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111.
Microstructural studies and analysis of internal stresses in Co–TiC composites prepared by the spontaneous crystallization method (high-temperature solution technique) have been performed. Metallographic observations and X-ray phase analysis of the obtained Co–TiC composite ingots were carried out. The microstructure of the Co–TiC interface was studied using transmission electron microscopy and high-resolution transmission electron microscopy. The Co–TiC composites were also subjected to numerical analysis by the finite-element method. The presented results of calculations include the analysis of the state of internal stresses generated in the composite during its cooling from the crystallization temperature to room temperature. On the basis of these results the internal stress distribution and its level were determined for the obtained Co–TiC composites. 相似文献
112.
P. M.C. de Oliveira S. Moss de Oliveira D. Stauffer S. Cebrat A. Pękalski 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):245-254
We discovered a dynamic phase transition induced by sexual
reproduction. The dynamics is a pure Darwinian rule applied to diploid
bit-strings with both fundamental ingredients to drive Darwin's
evolution: (1) random mutations and crossings which act in the sense of
increasing the entropy (or diversity); and (2) selection which acts in
the opposite sense by limiting the entropy explosion. Selection wins
this competition if mutations performed at birth are few enough, and
thus the wild genotype dominates the steady-state population. By slowly
increasing the average number m of mutations, however, the
population suddenly undergoes a mutational degradation precisely at a
transition point mc. Above this point, the “bad”
alleles (represented by 1-bits) spread over the genetic pool of the
population, overcoming the selection pressure. Individuals become
selectively alike, and evolution stops. Only below this point, m < mc, evolutionary life is possible.
The finite-size-scaling behaviour of this transition is
exhibited for large enough “chromosome” lengths L, through
lengthy computer simulations. One important and surprising observation
is the L-independence of the transition curves, for large L.
They are also independent on the population size. Another is that mc is near unity, i.e. life cannot be stable with much more
than one mutation per diploid genome, independent of the chromosome
length, in agreement with reality. One possible consequence is that an
eventual evolutionary jump towards larger L enabling the storage
of more genetic information would demand an improved DNA copying
machinery in order to keep the same total number of mutations per
offspring. 相似文献
113.
114.
Magdalena Obłoza Dr. Łukasz Łapok Dr. Tomasz Pędziński Prof. Katarzyna M. Stadnicka Prof. Maria Nowakowska 《Chemphyschem》2019,20(19):2482-2497
A series of novel aza-BODIPY dyes substituted with p-(dimethylamino)phenyl groups were synthesized and their spectral and electrochemical properties were compared. In particular, the impact of p-(Me2N)Ph- groups on these characteristics was of consideration. For two aza-BODIPYs studied, a near-IR absorption band was observed at circa λabs=796 nm. Due to the pronounced intramolecular charge transfer (ICT) exerted by the presence of strongly electron-donating p-(Me2N)Ph- substituents, the compounds studied were weakly emissive with the singlet lifetimes (τS) in the picosecond range. Nanosecond laser photolysis experiments of the brominated aza-BODIPYs revealed T1→Tn absorption spanning from ca. 350 nm to ca. 550 nm with the triplet lifetimes (τT) ranged between 6.0 μs and 8.5 μs. The optical properties of the aza-BODIPYs studied were pH-sensitive. Upon protonation of the dimethylamino groups with trifluoroacetic acid in toluene, a stepwise disappearance of the NIR absorption band at λabs=790 nm was observed with the concomitant appearance of a blue-shifted absorption band at λabs=652 nm, which was accompanied by a prominent emission band at λfl=680 nm. The transformation from a non-emissive to an emissive compound is associated with the inhibition of the ICT. As estimated by CV/DPV measurements, all aza-BODIPYs studied exhibited two irreversible oxidation and two quasi-reversible reduction processes. All compounds studied exhibit extremely high photostability and thermal stability. 相似文献
115.
Kęstutis Arlauskas Arūnas Baronas Nerijus Nekrašas Karolis Kazlauskas 《Journal of Non》2008,354(19-25):2160-2163
Using three electrode vacuum system for glow discharge of 5% SiH4 + 95% Ar gas mixture together with thermal evaporation of phosphorus or boric aced, the n- and p-type a-Si:H layers have been deposited. By co-evaporation of phosphorus or boric aced the conductivity of a-Si:H layers was changed in 10?11–10?3 Ω?1 cm?1 or 10?11 –10?8 Ω?1 cm?1 range, respectively. Blends of a-Si:H and tris-(8-hydroxyquinoline) aluminum (Alq3) have been vacuum-deposited by simultaneous glow discharge of 5% SiH4 + 95 % Ar gas mixture and thermal co-evaporation of Alq3. Photoluminescence spectrum of a-Si:H/Alq3 blend coincident with one of Alq3 was observed at room temperature. 相似文献
116.
