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991.
A particularly vexing phenomenon within invasion ecology is the occurrence of spontaneous collapses within seemingly well-established exotic populations. Here, we assess the frequency of collapses among 68 exotic bird populations established in Hawaii, Puerto Rico, Los Angeles and Miami. Following other published definitions, we define a ‘collapse’ as a decline in abundance of ≥90 % within ≤10 years that lasts for at least 3 years. We show that 44 of the 68 exotic bird populations have exhibited declines at some point within their time series. Sixteen of the populations declined sufficiently to be defined as collapsed. It took on average 3.8 ± 1.8 years for populations to decline into a collapsed state, and this state persisted on average for 7.1 ± 6.3 years across (collapsed) populations. We compared the severity and duration of declines across all 44 declining populations according to taxonomic Order and geographic region. Neither variable explained substantial variation in the metrics of collapse. Our results indicate that severe, rapid, and persistent population declines may be common among exotic populations. We suggest that incorporating the probability and persistence of collapses into management decisions can inform efforts to enact control or eradication measures. We also suggest that applying our approach to other taxa and locations is crucial for improving our understanding of when and where collapses are likely to occur. 相似文献
992.
Sébastien Givry Vincent Prevot Francis Duchiron 《World journal of microbiology & biotechnology》2008,24(6):745-752
Consumption of hexoses/pentoses and production of lactic acid by Lactobacillus bifermentans were investigated in optimized culture medium and hemicellulosic hydrolyzates. The hydrolyzate used had the following composition
(expressed in gL−1): xylose 50 ± 5 gL−1; glucose 18 ± 3 gL−1; arabinose 29 ± 5 gL−1. The immobilization experiments were conducted with microbial cells entrapped in calcium alginate beads. The results indicate
that maximum concentrations of lactic acid were produced after 54 h of fermentation. All glucose and arabinose in wheat bran
hydrolyzate were consumed during fermentation. Only xylose was not completely consumed. The substrate consumption rate was
3.2 gh−1, 1.9 gh−1, 1.6 gh−1 respectively for glucose, arabinose, and xylose. The optimized culture condition gave a lactic acid concentration and metabolic
yield of 62.77 gL−1 and 0.83 gg−1. These parameters improved to 41.3 gL−1 and 0.47 gg−1 respectively, when cell free was used. 相似文献
993.
Our understanding of the controls and magnitudes of regional CO2 exchanges in the Arctic are limited by uncertainties due to spatial heterogeneity in vegetation across the landscape and
temporal variation in environmental conditions through the seasons. We measured daytime net ecosystem CO2 exchange and each of its component fluxes in the three major tundra ecosystem-types that typically occur along natural moisture
gradients in the Canadian Low Arctic biweekly during the full snow-free season of 2004. In addition, we used a plant-removal
treatment to compare the contribution of bulk soil organic matter to total respiratory CO2 loss among these ecosystems. Net CO2 exchange rates varied strongly, but not consistently, among ecosystems in the spring and summer phases as a result of ecosystem-specific and differing responses of gross photosynthesis
and respiration to temporal variation in environmental conditions. Overall, net carbon gain was largest in the wet sedge ecosystem
and smallest in the dry heath. Our measures of CO2 flux variation within each ecosystem were frequently most closely correlated with air or soil temperatures during each seasonal
phase. Nevertheless, a particularly large rainfall event in early August rapidly decreased respiration rates and stimulated
gross photosynthetic rates, resulting in peak rates of net carbon gain in all ecosystems. Finally, the bulk soil carbon contribution
to total respiration was relatively high in the birch hummock ecosystem. Together, these results demonstrate that the relative
influences of moisture and temperature as primary controls on daytime net ecosystem CO2 exchange and its component fluxes differ in fundamental ways between the landscape and ecosystem scales. Furthermore, they
strongly suggest that carbon cycling responses to environmental change are likely to be highly ecosystem-specific, and thus
to vary substantially across the low arctic landscape.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
994.
