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991.
Over the years, the Mondego estuary has undergone various anthropogenic impacts. One of the most serious was the closing of the communication between the two arms of the system (north and south), in the 1990s, which promoted eutrophication and a consequent water quality decline in the south arm. Several mitigation measures were subsequently implemented, in particular the re-establishing of the communication between the two arms in 2006, increasing water flow and reducing water residence time in the south arm. The present study aimed to evaluate the impact of management measures on the ecological and conservation condition of the Mondego estuary, through a longitudinal assessment of the structure and composition of the fish communities over a decade. The Mondego fish community showed important modifications over the years, in terms of structure, ecological quality and conservation value. The fish community status improved following the reconnection of both arms. In the south arm those changes appear to be more evident than in the other estuarine areas, where an inverse pattern was observed in the last few years. A redistribution of the fish species within the system may have been responsible for those unexpected alterations in the north arm and upstream area.  相似文献   
992.
993.
994.
The interpretation of cryo-electron tomograms of macromolecular complexes can be difficult because of the large amount of noise and because of the missing wedge effect. Here it is shown how the presence of rotational symmetry in a sample can be utilized to enhance the quality of a tomographic analysis. The orientation of symmetry axes in a sub-tomogram can be determined using a locked self-rotation function. Given this knowledge, the sub-tomogram density can then be averaged to improve its interpretability. Sub-tomograms of the icosahedral bacteriophage phiX174 are used to demonstrate the procedure.  相似文献   
995.
Functional redundancy can increase the resilience of ecosystem processes by providing insurance against species loss and the effects of abundance fluctuations. However, due to the difficulty of assessing individual species’ contributions and the lack of a metric allowing for a quantification of redundancy within communities, few attempts have been made to estimate redundancy for individual ecosystem processes. We present a new method linking interaction metrics with metabolic theory that allows for a quantification of redundancy at the level of ecosystem processes. Using this approach, redundancy in the predation on aphids and other prey by natural enemies across a landscape heterogeneity gradient was estimated. Functional redundancy of predators was high in heterogeneous landscapes, low in homogeneous landscapes and scaled with predator specialisation. Our approach allows quantifying functional redundancy within communities and can be used to assess the role of functional redundancy across a wide variety of ecosystem processes and environmental factors.  相似文献   
996.
Post-dispersal seed predation by slugs is increasingly being acknowledged as a potentially important contribution to this ecosystem function. However, specific drivers of predation rates in different landscape contexts are still unknown. We assessed the role of slugs as facultative seed predators along an urban–rural gradient and identified scale-dependent anthropogenic drivers that might affect either slugs or their function as seed predators.We used a combination of seed cafeterias and pitfall traps in grassy areas of eleven schoolyards and five field margins surrounded by different land-use types to assess slug activity density and seed predation rates and quantified urbanization, habitat heterogeneity and microhabitat structure.We show that slugs are important seed predators regardless of anthropogenic land use. Their activity density was a significant predictor for seed predation but increases in woody vegetation and bare soil also increased seed predation. This indicates that the magnitude of seed predation might also be affected by slug foraging activity and feeding behaviour, which might be influenced by habitat features such as the availability of vegetation and bare soil. Our results suggest that not only assessing the activity density (as proxy for relative abundance) of seed predators but also identifying effects on their feeding patterns and behaviour might increase our mechanistic understanding of relationships between land-use changes and seed predation and their impact on cultivated and wild plant species.  相似文献   
997.
Mikuni S  Tamura M  Kinjo M 《FEBS letters》2007,581(3):389-393
The diffusion properties of EGFP-hGRalpha and mutants C421G, A458T and I566 in living cells were analyzed. The wild type and mutants C421G and A458T translocated from the cytoplasm to the nucleus after addition of Dex; however, the Brownian motions of the proteins were different. The diffusion constant of wild-type GRalpha after addition of Dex slowed to 15.6% of that in the absence of Dex, whereas those of A458T and C421G slowed to 34.8% and 61.7%, respectively. This is the first report that dimer formation is less important than the binding activity of GRalpha to GRE in the living cell.  相似文献   
998.
999.
Genetically engineered mice provide an excellent tool to study the role of a particular gene in biological systems and will be increasingly used as models to understand the signal transduction mechanisms involved in ischemic preconditioning (IP). However, the phenomenon of IP has not been well characterized in this species. We therefore attempted to examine whether IP could protect isolated mouse heart against global ischemia/reperfusion (GI/R) injury. Thirty adult mice hearts were perfused at constant pressure of 55 mmHg in Langendorff mode. Following 20 min equilibration, the hearts were randomized into three groups (n = 10/each): (1) Control Group; (2) IP2.5 Group: IP with two cycles of 2.5 min GI + 2.5 min R; (3) IP5 Group: IP with 5 min GI + 5 min R. All hearts were then subjected to 20 min of GI and 30 min R (37°C). Ventricular developed force was measured by a force transducer attached to the apex. Leakage of CK and LDH was measured in coronary efflux. Infarct size was determined by tetrazolium staining. Following sustained GI/R, infarct size was significantly reduced in IP2.5 (13.8 ± 2.3%), but not in IP5 (20.1 ± 4.0%), when compared with non-preconditioned control (23.6 ± 3.8%) hearts. CK and LDH release was also reduced in both IP2.5 and IP5 groups. No significant improvement in post-ischemic ventricular contractile function was observed in either IP groups. We conclude that IP with repetitive cycles of brief GI/R is able to reduce myocardial infarct size and intracellular enzyme leakage caused by a sustained GI/R in the isolated perfused mouse heart. This anti-necrosis cardioprotection induced by IP was not associated with the amelioration of post-ischemic ventricular dysfunction.  相似文献   
1000.
The alkaline transition of cytochrome c is a model for protein structural switching in which the normal heme ligand is replaced by another group. Stopped flow data following a jump to high pH detect two slow kinetic phases, suggesting two rate-limiting structure changes. Results described here indicate that these events are controlled by the same structural unfolding reactions that account for the first two steps in the reversible unfolding pathway of cytochrome c. These and other results show that the cooperative folding-unfolding behavior of protein foldons can account for a variety of functional activities in addition to determining folding pathways.  相似文献   
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