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161.
162.
A one-pot method for the regioselective formation of the three disulfide bridges of the heat-stable bacterial enterotoxin STa, residues 5–18, employing a temperature-controlled orthogonal protecting group scheme is reported. The protecting groups trityl, t-butyl and 4-methylbenzyl were chosen for the selective formation of the three cystine residues. Cleavage of the peptide from the solid support afforded a partially S-protected crude product with two free thiol groups. The first disulfide linking Cys 6 to Cys 14 was formed by oxidation of the dithiol peptide in a mixture of water/acetonitrile/DMSO. Following solvent removal, the second disulfide between Cys 5 and Cys 10 was formed directly by simultaneous cleavage and oxidation of the t-butyl groups in TFA/DMSO/anisole at room temperature. Subsequent heating of this solution initiated cleavage of the 4-methylbenzyl groups with concomitant oxidation of Cys 9 and Cys 17 yielding the desired three disulfide product. 相似文献
163.
Interest in zirconia as a chromatography support has increased considerably recently because of its chemical inertness and its promise as a useful support. We have reported the preparation of spherical zirconia and characterization of its chromatographic behavior. However, the zirconia was found unsatisfactory for its chromatographic efficiency, probably owing to the poor pore structure of it. In this paper, we for the first time report the preparation of alkylphosphonic acid modified zirconia-magnesia stationary phase, and characterization of its structure and chromatographic behavior. 相似文献
164.
[5-(芳亚甲基氨基)-1,3,4-噻二唑-2-基]硫乙酰芳胺的合成及 生物活性研究 总被引:2,自引:0,他引:2
在K2CO3存在下利用聚乙二醇-400 (PEG-400)作相转移催化剂, 于固-液相转移催化条件下, 通过5-芳亚甲基氨 基-2-巯基-1,3,4-噻二唑与氯乙酰芳胺的硫烷基化反应, 合成了16个未见文献报道的[5-(芳亚甲基氨基)-1,3,4-噻二唑-2-基]硫乙酰芳胺衍生物. 经元素分析, FT-IR,1H NMR和13C NMR确证了其结构. 生物活性实验结果表明, 部分化合物对小麦幼苗的生长具有明显的植物生长调节活性, 并对枯草杆菌具有一定的抑制活性. 相似文献
165.
A rapid qualitative method using on-line column-switching liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed and validated for screening 13 target veterinary drugs: four macrolides - erythromycin A, josamycin (leucomycin A3), kitasamycin (leucomycin A5), and tylosin A; six (fluoro)quinolones - ciprofloxacin, danofloxacin, enrofloxacin, flumequine, oxolinic acid, and sarafloxacin; and lincomycin, virginiamycin M1, and trimethoprim in different animal muscles. Clindamycin, norfloxacin, nalidixic acid, oleandomycin, ormetoprim, and roxithromycin were used as the internal standards. After simple deproteination and analyte extraction of muscle samples using acetonitrile, the supernatant was subjected to on-line cleanup and direct analysis by LC/MS/MS. On-line cleanup with an extraction cartridge packed with hydrophilic-hydrophobic polymer sorbent followed by fast LC using a short C18 column resulted in a total analysis cycle of 6 min for 19 drugs. This screening method considerably reduced the time and the cost for the quantitative and confirmatory analyses. The application of a control point approach was also introduced and explained. 相似文献
166.
研究了碱基在十二胺-N,N-二亚甲基膦酸(DDPA)改性氧化锆固定相(DPZ)上的色谱保留行为,考察了流动相中甲醇含量、流动相pH值、缓冲溶液中离子类型和离子强度对碱基保留的影响,对DDPA在氧化锆表面的吸附方式进行了研究。研究结果表明,DDPA仅以一个膦酸基与氧化锆结合,因而DPZ固定相表面上除了有长链的疏水烷基外,还有酸性的膦酸基和碱性的氨基。碱基分子中也存在氨基和酰胺基等极性基团,因此碱基在DPZ固定相上除了有疏水作用外,还具有电荷排斥作用、离子交换作用等多种保留机理。由于多种保留机理的存在,使得碱基在DPZ固定相上具有较好的分离选择性,在酸性条件下对碱基混合样品的分离取得了满意的结果。 相似文献
167.
