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941.
Local site differences in survival and parasitism of periwinkles (Littorina sitkana Philippi, 1846)
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Mónica Ayala‐Díaz Jean M. L. Richardson Bradley R. Anholt 《Ecology and evolution》2017,7(4):1021-1029
The periwinkle, Littorina sitkana, is found throughout the intertidal zone, often in isolated subpopulations. The majority of trematode parasites use snails as intermediate hosts, and decreased survivorship is often observed in snails infected with trematodes. Sampling L. sitkana from four sites in Barkley Sound, British Columbia, Canada, we test the effects of parasitic infection on snail survival using maximum likelihood and Bayesian approaches using the software MARK and WinBUGS. We found that survival of periwinkles and trematode community composition differed among sites, but survival and trematode prevalence were uncorrelated. WinBUGS performed better than MARK in two ways: (1) by allowing the use of information on known mortality, thus preventing survival overestimation; and (2) by giving more stable estimates while testing the effect of body size on snail survival. Our results suggest that snail survival depends heavily on local environmental factors that may vary greatly within a small geographical region. These findings are important because the majority of experimental studies on survival are done on snails from a single location. 相似文献
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944.
Ebben WP Feldmann CR Dayne A Mitsche D Chmielewski LM Alexander P Knetgzer KJ 《Journal of strength and conditioning research / National Strength & Conditioning Association》2008,22(6):1947-1949
The purpose of this study was to determine whether there is a linear relationship between the squat and a variety of quadriceps resistance training exercises for the purpose of creating prediction equations for the determination of quadriceps exercise loads based on the squat load. Six-repetition maximums (RMs) of the squat, as well as four common resistance training exercises that activate the quadriceps including the deadlift, lunge, step-up, and leg extension, were determined for each subject. Subjects included 21 college students. Data were evaluated using linear regression analysis to predict quadriceps exercise loads from 6RM squat data and were cross-validated with the prediction of sum of squares statistic. Analysis of the data revealed that the squat is a significant predictor of loads for the dead lift (R2 = 0.81, standard error of the estimate [SEE] = 12.50 kg), lunge (R2 = 0.62, SEE = 12.57 kg), step-up (R2 = 0.71, SEE = 9.58 kg), and leg extension (R2=0.67, SEE = 10.26 kg) exercises. Based on the analysis of the data, the following 6RM prediction equations were devised for each exercise: (a) deadlift load = squat load (0.83) + 14.92 kg, (b) lunge load = squat load (0.52) + 14.82 kg, (c) step-up load = squat load (0.50) + 3.32 kg, and (d) leg extension load = squat load (0.48) + 9.58 kg. Results from testing core exercises such as the squat can provide useful data for the assignment of loads for other exercises. 相似文献
945.
van den Berg MA Albang R Albermann K Badger JH Daran JM Driessen AJ Garcia-Estrada C Fedorova ND Harris DM Heijne WH Joardar V Kiel JA Kovalchuk A Martín JF Nierman WC Nijland JG Pronk JT Roubos JA van der Klei IJ van Peij NN Veenhuis M von Döhren H Wagner C Wortman J Bovenberg RA 《Nature biotechnology》2008,26(10):1161-1168
946.
Alexander A. Timoshin Diana Yu. Drobotova Vladimir L. Lakomkin Enno K. Ruuge Anatoly F. Vanin 《Nitric oxide》2008,19(4):338-344
It was found that microdialysis, i.e., passage of aqueous solutions of iron-N-methyl-d-glucamine dithiocarbamate complexes through dialysis fibers implanted into heart, kidney and liver tissues of narcotized rats, was accompanied by effective binding of the complexes to nitric oxide from interstitial fluid. The walls of dialysis fibers used in this study were permeable for compounds with molecular weight not exceeding 5 kDa. The dialyzate samples collected every 20 min and containing diamagnetic nitrosyl Fe3+-MGD adducts were reduced to the paramagnetic state with sodium dithionite; their concentration was measured by the EPR method. The basic level of the adducts, which represented mononitrosyl iron complexes with MGD (MNIC–MGD), in the dialyzate samples of all tested organs were similar (1 μМ). Treatment of animals with the water-soluble nitroglycerine analog Isoket or a low-molecular dinitrosyl iron thiosulfate complex as a NO donor increased the concentration of MNIC–MGD with going out into a plateau. The novel approach allows determination of nitric oxide levels in tissue interstitial fluid from concentration of MNIC–MGD formed during microdialysis. 相似文献
947.
Kang J Yang M Li B Qi W Zhang C Shokat KM Tomchick DR Machius M Yu H 《Molecular cell》2008,32(3):394-405
In mitosis, the spindle checkpoint detects a single unattached kinetochore, inhibits the anaphase-promoting complex or cyclosome (APC/C), and prevents premature sister chromatid separation. The checkpoint kinase Bub1 contributes to checkpoint sensitivity through phosphorylating the APC/C activator, Cdc20, and inhibiting APC/C catalytically. We report here the crystal structure of the kinase domain of Bub1, revealing the requirement of an N-terminal extension for its kinase activity. Though the activation segment of Bub1 is ordered and has structural features indicative of active kinases, the C-terminal portion of this segment sterically restricts substrate access to the active site. Bub1 uses docking motifs, so-called KEN boxes, outside its kinase domain to recruit Cdc20, one of two known KEN box receptors. The KEN boxes of Bub1 are required for the spindle checkpoint in human cells. Therefore, its unusual active-site conformation and mode of substrate recruitment suggest that Bub1 has an exquisitely tuned specificity for Cdc20. 相似文献
948.
