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991.
Dana S. Nau George Markowsky Max A. Woodbury D. Bernard Amos 《Mathematical biosciences》1978,40(3-4):243-270
This paper presents and explores a comprehensive mathematical model for human leukocyte antigen serology, based on a mathematical formalization of the concept of specificity. This model is general enough to take into account such factors as absorption, elution, cross-reactivity, and incomplete immunization. The paper includes a presentation of the relevant immunological background and a short discussion of the underlying computational difficulty of the basic problems. Upper and lower bounds are derived for the minimal number of specificities required to explain a given set of HLA reactions, and it is shown that the numbers of antibodies and antigens involved must be no less then this minimal number of specificities. Other techniques and theorems are also presented to aid in reducing and analyzing HLA reaction matrices. 相似文献
992.
Dana R. Warren Madeleine M. Mineau Eric J. Ward Clifford E. Kraft 《Environmental Biology of Fishes》2010,88(1):51-62
Stream pH and stream habitat have both been identified as important environmental features influencing total fish biomass
in streams, but few studies have evaluated the relative influence of habitat and pH together. We measured total fish biomass,
stream habitat, and stream pH in sixteen sites from three tributary systems in the northeastern United States. The habitat
metrics included total pool area, a cover score, large wood frequency, and stream temperature. We created and compared nine
linear models relating total fish biomass in summer to stream pH and stream habitat using Akaike’s Information Criterion (AIC)
analysis. The best (most parsimonious) models included pool area and stream pH. These results and a separate comparison of
three regressions (low-flow pH, pool area, and these two metrics together versus total fish biomass) suggest that both habitat
and stream buffering capacity affect the total biomass of fish in northeastern US headwater streams. When stream pH is adequate
(low-flow pH greater than at least 5.7), physical habitat is likely to be more important, but under lower pH conditions, habitat
is likely to be less effective in accounting for the total biomass of fish in these streams. This work demonstrates the continued
effects of stream acidification in the northeastern US and more generally, it illustrates the importance of considering both
physical and chemical conditions of a stream when evaluating the factors influencing fish communities. 相似文献
993.
994.
Examination of 140 collections of Chara zeylanica from 3 southwestern states shows that a strong dichotomy exists in the collections. Some produce 4-plated antheridia while others produce 8-plated antheridia. Absolute separation of the study material is possible on the basis of plate number. In addition, 3 other characters (length/width ratio of oospores; fertility of first branchlet node; and number of distal ecorticate branchlet internodes) show strong correlation with the antheridial type. Preliminary chromosomal work indicates that a segregation at this level may also be possible. In 4-plated collections examined, n = 28; 8-plated collections are usually n = 56; however, a few 8-plated collections are n = 42. No conclusion has been reached regarding the status of the latter collections. 相似文献
995.
Yukari Maezato Tyler Johnson Samuel McCarthy Karl Dana Paul Blum 《Journal of bacteriology》2012,194(24):6856-6863
Archaea such as Metallosphaera sedula are thermophilic lithoautotrophs that occupy unusually acidic and metal-rich environments. These traits are thought to underlie their industrial importance for bioleaching of base and precious metals. In this study, a genetic approach was taken to investigate the specific relationship between metal resistance and lithoautotrophy during biotransformation of the primary copper ore, chalcopyrite (CuFeS2). In this study, a genetic system was developed for M. sedula to investigate parameters that limit bioleaching of chalcopyrite. The functional role of the M. sedula copRTA operon was demonstrated by cross-species complementation of a copper-sensitive Sulfolobus solfataricus copR mutant. Inactivation of the gene encoding the M. sedula copper efflux protein, copA, using targeted recombination compromised metal resistance and eliminated chalcopyrite bioleaching. In contrast, a spontaneous M. sedula mutant (CuR1) with elevated metal resistance transformed chalcopyrite at an accelerated rate without affecting chemoheterotrophic growth. Proteomic analysis of CuR1 identified pleiotropic changes, including altered abundance of transport proteins having AAA-ATPase motifs. Addition of the insoluble carbonate mineral witherite (BaCO3) further stimulated chalcopyrite lithotrophy, indicating that carbon was a limiting factor. Since both mineral types were actively colonized, enhanced metal leaching may arise from the cooperative exchange of energy and carbon between surface-adhered populations. Genetic approaches provide a new means of improving the efficiency of metal bioleaching by enhancing the mechanistic understanding of thermophilic lithoautotrophy. 相似文献
996.
