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排序方式: 共有4717条查询结果,搜索用时 15 毫秒
991.
Dr. Baolin Wang Dr. Yongxin Li Dr. Rakesh Ganguly Prof. Dr. Richard D. Webster Prof. Dr. Rei Kinjo 《Angewandte Chemie (International ed. in English)》2018,57(26):7826-7829
One‐electron oxidation of 1,4,2,5‐diazadiborinine 1 has been studied. While the reaction of 1 a bearing phenyl groups on the B atoms with AgAl{OC(CF3)3}4 afforded a complex mixture, the same oxidation reaction with 1 b featuring bulky mesityl substituents on the B atoms rendered the corresponding cation radical 2 b as an isolable species. X‐ray diffraction analysis, EPR spectroscopy, and DFT calculations of 2 b revealed the delocalization of the unpaired electron over the entire π‐system of 2 b , as well as a large spin density (0.76 in total) on the two equivalent boron atoms. The chemical trapping reaction of 2 b with p‐benzoquinone and triphenyltin hydride afforded the dicationic species 3 containing two newly formed B?O bonds and the monocationic product 2b‐H containing a B?H bond, respectively, thus confirming the boron‐centered radical reactivity of 2 b . 相似文献
992.
《先进技术聚合物》2018,29(2):758-766
In this study, epoxy coatings were modified by adding various compositions of B4C particles. In order to achieve proper dispersion of particles in the epoxy coating and increasing chemical interactions between particles and polymeric coating, the surface of the B4C particles was treated with γ‐(2,3‐epoxypropoxy) propytrimethoxysilane (KH560). The surface modification and microstructure of B4C were characterized by Fourier transform infrared, X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. Electrochemical impedance spectroscopy was also used to evaluate the impedance of coatings. The results revealed that the KH560 not only enhanced the interaction between B4C particles and epoxy resin but also exhibited a remarkable ability to improve the anticorrosion performance of epoxy resin. The epoxy coating with the 3 wt% B4C‐KH560 particles exhibited the best anticorrosion performance, which can be attributed to the best uniform dispersion of the B4C‐KH560 particles, and the particles effectively block the aggressive species (Cl−, O2, and H2O) from the coating. 相似文献
993.
Yuhua Zhong Luchong Zhang Andreas Fischer Liang Wang Dietmar Drummer 《高分子科学杂志,A辑:纯化学与应用化学》2018,55(1):17-23
A novel thermally conductive Polyamide 6 (PA6) with good fire resistance was prepared by introducing a phosphorous-nitrogen flame retardant (FR) and platelet-shaped hexagonal boron nitride (hBN) into the matrix. With high thermal conductivity and good flame retardancy, the material is suitable for applications in electronic and electrical devices. The limiting oxygen index (LOI) changes for various loadings content of FR. However this formulation still does not show an ideal fire resistance, due to the appearance of melt dripping behavior during the UL 94 test. With the extra introduction of 3 vol% and 5 vol% hBN, the melt dripping behavior during the burning process completely disappeared. The hBN also increased the thermal conductivity. Furthermore PA6 compounded with FR and hBN showed a better thermal stability than neat PA6. The morphology of the char residues was investigated by scanning electron microscopy (SEM). The flaky hBN acted as the framework in the char structure and the rigid hBN could effectively break the bubble-shaped char on the surface of the residues which resulted in the enhancement of the strength and compactness of the char. 相似文献
994.
Layer-Structured Ti Doped O3-Na1-xCr1-xTixO2(x=0, 0.03, 0.05) with Excellent Electrochemical Performance as Cathode Materials for Sodium Ion Batteries 下载免费PDF全文
Layer-structured O3 type cathode materials Na1-xCr1-xTixO2(x=0, 0.03, 0.05) are fabricated by a thermo-polymerization method. The structures and morphologies are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. It has been found that the appropriate Ti doping effectively leads to the formation of uniform morphology. As a cathode, the x=0.03 sample delivers a quite high discharge capacity of 110 mAh/g at 32 C in the voltage range from 2.0 V to 3.6 V (vs. Na/Na+) and with a capacity retention of 96% after 100 cycles at 0.2 C. The Na//Na0.97Cr0.97Ti0.03O2 cell exhibits very high coulombic e ciency (above 96%). All these results suggest that Na0.97Cr0.97Ti0.03O2 is very promising for high-rate sodium ion batteries. 相似文献
995.
996.
Highlights on the Road towards Highly Emitting Solid‐State Luminophores: Two Classes of Thiazole‐Based Organoboron Fluorophores with the AIEE/AIE Effect
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Kseniya I. Lugovik Alexander K. Eltyshev Polina O. Suntsova Dr. Pavel A. Slepukhin Dr. Enrico Benassi Prof. Nataliya P. Belskaya 《化学:亚洲杂志》2018,13(3):311-324
Developing a novel, small‐sized molecular building block that may be capable of emitting light in the solid state is a challenging task and has rarely been reported in the literature. BF2‐containing dyes seem to be promising candidates towards this aim. Two series of new N^NBF2 complexes showing aggregation‐induced emission (AIE) and aggregation‐induced emission enhancement (AIEE) were designed and synthesized by means of a new protocol, which improved on the traditional method by employing microwave irradiation. The optical and photophysical properties of the BF2 complexes were investigated in depth. The synthesized complexes showed fluorescence in both solution and the solid state and, in a mixture of tetrahydrofuran/water, may aggregate into fluorescent nanoparticles. The experimental investigation was supported by quantum mechanical calculations. Their availability, stability, large Stokes shifts, and aggregation capabilities, along with their solid‐state emission capability, render this new class of BF2 complexes promising AIEE/AIE fluorophores for further applications in the fields of fluorescence imaging and materials science. 相似文献
997.