The effects of chronic nitrogen fertilization on alpine tundra soil microbial communities: implications for carbon and nitrogen cycling 总被引:3,自引:0,他引:3
Nemergut DR Townsend AR Sattin SR Freeman KR Fierer N Neff JC Bowman WD Schadt CW Weintraub MN Schmidt SK 《Environmental microbiology》2008,10(11):3093-3105
Many studies have shown that changes in nitrogen (N) availability affect primary productivity in a variety of terrestrial systems, but less is known about the effects of the changing N cycle on soil organic matter (SOM) decomposition. We used a variety of techniques to examine the effects of chronic N amendments on SOM chemistry and microbial community structure and function in an alpine tundra soil. We collected surface soil (0-5 cm) samples from five control and five long-term N-amended plots established and maintained at the Niwot Ridge Long-term Ecological Research (LTER) site. Samples were bulked by treatment and all analyses were conducted on composite samples. The fungal community shifted in response to N amendments, with a decrease in the relative abundance of basidiomycetes. Bacterial community composition also shifted in the fertilized soil, with increases in the relative abundance of sequences related to the Bacteroidetes and Gemmatimonadetes, and decreases in the relative abundance of the Verrucomicrobia. We did not uncover any bacterial sequences that were closely related to known nitrifiers in either soil, but sequences related to archaeal nitrifiers were found in control soils. The ratio of fungi to bacteria did not change in the N-amended soils, but the ratio of archaea to bacteria dropped from 20% to less than 1% in the N-amended plots. Comparisons of aliphatic and aromatic carbon compounds, two broad categories of soil carbon compounds, revealed no between treatment differences. However, G-lignins were found in higher relative abundance in the fertilized soils, while proteins were detected in lower relative abundance. Finally, the activities of two soil enzymes involved in N cycling changed in response to chronic N amendments. These results suggest that chronic N fertilization induces significant shifts in soil carbon dynamics that correspond to shifts in microbial community structure and function. 相似文献
949.
Diana Perez-Staples Aaron M. T. Harmer Samuel R. Collins Phillip W. Taylor 《Agricultural and Forest Entomology》2008,10(3):255-262
1 Recent studies have shown that continuous access to a protein source (yeast hydrolysate) can greatly enhance the sexual performance of male Queensland fruit flies ( Bactrocera tryoni ; 'Q-flies'). However, in Sterile Insect Technique programmes used to eradicate or suppress wild populations, mass-reared Q-flies are typically fed only sucrose and water for up to 2 days before release.
2 We investigated whether adding a protein source to the diet of male Q-flies for a 24- or 48-h window after emergence and then removing it is sufficient to enhance mating probability, latency to mate, copula duration, probability of sperm storage, number of sperm stored, female remating tendency and longevity of male Q-flies.
3 Protein-fed males were more likely to mate than males fed only sucrose, especially when young. Protein-fed males also had shorter mating latencies and longer copulations than protein-deprived males.
4 Females mated by protein-fed males were more likely to store sperm, stored more sperm and were less likely to remate than were females mated by protein-deprived males. Females were also less likely to remate if their first mate had been large.
5 Overall, providing male Q-flies access to a protein source for a 24- or 48-h window early on in their adult life was sufficient to greatly enhance all assessed measures of performance. Although 24-h access was sufficient for a notable enhancement, further benefits were evident in males provided 48-h access.
6 The results are discussed in terms of the practical implications for Sterile Insect Technique programs used to eradicate or suppress wild Q-fly populations. 相似文献
2 We investigated whether adding a protein source to the diet of male Q-flies for a 24- or 48-h window after emergence and then removing it is sufficient to enhance mating probability, latency to mate, copula duration, probability of sperm storage, number of sperm stored, female remating tendency and longevity of male Q-flies.
3 Protein-fed males were more likely to mate than males fed only sucrose, especially when young. Protein-fed males also had shorter mating latencies and longer copulations than protein-deprived males.
4 Females mated by protein-fed males were more likely to store sperm, stored more sperm and were less likely to remate than were females mated by protein-deprived males. Females were also less likely to remate if their first mate had been large.
5 Overall, providing male Q-flies access to a protein source for a 24- or 48-h window early on in their adult life was sufficient to greatly enhance all assessed measures of performance. Although 24-h access was sufficient for a notable enhancement, further benefits were evident in males provided 48-h access.
6 The results are discussed in terms of the practical implications for Sterile Insect Technique programs used to eradicate or suppress wild Q-fly populations. 相似文献
950.
Santos Alonso Neskuts Izagirre Isabel Smith-Zubiaga Jesús Gardeazabal José Luís Díaz-Ramón José Luís Díaz-Pérez Diana Zelenika María Dolores Boyano Nico Smit Concepción de la Rúa 《BMC evolutionary biology》2008,8(1):74