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31.
Elisa Brivio Alessandro Ceriotti Roberto Della Pergola Luigi Garlaschelli Mario Manassero Mirella Sansoni 《Journal of Cluster Science》1995,6(2):271-287
Redox condensation of [Ru3H(CO)11]- with Ni(CO)4, in tetrahydrofuran solution, under a nitrogen atmosphere, yields the tetranuclear anion [NiRuH(CO)11)-. Subsequent deprotonation with Bu'OK in acetonitrile solution leads to the formation of the related dianion. Both anions have been characterized by spectroscopic techniques, elemental analysis and single crystal X-ray diffraction. [PPh4][NiRu3H(CO)12] crystallizes in the triclinic space group PI with unit cell dimensionsof a = 11.842(2) Å,b = 12.335(3) Å, c = 13.3080) Å,a = 91.89(2)°, = 93.35(1)°,y = 96.41(2)°, Z = 2, V= 1926.9(7) Å'. The NiRu3, metal core of the molecule defines a distorted tetrahedron with nine terminal and three edge bridging carbonyl groups. The hydrido ligand was located by difference Fourier techniques and was found to bridge the NiRu2 basal triangle at a distance of 0.88(6) A from this plane. Selected average distances and angles are: Ru-Ru = 2.839 Å, Ru-Ni = 2.640 Å, Ru-C, = 1.910 A,Ru-C
b
= 2.084 Å, Ni-C
b
= 2.022 Å, Ru-H = 1.77 Å, C-0, = 1.135 Å, C-O
b
= 1.159 Å, M-C-O, = 176.3°,M-C--O
b
= 139.3°;other distances are: Ni-C1 = l.758(7) Å, Ni-H= 1.85(7) Å. [NEt4]2[NiRu3(CO)12] crystallizes in the orthorhombic space group Pnma (no. 62) with unit cell dimensions ofa=20.247(5) Å,b = 15.038(4)Å,c = 12.079(3) Å, Z=4, V=3678(2) A'. The molecule contains a tetrahedral NiRu3 core with eight terminal and four edge bridging carbon monoxide groups which bridge the three Ni-Ru and one Ru-Ru bond. Average distances and angles are: Ru -Ru =2.3050A Ru-Ni 2.648 Å, Ru-C
t
= 1.878 Å, Ru-C
b
2.045 Å, Ni-C
b
= 2.055 Å, C-O
t
= 1.145 Å, C-01,=1.157 Å, M-C-O,= 176.9°, M-C-O
b
= 138.6°; other distance is: Ni-C
t
= 1.754(10) Å,t = terminal,b = bridging. 相似文献
32.
5-Alkynylpyridazin-3(2H)-ones or 5-(2-chloroalkenyl)pyridazin-3(2H)-ones were isolated during the cleavage of the methoxymethyl group in a series of 5-alkynyl-2-methoxymethylpyridazin-3(2H)-ones by treatment with hydrochloric acid. The efficient and selective cleavage of the methoxymethyl group in these compounds can be performed under mild conditions by employing aluminium chloride. 相似文献
33.
Optical sensors based on hybrid DNA/conjugated polymer complexes 总被引:2,自引:0,他引:2
Ho HA Béra-Abérem M Leclerc M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(6):1718-1724
Single-stranded DNA (ss-DNA) can specifically bind to various targets, including a complementary ss-DNA, ions, proteins, drugs, and so forth. When binding takes place, the oligonucleotide probe often undergoes a conformational transition. This conformational change of the negatively charged ss-DNA can be detected by using a water-soluble, cationic polythiophene derivative, which transduces the complex formation into an optical (colorimetric or fluorometric) signal without any labeling of the probe or the target. This simple and rapid methodology has enabled the specific and sensitive detection of nucleic acids and human thrombin. This new biophotonic tool can easily be applied to the detection of various other biomolecules and is also useful in the high-throughput screening of new drugs. 相似文献
34.
Koushik Dhara Santanu Karan Jagnyeswar Ratha Partha Roy Goutam Chandra Mario Manassero Dr. Biswanath Mallik Dr. Pradyot Banerjee Dr. 《化学:亚洲杂志》2007,2(9):1091-1100
A 2D coordination compound {[Cu2(HL)(N3)]?ClO4}∞ ( 1 ; H3L=2,6‐bis(hydroxyethyliminoethyl)‐4‐methyl phenol) was synthesized and characterized by single‐crystal X‐ray diffraction to be a polymer in the crystalline state. Each [Cu2(HL)(N3)]+ species is connected to its adjacent unit by a bridging alkoxide oxygen atom of the ligand to form a helical propagation along the crystallographic a axis. The adjacent helical frameworks are connected by a ligand alcoholic oxygen atom along the crystallographic b axis to produce pleated 2D sheets. In solution, 1 dissociates into [Cu2(HL)2(H3L)]?2H2O ( 2 ); the monomer displays high selectivity for Zn2+ and can be used in HEPES buffer (pH 7.4) as a zinc ion selective luminescent probe for biological application. The system shows a nearly 19‐fold Zn2+‐selective chelation‐enhanced fluorescence response in the working buffer. Application of 2 to cultured living cells (B16F10 mouse melanoma and A375 human melanoma) and rat hippocampal slices was also studied by fluorescence microscopy. 相似文献
35.
