全文获取类型
收费全文 | 6233篇 |
免费 | 404篇 |
出版年
2023年 | 16篇 |
2022年 | 26篇 |
2021年 | 104篇 |
2020年 | 63篇 |
2019年 | 88篇 |
2018年 | 130篇 |
2017年 | 108篇 |
2016年 | 199篇 |
2015年 | 312篇 |
2014年 | 359篇 |
2013年 | 483篇 |
2012年 | 600篇 |
2011年 | 534篇 |
2010年 | 335篇 |
2009年 | 292篇 |
2008年 | 359篇 |
2007年 | 355篇 |
2006年 | 343篇 |
2005年 | 306篇 |
2004年 | 287篇 |
2003年 | 286篇 |
2002年 | 266篇 |
2001年 | 46篇 |
2000年 | 47篇 |
1999年 | 54篇 |
1998年 | 84篇 |
1997年 | 52篇 |
1996年 | 50篇 |
1995年 | 54篇 |
1994年 | 43篇 |
1993年 | 38篇 |
1992年 | 45篇 |
1991年 | 12篇 |
1990年 | 24篇 |
1989年 | 15篇 |
1988年 | 19篇 |
1987年 | 19篇 |
1986年 | 12篇 |
1985年 | 18篇 |
1984年 | 25篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1966年 | 5篇 |
排序方式: 共有6637条查询结果,搜索用时 15 毫秒
991.
Carmen Wängler Ralf Schirrmacher Peter Bartenstein Björn Wängler 《Bioorganic & medicinal chemistry letters》2009,19(7):1926-1929
Commonly applied methods for radiometal-labeling of proteins require complex and protracted derivatization reactions of the protein and the subsequent radiolabeling is time-consuming due to the low reaction temperatures applicable. Therefore, a convenient and efficient prelabeling technique for proteins using the DOTA derivative 2,2′,2′′-(10-(2-(2-mercaptoethylamino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid (thiol-DOTA) containing a thiol moiety for rapid and selective introduction into maleimide-derivatized proteins was developed. Thiol-DOTA was labeled with 68Ga, 90Y and 177Lu and subsequently introduced into bovine serum albumin and a human IgG with maximum radiochemical yields of 66%. The entire radiolabeling procedure was completed after only 30 min making this a favorable new labeling technique for proteins. 相似文献
992.
The pollen content of twenty-four unifloral honey samples from twelve different apiaries in La Palma (Canary Islands) was subjected to qualitative and quantitative melissopalynological analysis. The quantitative analysis showed that 4% of the honey belonged to Maurizio's Class I, 8% to Class II, 58% to Class III, 17% to Class IV and 13% to Class V. According to the qualitative analysis, eight honeys were typified as unifloral of Castanea sativa , five of Carlina salicifolia , three of Echium brevirame , three of Reseda luteola , two of Erica arborea , two of Lotus hillebrandii and one of Lamiaceae Origanum vulgare ssp. virens -type. No honeydew elements were found. 62 pollen types were identified belonging to 42 different families. There is no pollen type common to all samples but Foeniculum vulgare -type is present in 22 of the samples (91.7%) and the combination Cistus sp., Erica arborea , Aspalthium bituminosum , Origanum vulgare ssp. virens -type and Rumex sp. in 21 (87.5%). The organoleptic analysis indicated that they are of good quality. 相似文献
993.