Adi Hendler Eyal Akiva Mahakaran Sandhu Dana Goldberg Eyal Arbely Colin J Jackson Amir Aharoni 《Molecular biology and evolution》2021,38(2):545
Many enzymes that catalyze protein post-translational modifications can specifically modify multiple target proteins. However, little is known regarding the molecular basis and evolution of multispecificity in these enzymes. Here, we used a combined bioinformatics and experimental approaches to investigate the evolution of multispecificity in the sirtuin-1 (SIRT1) deacetylase. Guided by bioinformatics analysis of SIRT1 orthologs and substrates, we identified and examined important amino acid substitutions that have occurred during the evolution of sirtuins in Metazoa and Fungi. We found that mutation of human SIRT1 at these positions, based on sirtuin orthologs from Fungi, could alter its substrate specificity. These substitutions lead to reduced activity toward K382 acetylated p53 protein, which is only present in Metazoa, without affecting the high activity toward the conserved histone substrates. Results from ancestral sequence reconstruction are consistent with a model in which ancestral sirtuin proteins exhibited multispecificity, suggesting that the multispecificity of some metazoan sirtuins, such as hSIRT1, could be a relatively ancient trait. 相似文献
997.
Cloning, sequence, and transcriptional regulation of the operon encoding a putative N-acetylmannosamine-6-phosphate epimerase (nanE) and sialic acid lyase (nanA) in Clostridium perfringens. 下载免费PDF全文
Dana M. Walters Veronica L. Stirewalt Stephen B. Melville 《Journal of bacteriology》1999,181(15):4526-4532
998.
999.
Horizontal acquisition of multiple mitochondrial genes from a parasitic plant followed by gene conversion with host mitochondrial genes 总被引:1,自引:0,他引:1
Jeffrey P Mower Saša Stefanović Weilong Hao Julie S Gummow Kanika Jain Dana Ahmed Jeffrey D Palmer 《BMC biology》2010,8(1):150
Background
Horizontal gene transfer (HGT) is relatively common in plant mitochondrial genomes but the mechanisms, extent and consequences of transfer remain largely unknown. Previous results indicate that parasitic plants are often involved as either transfer donors or recipients, suggesting that direct contact between parasite and host facilitates genetic transfer among plants. 相似文献1000.
Expanding visitation to Polar regions combined with climate warming increases the potential for alien species introduction
and establishment. We quantified vascular plant propagule pressure associated with different groups of travelers to the high-Arctic
archipelago of Svalbard, and evaluated the potential of introduced seeds to germinate under the most favorable average Svalbard
soil temperature (10°C). We sampled the footwear of 259 travelers arriving by air to Svalbard during the summer of 2008, recording
1,019 seeds: a mean of 3.9 (±0.8) seeds per traveler. Assuming the seed influx is representative for the whole year, we estimate
a yearly seed load of around 270,000 by this vector alone. Seeds of 53 species were identified from 17 families, with Poaceae
having both highest diversity and number of seeds. Eight of the families identified are among those most invasive worldwide,
while the majority of the species identified were non-native to Svalbard. The number of seeds was highest on footwear that
had been used in forested and alpine areas in the 3 months prior to traveling to Svalbard, and increased with the amount of
soil affixed to footwear. In total, 26% of the collected seeds germinated under simulated Svalbard conditions. Our results
demonstrate high propagule transport through aviation to highly visited cold-climate regions and isolated islands is occurring.
Alien species establishment is expected to increase with climate change, particularly in high latitude regions, making the
need for regional management considerations a priority. 相似文献