The new hexaalkylborazine chromium tricarbonyls (n-Pr)3B3N3Me3Cr(CO)3 (V), Me3B3N3(n-Pr)3Cr(CO)3 (VI), (i-Pr)3B3N3Me3Cr(CO)3 (VII) and Me3B3N3(i-Pr)3Cr(CO)3 (VIII) have been prepared from fac-Cr(CO)3(MeCN)3 and the corresponding borazine in dioxane or without solvent. They are much more labile than the isomeric complex Et3B3N3Et3Cr(CO)3 (IV) which can be readily obtained from Et3B3N3Me3Cr(CO)3 and Et3B3N3Et3 by ring ligand exchange. The NMR., IR., UV. and Mass spectroscopic data of the complexes IV–VIII will be briefly discussed. The preparation of the borazine derivatives (n-Pr)3B3N3Me3 (IX) and Me3B3N3(n-Pr)3 (X) is also reported. 相似文献
36.
Mario Bianchi Ugo Matteoli Piero Frediani Gloria Menchi Franco Piacenti 《Journal of organometallic chemistry》1982,236(3):375-380
Hydrogen transfer from racemic alcohols to prochiral ketones in the presence of H4Ru4(CO)8[(?)-DIOP]2 has been examined. The enantiomer-discrimination is influenced by the structure of the reactants, temperature and the excess of phosphine present. 相似文献
37.
The first total synthesis of (±)-cyclooroidin, a member of the pyrrole-imidazole alkaloid family recently isolated from the sponge Agelas oroides in optically pure form, is described. The synthesis was achieved in nine linear steps, with an overall yield of 10%. Key step was a Wolff bromoketone synthesis performed on the intermediate longamide B. 相似文献
38.
Chiesa M Paganini MC Spoto G Giamello E Di Valentin C Del Vitto A Pacchioni G 《The journal of physical chemistry. B》2005,109(15):7314-7322
Paramagnetic centers at the surface of ionic oxides in the form of trapped electrons can be generated by exposure of the material to alkali metal or hydrogen atoms or of molecular hydrogen under UV irradiation. For many years, it has been assumed that the resulting paramagnetic centers consist of oxygen vacancies filled by one electron. High-resolution electron spin resonance spectra and ab initio quantum chemical calculations show that the paramagnetic centers consist of (H(+))(e(-)) electron pairs formed at morphological irregularities of the surface. At least three different kinds of (H(+))(e(-)) centers, [A], [B], and [C], have been identified with abundances of 80%, 10%, and 8%, respectively. In this work, we compare a wide set of measured and computed g-factors and hyperfine coupling constants of the unpaired electron with the surrounding (25)Mg, (17)O, and (1)H nuclei and we propose a general assignment of the centers. (H(+))(e(-)) pairs formed at Mg(4c) ions at steps and edges account for species [A], centers formed at Mg(4c) ions at reverse corners correspond to species [B], and species [C] originates from (H(+))(e(-)) pairs formed at Mg(3c) ions at corners and kinks. 相似文献
39.
Mario Giuffrida Pietro Maravigna Giorgio Montaudo Emo Chiellini 《Journal of polymer science. Part A, Polymer chemistry》1986,24(7):1643-1656
Some bipolyesters consisting of 1,2-propene glycol residue (P) and symmetric aromatic diacid residue constituted by two p-oxybenzoyl groups coupled by a terephthaloyl (HTH), phthaloyl (HOH) and isophthaloyl (HIH) group, and a nonsymmetric diacid residue constituted by a p-oxybenzoyl and a terephthaloyl group (HT), have been investigated by direct pyrolysis–mass spectrometry. The results show that intramolecular exchange reactions occurring at the pyrolysis stage cause a reorganization of the copolymer sequences. Sequential bipolyesters I–IV are ideal materials for the investigation of the extent of thermal reorganization induced in the bipolymer sequences by the pyrolytic process. 相似文献
40.
The kinetic behavior of cinnamic acids, their methyl esters, and two catechols 1-10 (ArOH) in the reaction with DPPH(*) in methanol and ethanol is not compatible with a reaction mechanism that involves hydrogen atom abstraction from the hydroxyl group of 1-10 by DPPH(*). The rate of this reaction at 25 degrees C is, in fact, comparatively fast despite that the phenolic OH group of ArOH is hydrogen bonded to solvent molecules. The observed rate constants (k(1)) relative to DPPH(*) + ArOH are 3-5 times larger for the methyl esters than for the corresponding free acids and, for the latter, decrease as their concentration is increased according to the relation k(1) = B/[ArOH](0)(m), where k(1) is given in units of M(-1) s(-1), m is ca. 0.5, and B ranges from 0.02 (p-coumaric acid) to ca. 3.48 (caffeic acid) in methanol and from 0.04 (p-coumaric acid) to ca. 13 (sinapic acid) in ethanol. Apparently, the reaction mechanism of DPPH(*) + ArOH involves a fast electron-transfer process from the phenoxide anion of 1-10 to DPPH(*). Kinetic analysis of the reaction sequence for the free acids leads to an expression for the observed rate constant, k(1), proportional to [ArOH](0)(-1/2) in excellent agreement with the experimental behavior of these phenols. The experimental results are also interpreted in terms of the influence that adventitious acids or bases present in the solvent may have. These impurities dramatically influence the ionization equilibrium of phenols and cause a reduction or an enhancement, respectively, of the measured rate constants. 相似文献