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141.
A room temperature ionic liquid N‐butylpyridinium hexafluorophosphate (BPPF6) was used as a binder to make an ionic liquid modified carbon paste electrode (IL‐CPE), which showed good characteristics such as simple preparation procedure, fast electrochemical response and good conductivity. The electrochemical oxidation of ascorbic acid (AA) on the new IL‐CPE was carefully studied. The oxidation peak potential of AA on the IL‐CPE appeared at 109 mV (vs. SCE), which was about 338 mV decrease of the overpotential compared to that obtained on the traditional carbon paste electrode (CPE) and the oxidation peak current was increased for about four times. The electrochemical parameters of AA on the IL‐CPE were calculated with the charge transfer coefficient (α) and the electrode reaction rate constant (ks) as 0.87 and 0.800 s?1, respectively. Based on the relationship of the oxidation peak current and the concentration of AA a sensitive analytical method was established with cyclic voltammetry. The linear range for AA determination was in the range from 1.0×10?5 to 3.0×10?3 mol/L with the linear regression equation as Ip (μA)=?2.52–0.064C (μmol/L) (n=13, γ=0.9942) and the detection limit was calculated as 8.0×10?6 mol/L (3σ). The proposed method was free of the interferences of coexisting substances such as dopamine (DA) and amino acids etc., and successfully applied to the vitamin C tablets determination. 相似文献
142.
以变色酸2R为底物测定辣根过氧化物酶的研究 总被引:4,自引:0,他引:4
变色酸 2R(CT2R)是一种具有电化学活性的物质 ,在碱性条件下 ,该物质在滴汞电极上 - 6 6 0mV(vs.SCE)左右产生还原波 ,加入H2 O2 和辣根过氧化物酶 (HRP)后 ,该物质被氧化生成具有非电化学活性的物质 ,导致溶液中游离的CT2R浓度降低 ,相应还原波波高降低 ,HRP在一定含量范围内与伏安峰的降低值具有良好的线性关系。通过测定波高的降低值可测定HRP ,测定游离HRP的线性范围是 4 .0× 10 -5~ 4 .0× 10 -3 g/L。对酶促反应的动力学进行了研究 ,反应的米氏常数Km =1.38mmol/L ,最大反应速率Vmax=5 3.9nA/min。 相似文献
143.
Dr. Yuan Zhang Yong Zhang Ya Lei Sun Dr. Xin Du Dr. Jiao Yi Shi Wei David Wang Prof. Dr. Wei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(20):6328-6334
We report herein for the first time the incorporation of a versatile organocatalyst, 4‐(N,N‐dimethylamino)pyridine (DMAP), into the network of a nanoporous conjugated polymer (NCP) by the “bottom‐up” approach. The resulting DMAP‐NCP material possesses highly concentrated and homogeneously distributed DMAP catalytic sites (2.02 mmol g?1). DMAP‐NCP also exhibits enhanced stability and permanent porosity due to the strong covalent linkage and the rigidity of the “bottom‐up” monomers. As a result, DMAP‐NCP shows excellent catalytic activity in the acylation of alcohols with yields of 92–99 %. The DMAP‐NCP catalyst could be easily recovered from the reaction mixture and reused in at least 14 consecutive cycles without measurable loss of activity. Moreover, the catalytic acylation reaction could be performed under neat and continuous‐flow conditions for at least 536 h of continuous work with the same catalyst activity. 相似文献
144.
以超支化聚乙烯亚胺为构筑基元、以卤键为推动力制备了可以选择性吸附带有负电荷小分子的层层组装多层膜. 为了将超支化聚乙烯亚胺引入多层膜体系中, 我们首先制备了接枝有卤键给体分子-碘全氟苯的超支化聚乙烯亚胺(BPEI-I). 然后将BPEI-I和含有卤键受体的聚(4-乙烯吡啶)(PVPy)在四氢呋喃和三氯甲烷的混合溶剂中组装成膜, 并用紫外可见光谱、AFM和XPS对膜的组装过程、形貌、厚度和推动力进行了表征. 制备得到的BPEI-I和PVPy多层膜可以吸附含有负电荷的2-蒽甲酸钠小分子, 而对有类似结构但带有正电荷的溴化-N-(2-蒽甲基)吡啶盐却没有吸附作用. 这种选择性吸附能力主要得益于包覆在多层膜中的超支化聚乙烯亚胺基元的正电荷空腔和由卤键构筑的弱极性微环境. 本文的研究为制备选择性吸附薄膜提供了一种新的思路, 在传感、富集分离和微接触印刷等领域都有潜在应用价值. 相似文献
145.
