全文获取类型
收费全文 | 2782篇 |
免费 | 273篇 |
国内免费 | 1篇 |
出版年
2023年 | 16篇 |
2022年 | 23篇 |
2021年 | 42篇 |
2020年 | 40篇 |
2019年 | 47篇 |
2018年 | 48篇 |
2017年 | 48篇 |
2016年 | 67篇 |
2015年 | 138篇 |
2014年 | 138篇 |
2013年 | 161篇 |
2012年 | 246篇 |
2011年 | 231篇 |
2010年 | 140篇 |
2009年 | 132篇 |
2008年 | 194篇 |
2007年 | 171篇 |
2006年 | 161篇 |
2005年 | 168篇 |
2004年 | 159篇 |
2003年 | 146篇 |
2002年 | 145篇 |
2001年 | 28篇 |
2000年 | 18篇 |
1999年 | 25篇 |
1998年 | 36篇 |
1997年 | 19篇 |
1996年 | 18篇 |
1995年 | 30篇 |
1994年 | 13篇 |
1993年 | 21篇 |
1992年 | 19篇 |
1991年 | 17篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1974年 | 5篇 |
1969年 | 5篇 |
1963年 | 2篇 |
1962年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有3056条查询结果,搜索用时 46 毫秒
71.
Trotz intensiver Bemühungen im Bereich des Pflanzenschutzes sind weltweit erhebliche Verluste im Bereich pflanzlicher Erntegüter zu verzeichnen. Rund ein Drittel der Verluste werden mikrobiellen Schaderregern, also Pilzen, Bakterien und Viren, zugeschrieben. Besonders schwierig ist der Tatsache zu begegnen, dass Pilze gegenüber spezifisch wirkenden Fungiziden Insensitivitäten bzw. Resistenzen entwickeln. Aus diesem Grunde muss über geeignete Strategien beim Fungizideinsatz, beim ‘Disease management’ und bei der Suche nach neuen, hochwirksamen Fungiziden nachgedacht werden. Der Erfolg bei der Suche nach neuen Fungiziden wird stark davon abhängen, ob neue Zielmoleküle für potentielle Fungizide entdeckt werden können. Dabei können moderne molekulargenetische Techniken von großem Nutzen sein. 相似文献
72.
Maud Martin Ilse Geudens Jonathan Bruyr Michael Potente Anouk Bleuart Marielle Lebrun Nicolas Simonis Christophe Deroanne Jean‐Claude Twizere Philippe Soubeyran Paul Peixoto Denis Mottet Veerle Janssens Wolf‐Karsten Hofmann Filip Claes Peter Carmeliet Richard Kettmann Holger Gerhardt Franck Dequiedt 《The EMBO journal》2013,32(18):2491-2503
73.
Kathleen B?rner Dominik Niopek Gabriella Cotugno Michaela Kaldenbach Teresa Pankert Joschka Willemsen Xian Zhang Nina Schürmann Stefan Mockenhaupt Andrius Serva Marie-Sophie Hiet Ellen Wiedtke Mirco Castoldi Vytaute Starkuviene Holger Erfle Daniel F. Gilbert Ralf Bartenschlager Michael Boutros Marco Binder Konrad Streetz Hans-Georg Kr?usslich Dirk Grimm 《Nucleic acids research》2013,41(21):e199
As the only mammalian Argonaute protein capable of directly cleaving mRNAs in a small RNA-guided manner, Argonaute-2 (Ago2) is a keyplayer in RNA interference (RNAi) silencing via small interfering (si) or short hairpin (sh) RNAs. It is also a rate-limiting factor whose saturation by si/shRNAs limits RNAi efficiency and causes numerous adverse side effects. Here, we report a set of versatile tools and widely applicable strategies for transient or stable Ago2 co-expression, which overcome these concerns. Specifically, we engineered plasmids and viral vectors to co-encode a codon-optimized human Ago2 cDNA along with custom shRNAs. Furthermore, we stably integrated this Ago2 cDNA into a panel of standard human cell lines via plasmid transfection or lentiviral transduction. Using various endo- or exogenous targets, we demonstrate the potential of all three strategies to boost mRNA silencing efficiencies in cell culture by up to 10-fold, and to facilitate combinatorial knockdowns. Importantly, these robust improvements were reflected by augmented RNAi phenotypes and accompanied by reduced off-targeting effects. We moreover show that Ago2/shRNA-co-encoding vectors can enhance and prolong transgene silencing in livers of adult mice, while concurrently alleviating hepatotoxicity. Our customizable reagents and avenues should broadly improve future in vitro and in vivo RNAi experiments in mammalian systems. 相似文献
74.
Histamine is a biogenic amine that plays an essential role in controlling many physiological functions, both in the central nervous system (CNS) and the peripheral nervous system (PNS). Most of these physiological effects are mediated through interactions with four histamine receptor subtypes, all of which are members of the larger family of rhodopsin-like class A G-protein coupled receptors (GPCRs) (Leurs et al., 2011; Lim et al., 2009). Here, we focus on the genetic variations and polymorphisms localized on the genes encoding for human histamine receptors where it provides an up to date collection of all polymorphisms found on genes encoding the histamine receptor subtypes and their association to diseases. 相似文献
75.
