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991.
Yong Xia Lili Lin Fenzhen Chang Xuan Fu Xiaohua Liu Xiaoming Feng 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(46):13952-13956
A highly efficient asymmetric ring‐opening reaction of cyclopropyl ketones with a broad range of thiols, alcohols and carboxylic acids has been first realized by using a chiral N,N′‐dioxide–scandium(III) complex as catalyst. The corresponding sulfides, ethers, and esters were obtained in up to 99 % yield and 95 % ee. This is also the first example of one catalytic system working for the ring‐opening reaction of donor–acceptor cyclopropanes with three different nucleophiles, let alone in an asymmetric version. 相似文献
992.
Interfacial bonding mechanism and bonding strength of AlTiCrN coating by cathodic arc ion plating
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AlTiCrN coating was prepared on the surface of YT14 tungsten carbide cutting tools by cathodic arc ion plating with Ti, Al and Cr as targets. The surface morphologies, interface energy spectrum, phase and elements' binding energy of the coatings were observed with SEM, EDS, XRD and XPS, respectively, and bonding strength of the coating interface was measured with scratch tester. The results show that the phases of AlTiCrN coating are mainly composed of AlN, CrN and TiN, the crystal plane of (111) has a strong preferred orientation. The concentrations of Al, Ti, Cr, N in the coating are higher than those in the substrate, showing the gradient diffusion distribution at the bonding interface, while C atoms of the substrate have diffused into the lattices of TiN, AlN and CrN to form an obvious interdiffusion layer, and the average bonding strength of coating interface is 57.65 N. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
993.
Biocatalytic Synthesis of the Anti‐diabetes Agent‐corosolic Acid by Whole Cells of Microorganisms
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Diabetes is one of the most prevalent and costly global diseases. For diabetes, frequent insulin treatment and synthetic drugs are very expensive and may cause unwanted side effects. Corosolic acid (CA), a natural product, was reported to be efficient in the treatment of diabetes, meanwhile without induction of anti‐insulin antibodies and obesity. The preparation of CA attracted many researchers in the world. This study investigated the biocatalytic synthesis method of CA from ursolic acid by Streptomyces griseus subsp. griseus 4.18. LC? MS analysis demonstrated that 5 day, 125 μg/mL substrate, pH=9 and 10% strain concentration were the appropriate conditions. It is estimated that biocatalysis will contribute to the development of green and sustainable synthetic processes with less time‐consuming and more environmentally friendly. 相似文献
994.
Shao‐Fu Yu Xiao‐Jun Huang Shu‐Na Fu Chun Wu Wen‐Cai Ye Guang‐Xiong Zhou 《Helvetica chimica acta》2015,98(9):1267-1272
One new lactone, cyclopentanepyrone A ( 1 ), and two new monoterpenoids, gardeterpenone A ( 2 ) and jasminoside V ( 3 ), were isolated from the fruits of Gardenia jasminoides var. radicans, along with four known monoterpenoids, 4 – 7 , which were isolated from this plant for the first time. The structures of the isolates were elucidated by extensive spectroscopic studies, including UV, IR, 1D‐ and 2D‐NMR, ESI‐MS, HR‐ESI‐MS, and CD experiments. 相似文献
995.
Three mono-, bi- and tetranuclear copper(I) complexes, [Cu(phen)(triphos-O)]BF4 (1) (phen = 1,10-phenanthroline, triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane), [Cu2(bipy)(triphos)2](BF4)2 (2) (bipy = 4,4′-bipyridine), and [Cu4(MeOC^N^N)4(triphos)2(bipy)](BF4)4 (3) (MeOC^N^N = 6-(4-methoxyphenyl)-2,2′-bipyridine), have been synthesized and characterized by NMR spectroscopy, electrospray ionization, and matrix-assisted laser desorption ionization time-of-flight mass spectrometries, elemental analysis, and X-ray crystal analysis. The crystal structure investigation revealed the copper ions of the complexes have pseudo-tetrahedral coordination geometry. The electronic absorption spectra of 1, 2, and 3 contain low-energy bands at 350–500 and 400–650 nm, which are assigned to d(Cu) → π*(phen or bipy) and a mixture of d(Cu) → π*(MeOC^N^N) and d(Cu) → π*(bipy) transitions, respectively. Complex 2 displays a strong, long-lived solid-state emission with a maximum at 555 nm and lifetime of 13.6 μs at room temperature. Photoinduced electron-transfer properties of 2 and 3 involving nanosecond time-resolved absorption spectroscopy and electron spin resonance techniques were studied. 相似文献
996.
