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91.
Many woody plant species in fire disturbed communities survive disturbance events by resprouting. The resprouting life history
is predicted to be costly to plants as resources are diverted into storage for post-fire regrowth rather than allocated to
current growth, and resprouting species typically grow more slowly than seeder species (species that do not resprout after
disturbance events). Differences in allocation to current growth are also predicted to make resprouter species poorer competitors
compared to seeder species. We tested the predictions that the evolution of a resprouter life history is associated with slow
growth, increased allocation to storage, and low competitive ability in woody plant seedlings. We grew eight phylogenetically
independent pairs of seeder and resprouter species in competition and no competition treatments in a field experiment near
Sydney, Australia. The presence of competitors reduced plant growth rates across taxa and fire response life histories. However,
relative to seeder species, resprouter species were not slower growing, they did not allocate more resources to storage, and
they did not have lower competitive abilities. We propose that differences in resource allocation to storage are not responsible
for differences in growth rate and competitive ability. Rather, growth rate and competitive ability in seedlings are associated
with key aspects of plant life history such as life-span and body size at maturity. These traits that are sometimes, but not
always, related to fire response life histories. 相似文献
92.
Aline Gomez Maqueo Chew Niels-Ulrik Frigaard Donald A. Bryant 《Photosynthesis research》2009,101(1):21-34
The first committed step in the biosynthesis of (bacterio-)chlorophyll is the insertion of Mg2+ into protoporphyrin IX by Mg-chelatase. In all known (B)Chl-synthesizing organisms, Mg-chelatase is encoded by three genes
that are homologous to bchH, bchD, and bchI of Rhodobacter spp. The genomes of all sequenced strains of green sulfur bacteria (Chlorobi) encode multiple bchH paralogs, and in the genome of Chlorobaculum tepidum, there are three bchH paralogs, denoted CT1295 (bchT), CT1955 (bchS), and CT1957 (bchH). Cba. tepidum mutants lacking one or two of these paralogs were constructed and characterized. All of the mutants lacking only one of these
BchH homologs, as well as bchS bchT and bchH bchT double mutants, which can only produce BchH or BchS, respectively, were viable. However, attempts to construct a bchH
bchS double mutant, in which only BchT was functional, were consistently unsuccessful. This result suggested that BchT alone is
unable to support the minimal (B)Chl synthesis requirements of cells required for viability. The pigment compositions of the
various mutant strains varied significantly. The BChl c content of the bchS mutant was only ~10% of that of the wild type, and this mutant excreted large amounts of protoporphyrin IX into the growth
medium. The observed differences in BChl c production of the mutant strains were consistent with the hypothesis that the three BchH homologs function in end product
regulation and/or substrate channeling of intermediates in the BChl c biosynthetic pathway.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
93.
Catalytic cracking of crude palm oil (CPO) and used palm oil (UPO) were studied in a transport riser reactor for the production of biofuels at a reaction temperature of 450 °C, with residence time of 20 s and catalyst-to-oil ratio (CTO) of 5 g g?1. The effect of HZSM-5 (differrent Si/Al ratios), beta zeolite, SBA-15 and AlSBA-15 were studied as physically mixed additives with cracking catalyst Rare earth-Y (REY). REY catalyst alone gave 75.8 wt% conversion with 34.5 wt% of gasoline fraction yield using CPO, whereas with UPO, the conversion was 70.9 wt% with gasoline fraction yield of 33.0 wt%. HZSM-5, beta zeolite, SBA-15 and AlSBA-15 as additives with REY increased the conversion and the yield of organic liquid product. The transport riser reactor can be used for the continuous production of biofuels from cracking of CPO and UPO over REY catalyst. 相似文献
94.
Matthew K. Chew 《Journal of the history of biology》2009,42(2):231-266
Dispersal of biota by humans is a hallmark of civilization, but the results are often unforeseen and sometimes costly. Like
kudzu vine in the American South, some examples become the stuff of regional folklore. In recent decades, “invasion biology,”
conservation-motivated scientists and their allies have focused largely on the most negative outcomes and often promoted the
perception that introduced species are monsters. However, cases of monstering by scientists preceded the rise of popular environmentalism.
