全文获取类型
收费全文 | 545篇 |
免费 | 23篇 |
国内免费 | 2篇 |
出版年
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 10篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 13篇 |
2015年 | 23篇 |
2014年 | 25篇 |
2013年 | 32篇 |
2012年 | 43篇 |
2011年 | 37篇 |
2010年 | 26篇 |
2009年 | 27篇 |
2008年 | 25篇 |
2007年 | 31篇 |
2006年 | 25篇 |
2005年 | 24篇 |
2004年 | 26篇 |
2003年 | 23篇 |
2002年 | 26篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1970年 | 5篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1913年 | 1篇 |
排序方式: 共有570条查询结果,搜索用时 15 毫秒
1.
Mario Prandini Gemma Gherson Alessandro Salvaterra Giulio Benamati Gino Zambanini Silvia Conci 《Aerobiologia》1992,8(1):38-45
Summary A study to evaluate and define the atmospheric pollen concentration in Trentino was carried out through the aerobiologic sampling in three localities chosen according to their different climatic conditions.1375 patients with pollinosis living in Trentino were studied retrospectively over the period ranging from 1986 to 1988 and selected according to the area they came from.Results have proved that the most allergenic pollen types are the following: Poaceae, Urticaceae (Parietaria), Compositae (Artemisia) and the tree pollen of Betulaceae and Corylaceae (Alnus, Betula, Corylus), and that pollinosis caused by such pollen, types has different features and frequencies according to the different localities.As far as symptoms are concerned, our data shows that rhinoconjuntivitis is more frequent in those patients who are allergic toParietaria while asthma results being more frequent in patients who are allergic to tree pollen. 相似文献
2.
An RNA molecule copurifies with RNase P activity from Xenopus laevis oocytes. 总被引:7,自引:5,他引:2 下载免费PDF全文
Utilizing a procedure for the purification of RNase P from Xenopus laevis germinal vesicle (GV) extracts, according to which the contamination by a large, cytoplasmic, cylindrical structure (1) is avoided, we demonstrate that the X.laevis enzyme, like the HeLa RNase P, is precipitated by anti-Th antibodies and an RNA molecule (XL RNA), 320 nucleotides long, copurifies with the activity. The sequence of XL RNA is 60% homologous to HeLa H1 RNA, therefore the two molecules seem related. 相似文献
3.
A Ruffatti G De Silvestro P Meneghini A Doria E Pellizzaro P F Gambari S Todesco 《Bollettino della Società italiana di biologia sperimentale》1983,59(8):1160-1164
IgM, IgA, IgG rheumatoid factors were investigated by a indirect immunofluorescence method in three groups of patients affected with rheumatoid arthritis of various picture: 30 patients with mild articular disease, 20 with severe joint involvement and 19 with articular and systemic symptoms. Rheumatoid factors occurred more frequently in patients with articular and extraarticular severe rheumatoid arthritis; moreover these patients showed higher titres and higher incidence of different immunoglobulin class rheumatoid factors in comparison with rheumatoid patients having mild joint disease. 相似文献
4.
Duplication of an Xp segment that includes the ZFX locus causes sex inversion in man 总被引:6,自引:6,他引:0
Gerd Scherer Werner Schempp Carlo Baccichetti Elisabetta Lenzini Franca Dagna Bricarelli Laura Doria Lamba Carbone Ulrich Wolf 《Human genetics》1989,81(3):291-294
Summary Two 46,XY females with tandem duplications of an X short arm segment were studied by cytogenetic and Southern blot analysis. The results show that the duplicated segment in each case included the Xp21.2–Xp22.2 interval, resulting in a double dose of ZFX on the single active X chromosome. The results from our two cases, in conjunction with those reported by other workers, lead us to conclude that the duplication is the reason for the sex inversion. If ZFY and ZFX are indeed sex-determining gene loci, these findings favour a model of sex determination characterized by antagonistic interaction between these genes. 相似文献
5.
