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591.
Nirogi R Kandikere V Mudigonda K Komarneni P Aleti R Boggavarapu R 《Biomedical chromatography : BMC》2008,22(2):214-222
A sensitive high-performance liquid chromatography-positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of sitagliptin, a DPP-4 inhibitor, in human plasma. Following liquid-liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M + H](+) ions, m/z 408-235 for sitagliptin and m/z 310-148 for the internal standard. The assay exhibited a linear dynamic range of 0.1-250 ng/mL for sitagliptin in human plasma. The lower limit of quantification was 0.1 ng/mL with a relative standard deviation of less than 6%. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. A run time of 2.0 min for each sample made it possible to analyze more than 300 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic studies. 相似文献
592.
Kumaraswamy G Sadaiah K Ramakrishna DS Police N Sridhar B Bharatam J 《Chemical communications (Cambridge, England)》2008,(42):5324-5326
A concise route for the syntheses of enantioenriched functionalized scaffolds of medium-sized oxacycles and carbocycles employing the chiral auxiliary-mediated Cu-catalyzed ylide formation/[2,3]-sigmatropic rearrangement as a key step was developed. 相似文献
593.
Balasubramanian Sridhar Krishnan Ravikumar 《Acta Crystallographica. Section C, Structural Chemistry》2008,64(10):o566-o569
In cytosinium succinate (systematic name: 4‐amino‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium 3‐carboxypropanoate), C4H6N3O+·C4H5O4−, (I), the cytosinium cation forms one‐dimensional self‐assembling patterns by intermolecular N—H...O hydrogen bonding, while in cytosinium 4‐nitrobenzoate cytosine monohydrate [systematic name: 4‐amino‐2‐oxo‐2,3‐dihydropyrimidin‐1‐ium 4‐nitrobenzoate 4‐aminopyrimidin‐2(1H)‐one solvate monohydrate], C4H6N3O+·C7H4NO4−·C4H5N3O·H2O, (II), the cytosinium–cytosine base pair, held together by triple hydrogen bonds, leads to one‐dimensional polymeric ribbons via double N—H...O hydrogen bonds. This study illustrates clearly the different alignment of cytosine molecules in the crystal packing and their ability to form supramolecular hydrogen‐bonded networks with the anions. 相似文献
594.
A high-performance liquid chromatographic method and a UV derivative spectrophotometric method for the determination of famciclovir, a highly active antiviral agent, in tablets were developed in the present work. The various parameters, such as linearity, precision, accuracy, specificity, robustness, limit of detection and limit of quantitation were studied according to International Conference on Harmonization guidelines. HPLC was carried out by using the reversed-phase technique on an RP-18 column with a mobile phase composed of 50 mM monobasic phosphate buffer and methanol (50 : 50; v/v), adjusted to pH 3.05 with orthophosphoric acid. The mobile phase was pumped at a flow rate of 1 ml/min and detection was made at 242 nm with UV dual absorbance detector. The first derivative UV spectrophotometric method was performed at 226.5 nm. Statistical analysis was done by Student's t-test and F-test, which showed no significant difference between the results obtained by the two methods. The proposed methods are highly sensitive, precise and accurate and therefore can be used for its Intended purpose. 相似文献
595.
Lahankar SA Chambreau SD Townsend D Suits F Farnum J Zhang X Bowman JM Suits AG 《The Journal of chemical physics》2006,125(4):44303
We present a detailed experimental and theoretical investigation of formaldehyde photodissociation to H(2) and CO following excitation to the 2(1)4(1) and 2(1)4(3) transitions in S(1). The CO velocity distributions were obtained using dc slice imaging of single CO rotational states (v=0, j(CO)=5-45). These high-resolution measurements reveal the correlated internal state distribution in the H(2) cofragments. The results show that rotationally hot CO (j(CO) approximately 45) is produced in conjunction with vibrationally "cold" H(2) fragments (v=0-5): these products are formed through the well-known skewed transition state and described in detail in the accompanying paper. After excitation of formaldehyde above the threshold for the radical channel (H(2)CO-->H+HCO) we also find formation of rotationally cold CO (j(CO)=5-28) correlated to highly vibrationally excited H(2) (v=6-8). These products are formed through a novel mechanism that involves near dissociation followed by intramolecular H abstraction [D. Townsend et al., Science 306, 1158 (2004)], and that avoids the region of the transition state entirely. The dynamics of this "roaming" mechanism are the focus of this paper. The correlations between the vibrational states of H(2) and rotational states of CO formed following excitation on the 2(1)4(3) transition allow us to determine the relative contribution to molecular products from the roaming atom channel versus the conventional molecular channel. 相似文献
596.
Synthesis of beta-hydroxysulfides from alkenes under supramolecular catalysis in the presence of beta-cyclodextrin in water 总被引:1,自引:0,他引:1
An environmentally benign and highly efficient procedure has been developed for the direct one-pot synthesis of beta-hydroxysulfides in good yields under neutral conditions from alkenes and thiophenols in the presence of aerial oxygen using beta-cyclodextrin in water. This protocol tolerates a wide variety of functional groups or substrates and does not require the use of either acid or base catalysts. beta-Cyclodextrin can be recovered and reused for a number of runs without any loss of activity. 相似文献
597.
Journal of Solid State Electrochemistry - 相似文献
598.
599.
600.
Balasubramanian Sridhar Jagadeesh Babu Nanubolu Krishnan Ravikumar 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(7):602-609
Cocrystals are molecular solids composed of at least two types of neutral chemical species held together by noncovalent forces. Crystallization of thymine [systematic name: 5‐methylpyrimidine‐2,4(1H,3H)‐dione] with four phenolic coformers resulted in cocrystal formation, viz. catechol (benzene‐1,2‐diol) giving thymine–catechol (1/1), C5H6N2O2·C6H6O2, (I), resorcinol (benzene‐1,3‐diol) giving thymine–resorcinol (2/1), 2C5H6N2O2·C6H6O2, (II), hydroquinone (benzene‐1,4‐diol) giving thymine–hydroquinone (2/1), 2C5H6N2O2·C6H6O2, (III), and pyrogallol (benzene‐1,2,3‐triol) giving thymine–pyrogallol (1/2), C5H6N2O2·2C6H6O3, (IV). The resorcinol molecule in (II) occupies a twofold axis, while the hydroquinone molecule in (III) is situated on a centre of inversion. Thymine–thymine base pairing is common across all four structures, albeit with different patterns. In (I)–(III), the base pair is propagated into an infinite one‐dimensional ribbon, whereas it exists as a discrete dimeric unit in (IV). In (I)–(III), the two donor N atoms and one carbonyl acceptor O atom of thymine are involved in thymine–thymine base pairing and the remaining carbonyl O atom is hydrogen bonded to the coformer. In contrast, in (IV), just one donor N atom and one acceptor O atom are involved in base pairing, and the remaining donor N atom and acceptor O atom of thymine form hydrogen bonds to the coformer molecules. Thus, the utilization of the donor and acceptor atoms of thymine in the hydrogen bonding is influenced by the coformers. 相似文献