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951.
El Sayed H. El Ashry Atta-ur-Rahman M. Iqbal Choudhary Sherif H. Kandil Ahmed El Nemr Tahsin Gulzar Aida H. Shobier 《Chemistry of Natural Compounds》2011,47(3):335-338
Phytochemical investigations on a marine green alga Ulva lactuca led to the isolation of two new compounds (E)-6-heptacosen-5-one (1) and (E)-6-octadecen-5-ol (2), along with four known compounds, (Z)-10-hexacosene (3), docosanoic acid (4), palmitic acid (5), and isofucosterol (6). Compounds 3 and 4 were isolated for the first time from this species. The structures of the compounds were deduced with the help of modern
spectroscopic techniques. 相似文献
952.
On the Reactivity of (−)‐(R)‐Carvone and (−)‐4aα,7α,7aβ‐Nepetalactone: Synthesis of New Heterocycles
Aziz El Mebtoul Mohamed Rouani Malika Chammache Houcine Bouidida Abdelkader Ilidrissi 《Helvetica chimica acta》2011,94(3):433-437
The 1,3‐dipolar cycloaddition of 4‐chlorobenzonitrile oxide to the unsaturated system of (?)‐(R)‐carvone occurred exclusively at C(8) to give a new isoxazoline derivative. This derivative reacts with NH2OH to yield a new heterocycle, observed for the first time. On the other hand, the addition of 4‐chlorobenzonitrile oxide to the unsaturated lactone (?)‐4aα,7α,7aβ‐nepetalactone gave, in a good yield, also a new heterocycle, again obtained for the first time. The terpenoid (?)‐(R)‐carvone and iridoid (?)‐4aα,7α,7aβ‐nepetalactone were isolated from Moroccan species Mentha viridis (L.) and Nepeta tuberosa (L.), respectively. The new heterocycles obtained were identified by combination of chromatographic and spectroscopic methods. 相似文献
953.
Hassan Valizadeh Ashkan Shomali Hamid Gholipour 《Journal of heterocyclic chemistry》2011,48(6):1440-1444
A simple and efficient method was developed for the reaction of dimethyl acetylenedicarboxylate with benzothiazole, isoquinoline, quinoline, 3‐bromopyridine, pyridine, benzoxazole, benzimidazole, and 5,6‐dimethyl benzimidazole for the high‐yield synthesis of the related heterocyclic products ( 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ) in very short reaction time under neat procedure. The reaction of isoquinoline, 3‐bromopyridine, and pyridine afforded to diastereomeric mixtures of products 2 , 4 , and 5 , respectively. However, only one isomer of products 1 , 3 , 6 , 7 , and 8 were identified from the reaction of benzothiazole, quinoline, benzoxazole, benzimidazole, and 5,6‐dimethyl benzimidazole, respectively. Benzotriazole afforded to product 9 under these conditions. For comparison, the reactions were examined in different reaction mediums and/or under microwave irradiation. J. Heterocyclic Chem., (2011). 相似文献
954.
Mostafa M. Ghorab Mansour S. Al‐Said Ebaa M. El‐Hossary 《Journal of heterocyclic chemistry》2011,48(3):563-571
Sulfonamide‐bearing compounds posses many types of biological activities and have been recently reported to show substantial antitumor activity in vitro and/or in vivo. There are a variety of mechanisms for the anticancer activity, and the most prominent mechanism is the inhibition of carbonic anhydrase isozymes. This work reports the synthesis of some new quinoline, pyrimido[4,5‐b]quinoline and 3,1‐oxazinoquinoline derivatives bearing a sulfonamide moiety. All the newly synthesized compounds were evaluated for their in vitro anticancer activity against Ehrlich ascites carcinoma cells. Compounds 10 , 13 , and 26 were the most active compounds with IC50 values of 6.1 μM, 6.8 μM, and 6.4 μM, respectively, and exhibited better activities than the reference drug doxorubicin (IC50 = 68.1 μM). J. Heterocyclic Chem., 2011. 相似文献
955.
The structure and thermodynamic properties of lanthanide complexes with a new tripodal ligand L2 have been elucidated using different physicochemical methods. At stoichiometric ratios, the tetrahedral three-dimensional complexes with lanthanide cations are formed in acetonitrile with good stabilities. Despite minor structural changes comparing to previously investigated tripodal ligands, the resulting assembly exhibits different features revealed with the crystal structure of [Eu(4)L2(4)](OH)(ClO(4))(11) (orthorhombic, Pbcn). Interestingly, the highly charged edifice contains an inner cage encapsulating a perchlorate anion. Such lanthanide mediated cage-like assemblies are rare, and may be of interest for different sensing applications. Indeed, the anionic guest can be exchanged with different anions. The related host-guest equilibria were investigated with NMR techniques. Various aspects of these reactions are qualitatively discussed. 相似文献
956.
