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531.
Chamberlain SD Gerding RM Lei H Moorthy G Patnaik S Redman AM Stevens KL Wilson JW Yang B Shotwell JB 《The Journal of organic chemistry》2008,73(23):9511-9514
A synthetic route to bisanilino-1H-pyrrolo[2,3-d]pyrimidines has been discovered, wherein the C(6)-chloride reactivity is necessarily enhanced via reversible acid-catalyzed internal activation of the pyrimidine ring by a C(1')-carboxamide moiety. Subsequent selective nucleophilic displacements at C(6) and C(1') constitute a one-pot tandem protocol for the rapid assembly of bisanilino-1H-pyrrolo[2,3-d]pyrimidines. 相似文献
532.
Wang W Bray CL Adams DJ Cooper AI 《Journal of the American Chemical Society》2008,130(35):11608-11609
Dry water stores 175 v(STP)/v methane at 2.7 MPa and 273.2 K in a hydrate form which is close to the Department of Energy volumetric target for methane storage. Dry water is a silica-stabilized free-flowing powder (95% wt water), and fast methane uptakes were observed (90% saturation uptake in 160 min with no mixing) as a result of the relatively large surface-to-volume ratio of this material. 相似文献
533.
Rao Y Kemp TF Trudeau M Smith ME Antonelli DM 《Journal of the American Chemical Society》2008,130(46):15726-15731
A multinuclear solid state NMR approach is applied to four templated mesoporous oxides (silica, titania, niobia and tantala) to include (15)N and (17)O magic angle spinning (MAS) NMR and double resonance (15)N-(93)Nb, (17)O Rotational-Echo Adiabatic Passage Double Resonance (REAPDOR). The templated samples were ramped in steps of 20 degrees C for 2 days up to typically 110 degrees C where the samples were left for 2-4 days. (15)N MAS NMR shows that amines are the only species present in the TiO2, Nb2O5, and Ta2O5. In SiO2, amines are only present as a minor coordination (10 +/- 2%), but there are several strong ammonium (15)N resonances. The REAPDOR experiments show that the nitrogen interacts with niobium, confirming a ligand interaction between the Nb and N, as previously believed. In the case of silica, the amine is quaternized and there is apparently no interaction with the Si, suggesting a RNH3(+) (-)O-Si- hydrogen-bonding interaction with the walls. (17)O MAS NMR provides the clearest indication of the local wall structure. In the aged, templated samples in all cases only OM2 coordinations are present which is very different from the pure bulk oxides (apart from SiO2) and must be due to the effects of amine coordination at the metal centers. On removal of the template, these oxides behave differently, with Ta2O5 showing a mixture of OTa2 (85 +/- 5%) and OTa3 (15 +/- 5%) which is similar to the types of coordination found in the bulk oxide. The previously reported (17)O MAS NMR data from heat-treated mesoporous niobia shows only ONb2, which is very highly ordered. In contrast for titania, the OTi2 coordination is immediately lost on removal of the template to be replaced by a mixture of OTi3 (60 +/- 5%) and OTi4 (40 +/- 5%), with the OTi4 becoming dominant above 250 degrees C, very different behavior from the corresponding bulk oxide. In summary, this NMR study shows that the local oxygen coordination in amine-templated mesoporous transition metal oxides is present as OM2 which is relatively rare in bulk oxides. The data indicates that the template interaction is largely controlled by the N-M dative bond to the wall, suppressing higher oxygen coordination numbers. Qualitatively it appears that the strength of this interaction varies greatly in the different mesoporous oxides. 相似文献
534.
Simmons K Kinney J Owens A Kleier D Bloch K Argentar D Walsh A Vaidyanathan G 《Journal of chemical information and modeling》2008,48(8):1663-1668
High-throughput screening (HTS) has become a central tool of many pharmaceutical and crop-protection discovery operations. If HTS screening is carried out at the level of the intact organism, as is commonly done in crop protection, this strategy has the potential of uncovering a completely new mechanism of actions. The challenge in running a cost-effective HTS operation is to identify ways in which to improve the overall success rate in discovering new biologically active compounds. To this end, we describe our efforts directed at making full use of the data stream arising from HTS. This paper describes a comparative study in which several machine learning and chemometric methodologies were used to develop classifiers on the same data sets derived from in vivo HTS campaigns and their predictive performances compared in terms of false negative and false positive error profiles. 相似文献
535.
