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991.
The yellow compound species pyoverdin was isolated from Pseudomonas chlororaphis. Degradation of triphenyltin (TPT) by pyoverdin (20 mg) was carried in distilled water (30 ml) containing a 6 µg l?1 concentration of TPT at 20 °C for 96 h in aerobic conditions. The organotins in water and sea water were analyzed by gas chromatograph–mass spectrometry in selected ion mode. TPT and diphenyltin (DPT) in sea water were degraded to monophenyltin (MPT) with pyoverdins isolated from P. chlororaphis. Degradation of TPT in sea water increased with increasing temperature between 4 and 37 °C. Optimum degradation of TPT in sea water was at pH 7–8.5. Degradation of TPT and DPT in distilled water can be faster than in sea water. Also, degradation of TPT in both water and sea water was faster than that of DPT. Tributyltin, dibutyltin, monobutyltin and MPT in water and sea water were not degraded by pyoverdins isolated from P. chlororaphis. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
992.
Two binaphthyl crown receptors containing phenylboric acid 2 and 2,4-dinitrophenylurea 3 as lariat parts were prepared from the optically active binaphthyl crown alcohol 1 in two and four steps, respectively. Host 2 showed a 30% extraction efficiency for GABA by a solid-liquid extraction method in DMSO. Chromogenic Host 3 discriminated the guest linear amino acid by molecular length and the information was revealed through color changes. 相似文献
993.
Toshikazu KomodaYasumasa Sugiyama Naoki AbeMisako Imachi Hiroshi Hirota Hiroyuki KoshinoAkira Hirota 《Tetrahedron letters》2003,44(40):7417-7419
The chemical structure of tetrapetalone A (1), a novel lipoxygenase inhibitor from Streptomyces sp., was revised by using the 1H-15N HMBC technique. Furthermore, the absolute stereochemistry of all the asymmetric carbons in 1 was determined based on the detailed NOE data of 1 and its derivative. 相似文献
994.
Srinivasan A Ishizuka T Osuka A Furuta H 《Journal of the American Chemical Society》2003,125(4):878-879
Meso-hexakis(pentafluorophenyl)-substituted doubly N-confused hexaphyrins and their metal complexes were synthesized for the first time, and the structures were elucidated by X-ray single-crystal analyses. The free base form of oxidized hexaphyrin (5) had two preorganized N3O pockets in the macrocyclic core, where a hydrogen-bonding network was formed to keep the molecule planar (the mean plane deviation is 0.054 A). The formation of a planar bis-Cu(II) complex was confirmed by UV/vis, magnetic susceptibility measurements, and X-ray crystallography. The bis-Ni(II) complex (7), on the other hand, was distored from planarity, but it changed to the planar structure upon solvent (acetonitrile) coordination as judged by the observation of a sharp Soret-like band in absorption spectra and the X-ray structures of the complexes. 相似文献
995.
Asako Hirai Masaki Tsuji Hiroyuki Yamamoto Fumitaka Horii 《Cellulose (London, England)》1998,5(3):201-213
Effects of polymer additives on the formation of microfibrils of bacterial cellulose have been examined by transmission electron microscopy. Among additives with different degrees of polymerization (DP) or substitution (DS), carboxymethyl cellulose sodium salt (CMC) with DP = 80 and DS = 0.57 is the most effective in producing separate, smaller-size microfibrils. By increasing the concentration of this CMC from 0.1 to 1.5%, the percentage of microfibrils measuring 3–7 nm wide is increased and levels off at around 1.0%. Other polymer additives such as xyloglucan are less effective than CMC in producing microfibrils with smaller sizes and the resulting microfibrils still tend to aggregate. The number of charged substituents and the molecular weight seem to be important factors in the production of highly separate smaller-size microfibrils. The reduction in average microfibril size is well correlated to the decrease in mass fraction of cellulose I in bacterial cellulose crystals. On the basis of these results, the mechanism of the crystallization of celluloses I and I is discussed. The effect of colony types, smooth and rough, on the formation of microfibrils in the presence of CMC is also described. 相似文献
996.