Mei Shu Yang Xu Xing Liu Yanping Li Qinghua He Zhui Tu Jinheng Fu Shirley J. Gee Bruce D. Hammock 《Analytica chimica acta》2016
A rapid and sensitive one-step competitive enzyme immunoassay for the detection of FB1 was developed. The anti-idiotypic nanobody–alkaline phosphatase (Ab2β−Nb−AP) was validated by the AP enzyme activity and the properties of bounding to anti-FB1-mAb (3F11) through colorimetric and chemiluminescence analyses. The 50% inhibitory concentration and the detection limit (LOD) of colorimetric enzyme-linked immunosorbent assay (ELISA) for FB1 were 2.69 and 0.35 ng mL−1, respectively, with a linear range of 0.93–7.73 ng mL−1. The LOD of the chemiluminescence ELISA (CLIA) was 0.12 ng mL−1, and the IC50 was 0.89 ± 0.09 ng mL−1 with a linear range of 0.29–2.68 ng mL−1. Compared with LC-MS/MS, the results of this assay indicated the reliability of the Ab2β−Nb−AP fusion protein based one-step competitive immunoassay for monitoring FB1 contamination in cereals. The Ab2β−Nb−AP fusion proteins have the potential to replace chemically-coupled probes in competitive enzyme immunoassay systems. 相似文献
168.
WANG Rui DA Chao-Shan LIU Da-Xue YANG Xiao-wu XIN Zhuo-Qun DONG Shou-Liang ShEN Jan-Heng SU Wu WANG Heng-shan WANG Quan ZHANG Li-Chen CHAN Albert S.C 《高等学校化学研究》2001,17(3)
Catalytic asymmetric carbon-carbon bond formation is one of the most important reactions and have attracted much attention to develop more efficient enantioselective C-C formation methods in organic synthesis. In this field, asymmetric addition of diethylzinc to aldehydes[1] and conjugate addition to enones[2] have drawn special interests and have been greatly developed. Regardless of it, much spaces in these areas still exist, so it needs more extensive and intensive researches for the purpose of as follows: (1) attaching ligands to a polymer for the easy separation of the catalysts so as to be able to allow very efficient recovery and reuse of the catalysts, and the possibility of carrying out the desired transfomation in continuous mode in a flow reactor, etc., (2) searching for novel chiral catalysts with such features as more suitable for more extensive substrates varieties, and more convenient and economical as well as possessing applicable prospect, and so on. Here we report some works in these areas done in our laboratory. 相似文献
169.
Heron Vrubel Manfredo Hrner Estela dos Reis Crespan Shirley Nakagaki Fbio S. Nunes 《无机化学与普通化学杂志》2008,634(11):1839-1841
Hydrogen peroxide reacts with [MoO2Cl2(dmso)2] to produce orange crystals of the title complex, [MoO(O2)Cl2(dmso)2]. The structure is orthorhombic with distorted pentagonal bipyramidal geometry around the molybdenum ion. A short O‐O bond length suggested the presence of a superoxide, but electron paramagnetic resonance measurements definitely supported the peroxo structure. 相似文献
170.
2,2,3,4,4-pentamethylphosphetanic acid,C8H16PO2H: salts,complexes and a hydrogen bonded amine adduct
John Emsley Amanda P. Dunning Robert J. Parker John K. Williams Shirley Brown Stella Earnshaw David S. Moore 《Polyhedron》1984,3(3):325-329
The conjugate base of the title acid, i.e. C8H16PO2?, has been investigated as its simple salts, as a ligand in transition metal complexes of cobalt and ruthenium, and as a secondary amonium salt in which hydrogen bonding between anion and cation occurs. 相似文献