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121.
Wolfgang A. Herrmann Martina Flöel Cornelia Weber John L. Hubbard Adolf Schäfer 《Journal of organometallic chemistry》1985,286(3):369-397
The eighteen new μ-alkylidene ruthenium complexes 5a–r and 5t are very easily and cleanly obtained along the diazoalkane or the hydrazone routes that involve treatment of the dinuclear, metal-metal doubly bonded precursor compound [(η5-C5H5)Ru(μ-NO)]2 (3) either with the diazoalkanes oxidizing agent (e.g., MnO2), with the respective hydrazones. Similarly, sulfur dioxide adds cleanly to the RuRu double bond of 3, thus giving the complex (μ-SO2)[(η5-C5H5)Ru(NO)]2 (5s). Regardless of the nature of the carbene bridge ligands, the dimetallacyclopropanes exhibit, in contrast to their iron analogues, exclusively terminal nitrosyl ligands. cis/trans-Isomerism with predominating amounts of the trans-isomers is observed for the derivatives that display unsymmetrically substituted carbene bridges.Treatment of the μ-methylene- and μ-ethylidene complexes (μ-CH2)[(η5-C5H5)Ru(NO)]2 (5a) and (μ-CHCH3)[(η5-C tetrafluoroboric acid or trifluoromethanesulfonic acid in diethyl ether yields, at ambient temperature, quantitatively the ionic complexes 6a,b and 7a,b, respectively, which were shown by 1H NMR spectroscopy to contain metal-metal bridging hydrogen functionalities. The reaction of hydrogen bromide with 5a under the same conditions gives the neutral bromo(methyl) complex 6d. This latter compound results from the isolable ionic intermediate of composition [(μ-CH2)(μ-H){(η5C5H5)Ru(NO)}2]+Br? (6c), which reaction stems from the nucleophilicity of the halide ion present in 6c. 相似文献
122.
The dicobalt octacarbonyl catalyzed reaction of styrene oxide with trialkylsilanes yields a mixture of 1-phenyl-2-trialkylsiloxyethane and Z- and E-1-phenyl-2-trialkylsiloxyethene. The ratio of these products can be controlled. 相似文献
123.
Zusammenfassung Bei übersättigten Lösungen, die ihre Eigenschaften in ruhendem Zustande nur sehr langsam verändern, kann in der Strömungsapparatur durch die laminare Bewegung ein rasches Wachstum der gelösten Teilchen einsetzen, das durch die Messung der Strömungsdoppelbrechung fortlaufend verfolgbar ist. Nach dem Meßverfahren von Signer können der Auslöschwinkel und die Stärke der Doppelbrechung aus der Kompensationskurve, die eine Sinusschwingung vorstellt, abgelesen werden. Durch fortlaufende Registrierung dieser Kurve können Veränderungen des Auslöschwinkels, der Auskunft über das Längen-Breitenverhältnis der Teilchen gibt, und die Stärke der Doppelbrechung, die von der Teilchenorientierung und bei konstantem Längen-Breitenverhältnis außerdem von der Teilchendicke abhängt, nachgewiesen werden.Bei den untersuchten Lösungen von Karnaubawachs und Kongorot zeigen die geströmten Teilchen ein deutliches Wachstum, das nach den Beobachtungsdaten nicht zu stäbigen, sondern eher zu flächigen bis massigen Sekundärteilchen führt. 相似文献
124.
125.
Rydberg spectra are shown to provide a spectral fingerprint that is sensitive to molecular structure in unique ways. The concepts are demonstrated using a set of isomeric fluorophenols and a sequence of aliphatic diamines. In the fluorophenols, the sensitivity extends to the placement of a single hydrogen atom and can be traced to the molecular charge distributions associated with the locations of atoms and functional groups with respect to the charge center. Experiments on tetramethyl diamines demonstrate that the structural sensitivity encompasses the extended molecular structure, including parts of the molecule that are remote from the ionization center. This global structure sensitivity makes Rydberg fingerprint spectroscopy uniquely suited to characterize structures of large-scale molecular systems. 相似文献
126.
A D C, spectrochemical method using the STALLWOOD jet has been developed for the determination of Li, Na, K and Rb in silicate minerals and rocks. Samples are mixed with graphite and Cs2CO3 in tho ratio 2 : 1 : 1, and Cs serves as internal standard. Precision and accuracy is satisfactory. 相似文献
127.
Silvia Stumpf Gudrun Goretzki Kerstin Gloe Karsten Gloe Wilhelm Seichte Edwin Weber Jan W. Bats 《Journal of inclusion phenomena and macrocyclic chemistry》2003,45(3-4):225-233
The di- and tetra-allyl ethers of tert-butylcalix[4]arene 1 and 2 have been prepared by alkylation of tert-butylcalix[4]arene with allyl bromide and K2CO3 using different reaction times. Solution 1H NMR measurement of the di-allyl ether 1 and X-ray crystal structures of the complexes of 1 with chloroform (1a) or methanol (1b) indicate the cone conformation of 1 in which intramolecular hydrogen bonding can be maximized. The crystalline state conformers 1a and 1b are distorted in different grades depending on the solvent. While methanol is incorporated in the macrocycle, chloroform molecules do not occupy the cage. The solution 1H NMR spectra of tetra-allyl ether 2 show the co-existence of the cone and partial cone conformation. The partial cone conformer of 2 was investigated by X-ray crystallography. In this compound hydrogen bonding is not existent. The conformer distribution is likely affected by steric and template effects. 相似文献
128.
Magnetic field decoupling experiments in the optically excited states of NO2 yield decoupling signals with a width of 10 to 40 mG. We attribute these signals to the non-rigidity of the excited molecule. 相似文献
129.
130.
H. G. Weber 《Zeitschrift für Physik A Hadrons and Nuclei》1978,284(2):145-151
The polarization transfer between optically pumped alkali atoms and alkali molecules is studied, using the model introduced in a previous paper (Z. Physik A273, 9(1975)). It is shown that the atom-molecule-exchange reactionX+X 2→X 2+X is responsible for the nulear spin polarization observed in the alkali molecules, and that the recombination of the alkali atoms does not contribute to this polarization transfer. 相似文献