Hiroyuki Takemura Teruo Shinmyozu Hirokazu Miura Islam Ullah Khan Takahiko Inazu 《Journal of inclusion phenomena and macrocyclic chemistry》1994,19(1-4):193-206
Side arm modifications of hexahomotriazacalix[3]arene (1) were achieved by simple synthetic methods. Compound5 has picolyl side arms and liquid-liquid extraction experiments showed that the alkali cation affinity of5 is much stronger than that of1. A chiral group was also introduced into the azacalixarene structure. Calix[4]arene was converted into dihomoazacalix[4]arene (2) in 8% yield. Clathrate formation of2 with various solvents is described. MM3 calculations were carried out onp-substituted analogs of2. The self-filled structure, in which the benzyl side arm is placed in its cavity, is the most stable structure when thep-positions of the aromatic rings carry small substituents. Strong hydrogen bonds between nitrogen and phenolic hydroxyl groups in dihomoazacalix[4]arene (2) were observed at low temperatures. The1H-NMR signals of phenolic hydroxyl groups appeared as six singlets in the range of 9.817.1 ppm at –70°C.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes. 相似文献
997.
Takahashi S Souma K Hashimoto R Koshino H Nakata T 《The Journal of organic chemistry》2004,69(13):4509-4515
The C(2)-symmetric macrodiolide core 2 of an antiviral agent, macroviracin A (1), was constructed in a single step by the intermolecular macrodimerization of C(22)-hydroxy carboxylic acid 3 with 2-chloro-1,3-dimethylimidazolinium chloride and DMAP in the presence of sodium hydride (NaH). The use of potassium hydride instead of NaH caused the intramolecular cyclization, predominantly providing the corresponding monomer 26. The acid 3 was synthesized through a series of reactions such as the coupling reaction of acetylene 5 and oxirane 6, stereoselective glycosidation with the trichloroacetimidate method, and Jones oxidation. 相似文献
998.
Tsukada N Mitsuboshi T Setoguchi H Inoue Y 《Journal of the American Chemical Society》2003,125(40):12102-12103
Reactions of alkynes with arenes proceeded in the presence of dinuclear palladium complexes and trialkylboranes to yield alkyne hydroarylation products with high stereoselectivity. In the reactions of monosubstituted benzenes, meta and para products were formed in statistical ratios, while no ortho isomers were detected. 相似文献
999.
Hiroyuki Kakei Riichiro Tsuji Dr. Takashi Ohshima Dr. Hiroyuki Morimoto Shigeki Matsunaga Dr. Masakatsu Shibasaki Prof. Dr. 《化学:亚洲杂志》2007,2(2):257-264
The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)3–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)3–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent. 相似文献
1000.
Synthetic polymers which can adsorb bisphenol A (BPA) and related compounds were prepared by a covalent molecular imprinting technique. BPA dimethacrylate, used as template molecule, was polymerized with a crosslinker, triethylene glycol dimethacrylate (TEGDMA) or trimethylol propane trimethacrylate (TRIM). After the polymerization treatment with dilute NaOH was used to cleave BPA from the polymers. For high recovery of BPA with low polymer matrix degradation, the hydrolysis conditions were determined to be treatment with 1.0 mol L–1 NaOH for 48 h. The binding sites generated by the hydrolysis were evaluated by determination of the retentivity of BPA, BPA analogues, and other endocrine disruptors. The polymers strongly adsorbed compounds with two hydroxyl groups at the 4,4-positions. Generally the TEGDMA-based polymers had stronger affinity than the TRIM-based polymers, although the TRIM-based polymer adsorbed steroidal hormones with two hydroxyl groups, for example 17-estradiol and 17-estradiol, more strongly than the TEGDMA-based polymer, meaning that the crosslinkers affected the properties of the binding sites and, depending upon the target molecules, suitable crosslinkers should be chosen in this system. 相似文献