Antonio Hernandes Chaves Neto Karla Cristiana Queiroz Renato Milani Edgar Julian Paredes‐Gamero Giselle Zenker Justo Maikel P. Peppelenbosch Carmen Veríssima Ferreira 《Journal of cellular biochemistry》2011,112(1):71-77
Despite numerous reports on the ability of ascorbic acid and β‐glycerophosphate (AA/β‐GP) to induce osteoblast differentiation, little is known about the molecular mechanisms involved in this phenomenon. In this work, we used a peptide array containing specific consensus sequences (potential substrates) for protein kinases and traditional biochemical techniques to examine the signaling pathways modulated during AA/β‐GP‐induced osteoblast differentiation. The kinomic profile obtained after 7 days of treatment with AA/β‐GP identified 18 kinase substrates with significantly enhanced or reduced phosphorylation. Peptide substrates for Akt, PI3K, PKC, BCR, ABL, PRKG1, PAK1, PAK2, ERK1, ERBB2, and SYK showed a considerable reduction in phosphorylation, whereas enhanced phosphorylation was observed in substrates for CHKB, CHKA, PKA, FAK, ATM, PKA, and VEGFR‐1. These findings confirm the potential usefulness of peptide microarrays for identifying kinases known to be involved in bone development in vivo and in vitro and show that this technique can be used to investigate kinases whose function in osteoblastic differentiation is poorly understood. J. Cell. Biochem. 112: 71–77, 2011. © 2010 Wiley‐Liss, Inc. 相似文献
994.
J. F. Calzada C. Rolz Maria del Carmen de Arriola H. Castaneda J. E. Godoy 《World journal of microbiology & biotechnology》1986,2(4):489-492
Summary Results from the operation of methanogenic reactors of three different sizes, using coffee pulp juice as raw material, are presented. All reactors were packed with unreticulated polyurethane foam and geometrical similarity was maintained. Pilot plant operation showed lower gas production per unit reactor volume but higher conversions per unit of organic load, even at lower temperatures.
Paper presented at the VII International Conference on the Global Impacts of Applied Microbiology, Helsinki, 12–16 August 1985. 相似文献
Resumen Se presentan los resultados de la operación de tres reactores metano-génicos de differente tamaño, usando jugo de pulpa de café como materia prima. Los reactores fueron empacados con esponja de poliuretano no reticulado y se mantuvo una similitud geométrica. La operación de una planta piloto mostró una menor producción de gas por unidad volumétrica de reactor pero conversiones mejores, aún a más bajas temperaturas.
Résumé Les résultats présentés concernant le fonctionnement de trois réacteurs méthanogènes de dimensions différentes, utilisant comme matière première le jus de pulpe de café. Tous les réacteurs étaient compactés avec de la mousse de polyuréthane non réticulée, et avaient des formes géométriques similaires. Les opérations à l'échelle pilote ont donné une moindre production de gaz par unité de volume, mais un taux de conversion par unité de charge organique plus élevé, même à des températures inférieures.
Paper presented at the VII International Conference on the Global Impacts of Applied Microbiology, Helsinki, 12–16 August 1985. 相似文献
995.
Julia O. Sonsin Peter E. Gasson FLS Claudia F. Barros Carmen R. Marcati 《Botanical journal of the Linnean Society. Linnean Society of London》2012,170(2):257-276
A comparative study of the secondary xylem (wood) anatomy of 11 species (38 specimens) occurring in cerrado s.s. and the adjacent gallery forest (both cerrado s.l. habitat) was made with the aim of identifying the anatomical characteristics of ecological value and correlating them with the environmental conditions. The anatomical features that vary, in general, between the two habitats are: growth ring distinctness (well or poorly defined); tyloses and deposits (more abundant in cerrado specimens); gelatinous fibres (more evident in cerrado specimens and in different patterns between habitats); variation in paratracheal and banded parenchyma (more abundant in cerrado); and more cells per parenchyma strand in cerrado. In general, gallery forest specimens have wider vessels, fewer vessels per square millimetre and larger intervessel pits, indicating more efficient water conduction, whereas cerrado s.s. specimens are the opposite, with low vulnerability and mesomorphy indices, demonstrating greater safety under conditions of water stress. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ?? , ??–??. 相似文献
996.
