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971.
[structure: see text] A convergent, stereoselective total synthesis of the macrolide antitumor agent rhizoxin D is described. (+)-DIPCl-promoted asymmetric aldol reaction, Evans-Tishchenko 1,3-diol synthesis, modified Julia coupling, and Horner-Wadsworth-Emmons reactions are featured. 相似文献
972.
An innovative in-plane passive micromixer using modified Tesla structures, which are used as passive valves, has been designed, simulated, fabricated and successfully characterized in this paper. Simulation and experimental results of the developed novel micromixer have shown excellent mixing performance over a wide range of flow conditions in the micro scale. The micromixer realized in this work has achieved even better mixing performance at a higher flow rate, and its pressure drop is less than 10 KPa at the flow rate of 100 microl min(-1). This micromixer shows characteristics similar to Taylor dispersion, with contributions from both diffusion and convection. The mixer has a diffusion domain region at low flow rate, but it moves to a convection domain region at high flow rate. Due to the simple in-plane structure of the novel micromixer explored in this work, the mixer can be easily realized and integrated with on-chip microfluidic devices and micro total analysis systems (micro-TAS). 相似文献
973.
Wei Xiang Qi‐Shi Song Hong‐Jie Zhang Rong‐Tao Li Zhi Na Han‐Dong Sun 《Helvetica chimica acta》2004,87(11):2842-2847
A new ursane‐type nortriterpenoid, adenanthusone (=(11α,12α)‐4‐demethyl‐11,12‐epoxy‐3,13‐dihydroxy‐2‐oxoursa‐3,20(30)‐diene‐28‐oic acid γ‐lactone; 1 ) was isolated from Isodon adenanthus. Its structure was determined by NMR spectra and X‐ray crystallographic diffraction analysis. The biogenetic implication of the nortriterpene is discussed. 相似文献
974.
A fast multi‐residue screening method for determining pesticides in tea is described. Pesticides are extracted from tea with acetone and methylene chloride, then enriched and cleaned up with solid phase extraction (SPE) prior to gas chromatographic determination. The fast screening is achieved by a gas chromatograph system equipped with dual‐column, dual‐tower auto‐sampler and both electron capture detector (ECD) and flame photometric detector (FPD). Optimal conditions are investigated for the prospective pesticides including column selection, detection mode, the retention behaviors, quantitative calibration, as well as the recoveries and repeatability of pesticides from tea samples. Under the optimal conditions, with the FPD‐P detector accompanied CP‐SIL 13CB column, 48 pesticides can be separated well and detected within 38 min; and with a DB‐5 column, 35 ECD‐detectable pesticides can be separated and detected within 46 min. The recoveries of 84 pesticides in tea samples are 65–120% with 0.34–16% RSD for spiking 0.02–3.0 mg/kg standard species. Because of the thermal instability of most pesticides, direct cold extraction of pesticides from a tea sample is recommended. The proposed method provided a very fast and efficient procedure to screen 84 pesticides from a complicated tea sample matrix. 相似文献
975.
Hong‐Qing Wang Zhao‐Jie Liu Li‐Min Yang Ming‐Wu Ding 《Journal of heterocyclic chemistry》2004,41(3):393-397
A series of new 1H‐pyrazolo[3,4‐d]pyrimidin‐4(5H)‐one Derivatives 5 has been designed and regio‐selectively synthesized via a tandem aza‐Wittig reaction. The structures of all compounds prepared have been confirmed by 1H NMR, IR, EI‐MS spectroscopy and elemental analyses. The results of preliminary bioassay indicate that most compounds 5 possess an inhibition effect against Botrytis cinereapers and Pyricularia oryzae at the concentration of 50 mg/L. 相似文献
976.
Zhen‐Yi Jiang Xiao‐Hong Xu Hai‐Shun Wu Fu‐Qiang Zhang Zhi‐Hao Jin 《International journal of quantum chemistry》2004,97(4):876-882
Geometric and electronic properties of CmN2 (m = 1–14) clusters have been investigated by density functional theory using the hybrid B3LYP functional and the 6‐311G(d) basis set. Harmonic frequencies for these clusters are given to aid in the characterization of the ground states. These results show that CmN2 (m = 1–14) clusters form linear structures with D∞h symmetry. Two N atoms favor to bond at ends in linear isomers. The chains with odd m have triplet ground states whereas the ones with even m have singlet ground states. The calculated HOMO–LUMO gaps and ionization potentials all show that the CmN2 (m = 1–14) clusters with even m are more stable than those with odd m, which is consistent with the observed even–odd alternation of the time‐of‐flight signal intensities. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献
977.
