全文获取类型
收费全文 | 2787篇 |
免费 | 272篇 |
国内免费 | 2篇 |
专业分类
3061篇 |
出版年
2023年 | 19篇 |
2022年 | 29篇 |
2021年 | 43篇 |
2020年 | 41篇 |
2019年 | 48篇 |
2018年 | 48篇 |
2017年 | 50篇 |
2016年 | 67篇 |
2015年 | 138篇 |
2014年 | 140篇 |
2013年 | 162篇 |
2012年 | 248篇 |
2011年 | 230篇 |
2010年 | 142篇 |
2009年 | 134篇 |
2008年 | 196篇 |
2007年 | 175篇 |
2006年 | 160篇 |
2005年 | 166篇 |
2004年 | 159篇 |
2003年 | 147篇 |
2002年 | 144篇 |
2001年 | 26篇 |
2000年 | 15篇 |
1999年 | 23篇 |
1998年 | 33篇 |
1997年 | 19篇 |
1996年 | 18篇 |
1995年 | 28篇 |
1994年 | 13篇 |
1993年 | 21篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1974年 | 8篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1969年 | 5篇 |
1955年 | 3篇 |
排序方式: 共有3061条查询结果,搜索用时 15 毫秒
81.
Mellinger DK Nieukirk SL Klinck K Klinck H Dziak RP Clapham PJ Brandsdóttir B 《Biology letters》2011,7(3):411-413
North Atlantic right whales (Eubalaena glacialis) were found in an important nineteenth century whaling area east of southern Greenland, from which they were once thought to have been extirpated. In 2007-2008, a 1-year passive acoustic survey was conducted at five sites in and near the 'Cape Farewell Ground', the former whaling ground. Over 2000 right whale calls were recorded at these sites, primarily during July-November. Most calls were northwest of the historic ground, suggesting a broader range in this region than previously known. Geographical and temporal separation of calls confirms use of this area by multiple animals. 相似文献
82.
83.
Mayr JA Freisinger P Schlachter K Rolinski B Zimmermann FA Scheffner T Haack TB Koch J Ahting U Prokisch H Sperl W 《American journal of human genetics》2011,(6):806-812
Thiamine pyrophosphate (TPP) is an essential cofactor of the cytosolic transketolase and of three mitochondrial enzymes involved in the oxidative decarboxylation of either pyruvate, α-ketoglutarate or branched chain amino acids. Thiamine is taken up by specific transporters into the cell and converted to the active TPP by thiamine pyrophosphokinase (TPK) in the cytosol from where it can be transported into mitochondria. Here, we report five individuals from three families presenting with variable degrees of ataxia, psychomotor retardation, progressive dystonia, and lactic acidosis. Investigation of the mitochondrial energy metabolism showed reduced oxidation of pyruvate but normal pyruvate dehydrogenase complex activity in the presence of excess TPP. A reduced concentration of TPP was found in the muscle and blood. Mutation analysis of TPK1 uncovered three missense, one splice-site, and one frameshift mutation resulting in decreased TPK protein levels. 相似文献
84.
Fox BM Natero R Richard K Connors R Roveto PM Beckmann H Haller K Golde J Xiao SH Kayser F 《Bioorganic & medicinal chemistry letters》2011,21(8):2460-2467
We discovered novel pyrrolidine MCHR1 antagonist 1 possessing moderate potency. Profiling of pyrrolidine 1 demonstrated that it was an inhibitor of the hERG channel. Investigation of the structure-activity relationship of this class of pyrrolidines allowed us to optimize the MCHR1 potency and decrease the hERG inhibition. Increasing the acidity of the amide proton by converting the benzamide in lead 1 to an anilide provided single digit nanomolar MCHR1 antagonists while replacing the dimethoxyphenyl ring of 1 with alkyl groups possessing increased polarity dramatically reduced the hERG inhibition. 相似文献
85.
Eva Schnabel Stefan Karrasch Holger Schulz Sven Gl?ser Christa Meisinger Margit Heier Annette Peters H-Erich Wichmann Jürgen Behr Rudolf M Huber Joachim Heinrich 《Respiratory research》2011,12(1):50
Background
Several studies showed that blood pressure and lung function are associated. Additionally, a potential effect of antihypertensive medication, especially beta-blockers, on lung function has been discussed. However, side effects of beta-blockers have been investigated mainly in patients with already reduced lung function. Thus, aim of this analysis is to determine whether hypertension and antihypertensive medication have an adverse effect on lung function in a general adult population.Methods
Within the population-based KORA F4 study 1319 adults aged 40-65 years performed lung function tests and blood pressure measurements. Additionally, information on anthropometric measurements, medical history and use of antihypertensive medication was available. Multivariable regression models were applied to study the association between blood pressure, antihypertensive medication and lung function.Results
High blood pressure as well as antihypertensive medication were associated with lower forced expiratory volume in one second (p = 0.02 respectively p = 0.05; R2: 0.65) and forced vital capacity values (p = 0.01 respectively p = 0.05, R2: 0.73). Furthermore, a detailed analysis of antihypertensive medication pointed out that only the use of beta-blockers was associated with reduced lung function, whereas other antihypertensive medication had no effect on lung function. The adverse effect of beta-blockers was significant for forced vital capacity (p = 0.04; R2: 0.65), while the association with forced expiratory volume in one second showed a trend toward significance (p = 0.07; R2: 0.73). In the same model high blood pressure was associated with reduced forced vital capacity (p = 0.01) and forced expiratory volume in one second (p = 0.03) values, too.Conclusion
Our analysis indicates that both high blood pressure and the use of beta-blockers, but not the use of other antihypertensive medication, are associated with reduced lung function in a general adult population. 相似文献86.
