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981.
Ling-Fang Lei Min-Feng Chen Tao Wang Xi-Xin He Bing-Xin Liu Yun Deng Xiao-Jie Chen Yu-Ting Li Shan-Yue Guan Jun-Hua Yao Wei Li Wen-Cai Ye Dong-Mei Zhang Cui-Xian Zhang 《Tetrahedron》2014
One novel nine-membered macrocyclic polysulfur cembranoid lactone, sinulariaoid A (1); three new multioxygenated cembranoids, sinulariaoid B (2), sinulariaoid C (3), sinulariaoid D (4); and four known cembranoids, capilloloid (5), dihydrosinularin (6), sinularin (7), and dihydrosinuflexolide (8) were isolated from the soft coral Sinularia sp. collected off of Sanya Bay in the South China Sea. Their stereochemical structures were determined on the basis of extensive spectroscopic methods, including single crystal X-ray diffraction analysis. Sinulariaoid A (1) is the first reported nine-membered macrocyclic polysulfur cembranoid from soft coral. The cytotoxic activities of compounds 1–8 were determined in four human cancer cell lines (HepG2, HepG2/ADM, MCF-7, and MCF-7/ADM). Of these, sinulariaoid A (1) exhibited the most potent anticancer activity in vitro, and its cytotoxicity in HepG2/ADM was more potent than in the other three cell lines. Furthermore, it was found that sinulariaoid A (1) induced apoptosis, and its selective toxicity toward HepG2/ADM cells was not related to P-glycoproteins. 相似文献
982.
Substituent effects on the redox potentials of dihydroxybenzenes: theoretical and experimental study
Tao Liu Meng-Meng Liu Xiao-Wen Zheng Chong-Yang Du Xiang-Yang Cui Lu Wang Ling-Li Han Zhang-Yu Yu 《Tetrahedron》2014
The redox reactions of p-hydroquinone and pyrocatechol undergo a two-proton-two-electron process in aqueous solution. We calculated their redox potentials at the B3LYP/6-311+G(d,p) level, and verified the values by employing cyclic voltammetry experiments. Then we selected seven substituent groups (–F, –Cl, –OH, –COOH, –CN, –NH2, and –NO2 groups) to systematically investigate the substituent effect, including the sort, position, and number of the substituent, on the redox potentials of p-hydroquinone and pyrocatechol. The calculated results show that –NH2 and –OH groups can decrease the redox potentials, while –F, –Cl, –COOH, –CN, and –NO2 groups increase the potential values of p-hydroquinone and pyrocatechol. The calculations can accurately predict the substituent effects on the redox potentials of pyrocatechol and p-hydroquinone. We would expect that the accurate calculation results for the model systems could be applied in the prediction of electrode potentials of other molecules. 相似文献
983.
Hu Yuan Kaijian Bi Wanlin Chang Rongcai Yue Bo Li Ji Ye Qingyan Sun Huizi Jin Lei Shan Weidong Zhang 《Tetrahedron》2014
A total synthesis of Daphnodorin A, a member of the Daphnodorins, was accomplished. Key features of the synthetic strategy include construction of 2-substituted-3-functionalized benzofuran via intramolecular Heck reaction and a mild Barton–McCombie deoxygenation process mediated by triethylborane. The total synthesis provided Daphnodorin A in 19.7% or 5.6% overall yield over 7 or 15 steps. 相似文献
984.
Changtao Ji Qi Chen Qinglian Li Hongbo Huang Yongxiang Song Junying Ma Jianhua Ju 《Tetrahedron letters》2014
McbA was characterized in vitro as a novel amide synthetase in the marinacarbolines A–D biosynthetic pathway, catalyzing amide bond formation between 1-acetyl-3-carboxy-β-carboline (1a) and substituted-β-phenethylamines (1b, 2b, 3b) and tryptamine (4b) in an ATP-dependent manner. Enzyme kinetic analyses highlight β-phenethylamine as the most suitable amine donor. McbA showed broad substrate compatibility with substituted amines; 10 new β-carboline analogues were chemoenzymatically generated. 相似文献
985.
An efficient one-step method has been developed to construct furans via a Suzuki–Miyaura cross-coupling reaction of 1,2-oxaborol-2(5H)-ols with carboxylic anhydrides. In the presence of Pd(OAc)2/PCy3, the multi-substituted alkenylboron compounds could couple with anhydrides to obtain furans in moderate-to-good yields. The addition of bases promoted the coupling reaction, and the plausible reaction mechanism was proposed. 相似文献
986.
α-Hydroxyallylphosphinates were stereoselectively converted to γ-chloro allylphosphinates when treated with Ph3P and CCl4, via substitution of hydroxyl and migration of double bond. The reaction was promoted by phosphonium cation that acted as Lewis acid. 相似文献
987.
