全文获取类型
收费全文 | 787篇 |
免费 | 75篇 |
国内免费 | 2篇 |
专业分类
864篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 27篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 27篇 |
2017年 | 19篇 |
2016年 | 27篇 |
2015年 | 59篇 |
2014年 | 48篇 |
2013年 | 58篇 |
2012年 | 69篇 |
2011年 | 73篇 |
2010年 | 57篇 |
2009年 | 29篇 |
2008年 | 44篇 |
2007年 | 52篇 |
2006年 | 41篇 |
2005年 | 38篇 |
2004年 | 31篇 |
2003年 | 34篇 |
2002年 | 18篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有864条查询结果,搜索用时 0 毫秒
71.
J Barp CL Sartório C Campos SF Llesuy AS Araujo A Belló-Klein 《Canadian journal of physiology and pharmacology》2012,90(9):1229-1234
The aim of this study was to evaluate the potential influence of endogenous ovarian hormones on cardiac oxidative stress in renovascular hypertension. Female Wistar rats (N = 10 per group) were divided among 4 groups: (i) normotensive control; (ii) hypertensive control; (iii) normotensive ovariectomized; and (iv) hypertensive ovariectomized rats. To induce hypertension, 2-kidney 1-clip (2K1C) Goldblatt's method was followed. Blood pressure (BP) was enhanced (25%) in 2K1C and it was not further altered in hypertensive ovariectomized animals. Lipid peroxidation (measured by thiobarbituric acid reactive substances; TBARS) increased in heart homogenates after ovariectomy (253%) and was additionally augmented when associated with hypertension (by 28%). Superoxide dismutase and catalase activities were similar in both hypertensive groups. Hypertension enhanced glutathione peroxidase activity (75%), but the association with ovariectomy prevented this change. Total radical trapping antioxidant potential (TRAP) decreased in hypertensive rats (34%) and was recovered when associated with ovariectomy. However, this adaptation seems not to be sufficient to avoid the increased oxidative damage in ovariectomized hypertensive animals. These results suggest a protective role for physiological ovarian hormones in the cardiac oxidative stress induced by 2K1C hypertension. 相似文献
72.
Angel García-Gutiérrez Francisco R. Cantón Fernando Gallardo Francisca Sánchez-Jiménez Francisco M. Cánovas 《Plant molecular biology》1995,27(1):115-128
Pine seedlings are able to accumulate chlorophylls and develop green plastids in a light-independent manner. In this work, we have characterized ferredoxin-dependent glutamate synthase (EC 1.4.7.1; Fd-GOGAT), a key enzyme in nitrogen interconversion during this process. Fd-GOGAT has been purified about 170-fold from cotyledons of maritime pine (Pinus pinaster). As occurs in angiosperms, the native enzyme is a single polypeptide with an apparent molecular mass of 163–168 kDa that is confined to the chloroplast stroma. Polyclonal antibodies generated against the purified enzyme were used to immunoscreen a gt11 expression library from Scots pine (Pinus sylvestris) seedlings and partial cDNA clones were isolated and characterized. The clone with the longest cDNA insert (pGOP44) contained the codification for the C-terminal (550 amino acids) of the pine Fd-GOGAT polypeptide. Immunological cross-reactivity and comparative amino sequence analysis revealed that Fd-GOGAT is a well conserved protein in higher plants. Western blot analyses showed that protein was expressed in chloroplast-containing pine tissues and this expression pattern was not affected by exogenously supplied nitrogen. Fd-GOGAT mRNA, polypeptide and enzyme activity accumulated in substantial amounts in dark-grown pine seedlings. The presence of a functional Fd-GOGAT may be important to provide the required glutamate for the biosynthesis of nitrogen compounds during chloroplast biogenesis in the dark. 相似文献
73.
