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601.
Masahiro Yamasaki Shinya Hasegawa Hiroshi Takahashi Yuka Kobayashi Chihiro Sakai Yoko Ashizawa 《Natural product research》2015,29(22):2103-2106
One of the activities of placental extracts (PEs) is skin-whitening effect, but the physiological and genetic mechanism for this effect has not yet been clarified. Here, we focus on PE as a regulator of antioxidant enzyme genes. Porcine PE was prepared, and its activity was investigated in B16 melanoma cells. PE treatment decreased the melanin content of UV-irradiated B16 cells in a dose-dependent manner. PE directly reduced the enzyme activity of tyrosinase in a cell-free assay. In addition, PE treatment increased the gene expression of cytosolic superoxide dismutase (SOD-1), extracellular SOD (SOD-3) and catalase but did not affect the expression of tyrosinase. Moreover, PE protected the B16 cells from H2O2-induced cell death. Taken together, our data suggest that PEs could play a role not only as a suppressor of melanin synthesis but also as a regulator of antioxidant genes and might protect the skin against oxidative stress. 相似文献
602.
以苯乙酮为唯一碳源,从土壤中筛选出一株能够将4-氧-4-[3-(三氟甲基)-5,6-二氢[1,2,4]三唑并[4,3-a]吡嗪-7(8H)-基]-1-(2,4,5-三氟苯基)丁-2-酮(2)对映选择性还原为抗Ⅱ型糖尿病药物西他列汀关键手性中间体(S)-3-羟基-1-[3-(三氟甲基)-5,6-二氢[1,2,4]三唑并[4,3-a]吡嗪-7(8H)-基]-4-(2,4,5-,三氟苯基)丁-1-酮((S)-1)的细菌菌株,经鉴定并命名为类产碱假单胞菌(Pseudomonas pseudoalcaligenes)XW-40.系统研究了水溶性辅溶剂、温度、p H、底物浓度、细胞浓度、反应时间等反应条件对生物还原产率和对映选择性的影响.该菌株全细胞能够耐受浓度高达10 g/L的前手性酮2.在最优反应条件下,以制备规模合成了(S)-1,分离收率90%,ee99%. 相似文献
603.
In this study, a new binary complex [Cu(HCip)2](NO3)2 · 6H2O (1) has been synthesized and then characterized by X-ray structure analyses. In this compound, each ciprofloxacin acts as a bidentate ligand resulting in a crystallographically planar configuration; the nitrate anions are located in apical positions with an axial distance significantly larger than the equatorial distances, which would be consistent with a very weak metal ion interaction due to the Jahn–Teller effect. In addition, both the synthesis and characterization of two new ternary complexes of ciprofloxacin–copper(II)–1,10-phenanthroline, [Cu(phen)(Cip)](NO3) · 4H2O (2) and Cu(phen)(HCip)(NO3)2 · H2O (3), have been accomplished. We have also undertaken the single crystal structural determination of 2, in which the ciprofloxacin acts as tridentate bridging ligand; the complex exhibits a five-coordinated motif in a distorted square pyramidal environment around the metal center. The chemical nuclease activity of compounds 2 and 3 has also been studied, revealing that both compounds behave as efficient chemical nucleases in the presence of ascorbate. Mechanistic studies, with various radical oxygen scavengers, indicate that the DNA cleavage reaction is mediated by hydroxyl radicals, singlet oxygen, and the superoxide anion. 相似文献
604.
Superoxide Dismutase Activity of the Naturally Occurring Human Serum Albumin–Copper Complex without Hydroxyl Radical Formation 下载免费PDF全文
Ryunosuke Kato Dr. Matofusa Akiyama Prof. Dr. Hiroyoshi Kawakami Prof. Dr. Teruyuki Komatsu 《化学:亚洲杂志》2014,9(1):83-86
The superoxide radical anion (O2.?) is biologically toxic and contributes to the pathogenesis of various diseases. Here we describe the superoxide dismutase (SOD) activity of human serum albumin (HSA) complexed with a single CuII ion at the N‐terminal end (HSA–Cu complex). The structure of this naturally occurring copper‐coordinated blood serum protein has been characterized by several physicochemical measurements. The O2.? dismutation ability of the HSA–Cu (1:1) complex is almost the same as that of the well‐known SOD mimics, such as MnIII‐tetrakis(N‐methylpyridinium)porphyrin. Interestingly, the HSA–Cu complex does not induce a subsequent Fenton reaction to produce the hydroxyl radical (OH.), which is one of the most harmful reactive oxygen species. 相似文献
605.
