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991.
Latitudinal Variation in Leaf and Tree Traits of the Mangrove Avicennia germinans (Avicenniaceae) in the Central Region of the Gulf of Mexico 总被引:1,自引:0,他引:1
The variation in leaf mass per area, leaf nutrients (% carbon, nitrogen and phosphorus), and the allometric relation between tree height and diameter of the black mangrove, Avicennia germinans, were explored in nine mangrove forests in similar environments along a 5° latitudinal gradient in the central region of the Gulf of Mexico, as indicated by a southward increase in temperature and precipitation. There was no correlation between leaf nitrogen or phosphorus content and latitude. Leaf mass per area and leaf carbon content were positively correlated with latitude and negatively correlated with temperature and annual rainfall, whereas asymptotic tree height and maximum diameter showed the opposite trend. Such patterns suggest a trade-off between leaf traits and tree size which may be constrained by the same environmental factors along a dry-cold to humid-warm latitudinal gradient. 相似文献
992.
Soliz J Soulage C Borter E van Patot MT Gassmann M 《American journal of physiology. Regulatory, integrative and comparative physiology》2008,295(2):R649-R658
Proteins harboring a Per-Arnt-Sim (PAS) domain are versatile and allow archaea, bacteria, and plants to sense oxygen partial pressure, as well as light intensity and redox potential. A PAS domain associated with a histidine kinase domain is found in FixL, the oxygen sensor molecule of Rhizobium species. PASKIN is the mammalian homolog of FixL, but its function is far from being understood. Using whole body plethysmography, we evaluated the ventilatory response to acute and chronic hypoxia of homozygous deficient male and female PASKIN mice (Paskin-/-). Although only slight ventilatory differences were found in males, female Paskin-/- mice increased ventilatory response to acute hypoxia. Unexpectedly, females had an impaired ability to reach ventilatory acclimatization in response to chronic hypoxia. Central control of ventilation occurs in the brain stem respiratory centers and is modulated by catecholamines via tyrosine hydroxylase (TH) activity. We observed that TH activity was altered in male and female Paskin-/- mice. Peripheral chemoreceptor effects on ventilation were evaluated by exposing animals to hyperoxia (Dejours test) and domperidone, a peripheral ventilatory stimulant drug directly affecting the carotid sinus nerve discharge. Male and female Paskin-/- had normal peripheral chemosensory (carotid bodies) responses. In summary, our observations suggest that PASKIN is involved in the central control of hypoxic ventilation, modulating ventilation in a gender-dependent manner. 相似文献
993.
Kaba NK Schultz J Law FY Lefort CT Martel-Gallegos G Kim M Waugh RE Arreola J Knauf PA 《American journal of physiology. Cell physiology》2008,295(5):C1454-C1463
Ischemia-reperfusion injury is a common pathological occurrence causing tissue damage in heart attack and stroke. Entrapment of neutrophils in the vasculature during ischemic events has been implicated in this process. In this study, we examine the effects that lactacidosis and consequent reductions in intracellular pH (pH(i)) have on surface expression of adhesion molecules on neutrophils. When human neutrophils were exposed to pH 6 lactate, there was a marked decrease in surface L-selectin (CD62L) levels, and the decrease was significantly enhanced by inclusion of Na(+)/H(+) exchanger (NHE) inhibitor 5-(N,N-hexamethylene)amiloride (HMA). Similar effects were observed when pH(i) was reduced while maintaining normal extracellular pH, by using an NH(4)Cl prepulse followed by washes and incubation in pH 7.4 buffer containing NHE inhibitors [HMA, cariporide, or 5-(N,N-dimethyl)amiloride (DMA)]. The amount of L-selectin shedding induced by different concentrations of NH(4)Cl in the prepulse correlated with the level of intracellular acidification with an apparent pK of 6.3. In contrast, beta(2)-integrin (CD11b and CD18) was only slightly upregulated in the low-pH(i) condition and was enhanced by NHE inhibition to a much lesser extent. L-selectin shedding was prevented by treating human neutrophils with inhibitors of extracellular metalloproteases (RO-31-9790 and KD-IX-73-4) or with inhibitors of intracellular signaling via p38 MAP kinase (SB-203580 and SB-239063), implying a transmembrane effect of pH(i). Taken together, these data suggest that the ability of NHE inhibitors such as HMA to reduce ischemia-reperfusion injury may be related to the nearly complete removal of L-selectin from the neutrophil surface. 相似文献
994.