Ype de Jong Johannes Henricus Francisca Maria Pinckaers Robin Marco ten Brinck Augustinus Aizo Beent Lycklama à Nijeholt Olaf Matthijs Dekkers 《PloS one》2014,9(7)
Background
It is suggested that the body posture during urination can influence urodynamic parameters in patients with Lower Urinary Tract Symptoms (LUTS) to an extent approaching pharmacological interventions. In this article, the influence of body position during micturition on maximum urinary flow rate (Qmax), voiding time (TQ) and post-void residual volume (PVR) in healthy males and patients with LUTS is analyzed by means of a systematic review and meta-analysis.Evidence Acquisition
A systematic search was conducted in 14 medical databases. Studies comparing urodynamic parameters in standing versus sitting position were eligible for inclusion. Studies were stratified according to health status of included male participants: healthy individuals and patients with LUTS. Standardized mean differences for Qmax, TQ and PVR were pooled in a random effects model.Results
Eleven articles were included. In men with LUTS, a significantly lower PVR (−24.96 ml; 95%CI −48.70 to −1.23) was shown in sitting position compared to standing. In accordance, Qmax was increased (1.23 ml/s; 95%CI −1.02 to 3.48), and TQ was decreased (−0.62 s; 95%CI −1.66 to 0.42) in sitting position, although these differences did not reach statistical significance. In healthy men, Qmax (0.18 ml/s; 95% CI −1.67 to 2.02), TQ (0.49 s; 95%CI −3.30 to 4.27) and PVR (0.43 ml; 95%CI −0.79 to 1,65) were similar in sitting and standing position.Conclusion
For healthy men, no difference is found in any of the urodynamic parameters. In patients with LUTS, the sitting position is linked with an improved urodynamic profile. 相似文献74.
75.
Elena SF Bedhomme S Carrasco P Cuevas JM de la Iglesia F Lafforgue G Lalić J Pròsper A Tromas N Zwart MP 《Molecular plant-microbe interactions : MPMI》2011,24(3):287-293
Over the years, agriculture across the world has been compromised by a succession of devastating epidemics caused by new viruses that spilled over from reservoir species or by new variants of classic viruses that acquired new virulence factors or changed their epidemiological patterns. Viral emergence is usually associated with ecological change or with agronomical practices bringing together reservoirs and crop species. The complete picture is, however, much more complex, and results from an evolutionary process in which the main players are ecological factors, viruses' genetic plasticity, and host factors required for virus replication, all mixed with a good measure of stochasticity. The present review puts emergence of plant RNA viruses into the framework of evolutionary genetics, stressing that viral emergence begins with a stochastic process that involves the transmission of a preexisting viral strain into a new host species, followed by adaptation to the new host. 相似文献
76.
Sheila Unger Maria?W. Górna Antony Le?Béchec Sonia Do?Vale-Pereira Maria?Francesca Bedeschi Stefan Geiberger Giedre Grigelioniene Eva Horemuzova Faustina Lalatta Ekkehart Lausch Cinzia Magnani Sheela Nampoothiri Gen Nishimura Duccio Petrella Francisca Rojas-Ringeling Akari Utsunomiya Bernhard Zabel Sylvain Pradervand Keith Harshman Belinda Campos-Xavier Luisa Bonafé Giulio Superti-Furga Brian Stevenson Andrea Superti-Furga 《American journal of human genetics》2013,92(6):990-995
Kenny-Caffey syndrome (KCS) and the similar but more severe osteocraniostenosis (OCS) are genetic conditions characterized by impaired skeletal development with small and dense bones, short stature, and primary hypoparathyroidism with hypocalcemia. We studied five individuals with KCS and five with OCS and found that all of them had heterozygous mutations in FAM111A. One mutation was identified in four unrelated individuals with KCS, and another one was identified in two unrelated individuals with OCS; all occurred de novo. Thus, OCS and KCS are allelic disorders of different severity. FAM111A codes for a 611 amino acid protein with homology to trypsin-like peptidases. Although FAM111A has been found to bind to the large T-antigen of SV40 and restrict viral replication, its native function is unknown. Molecular modeling of FAM111A shows that residues affected by KCS and OCS mutations do not map close to the active site but are clustered on a segment of the protein and are at, or close to, its outer surface, suggesting that the pathogenesis involves the interaction with as yet unidentified partner proteins rather than impaired catalysis. FAM111A appears to be crucial to a pathway that governs parathyroid hormone production, calcium homeostasis, and skeletal development and growth. 相似文献
77.
We have identified a membrane-active region in the HCV NS5A protein by performing an exhaustive study of membrane rupture induced by a NS5A-derived peptide library on model membranes having different phospholipid compositions. We report the identification in NS5A of a highly membranotropic region located at the suggested membrane association domain of the protein. We report the binding and interaction with model membranes of two peptides patterned after this segment, peptides 1A and 1B, derived from the strains 1a_H77 and 1b_HC-4J respectively. We show that they insert into phospholipid membranes, interact with them, and are located in a shallow position in the membrane. The NS5A region where this segment resides might have an essential role in the membrane replication and/or assembly of the viral particle through the modulation of the replication complex, and consequently, directly implicated in the HCV life cycle. 相似文献
78.
