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991.
Frommberger M Hertkorn N Englmann M Jakoby S Hartmann A Kettrup A Schmitt-Kopplin P 《Electrophoresis》2005,26(7-8):1523-1532
A quantitative, specific, and sensitive method for the determination of N-acylhomoserine lactones (HSLs - a group of bacterial semiochemicals) in the form of their hydrolysis products (N-acylhomoserines, HSs) is presented. Real samples were analyzed by capillary zone electrophoresis-mass spectrometry (CZE-MS) after alkaline lactonolysis and extraction by mixed-mode anion-exchange solid-phase extraction. The presented cleanup significantly speeds up the HSL extraction procedure, strongly reduces sample consumption, and is more selective compared to the commonly used liquid/liquid extraction. Completeness of the hydrolysis reaction was examined by nuclear magnetic resonance spectroscopy. This CZE-MS method complements recently published capillary separation techniques (nano liquid chromatography-MS, partial-filling micellar electrokinetic chromatography-MS, gas chromatography-MS) and provides a possibility to differentiate quantitatively between the homoserines (as naturally occurring degradation products) besides the intact homoserine lactones. The method was found to be quantitative down to a concentration of 0.05 microg/mL (limit of quantification), while the limit of detection was determined with 0.01 microg/mL - sufficient for the analysis of culture supernatants. 相似文献
992.
Margarita Surez Esperanza Salfrn Estael Ochoa Yamila Verdecia Livan Alba Nazario Martín Carlos Seoane Roberto Martínez‐Alvarez Hector Novoa De Armas Norbert M. Blaton Oswald M. Peeters Camiel J. De Ranter 《Journal of heterocyclic chemistry》2003,40(2):269-275
Two dihydropyridines endowed with fluorine atoms ( 3 ) and fluorine and chlorine atoms ( 4 ) have been synthesized and structurally characterized by experimental X‐ray analyses and theoretical calculations at the semiempirical (AMI) and ab initio (HF/6–31G*) levels. The results show that these compounds meet the required criteria to act as potential calcium channel modulators. 相似文献
993.
Gourianova S Willenbacher N Kutschera M 《Langmuir : the ACS journal of surfaces and colloids》2005,21(12):5429-5438
The adhesive properties of untreated and corona treated polypropylene (PP) films were studied in polar (water) and nonpolar (hexadecane) liquid medium by using chemical force microscopy. A gold-coated colloidal probe was sequentially modified with self-assembled monolayers (SAMs) of omega-functionalized alkanethiols. The same colloidal probe was used for the force measurements, to avoid influence of determination accuracy of the spring constant and sphere radius on the obtained results. The thermodynamic work of adhesion was determined from the measured pull-off force using the Johnson-Kendall-Roberts (JKR) adhesion theory. Rabinovich's model was applied for the consideration of an effect of roughness when calculating the work of adhesion. It was found that the work of adhesion correlates with the hydrophilic properties of the PP surface and SAMs as well as with the polarity of the liquid medium. The observed correlations agree well with those found for the work of adhesion calculated from contact angle measurement. 相似文献
994.
Lutz Rösch Gerald Altnau Wolfgang Erb Joachim Pickardt Norbert Bruncks 《Journal of organometallic chemistry》1980,197(1):51-57
Dicyclopentadienyl(trimethylsilyl)titanium chloride, a stable trimethylsilyltitanium compound, is synthesized by reaction of dicyclopentadienyltitanium dichloride and tris(trimethylsilyl)aluminium, coordinated with diethyl ether, or lithium tetarakis(trimethylsilyl)aluminate. The IR and NMR spectra are reported. The crystal structure of the title compound has been determined. It shows a distorted tetrahedral surrounding of the titanium atom; the Ti–Si distance is 267 pm. 相似文献
995.
Christoph D. Hahn Ali Tinazli Martin Hölzl Christa Leitner Filip Frederix Bernd Lackner Norbert Müller Christian Klampfl Robert Tampé Hermann J. Gruber 《Monatshefte für Chemie / Chemical Monthly》2007,138(3):245-252
Summary. The present study describes new synthetic routes to oligo(ethylene glycol)-terminated alkanethiols (OEG-ATs), starting from α,ω-dibromoalkanes, which are reacted either with OEG or with trityl mercaptan in the first step. In addition to these ether conjugates of OEG and AT, analogous ester and amide conjugates were prepared by established procedures. All thiols were used to form self-assembled
monolayers (SAMs) on cleaned gold surfaces and these were stored for 1–2 weeks under water at 4°C before the extent of nonspecific protein
adsorption was tested with IgG, BSA, and lysozyme at 1 mg cm−3 protein concentration in phosphate-buffered saline. Under these practice-oriented testing conditions, SAMs with tri(ethylene glycol) chains (EG
3) exhibited nonsatisfactory protein resistance, in sharp contrast to EG
4 or longer OEG chains. The effectiveness of EG
3 was partially restored when they were linked to a long acyl chain (16-mercaptohexadecanoic acid) instead of 12-mercaptododecane
or 11-mercaptoundecane. Furthermore it was found that (i) SAM formation at 20 μM thiol versus 500 μM
OEG-AT gave identical results, (ii) gel-filtered proteins were much less adsorbed than the unpurified commercial products, and (iii)
the method for gold-precleaning was very critical. In conclusion, this study offers convenient synthetic routes to OEG-AT and helps to choose molecules and procedures for reliable preparation of protein-resitant SAMs with prolonged stability during storage. 相似文献
996.