Eric Allan Wolfgang W. Weisser Markus Fischer Ernst-Detlef Schulze Alexandra Weigelt Christiane Roscher Jussi Baade Romain L. Barnard Holger Beßler Nina Buchmann Anne Ebeling Nico Eisenhauer Christof Engels Alexander J. F. Fergus Gerd Gleixner Marlén Gubsch Stefan Halle Alexandra M. Klein Ilona Kertscher Annely Kuu Markus Lange Xavier Le Roux Sebastian T. Meyer Varvara D. Migunova Alexandru Milcu Pascal A. Niklaus Yvonne Oelmann Esther Pašalić Jana S. Petermann Franck Poly Tanja Rottstock Alexander C. W. Sabais Christoph Scherber Michael Scherer-Lorenzen Stefan Scheu Sibylle Steinbeiss Guido Schwichtenberg Vicky Temperton Teja Tscharntke Winfried Voigt Wolfgang Wilcke Christian Wirth Bernhard Schmid 《Oecologia》2013,173(1):223-237
In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination. 相似文献
76.
77.
John Michael Hardman Wopke van der Werf Suzanne E. Blatt Jeffrey L. Franklin Richard Karsten Holger Teismann 《Experimental & applied acarology》2013,60(2):181-203
Successful biological control of mites is possible under various conditions, and identifying what are the requirements for robust control poses a challenge because interacting factors are involved. Process-based modeling can help to explore these interactions and identify under which conditions biological control is likely, and when not. Here, we present a process-based model for population interactions between the phytophagous mite, Tetranychus urticae, and its predator, Typhlodromus pyri, on apple trees. Temperature and leaf nitrogen concentration influence T. urticae rates of development and reproduction, while temperature and rate of ingestion of prey and pollen influence T. pyri rates of survival and reproduction. Predator and prey population dynamics are linked through a stage structured functional response model that accounts for spatial heterogeneity in population density throughout the trees. T. urticae biomass-days (BMD’s), which account for sizes of larvae, nymphs and adults, indicate level of mite-induced leaf damage. When BMD’s exceed 290 per leaf, there are economic losses. When BMD’s exceed 350 per leaf, T. urticae population growth is curbed and eventually the population decreases. Simulations were run to determine which conditions would lead to current year economic loss and increased risk of loss in the following year, i.e. where more T. urticae than T. pyri are present at the end of September. Risk was high with one or more of the following initial conditions: a high prey: predator ratio (10:1 or more); a low to intermediate (0.04–0.2 T. urticae per leaf) initial density; T. urticae with a higher initial proportion of adult females than T. pyri; and a delayed first detection of mites, whether in late July, or sometimes in late June, but not in early June. Warm summer weather, higher leaf nitrogen and T. urticae immigration into trees were also risk factors. Causes for these patterns based on biological characteristics of T. urticae and T. pyri are discussed, as are counter measures which can be taken to reduce risk. 相似文献
78.
79.
Jacob Glenting Hans Christian Beck Astrid Vrang Holger Riemann Peter Ravn Anne Maria Hansen Martin Antonsson Siv Ahrné Hans Israelsen Søren Madsen 《Microbiological research》2013,168(5):245-253
An important criterion for the selection of a probiotic bacterial strain is its ability to adhere to the mucosal surface. Adhesion is usually mediated by proteins or other components located on the outer cell surface of the bacterium. In the present study we characterized the adhesive properties of two classical intracellular enzymes glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and enolase (ENO) isolated from the outer cell surface of the probiotic bacterium Lactobacillus plantarum 299v. None of the genes encoded signal peptides or cell surface anchoring motifs that could explain their extracellular location on the bacterial surface. The presence of the glycolytic enzymes on the outer surface was verified by western blotting using polyclonal antibodies raised against the specific enzymes. GAPDH and ENO showed a highly specific binding to plasminogen and fibronectin whereas GAPDH but not ENO showed weak binding to mucin. Furthermore, a pH dependent and specific binding of GAPDH and ENO to intestinal epithelial Caco-2 cells at pH 5 but not at pH 7 was demonstrated. The results showed that these glycolytic enzymes could play a role in the adhesion of the probiotic bacterium L. plantarum 299v to the gastrointestinal tract of the host. Finally, a number of probiotic as well non-probiotic Lactobacillus strains were analyzed for the presence of GAPDH and ENO on the outer surface, but no correlation between the extracellular location of these enzymes and the probiotic status of the applied strains was demonstrated. 相似文献
80.
María M. Benito Holger Schielzeth Jacob González‐Solís Peter H. Becker 《Journal of avian biology》2013,44(2):179-188
Adaptive sex allocation has frequently been studied in sexually size dimorphic species, but far less is known about patterns of sex allocation in species without pronounced sexual size dimorphism. Parental optimal investment can be predicted under circumstances in which sons and daughters differ in costs and/or fitness returns. In common terns Sterna hirundo, previous studies suggest that sons are the more costly sex to produce and rear. We investigated whether hatching and fledging sex ratio and sex‐specific chick mortality correlated with the ecological environment (laying date, clutch size, hatching order and year quality) and parental traits (condition, arrival date, experience and breeding success), over seven consecutive years. Population‐wide sex ratios and sex‐specific mortality did not differ from parity, but clutch size, mass of the father, maternal breeding experience and to some extent year quality correlated with hatching sex ratio. The proportion of sons tended to increase in productive years and when the father was heavier, suggesting the possibility that females invest more in sons when the environmental and the partner conditions are good. The proportion of daughters increased with clutch size and maternal breeding experience, suggesting a decline in breeding performance or a resources balance solved by producing more of the cheaper sex. No clear patterns of sex‐specific mortality were found, neither global nor related to parental traits. Our results suggest lines for future studies on adaptive sex allocation in sexually nearly monomorphic species, where adjustment of sex ratio related to parental factors and differential allocation between the offspring may also occur. 相似文献