Paolo AscenziAlberto Bertollini Roberto Santucci Gino AmiconiMassimo ColettaAlessandro DesideriBruno GiardinaFrancesca PolizioRoberto Scatena 《Journal of inorganic biochemistry》1993,50(4):263-272
The cooperative effect of inositol hexakisphosphate (IHP), bezafibrate (BZF), and clofibric acid (CFA) on the spectroscopic (EPR and absorbance) properties of the nitric oxide derivative of ferrous human hemoglobin (HbNO) has been investigated quantitatively. In the presence of IHP, BZF, and CFA, the X-band EPR spectra and the absorption spectra in the Soret region of HbNO display the same basic characteristics described in the presence of 2,3-diphosphoglycerate (2,3-DPG), which have been attributed to a low affinity conformation of the tetramer. Addition to HbNO of two allosteric effectors together (such as IHP and BZF, or IHP and CFA) further stabilizes the low affinity conformation of the ligated hemoprotein (i.e., HbNO). Moreover, in the presence of saturating amounts of IHP, the affinity of BZF and CFA for HbNO increases by about fifteenfold. Likewise, in the presence of both IHP and BZF, as well as in IHP and CFA, the oxygen affinity for ferrous human hemoglobin (Hb) is reduced with respect to that observed in the presence of IHP, BZF, or CFA alone, which in turn is lower than that reported in the absence of any allosteric effector. All the data were obtained at pH 7.0 (in 1.0 × 10−1 M N-[2-hydroxyethyl]piperazine-N′-[2-ethanesulfonic acid]/NaOH buffer system plus 1.0 × 10−1 M NaCl), as well as at 100 K and/or 20°C. The results here reported represent clearcut evidence for the cooperative and specific (i.e., functionally relevant) binding of IHP, BZF, and CFA to Hb. 相似文献
6.
Maura Turriani Rossana Pesi Antonella Nardone Gino Turchi Francesco Sgarrella Pier Luigi Ipata Maria Grazia Tozzi 《Journal of biochemical and molecular toxicology》1994,9(1):51-57
Nucleoside phosphotransferase acting on inosine and deoxyinosine has been partially purified from cultured Chinese hamster lung fibroblasts (V79). The activity is associated with a cytosolic 5′-nucleotidase acting on IMP and deoxyIMP. The transfer of the phosphate group from IMP to inosine catalyzed by this enzyme was activated by ATP and 2,3-bisphosphoglycerate. Inosine, deoxyinosine, guanosine, deoxyguanosine, and the nucleoside analogs 2′,3′-dideoxyinosine and 8-azaguanosine are substrates, while adenosine and deoxyadenosine are not. IMP, deoxyIMP, GMP, and deoxyGMP are the best phosphate donors. The cytosolic 5′-nucleotidase/phosphotransferase substrate, 8-azaguanosine, was found to be very toxic for cultured fibroblasts (LD50 = 0.32 μM). Mutants resistant to either 8-azaguanosine and the correspondent base 8-azaguanine were isolated and characterized. Our results indicated that the 8-azaguanosine-resistant cells were lacking both cytosolic 5′-nucleotidase and hypoxanthine-guanine phosphoribosyltransferase, while 8-azaguanine resistant cells were lacking only the latter enzyme. Despite this observation, both mutants displayed 8-azaguanosine resistance, thus indicating that cytosolic 5′-nucleotidase is not essential for the activation of this nucleoside analog. 相似文献
7.
Gino Giannaccini Claudia Martini Antonio Lucacchini Enrica Strettoi Marco Piccolino† 《Journal of neurochemistry》1993,61(4):1263-1269
Abstract: The binding of [3 H]flunitrazepam, [3 H]RO 5-4864, and [3 H]PK 11195 to membrane preparations of the retina was studied in the turtle and rabbit. Only a single population of [3 H]flunitrazepam binding sites was detected in the turtle, whereas two populations appeared to be present in the rabbit. No specific binding for [3 H]RO 5-4864 and [3 H]PK 11195 could be detected in the turtle. In rabbit, both ligands bound with high affinity, revealing a significant population of binding sites (KD values of 24 ± 2.3 and 2.2 ± 0.8 nM, and Bmax values of 440 ± 35 and 1,482 ± 110 fmol/mg of protein, respectively). The binding was temperature - and protein-dependent. Displacement studies showed a similar rank order of potency of various unlabeled ligands against both [3 H]RO 5-4864 and [3 H]PK 11195 (PK 11195 > Ro 5-4864 > flunitrazepam > flumazenil). These results suggest that peripheral-type benzodiazepine receptors are present in the retina of the rabbit, but not of the turtle. 相似文献
8.