Hong‐Ze Gao Zhong‐Min Su Chun‐Sheng Qin Ri‐Gen Mo Yu‐He Kan 《International journal of quantum chemistry》2004,97(6):992-1001
Bis(2‐methyl‐8‐quinolinolato)aluminum(III) hydroxide complex (AlMq2OH) is used in organic light‐emitting diodes (OLEDs) as an electron transport material and emitting layer. By means of ab initio Hartree–Fock (HF) and density functional theory (DFT) B3LYP methods, the structure of AlMq2OH was optimized. The frontier molecular orbital characteristics and energy levels of AlMq2OH have been analyzed systematically to study the electronic transition mechanism in AlMq2OH. For comparison and calibration, bis(8‐quinolinolato)aluminum(III) hydroxide complex (Alq2OH) has also been examined with these methods using the same basis sets. The lowest singlet excited state (S1) of AlMq2OH has been studied by the singles configuration interaction (CIS) method and time‐dependent DFT (TD‐DFT) using a hybrid functional, B3‐LYP, and the 6‐31G* basis set. The lowest singlet electronic transition (S0 → S1) of AlMq2OH is π → π* electronic transitions and primarily localized on the different quinolate ligands. The emission of AlMq2OH is due to the electron transitions from a phenoxide donor to a pyridyl acceptor from another quinolate ligand including C → C and O → N transference. Two possible electron transfer pathways are presented, one by carbon, oxygen, and nitrogen atoms and the other via metal cation Al3+. The comparison between the CIS‐optimized excited‐state structure with the HF ground‐state structure indicates that the geometric shift is mainly confined to the one quinolate and these changes can be easily understood in terms of the nodal patterns of the highest occupied and lowest unoccupied molecular orbitals. On the basis of the CIS‐optimized structure of the excited state, TD‐B3‐LYP calculations predict an emission wavelength of 499.78 nm. An absorption wavelength at 380.79 nm on the optimized structure of B3LYP/6‐31G* was predicted. They are comparable to AlMq2OH 485 and 390 nm observed experimentally for photoluminescence and UV‐vis absorption spectra of AlMq2OH solid thin film on quartz, respectively. Lending theoretical corroboration to recent experimental observations and supposition, the reasons for the blue‐shift of AlMq2OH were revealed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献
978.
Yun-Zhi Tang Shao-Song Qian Xi-Sen Wang Hong Zhao Xue-Feng Huang Yong-Hua Li Xing-Cai Jiao Ren-Gen Xiong Prof. Dr. 《无机化学与普通化学杂志》2004,630(11):1623-1626
The in situ hydrolysis of phthalyl-γ-glutaminyl-histidine with Cd(ClO4)2·6H2O in the presence of water and methanol affords a novel two-dimensional cadmium coordination polymer, a new phase, anhydrous cadmium(II) phthalate, ( 1 ). The structure was determined by single crystal X-ray diffraction. Crystal data: P21/c, a = 13.8168(14), b = 7.0351(7), c = 8.2054(8) Å, β = 105.540(2)°, V = 768.43(13) Å3, Z = 4, R1 = 0.0380, wR2 = 0.1111. 相似文献
979.
Poly[[μ2‐aqua‐bis[(1,10‐phenanthroline)nickel(II)]]‐di‐μ2,μ4‐5‐nitro‐1,3‐benzenedicarboxylato]
Hong‐Yin He Yi‐Li Zhou Long‐Guan Zhu 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(11):m569-m571
The reaction of Ni(CH3COO)2·4H2O, 5‐nitro‐1,3‐benzenedicarboxylic acid (H2nmbdc), 1,10‐phenanthroline and water under hydrothermal conditions yields the first reported two‐dimensional nickel coordination polymer with water‐ and carboxylate‐bridged dimeric units, viz. [Ni2(C8H3NO6)2(C12H8N2)2(H2O)]n. The coordination polyhedron of the NiII ion in the title structure is an octahedron defined by an N2O4 donor set. The water molecule is positioned on a mirror plane and the 5‐nitro‐1,3‐benzenedicarboxylate group is located on a twofold axis. Two types of nmbdc2− coordination mode are observed: one is a bis‐monodentate mode, μ2‐nmbdc2−, and the other is a bis‐bridging mode, μ4‐nmbdc2−. The dimeric unit in the title compound is similar to the structural moiety in urease. In the two‐dimensional framework in the title compound, strong stacking interactions between benzene rings (μ2‐nmbdc2− and μ4‐nmbdc2−) and 1,10‐phenanthroline ligands are observed. 相似文献
980.
Pinhasov A Mei J Amaratunga D Amato FA Lu H Kauffman J Xin H Brenneman DE Johnson DL Andrade-Gordon P Ilyin SE 《Combinatorial chemistry & high throughput screening》2004,7(2):133-140
To meet growing needs for high throughput gene expression profiling, we established a new automated high throughput TaqMan RT-PCR method for quantitative mRNA expression analysis. In this method, the Allegro( trade mark ) (Zymark) system conducts all sample tracking and liquid handling steps, and ABI PRISM 7900 HT (Applied Biosystems) is used to conduct real-time determination of the C(t) value when amplification of PCR products is first detected and accumulation of inhibitory PCR products is unlikely to occur. The ABI PRISM 7900 HT Sequence Detection System features a real-time PCR instrument with 384-well-plate compatibility and robotic loading, and continuous wavelength detection, which enables the use of multiple fluorophores in a single reaction. The Allegro System offers an assembly line approach with a modular design that allows reconfiguration of the components to accommodate variations in the assay flow. In the present study, we have established and validated a new automated High Throughput (HT) TaqMan RT-PCR- based method for quantitative mRNA expression analysis. The data demonstrate that HT-Taqman PCR is a powerful tool that can be used for measuring low concentrations of mRNA, and is highly accurate, reproducible, and amenable to high throughput analysis. Results suggest that HT-TaqMan is a reliable method for the quantification of low-expression genes and a powerful tool with HT capability for target identification/validation, structure-activity relationship (SAR) study, compound selection for efficacy studies, and biomarker identification in drug discovery and development. 相似文献