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951.
Meyers C Maes BU Loones KT Bal G Lemière GL Dommisse RA 《The Journal of organic chemistry》2004,69(18):6010-6017
Evidence for an interphase deprotonation of Pd(II)-amine complexes with weak carbonate base has been gained for the first time. When a rate-limiting deprotonation step is involved in the catalytic cycle, controlling the structure (shape and size of the particles) and/or molar excess of the carbonate base used can significantly increase the reaction rate of Buchwald-Hartwig aminations. By taking such a "base effect" into account a general protocol for the intermolecular amination of aryl iodides with all types of amines has been developed based on a standard Pd-BINAP catalyst, using cesium carbonate as the base. 相似文献
952.
A.Guy Orpen 《Journal of organometallic chemistry》1978,159(2):c1-c4
A semi-empirical method of predicting the location of hydride ligands in metal carbonyl cluster compounds using X-ray structural information is described. The hydride positions thus derived are compared with those obtained from neutron diffraction experiments and predictions made for previously ambiguous cases. 相似文献
953.
Chotima R Dale T Green M Hey TW McMullin CL Nunns A Orpen AG Shishkov IV Wass DF Wingad RL 《Dalton transactions (Cambridge, England : 2003)》2011,40(19):5316-5323
Reaction of [Pd(PPh(3))(4)] with 1,1-dichloro-2,3-diarylcyclopropenes gives complexes of the type cis-[PdCl(2)(PPh(3))(C(3)(Ar)(2))] (Ar = Ph 5, Mes 6). Reaction of [Pd(dba)(2)] with 1,1-dichloro-2,3-diarylcyclopropenes in benzene gave the corresponding binuclear palladium complexes trans-[PdCl(2)(C(3)(Ar)(2))](2) (Ar = Ph 7, p-(OMe)C(6)H(4)8, p-(F)C(6)H(4)9). Alternatively, when the reactions were performed in acetonitrile, the complexes trans-[PdCl(2)(NCMe)(C(3)(Ar)(2))] (Ar = Ph 10, p-(OMe)C(6)H(4)11 and p-(F)C(6)H(4)) 12) were isolated. Addition of phosphine ligands to the binuclear palladium complex 7 or acetonitrile adducts 11 and 12 gave complexes of the type cis-[PdCl(2)(PR(3))(C(3)(Ar)(2))] (Ar = Ph, R = Cy 13, Ar = p-(OMe)C(6)H(4), R = Ph 14, Ar = p-(F)C(6)H(4), R = Ph 15). Crystal structures of complexes 6·3.25CHCl(3), 10, 11·H(2)O and 12-15 are reported. DFT calculations of complexes 10-12 indicate the barrier to rotation about the carbene-palladium bond is very low, suggesting limited double bond character in these species. Complexes 5-9 were tested for catalytic activity in C-C coupling (Mizoroki-Heck, Suzuki-Miyaura and, for the first time, Stille reactions) and C-N coupling (Buchwald-Hartwig amination) showing excellent conversion with moderate to high selectivity. 相似文献
954.
The Ramanujan Journal - Let $$f(z)=\sum _{n=0}^{\infty }a_{n}{\mathbf {e}}(nz),g(z)=\sum _{n=0}^{\infty }b_{n}{\mathbf {e}}(nz)\ ({\mathbf {e}}(z)=e^{2\pi \sqrt{-1}z})$$ be holomorphic modular... 相似文献
955.
Air‐Stable (CAAC)CuCl and (CAAC)CuBH4 Complexes as Catalysts for the Hydrolytic Dehydrogenation of BH3NH3 下载免费PDF全文
Dr. Xingbang Hu Dr. Michèle Soleilhavoup Dr. Mohand Melaimi Dr. Jiaxiang Chu Prof. Guy Bertrand 《Angewandte Chemie (International ed. in English)》2015,54(20):6008-6011
The first stable copper borohydride complex [(CAAC)CuBH4] [CAAC=cyclic(alkyl)(amino)carbene] bearing a single monodentate ligand was prepared by addition of NaBH4 or BH3NH3 to the corresponding [(CAAC)CuCl] complex. Both complexes are air‐stable and promote the catalytic hydrolytic dehydrogenation of ammonia borane. The amount of hydrogen released reaches 2.8 H2/BH3NH3 with a turnover frequency of 8400 mol molcat?1 h?1 at 25 °C. In a fifteen‐cycle experiment, the catalyst was reused without any loss of efficiency. 相似文献
956.
