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41.
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The combined derivative spectrophotometry developed in this paper is a new method, which can be used to determine multicomporent mixture simultaneously and may improve the sensitivity and accuracy of the measurement remarkably. Two practical tests were carried out to verify the correctness of the theory, and the results are satisfactory. 相似文献
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44.
Photochemical degradation of environmentally persistent perfluorooctanoic acid (PFOA) in the presence of Fe(Ⅲ) 总被引:1,自引:0,他引:1
Yuan Wang~ 《中国化学快报》2008,19(3):371-374
Environmentally persistent and bioaccumulative perfluorooctanic acid (PFOA) was difficult to be decomposed under the irradiation of 254 nm UV light. However, in the presence of 80μmol/L Fe(Ⅲ), 80% of PFOA with initial concentration of 48μmol/L (20 mg/L) was effectively degraded and 47.8% of fluorine atoms in PFOA molecule were transformed into inorganic fluoride ion after 4 h reaction. Shorter chain perfluorocarboxylic acids bearing C3-C7 and fluoride ion were detected and identified by LC/MS and IC as the degradation products in the aqueous solution. It was proposed that complexes of PFOA with Fe(Ⅲ) initiated degradation of PFOA irradiated with 254 nm UV light. 相似文献
45.
Feiguo chen Wei Ge Li Guo Xianfeng He Bo Li Jinghai Li Xipeng Li Xiaowei Wang Xiaolong Yuan 《中国颗粒学报》2009,7(4)
mputing mode. The preliminary applications of this machine in areas of multi-phase flow, molecular dynamics and so on are reported, demonstrating the supercomputer as a paradigm of green computation in new architecture. 相似文献
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Jianyun Wang Dongming Zhang Xixun Yu Changsheng Zhao 《Polymer Degradation and Stability》2010,95(7):1205-1012
Organic and inorganic composite material is becoming a solution on making the mechanical and degradation properties of biomaterial more suited. Porous calcium polyphosphate was immersed into different concentrations of carboxymethyl chitosan before immersing 10% alginate dialdegyde. After freeze-drying, the scaffolds were performed in physiologic saline. At stated day, the weightloss, Ca2+ concentration, pH value and morphology were measured. The biocompatibility of the composite was demonstrated by extract and direct contact tests. As the results showed, the degradation rates of composites were faster, and the compressive strength became bigger because of the cross-linked network formed by Carboxymethyl chitosan (CMC) and alginate dialdehyde (ADA). The pH value of composite was higher than that of calcium polyphosphate (CPP) due to the organic part of composite’s pH was in slight alkaline. From the SEM, the cross-linked network structure could be observed clearly. Because the glycosaminoglycans-like chains in CMC molecules, which are typically presented in extracellular matrix (ECM), extractions of composite material gave the cells good adhesion and growth condition. All the results testified the composite scaffold was a good candidate for bone repair. 相似文献
48.
使用MP2方法研究了N-H•••O=C氢键二聚体的氢键强度,探讨了不同取代基对N-H•••O=C氢键强度的影响.研究发现,可以通过改变质子供体或受体分子上取代基的供电性或吸电性来调控氢键强度:乙基等供电子基团对N-H•••O=C氢键强度的调节作用不大;NO2和CN等强吸电子基团可极大地改变N-H•••O=C氢键强度;质子供体分子中的强吸电子基团如CN可使N-H•••O=C氢键强度增强多达4.6kcal/mol,质子受体分子中的强吸电子基团如NO2可使N-H•••O=C氢键强度减弱多达2.6kcal/mol.自然键轨道(NBO)分析表明,N-H•••O=C氢键强度越强,参与形成氢键的氢原子电荷越正,氧原子电荷越负,单体分子间电荷转移越多,N-H•••O=C氢键中氧原子孤对电子n(O)对N-H反键轨道σ*(N-H)的二阶稳定化能越大. 相似文献
49.
Biodegradable microspheres have been widely used in drug/protein delivery system. In this paper, a modified ionotropic gelation method combined with a high voltage electrostatic field was developed to prepare protein-loaded chitosan microspheres. Bovine serum albumin (BSA) was chosen as a model protein. The preparation process and major parameters were discussed and optimized. The morphology, particle size, encapsulation efficiency and in vitro release behavior of the prepared microspheres were investigated. The results revealed that the microspheres exhibited good sphericity and dispersity when the mixture of sodium tripolyphosphate (TPP) and ethanol was applied as coagulation solution. Higher encapsulation efficiency (>90%) was achieved for the weight ratio of BSA to chitosan below 5%. 35% of BSA was released from the microspheres cured in 3% coagulation solution, and more than 50% of BSA was released from the microspheres cured in 1% coagulation solution at pH 8.8. However, only 15% of BSA was released from the microspheres cured in 1% coagulation solution at pH 4. The results suggested that ionotropic gelation method combined with a high voltage electrostatic field will be an effective method for fabricating chitosan microspheres for sustained delivery of protein. 相似文献
50.
Qian Zhao Yehai Xu Yanhui Li Tingshun Jiang Changsheng Li Hengbo Yin 《Applied Surface Science》2009,255(23):34-9429
Rare earth Ce-incorporated MCM-41 mesoporous molecular sieves (CeMCM-41) were synthesized via a direct and nonhydrothermal method at room temperature from sodium silicate and ammonium cerium (IV) nitrate as raw materials. Cetyltrimethyl ammonium bromide (CTAB) was used as a template. The resultant samples were characterized by means of powder X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance ultraviolet–visible spectroscopy (UV–vis) and N2 physical adsorption, respectively. The effect of the Si/Ce molar ratio on the crystalline structure and textural properties of CeMCM-41 was also investigated. The experimental results show that ordered CeMCM-41 mesoporous molecular sieves were successfully synthesized at room temperature and the resultant mesoporous materials have specific surface areas in the range of 594–1369 m2/g and average pore sizes in the range of ca. 2.5–2.8 nm. It has been found that the structural properties are strongly related to the amounts of cerium incorporation. When the cerium content increased in the samples, the intensity of the peak (1 0 0) was gradually reduced, and the surface area and structural regularity were diminished. 相似文献