《International journal of quantum chemistry》2018,118(10)
A new series of divalent boron‐rare gas cations (Rg = He ∼ Rn, n = 1–4) have been predicted theoretically at the B3LYP, MP2, and CCSD(T) levels to present the structures, stability, charge distributions, bond natures, and aromaticity. The Rg B bond energies are quite large for heavy rare gases and increase with the size of the Rg atom. Because of steric hindrance new Rg atoms introduced to the B4 ring will weaken the Rg B bond. Thus in the Rg B bond has the largest binding energy 90–100 kcal/mol. p‐ has a slightly shorter Rg B bond length and a larger bond energy than o‐ . NBO and AIM analyses indicate that for the heavy Rg atoms Ar ∼ Rn the B Rg bonds have character of typical covalent bonds. The energy decomposition analysis shows that the σ‐donation from rare gases to the boron ring is the major contribution to the Rg B bonding. Adaptive natural density partitioning and nuclear‐independent chemical shift analyses suggest that both and have obvious aromaticity. 相似文献
998.
Densities, heat capacities and conductivities of water-surfactant--cyclodextrin (-CD) ternary systems were determined at 25°C. The surfactants studied were sodium dodecylsulfate (NaDS) and dodecyltrimethylammonium bromide (DTAB). From conductivity data, apparent critical micelle concentrations (cmc*) and degree of ionization of micelles were obtained at a fixed -CD concentration (mCD). From the cmc* value and that in water (cmc) the stoichiometry of the surfactant--CD complex was calculated. At a given mCD, the apparent molar volume V,CD and heat capacity C,CD of -CD in the two surfactants were calculated as functions of surfactant concentration mS. For both NaDS and DTAB, V,CD increases with mS up to about the cmc beyond which it decreases to a constant value at high mS, the opposite is observed for C,CD. With NaDS, a jump in the C,CD vs, mS trend was detected and ascribed to a structural NaDS micellar transition. The apparent molar volume VS and heat capacity CS of NaDS and DTAB in the water--CD mixture 0.017 m were also obtained. From these properties and those in pure water, the volume VS and heat capacity CS of transfer of the surfactant from water to water+-CD mixture as functions of mS were calculated. For both surfactants, the VS vs. mS trends increase to the cmc and then decrease in a monotonic manner, whereas CS increases regularly with mS in the pre-micellar region and is essentially constant in the post-micellar region. The VS vs. mS trends were qualitatively explained in terms of dispersed, complexed and micellized surfactant contributions. 相似文献
999.
We report a novel separation method that is applicable to both DNA and protein samples, based on electrophoresis in a three-dimensional (3-D) geometry. In contrast to conventional electrophoresis, samples are applied in a two-dimensional, planar array to one of the surfaces of a 3-D geometry separation medium. Loading onto a plane results in a very high sample capacity. Sample migration and separation occur along the third spatial dimension, which is perpendicular to the loading plane. The key problem of electrophoresis in a 3-D geometry separation setup is that temperature gradients are caused by Joule's heat, affecting the electrical conductivity and viscosity of the separation medium. A means of achieving straight sample migration under these circumstances is to force heat flow through the separation medium parallel to the axis of sample migration. This can be done by dissipating the heat via the electrode sides of the gel and blocking any other heat transfer. The separation of DNA and proteins by this method has been tested using agarose gel electrophoresis, polyacrylamide gel electrophoresis, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Data were acquired off-line by conventional staining methods as well as on-line by detection of laser-induced fluorescence. We describe how to excise samples from the separation medium for preparative purposes. Possible unique applications of this 3-D geometry electrophoresis separation method are also discussed. 相似文献
1000.
Jaehwan Kim Niangui Wang Yi Chen Sun-Kon Lee Gyu-Young Yun 《Cellulose (London, England)》2007,14(3):217-223
In an earlier work we reported the discovery of cellulose as a smart material that can be used in sensors and actuators. While
the cellulose-based Electro-Active Paper (EAPap) actuator has many merits – lightweight, dry condition, biodegradability,
sustainability, large displacement output and low actuation voltage – its performance is sensitive to humidity. We report
here on an EAPap made with a cellulose and sodium alginate that produces its maximum displacement at a lower humidity level
than the earlier one. To fabricate this EAPap, we dissolved cellulose fibers into a aqueous solution of NaOH/urea. Sodium
alginate (0, 5 or 10% by weight) was then added to this cellulose solution. The solution was cast into a sheet and hydrolyzed
to form a wet cellulose-sodium alginate blend film. After drying, a bending EAPap actuator was made by depositing thin gold
electrodes on both sides of it. The performance of the EAPap actuator was then evaluated in terms of free displacement and
blocked force with respect to the actuation frequency, activation voltage and content of sodium alginate. The actuation principle
is also discussed. 相似文献