全文获取类型
收费全文 | 4099篇 |
免费 | 307篇 |
国内免费 | 2篇 |
出版年
2023年 | 12篇 |
2022年 | 31篇 |
2021年 | 58篇 |
2020年 | 47篇 |
2019年 | 51篇 |
2018年 | 53篇 |
2017年 | 73篇 |
2016年 | 92篇 |
2015年 | 187篇 |
2014年 | 184篇 |
2013年 | 258篇 |
2012年 | 331篇 |
2011年 | 352篇 |
2010年 | 225篇 |
2009年 | 203篇 |
2008年 | 297篇 |
2007年 | 242篇 |
2006年 | 251篇 |
2005年 | 232篇 |
2004年 | 225篇 |
2003年 | 237篇 |
2002年 | 204篇 |
2001年 | 48篇 |
2000年 | 34篇 |
1999年 | 52篇 |
1998年 | 52篇 |
1997年 | 36篇 |
1996年 | 45篇 |
1995年 | 41篇 |
1994年 | 31篇 |
1993年 | 20篇 |
1992年 | 36篇 |
1991年 | 13篇 |
1990年 | 20篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1971年 | 3篇 |
1915年 | 1篇 |
排序方式: 共有4408条查询结果,搜索用时 500 毫秒
51.
52.
Catherine Curie Thierry Liboz Marie-Hélène Montané Dominique Rouan Michèle Axelos Bernard Lescure 《Plant molecular biology》1992,18(6):1083-1089
In Arabidopsis thaliana, the activation process of the A1 EF-1 gene depends on several elements. Using the GUS reporter gene, transient expression experiments have shown that mutations of upstream cis-acting elements of the A1 promoter, or the deletion of an intron located within the 5 non-coding region, similarly affect expression in dicot or monocot protoplasts. The results reported here strongly suggest that this 5 intron is properly spliced in Zea mays. We show that two trans-acting factors, specifically interacting with an upstream activating sequence (the TEF 1 box), are present in nuclear extracts prepared from A. thaliana, Brassica rapa, Nicotiana tabacum and Z. mays. In addition, a DNA sequence homologous to the TEF 1 box, found at approximately the same location within a Lycopersicon esculentum EF-1 promoter, interacts with the same trans-acting factors. Homologies found between the A. thaliana and L. esculentum TEF 1 box sequences have allowed us to define mutations of this upstream element which affect the interaction with the corresponding trans-acting factors. These results support the notion that the activation processes of A. thaliana EF-1 genes have been conserved among angiosperms and provide interesting data on the functional structure of the TEF 1 box. 相似文献
53.
Jacques Thierry 《Geobios》1976,9(3):291-331
From Bajocian to lower Kimmeridgian, the subfamilyStephanocerataceae represents a large stock of the ammonite fauna. Though it is tributary of author's stratigraphical correlations and systematical interpretations, its geographical distribution with a drifting continents concept gives many teaching about the study of this superfamily, the continental drift and its consequences. Showing a world wide repartition at its apparition this stock then presents branches; the one (Stephanoceratidae) is not envisaged here; the second (Sphaeroceratidae and Cardioceratidae families) characterises rather the «boreal province; the third (Macrocephalitidae family) is chiefly specific of the «tethysian province. A «north-east pacific province with boreal affinities and a «south-east province with tethysian affinities are delimited. It is probably from its fauna that the tethysian macrocephalitid stock appears; first represented by ammonites specifically north american in middle and upper Bathonian stage, they extend during upper Bathonian and lower Callovian and reach South America and the Tethys. The presence of a narrow sea, on Patagonia, West Antarctica, East Africa, Madagascar and India, joining the Tethys and the south edge of Gondwania, is proved at various times, at Bajocian and Callovian stages. 相似文献
54.
Stylianos Mamatas-Kalamaras Thierry Sévenet Claude Thal Pierre Potier 《Phytochemistry》1975,14(7):1637-1639
Five alkaloids have been isolated from Alstonia vitiensis: pleïocarpamine, vincorine, cabucraline, alstovine (11-methoxycompactinervine) and quaternoxine; the latter two are new alkaloids. 相似文献
55.
