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121.
Chemical Constituents of Ailanthus triphysa 总被引:2,自引:0,他引:2
Two new compounds,8(14),15-isopimaradiene-2α,3α,19-triol(1),and 6α,7β-dihydroxy-17(20)-cis-5α-pregna-16-one(2),together with four known copounds,a oxygenated rare phyllocladane,phyllocladan-16α,19-diol(3),kaempferol-3-0-β-D-galactopyranosied,kaempferol-3-0-α-L-rhamnopyranoside and scopoletin, were isolated from the leaves of Ailanthus tripysa.Structures of 1-3 were elucidated on the basis of spectroscopic data as compared with related compounds. 相似文献
122.
The preparation and potentiometric pH response properties of membranes formulated with various aminated-poly(vinyl chloride) (PVC-NH2) products are described. Products containing secondary and/or primary amino functional groups are obtained by modifying PVC with mono- and/or diamines, respectively. Blank membranes prepared with either type of aminated-polymer exhibit nearly Nernstian potentiometric pH responses over different pH ranges. In general, membranes based on diamino products exhibit pH response over a wider range (5–10.5) than membranes formulated with monoamino products (<8.0). These potentiometric results are used to estimate the basicity of the various primary and secondary amino sites in the membrane phases.Dedicated to Professer W. Simon on the occasion of his 60th birthday 相似文献
123.
Tran QL Than MM Tezuka Y Banskota AH Kouda K Watanabe H Zhu S Komatsu K Thet MM Swe T Maruyama Y Kadota S 《Chemical & pharmaceutical bulletin》2003,51(6):679-682
Ginseng, the underground parts of plants of Panax species, has been used in oriental traditional medicine for centuries. Unfortunately, because of extensive exploitation over thousands of years, the natural source of these species has been almost exhausted. Recently, we have found a wild ginseng growing in Myanmar. Here, by a combination of chemical composition study and gene sequence analysis, we unambiguously demonstrate that the wild ginseng is actually P. zingiberensis, commonly known as ginger ginseng. This ginseng was an indigenous to the southwestern China. However, now it is seriously threatened to brink of extinction and is put on the highest level of protection in China. Therefore, an appropriate protection measure is highly recommended to preserve this valuable resource, since this Myanmar ginseng might turn out to be the last P. zingiberensis, which could ever be seen in the planet. 相似文献
124.
Kobayashi S Miyamura H Akiyama R Ishida T 《Journal of the American Chemical Society》2005,127(25):9251-9254
A novel, highly active immobilized ruthenium catalyst, which can be successfully used in oxidation of alcohols to aldehydes and ketones, has been developed. In contrast to most immobilized catalysts, the Ru catalyst has activity that is higher than that of the original non-immobilized catalyst. In a batch system, the Ru catalyst was recovered and reused several times without loss of activity. The catalyst was also applied to a flow system, in which excellent conversions and yields were demonstrated. No leaching of Ru was observed in both cases. 相似文献
125.
126.
Thorium atoms react with H2O2, H2 + O2 mixtures, and H2O in excess argon to form the Th(OH)2 and Th(OH)4 molecules as minor and major products, respectively. The vibrational frequencies observed in the matrix infrared spectra are in excellent agreement with MP2 computed values, which confirms the identification of these highly ionic thorium hydroxide molecules. Our MP2 calculations converge to slightly bent and tetrahedral structures, respectively. This investigation reports the first evidence for pure actinide dihydroxide and tetrahydroxide molecules. 相似文献
127.
Lee SS Douma M Koerner T Oleschuk RD 《Rapid communications in mass spectrometry : RCM》2005,19(18):2671-2680
A novel electrospray interface, which has distinct advantages over conventional pulled silica emitters, has been developed. This novel interface can be easily fabricated by forming a porous polymer monolith (PPM) at the end of a fused-silica capillary that facilitates a stable electrospray over a wide range of flow rates with only a modest increase in back-pressure. A comparison was made between the PPM-assisted electrospray and a commercial nanosprayer in terms of sensitivity, stability and robustness. A PPM-filled electrospray tip produced a day-to-day signal variation of 23% relative standard deviation (RSD) over a 3-day period when spraying a 1.0 microM test peptide solution. Furthermore, three different capillaries fabricated by the same process produced a signal variation of 17% RSD, indicating that the fabrication process shows good reproducibility. The multiple flow paths of the PPM function to split the flow and reduce clogging. Even following the accumulation of debris after prolonged use, a stable spray could still be generated with the PPM-filled capillary while the commercial nanosprayer ceased to function properly. In terms of sensitivity, PPM-assisted electrospray showed an enhancement in sensitivity at infusion flow rates between 100 to 1000 nL/min while commercial nanosprayers performed slightly better at flow rates below 100 nL/min. A sample purification step can be combined with the PPM-assisted sprayer, using the PPM as a stationary phase to desalt and preconcentrate samples prior to mass spectrometric detection. 相似文献
128.
129.
[reaction: see text] Modulation of the fluorescein fluorescence in the presence of spiropyran and ferric ion by light was observed. Such fluorescence modulation was due to the low oxidation potential of complex MC.Fe(2+), which made the electron transfer from MC.Fe(2+) to Flu(+)()(*)() thermodynamically favorable. As a result, the communication between two molecular switches based on fluorescein and spiropyan, respectively, was realized via the reversible Fe(III)/Fe(II) redox couple. The communicating behavior corresponds well to the function of an INHIBIT logic gate. 相似文献
130.