Sawalha MF Peralta-Videa JR Duarte-Gardea M Gardea-Torresdey JL 《Bioresource technology》2008,99(10):4438-4444
Experiments performed on the Cu(II), Pb(II), and Zn(II) binding by saltbush biomass (Atriplex canescens) showed that the metal binding increased as pH increased from 2.0 to 5.0. The highest amounts of Cu, Pb, and Zn bound by the native biomass varied from 48-89%, 89-94%, and 65-73%, respectively. The hydrolyzed biomass bound similar amount of Pb and 50% more Cu and Zn than the native. The esterified biomass had a lower binding capacity than native; however, esterified flowers bound 45% more Cu at pH 2.0 than native flowers. The optimum binding time was 10 min or less. More than 60% of the bound Cu was recovered using 0.1 mM HCl, while more than 90% of Pb was recovered with either HCl or sodium citrate at 0.1 mM. For Zn, 0.1 mM sodium citrate allowed the recovery of 75%. Results indicated that carboxyl groups participate in the Cu, Pb, and Zn binding. 相似文献
995.
Pleurotus species are recognized for producing beta-glucans with important medicinal properties as a constituent of the cellular wall of the fruiting body or of the mycelium. The aims of this work were to select a culture medium that maximized the production of biomass and polysaccharides produced by Pleurotus ostreatus DSM 1833 and to evaluate the selected medium in two values of initial oxygen transfer rate -K(L)a (10.2 and 19.3 h(-1)). A 2* *4 factorial design was constructed to evaluate the supplementation of wheat extract with corn steep liquor--CSL (10 or 20 g L(-1)), yeast extract--YE (2 or 5gL(-1)), ammonium sulfate--AS (0 or 5 g L(-1)) and glucose (20 or 40 g L(-1)). In terms of maximum productivity in biomass and global productivity in polysaccharides, the best values were obtained when 5 g L(-1) of YE and 40 g L(-1) of glucose were used. In terms of maximum concentration of biomass, the best results were obtained when 20 g L(-1) of CSL and 40 g L(-1) of glucose were used. The best results in terms of production of biomass and polysaccharides were achieved when lower initial K(L)a (10.2 h(-1)) was used. 相似文献
996.
Torres-Gómez H Hernández-Núñez E León-Rivera I Guerrero-Alvarez J Cedillo-Rivera R Moo-Puc R Argotte-Ramos R Rodríguez-Gutiérrez Mdel C Chan-Bacab MJ Navarrete-Vázquez G 《Bioorganic & medicinal chemistry letters》2008,18(11):3147-3151
A series of ten novel hybrids from benzimidazole and pentamidine were prepared using a short synthetic route. Each compound was tested in vitro against the protozoa Trichomonas vaginalis, Giardia lamblia, Entamoeba histolytica, Leishmania mexicana, and Plasmodium berghei, in comparison with pentamidine and metronidazole. Some analogues showed high bioactivity in the low micromolar range (IC(50)<1 microM) against the first four protozoa, which make them significantly more potent than either standard. 1,5-bis[4-(5-methoxy-1H-benzimidazole-2-yl)phenoxy]pentane (2) was 3- and 9-fold more potent againstG. lamblia than metronidazole and pentamidine, respectively. This compound was 23-, 108-, and 13-fold more active than pentamidine against T. vaginalis, E. histolytica and L. mexicana, respectively. Studying further structure-activity relationships through the use of bioisosteric substitution in these hybrids should provide new leads against protozoal diseases. 相似文献
997.
998.
Carlos E. Aragón Maritza Escalona Iris Capote Danilo Pina Inaudis Cejas Roberto Rodriguez Maria Jesus Cañal Jorge Sandoval Sophe Roels Pierre Debergh Justo Gonzalez-Olmedo 《In vitro cellular & developmental biology. Plant》2005,41(4):550-554
Summary The photosynthetic capacity changes and the main enzymatic systems related to carbon metabolism were investigated during the
in vitro culture of plantain shoots (Musa AAB cv. CEMSA 3/4) in temporary immersion bioreactors (TIB) and their subsequent acclimatization.
The maximal rate of photosynthesis (Pn), transpiration, and the activity of the carbon metabolism enzymes phosphoenolpyruvate
carboxylase (PEPC), acid invertase (AI), pyruvate kinase (PK) and sucrose phosphate synthase (SPS) were measured every 7 d
during the 21 d of elongation in TIB, and the following 42 d of acclimatization. Sucrose content in the liquid medium and
in the leaves was also determined. The most significant changes in plant growth were observed during acclimatization. During
the in vitro stage photosynthesis was limited (4–6 μmol CO2m−2s−1); the photosynthetic rate however increases rapidly and significantly as soon as in vitro culture is over during acclimatization. PEPC activity increased during the whole evaluation period. The highest levels were
achieved around days 42 and 56. PK and SPS activities were optimal during the first weeks in acclimatization (28–35 d), while
AI increased at the beginning of the elongation phase (7 d), and later at the end of the acclimatization (49–63 d). The relationships
between morphological parameters, photosynthetic capacity of the plantlets and the carbon metabolism enzymes during both phases
of the culture are discussed. 相似文献
999.
