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101.
Diffusional limitations explain the lower photosynthetic capacity of ferns as compared with angiosperms in a common garden study 下载免费PDF全文
M. CARRIQUÍ H. M. CABRERA M. À. CONESA R. E. COOPMAN C. DOUTHE J. GAGO A. GALLÉ J. GALMÉS M. RIBAS‐CARBO M. TOMÁS J. FLEXAS 《Plant, cell & environment》2015,38(3):448-460
Ferns are thought to have lower photosynthetic rates than angiosperms and they lack fine stomatal regulation. However, no study has directly compared photosynthesis in plants of both groups grown under optimal conditions in a common environment. We present a common garden comparison of seven angiosperms and seven ferns paired by habitat preference, with the aims of (1) confirming that ferns do have lower photosynthesis capacity than angiosperms and quantifying these differences; (2) determining the importance of diffusional versus biochemical limitations; and (3) analysing the potential implication of leaf anatomical traits in setting the photosynthesis capacity in both groups. On average, the photosynthetic rate of ferns was about half that of angiosperms, and they exhibited lower stomatal and mesophyll conductance to CO2 (gm), maximum velocity of carboxylation and electron transport rate. A quantitative limitation analysis revealed that stomatal and mesophyll conductances were co‐responsible for the lower photosynthesis of ferns as compared with angiosperms. However, gm alone was the most constraining factor for photosynthesis in ferns. Consistently, leaf anatomy showed important differences between angiosperms and ferns, especially in cell wall thickness and the surface of chloroplasts exposed to intercellular air spaces. 相似文献
102.
Differential effects of temperature change and human impact on European Late Quaternary mammalian extinctions 下载免费PDF全文
Sara Varela Matheus Souza Lima‐Ribeiro JosÉ Alexandre Felizola Diniz‐Filho David Storch 《Global Change Biology》2015,21(4):1475-1481
Species that inhabited Europe during the Late Quaternary were impacted by temperature changes and early humans, resulting in the disappearance of half of the European large mammals. However, quantifying the relative importance that each factor had in the extinction risk of species has been challenging, mostly due to the spatio‐temporal biases of fossil records, which complicate the calibration of realistic and accurate ecological niche modeling. Here, we overcome this problem by using ecotypes, and not real species, to run our models. We created 40 ecotypes with different temperature requirements (mean temperature from ?20 °C to 25 °C and temperature range from 10 °C to 40 °C) and used them to quantify the effect of climate change and human impact. Our results show that cold‐adapted ecotypes would have been highly affected by past temperature changes in Europe, whereas temperate and warm‐adapted ecotypes would have been positively affected by temperature change. Human impact affected all ecotypes negatively, and temperate ecotypes suffered the greatest impacts. Based on these results, the extinction of cold‐adapted species like Mammuthus primigenius may be related to temperature change, while the extinction of temperate species, like Crocuta crocuta, may be related to human impact. Our results suggest that temperature change and human impact affected different ecotypes in distinct ways, and that the interaction of both impacts may have shaped species extinctions in Europe. 相似文献
103.
Burykh ÉA 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2011,97(5):459-471
Two groups of individuals were distinguished in experiments with acute hypoxic action (respiration of oxygen-nitrogen mixture with 8 % oxygen content) - with low (LHR) and high (HHR) resistance to hypoxia. In subjects of the LR group, slowing down of the pulse rate and lowering of arterial pressure in the shoulder artery were observed on the 5th-10th minute of hypoxia. In the HHR subjects, primary growth of the pulse rate was followed by its stabilization; no significant changes of the arterial pressure were observed. In LHR subjects, in the first 5-10 min of the hypoxia, a significantly lower level of the blood oxygen saturation was observed in comparison to the HHR. In the LHR group, there was a higher increment of amplitude-frequency index of the rheoencephalogram in comparison to the HHR, indicating a higher increment of the cerebral blood flow. The slowing down of the pulse rate in the LHR subjects was accompanied with increasing cerebral pulse volume, so that in spite of the pulse rate slowing, the minute volume of cerebral circulation increased. In the LHR subjects, two-phased dynamics of the EEG was observed: in the first phase there was a slow growth of theta- and delta-band EEG spectral power, in the second phase (on the 5th-10th min of hypoxia), sharp (200-300 % of the background level) growth of the EEG spectral power in those bands was observed. In the HHR subjects, gradual growth of EEG spectral power occurred with relative stabilization on the 10th-12th min of hypoxia. Possible role of the stress in the collapse-like reaction during acute hypoxia is analysed, which might cause increase of the oxygen request of the brain, higher growth of cerebral blood flow and more pronounced lowering of functional activity of the brain in the LHR subjects. 相似文献
104.
