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51.
Summary Transmembrane linear terminal complexes considered to be involved in the synthesis of cellulose microfibrils have been described in the plasma membrane ofBoergesenia forbesii. Evidence for the existence of these structures has been obtained almost exlusively using the freeze etching technique. In the present study an attempt has been made to complete these studies using conventional fixation, staining, and sectioning procedures. In developing cells ofBoergesenia forbesii, strongly stained structures traversing the plasma membrane and averaging 598.9 nm ± 171.3 nm in length, 28.7 nm ± 4.2 nm in width, and 35.2 nm ± 6.6 nm in depth have been demonstrated. These structures are considered to be linear terminal complexes. At their distal (cell wall) surface, they appear to be closely associated with cellulose microfibrils. At the proximal (cytoplasmic) surface, they are associated with microtubules and polysomes. A model of the possible interrelation of the terminal complexes and microtubules leading to the generation of cell wall microfibrils is proposed. 相似文献
52.
Bongiorno D Ceraulo L Mele A Panzeri W Selva A Turco Liveri V 《Carbohydrate research》2002,337(8):743-754
The stoichiometry, geometry, stability, and solubility of the inclusion complexes of melatonin (MLT) with native cyclomaltooligosaccharides (alpha-, beta- or gamma-cyclodextrins, CDs) are determined experimentally by high-resolution NMR spectroscopy, calorimetric and solubility measurements, and mass spectrometry. The observed differences are discussed in terms of molecular recognition expression of the host-guest (h-g) interactions within the hydrophobic CDs cavities of different size. The 1:1 h-g stoichiometry in water solution prevails at low CD concentrations; the trend to form higher order associations is observed at increasing CD concentrations. The stability order beta-CD>gamma-CD>alpha-CD for the complexes in water solution and beta-CD>alpha-CD>gamma-CD for the protonated or alkali-cationated complexes in the gas phase are rationalized on the grounds of the structural data from NMR spectroscopy and of the thermodynamic parameters from calorimetric measurements. 相似文献
53.
The complex [Ru(SB12H11)(NH3)5]·2H2O has been prepared by the reaction of Cs2B12H11SH with [RuCl(NH3)5]Cl2 in aqueous solution. The complex represents the first reported example of the borocaptate anion acting as a ligand. The structure of the complex has been determined by single crystal X-ray diffraction analysis. The crystal parameters are monoclinic, space group P21/c, A = 8.056(1), B = 14.240(2), C = 15.172(2) Å, β=98.48° and Z = 4. The ruthenium atom has a distorted octahedral coordination. The distortion is probably due to the high (3−) charge and the large bulk of the borocaptate ligand. These features can also be observed in the spectroscopic properties of the complex. 相似文献
54.
D. P. Singh Ramesh Kumar Jitender Singh 《Journal of enzyme inhibition and medicinal chemistry》2013,28(3):883-889
A new series of complexes is synthesized by template condensation of oxalyldihydrazide and glyoxal in methanolic medium in the presence of trivalent chromium, manganese and iron salts forming complexes of the type: [M(C8H8N8O4)X]X2 where M = Cr(III), Mn(III), Fe(III) and X = Cl? 1, , CH3COO? 1. The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic susceptibility measurements, electronic, NMR, infrared and far infrared spectral studies. On the basis of these studies, a five coordinate square pyramidal geometry for these complexes has been proposed. The biological activities of the metal complexes were tested in vitro against a number of pathogenic bacteria and some of the complexes exhibited remarkable antibacterial activities. 相似文献
55.
Roman Bo?a Peter Baran L'ubor Dlháň Hartmut Fuess Wolfgang Haase Franz Renz Wolfgang Linert Ingrid Svoboda Rüdiger Werner 《Inorganica chimica acta》1997,260(2):4119-136
The structure of the [Fe(bzimpy)2](ClO4)2·xH2O system (x = 0.25) was determined by single crystal X-ray structure analysis. The Fe(II) ion is hexacoordinated by six donor nitrogen atoms. The magnetic properties of the complex were investigated by powder magnetic susceptibility measurements and ESR. The freshly prepared sample does not show any traces of iron(III) impurities but these are formed as a function of time. After 1 year the sample contains 8.2% iron(III) as shown by UV spectroscopy and indicated by geff = 4.3 and 2.0 in its ESR spectrum. This explains the recorded ξ versus T behaviour at low temperature: with increasing temperature the ξ value decreases according to the Curie-Weiss law for a S = 5/2 system having an effective g = 4.3. Above 220 K a continuous increase in the ξ value is observed and a spin crossover applies. The spin transition is not complete at room temperature. A pronounced hysteresis is observed upon heating/cooling the sample between 220 and 414 K on the basis of magnetic data and infrared spectra. 相似文献
56.
57.