Christian Bonhomme Jocelyne Maquet Jacques Livage Gino Mariotto 《Inorganica chimica acta》1995,230(1-2):85-95
Seven new mono- and/or dimercurated compounds involving acetylacetone (2,4-pentanedione) or ethyl acetoacetate (3-ethyl ketobutanoate) were synthesized in aqueous medium. In all cases, mercuration occurred at methylene carbon atoms. All compounds were carefully analyzed by solid state carbon-13 nuclear magnetic resonance. Assignments were confirmed by using selective sequences, which allowed a total editing of the spectra. It was shown that deshielding of 13C mercurated sites occurred when the rate of mercuration increased. It was also possible to measure direct 1J(199Hg13C) coupling constants. The main bands of the vibrational spectra (infrared and Raman) were assigned. It was proved that v(C = O) and δ(C(γ)-H) could be directly related to the mercuration rate of molecules. 相似文献
9.
Gino Toffano Silvio Mazzari Adriano Zanotti Alessandro Bruni 《Neurochemical research》1984,9(8):1065-1073
The influence of phosphatidylserine (PS) on the isoniazid-induced convulsions has been studied in mice. Sonicated dispersions of this phospholipid given intravenously do not show anticonvulsant activity but they do so when -aminobutyric acid (GABA) is simultaneously injected. GABA alone is inactive. The synergism between PS and GABA is influenced by the structure of the phospholipid liposomes. In contrast to multilamellar vesicles, oligolamellar vesicles are active. Under these conditions the effect shows head group specificity, in that the neutral phosphatidylcholine (PC) or the acidic phosphatidylinositol (PI) are inactive, either in the presence or in the absence of GABA. Lysophosphatidylserine (lysoPS), the deacylated PS derivative, shows increased efficacy as an isoniazid antagonist in the presence of GABA, and has anticonvulsant activity also in the absence of GABA. Other lysophospholipids are inactive. It is suggested that PS, after its metabolic conversion to lysoPS, enhances the anticonvulsant effect of GABA. 相似文献
10.
Olga Vargas María DEL Carmen Doria de Lorenzo María Cristina Saldate F. Orrego 《Journal of neurochemistry》1977,28(1):165-170
The release of [3H]GABA induced by elevated extracellular potassium (K)o, from thin rat brain cortex slices, has been compared with that of [3H]noradrenaline ([3H]NA), released by the same procedures, both from normal slices, and from slices pre-treated with reserpine and nialamide, [3H]NA being predominantly a vesicular component in the former situation, and a soluble substance in the latter one. 46 mM-(K)o released considerably more [3H]NA from normal than from drug-treated slices, while the release of GABA was about two thirds of the latter. When 4min ‘pulses’ of increasing concentrations of potassium were applied, it was observed that the release of GABA and of [3H]NA from drug-treated slices increased in proportion to (K)o, up to 36-46 mM and then declined considerably with higher (K)o. The dependency of potassium-induced release on the concentration of calcium in the medium, indicated that release of [3H]NA from normal slices was proportional to calcium up to 1.5-2 mM, while that of [3H]NA from drug-treated slices increased up to 0.5 mM-Calcium, and then declined with higher concentrations. GABA release also increased up to 0.5 mM-calcium, but no further changes were observed at higher concentrations. The calcium antagonist D-600 inhibited high (K)o-induced release of [3H]NA from normal slices to a greater extent than that of [3H]GABA or of [3H]NA from drug-treated slices. These results, in which elevated (K)o-induced release of [3H]GABA resembles considerably that of soluble NA, but differs from that of NA present in synaptic vesicles, suggest that release of [3H]GABA also occurs from the soluble cytoplasmic compartment, and that the partial calcium requirement that is found is unrelated to that of transmitter secretion. These findings are also a further indication of the lack of specificity of elevated (K)o as a stimulus for inducing transmitter secretions. 相似文献