Miller CW Li ZP Schuller IK Dave RW Slaughter JM Akerman J 《Physical review letters》2007,99(4):047206
Precisely engineered tunnel junctions exhibit a long sought effect that occurs when the energy of the electron is comparable to the potential energy of the tunneling barrier. The resistance of metal-insulator-metal tunnel junctions oscillates with an applied voltage when electrons that tunnel directly into the barrier's conduction band interfere upon reflection at the classical turning points: the insulator-metal interface and the dynamic point where the incident electron energy equals the potential barrier inside the insulator. A model of tunneling between free electron bands using the exact solution of the Schr?dinger equation for a trapezoidal tunnel barrier qualitatively agrees with experiment. 相似文献
536.
Shantanu Dave 《Mathematische Nachrichten》2010,283(11):1575-1588
We use spectral theory to produce embeddings of distributions into algebras of generalized functions on a closed (compact without boundary) Riemannian manifold. These embeddings are invariant under isometries and preserve the singularity structure of the distributions (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
537.
Synthesis and Mesomorphic Characteristics of Fluoroaniline Derivatives with Different Lateral Groups
Jayrang S. Dave Purvang D. Patel Himanshu Bhatt 《Molecular Crystals and Liquid Crystals》2013,570(1):76-84
Two new homologous series of liquid crystals viz. 4-(4'-n-alkoxybenzoyloxy)-2-chlorophenylazo-4”-fluorobenzenes(I) and 4-(4'-n-alkoxybenzoyloxy)-2-methylphenyl azo-4”-fluorobenzenes(II) with terminal fluoro, lateral chloro(I) and methyl(II) group and central ester and azo linkages are synthesized and their mesomorphic properties are studied. Both the series are similar in molecular structure with the difference in their lateral substitutions; series I has chloro group and series II has methyl group as laterally substituted groups. All the twelve homologues of each of the series are mesogenic in nature. Series I shows nematic mesophase from the first C1 to the last C16 derivative synthesized; smectic mesophase is exhibited by last two viz. C14 and C16 derivative, where as all the members from C1 to C16 of series II only show nematic mesophase. The nematic mesophase shows marble texture and the smectic mesophase shows Schlirene texture of the Smectic C variety. Both the series are compared with structurally related series. 相似文献
538.
Dave Mangindaan Wei‐Hsuan Kuo Hengky Kurniawan Meng‐Jiy Wang 《Journal of Polymer Science.Polymer Physics》2013,51(18):1361-1367
A chemical gradient possessing gradual change of amine concentration for every 100 carbon atoms (NHx/100 C) from 4.03 to 1.98 was prepared by plasma polymerization of allylamine on polypropylene films. Electron spectroscopy for chemical analysis and water contact angle (WCA) measurements revealed that the nitrogen incorporation resulted in the amine functionality (C? N binding) and, therefore, the formation of the wettability gradient. The gradient showed the WCAs varied from 15° to 90° as the change of amine concentration on the gradient from the nitrogen rich end to the nitrogen deprived end. Furthermore, the interactions between the gradient with mammalian cells revealed that more than twofold cell density was found at the nitrogen rich end when compared with the nitrogen deprived end. Plasma polymerization was demonstrated as an effective method to create controllable chemical gradient and the obtained allylamine gradient was useful for biomaterial applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1361–1367 相似文献
539.
State-of-the-art automatic speech recognition (ASR) systems follow a well established statistical paradigm, that of parameterization of speech signals (a.k.a. feature extraction) at front-end and likelihood evaluation of feature vectors at back-end. For feature extraction, Mel-frequency cepstral coefficients (MFCC) and perceptual linear prediction (PLP) are the two dominant signal processing methods, which have been used mainly in ASR. Although the effects of both techniques have been analyzed individually, it is not known whether any combination of the two can produce an improvement in the recognition accuracy or not. This paper presents an investigation on the possibility to integrate different types of features such as MFCC, PLP and gravity centroids to improve the performance of ASR in the context of Hindi language. Our experimental results show a significant improvement in case of such few combinations when applied to medium size lexicons in typical field conditions. 相似文献
540.
Polymeric complexes of copper (II) with some orthohydroxy thiosemicarbazones (H2L), such as 2-OH-5-Me (C1), aceto/propiophenone thiosemicarbazones with some bases (B), viz., pyridine; α-, β-, γ-picolines; piperidine; morpholine and bidentate bases; bipy and o-phen, have been isolated and characterized. The analytical data shows them to have 1: 1: 1 composition of Cu:L:B. Their thermal, spectral, and magnetic properties are studied. 相似文献