Ringseis R Heller K Kluge H Eder K 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2011,158(4):450-454
Rodents are able to lower fatty acid utilization in liver and muscle during lactation in order to spare fatty acids for the production of milk triacylglycerols, an effect which is mediated by a down-regulation of peroxisome proliferator-activated receptor α (PPARα). The present study was performed to investigate whether similar fatty acid sparing effects are developing in lactating sows. We considered PPARα and its target genes involved in fatty acid utilization in biopsy samples from muscle and adipose tissue of lactating compared to non-lactating sows. In muscle, PPARα target genes involved in fatty acid utilization were up-regulated during lactation indicating that the fatty acid utilization in muscle was increased. Activation of PPARα was probably due to increased concentrations of non-esterified fatty acids in plasma observed in the lactating sows. In contrast to muscle, PPARα and its target genes involved in β-oxidation in white adipose tissue were down-regulated in early lactation. Overall, the present study shows that sows, unlike rats, are not able to reduce the fatty acid utilization in muscle in order to spare fatty acids for milk production. However, fatty acid oxidation in adipose tissue is lowered during early lactation, an effect that might be helpful to conserve fatty acids released from adipose tissue for the delivery into other tissues, including mammary gland, via the blood. 相似文献
87.
Ahmed M. Abouzid Thomas Frischmuth Holger Jeske 《Molecular & general genetics : MGG》1988,212(2):252-258
Summary The putative replicative form of the abutilon mosaic virus (AbMV), a geminivirus, was purified from infected plants. It was shown to consist of a bipartite genome of 2660 and 2640 bp. This double-stranded DNA has a closed or relaxed circular conformation and part of it is packed in nucleoprotein complexes with a chromatin-like structure. Similarities between the geminiviruses and the animal simian virus 40 are discussed against this back-ground.Cloning was performed under L2/B1 conditions according to the licence of the ZKBS 1526/1This article is based on a doctoral study by A.A. and T.F. in the Faculty of Biology, University of Hamburg 相似文献
88.
Lena Kathe Reiner Krmer Holger Budahn Klaus Pillen Frank Rabenstein Thomas Nothnagel 《Journal of Phytopathology》2019,167(10):558-566
Fusarium oxysporum is one of the major pathogens causing root and crown rot in asparagus. Breeding of cultivars resistant to F. oxysporum would be the most efficient strategy for pathogen control. In this study, a bioassay was developed for screening seedling resistance. The non‐destructive bioassay comprises inoculation with a highly aggressive F. oxysporum isolate, incubation in a climate chamber and quantification of disease symptoms by a digital image analysing system and a PTA‐ELISA. This bioassay is simple to implement and demonstrated high reproducibility. Subsequently, it was used to determine the resistance behaviour of 16 asparagus genotypes to F. oxysporum. The asparagus cultivars revealed different levels of susceptibility, whereas the wild relative A. densiflorus was confirmed to be resistant. 相似文献
89.
Holger Kneuper Zhen Ping Cao Kate B. Twomey Martin Zoltner Franziska Jäger James S. Cargill James Chalmers Magdalena M. van der Kooi‐Pol Jan Maarten van Dijl Robert P. Ryan William N. Hunter Tracy Palmer 《Molecular microbiology》2014,93(5):928-943
The Type VII protein secretion system, found in Gram‐positive bacteria, secretes small proteins, containing a conserved W‐x‐G amino acid sequence motif, to the growth medium. Staphylococcus aureus has a conserved Type VII secretion system, termed Ess, which is dispensable for laboratory growth but required for virulence. In this study we show that there are unexpected differences in the organization of the ess gene cluster between closely related strains of S. aureus. We further show that in laboratory growth medium different strains of S. aureus secrete the EsxA and EsxC substrate proteins at different growth points, and that the Ess system in strain Newman is inactive under these conditions. Systematic deletion analysis in S. aureus RN6390 is consistent with the EsaA, EsaB, EssA, EssB, EssC and EsxA proteins comprising core components of the secretion machinery in this strain. Finally we demonstrate that the Ess secretion machinery of two S. aureus strains, RN6390 and COL, is important for nasal colonization and virulence in the murine lung pneumonia model. Surprisingly, however, the secretion system plays no role in the virulence of strain SA113 under the same conditions. 相似文献
90.
Karsten Schnatbaum Victor Solis‐Mezarino Daniil Pokrovsky Frederike Schfer Dennis Nagl Lars Hornberger Johannes Zerweck Tobias Knaute Julia Avramova‐Nehmer Mike Schutkowski Veit Hornung Holger Wenschuh Moritz Carl Vlker‐Albert Axel Imhof Ulf Reimer 《Proteomics》2020,20(10)
Targeted proteomics depends on the availability of stable isotope labeled (SIL) peptide standards, which for absolute protein quantification need to be absolutely quantified. In the present study, three new approaches for absolute quantification of SIL peptides are developed. All approaches rely on a quantification tag (Qtag) with a specific UV absorption. The Qtag is attached to the peptide during synthesis and is removed by tryptic digestion under standard proteomics workflow conditions. While one quantification method (method A) is designed to allow the fast and economic production of absolutely quantified SIL peptides, two other methods (methods B and C) are developed to enable the straightforward re‐quantification of SIL peptides after reconstitution to control and monitor known problems related to peptide solubility, precipitation, and adhesion to vials. All methods yield consistent results when compared to each other and when compared to quantification by amino acid analysis. The precise quantitation methods are used to characterize the in vivo specificity of the H3 specific histone methyltransferase EZH2. 相似文献