电化学DNA杂交检测技术因其快速、灵敏、低消耗和易于操作等优点而在临床医学、环境监测和药物分析等领域受到普遍关注。电化学DNA杂交指示剂是DNA电化学杂交传感器的重要组成部分,能与单链DNA和双链DNA通过不同的模式和作用力进行差异性结合。本文介绍了电化学杂交指示剂的定义及其在DNA电化学传感器中的重要性,根据分子结构上的特征差异,将非标记型电化学杂交指示剂分为有机染料(荧光素)、药物分子和金属配合物三类,并从中选取了各个类型中具有代表性的指示剂对它们的工作原理、研究进展和应用现状进行了比较和评述。对杂交指示剂的设计和开发前景,特别是满足基因芯片应用等方面做出了展望。 相似文献
146.
Closo-BnHn−2(CO)2 (n = 5–12), isolobal analogues of closo-C2Bn−2Hn, have been investigated at the B3LYP/6-311+G**density functional level of theory. The most stable isomers of closo-BnHn−2(CO)2 are similar to those of closo-C2Bn−2Hn in geometric patterns apart from closo-B6H4(CO)2, and closo-BnHn−2(CO)2 is much less strained than closo-C2Bn−2Hn. Energetic analysis identifies closo-B6H4(CO)2, closo-B12H10(CO)2 and closo-B10H8(CO)2 to be most stable, of which the latter two cages have been prepared experimentally. On the basis of the negative and rather large nucleus independent chemical shifts (NICS), closo-BnHn−2(CO)2 are aromatic. To aid further experimental study, the CO stretching frequencies have been computed. 相似文献
147.
Enhancement of Solar Hydrogen Evolution from Water by Surface Modification with CdS and TiO2 on Porous CuInS2 Photocathodes Prepared by an Electrodeposition–Sulfurization Method 下载免费PDF全文
Dr. Jiao Zhao Dr. Tsutomu Minegishi Li Zhang Dr. Miao Zhong Gunawan Dr. Mamiko Nakabayashi Dr. Guijun Ma Dr. Takashi Hisatomi Dr. Masao Katayama Prof. Dr. Shigeru Ikeda Prof. Dr. Naoya Shibata Prof. Dr. Taro Yamada Prof. Dr. Kazunari Domen 《Angewandte Chemie (International ed. in English)》2014,53(44):11808-11812
Porous films of p‐type CuInS2, prepared by sulfurization of electrodeposited metals, are surface‐modified with thin layers of CdS and TiO2. This specific porous electrode evolved H2 from photoelectrochemical water reduction under simulated sunlight. Modification with thin n‐type CdS and TiO2 layers significantly increased the cathodic photocurrent and onset potential through the formation of a p–n junction on the surface. The modified photocathodes showed a relatively high efficiency and stable H2 production under the present reaction conditions. 相似文献
148.
Efficient Copper‐Catalyzed Direct Intramolecular Aminotrifluoromethylation of Unactivated Alkenes with Diverse Nitrogen‐Based Nucleophiles 下载免费PDF全文
Dr. Jin‐Shun Lin Ya‐Ping Xiong Can‐Liang Ma Li‐Jiao Zhao Prof. Dr. Bin Tan Prof. Dr. Xin‐Yuan Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(5):1332-1340
A mild, convenient, and step‐economical intramolecular aminotrifluoromethylation of unactivated alkenes with a variety of electronically distinct, nitrogen‐based nucleophiles in the presence of a simple copper salt catalyst, in the absence of extra ligands, is described. Many different nitrogen‐based nucleophiles (e.g., basic primary aliphatic and aromatic amines, sulfonamides, carbamates, and ureas) can be employed in this new aminotrifluoromethylation reaction. The aminotrifluoromethylation process allows straightforward access to diversely substituted CF3‐containing pyrrolidines or indolines, in good to excellent yields, through a direct difunctionalization strategy from the respective acyclic starting materials. Mechanistic studies were conducted and a plausible mechanism was proposed. 相似文献
149.
A new eudesmanolide, 1‐oxo‐11αH‐eudesma‐2,4(14)‐dien‐12,8β‐olide ( 1 ), and four new guaianolides, 9β,10β‐epoxy‐4α‐hydroxy‐1βH,11αH‐guaian‐12,8α‐olide ( 2 ), 9β,10β‐epoxy‐4α‐hydroxy‐1βH,11βH‐guaian‐12,8α‐olide ( 3 ), 4α,9α‐dihydroxy‐1βH,11αH‐guai‐10(14)‐en‐12,8α‐olide ( 4 ), and 4α,9α‐dihydroxy‐1βH,11βH‐guai‐10(14)‐en‐12,8α‐olide ( 5 ), together with one known eudesmanolide and two known germacranolides, were isolated from the whole plants of Carpesium triste. Their structures and relative configurations were elucidated on the basis of spectroscopic methods, including 2D‐NMR techniques. 相似文献
150.