Carmen González-Lluch Joaquín L. Sancho-Bru Pablo-Jesús Rodríguez-Cervantes 《Computer methods in biomechanics and biomedical engineering》2014,17(10):1108-1118
Many studies have investigated the effect of different parameters of the endodontically restored tooth on its final strength, using in vitro tests and model simulations. However, the differences in the experimental set-up or modelling conditions and the limited number of parameters studied in each case prevent us from obtaining clear conclusions about the relative importance of each parameter. In this study, a validated 3D biomechanical model of the restored tooth was used for an exhaustive sensitivity analysis. The individual influence of 20 different parameters on the mechanical performance of an endodontic restoration with prefabricated posts was studied. The results bring up the remarkable importance of the loading angle on the final restoration strength. Flexural loads are more critical than compressive or tensile loads. Young's modulus of the post and its length and diameter are the most influential parameters for strength, whereas other parameters such as ferrule geometry or core and crown characteristics are less significant. 相似文献
997.
Flavio Flamigni Gabriele Campana Lucia Carboni Carmen Rossoni Santi Spampinato 《Biochimica et Biophysica Acta (BBA)/General Subjects》1994,1201(1):101-105
Addition of Zn2+_ to cell medium inhibited the induction of ornithine decarboxylase (ODC) activity in ODC overproducing L1210-DFMOr cells. A significant effect was observed at a concentration as low as 0.01 mM, however a more marked inhibition was caused by the addition of 0.1 mM Zn2+. The inhibition of the induction of ODC activity was accompanied by a proportional decrease in the content of immunoreactive ODC protein, whereas the level of ODC mRNA, detemined by a solution hybridization RNase protection assay, was not affected signigicantly. Instead, some acceleration of ODC turnover was observed. the addition of 0.1 mM Co2+ or Mn2+, but not of other divalent metal ions, also inhibited ODC induction; differently from Zn2+ however, these metals affected cell viability and/or cell growth. Removal of endogenous Zn2+ by a chelator also provoked a strong decrease of ODC induction, which was reversed by Zn2+. However, addition of Zn2+ in excess of the chelator proved to be markedly inhibitory. These results indicate that both a restricted Zn2+ availability and an enhanced presence of the metal can inhibit the induction of ODC in L1210-DFMOr cells. 相似文献
998.
Francesca Pennacchietti Stefania Abbruzzetti Aba Losi Carmen Mandalari Roberta Bedotti Cristiano Viappiani Francesca Cella Zanacchi Alberto Diaspro Wolfgang G?rtner 《PloS one》2014,9(9)
We report thermal recovery kinetics of the lit state into the parental dark state, measured for the blue light-sensing photoreceptor YtvA inside overexpressing E. coli and B. subtilis bacterial cells, performed for the wild type and several mutated proteins. Recovery was followed as a recovery of the fluorescence, as this property is only found for the parental but not for the photochemically generated lit state. When cells were deposited onto a microscope glass plate, the observed thermal recovery rate in the photocycle was found ca. ten times faster in comparison to purified YtvA in solution. When the E. coli or B. subtilis colonies were soaked in an isotonic buffer, the dark relaxation became again much slower and was very similar to that observed for YtvA in solution. The observed effects show that rate constants can be tuned by the cellular environment through factors such as hydration. 相似文献
999.
María A. Ruvira Teresa LucenaMaría J. Pujalte David R. ArahalM. Carmen Macián 《Systematic and applied microbiology》2013
A facultatively anaerobe, moderately halophilic, Gram-negative, filamentous, non motile and unpigmented bacterium, designated M30T, was isolated from coastal Mediterranean Sea water in Valencia, Spain. Phylogenetic analysis based on 16S rRNA sequences placed this strain in the phylum “Bacteroidetes” with Marinifilum fragile JC2469T as its closest relative with 97% sequence similarity. Average nucleotide identity (ANI) values between both strains were far below the 95% threshold value for species delineation (about 89% using BLAST and about 90% using MUMmer). A comprehensive polyphasic study, including morphological, biochemical, physiological, chemotaxonomic and phylogenetic data, confirmed the independent species status of strain M30T within the genus Marinifilum, for which the name Marinifilum flexuosum sp. nov. is proposed. The type strain of Marinifilum flexuosum is M30T (=CECT 7448T = DSM 21950T). 相似文献
1000.