Virulence genes and intimin types of Shiga-toxin-producing Escherichia coli isolated from cattle and beef products in Argentina. 总被引:4,自引:0,他引:4
Miguel Blanco Nora L Padola Alejandra Krüger Marcelo E Sanz Jesús E Blanco Enrique A González Ghizlane Dahbi Azucena Mora María Isabel Bernárdez Analía I Etcheverría Guillermo H Arroyo Paula M A Lucchesi Alberto E Parma Jorge Blanco 《International microbiology》2004,7(4):269-276
A total of 153 Shiga-toxin-producing Escherichia coli (STEC) isolates from feces of cattle and beef products (hamburgers and ground beef) in Argentina were characterized in this study. PCR showed that 22 (14%) isolates carried stx1 genes, 113 (74%) possessed stx2 genes and 18 (12%) both stx1 and stx2. Intimin (eae), enterohemolysin (ehxA), and STEC autoagglutinating adhesin (saa) virulence genes were detected in 36 (24%), 70 (46%) and in 34 (22%) of the isolates, respectively. None of 34 saa-positive isolates carried the gene eae, and 31 were ehxA-positive. Fourteen (7 of serotype O26:H11 and 4 of serotype O5:H-) isolates had intimin b1, 16 isolates possessed intimin g1 (11 of serotype O145:H- and 5 of serotype O157:H7), 5 isolates had intimin type e1 (4 of serotypes O103:H- and O103:H2), and one isolate O111:H- showed intimin type q/g2. Although the 153 STEC isolates belonged to 63 different seropathotypes, only 12 accounted for 58% of isolates. Seropathotype ONT:H- stx2 (18 isolates) was the most common, followed by O171:H2 stx2 (12 isolates), etc. The majority (84%) of STEC isolates belonged to serotypes previously found in human STEC and 56% to serotypes associated with STEC isolated from patients with hemolytic uremic syndrome (HUS). Thus, this study confirms that cattle are a major reservoir of STEC pathogenic for humans. To our knowledge, this is the first study that described the presence of saa gene in STEC of serotypes O20:H19, O39:H49, O74:H28, O79:H19, O116:H21, O120:H19, O141:H7, O141:H8, O174:H21, and ONT:H21. The serotypes O120:H19 and O185:H7 were not previously reported in bovine STEC. 相似文献
1000.
The demographic costs of nectar production in the desert perennial Prosopis glandulosa (Mimosoideae): a modular approach 总被引:1,自引:0,他引:1
Golubov Jordan Mandujano María C. Montaña Carlos López-Portillo Jorge Eguiarte Luis E. 《Plant Ecology》2004,170(2):267-275
Nectar production in angiosperms is considered to represent a reproductive cost, and has been associated with a decrease in
fruit set or an overall decrease in the energetic budget of the plant. Populations of Prosopis glandulosa var. torreyana (honey mesquite) are a suitable system to evaluate the demographic costs of nectar production, as populations are composed
of a 1:1 proportion of nectarful to nectarless individuals. The study was carried out in a population of 404 individuals of
Prosopis g1andulosa var. torreyana found in an area with differing water availability in the Southern Chihuahuan Desert. The possible costs of nectar production
were assessed on 1212 shoots of the honey mesquite that were tagged in 1994 and followed until 1998. We used two methods of
analysis to describe the effect of nectar production on modular population dynamics: matrix analysis and log-xlinear models.
Water availability and the varying environmental conditions affected plant growth, but nectar production did not have an effect
on the demographic parameters we measured. The values of λ did not differ between nectar morphs and the only important effects
we detected were the year to year variation in precipitation and microclimate differences at each site. Furthermore, the elasticity
of each demographic process (growth, fecundity, retrogression and stasis) between nectar morphs did not differ. The log-linear
models suggested a similar pattern but could discriminate the importance of each factor (nectar morph, year and site) on module
fate. We were not able to detect a demographic cost of nectar production in the honey mesquite. The absence of a demographic
response could be due to the negligible cost of producing nectar for this species or that the resources allocated for growth
are different from those allocated for reproduction. Our results suggest that the modular fates of mesquites are mainly determined
by environmental factors.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献