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51.
A new phosphorylcholine, (6-hydroxy) hexyl-2-(trimethylammonio) ethyl phosphate (HTEP), was synthesized andcharasterized. Segmented polyurethane (SPU) containing phosphorylcholine structure was synthesized based ondiphenylmethane diisocyanate (MDI), soft segment polytetramethylene glycol (PTMG) and HTEP, with 1,4-butanediol (BD)as a chain extender. The existence of phosphorylcholine structure on the surface of SPU was revealed by attenuated totalreflectance Fourier transform infrard spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and water contactangle measurements. The blood compatibilities of the polymers were evaluated by hemolytic testing and a platelet-richplasma (PRP) adhesion experiment, which was viewed by scanning electron microscopy (SEM) with polyurethane as areference. The novel segmented polyurethane containing phosphorylcholine structure showed improved blood compatibility. 相似文献
52.
A three-phase model, comprising crystalline, mobile amorphous, and rigid amorphous fractions (χ
c, χ
MA, χ
RA, respectively) has been applied in the study of semicrystalline Nylon-6. The samples studied were Nylon-6 alpha phase prepared
by subsequent annealing of a parent sample slowly cooled from the melt. The treated samples were annealed at 110°C, then briefly
heated to 136°C, then re-annealed at 110°C. Temperature-modulated differential scanning calorimetry (TMDSC) measurements allow
the devitrification of the rigid amorphous fraction to be examined.
We observe a lower endotherm, termed the ‘annealing’ peak in the non-reversing heat flow after annealing at 110°C. By brief
heating above this lower endotherm and immediately quenching in LN2-cooled glass beads, the glass transition temperature and χ
RA decrease substantially, χ
MA increases, and the annealing peak disappears. The annealing peak corresponds to the point at which partial de-vitrification
of the rigid amorphous fraction (RAF) occurs. Re-annealing at 110°C causes the glass transition and χ
RA to increase, and χ
MA to decrease. None of these treatments affected the measured degree of crystallinity, but it cannot be excluded that crystal
reorganization or recrystallization may also occur at the annealing peak, contributing to the de-vitrification of the rigid
amorphous fraction.
Using a combined approach of thermal analysis with wide and small angle X-ray scattering, we analyze the location of the rigid
amorphous and mobile amorphous fractions within the context of the Heterogeneous and Homogeneous Stack Models. Results show
the homogeneous stack model is the correct one for Nylon-6. The cooperativity length (ξA) increases with a decrease of rigid amorphous fraction, or, increase of the mobile amorphous fraction. Devitrification of
some of the RAF leads to the broadening of the glass transition region and shift of T
g. 相似文献
53.
54.
Chetsumon Aparat Umeda Fusako Maeda Isamu Yagi Kiyohito Mizoguchi Tadashi Miura Yoshiharu 《Applied biochemistry and biotechnology》1998,(1):249-256
A photobioreactor was constructed using anchored polyurethane foam strips (1 x 1 x 40 cm) fixed onto a stainless-steel ring
to prevent flotation, as a biomass support material (BSM). This type of reactor was named a seaweed-type bioreactor. A filamentous
cyanobacterium, Scytonema sp. TISTR 8208, which produces a novel cyclic dodecapeptide antibiotic, was immobilized in seaweed-type
photobioreactor and cultivated with air containing 5% CO2 sparged at a gas flow rate of 250 mL/min under illumination at a light intensity of 200 μmol photon m-2s-1. The antibiotic produced in the seaweed-type photobioreactor was purified by HPLC and examined regarding its spectrum and
mode of action. The antibiotic effectively inhibited the growth of Gram-positive bacteria, pathogenic yeasts, and filamentous
fungi, but it had only a weak effect on Gram-negative bacteria. Scanning electron micrograph analysis showed that the most
characteristic change was swelling of the cells after exposure to the antibiotic. The antibiotic seems to alter the conformation
of the microbial cell membrane, thereby changing its permeability, leading to osmotic shock. 相似文献
55.