Chen P El Ojaimi M Gros CP Richard P Barbe JM Guilard R Shen J Kadish KM 《Inorganic chemistry》2011,50(8):3479-3489
A series of homobimetallic manganese cofacial porphyrin-corrole dyads were synthesized and investigated as to their electrochemistry, spectroelectrochemistry, and ligand binding properties in nonaqueous media. Four dyads were investigated, each of which contained a Mn(III) corrole linked in a face-to-face arrangement with a Mn(III) porphyrin. The main difference between compounds in the series is the type of spacer, 9,9-dimethylxanthene, anthracene, dibenzofuran, or diphenylether, which determines the distance and interaction between the metallomacrocycles. Each redox process of the porphyrin-corrole dyads was assigned on the basis of spectroscopic and electrochemical data and by comparison with reactions and properties of the monocorrole and the monoporphyrin which were examined under the same solution conditions. The Mn(III) porphyrin part of the dyad undergoes two major one-electron reductions in pyridine and benzonitrile, the first of which involves a Mn(III)/Mn(II) process and the second the addition of an electron to the conjugated π-ring system of the macrocycle. The Mn(III) corrole part of the dyads also exhibits two major redox processes, one involving Mn(III)/Mn(II) and the other Mn(III) to Mn(IV) under the same solution conditions. The potentials and reversibility of each electron transfer reaction were shown to depend upon the solvent, type of spacer separating the two macrocycles, and the presence or absence of axial ligation, the latter of which was investigated in detail for the case of acetate ion which was found to bind within the cavity of the dyad to both manganese centers, both before and after the stepwise electroreduction to the Mn(II) forms of the two macrocycles. An intramolecular chloride ion exchange between the porphyrin part of the dyads which contain Mn(III)Cl and the singly oxidized corrole in the dyad is observed after the Mn(III)/Mn(IV) reaction of the corrole, suggesting that chloride is coordinated inside the cavity in the neutral compound. 相似文献
957.
Hamilton JM Whitehead JR Williams NJ El Ojaimi M Thummel RP Hancock RD 《Inorganic chemistry》2011,50(8):3785-3790
DPA (dipyrido[4,3-b;5,6-b]acridine) may be considered as a tridentate homologue of phen (1,10-phenanthroline). In this paper some of the metal ion complexing properties of DPA in aqueous solution are reported. Using UV-visible spectroscopy to follow the intense π-π* transitions of DPA as a function of pH gave protonation constants at ionic strength (μ) = 0 and 25 °C of pK(1) = 4.57(3) and pK(2) = 2.90(3). Titration of 10(-5) M solutions of DPA with a variety of metal ions gave log K(1) values as follows: Zn(II), 7.9(1); Cd(II), 8.1(1); Pb(II), 8.3(1); La(III), 5.23(7); Gd(III), 5.7(1); Ca(II), 3.68; all at 25 °C and μ = 0. Log K(1) values at μ = 0.1 were obtained for Mg(II), 0.7(1); Sr(II), 2.20(1); Ba(II), 1.5(1). The log K(1) values show that the high level of preorganization of DPA leads to complexes 3 log units more stable than the corresponding terpyridyl complexes for large metal ions such as La(III) or Ca(II), but that for small metal ions such as Mg(II) and Zn(II) such stabilization is minimal. Molecular mechanics calculations (MM) are used to show that the best-fit M-N length for coordination with DPA is 2.60 ?, accounting for the high stability of Ca(II) or La(III) complexes of DPA, which are found to have close to this M-N bond length in their phen complexes. 相似文献
958.
Rami Suleiman Abdelletif Ibdah Bassam El Ali 《Journal of organometallic chemistry》2011,696(11-12):2355-2363
A DFT study on the palladium-bisphosphine catalyzed alkoxycarbonylation and aminocarbonylation of alkyne (propyne) is reported. The theoretical study explores the feasibility and the regioselectivity control of two independent mechanisms: the first is based on the active intermediate [Pd(II)(P2)(H)]+ (where P2 = PH2CH2CH2CH2CH2PH2) for the alkoxycarbonylation reaction, and the second is based on the active species [Pd(II)(P2)(NR2)]+ for the aminocarbonylation reaction. The study explains the role of solvent in increasing the yield and in controlling the selectivity of reaction to produce selectively the trans isomer in the alkoxycarbonylation reaction (hydride cycle) and the gem isomer in the aminocarbonylation reaction (amine cycle). In hydride cycle, the regioselectivity is mainly determined by the stability of the complex [Pd(II)(P2)(COC3H5)(CH3CN)]+; however, for the amine cycle, the regioselectivity is determined by the stability of the complex [Pd(II)(P2)(C3H5CON(CH3)2)]+. The calculations reveal that ligand simplification is not valid in addressing the regioselectivity behavior of alkoxycarbonylation and aminocarbonylation reactions. The kinetic data for the formation of the two key complexes show no difference between the gem and trans isomers which predict the regioselectivity to be a thermodynamically controlled process. 相似文献
959.
960.
Salah-ud-din Ghulam Mohi-ud-Din Atif Bin Mansoor Hassan Masood Mustafa Mumtaz 《Signal, Image and Video Processing》2011,5(4):477-483
The ever increasing demand of security has resulted in wide use of Biometric systems. Despite overcoming the traditional verification
problems, the unimodal systems suffer from various challenges like intra class variation, noise in the sensor data etc, affecting
the system performance. These problems are effectively handled by multimodal systems. In this paper, we present multimodal
approach for palm- and fingerprints by feature level and score level fusions (sum and product rules). The proposed multi-modal
systems are tested on a developed database consisting of 440 palm- and fingerprints each of 55 individuals. In feature level
fusion, directional energy-based feature vectors of palm- and fingerprint identifiers are combined to form joint feature vector
that is subsequently used to identify the individual using a distance classifier. In score level fusion, the matching scores
of individual classifiers are fused by sum and product rules. Receiver operating characteristics curves are formed for unimodal
and multimodal systems. Equal Error Rate (EER) of 0.538% for feature level fusion shows best performance compared to score
level fusion of 0.6141 and 0.5482% of sum and product rules, respectively. Multimodal systems, however, significantly outperform
unimodal palm- and fingerprints identifiers with EER of 2.822 and 2.553%, respectively. 相似文献