以正硅酸四甲酯(TMOS)为硅源,P123(EO20PO70EO20)为表面活性剂,在p H=6的磷酸缓冲体系中制备了囊泡状二氧化硅材料.利用乙醇萃取脱除模板剂P123,电镜观测结果表明所得二氧化硅具有大孔囊泡结构,N2吸附结果表明其具有高比表面积和大孔容.通过Boehm滴定法确定了硅羟基数量与吸水率呈正相关.用囊泡状二氧化硅材料与商业化活性炭(AC)和硅胶(SG)对水蒸气、正己烷和油气进行静态吸附.在自建的动态正己烷吸附装置上用对囊泡状二氧化硅材料和商业化AC和SG对正己烷进行动态吸附.吸附结果表明,囊泡状二氧化硅材料的静/动态吸附容量和稳定性都远高于商业化活性炭和硅胶. 相似文献
988.
近年来,我们基于1,1'-联萘基-2,2'-二酚(BINOL)为手性源成功地发展了一类多手性中心化合物联萘-2-芳甲羟基-2'-醇(Ar-BINMOLs),它是BINOL的单苄醚化合物经过不对称[1,2]-Wittig重排合成得到的,涉及C—O键的断裂与新C—C的构建反应,由轴手性诱导产生新的碳手性中心,结构独特新颖,同时具有C2轴手性和sp3碳手性的光学纯醇酚类化合物.目前,Ar-BINMOLs作为新型手性配体应用于不对称催化反应已有不少的报道.基于BINOL衍生物以及近几年Ar-BINMOLs及其衍生物的研究进展,重点阐述了其作为新型手性配体或手性骨架在不对称催化反应中的应用研究进展. 相似文献
989.
Enrichment of neonicotinoid insecticides from lemon juice sample with magnetic three‐dimensional graphene as the adsorbent followed by determination with high‐performance liquid chromatography
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A novel 3D‐graphene (3D‐G) magnetic nanomaterial was prepared and used as an adsorbent for the extraction of four neonicotinoid insecticides (acetamiprid, imidacloprid, thiacloprid, and thiamethoxam) from lemon juice sample. Then, HPLC with UV detection was applied for the determination of the neonicotinoid insecticides desorbed from the 3D‐G magnetic nanomaterial. The main experimental parameters that affect the extraction efficiencies such as the amount of 3D‐G magnetic nanomaterial, sample solution pH, extraction time, salting‐out effect, and desorption conditions were studied and optimized. As a result, the linear concentration range of the method was from 0.3 to 100.0 ng/mL for thiacloprid, from 0.5 to 100.0 ng/mL for imidacloprid and acetamiprid, and from 1.0 to 100.0 ng/mL for thiamethoxam, with correlation coefficients of 0.9965–0.9985, respectively. The LODs of the method based on an S/N of 3 were between 0.08 and 0.2 ng/mL. The enrichment factors obtained were between 67 and 427, and the RSDs (n = 6) were in the range from 4.6 to 7.1%, and the recoveries of the method fell in the range of 88.75 to 111.60%. 相似文献
990.
Qi Zhang Yingxiang Du Jiaquan Chen Guangfu Xu Tao Yu Xiaoyi Hua Jinjing Zhang 《Analytical and bioanalytical chemistry》2014,406(5):1557-1566
Various chiral selectors have been utilized successfully in capillary electrophoresis (CE); however, the number of polysaccharides used as chiral selectors is still small and the mechanism of enantiorecognition has not been fully elucidated. Chondroitin sulfate D (CSD) and chondroitin sulfate E (CSE), belonging to the group of glycosaminoglycans, are linear, sulfated polysaccharides with large mass. In this paper, they were investigated for the first time for their potential as chiral selectors by CE. The effect of buffer composition and pH, chiral selector concentration, and applied voltage were systematically examined and optimized. A variety of drug enantiomers were resolved in the buffer pH range of 2.8–3.4 using 20 mM Tris/H3PO4 buffer with 5.0 % CSD or CSE and 20 kV applied voltage. A central composite design was used to validate the optimized separation parameters and satisfactory uniformity was obtained. As observed, CSE allowed satisfactory separation of the enantiomers of amlodipine, laudanosine, nefopam, sulconazole, and tryptophan methyl ester, as well as partial resolution of citalopram, duloxetine, and propranolol under the optimized conditions. CSD allowed partial or nearly baseline separation of amlodipine, laudanosine, nefopam, and sulconazole. The results indicated that CSE has a better enantiorecognition capability than CSD toward the tested drugs. Figure
Chiral separation of various drug enantiomers in CE with CSE (A) and CSD (B) as chiral selectors 相似文献