(50):4430-4433
Here we report l-proline catalyzed 3-component reaction of indoles, aldehydes and N-substituted anilines in water as solvent at room temperature for the synthesis of 3-(α,α-diarylmethyl)indoles. The reaction is in fact a Michael addition of N-substituted anilines to alkylideneindolenines. The reaction is very clean, high yielding and having broad substrate scope. A tentative mechanism is proposed. 相似文献
992.
Benzo[a]pyrene is a carcinogen often present in diesel. For pervaporative removal of benzo[a]pyrene from n-tetradecane, representing a model diesel composition, both conventional as well as statistically designed experimental methods have been carried out. The effect of membrane composition, thickness, the effect of membrane pretreatment time and operating temperature on pervaporative separation have been investigated by response surface methodology, RSM for efficient permeation of target compound. The suitable membrane has been further used to study the effect of different physico-chemical parameters on permeation conventionally. RSM has also been applied to optimize the operational conditions of pervaporation process to maximize the response, i.e., the pervaporation separation index. With the design of experiments, the quadratic response surface models have been developed to link the response with input variables via mathematical relationships. The maximum value of Pervaporation Separation Index obtained is 1.9654 kg m?2 h?1. The optimized process condition’s run time is 10.79 h, the feed PAH concentration is 166.34 ppm with a permeate side pressure of 0.73 mmHg and an operating temperature of 451.25 K. 相似文献
993.
N. C. Dutta 《Journal of Radioanalytical and Nuclear Chemistry》1997,224(1-2):173-175
A study of fixation of cobalt on the crystalline matrix of titania by co-precipitation was carried out. The tracer level solid-liquid distribution of60Co over preformed hydrous titania showed an appreciable uptake of 71%. Macro amounts of Co2+ ions were precipitated along with Ti(IV) hydroxide (pH 8–9) and a maximum loading of 29 wt% was observed. The Soxhlet leachabilities of the calcined mixed mass, heated at 1000 °C, were found to be in the order of 10–1 g·m–2·d–1 and the observation of structural changes of the original host matrix of titania revealed the fixation of cobalt in the mineral assemblage of CoTiO3 (rhombohedral) and the rutile form of titania. 相似文献
994.
995.
The quasi-particle-phonon model of pre-equilibrium decay (QP Ph M PED) is proposed. Within this model, intermediate states are specified by the number of quasi-particles, quasi-holes and phonons. In describing nuclear relaxation we consider two types of internuclear transitions with the change in exciton number byN
ex=0, ±2 and number of phononN
ph=±1. The mixed densities of intermediate states(N
ex,N
ph,E) have been determined. An analysis has been made of the structure of the hard part of the emission spectrum in the60Ni(p,p) and120Sn(p,p) reaction at p=62 MeV. This analysis suggests the importance of taking into account the transitions withN
ph=+1, along with the transitions withN
ex= +2. 相似文献
996.
Kaushik Dutta A. S. Brar 《Journal of polymer science. Part A, Polymer chemistry》1999,37(21):3922-3928
The configurational assignment of poly(vinylpyrrolidone) (PVP) prepared by peroxide-initiated solution polymerization was studied by the combination of one- and two-dimensional NMR spectroscopy. The broad and overlapping 1H-NMR and 13C{1H}-NMR spectra of PVP were assigned to the configurational triad, pentad (CH, 2CH2, 3CH2, and 4CH2 regions), and tetrad (β-CH2 region) sequences. The configurational assignments of the various carbon resonances were confirmed with the help of two-dimensional experiments such as heteronuclear single quantum correlation (HSQC), heteronuclear single quantum correlation–total correlation spectroscopy (2-D HSQC–TOCSY). The various geminal and vicinal couplings within the configurational sequences were assigned with the help of total correlation spectroscopy (TOCSY low mixing time). The propagation pathway was studied using the 13C{1H}-NMR (carbonyl carbon) and 15N{1H}-NMR spectra. The 15N{1H} resonance signals were assigned to pentad-level configurational sequences. The results obtained by the analysis of the area under the resonance signals confirmed that poly(vinylpyrrolidone) obeys Bernoullian statistics. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3922–3928, 1999 相似文献
997.
998.
S. Adhikari P. Dutta S.P. Bhattacharyya 《International journal of quantum chemistry》1996,59(2):109-117
A local grid method proposed earlier is used to model chemical dynamical events in more than one dimension. Two different mean-field routes are applied to model problems representing dynamics of isomerization, H+-ion transfer, energy transfer, etc. The methods are seen to work with equal facility for both time-dependent and time-independent potentials. © 1996 John Wiley & Sons, Inc. 相似文献
999.
1000.
An enzyme which is capable of catalyzing C–H amination reactions is considered to be a dream tool for chemists due to its pharmaceutical potential and greener approach. Recently, the Arnold group achieved this feat using an engineered CYP411 enzyme, which further undergoes a random directed evolution which increases its efficiency and selectivity. The present study provides mechanistic insight and the root cause of the success of these mutations to enhance the reactivity and selectivity of the mutant enzyme. This is achieved by means of comprehensive MD simulations and hybrid QM/MM calculations. The study shows that the efficient C–H amination by the engineered CYP411 is a combined outcome of electronic and steric effects. The mutation of the axial cysteine ligand to serine relays electron density to the Fe ion in the heme, and thereby enhances the bonding capability of the heme-iron to the nitrogen atom of the tosyl azide. In comparison, the native cysteine-ligated P450 cannot bind the tosyl azide. Additionally, the A78V and A82L mutations in P411 provide ‘bulk’ to the active site which increases the enantioselectivity via a steric effect. At the same time, the QM/MM calculations elucidate the C–H amination by the iron nitrenoid, revealing a mechanism analogous to Compound I in the native C–H hydroxylation by P450.Computer simulation method reveals the mechanism of C–H amination reaction due to a single site mutation. 相似文献