Germán Diestre Ortín Vanessa González Sequero Núria Collell Domènech Francisca Pérez López Pablo Hernando Robles 《Revista espa?ola de geriatría y gerontología》2013
Introduction
Advanced care planning (ACP) helps in make decisions on the health problems of people who have lost the capacity for informed consent. It has proven particularly useful in addressing the end of life. The aim of this study was to determine the prevalence of ACP in patients with severe chronic diseases.Material and methods
Review of medical records of patients with dementia, amyotrophic lateral sclerosis, Parkinson's disease, chronic obstructive pulmonary disease or interstitial lung disease, heart failure, chronic kidney disease on dialysis and cancer, all in advanced stages. We collected data on living wills or registered prior decisions by the physician according to clinical planned.Results
A total of 135 patients were studied. There was a record of ACP in 22 patients (16.3%). In most of them it was planned not to start any vital treatment in the event of high risk of imminent death and lacking the ability to make decisions. Only two patients were had a legal living will.Conclusion
The registration of ACP is relatively low, and this can affect decision-making in accordance with the personal values of patients when they do not have the capacity to exercise informed consent. 相似文献79.
Diana Pinto Stefania Sut Stefano Dall'Acqua Cristina Delerue-Matos Francisca Rodrigues 《化学与生物多样性》2021,18(3):e2000925
Hardy kiwifruit (Actinidia arguta) is a highly appreciated exotic fruit endowed with outstanding bioactive compounds. The present work proposes to characterize the pulp from A. arguta organic fruits, emphasizing its radicals scavenging capacity and effects on intestinal cells (Caco-2 and HT29-MTX). The physicochemical properties and phenolic profile were also screened. The total phenolic and flavonoid contents (TPC and TFC, respectively) of pulp were 12.21 mg GAE/g on dry weight (DW) and 5.92 mg CE/g DW, respectively. A high antioxidant activity was observed (FRAP: 151.41 μmol FSE/g DW; DPPH: 12.17 mg TE/g DW). Furthermore, the pulp did not induce a toxic effect on Caco-2 and HT29-MTX cells viability up to 1000 μg/mL. Regarding in vitro scavenging capacity, the pulp revealed the highest scavenging power against NO. (IC50=3.45 μg/mL) and HOCl (IC50=12.77 μg/mL). These results emphasize the richness of A. arguta fruit pulp to be used in different food products. 相似文献
80.
Laura David Peter Schwan Martin Lobedann Sven-Oliver Borchert Bastian Budde Maike Temming Mike Kuerschner Francisca Maria Alberti Aguilo Kerstin Baumarth Tobias Thüte Benjamin Maiser Andreas Blank Viktorija Kistler Nils Weber Heiko Brandt Martin Poggel Klaus Kaiser Karl Geisen Felix Oehme Gerhard Schembecker 《Biotechnology and bioengineering》2020,117(4):1024-1036
Continuous processing is the future production method for monoclonal antibodies (mAbs). A fully continuous, fully automated downstream process based on disposable equipment was developed and implemented inside the MoBiDiK pilot plant. However, a study evaluating the comparability between batch and continuous processing based on product quality attributes was not conducted before. The work presented fills this gap comparing both process modes experimentally by purifying the same harvest material (side-by-side comparability). Samples were drawn at different time points and positions in the process for batch and continuous mode. Product quality attributes, product-related impurities, as well as process-related impurities were determined. The resulting polished material was processed to drug substance and further evaluated regarding storage stability and degradation behavior. The in-process control data from the continuous process showed the high degree of accuracy in providing relevant process parameters such as pH, conductivity, and protein concentration during the entire process duration. Minor differences between batch and continuous samples are expected as different processing conditions are unavoidable due to the different nature of batch and continuous processing. All tests revealed no significant differences in the intermediates and comparability in the drug substance between the samples of both process modes. The stability study of the final product also showed no differences in the stability profile during storage and forced degradation. Finally, online data analysis is presented as a powerful tool for online-monitoring of chromatography columns during continuous processing. 相似文献