全文获取类型
收费全文 | 30583篇 |
免费 | 2465篇 |
国内免费 | 4篇 |
专业分类
33052篇 |
出版年
2023年 | 154篇 |
2022年 | 140篇 |
2021年 | 355篇 |
2020年 | 254篇 |
2019年 | 304篇 |
2018年 | 644篇 |
2017年 | 613篇 |
2016年 | 751篇 |
2015年 | 904篇 |
2014年 | 1028篇 |
2013年 | 1496篇 |
2012年 | 2210篇 |
2011年 | 2315篇 |
2010年 | 1283篇 |
2009年 | 957篇 |
2008年 | 1919篇 |
2007年 | 1895篇 |
2006年 | 1775篇 |
2005年 | 1633篇 |
2004年 | 1534篇 |
2003年 | 1432篇 |
2002年 | 1341篇 |
2001年 | 952篇 |
2000年 | 1020篇 |
1999年 | 540篇 |
1998年 | 281篇 |
1997年 | 218篇 |
1996年 | 244篇 |
1995年 | 229篇 |
1994年 | 191篇 |
1993年 | 195篇 |
1992年 | 207篇 |
1991年 | 187篇 |
1990年 | 203篇 |
1989年 | 174篇 |
1988年 | 172篇 |
1987年 | 163篇 |
1986年 | 153篇 |
1985年 | 204篇 |
1984年 | 199篇 |
1983年 | 163篇 |
1982年 | 200篇 |
1981年 | 201篇 |
1980年 | 141篇 |
1979年 | 182篇 |
1978年 | 152篇 |
1977年 | 121篇 |
1976年 | 118篇 |
1975年 | 111篇 |
1974年 | 128篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Ms Maarit Laine Ms Maria Aromaa Dr Pasi Virta Tuomas Lönnberg Dr Päivi Poijärvi-Virta Dr Harri Lönnberg 《Nucleosides, nucleotides & nucleic acids》2013,32(7-8):609-618
{2-Deoxy-3-O-[2-cyanoethoxy(diisopropylamino)phosphino]-5-O-(4,4′-dimethoxytrityl)-α-D- erythro-pentofuranosyl}-N-{2-[4,7,10-tris(2,2,2-trifluoroacetyl)-1,4,7,10-tetraazacyclododecan-1- yl]ethyl}acetamide (1) was prepared and incorporated into a 2′-O-methyl oligoribonucleotide. The hybridization of this oligonucleotide with complementary 2′-O-methyl oligoribonucleotides incorporating one to five uracil bases opposite to the azacrown structure was studied in the absence and presence of Zn2+. Introduction of Zn2+ moderately stabilized the duplex with U-bulged targets. 相似文献
992.
Marri Lönnberg Pertti Lehikoinen Rainer Käppi 《Nucleosides, nucleotides & nucleic acids》2013,32(1-2):397-398
Abstract Kinetics of the reactions of 6-substituted 9-(β-Q-ribofuranosyl)purines with aqueous alkalies have been studied liquid chromatographicaIly. 相似文献
993.
Satu Mikkola Mikko Oivanen Kari Neuvonen Suvi Piitari Kaisa Ketomäki Harri Lönnberg 《Nucleosides, nucleotides & nucleic acids》2013,32(10-12):1675-1692
Abstract Uridylyl-(3′,5′)-8-carboxymethylaminoadenosine has been synthesised, and its transesterification to uridine 2′,3′-cyclic phosphate in the presence and absence of Zn2+ ion has been studied. The results show that a carboxylate function in the vicinity of the phosphodiester bond accelerates the metal ion promoted cleavage but not the metal ion independent reaction. Under acidic conditions, the predominant reaction is the cleavage of the side chain, giving the 8-amino derivative. 相似文献
994.
995.
