全文获取类型
收费全文 | 6225篇 |
免费 | 573篇 |
国内免费 | 3篇 |
出版年
2023年 | 56篇 |
2022年 | 47篇 |
2021年 | 223篇 |
2020年 | 99篇 |
2019年 | 154篇 |
2018年 | 140篇 |
2017年 | 128篇 |
2016年 | 186篇 |
2015年 | 338篇 |
2014年 | 317篇 |
2013年 | 417篇 |
2012年 | 471篇 |
2011年 | 437篇 |
2010年 | 273篇 |
2009年 | 258篇 |
2008年 | 323篇 |
2007年 | 350篇 |
2006年 | 310篇 |
2005年 | 265篇 |
2004年 | 223篇 |
2003年 | 227篇 |
2002年 | 223篇 |
2001年 | 61篇 |
2000年 | 59篇 |
1999年 | 76篇 |
1998年 | 51篇 |
1997年 | 40篇 |
1996年 | 37篇 |
1995年 | 26篇 |
1994年 | 35篇 |
1993年 | 36篇 |
1992年 | 43篇 |
1991年 | 46篇 |
1990年 | 38篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 43篇 |
1986年 | 31篇 |
1985年 | 26篇 |
1984年 | 46篇 |
1982年 | 32篇 |
1980年 | 25篇 |
1979年 | 42篇 |
1978年 | 32篇 |
1977年 | 37篇 |
1976年 | 42篇 |
1975年 | 47篇 |
1974年 | 27篇 |
1972年 | 29篇 |
1968年 | 25篇 |
排序方式: 共有6801条查询结果,搜索用时 15 毫秒
991.
R. Schick E. Jacob 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1951,21(7-8):211-222
Ohne ZusammenfassungMit 2 Textabbildungen.
Elisabeth Schiemann zum 70. Geburtstag. 相似文献
992.
993.
994.
995.
996.
Respiration in Saccharomyces cerevisiae is regulated by small proteins such as the respiratory supercomplex factors (Rcf). One of these factors (Rcf1) has been shown to interact with complexes III (cyt. bc1) and IV (cytochrome c oxidase, CytcO) of the respiratory chain and to modulate the activity of the latter. Here, we investigated the effect of deleting Rcf1 on the functionality of CytcO, purified using a protein C-tag on core subunit 1 (Cox1). Specifically, we measured the kinetics of ligand binding to the CytcO catalytic site, the O2-reduction activity and changes in light absorption spectra. We found that upon removal of Rcf1 a fraction of the CytcO is incorrectly assembled with structural changes at the catalytic site. The data indicate that Rcf1 modulates the assembly and activity of CytcO by shifting the equilibrium of structural sub-states toward the fully active, intact form. 相似文献
997.
Estimating fish swimming metrics and metabolic rates with accelerometers: the influence of sampling frequency 下载免费PDF全文
Jacob W. Brownscombe Robert J. Lennox Andy J. Danylchuk Steven J. Cooke 《Journal of fish biology》2018,93(2):207-214
Accelerometry is growing in popularity for remotely measuring fish swimming metrics, but appropriate sampling frequencies for accurately measuring these metrics are not well studied. This research examined the influence of sampling frequency (1–25 Hz) with tri‐axial accelerometer biologgers on estimates of overall dynamic body acceleration (ODBA), tail‐beat frequency, swimming speed and metabolic rate of bonefish Albula vulpes in a swim‐tunnel respirometer and free‐swimming in a wetland mesocosm. In the swim tunnel, sampling frequencies of ≥ 5 Hz were sufficient to establish strong relationships between ODBA, swimming speed and metabolic rate. However, in free‐swimming bonefish, estimates of metabolic rate were more variable below 10 Hz. Sampling frequencies should be at least twice the maximum tail‐beat frequency to estimate this metric effectively, which is generally higher than those required to estimate ODBA, swimming speed and metabolic rate. While optimal sampling frequency probably varies among species due to tail‐beat frequency and swimming style, this study provides a reference point with a medium body‐sized sub‐carangiform teleost fish, enabling researchers to measure these metrics effectively and maximize study duration. 相似文献
998.