The story of tamarisk (Tamarix spp.), flowering trees and shrubs imported to New England sometime before 1818, provides an example of scientific “monstering”
and shows how slaying the monster, rather than allaying its impacts, became a goal in itself. Tamarisks’ drought and salt
tolerance suggested usefulness for both coastal and inland erosion control, and politicians as well as academic and agency
scientists promoted planting them in the southern Great Plains and Southwest. But when erosion control efforts in Arizona,
New Mexico and Texas became entangled with water shortages, economic development during the Depression and copper mining for
national defense during World War Two, federal hydrologists moved quickly to recast tamarisks as water-wasting foreign monsters.
Demonstrating significant water salvage was difficult and became subsidiary to focusing on ways to eradicate the plants, and
a federal interagency effort devoted specifically to the latter purpose was organized and continued until it, in turn, conflicted
with regional environmental concerns in the late 1960s. 相似文献
95.
96.
Background
Previous studies have demonstrated that knockout or inhibition of Platelet/Endothelial Cell Adhesion Molecule (PECAM, CD31) in a number of murine strains results in impaired inflammatory responses, but that no such phenotype is seen in the C57BL/6 (B6) murine background.Methodology/Principal Findings
We have undertaken a quantitative trait locus (QTL) mapping effort between FVB/n (FVB) and B6 mice deficient for PECAM to identify the gene or genes responsible for this unique feature of B6 mice. We have identified a locus on murine chromosome 2 at approximately 35.8 Mb that is strongly associated (LOD score = 9.0) with inflammatory responses in the absence of PECAM.Conclusions/Significance
These data potentiate further study of the diapedesis machinery, as well as potential identification of new components of this machinery. As such, this study is an important step to better understanding the processes of inflammation. 相似文献97.
Decision making often entails longshot risks involving a small chance of receiving a substantial outcome. People tend to be risk preferring (averse) when facing longshot risks involving significant gains (losses). This differentiation towards longshot risks underpins the markets for lottery as well as for insurance. Both lottery and insurance have emerged since ancient times and continue to play a useful role in the modern economy. In this study, we observe subjects'' incentivized choices in a controlled laboratory setting, and investigate their association with a widely studied, promoter-region repeat functional polymorphism in monoamine oxidase A gene (MAOA). We find that subjects with the high activity (4-repeat) allele are characterized by a preference for the longshot lottery and also less insurance purchasing than subjects with the low activity (3-repeat) allele. This is the first result to link attitude towards longshot risks to a specific gene. It complements recent findings on the neurobiological basis of economic risk taking. 相似文献
98.
Emily Catherine Hodkinson Keith Morrice William Loan Jacob Nicholas EngWooi Chew 《Indian pacing and electrophysiology journal》2014,14(1):37-43
It is established that cardiac resynchronisation therapy (CRT) reduces mortality and hospitalisation and improves functional class in patients with NYHA class 3-4 heart failure, an ejection fraction of ≤ 35% and a QRS duration of ≥ 120ms. Recent updates in the American guidelines have expanded the demographic of patients in whom CRT may be appropriate. Here we present two cases of complex CRT; one with a conventional indication but occluded central veins and the second with a novel indication for CRT post cardiac transplant. 相似文献
99.
Yin Hoon Chew Robert W. Smith Harriet J. Jones Daniel D. Seaton Ramon Grima Karen J. Halliday 《The Plant cell》2014,26(1):5-20
Plants respond to changes in the environment by triggering a suite of regulatory networks that control and synchronize molecular signaling in different tissues, organs, and the whole plant. Molecular studies through genetic and environmental perturbations, particularly in the model plant Arabidopsis thaliana, have revealed many of the mechanisms by which these responses are actuated. In recent years, mathematical modeling has become a complementary tool to the experimental approach that has furthered our understanding of biological mechanisms. In this review, we present modeling examples encompassing a range of different biological processes, in particular those regulated by light. Current issues and future directions in the modeling of plant systems are discussed. 相似文献
100.