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991.
Anastasia A. Selina Sergey S. Karlov Ekaterina V. Gauchenova Andrei V. Churakov Lyudmila G. Kuz'mina Judith A. K. Howard Jörg Lorberth Galina S. Zaitseva 《Heteroatom Chemistry》2004,15(1):43-56
Reactions of element-substituted alkynes R3MCCPh (R3M = Me3Si, Et3Si, Ph3Si, Et3Ge, n-Bu3Sn, N(CH2CH2O)3Si, N(CH2CH2O)3Ge, N(CH2-CHMeO)3Ge, and N(CH2CH2O)2(CH2CHPhO)Ge) with bromine, tetra-n-butylammonium tribromide (TBAT), and N-bromosuccinimide (NBS)/DMSO were investigated. The Z,E-ratio of isomeric dibromoalkenes formed in bromination reaction with Br2 and TBAT are discussed. The crystal structures of N(CH2CH2O)3SiCCPh and N(CH2CHMeO)3GeX (X = C CPh, C(Br)C(Br)Ph, C(Br2)C(O)Ph), and Ph3SiC(Br)C(Br)Ph are reported. © 2003 Wiley Periodicals, Inc. 15:43–56, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10211 相似文献
992.
Jan Rijn Zeevaart Judith Marie Wagener Maria Neves Maria Ceu Costa Cristina Rodrigues Mildred Dithebe Elmaré Kilian Ignacy Cukrowski 《Journal of Radioanalytical and Nuclear Chemistry》2010,283(1):123-131
99mTc-DMSA (dimercaptosuccinic acid) is known to be a safe and effective agent for static renal imaging. However, it has a long
uptake time which is a limiting factor in diagnostic procedures and also leads to a relatively high radiation dose being administered
to patients. There is a constant search for possible new renal imaging agents with a good resolution, kidney/liver contrast
and low radiation dose to all organs. A series of biguanide derivatives (potential as non-insulin-dependent diabetes mellitus
agents) labelled with 99mTc were investigated as potential alternative kidney-imaging agents on theoretical grounds (in silico) and their biodistribution (in vivo) verified in a limited number of animal experiments. Such a dual approach has the benefit
that it reduces the number of animal experiments needed to evaluate a potential radiopharmaceutical. The blood plasma model
shows little or no complexation of the biguanide type ligands by the metal ions in blood plasma. It was therefore expected
that these ligands will clear rapidly through the kidneys and liver (increased lipophilicity). These predictions were verified
by studies on single vervets comparing them with 99mTc-DMSA as gold standard. All the biguanide derivatives labelled with 99mTc show liver, kidney and gallbladder uptake in vervets. It was shown that the agent 99mTc-CBIG (carboxylbiguanide) has a very fast kidney clearance, which will reduce the dose to organs (as experienced for 99mTc-DMSA), although it’s potential as a kidney agent is limited by its gallbladder uptake. 相似文献
993.
DETECTION OF UVR-INDUCED DNA DAMAGE IN MOUSE EPIDERMIS in vivo USING ALKALINE ELUTION 总被引:1,自引:0,他引:1
Judith S. Kinley Gunnar Brunborg Johan Moan Antony R. Young 《Photochemistry and photobiology》1995,61(2):149-158
Abstract— Alkaline elution has been used to detect ultraviolet radiation (UVR)-induced DNA damage in the epidermis of C3H/Tif hr/hr mice. This technique detects DNA damage in the form of single-strand breaks and alkali-labile sites (SSB) formed directly by UVA (320–400 nm) or indirectly by UVB (280–320 nm). The latter induces DNA damage such as cyclobutane pyrimidine dimers and pyrimidine-pyrimidone (6–4)-photoproducts, which are then converted into transient SSB by cellular endonucleases, during nucleotide excision repair (NER). The irradiation system used had a spectral output similar in effect to solar UVR, with the UVB component inducing 94% of the edema response observed in mice. Consequently, the majority of SSB detected were those formed via NER of UVB-induced photoadducts. The number of SSB detected immediately after 8 kj/m2 (2.7 minimum erythema doses determined at 48 h post-UVR [MED]) was low, indicating the formation of only small numbers of transient SSB. When DNA repair inhibitors hydroxyurea and 1 -β-D-arabinofuranosylcytosine were administered (intraperi-toneally) to mice 30 min before UVR, they prevented sealing of the DNA SSB formed during NER. A four-fold increase in the number of SSB detected resulted, which was found to be linearly related to the UVR dose. The SSB induced by 2 kj/m2 (less than an MED) were readily detected, with the ear showing lower numbers of SSB than the dorsum. When repair inhibitors were added post-UVR, the rate of formation of SSB declined rapidly with time of administration, reflecting repair of DNA lesions. After a UVR dose of 6 kj/m2 (2 MED), 50% of the initial repair-dependent SSB had been removed after approximately 2 h in the ear and 4 h in the dorsum; no more SSB appeared to be incised by 24 h post-UVR. The technique described is an efficient and highly sensitive one for the quantification of SSB induced in UV-irradiated skin samples in vivo. 相似文献
994.