Formation of High‐Valent Iron–Oxo Species in Superoxide Reductase: Characterization by Resonance Raman Spectroscopy 下载免费PDF全文
Dr. Florence Bonnot Dr. Emilie Tremey Dr. David von Stetten Dr. Stéphanie Rat Dr. Simon Duval Dr. Philippe Carpentier Dr. Martin Clemancey Dr. Alain Desbois Dr. Vincent Nivière 《Angewandte Chemie (International ed. in English)》2014,53(23):5926-5930
Superoxide reductase (SOR), a non‐heme mononuclear iron protein that is involved in superoxide detoxification in microorganisms, can be used as an unprecedented model to study the mechanisms of O2 activation and of the formation of high‐valent iron–oxo species in metalloenzymes. By using resonance Raman spectroscopy, it was shown that the mutation of two residues in the second coordination sphere of the SOR iron active site, K48 and I118, led to the formation of a high‐valent iron–oxo species when the mutant proteins were reacted with H2O2. These data demonstrate that these residues in the second coordination sphere tightly control the evolution and the cleavage of the O? O bond of the ferric iron hydroperoxide intermediate that is formed in the SOR active site. 相似文献
606.
Motoichi Kurisawa Joo Eun Chung Hiroshi Uyama Shiro Kobayashi 《Macromolecular bioscience》2003,3(12):758-764
Catechin was oxidatively polymerized by laccase in a mixture of a polar organic solvent and buffer to give a new class of flavonoid polymers. Myceliophthora laccase showed high catalytic activity for the polymerization. Using a mixed solvent of acetone and pH 5 acetate buffer efficiently produced the polymer. Under the selected conditions, DMF‐soluble polymers were obtained in good yields. Effects of reaction parameters on the yield, solubility, and molecular weight of the polymer have been systematically investigated. A radical species was detected in the polymer by ESR spectroscopy. The polymers showed greatly amplified superoxide scavenging activity and xanthine oxidase inhibitory activity compared with monomeric catechin.
607.
608.
配合物[Ni(EDTB)]•2Cl•CH3OH•C2H5OH的合成、晶体结构及SOD模拟活性的研究 总被引:3,自引:0,他引:3
报道六齿配体N,N,N',N'-四(2-苯并咪唑亚甲基)-1,2-乙二胺(EDTB)及单核镍(II)配合物[Ni(EDTB)]•2Cl• CH3OH•C2H5OH的合成、晶体结构和SOD模拟活性. 该配合物为三斜晶系, P1空间群, a=1.0931(2) nm, b=1.1693(2) nm, c=1.6756(4) nm, α=76.042(3)°, β=88.787(3)°, γ=72.044(3)°, V=1.9740(7) nm3, Dc=1.321 g/cm3, Z=2, F(000)=824, μ=0.670 mm-1. 最终因子R[I>2σ(I)]: R1=0.0611, wR2=0.1497; R(全部数据): R1=0.0870, wR2=0.1604. 结构分析表明, 镍(II)分别与配体中的四个苯并咪唑氮和两个亚胺基氮配位形成扭曲的八面体构型. 改良的邻苯三酚自氧化活性测定表明, 该配合物具有较高的SOD模拟活性. 相似文献
609.
610.
4-Deoxy-l-erythro-5-hexoseulose uronate (DEH), DEH reductase, and alginate lyase have key roles in the metabolism of alginate, a promising carbon source in brown macroalgae for biorefinery. In contrast to the widely reviewed alginate lyase, DEH and DEH reductase have not been previously reviewed. Here, we summarize the current understanding of DEH and DEH reductase, with emphasis on (i) the non-enzymatic and enzymatic formation and structure of DEH and its reactivity to specific amino groups, (ii) the molecular identification, classification, function, and structure, as well as the structural determinants for coenzyme specificity of DEH reductase, and (iii) the significance of DEH for biorefinery. Improved understanding of this and related fields should lead to the practical utilization of alginate for biorefinery. 相似文献