B-Cell activating factor (BAFF) is critical for B cell survival and maturation; excessive expression of it corrupts B-cell
tolerance and may lead to autoimmunity. The gene, scFv-Fc, coding for the antibody of BAFF was inserted into the eukaryotic
expression vector, pPICZαA, and transformed into Pichia pastoris. A high-level expression strain was obtained using a ‘yeastern blotting’ method. The scFv-Fc antibody was purified and 56 mg
was obtained from 1 l of culture supernatant. It retained high binding activity to both soluble BAFF and membrane-bound BAFF. 相似文献
995.
da Silva SM Venceslau SS Fernandes CL Valente FM Pereira IA 《Antonie van Leeuwenhoek》2008,93(4):381-390
The gram-negative anaerobic gut bacterium Bilophila wadsworthia is the third most common isolate in perforated and gangrenous appendicitis, being also found in a variety of other infections.
This organism performs a unique kind of anaerobic respiration in which taurine, a major organic solute in mammals, is used
as a source of sulphite that serves as terminal acceptor for the electron transport chain. We show here that molecular hydrogen,
one of the major products of fermentative bacteria in the colon, is an excellent growth substrate for B. wadsworthia. We have quantified the enzymatic activities associated with the oxidation of H2, formate and pyruvate for cells obtained in different growth conditions. The cell extracts present high levels of hydrogenase
activity, and up to five different hydrogenases can be expressed by this organism. One of the hydrogenases appears to be constitutive,
whereas the others show differential expression in different growth conditions. Two of the hydrogenases are soluble and are
recognised by antibodies against a [FeFe] hydrogenase of a sulphate reducing bacterium. One of these hydrogenases is specifically
induced during fermentative growth on pyruvate. Another two hydrogenases are membrane-bound and show increased expression
in cells grown with hydrogen. Further work should be carried out to reveal whether oxidation of hydrogen contributes to the
virulence of B. wadsworthia. 相似文献
996.
In ectotherms, lower temperatures at high latitudes would theoretically reduce annual growth rates of individuals. If slower
growth and resulting smaller body size reduce fitness, individuals at high latitudes may evolve compensatory growth. This
study compares individual growth rates among and within 12 latitudinal populations of the medaka (Oryzias latipes). Growth rates during juvenile stage were measured in a common, temperature-controlled (28°C) environment. The results revealed
that juvenile growth rates differed significantly among the populations. Growth rates were, moreover, significantly correlated
with latitudes of source populations, such that higher-latitude individuals grew faster. Significant variation in growth rates
among full-sib families within populations was also demonstrated. The results strongly suggest that higher-latitude O. latipes have acquired a greater capacity for growth as an adaptation to shorter growing seasons (which would reduce annual growth
rates), thus refuting probability processes, i.e., genetic drift, founder, or bottleneck effects, as a cause of the among-population
variation. 相似文献
997.
Salmaso M Malacarne G Troggio M Faes G Stefanini M Grando MS Velasco R 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2008,116(8):1129-1143
Grapevine molecular maps based on microsatellites, AFLP and RAPD markers are now available. SSRs are essential to allow cross-talks
between maps, thus upgrading any growing grapevine maps. In this work, single nucleotide polymorphisms (SNPs) were developed
from coding sequences and from unique BAC-end sequences, and nested in a SSR framework map of grapevine. Genes participating
to flavonoids metabolism and defence, and signal transduction pathways related genes were also considered. Primer pairs for
351 loci were developed from ESTs present on public databases and screened for polymorphism in the “Merzling” (a complex genotype
Freiburg 993–60 derived from multiple crosses also involving wild Vitis species) × Vitis vinifera (cv. Teroldego) cross population. In total 138 SNPs, 108 SSR markers and a phenotypic trait (berry colour) were mapped in
19 major linkage groups of the consensus map. In specific cases, ESTs with putatively related functions mapped near QTLs previously
identified for resistance and berry ripening. Genes related to anthocyanin metabolism mapped in different linkage groups.