995.
Thompson LK Kelly TL Dawe LN Grove H Lemaire MT Howard JA Spencer EC Matthews CJ Onions ST Coles SJ Horton PN Hursthouse MB Light ME 《Inorganic chemistry》2004,43(24):7605-7616
Mn(II)9 grid complexes with a [Mn9(mu-O)12] core, obtained by self-assembly of a series of tritopic picolinic dihydrazone ligands with Mn(II) salts, have been oxidized by both chemical and electrochemical methods to produce mixed oxidation state systems. Examples involving [Mn(III)3Mn(II)6] and [Mn(III)4Mn(II)5] combinations have been produced. Structures are reported for [Mn9(2poap-2H)6](NO3)6.14H2O (1), [Mn9(2poap-2H)6](ClO4)10.10H2O (3), and [Mn9(Cl2poap-2H)6](ClO4)9.14H2O.3CH3CN (10). Structural studies show distinct contraction of the corner grid sites on oxidation, with overall magnetic properties consistent with the resulting changes in electron distribution. Antiferromagnetic exchange in the outer ring of eight metal centers creates a ferrimagnetic subunit, which undergoes antiferromagnetic coupling to the central metal, leading to S=1/2 (3) and S2/2 (10) ground states. Two moderately intense absorptions are observed on oxidation of the Mn(II) grids in the visible and near-infrared (1000 nm, 700 nm), associated with charge transfer transitions (LMCT, IVCT respectively). Compound 1 crystallized in the monoclinic system, space group P2 1/n, with a=21.308(2) A, b=23.611(2) A, c=32.178(3) A, beta=93.820(2) degrees . Compound 3 crystallized in the tetragonal system, space group I, with a=b=18.44410(10) A, c = 24.9935(3) A. Compound 10 crystallized in the triclinic system, space group P, with a=19.1150(10) A, b=19.7221(10) A, c=26.8334(14) A, alpha=74.7190(10) degrees, beta=77.6970(10) degrees, gamma=64.7770(10) degrees. The facile oxidation of the Mn(II)9 grids is highlighted in terms of their potential use as molecular based platforms for switching and data storage. 相似文献
996.
Hugo A. López-Peña Lindsay S. Hernández-Muñoz Judith Cardoso Felipe J. González Ignacio González Carlos Frontana 《Electrochemistry communications》2009,11(7):1369-1372
In this work, an electrochemical and ESR-spectrochemical study of the oxidation properties for nitroxide radicals contained in the structure of poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidin-N-oxyl) (PTMA) in acetonitrile solution was performed. Results revealed that this polymer contains two types of nitroxide radical species, the first associated to a multielectronic and reversible electron transfer process. Remaining radical species are irreversibly oxidized at more positive potential values. Proportions obtained for the respective amount of each oxidized species, 78% and 22% respectively, are similar to the values expected due to the difference in syndiotactic:heterotactic triads in the polymer and reported values for the experimental charge/discharge efficiencies of batteries constructed with this material. These effects also influence electron transfer kinetics during the oxidation of each type of radical species in the polymer. These findings suggest that the detailed understanding of the oxidation processes of different microstructures in radical polymers is useful to analyze performance based in these materials. 相似文献
997.
