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161.
Harusawa S Araki L Terashima H Kawamura M Takashima S Sakamoto Y Hashimoto T Yamamoto Y Yamatodani A Kurihara T 《Chemical & pharmaceutical bulletin》2003,51(7):832-837
(+)-4(5)-[(2R,5R)-5-aminomethyltetrahydrofuran-2-yl]imidazole [(+)-1, imifuramine] and its 2R,5S-stereoisomer (+)-2 were expected as base compounds to develop selective human histamine H4-receptor ligands. The improved synthesis of (+)-1 was done via cyclization of a diazafulvene intermediate generated by Bu3P/N,N,N',N'-tetramethylazodicarboxamide (TMAD) treatment of a diol 17ab bearing an unsubstituted imidazole moiety in good yields. This methodology also afforded an alternative synthetic route to trans- and cis-ethyl 4(5)-(5-hydroxymethyltetrahydrofuran-2-yl)imidazole carboxylates (5 and 6), reported previously. Also, 4(5)-[(2R,5S)-5-aminomethyltetrahydrofuran-2-yl]imidazole (+)-2 was synthesized from ethyl 4(5)-(2-deoxy-beta-D-ribofuranosyl)imidazole-1-carboxylate (35) via the four steps involving deoxygenation. 相似文献
162.
The higher order structure of proteins solubilized in an bis(2-ethylhexyl) sulfosuccinate sodium (AOT) reverse micellar system was investigated. From circular dichroic (CD) measurement, CD spectra of cytochrome c, which is solubilized at the interface of reverse micelles, markedly changed on going from buffer solution to the reverse micellar solution, and the ellipticity values in the far- and near-UV regions decreased with decreasing the water content (W0: molar ratio of water to AOT), indicating that the secondary and tertiary structures of cytochrome c changed with the water content. The ellipticity of ribonuclease A, which is solubilized in the center of micellar water pool, in the near-UV region was dependent on W0 and became minimum when W0 of ca. 8 while the ellipticity in the far-UV region was almost constant, indicating that the tertiary structure of ribonuclease A was affected by the water content, but the secondary structure was conserved. The degree of curvature of the micellar interface appears to influence the protein structure because the reverse micelle size is linearly proportional to the W0 value. As evidence of this, when the micelle size was comparable to the protein's dimensions, the structures were more affected by the water content. Judging from the dependence of the factor influencing the protein structure on the protein species, the location of solubilized protein in reverse micelles is significantly related to whether the protein structure in the system is affected by the micellar interface. In the cases of cytochrome c and lysozyme, the ellipticity against W0 was dependent on the AOT concentration. In contrast, ribonuclease A gave very similar ellipticity values whatever the AOT concentration. In the n-hexane micellar system, cytochrome c exhibited lower ellipticity values and ribonuclease A in the lower W0 range (W0 < ca. 8) higher ellipticity values. These results indicated that the interaction between the protein and the micellar interface is a dominant factor influencing the protein structure in reverse micelles, and that it is governed by the location of solubilized proteins and the state of the micellar interface. 相似文献
163.
H Hattori S Yamamoto M Iwata E Takashima T Yamada O Suzuki 《Journal of chromatography. A》1992,579(2):247-252
Fourteen phenothiazine derivatives were tested for their detection by gas chromatography (GC) with surface ionization detection (SID). The sensitivity of GC-SID was highest with trimeprazine and levomepromazine, which contain aliphatic tertiary amino side chains, and lowest with thiethylperazine and thioproperazine, which contain sulphur residues. Chlorpromazine, trimeprazine and promazine showed excellent linearity between the SID response and the drug amount in the range 0.25-3.0 pmol on-column. Their detection limits were as low as ca. 5-10 pg (15-30 fmol) on-column (250-500 pg per ml of body fluid). A detailed procedure for isolation of phenothiazines from human whole blood and urine using Sep-Pak C18 cartridges, before the GC with SID, is also presented. The recoveries of the drugs (100 pmol), which were added to 1 ml of whole blood or urine, were more than 79%. The baselines remained steady as the column temperature was increased. 相似文献
164.
A portable tritium sampler was developed for the stepwise collections of water vapour (HTO), hydrogen (HT) and hydrocarbons (CH3T) in the atmosphere. First, water vapour was collected in an electronic cooler and an HTO collection column containing 400 g of molecular sieve. Next, dried air was introduced into an HT collection column containing 150 g of palladium catalyst. Hydrogen was then converted to water by catalytic oxidation at room temperature and the resultant water was immediately adsorbed on the molecular sieve bed supporting the catalyst. The remaining gas was finally introduced into a CH3T collection column containing 100 g of molecular sieve through a platinum catalyst column, in which hydrocarbons were burnt at 400°C. The resultant water was adsorbed in the CH3T collection column. The collection efficiencies of water in the HTO, HT and CH3T collection columns were all estimated to be nearly 100%. This newly developed method was found to be useful for the routine tritium monitoring by applying it to actual air samples. 相似文献
165.
N. Momoshima T. Kaji I. T. Poppy N. Inoue Y. Takashima 《Journal of Radioanalytical and Nuclear Chemistry》1991,150(1):163-169
Tritium concentrations were measured for river waters on two islands in Japan. Significant difference was observed on the distribution of tritium concentrations on both islands, the river water samples from the northern island had higher concentrations and the average was about twice compared to that from the southern island. Higher tritium concentration in precipitation and the larger area of the northern island would be responsible for higher tritium concentrations in river waters. 相似文献
166.