Thierry Brun Jean Péduzzi Manuela Marin Caniça Gérard Paul Pierre Névot Michel Barthélémy Roger Labia 《FEMS microbiology letters》1994,120(1-2):111-117
Abstract A novel procedure was used to purify a cytosolic chitinase from Candida albicans to electrophoretic homogeneity. The results represent the first demonstration of the purification of a fungal intracellular chitinase using the criterion of a single band detected following silver-staining of a polyacrylamide gel run under denaturing conditions. Purified chitinase had pH and temperature optima of 5.0 and 50°C, respectively. Inhibition of enzyme activity by allosamidin was pH-dependent occuring maximally at pH 8.0. Phospholipids had similar marked and highly specific effects on the activities of both the purified soluble enzyme and a solubilized microsomal chitinase from C. albicans . Evidence is provided for the existence of a complex chitinolytic system in this organism. 相似文献
56.
57.
The appropriateness of the Amplified Fragment Length Polymorphism (AFLP) technique for investigating Chondrus crispus Stackhouse populations in the Maritime Provinces of Canada was assessed. The AFLP procedure was first subjected to reproducibility
testing and three shortcomings were noted: 1) failure to reproduce band intensity between replicate runs for the same individual
and primer pair; 2) failure of some bands to replicate; 3) lack of reproducibility for complete replicate runs for some individuals
and primer pairs. In the last-mentioned case, the lack of reproducibility resulted in characteristic electropherograms indicative
of weak reactions. These weak runs can be attributed to poor restriction digest/ligation reactions and/or substandard PCR,
these failures ultimately resulting from low and inconsistent DNA quality. We recommend that reproducibility testing should
be completed routinely in studies using the AFLP technique. In the current work, only fragments and individuals that gave
reproducible results were used in subsequent analyses. The AFLP method resulted in highly variable markers within and between
the populations of C. crispus included in this investigation, which prevented successful resolution of population structure. This situation could result
from a lack of suitability for AFLP markers in population genetic studies, and/or too extensive genetic variation for C. crispus populations to be discerned by the AFLP technique. These two possible explanations are discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
58.
Simone Benedetto Véronique Drai-Zerbib Marco Pedrotti Geoffrey Tissier Thierry Baccino 《PloS one》2013,8(12)
The mass digitization of books is changing the way information is created, disseminated and displayed. Electronic book readers (e-readers) generally refer to two main display technologies: the electronic ink (E-ink) and the liquid crystal display (LCD). Both technologies have advantages and disadvantages, but the question whether one or the other triggers less visual fatigue is still open. The aim of the present research was to study the effects of the display technology on visual fatigue. To this end, participants performed a longitudinal study in which two last generation e-readers (LCD, E-ink) and paper book were tested in three different prolonged reading sessions separated by - on average - ten days. Results from both objective (Blinks per second) and subjective (Visual Fatigue Scale) measures suggested that reading on the LCD (Kindle Fire HD) triggers higher visual fatigue with respect to both the E-ink (Kindle Paperwhite) and the paper book. The absence of differences between E-ink and paper suggests that, concerning visual fatigue, the E-ink is indeed very similar to the paper. 相似文献
59.
60.
Didjour Albert Kambir Jean Brice Boti Thierry Acafou Yapi Zana Adama Ouattara Mathieu Paoli Ange Bighelli Flix Tomi Joseph Casanova 《化学与生物多样性》2020,17(1)
The chemical composition of 44 leaf oil samples of Laggera pterodonta (DC.) Sch.Bip. ex Oliv. (Asteraceae) from Côte d'Ivoire was investigated, using combination of chromatographic (GC‐FID) and spectroscopic (GC/MS, 13C‐NMR) techniques. Two oil samples chosen according to their chromatographic profiles were submitted to column chromatography and all fractions of CC were analyzed by GC‐FID, GC/MS and 13C‐NMR. In total, 83 components accounting for 96.5 to 99.4 % of the whole chemical composition were identified. Significant variations were observed within terpene classes: monoterpene hydrocarbons (0.4–22.7 %), oxygenated monoterpenes (32.9–54.9 %), sesquiterpene hydrocarbons (18.6–38.3 %) and oxygenated sesquiterpenes (3.5–38.4 %). Thus, the 44 compositions were subjected to hierarchical cluster analysis (HCA) and principal component analysis (PCA). Two groups were differentiated according to their composition. All the samples contained 2,5‐dimethoxy‐p‐cymene, α‐humulene and (E)‐β‐caryophyllene among the main components. Other components were present at appreciable contents and allowed differentiation of two groups: sabinene and germacrene D for Group I; 10‐epi‐γ‐eudesmol and eudesm‐7(11)‐en‐4α‐ol for Group II. All the samples collected in Eastern Côte d'Ivoire constituted Group I, while samples collected in the Central area of the country constituted Group II. 相似文献