Dr. Swati Deswal Rishukumar Panday Dr. Dipti R. Naphade Prashant Dixit Dr. Balu Praveenkumar Dr. Jan K. Zaręba Prof. Dr. Thomas D. Anthopoulos Prof. Dr. Satishchandra Ogale Prof. Dr. Ramamoorthy Boomishankar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(33):e202200751
Bismuth containing hybrid molecular ferroelectrics are receiving tremendous attention in recent years owing to their stable and non-toxic composition. However, these perovskite-like structures are primarily limited to ammonium cations. Herein, we report a new phosphonium based discrete perovskite-like hybrid ferroelectric with a formula [Me(Ph)3P]3[Bi2Br9] ( MTPBB ) and its mechanical energy harvesting capability. The Polarization-Electric field (P-E) measurements resulted in a well-defined ferroelectric hysteresis loop with a remnant polarization value of 2.1 μC cm−2. Piezoresponse force microscopy experiments enabled visualization of the ferroelectric domain structure and evaluation of the piezoelectric strain coefficient (d33) for an MTPBB single crystal and thin film sample. Furthermore, flexible devices incorporating MTPBB in polydimethylsiloxane (PDMS) matrix at various concentrations were fabricated and explored for their mechanical energy harvesting properties. The champion device with 20 wt % of MTPBB in PDMS rendered a maximum peak-to-peak open-circuit voltage of 22.9 V and a maximum power density of 7 μW cm−2 at an optimal load of 4 MΩ. Moreover, the potential of MTPBB -based devices in low power electronics was demonstrated by storing the harvested energy in various electrolytic capacitors. 相似文献
117.
Majchrzak-Kucęba Izabela Ściubidło Aleksandra 《Journal of Thermal Analysis and Calorimetry》2019,138(6):4139-4144
Journal of Thermal Analysis and Calorimetry - The paper presents the effect of the tabletting pressure and time on the chemical structure and crystallinity of the CuBTC and MIL-53(Al)... 相似文献
118.
The Model of “Minimal Oscillator” Derived from the Kinetic Mechanism of the H2O2–NaSCN–NaOH–CuSO4 Dynamical System
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Dissipative chemical reactions, which involve oscillatory variations of the concentrations of the intermediates in time, are usually characterized with complicated kinetic mechanisms. However, the essential source of the oscillations can often be reduced to only a few reaction steps providing the alternative domination of the positive and negative feedback loops. In an extreme case such a reduction leads to the so–called “minimal oscillator,” the concept used in the past for the well‐known Belousov‐Zhabotinsky (BZ) reaction. In the present work, we construct such a minimal system for the (discovered by M. Orbán) H2O2–NaSCN–NaOH–CuSO4 homogeneous oscillator, in which instabilities originate from kinetic mechanism substantially different from that proposed for the BZ system. The methodology involves intuitive analysis of the reaction mechanism, supported by numerical calculations and spectrophotometric measurements. We show how the actual, only three‐variable model evolves from our previously elaborated: nine‐ and five–variable mechanisms and prove that its further reduction to two–variable one is not possible. Thus the present work is a final step in our searches for the “minimal Orbán oscillator”. 相似文献
119.
Michnik Anna Kiełboń Agnieszka Duch Klaudia Sadowska-Krępa Ewa Pokora Ilona 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6739-6743
Journal of Thermal Analysis and Calorimetry - The results of studies of physiological fluids by differential scanning calorimetry (DSC) for the purpose of diagnosis and monitoring of diseases are... 相似文献
120.
Marlena Pięta Jacek Kędzia Dorota Kowalczyk Jakub Wojciechowski Wojciech M. Wolf Tomasz Janecki 《Tetrahedron》2019,75(17):2495-2505
An efficient, versatile, enantioselective synthesis of 1,3-disubstituted and 1,3,6-trisubstituted 5-methylidenedihydrouracils applying Horner-Wadsworth Emmons methodology was developed. Starting 1,3-disubstituted 5-diethoxyphosphoryluracils were subjected to reduction of the double bond or addition of various Grignard reagents and obtained Horner-Wadsworth Emmons reagents were used for the olefination of formaldehyde. Enantioselective synthesis of 1,3,6-trisubstituted 5-methylidenedihydrouracils was accomplished by introducing (R,R)- or (S,S)-di(1-phenylethylamino)phosphoryl groups as chiral auxiliary. Additions of Grignard reagents in the presence of these groups were highly and complimentary diastereoselective (de?~?80%). Further separation of the diastereomeric mixtures by column chromatography enabled synthesis of (R)- and (S)-1,3,6-trisubstituted-5-methylidenedihydrouracils with ee?≥?98%. Furthermore, absolute configuration of the adducts and final products was established using single crystal X-ray analysis. Stereochemical course of the addition reactions is also discussed. 相似文献