Sotiris Zartilas Nick Hadjiliadis Nikolaos Kourkoumelis Maciej Kubicki Ian S. Butler Jan Balzarini 《Inorganica chimica acta》2009,362(3):1003-121
Silver(I) halides react with tri(p-tolyl)phosphine (tptp, C21H21P) in MeOH/MeCN solutions in 1:1 or 1:3 molar ratios to give complexes of formulae {[AgCl(tptp)]4} (1) or [AgX(tptp)3] (X = Cl (2), Br (3), I (4)), respectively. The complexes were characterized by elemental analyses, and FT-IR far-IR, FT-Raman, TG and 1H, 13C, 31P NMR spectroscopic techniques. Crystal structures of complexes 2-4 were determined by X-ray diffraction at room temperature (rt). The crystal structure of 1 and 4 was also determined at 100(1) and 140(2) K (lt), respectively. In complex 1 four μ3-Cl ions are bonded with four Ag(I) ions forming a cubane while the coordination sphere of silver(I) ions is completed by one P atom from a terminal tri(p-tolyl)phosphine ligand. In complexes 2-3 one terminal halogen and three P atoms from phosphine ligands form a tetrahedral arrangement around the metal ion. Complexes 1-4 were tested for in vitro cytostatic activity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, polycyclic aromatic hydrocarbons (PAH, benzo[a]pyrene) carcinogenesis and against murine leukemia (L1210) and human T-lymphocyte (Molt4/C8 and CEM) cells. The silver(I) complexes 1-4 show strong activity. 相似文献
58.
Daniel J. Saltzberg Shruthi Viswanath Ignacia Echeverria Ilan E. Chemmama Ben Webb Andrej Sali 《Protein science : a publication of the Protein Society》2021,30(1):250-261
Biology is advanced by producing structural models of biological systems, such as protein complexes. Some systems are recalcitrant to traditional structure determination methods. In such cases, it may still be possible to produce useful models by integrative structure determination that depends on simultaneous use of multiple types of data. An ensemble of models that are sufficiently consistent with the data is produced by a structural sampling method guided by a data‐dependent scoring function. The variation in the ensemble of models quantified the uncertainty of the structure, generally resulting from the uncertainty in the input information and actual structural heterogeneity in the samples used to produce the data. Here, we describe how to generate, assess, and interpret ensembles of integrative structural models using our open source Integrative Modeling Platform program ( https://integrativemodeling.org ). 相似文献
59.
Bis‐ and Tetrakis(carboxylato)platinum(IV) Complexes with Mixed Axial Ligands – Synthesis,Characterization, and Cytotoxicity 下载免费PDF全文
Björn R. Hoffmeister Michaela Hejl Mahsa S. Adib‐Razavi Michael A. Jakupec Markus Galanski Bernhard K. Keppler 《化学与生物多样性》2015,12(4):559-574
A series of twelve novel diamminetetrakis(carboxylato)platinum(IV) and 18 novel bis(carboxylato)dichlorido(ethane‐1,2‐diamine)platinum(IV) complexes with mixed axial carboxylato ligands was synthesized and characterized by multinuclear 1H‐, 13C‐, 15N‐, and 195Pt‐NMR spectroscopy. Their cytotoxic potential was evaluated (by MTT assay) against three human cancer cell lines derived from ovarian teratocarcinoma (CH1/PA‐1), lung (A549), and colon carcinoma (SW480). In the cisplatin‐sensitive CH1/PA‐1 cancer cell line, diamminetetrakis(carboxylato)platinum(IV) complexes showed IC50 values in the low micromolar range, whereas, for the most lipophilic compounds of the bis(carboxylato)dichlorido(ethane‐1,2‐diamine)platinum(IV) series, IC50 values in the nanomolar range were found. 相似文献
60.
The 2-methallyl complex [(η5-C9H7)Ru(η3-2-MeC3H4)(PPh3)] (3), prepared from [(η5-C9H7)Ru(PPh3)2Cl] (2) and 2-MeC3H4MgCl, reacts with HX (X = Cl, CF3CO2) in the presence of ethene to give the chiral-at-metal compounds [(η5-C9H7)Ru(C2H4)(PPh3)X] (4, 5) in nearly quantitative yields. Treatment of 2 with AgPF6 and ethene affords [(η5-C9H7)Ru(C2H4)(PPh3)2]PF6 (6), which reacts with acetone to give the substitution product [(η5-C9H7)Ru(OCMe2)(PPh3)2]PF6 (7). The molecular structure of 7 has been determined crystallographically. Whereas treatment of 4 with CH(CO2Et)N2 yields the olefin complex [(η5-C9H7)Ru{η2-(Z)-C2H2(CO2Et)2}(PPh3)Cl] (8), the reactions of 4 and 5 with Ph2CN2, PhCHN2 and (Me3Si)CHN2 lead to the formation of the carbeneruthenium(II) derivatives [(η5-C9H7)Ru(CRR′)(PPh3)Cl] (9-11) and [(η5-C9H7)Ru(CRR′)(PPh3)(κ1-O2CCF3)] (12-14), respectively. Treatment of 9 (R = R′ = Ph), 10 (R = H, R′ = Ph) and 11 (R = H, R′ = SiMe3) with MeLi produces the hydrido(olefin) complexes [(η5-C9H7)RuH(η2-CH2CPh2)(PPh3)] (15), [(η5-C9H7)RuH(η2-CH2CHPh)(PPh3)] (18a,b) and [(η5-C9H7)RuH(η2-CH2CHSiMe3)(PPh3)] (19) via C-C coupling and β-hydride shift. The analogous reactions of 11 with PhLi gives the η3-benzyl compound [(η5-C9H7)Ru{η3-(Me3Si)CHC6H5}(PPh3)] (20). The η3-allyl complex [(η5-C9H7)Ru(η3-1-PhC3H4)(PPh3)] (17) was prepared from 10 and CH2CHMgBr by nucleophilic attack. 相似文献