An ascorbic acid (AA) amperometric sensor was fabricated based on a glassy carbon electrode (GCE) modified with a reduced graphene oxide-wrapped hierarchical TiO2 (RGO—TiO2) nanocomposite. The RGO—TiO2 nanocomposite was synthesized via the facial wet chemical method and characterized by scanning electron microscopy and X-ray diffraction. Cyclic voltammetry and amperometric techniques were employed to investigate its electrocatalytic performance towards the AA oxidation. The combined advantages of RGO and TiO2 provide the electrode with higher current response and lower oxidation potential compared with those of bare GCE and TiO2 modified GCE. The proposed electrode can be used for the determination of AA in the wide concentration range from 1 to 1500 µM with the detection limit of 0.5 µM. The proposed electrode was successfully used to determine AA in vitamin C tablets and spiked fruit juice. 相似文献
997.
998.
Nucleophilic β‐Carbon Activation of Propionic Acid as a 3‐Carbon Synthon by Carbene Organocatalysis
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Dr. Zhenqian Fu Prof. Dr. Jaume Torres Pengcheng Zheng Prof. Dr. Song Yang Prof. Dr. Bao‐An Song Prof. Dr. Yonggui Robin Chi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9360-9363
Direct β‐carbon activation of propionic acid (C2H5CO2H) by carbene organocatalysis has been developed. This activation affords the smallest azolium homoenolate intermediate (without any substituent) as a 3‐carbon nucleophile for enantioselective reactions. Propionic acid is an excellent raw material because it is cheap, stable, and safe. This approach provides a much better solution to azolium homoenolate synthesis than the previously established use of acrolein (enal without any substituent), which is expensive, unstable, and toxic. 相似文献
999.
Stochastic/Controlled Symmetry Breaking of the T8‐POSS Cages toward Multifunctional Regioisomeric Nanobuilding Blocks
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Xiao‐Man Wang Qing‐Yun Guo Shuai‐Yuan Han Jing‐Yi Wang Di Han Prof. Qiang Fu Prof. Wen‐Bin Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15246-15255
Precise synthesis of nanobuilding blocks with accurately positioned functional groups presents a daunting challenge. Herein, a practical synthesis and thorough characterization of a series of T8‐polyhedral oligomeric silsesquioxane (POSS) di‐ and triadducts is reported. Upon addition of triflic acid across the double bonds in octavinylPOSS (V8T8) followed by hydrolysis, the cubic symmetry of the T8‐POSS cage (Oh) is broken into C2v (ortho‐), C2v (meta‐), and D3d (para‐) for diadducts and further to Cs (oom‐), Cs (omp‐), and C3v (mmm‐) for triadducts in a stochastic fashion. Their structures and regioconfigurations have been unambiguously demonstrated by 1H, 13C, and 29Si NMR spectroscopy, as well as MALDI‐TOF mass spectrometry. The assignment of the diadducts was further corroborated by converting each individual diadduct into triadduct(s), the structure of which is controlled by the symmetry of the precursor. Except for the C3v triadduct, they can all be prepared in synthetically useful quantities. The presence of two types of highly reactive and mutually orthogonal functional groups facilitates further modification into complex nanostructures and composite materials. These unique regioisomers provide a versatile platform for constructing giant molecules and Janus silsesquioxanes. 相似文献
1000.
Ansa‐Complexes of [Mn(η5‐C5H5)(η6‐C6H6)]: Preparation,Characterization, and Reactivity of [n]Manganoarenophanes (n=1, 2, 3)
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Prof. Dr. Holger Braunschweig Dr. Alexander Damme Dr. Klaus Dück Dr. Marco Fuß Dr. Christian Hörl Dr. Thomas Kramer Dr. Ivo Krummenacher Dr. Thomas Kupfer Valerie Paprocki Christoph Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14797-14803
We report the synthesis of [n]manganoarenophanes (n=1, 2) featuring boron, silicon, germanium, and tin as ansa‐bridging elements. Their preparation was achieved by salt‐elimination reactions of the dilithiated precursor [Mn(η5‐C5H4Li)(η6‐C6H5Li)]?pmdta (pmdta=N,N,N′,N′,N′′‐pentamethyldiethylenetriamine) with corresponding element dichlorides. Besides characterization by multinuclear NMR spectroscopy and elemental analysis, the identity of two single‐atom‐bridged derivatives, [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] and [Mn(η5‐C5H4)(η6‐C6H5)SiPh2], could also be determined by X‐ray structural analysis. We investigated for the first time the reactivity of these ansa‐cyclopentadienyl–benzene manganese compounds. The reaction of the distannyl‐bridged complex [Mn(η5‐C5H4)(η6‐C6H5)Sn2tBu4] with elemental sulfur was shown to proceed through the expected oxidative addition of the Sn?Sn bond to give a triatomic ansa‐bridge. The investigation of the ring‐opening polymerization (ROP) capability of [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] with [Pt(PEt3)3] showed that an unexpected, unselective insertion into the Cipso?Sn bonds of [Mn(η5‐C5H4)(η6‐C6H5)SntBu2] had occurred. 相似文献