Quantitative determination of chloramphenicol in milk powders by isotope dilution liquid chromatography coupled to tandem mass spectrometry 总被引:5,自引:0,他引:5
Guy PA Royer D Mottier P Gremaud E Perisset A Stadler RH 《Journal of chromatography. A》2004,1054(1-2):365-371
A method is described for the determination of residues of the illegal antibiotic chloramphenicol (CAP) in milk powders. The analyte is quantified by liquid chromatography coupled to electrospray ionisation tandem mass spectrometry (LC-ESI-MS-MS) operating in negative ion multiple reaction monitoring mode (MRM) after a liquid-liquid extraction followed by a clean-up step on solid phase extraction (SPE) cartridge. Because of the presence of two chlorine atoms in the CAP molecule, four specific transition reactions of CAP were monitored by MS-MS in selecting m/z 321 --> 257, 321 --> 152 (35Cl2) and m/z 323 --> 257, 323 --> 152 (37Cl35Cl). Two calibration curves were constructed by plotting the area ratio of m/z 321 --> 152 versus 326 --> 157 and m/z 321 --> 257 versus 326 --> 262 against their corresponding amount ratio. Indeed, even if m/z 321 --> 152 was found to give a higher MS-MS response (calibration curve used by default), an interfering chemical substance was sometimes observed for some milk extracts and not for the transition m/z 321 --> 257. The quantitation method was validated according to the European Union (EU) criteria for the analysis of veterinary drug residues at 0.1, 0.2 and 0.5 microg/kg concentration levels using d5-CAP as internal standard. The decision limit (CCalpha) and detection capability (CCbeta) of CAP in milk were calculated for m/z 321 --> 152 at 0.02 microg/kg and 0.03 microg/kg, respectively, and for m/z 321 --> 257 at 0.02 microg/kg and 0.04 microg/kg, respectively. At the lowest fortification level (i.e. 0.1 microg/kg), repeatability and within-laboratory reproducibility were calculated for m/z 321 --> 257 both at 0.02 microg/kg and for m/z 321 --> 152 at 0.03 and 0.05 microg/kg, respectively. Moreover, the measurement of uncertainty of the analytical method was calculated at the same spiking levels and falls within the precision values of the within-laboratory reproducibility. This method can be applied to several types of milk powders (e.g. full cream, skim) and can serve as a monitoring tool to avoid that unacceptable levels of residues of CAP enter the food chain. 相似文献
957.
Kinetics of Lifetime Changes in Bimetallic Nanocatalysts Revealed by Quick X‐ray Absorption Spectroscopy 下载免费PDF全文
Dr. Matthias Filez Dr. Hilde Poelman Dr. Evgeniy A. Redekop Dr. Vladimir V. Galvita Dr. Konstantinos Alexopoulos Dr. Maria Meledina Dr. Ranjith K. Ramachandran Dr. Jolien Dendooven Prof. Christophe Detavernier Prof. Gustaaf Van Tendeloo Dr. Olga V. Safonova Dr. Maarten Nachtegaal Prof. Bert M. Weckhuysen Prof. Guy B. Marin 《Angewandte Chemie (International ed. in English)》2018,57(38):12430-12434
958.
Guy Roos 《中国科学A辑(英文版)》2005,48(1):225-237
We introduce the notion of virtual Bergman kernel and study some of its applications. 相似文献
959.
Guy Mayer 《Optics Communications》1977,20(2):200-204
Stimulated scattering by free electrons is first studied within a quantum model due to Schroedinger and subsequently within a classical “hydrodynamical” picture. In the latter case, it can be shown that a method initially introduced by Landau to study the damping of electronic vibrations in plasmas is well suited to this problem and provides a precise analysis of the experimental results recently obtained by a Stanford group. 相似文献
960.
Lassen PR Guy L Karame I Roisnel T Vanthuyne N Roussel C Cao X Lombardi R Crassous J Freedman TB Nafie LA 《Inorganic chemistry》2006,45(25):10230-10239
The infrared and vibrational circular dichroism (VCD) spectra of six chiral oxorhenium(V) complexes, bearing a hydrotris(1-pyrazolyl)borate (Tp) ligand, have been investigated. These complexes are promising candidates for observation of parity violation (symmetry breaking due to the weak nuclear force). New chiral oxorhenium complexes have been synthesized, namely, [TpReO(eta2-O(CH3)CH2CH2O-O,O)] (4a and 4b) diastereomers and [TpReO(eta2-N(CH3)CH2CH2O-N,O)] (5) and [TpReO(eta2-N(tBu)CH2CH2O-N,O)] (6) enantiomers. All compounds could be obtained in enantiomerically pure form by using either column chromatography or HPLC over chiral columns. VCD spectroscopy of these compounds and of [TpReO(eta2-N(CH3)CH(CH3)CH(Ph)O-N,O)] (2) and [TpReO(eta2-N(CH2)3CHCO2-N,O)] (3) (with chiral bidentate ligands derived, respectively, from ephedrine and proline) were studied. This allowed the absolute configuration determination of all compounds together with their conformational analysis, by comparing calculated and experimental spectra. This is the first VCD study of rhenium complexes which further demonstrates the applicability of VCD spectroscopy in determining the chirality of inorganic complexes. 相似文献