K. MOKHTAR‐JAMAÏ M. PASCUAL J.‐B. LEDOUX R. COMA J.‐P. FÉRAL J. GARRABOU D. AURELLE 《Molecular ecology》2011,20(16):3291-3305
Defining the scale of connectivity among marine populations and identifying the barriers to gene flow are tasks of fundamental importance for understanding the genetic structure of populations and for the design of marine reserves. Here, we investigated the population genetic structure at three spatial scales of the red gorgonian Paramuricea clavata (Cnidaria, Octocorallia), a key species dwelling in the coralligenous assemblages of the Mediterranean Sea. Colonies of P. clavata were collected from 39 locations across the Mediterranean Sea from Morocco to Turkey and analysed using microsatellite loci. Within three regions (Medes, Marseille and North Corsica), sampling was obtained from multiple locations and at different depths. Three different approaches (measures of genetic differentiation, Bayesian clustering and spatially explicit maximum‐difference algorithm) were used to determine the pattern of genetic structure. We identified genetic breaks in the spatial distribution of genetic diversity, which were concordant with oceanographic conditions in the Mediterranean Sea. We revealed a high level of genetic differentiation among populations and a pattern of isolation by distance across the studied area and within the three regions, underlining short effective larval dispersal in this species. We observed genetic differentiation among populations in the same locality dwelling at different depths, which may be explained by local oceanographic conditions and which may allow a process of local adaptation of the populations to their environment. We discuss the implications of our results for the conservation of the species, which is exposed to various threats. 相似文献
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108.
de Barros EP Garcia-Pinto AB Machado PY dos Santos Pereira MJ de Carvalho JJ 《Journal of molecular histology》2011,42(4):323-331
The incidence of chronic renal diseases is increasing worldwide, and there is a great need to identify therapies capable of
arresting or reducing disease progression. The current treatment of chronic nephropathies is limited to angiotensin-converting
enzyme inhibitors and angiotensin receptor blockers, but increasing clinical and experimental evidence suggests that statins
could play a therapeutic role. Ultrastructural studies have shown the presence of gap junctions within all the cells of the
glomerulus and podocytes have been found to contain primarily connexin-43. The present study aims to observe the beneficial
effects of rosuvastatin on structural and ultrastructural renal morphology and on glomerular connexin-43 expression in normotensive
rats and spontaneously hypertensive rats (SHR). Rats were randomly allocated into four groups: WKY-C: normotensive animals
no receiving rosuvastatin; WKY-ROS: normotensive animals receiving rosuvastatin; SHR-C: hypertensive animals no receiving
rosuvastatin; SHR-ROS: hypertensive animals receiving rosuvastatin. Our results show no differences in blood urea, creatinine,
uric acid and creatine phosphokinase levels between the groups, however, there was an decreasing of 24-h protein excretion
in SHR-ROS. Capsular area in SHR-ROS was decreased, however, there was no alteration in urinary space. By transmission electron
microscopy the slit diaphragm and podocyte foot processes were more preserved in SHR-ROS. By scanning electron microscopy
the podocyte foot processes were more preserved in SHR-ROS. Increased connexin-43 immunofluorescence was observed in glomeruli
of WKY-ROS and SHR-ROS. In conclusion, we hypothesize that renal pleiotropic effect of rosuvastatin can be a therapeutic tool
for improving kidney ultrastructure and, consequently, renal function in hypertensive individuals. 相似文献
109.
Myrtaceae family (121 genera, 3800-5800 spp.) is one of the most important families in tropical forests. They are aromatic trees or shrubs, which frequently produce edible fruits. In the neotropics, ca. 1000 species were found. Several members of this family are used in folk medicine, mainly as an antidiarrheal, antimicrobial, antioxidant, cleanser, antirheumatic, and anti-inflammatory agent and to decrease the blood cholesterol. In addition, some fruits are eaten fresh or used to make juices, liqueurs, and sweets very much appreciated by people. The flavor composition of some fruits belonging to the Myrtaceae family has been extensively studied due to their pleasant and intense aromas. Most of the essential oils of neotropical Myrtaceae analyzed so far are characterized by predominance of sesquiterpenes, some with important biological properties. In the present work, chemical and pharmacological studies carried out on neotropical Myrtaceae species are reviewed, based on original articles published since 1980. The uses in folk medicine and chemotaxonomic importance of secondary metabolites are also briefly discussed. 相似文献
110.
LORENA GÓMEZ‐APARICIO RAÚL GARCÍA‐VALDÉS PALOMA RUÍZ‐BENITO MIGUEL A. ZAVALA 《Global Change Biology》2011,17(7):2400-2414
Most large‐scale multispecies studies of tree growth have been conducted in tropical and cool temperate forests, whereas Mediterranean water‐limited ecosystems have received much less attention. This limits our understanding of how growth of coexisting tree species varies along environmental gradients in these forests, and the implications for species interactions and community assembly under current and future climatic conditions. Here, we quantify the absolute effect and relative importance of climate, tree size and competition as determinants of tree growth patterns in Iberian forests, and explore interspecific differences in the two components of competitive ability (competitive response and effect) along climatic and size gradients. Spatially explicit neighborhood models were developed to predict tree growth for the 15 most abundant Iberian tree species using permanent‐plot data from the Spanish Second and Third National Forest Inventory (IFN). Our neighborhood analyses showed a climatic and size effect on tree growth, but also revealed that competition from neighbors has a comparatively much larger impact on growth in Iberian forests. Moreover, the sensitivity to competition (i.e. competitive response) of target trees varied markedly along climatic gradients causing significant rank reversals in species performance, particularly under xeric conditions. We also found compelling evidence for strong species‐specific competitive effects in these forests. Altogether, these results constitute critical new information which not only furthers our understanding of important theoretical questions about the assembly of Mediterranean forests, but will also be of help in developing new guidelines for adapting forests in this climatic boundary to global change. If we consider the climatic gradients of this study as a surrogate for future climatic conditions, then we should expect absolute growth rates to decrease and sensitivity to competition to increase in most forests of the Iberian Peninsula (in all but the northern Atlantic forests), making these management considerations even more important in the future. 相似文献