全文获取类型
收费全文 | 6265篇 |
免费 | 404篇 |
出版年
2023年 | 16篇 |
2022年 | 56篇 |
2021年 | 105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 | 334篇 |
2009年 | 292篇 |
2008年 | 359篇 |
2007年 | 355篇 |
2006年 | 343篇 |
2005年 | 306篇 |
2004年 | 286篇 |
2003年 | 287篇 |
2002年 | 266篇 |
2001年 | 46篇 |
2000年 | 47篇 |
1999年 | 54篇 |
1998年 | 84篇 |
1997年 | 54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6669条查询结果,搜索用时 265 毫秒
971.
Sophie Monsarrat Simon Benhamou Fran?ois Sarrazin Carmen Bessa-Gomes Willem Bouten Olivier Duriez 《PloS one》2013,8(1)
Feeding stations are commonly used to sustain conservation programs of scavengers but their impact on behaviour is still debated. They increase the temporal and spatial predictability of food resources while scavengers have supposedly evolved to search for unpredictable resources. In the Grands Causses (France), a reintroduced population of Griffon vultures Gyps fulvus can find carcasses at three types of sites: 1. “light feeding stations”, where farmers can drop carcasses at their farm (spatially predictable), 2. “heavy feeding stations”, where carcasses from nearby farms are concentrated (spatially and temporally predictable) and 3. open grasslands, where resources are randomly distributed (unpredictable). The impact of feeding stations on vulture’s foraging behaviour was investigated using 28 GPS-tracked vultures. The average home range size was maximal in spring (1272±752 km2) and minimal in winter (473±237 km2) and was highly variable among individuals. Analyses of home range characteristics and feeding habitat selection via compositional analysis showed that feeding stations were always preferred compared to the rest of the habitat where vultures can find unpredictable resources. Feeding stations were particularly used when resources were scarce (summer) or when flight conditions were poor (winter), limiting long-ranging movements. However, when flight conditions were optimal, home ranges also encompassed large areas of grassland where vultures could find unpredictable resources, suggesting that vultures did not lose their natural ability to forage on unpredictable resources, even when feeding stations were available. However during seasons when food abundance and flight conditions were not limited, vultures seemed to favour light over heavy feeding stations, probably because of the reduced intraspecific competition and a pattern closer to the natural dispersion of resources in the landscape. Light feeding stations are interesting tools for managing food resources, but don’t prevent vultures to feed at other places with possibly high risk of intoxication (poison). 相似文献
972.
James K. Nuñez Jin Chen Greg C. Pommier J. Zachery Cogan Joseph M. Replogle Carmen Adriaens Gokul N. Ramadoss Quanming Shi King L. Hung Avi J. Samelson Angela N. Pogson James Y.S. Kim Amanda Chung Manuel D. Leonetti Howard Y. Chang Martin Kampmann Bradley E. Bernstein Volker Hovestadt Jonathan S. Weissman 《Cell》2021,184(9):2503-2519.e17
- Download : Download high-res image (281KB)
- Download : Download full-size image
973.
A Xenogeneic-Free Protocol for Isolation and Expansion of Human Adipose Stem Cells for Clinical Uses
974.
975.
Carmen Díaz-Paniagua 《Ecography》1992,15(3):267-272
Timing of larval periods of 9 species of amphibians (Hyla meridionalis, Pelobates cultripes, Discoglossus galganot, Bufo calamita, Bufo bufo, Rana perezi, Triturus marmoratus, Triturus boscat, Pleurodeles waltl) was followed in 7 different years Total larval season may last from autumn to summer, whereas in low rainy years it may last from late winter to summer In rainy years, two species are early breeders, starting to breed m autumn, six species commonly start in mid-winter and one species always breeds later, in spring The widest interannual variability m the onset and duration of larval season occurs in the earliest breeders In general, the more rainy the autumn and the higher temperatures were reached, the earlier the season started In contrast, duration of the season was not correlated with rainfall and temperature Interannual variability is interpreted as the possibility of adjusting the reproduction of the species to the availability of breeding habitats, constrained by physiological features of the species and interspecific relationships 相似文献
976.
Recent research on mental representation of complex action has revealed distinct differences in the structure of representational frameworks between experts and novices. More recently, research on the development of mental representation structure has elicited functional changes in novices'' representations as a result of practice. However, research investigating if and how mental practice adds to this adaptation process is lacking. In the present study, we examined the influence of mental practice (i.e., motor imagery rehearsal) on both putting performance and the development of one''s representation of the golf putt during early skill acquisition. Novice golfers (N = 52) practiced the task of golf putting under one of four different practice conditions: mental, physical, mental-physical combined, and no practice. Participants were tested prior to and after a practice phase, as well as after a three day retention interval. Mental representation structures of the putt were measured, using the structural dimensional analysis of mental representation. This method provides psychometric data on the distances and groupings of basic action concepts in long-term memory. Additionally, putting accuracy and putting consistency were measured using two-dimensional error scores of each putt. Findings revealed significant performance improvements over the course of practice together with functional adaptations in mental representation structure. Interestingly, after three days of practice, the mental representations of participants who incorporated mental practice into their practice regime displayed representation structures that were more similar to a functional structure than did participants who did not incorporate mental practice. The findings of the present study suggest that mental practice promotes the cognitive adaptation process during motor learning, leading to more elaborate representations than physical practice only. 相似文献
977.
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
978.
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
979.
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
980.
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