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51.
Khodabakhsh NIKNAM Mohammad Ali ZOLFIGOL Zahra HOSSIENINEJAD Nader DANESHVAR 《催化学报》2007,28(7):591-595
以金属硫酸氢盐M(HSO4)n(Ca(HSO4)2,Zn(HSO4)2和过硫酸氢钾制剂oxone○R)为催化剂催化醛、1,3-二羰基化合物和尿素进行缩合反应,在90℃及无溶剂的条件下高收率、一锅法合成了3,4-二氢嘧啶-2(1H)-酮. 相似文献
52.
Artificial cerebrospinal fluid (c.s.f.) containing 40 mmol/L excess calcium was perfus-ed through the lateral ventricles of New Zealand white rabbits in order to reduce the Na~+/Ca~(++) ratio in the brain and the effects on both the febrile response and adenosine cyclic mo-nophosphate (cAMP) concentration in plasma and c.s.f, during leucocytic pyrogen (LP)-induced fever were observed. The results showed that cAMP concentration in c.s.f, increas-ed significantly during LP-induced fever while the cAMP level in Plasma remained unchang-ed, and the perfusion of artificial c.s,f, containing 40 mmol/L excess calcium can signif-icantly inhibit not only the febrile response but also the increase in c.s.f, cAMP level,while there appears no effect on plasma cAMP concentration, thus demonstrating that theincrease of Na~+/Ca~(++) ratio causing the increase of cAMP content in the brain may be anessential link in the pathogenesis of LP-induced fever. 相似文献
53.
Lingjia Xu Liangliang Zhu Shi Wu Xiaopeng Chen Qiwen Teng 《Central European Journal of Chemistry》2006,4(4):732-742
Supermolecular complexes formed by oligophenyleneethynylene derivatives and isophthalic acid were studied using AM1 method
to obtain binding energy. Electronic spectra and IR spectra of the complexes were calculated by INDO/CIS and AM1 methods based
on AM1 geometries. Results indicated that the dimer could be formed by the monomers via hydrogen bonding because of the negative
binding energy. Binding energy of the complexes was affected by electronegativity and steric effects of the substituents.
The first UV absorptions and IR frequencies of N-H bonds of the complexes were both red-shifted compared with those of the
monomers. The complexes could bind small molecules via hydrogen bonds, resulting in the change in UV absorptions and an increase
in IR frequencies of N-H bonds. 相似文献
54.
Xiaoqiang Li Stefan Miltschitzky Andreas Grauer Veronika Michlov Burkhard Knig 《Tetrahedron》2006,62(52):12191-12196
The synthesis and peptide-binding properties of a Zn(II)nitrilotriacetate complex substituted with pyrimidine hydrazine amides are reported. The metal complex provides millimolar binding affinity in aqueous buffer to peptides bearing N-terminal His. The pyrimidine heterocycles intermolecularly interact with the bound peptide and quench the emission of nearby Trp residues by energy transfer. 相似文献
55.
Publications on the binding characteristics of metals with humic acid (HA) are sparse. Here we investigated the release of nickel from Ni(II)-HA complexes using model solutions of three different [Ni(II)]/[HA] mole ratios at three different pH values; we also compared the results with those of [Ni(II)]/[FA] complexes from previous work in this laboratory. Ligand exchange kinetics using the competing ligand exchange method (CLEM) were studied using two different techniques: graphite furnace atomic absorption spectrometry (GFAAS) with Chelex 100 resin as the competing ligand, and adsorptive cathodic stripping voltammetry (AdCSV) with dimethylglyoxime as the competing ligand to measure the rate of dissociation of Ni(II)-HA complexes. The results of the kinetic studies showed that as the [Ni(II)]/[HA] mole ratio was decreased, the rate of dissociation of Ni(II)-HA complexes decreased, and the proportion of free Ni2+ ions plus very labile nickel complexes decreased while the proportion of the less labile kinetically distinguishable components increased. Generally, the rate of dissociation of Ni(II)-HA complexes was slower than that of Ni(II)-FA complexes. Studies on the validity of the kinetic model showed that the concentrations of chemical species varied in a reasonable way with pH and the [Ni(II)]/[HA] mole ratios, indicating that the kinetically distinguishable components have chemical significance and the kinetic model is valid. 相似文献
56.
