全文获取类型
收费全文 | 4067篇 |
免费 | 381篇 |
国内免费 | 3篇 |
专业分类
4451篇 |
出版年
2023年 | 30篇 |
2022年 | 60篇 |
2021年 | 131篇 |
2020年 | 79篇 |
2019年 | 92篇 |
2018年 | 115篇 |
2017年 | 106篇 |
2016年 | 170篇 |
2015年 | 309篇 |
2014年 | 276篇 |
2013年 | 272篇 |
2012年 | 446篇 |
2011年 | 361篇 |
2010年 | 231篇 |
2009年 | 187篇 |
2008年 | 268篇 |
2007年 | 240篇 |
2006年 | 198篇 |
2005年 | 189篇 |
2004年 | 135篇 |
2003年 | 129篇 |
2002年 | 110篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 13篇 |
1998年 | 27篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1988年 | 14篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1976年 | 4篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1972年 | 5篇 |
1969年 | 4篇 |
1968年 | 4篇 |
排序方式: 共有4451条查询结果,搜索用时 15 毫秒
161.
Meyer VS Kastenmuller W Gasteiger G Franz-Wachtel M Lamkemeyer T Rammensee HG Stevanovic S Sigurdardottir D Drexler I 《Journal of immunology (Baltimore, Md. : 1950)》2008,181(9):6371-6383
Viral peptides are presented by HLA class I on infected cells to activate CD8(+) T cells. Several immunogenic peptides have been identified indirectly by epitope prediction and screening of T cell responses to poxviral vectors, including modified vaccinia virus Ankara (MVA) currently being tested as recombinant or smallpox vaccines. However, for the development of optimal vaccination and immunomonitoring strategies, it is essential to characterize the actual viral HLA ligand repertoire of infected cells. We used an innovative approach to identify naturally processed MVA HLA ligands by differential HPLC-coupled mass spectrometry. We describe 12 viral peptides presented by HLA-A*0201 and 3 by HLA-B*0702. All HLA-A*0201 ligands participated in the memory response of MVA-immune donors, and several were immunogenic in Dryvax vaccinees. Eight epitopes were novel. Viral HLA ligand presentation and viral protein abundance did not correlate. All ligands were expressed early during the viral life cycle, and a pool of three of these mediated stronger protection against a lethal challenge in mice as compared with late epitopes. This highlights the reliability of the comparative mass spectrometry-based technique to identify relevant viral CD8(+) T cell epitopes for optimizing the monitoring of protective immune responses and the development of effective peptide-based vaccines. 相似文献
162.
Wenxin Liu Hans Peter Maurer Willmar L. Leiser Matthew R. Tucker Sigrid Weissmann Volker Hahn Tobias Würschum 《Bioenergy Research》2017,10(2):449-455
Triticale is a promising crop for agricultural biomass production but breeding has until now mainly focused on grain yield. Here, we evaluated the potential of marker-assisted simultaneous improvement of grain yield and biomass yield. To this end, we employed a large triticale doubled haploid population with 647 individuals derived from four families that were phenotyped for grain yield and biomass yield, as well as thousand-kernel weight, tiller density, and plant height in multi-environment field trials. Employing an association mapping approach, we identified quantitative trait loci (QTL) for all the five traits. The phenotypic correlation between grain yield and biomass yield was low, and we detected only one overlapping QTL suggesting different genetic architectures underlying both traits. Our results indicate that a marker-based selection for either grain yield or biomass yield does not adversely affect the other traits. Furthermore, an improvement of the multiplicative yield traits can to some extent also be achieved by selection for QTL identified for the component traits. Taken together, our results suggest that marker-assisted breeding can assist the establishment of dual-purpose triticale cultivars with high grain and biomass yield. 相似文献
163.
Nitrate reductase (NR) from the fungus Neurospora crassa is a complex homodimeric metallo-flavoenzyme, where each protomer contains three distinct domains; the catalytically active terminal molybdopterin cofactor, a central heme-containing domain, and an FAD domain which binds with the natural electron donor NADPH. Here, we demonstrate the catalytic voltammetry of variants of N. crassa NRs on a modified Au electrode with the electrochemically reduced forms of benzyl viologen (BV2+) and anthraquinone sulfonate (AQS?) acting as artificial electron donors. The biopolymer chitosan used to entrap NR on the electrode non-covalently and the enzyme film was both stable and highly active. Electrochemistry was conducted on two distinct forms; one lacking the FAD cofactor and the other lacking both the FAD and heme cofactors. While both enzymes showed catalytic nitrate reductase activity, removal of the heme cofactor resulted in a more significant effect on the rate of nitrate reduction. Electrochemical simulation was carried out to enable kinetic characterisation of both the NR:nitrate and NR:mediator reactions. 相似文献
164.