Olivia F. Koentjoro Philipp Zuber Horst Puschmann Andres E. Goeta Judith A. K. Howard Paul J. Low 《Journal of organometallic chemistry》2003,670(1-2):178-187
Palladium–copper catalysed cross-coupling reactions of tetracholoroethene with terminal acetylenes RCCH (R=SiMe3, C6H5, C6H4CN-4) in refluxing triethylamine afford the corresponding tetraethynylethenes in 30–60% isolated yields. The reaction of 1,6-bis(trimethylsilyl)-3,4-bis(trimethylsilylethynyl)-hex-3-ene-1,5-diyne with [Co2(CO)6(L2)] [L2=(CO)2 or μ-dppm] affords complexes in which one or two (trans) acetylene moieties are coordinated by a dicobalt fragment. 相似文献
998.
Andrei S. Batsanov Judith A. K. Howard David O'Hagan Mustafa Tavasli 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):e512-e513
The title compound [alternative name: 8‐methyl‐8‐azabicyclo[3.2.1]octan‐3‐ylmethyl p‐toluenesulfonate(N8—B)–borane], C16H26BNO3S, has the tosyloxymethyl substituent in an endo position. The BH3 group is equatorial and the (N‐bonded) methyl group is axial, relative to the six‐membered heterocycle. The N—B bond of 1.649 (8) Å is one of the longest known. 相似文献
999.
The binding of propylene oxide (PO) to a series of metal cations LM(III)(+), where for L = tetraphenylporphyrin (TPP) M = Al, Ga, Cr, and Co, and for L = (R,R)-N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexenediamine (salen) M = Al and Cr, was studied in the gas phase by electrospray tandem mass spectroscopy, and the relative stabilities of LM(PO)(2)(+) and LM(PO)(+) cations were determined. The chromium(III) and aluminum(III) cations most tenaciously bind PO, and for M = Al, coordination to the TPP ligated metal center was favored relative to salen. For (TPP)M(PO)(2)(+), the dissociation of PO followed the order M = Al > Cr, but for (TPP)M(PO)(+) the dissociation was M = Cr > Al. The single-crystal structural determinations on (R,R-salen)AlOCHMe(S)CH(2)Cl.0.5PO and (R,R-salen)AlO(2)CMe.1.5py grown in neat PO and pyridine, respectively, reveal five-coordinate aluminum(III) centers with the alkoxide/acetate ligands in the axial position of a square-based pyramid. These results are discussed in terms of the reactivity of these metal complexes in ring-opening polymerizations and copolymerizations with PO and CO(2), respectively. 相似文献
1000.
Batsanov AS Collings JC Fairlamb IJ Holland JP Howard JA Lin Z Marder TB Parsons AC Ward RM Zhu J 《The Journal of organic chemistry》2005,70(2):703-706
Palladium-catalyzed terminal alkyne dimerization, through oxidative homocoupling, is a useful approach to the synthesis of symmetrical 1,4-diynes. Recent investigations have suggested that this reaction might be accomplished in the absence of intentionally added stoichiometric oxidants (to reoxidize Pd(0) to Pd(II)). In this paper, we have fully addressed the question of whether oxygen (or added oxidant) is required to facilitate this process. The presence of a stoichiometric quantity of air (or added oxidant such as I2) is essential for alkyne dimerization. Excess PPh3 inhibits alkyne dimerization to enyne, which only occurs to a significant extent when the reaction is starved of oxidant. Theoretical studies shed more light on the requirement for an oxidant in the homocoupling reaction in order for the process to be theromodynamically favorable. The employment of I2 as the stoichiometric oxidant appears to be the method of choice. The dual role of Cu both in transmetalation of alkynyl units to Pd(II) and in assisting reoxidation of Pd(0) to Pd(II) is suggested. 相似文献