Suvash Shrestha On Chen Mary Greene Jinu Jacob John Yisachar Greenberg Felix Yang 《Indian pacing and electrophysiology journal》2016,16(1):3-7
Convergent atrial fibrillation ablation involves extensive epicardial as well as endocardial ablation of the left atrium. We examined whether it changes the morphology of the surface P wave. We reviewed electrocardiograms of 29 patients who underwent convergent ablation for atrial fibrillation. In leads V1, II and III, we measured P wave duration, area and amplitude before ablation, and at 1, 3 and 6 months from ablation.After ablation, there were no significant changes in P wave amplitude, area, or duration in leads II and III. There was a significant reduction in the area of the terminal negative deflection of the P wave in V1 from 0.38 mm2 to 0.13 mm2 (p = 0.03). There is also an acute increase in the amplitude and duration of the positive component of the P wave in V1 followed by a reduction in both by 6 months. Before ablation, 62.5% of the patients had biphasic P waves in V1. In 6 months, only 39.2% of them had biphasic P waves.Hybrid ablation causes a reduction of the terminal negative deflection of the P wave in V1 as well as temporal changes in the duration and amplitude of the positive component of the P wave in V1. This likely reflects the reduced electrical contribution of the posterior left atrium after ablation as well as anatomical and autonomic remodeling. Recognition of this altered sinus P wave morphology is useful in the diagnosis of atrial arrhythmias in this patient population. 相似文献
999.
T. Revathy Jobin John Jacob M. A. Jayasri K. Suthindhiran 《World journal of microbiology & biotechnology》2016,32(7):109
Magnetotactic bacteria (MTB) are aquatic prokaryotes that orient themselves to earth’s magnetic field with the help of intracellular organelle magnetosomes. Although many species of MTB have been identified, the isolation of MTB is a challenging task due to the lack of systematic isolation procedure and/or commercial media. In this study, we are reporting the isolation of magnetotactic spirillum from the Pulicat lagoon, India using a systematic and selective procedure. Sampling site was chosen on the basis of physicochemical properties of the ecosystem and the catalysed reporter deposition fluorescence in situ hybridization (CARD–FISH) analysis of sediment samples. In the current study, a combination of techniques including ‘capillary racetrack’ Purification and gradient cultivation resulted in the isolation of magnetotactic spirilla from aquatic sediments. Based on the 16S rRNA gene sequence analysis, the strain was identified as Magnetospirillum and was designated as Magnetospirillum sp. VITRJS1. The genes responsible for magnetosome formation (mamA, B, E, F, K, M, O, P, Q, T) were successfully detected using PCR amplification. The presence of cbbM gene confirmed that the isolate is chemolithoautotroph and utilises reduced sulphur as an electron source. Furthermore, magnetosomes extracted from VITRJS1 found to be cubo-octahedral in shape and 45 nm in size. Our results indicate that the systematic procedure using sediment analysis, CARD–FISH, and a combination of isolation methods enables the selective and rapid isolation of MTB from aquatic sediment sample. 相似文献
1000.
Looking into the past – the reaction of three grouse species to climate change over the last million years using whole genome sequences 下载免费PDF全文
Radoslav Kozma Páll Melsted Kristinn P. Magnússon Jacob Höglund 《Molecular ecology》2016,25(2):570-580
Tracking past population fluctuations can give insight into current levels of genetic variation present within species. Analysing population dynamics over larger timescales can be aligned to known climatic changes to determine the response of species to varying environments. Here, we applied the Pairwise Sequentially Markovian Coalescent (psmc ) model to infer past population dynamics of three widespread grouse species; black grouse, willow grouse and rock ptarmigan. This allowed the tracking of the effective population size (Ne) of all three species beyond 1 Mya, revealing that (i) early Pleistocene cooling (~2.5 Mya) caused an increase in the willow grouse and rock ptarmigan populations, (ii) the mid‐Brunhes event (~430 kya) and following climatic oscillations decreased the Ne of willow grouse and rock ptarmigan, but increased the Ne of black grouse and (iii) all three species reacted differently to the last glacial maximum (LGM) – black grouse increased prior to it, rock ptarmigan experienced a severe bottleneck and willow grouse was maintained at large population size. We postulate that the varying psmc signal throughout the LGM depicts only the local history of the species. Nevertheless, the large population fluctuations in willow grouse and rock ptarmigan indicate that both species are opportunistic breeders while black grouse tracks the climatic changes more slowly and is maintained at lower Ne. Our results highlight the usefulness of the psmc approach in investigating species’ reaction to climate change in the deep past, but also that caution should be taken in drawing general conclusions about the recent past. 相似文献