Tor Erik Brandrud Geert Schmidt-Stohn Kare Liimatainen Tuula Niskanen Tobias Guldberg Frøslev Karl Soop Dimitar Bojantchev Ilkka Kytövuori Thomas Stjernegaard Jeppesen Francesco Bellù Günter Saar Bernhard Oertel Tahir Ali Marco Thines Bálint Dima 《Mycological Progress》2018,17(12):1323-1354
Cortinarius is one of the most species-rich genera of mushroom-forming fungi. Based on phylogenetic and morphological evidence, Cortinarius, sect. Riederi, is introduced at sectional level (= subsect. Riederi sensu Brandrud & Melot). The taxonomy, phylogeny, ecology and distribution of not only mainly European but also including some North American taxa of this section are treated, which includes nine species and two varieties. Of these, three taxa are described as new (C. burlinghamiae, C. pallidoriederi and C. argenteolilacinus var. dovrensis). The sect. Riederi species possess morphological features similar to Phlegmacium group(s) and forms a phylogenetically isolated lineage, with no supported affinity to other phlegmacioid groups. Three taxa are known from both Europe and North America, two species are known only from North America and five only from Europe. Altogether, eight of the ten taxa are associated with conifers or northern (boreal-subalpine) deciduous trees (Betula spp.). Only two species occur in more temperate forests (Fagus forests), and no species have so far been found in thermophilous Quercus forests 相似文献
165.
Humans often behave more prosocially when being observed in person and even in response to subtle eye cues, purportedly to manage their reputation. Previous research on this phenomenon has employed the “watching eyes paradigm,” in which adults displayed greater prosocial behavior in the presence of images of eyes versus inanimate objects. However, the robustness of the effect of eyes on prosocial behavior has recently been called into question. Therefore, the first goal of the present study was to attempt to replicate this effect. Additionally, it remains unclear whether the watching-eyes effect is driven specifically by reputation management (owing to the monitoring function of the eyes) or whether any cues indexing human presence more generally also have a similar effect. To address these questions, the current study compared prosocial behavior in the presence of eyes versus inanimate objects as well as other human features. The study was conducted as a field experiment at a children’s museum. Each week, the donation signs were changed to show eyes, noses, mouths, or chairs. Total donation amount and number of patrons per week were recorded. Participants donated more when they were exposed to eyes than to inanimate objects (chairs). We thus replicated the previously reported watching-eyes effect. Moreover, more money was donated when individuals were exposed to eyes than to more general cues of human presence (nose and mouth). The current findings suggest that eyes play a special role in promoting cooperation in humans, likely by serving as cues of monitoring and thus eliciting reputation management behavior. 相似文献
166.
The effect of habitat fragmentation on the bee visitor assemblages of three Australian tropical rainforest tree species 下载免费PDF全文
Tropical forest loss and fragmentation can change bee community dynamics and potentially interrupt plant–pollinator relationships. While bee community responses to forest fragmentation have been investigated in a number of tropical regions, no studies have focused on this topic in Australia. In this study, we examine taxonomic and functional diversity of bees visiting flowers of three tree species across small and large rainforest fragments in Australian tropical landscapes. We found lower taxonomic diversity of bees visiting flowers of trees in small rainforest fragments compared with large forest fragments and show that bee species in small fragments were subsets of species in larger fragments. Bees visiting trees in small fragments also had higher mean body sizes than those in larger fragments, suggesting that small‐sized bees may be less likely to persist in small fragments. Lastly, we found reductions in the abundance of eusocial stingless bees visiting flowers in small fragments compared to large fragments. These results suggest that pollinator visits to native trees living in small tropical forest remnants may be reduced, which may in turn impact on a range of processes, potentially including forest regeneration and diversity maintenance in small forest remnants in Australian tropical countryside landscapes. 相似文献
167.
168.
Tobias Fürch Matthias Preusse Jürgen Tomasch Hajo Zech Irene Wagner-D?bler Ralf Rabus Christoph Wittmann 《BMC microbiology》2009,9(1):209
Background
In the present work the central carbon metabolism of Dinoroseobacter shibae and Phaeobacter gallaeciensis was studied at the level of metabolic fluxes. These two strains belong to the marine Roseobacter clade, a dominant bacterial group in various marine habitats, and represent surface-associated, biofilm-forming growth (P. gallaeciensis) and symbiotic growth with eukaryotic algae (D. shibae). Based on information from recently sequenced genomes, a rich repertoire of pathways has been identified in the carbon core metabolism of these organisms, but little is known about the actual contribution of the various reactions in vivo. 相似文献169.
170.
Daw-Yang Hwang Stefan Kohl Xueping Fan Asaf Vivante Stefanie Chan Gabriel C. Dworschak Julian Schulz Albertien M. van Eerde Alina C. Hilger Heon Yung Gee Tracie Pennimpede Bernhard G. Herrmann Glenn van de Hoek Kirsten Y. Renkema Christoph Schell Tobias B. Huber Heiko M. Reutter Neveen A. Soliman Natasa Stajic Radovan Bogdanovic Elijah O. Kehinde Richard P. Lifton Velibor Tasic Weining Lu Friedhelm Hildebrandt 《Human genetics》2015,134(8):905-916