Yildiz Öner-İyidoğan Hikmet Koçak Muhammed Seyidhanoğlu Figen Gürdöl Ahmet Gülçubuk Funda Yildirim Aydin Çevik Müjdat Uysal 《Journal of physiology and biochemistry》2013,69(4):677-686
Fetuin-A is synthesized in the liver and is secreted into the bloodstream. Clinical studies suggest involvement of fetuin-A in metabolic disorders such as visceral obesity, insulin resistance, diabetes, and fatty liver. Curcumin is extracted from the rhizome Curcuma longa and has been shown to possess potent antioxidant, anticarcinogenic, anti-inflammatory, and hypoglycemic properties. In this study, we investigated the effect of curcumin treatment on serum fetuin-A levels as well as hepatic lipids and prooxidant–antioxidant status in rats fed a high-fat diet (HFD). Male Sprague–Dawley rats were divided into six groups. Group 1 was fed control diet (10 % of total calories from fat). Groups 2 and 3 were given curcumin (100 and 400 mg/kg bw/day, respectively ) by gavage for 8 weeks and were fed control diet. Group 4 was fed with HFD (60 % of total calories from fat). Groups 5 and 6 received HFD together with the two doses of curcumin, respectively. Curcumin treatment appeared to be effective in reducing liver triglycerides and serum fetuin-A levels. These findings suggest that the reduction of fetuin-A may contribute to the beneficial effects of curcumin in the pathogenesis of obesity. 相似文献
996.
Biodiversity of ecological communities has been examined widely. However, comparisons of observed species richness are limited because they fail to reveal what part of the differences are caused by natural variation in species pool size and what part is due to dark diversity – the absence of suitable species from a species pool. In other words, conventional biodiversity inventories do not convey information about how complete local plant communities are. We therefore propose the community completeness concept – a new perspective on the species pool framework. In order to ascertain community completeness, we need to estimate the extent of dark diversity, for which several methods are under development. We recommend the Community Completeness Index based on a log-ratio (or logistic) expression: ln(observed richness/dark diversity). This metric offers statistical advantages over other methods (e.g. the proportion of observed richness from the species pool). We discuss how community completeness can be related to long-term and successional community stability, landscape properties and disturbance patterns as well as to a variety of biotic interactions within and among trophic levels. The community completeness concept is related to but distinctive from the alpha-beta-gamma diversity approach and the community saturation phenomenon. The Community Completeness Index is a valuable metric for comparing biodiversity of different ecosystems for nature conservation. It can be used to measure the success of ecological restoration and vulnerability to invasion by alien species. In summary, community completeness is an interface between observed local observed species richness and dark diversity, which can be useful both in theoretical and applied biodiversity research. 相似文献
997.
Klaudia Kruppa Adél Sepsi Éva Szakács Marion S. Röder Márta Molnár-Láng 《Journal of applied genetics》2013,54(3):251-258
A spontaneous wheat-barley translocation line was previously detected in the progenies of the Mv9kr1?×?‘Igri’ wheat-barley hybrid and the translocation was identified as 5HS-7DS.7DL. Multicolor genomic in situ hybridization (mcGISH) with D and H genomic DNA probes and three-color fluorescence in situ hybridization (FISH) with repetitive DNA probes (Afa-family, pSc119.2, and pTa71) were performed to characterize the rearranged chromosome. The effect of 5HS and the deleted 7DS fragment on the morphological traits (plant height, fertility, yield, and spike characteristics) of wheat was assessed. Despite the non-compensating nature of the translocation, the plants showed good viability. The aim of the study was to physically localize SSR markers to the telomeric and subtelomeric regions of the 7DS chromosome arm. Of the 45 microsatellite markers analyzed, ten (Xbarc0184, Xwmc0506, Xgdm0130, Xgwm0735, Xgwm1258, Xgwm1123, Xgwm1250, Xgwm1055, Xgwm1220, and Xgwm0635) failed to amplify any 7DS-specific fragments, signaling the elimination of a short chromosome segment in the telomeric region. The breakpoint of the 5HS-7DS.7DL translocation appeared to be more distal than that of reported deletion lines, which provides a new physical landmark for future deletion mapping studies. 相似文献
998.