A myb gene, which has been correlated with anthocyanin biosynthesis, cosegregated with berry colour on linkage group 2. The possibility
of associating candidate genes to known position of QTL is discussed for this plant.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Marzia Salmaso and Giulia Malacarne contributed equally to the present work. 相似文献
998.
Alcoholic liver disease (ALD) is one of the most common diseases in modern society. A large number of studies are in progress
aiming to identify natural substances that would be effective in reducing the severity of ALD. Although there are currently
a number of drugs on the market, their long-term use can have numerous side effects. Hemidesmus indicus is an indigenous Ayurvedic medicinal plant used in soft drinks in India. In this study, we examined the effects of its ethanolic
root extract on experimental liver damage in order to evaluate its hepatoprotective effects against hepatotoxicity induced
in rats by ethanol at a dosage of 5 g/kg body weight for 60 days. The H. indicus root extract was given at a dose of 500 mg/kg body weight for the last 30 days of the experiment. The animals were monitored
for food intake and weight gain. The liver was analysed for the degree of lipid peroxidation using thiobarbituric acid reactive
substances (TBARS) and antioxidant status using the activities of glutathione-depedendant enzymes. The degree of liver damage
was analysed using serum marker enzyme activities, the total protein, albumin, globulin, ceruloplasmin and liver glycogen
contents, and the A/G ratio. The Fourier transform infrared spectra (FT-IR) of the liver tissues were recorded in the region
of 4000–400 cm−1. The ethanol-fed rats showed significantly elevated liver marker enzyme activities, lipid peroxidation levels and reduced
antioxidant levels as compared to the control rats. Oral administration of H. indicus for the latter 30 days resulted in an increased food intake and weight gain, decreased TBARS levels, near normal levels of
glutathione-dependent enzymes, increased total protein, albumin, globulin and liver glycogen contents, an increased A/G ratio,
and decreased liver marker enzyme activities and ceruloplasmin levels. The relative intensity of the liver FT-IR bands for
the experimental groups were found to be altered significantly (p < 0.05) compared to the control samples. For the group that
had H. indicus co-administered with ethanol, the intensity of the bands was near normal. Moreover, the results of the FT-IR study correlated
with our biochemical results. 相似文献
999.
Applied nucleation is a straightforward,cost‐effective forest restoration approach: reply to Ramírez‐Soto et al. (2018) 下载免费PDF全文
We agree with Ramírez‐Soto and colleagues that applied nucleation can be an effective approach for tropical forest restoration both in lowland and higher elevation tropical forests. We also contend that it is cheaper than standard plantation‐style plantings and is straightforward to train personnel to implement this approach. 相似文献
1000.
Matheus O. Freitas Marilia Previero Carolina V. Minte-Vera Henry L. Spach Ronaldo B. Francini-Filho Rodrigo L. Moura 《Environmental Biology of Fishes》2018,101(1):79-94
The reproductive biology of Epinephelus morio (red grouper) and Mycteroperca bonaci (black grouper) were evaluated based on 533 specimens collected from artisanal fisheries landings in the Abrolhos Bank, Brazil, between May 2005 and September 2012. Sex ratio for the black grouper was 1:14 (n = 155 females and 11 males; 26.1–147 cm TL) and 1:10 for the red grouper (n = 334 females and 33 males; 15.0–96.0 cm TL). For both species, highest values of the gonadosomatic index (GSI) for females were recorded between July and October, indicating spawning during the austral winter. The length at first maturity (L50) for females was estimated at 62.0 and 47.0 cm TL for the black and red grouper, respectively. Batch fecundity based on TL and TW ranged from 2 to 15.4?106 and 1.5 to 13.7?106 for the black and red grouper, respectively. Interviews with experienced fishers revealed that spawning seasons of both groupers are largely unrecognized. Results demonstrate a positive relationship between GSI peaks, lower temperatures and stronger winds. The information provided herein may help decision-making regarding fisheries management and conservation for E. morio and M. bonaci at various levels of governance in the Abrolhos Bank, the region with the largest and richest coralline reefs in the South Atlantic. 相似文献