The synthesis of new flavone-3-sulfonylurea derivatives is hereby described. The influence of a phenyl group in the 2-position and an acetate group in the 8-position at the chromone nucleus on the activity was studied. Only weak cytostatic activity of the new compounds was found. 相似文献
997.
Summary 1,19-Bilindiones bearing a phenanthryl, mesityl,tert-butyl, and isopropyl substituent at the C-10 position were synthesized. Conformational analysis using13C- and1H-NMR spectroscopic techniques and absorption spectroscopy together with semiempirical calculations revealed that the aryl derivatives adopt the common circular helical geometry, whereas thetert-butyl derivative is heavily distorted. The mean planes of the two dipyrrinone moieties are orthogonally positioned to each other. The 10-isopropyl-bilindione tautomerizes to the 10-isopropyliden-biladiene-ac. 相似文献
998.
Tetrameric [{RZn(NHNMe2)}4] (R = Me, Et), the first organometallic zinc hydrazides to be described, have been prepared by alkane elimination from dialkylzinc solutions and N,N-dimethylhydrazine. They were characterised by 1H and 13C NMR and IR spectroscopy, mass spectrometry, elemental analysis and X-ray crystallography. The compounds form asymmetric aggregates containing the novel Zn4N8 core; tetrahedra of Zn atoms bear the alkyl groups at Zn, with the triangular faces bridged by NHNMe2 substituents. The NH groups are connected to two Zn atoms, and the NMe2 groups to one. Hydrolysis of the compounds with water gives [(RZn)4(OH)(NHNMe2)3] as products, which also were characterised as described above. Higher yields of these hydroxo clusters were achieved in one-pot syntheses by reaction of dialkylzinc solutions with mixtures of N,N-dimethylhydrazine and water. They contain Zn4N6O cages, in which one hydroxide in the tetrameric hydrazides described above replaces one NHNMe2 group. Similar products can be prepared with alkoxy instead of hydroxy groups, in analogous one-pot syntheses with alcohols. Alcoholysis of [EtZn(NHNMe2)]4 with methanol or ethanol gave zinc trishydrazide monoalkoxides, [(EtZn)4(OR)(NHNMe2)3] (R = Me, Et), which have constitutions analogous to the monohydroxides. The organozinc bishydrazide bisalkoxides [(MeZn)4(NHNMe2)2(OEt)2] and [(EtZn)4(NHNMe2)2(OEt)2] were obtained in one-pot reactions from dialkylzinc solutions with mixtures of the hydrazine and alcohol, and their crystal structures, confirmed by spectroscopic methods in solution, show an unsymmetrical aggregation with the novel Zn4N4O2 cage structure. 相似文献
999.
Using a force field previously described, the energy hypersurface around the global energy minimum of the (Z,Z,Z)-Octamethylbilatriene-abc1 was investigated with respect to the torsion angles at positions 5, 9 and 14 yielding informations on the geometry of the global minimum and the transition paths between enantiomeric conformers. The geometry of the most stable conformations were calculated for the diastereomers of1 as well as for the peripherally unsubstituted3 and the N-methylated derivatives4, 5 and6. The conformational behaviour and the relative stabilities of the diastereomers turned out to be dominated by the influence of the peripheral substitution (alkylgroup backbone). The results are in good agreement with earlier experimental results.
40. Mitt.:Falk, H., Schlederer, T., Mh. Chem.112, 501 (1981). 相似文献
1000.
Heinz Falk Karl Grubmayr Gerhard Kapl Norbert Müller Ulrich Zrunek 《Monatshefte für Chemie / Chemical Monthly》1983,114(6-7):753-771
2,3-Dihydrobilatrienes-abc substituted analogous to the natural chromophor of phytochrome may exhibit diastereomerism at the exocyclic double bond of the unsaturated lactam ring. Their properties are comparable to the previouslystudied bilatriene-abc diastereomers. At the exocyclic double bond of the saturated lactam ring however, diastereomers could only be prepared for thermodynamic reasons. The spectroscopic properties of the various diastereomers of five compounds were recorded and are discussed with respect to their utility in structural studies of the natural pigment system. 相似文献