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831.
832.
合成了12个吡啶氮桥联的双环三唑鎓盐2a~2l卡宾催化剂前体,用于催化苯偶姻缩合反应和酯交换反应,考察了反应条件对催化反应的影响,并与其它三唑鎓盐的催化活性进行了比较.结果表明,在较低催化剂用量下,催化剂2c表现出优良的催化活性,分离产率最高分别达到98%和93%. 相似文献
833.
834.
K. B. Sophy Dr. Jer‐Lai Kuo Prof. Dr. Xue‐Wei Liu Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(2):588-594
We carried out a principle study on the reaction mechanism of rhodium‐catalyzed intramolecular aziridination and aziridine ring opening at a sugar template. A sulfamate ester group was introduced at different positions of glycal to act as a nitrene source and, moreover, to allow the study of the relative reactivity of the nitrene transfer from different sites of the glycal molecule. The structural optimization of each intermediate along the reaction pathway was extensively done by using BPW91 functional. The crucial step in the reaction is the Rh‐catalyzed nitrene transfer to the double bond of the glycal. We found that the reaction could proceed in a stepwise manner, whereby the N atom initially induced a single‐bond formation with C1 on the triplet surface or in a single step through intersystem crossing (ISC) of the triplet excited state of the rhodium–nitrene transition state to the singlet ground state of the aziridine complexes. The relative reactivity for the conversion of the nitrene species to the aziridine obtained from the computed potential energy surface (PES) agrees well with the reaction time gained from experimental observation. The aziridine ring opening is a spontaneous process because the energy barrier for the formation of the transition state is very small and disappears in the solution calculations. The regio‐ and stereoselectivity of the reaction product is controlled by the electronic property of the anomeric carbon as well as the facial preference for the nitrene insertion, and the nucleophilic addition. 相似文献
835.
Liwei Yan Ying Xue Prof. Dr. Ge Gao Prof. Dr. Jingbo Lan Dr. Fan Yang Xiaoyu Su Dr. Jingsong You Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(7):2250-2257
The chiral tris‐monodentate imidazolinyl ligands 1 a – c exhibit a strong tendency to form the discrete, helical [2+3] nanocages 3 ([ 1 2 ?2 3]) with tartaric acids 2 . Circular dichroism (CD) spectra and theoretical calculations reveal that supramolecular handedness of capsulelike architectures is determined only by the chirality of the imidazolinyl ligands rather than tartaric acids. The chirality of imidazolinyl ligands is transferred to the helicity of the complexes through the directed hydrogen bonds between the N3 atom of imidazoline rings and the carboxyl of tartaric acids. These hydrogen‐bonded nanocages can spontaneously self‐assemble into spherical vesicles, during which the hydrogen bonding that arises from the hydroxyl groups of tartaric acids plays a crucial issue. The vesicles formed by [{(S,S,S)‐ 1 a }2( 2 L)3] ( 3 a ) may further evolve into microspheres that gelate organic solvents after being aged at ?20 °C for 24 h, and can also be unprecedentedly transformed to tubular assemblies capable of rigidifying the solvents when subjected to ultrasound irradiation. 相似文献
836.
The cellulose acetate covered Prussian blue modified glassy carbon electrode (GCE/PB/CA) was fabricated as a novel hydrogen peroxide sensor. It was shown by scanning electron microscope (SEM) and atomic force microscope (AFM) that Prussian blue was covered and protected by cellulose acetate perfectly. The modified electrode showed a good electrocatalytic activity for H2O2 reduction in neutral aqueous solution. H2O2 was detected amperometrically in 0.05 mol/L phosphate buffer solutions (pH 7.0, containing 0.1 mol/L KCl as supporting electrolyte) at an applied potential of ?0.2 V (vs. SCE). The response current was proportional to the concentration of H2O2 in the range of 1.0×10?5 mol/L to 2.5×10?4 mol/L with the detection limit of 2.2×10?6 mol/L at a signal to noise ratio 3. 相似文献
837.
Yong Shen Ai‐Xue Zuo Zhi‐Yong Jiang Xue‐Mei Zhang Hong‐Ling Wang Ji‐Jun Chen 《Helvetica chimica acta》2010,93(3):482-489
Five new C19‐diterpenoid alkaloids, named hemsleyaconitines A–E ( 1 – 5 , resp.), were isolated from Aconitum hemsleyanum Pritz. By UV, IR, MS, 1D‐ and 2D‐NMR analyses, their structures were elucidated as 18‐dehydroxygeniculatine D ( 1 ), 6‐hydroxy‐14‐O‐veratroylneoline ( 2 ), 14‐O‐acetyl‐8‐ethoxysachaconitine ( 3 ), 18‐veratroylkaracoline ( 4 ) and 8‐O‐ethylaustroconitine B ( 5 ). 相似文献
838.
Wen Wu Sun Shi Rong Li Hong Zhou Dr. Zhi Quan Pan Dr. Qi Mao Huang Xue Lei Hu 《无机化学与普通化学杂志》2010,636(7):1386-1391
A new dumbbell‐type 4,4′‐bipy‐bridged dinuclear copper(II) complex, [Cu2(4,4′‐bipy)L2(H2O)2](ClO4)4 · 8CH3OH · 10H2O, where L = 1‐[bis(3‐aminopropyl)amino]‐2‐ propanol and bipy = bipyridine, has been synthesized and characterized, X‐ray crystallographic analysis shows that the [Cu2(4,4′‐bipy)L2(H2O)2]4+ cations and water molecules generate layer structures extending parallel to bc planes through hydrogen bonding interactions of O–H ··· O and C–H ··· O. The layers are also connected by hydrogen bonding interactions involving methanol, water, and perchlorate anions. These interactions lead to the formation of rectangular channels of 12.3 Å × 6.0 Å along the crystallographic c axis. Perchlorate anions fill in each channel in a sandwich‐like packing mode, they are joined with the adjacent layers by water heptamers. Magnetic susceptibility measurements show that the magnetic exchange interaction is weak although it has a regular π‐type electron transfer pathway. Furthermore, the electrochemical and thermogravimetric properties of the complex were also investigated. 相似文献
839.
840.
Zhi‐An He Guang‐Zhou Lu Lin‐Lin Zhu Yong‐Xue Wang Fu‐Lin Yan Ji‐Xia Zhang 《中国化学会会志》2010,57(2):256-259
Two new ent‐kaurane diterpenoids, taihangexcisoidesin C (1) and its acetonide, taihangexcisoidesin D (2), along with 9 known compounds were isolated from the leaves of Isodon excisoides. The structures of the new compounds were elucidated using 1D and 2D NMR spectroscopy analysis. Compounds 3‐6 and 8‐9 were tested for their antibacterial activity against Escherichia coli, Staphylococcus aureus, S. epidermidis and S. saprophyticus. Compound 6 showed inhibitory effects on Staphylococcus aureus, S. epidermidis and S. saprophyticus MIC values 32, 16 and 16 μg/mL, respectively. All of the compounds didn't show effects on Escherichia coli (MIC > 10 mg/mL). 相似文献