桑蚕丝素蛋白初始结构对其矿化作用的影响 总被引:4,自引:0,他引:4
以碱金属离子诱导桑蚕丝素蛋白溶液发生构象转变, 研究了蛋白质初始结构对其矿化作用的影响. FT-IR, XRD和SEM等测试结果显示, 未经任何处理的桑蚕丝素蛋白溶液矿化后形成片状复合物, 其无机相以二水磷酸氢钙(DCPD)为主; 而经过K+和Na+金属离子处理后, 桑蚕丝素溶液的结构由无规线团/螺旋构象向β-折叠发生转变, 矿化后成纤维状, 并相互结合呈现纳米级的三维多孔结构, 其无机相以热力学稳定的羟基磷灰石(HA)为主. 可以认为, 丝素蛋白结构转化为较伸展的β-折叠后, 使得更多的亲水基团暴露在外面, 在丝素蛋白分子不断凝聚成纤过程中, HA结晶快速生长并附着在这些微纤上, 最终形成纤维状的丝素蛋白/HA复合物. 该结果为阐明蛋白质的生物矿化过程及其调控机理提供了理论依据, 同时可以从矿化复合物的形成来反映这些微量元素可能对骨组织形成的影响, 为临床骨组织的修复提供一定的参考. 相似文献
57.
Designing peptide inhibitors of the p53-MDM2 interaction against cancer is of wide interest. Computational modeling and virtual screening are a well established step in the rational design of small molecules. But they face challenges for binding flexible peptide molecules that fold upon binding. We look at the ability of five different peptides, three of which are intrinsically disordered, to bind to MDM2 with a new Bayesian inference approach (MELD × MD). The method is able to capture the folding upon binding mechanism and differentiate binding preferences between the five peptides. Processing the ensembles with statistical mechanics tools depicts the most likely bound conformations and hints at differences in the binding mechanism. Finally, the study shows the importance of capturing two driving forces to binding in this system: the ability of peptides to adopt bound conformations () and the interaction between interface residues (). 相似文献
58.
Fabian Mohr 《Journal of organometallic chemistry》2004,689(2):374-379
The polyether bis(alkynes) α,ω-bis(O-propargyl)triethylene glycol and α,ω-bis(O-4-propargyloxyphenoxy)triethylene glycol reacted with [AuCl(SMe2)] in the presence of base to form the corresponding oligomeric gold(I) acetylide complexes (AuCCCH2O(CH2CH2O)3CH2CCAu)n and (AuCCCH2OC6H4O(CH2CH2O)3C6H4OCH2CCAu)n. These digold(I) diacetylide complexes reacted with diphosphine ligands to give macrocyclic digold(I) complexes of the type [Au2(μ-CC)(μ-PP)], where CC is the diacetylide and PP is a diphosphine ligand. These digold(I) complexes bind the cations Li+, Na+, K+ and Cs+, as studied by electrospray mass spectrometry. 相似文献
59.
在固定床反应器上,评价了不同温度下钙钛矿型复合氧化物SrTiO3和CaTiO3的组成变化对甲烷氧化偶联反应的影响.同时,利用XPS和CO2-TPD对催化剂的结构及其氧物种的反应特性进行了表征.结果表明:SrTiO3和少量Ca掺杂的CaxSrl-xTiO3有利于在较低温度(923K)下催化反应的活性和选择性,而CaTiO3体系则在高温(1073K)下表现出较好的活性和选择性.钙钛矿型复合氧化物SrTiO3和CaTiO3组成变化对不同温度下反应活性的影响与CO2-TPD的脱附谱图有很好的平行关系. 相似文献
60.
甲烷在SrO-La2O3/CaO催化剂上的氧化偶联Ⅱ.反应动力学的研究 总被引:1,自引:0,他引:1
在20%La2O3/CaO(LC)催化剂中添加SrO(添加SrO的LC以SLC表示)明显地提高了反应活性和C2选择性。反应动力学研究表明,LC和SLC催化剂在甲烷氧化偶联反应中,在表观活化能和表观反应级数上存在很大的差异。LC催化剂在CH4转化以及C2和COx形成过程中,表观活化能大于SLC催化剂,而SLC催化剂的指前因子小于LC体系,两者存在着补偿形象。SLC催化剂的反应速率常数比kc2/kCH 相似文献