Laçine Aksoy Erdi Kolay Yasin Ağılönü Zeyneb Aslan Mustafa Kargıoğlu 《Saudi Journal of Biological Sciences》2013,20(3):235-239
Thermopsis turcica, endemic to Turkey, is in danger of extinction. Studies on this species are very few due to the fact that it was only discovered in 1983 and grows in a small circumscribed area in Turkey. In this study, free radical scavenging activity, total phenolic content, total oxidant status (TOS), and total antioxidant status (TAS) of methanol (TTM) and acetone (TTA) extracts of T. turcica were measured spectroscopically. Free radical scavenging activity was determined according to the elimination of DPPH radicals and total phenol content was determined by the Folin–Ciocalteu reaction. Total oxidant status (TOS) and total antioxidant status (TAS) were measured with commercially available kits. Methanol and acetone extracts of T. turcica were found to have a specific radical scavenging effect. This effect was found to be related to the total phenolic content of the extracts. Since the TTA had a higher phenolic content than the methanol extract, it had a stronger radical scavenging effect. In addition, the total antioxidant capacity of the methanol extract was observed to be higher than that of its acetone counterpart. As a result, due to its antioxidative properties, T. turcica is thought to be a natural source of antioxidants. 相似文献
999.
Ji?í ?míd Ji?í Moravec Luká? Kratochvíl Václav Gvo?dík Abdul Karim Nasher Salem M. Busais Thomas Wilms Mohammed Y. Shobrak Salvador Carranza 《ZooKeys》2013,(355):79-107
A recent molecular phylogeny of the Arid clade of the genus Hemidactylus revealed that the recently described H. saba and two unnamed Hemidactylus species from Sinai, Saudi Arabia and Yemen form a well-supported monophyletic group within the Arabian radiation of the genus. The name ‘Hemidactylus saba species group’ is suggested for this clade. According to the results of morphological comparisons and the molecular analyses using two mitochondrial (12S and cytb) and four nuclear (cmos, mc1r, rag1, rag2) genes, the name Hemidactylus granosus Heyden, 1827 is resurrected from the synonymy of H. turcicus for the Sinai and Saudi Arabian species. The third species of this group from Yemen is described formally as a new species H. ulii
sp. n. The phylogenetic relationships of the members of ‘Hemidactylus saba species group’ are evaluated and the distribution and ecology of individual species are discussed. 相似文献
1000.
Antonio Mu?oz-Mérida Juan José González-Plaza Andrés Ca?ada Ana María Blanco Maria del Carmen García-López José Manuel Rodríguez Laia Pedrola M. Dolores Sicardo M. Luisa Hernández Raúl De la Rosa Angjelina Belaj Mayte Gil-Borja Francisco Luque José Manuel Martínez-Rivas David G. Pisano Oswaldo Trelles Victoriano Valpuesta Carmen R. Beuzón 《DNA research》2013,20(1):93-108
Olive breeding programmes are focused on selecting for traits as short juvenile period, plant architecture suited for mechanical harvest, or oil characteristics, including fatty acid composition, phenolic, and volatile compounds to suit new markets. Understanding the molecular basis of these characteristics and improving the efficiency of such breeding programmes require the development of genomic information and tools. However, despite its economic relevance, genomic information on olive or closely related species is still scarce. We have applied Sanger and 454 pyrosequencing technologies to generate close to 2 million reads from 12 cDNA libraries obtained from the Picual, Arbequina, and Lechin de Sevilla cultivars and seedlings from a segregating progeny of a Picual × Arbequina cross. The libraries include fruit mesocarp and seeds at three relevant developmental stages, young stems and leaves, active juvenile and adult buds as well as dormant buds, and juvenile and adult roots. The reads were assembled by library or tissue and then assembled together into 81 020 unigenes with an average size of 496 bases. Here, we report their assembly and their functional annotation. 相似文献