Tarek M. Madkour Rasha A. Azzam 《Journal of polymer science. Part A, Polymer chemistry》2002,40(14):2526-2536
Polyurethane elastomers of a controlled molecular architecture were synthesized using a two‐step polymerization technique. The building blocks of the elastomeric materials included urea–urethane prepolymers end‐capped with diisocyanate groups and had an exact number of urea groups at both ends. Two‐dimensional bifurcated hydrogen‐bonding networks incorporating the urea groups were, with differential scanning calorimetric and dynamic mechanical thermal analyzer techniques, responsible for the increase in the glass‐transition temperature (Tg) of the hard block and sharp interface morphology between the pure “hard” domains and pure “soft” domains. The higher extent of the phase separation between the two phases contributed to higher elastic moduli for the hard blocks and higher tensile strength for the elastomeric samples. Higher elongation values were attributed to the liberation of the elastomeric chain ends that otherwise would have been constrained in the interface region. The higher Tg values of the hard blocks corresponded to an increase in the hardness values and a decrease in the tear‐strength values. The increase in the amount of urea groups within the hard segments, as a result of the increased amount of water and blowing catalyst, resulted in elastomeric foams with higher open‐cell content. This resulted in lower resilience values as measured using the pendulum rebound test and was attributed to the ability of the open cells to absorb and dissipate energy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2526–2536, 2002 相似文献
56.
Nickel foam and five nickel foam-based composite electrodes were prepared for being used as anode materials for the electrooxidation
of methanol in KOH solution containing 0.1 and 1.0 M of methanol. The layered electrodes composed of nickel foam, platinum
nanoparticles, polyaniline (PANI) and/or porous carbon (C) prepared in various assemblies. As shown by SEM analysis, depending
on the preparation conditions, the electrodes of different morphologies were obtained. Using the cyclic voltammetry method,
the oxidation of methanol on nickel foam electrode was observed in the potential range 0.4 V ↔ 0.7 V, where the Ni(OH)2/NiOOH transformation occurred. The presence of Pt particles in electrode gave rise to the increase in electrocatalytic activity
in this potential range. For electrodes containing dispersed platinum catalyst (Ni/Pt, Ni/PANI/Pt and Ni/C/Pt), the oxidation
of methanol was noted also in the potential range −0.5 V ↔ 0.1 V. The electrocatalytic activities of the examined electrodes
toward methanol oxidation at low potentials were in order Ni/Pt > Ni/C/Pt > Ni/PANI/Pt, whereas at high potentials in order
Ni/PANI/Pt > Ni/Pt> Ni/C/Pt > Ni. Among the examined electrodes, the most resistant to cyclic poisoning appeared to be the
Ni/C/Pt electrode.
Presented at the 4Th Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005 相似文献
57.
泡沫塑料动态快速分离富集金方法的研究 总被引:5,自引:2,他引:5
本文系统研究了泡沫塑料动态快速分离富集金的方法。对泡沫塑料柱的处理方法,再生及主要共存离子干扰的消除等均做了较详细的研究。提出了一种简便,不控速的金分离富集的方法。该法用于分析0.051~3.59g/t四种不同含量的金标样,结果与推荐值吻合,5次分析结果,相对标准偏差<5%,同时,可用泡沫塑料柱当天连续使用分析拿标样,回收率为93%—109%。 相似文献
58.
通过在聚氨酯泡沫模板中沉积多壁碳纳米管,用炭的预制体酚醛树酯将碳纳米管粘接固定在一起,经过高温碳化过程制备了碳纳米管-炭复合泡沫材料。红外光谱结果表明利用浓硫酸和浓硝酸的混合溶液处理可以使复合泡沫表面活化形成羧基和羟基,从而使复合泡沫具备较强的分子吸附能力。扫描电镜和氮吸附实验表明这种复合泡沫同时具备大孔和介孔,大孔能够满足流体自由流动的通畅性,介孔可以满足中分子的吸附需要。对标定物维生素B12的吸附实验证明这种复合泡沫对中分子量的生化分子具有有效的吸附能力。这种宏观尺寸的泡沫材料与传统的颗粒状活性炭相比具有简化工艺,提高吸附效率的应用潜力。 相似文献
59.
Francisco García-Moreno Paul H. Kamm Tillmann R. Neu John Banhart 《Journal of synchrotron radiation》2018,25(5):1505-1508
An experimental setup has been developed that allows for capturing up to 25 tomograms s?1 using the white X‐ray beam at the experimental station EDDI of BESSY II, Berlin, Germany. The key points are the use of a newly developed, precise and fast rotation stage, a very efficient scintillator and a fast CMOS camera. As a first application, the foaming of aluminium alloy granules at 923 K was investigated in situ. Formation and growth of bubbles in the liquid material were observed and found to be influenced by the limited thermal conductivity in the bulk granules. Changes that took place between two tomographic frames separated in time by 39 ms could be detected and analysed quantitatively. 相似文献
60.