Takashima H Yamada S Obara S Kitamura K Inabata S Miyakawa N Tanabe K Nagashima U 《Journal of computational chemistry》2002,23(14):1337-1346
We developed a novel parallel algorithm for large-scale Fock matrix calculation with small locally distributed memory architectures, and named it the "RT parallel algorithm." The RT parallel algorithm actively involves the concept of integral screening, which is indispensable for reduction of computing times with large-scale biological molecules. The primary characteristic of this algorithm is parallel efficiency, which is achieved by well-balanced reduction of both communicating and computing volume. Only the density matrix data necessary for Fock matrix calculations are communicated, and the data once communicated are reutilized for calculations as many times as possible. The RT parallel algorithm is a scalable method because required memory volume does not depend on the number of basis functions. This algorithm automatically includes a partial summing technique that is indispensable for maintaining computing accuracy, and can also include some conventional methods to reduce calculation times. In our analysis, the RT parallel algorithm had better performance than other methods for massively parallel processors. The RT parallel algorithm is most suitable for massively parallel and distributed Fock matrix calculations for large-scale biological molecules with more than thousands of basis functions. 相似文献
167.
N. Momoshima H. Kawamura Y. Takashima 《Journal of Radioanalytical and Nuclear Chemistry》1993,173(2):323-329
Commerically available CO2 absorbent and its scintillator were used to determine14C in environmental materials. Absorption of CO2 by the CO2 absorbent was quantitative, and strong and stable fixation was confirmed by no release of CO2 from the CO2 absorbent for a long period after absorption. The14C activity was measured by a large-volume low-background liquid-scintillation counter and the counts were quite stable for two weeks. Counting efficiency and background counts varied with the amounts of CO2 absorbed, indicating a change of quenching level with absorption of CO2. The different quenching levels were, however, normalized with external standard channel ratio (ESCR). Specific activity of14C in the present shell was evaluated for samples with different amounts of CO2 absorbed and were consistent with each other within the counting error, suggesting validity of the present method. Contemporary14C level in the environmental materials, 95% CO2 saturated sample, could be measured with 4% counting error (2) by 1000 min counting time. 相似文献
168.
Ming-Rong Zhang Masanao Ogawa Kenji Furutsuka Yuichiro Yoshida Kazutoshi Suzuki 《Journal of fluorine chemistry》2004,125(12):1879-1886
In this study, we report the synthesis and reactivity of [18F]fluoromethyl iodide ([18F]FCH2I) with various nucleophilic substrates and the stabilities of [18F]fluoromethylated compounds. [18F]FCH2I was prepared by reacting diiodomethane (CH2I2) with [18F]KF, and purified by distillation in radiochemical yields of 14-31% (n = 25). [18F]FCH2I was stable in organic solvents commonly used for labeling and aqueous solution with pH 1-7, but was unstable in basic solutions. [18F]FCH2I displayed a high reactivity with various nucleophilic substrates such as phenol, thiophenol, amide and amine. The [18F]fluoromethylated compounds synthesized by the reactions of phenol, thiophenol and tertiary amine with [18F]FCH2I were stable for purification, formulation and storage. In contrast, the [18F]fluoromethylated compounds synthesized by the reactions of primary or secondary amines, and amide with [18F]FCH2I were too unstable to be detected or purified from the reaction mixtures. Defluorination of these [18F]fluoromethyl compounds was a main decomposition route. 相似文献
169.
Reactions between carbon dioxide and fluorine were examined at temperatures of 303-523 K under various pressure and mixture ratios of both gases. Reactions were carried out similarly under the existence of NaF, CsF and EuF3.After the reaction, fluorine was removed and the reaction products were analyzed using FT-IR, GC/FT-IR and GC/MS. The major products were CF3OF, COF2, CF4 and CF2(OF)2.The best yield of COF2 was 11.1% under the reaction condition of CO2/F2 = 76 kPa/76 kPa with temperature of 498 K for 72 h in a direct reaction. The formation rate of COF2 in the direct reaction was estimated as 0.232 dm3 mol−1 h−1 under the reaction conditions of CO2/F2 = 76 kPa/76 kPa, at 498 K. In the presence of CsF, it was estimated as 1.88 dm3 mol−1 h−1 at CO2/F2 = 76 kPa/76 kPa at 498 K.The activation energy of the COF2 formation in the direct reaction was estimated as 45.7 kJ mol−1 at CO2/F2 = 76 kPa/76 kPa at 498 K. In addition, 24.2 and 38.9 kJ mol−1 were evaluated at CO2/F2 = 76 kPa/76 kPa at 498 K, respectively, in the presence of CsF and EuF3. 相似文献
170.
Hiroshi Tatewaki Toshikatsu Koga Hiroyuki Takashima 《Theoretical chemistry accounts》1997,96(4):243-247
We report five minimal-type contracted Gaussian-type function (CGTF) basis sets of the second-row atoms, Na – Ar, for molecular
applications. Three of the present CGTF sets are revised versions of those given by Huzinaga and co-workers and the other
two are newly developed for more accurate calculations. Practical utility and improved reliability of the present basis sets,
augmented by polarization functions, are confirmed by test calculations on the P atom and P2 molecule both at the self-consistent field (SCF) and configuration interaction (CI) levels.
Received: 10 February 1997 / Accepted: 23 April 1997 相似文献