全文获取类型
收费全文 | 1767篇 |
免费 | 79篇 |
专业分类
1846篇 |
出版年
2024年 | 6篇 |
2023年 | 17篇 |
2022年 | 40篇 |
2021年 | 61篇 |
2020年 | 49篇 |
2019年 | 50篇 |
2018年 | 49篇 |
2017年 | 56篇 |
2016年 | 76篇 |
2015年 | 80篇 |
2014年 | 96篇 |
2013年 | 120篇 |
2012年 | 131篇 |
2011年 | 138篇 |
2010年 | 90篇 |
2009年 | 70篇 |
2008年 | 98篇 |
2007年 | 105篇 |
2006年 | 89篇 |
2005年 | 77篇 |
2004年 | 71篇 |
2003年 | 51篇 |
2002年 | 47篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 11篇 |
1972年 | 3篇 |
1971年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有1846条查询结果,搜索用时 15 毫秒
61.
Bicer M Akil M Sivrikaya A Kara E Baltaci AK Mogulkoc R 《Journal of physiology and biochemistry》2011,67(4):511-517
The present study aims to examine the effect of supplementation of zinc on the distribution of various elements in the sera
of diabetic rats subjected to an acute swimming exercise. A total of 80 Sprague–Dawley-type adult male rats were equally allocated
to one of eight groups: Group 1, general; Group 2, zinc-supplemented; Group 3, zinc-supplemented diabetic; Group 4, swimming
control; Group 5, zinc-supplemented swimming; Group 6, zinc-supplemented diabetic swimming; Group 7, diabetic swimming; and
Group 8, diabetes. The rats were injected with 40 mg/kg/day subcutaneous streptozotocin (STZ) twice, with a 24-h interval
between two injections. Zinc was supplemented at a dose of 6 mg/kg/day (ip) for 4 weeks. Blood samples were collected at the
end of the 4-week study, and serum levels of lead, cobalt, molybdenum, chrome, sulfur, magnesium, manganese, sodium, potassium,
phosphorus, copper, iron, calcium, zinc, and selenium (mg/L) were determined with atomic emission. The lowest molybdenum,
chrome, copper, iron, potassium, magnesium, sodium, phosphorus, lead, selenium, and zinc values were obtained in Group 7 and
8. These same parameters were higher in the swimming exercise group (Group 4), relative to all other groups. The values in
zinc-supplemented groups were found lower than the values in Group 4, but higher than those in Group 6 and 7. The results
obtained from the study demonstrate that acute swimming exercise and diabetes affect the distribution of various elements
in the serum, while zinc supplementation can prevent the negative conditions associated with both exercise and diabetes. 相似文献
62.
Yilmaz N Vural H Yilmaz M Sutcu R Sirmali R Hicyilmaz H Delibas N 《Journal of receptor and signal transduction research》2011,31(3):214-219
Calorie restriction (CR) has attracted increased interest since CR enhances lifespan and alters age-related decline in hippocampal-dependent cognitive functions. Obesity is associated with poor neurocognitive outcome including impaired hippocampal synaptic plasticity and cognitive abilities such as learning and memory. N-Methyl-D-aspartate receptors (NMDARs) are linked to hippocampal-dependent learning and memory, which may be stabilized by CR. In the present study, we aimed to establish the effects of CR on NMDARs in CA1 region of hippocampus in obese and non-obese rats. In addition, malondialdehyde (MDA) levels were determined as a marker for lipid peroxidation (LPO) in hippocampus. Four groups were constituted as control group (C, n?=?9), obese group (OB, n?=?10), obese calorie-restricted group (OCR, n?=?9), and non-obese calorie-restricted group (NCR, n?=?10). OCR and NCR were fed with a 60% CR diet for 10 weeks. After 10 weeks of CR, the MDA levels significantly decreased in the calorie-restricted groups. Obesity caused significant decreases in NR2A and NR2B subunit expressions in the hippocampus. The hippocampal NR2A and NR2B levels significantly increased in the OCR group compared with the OB group (P?0.05). In contrast, the hippocampal NR2A and NR2B levels significantly decreased in the NCR group compared with the C group (P?0.05). Oxidative stress can be prevented by CR, and these data may provide a molecular and cellular mechanism by which CR may regulate NMDAR-mediated response against obesity-induced changes in the hippocampus. 相似文献
63.
In this work, modified carboxymethylcellulose (CMC) was used as a new support material for production of ethanol. Crosslinked
graft copolymers of CMC with N-vinyl-2-pyrrolidone (N-VP) were prepared in different grafting yields. The beads material was characterized by means of fourier transform infrared
spectroscopy (FT-IR), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and swelling experiment.
Saccharomyces cerevisiae was immobilized using entrapment method in the graft copolymers of carboxymethylcellulose-g-poly(N-vinyl-2-pyrrolidone) (CMC-g-PVP)
for ethanol fermentation. The effects of grafting yield, initial glucose concentration and crosslinker concentration on the
yield of ethanol process were investigated. Reusability of the immobilized yeasts was investigated and found that the materials
can be used four times without losing their activity. Ethanol production increased to 59.3 g/L from 46.4 g/L when percentage
of N-VP in the graft copolymer was increased. The highest ethanol productivity was found to be 1.75–2.25 g/L h. Fermentation time
decreased with the decreasing of crosslinker concentration. The results suggest that the proposed method for immobilization
of Saccharomyces cerevisiae has potential in industrial applications for ethanol process. 相似文献
64.
Methods described in this paper are confined to in vitro dedifferentiated plant cell suspension cultures, which are convenient for the large-scale production of fine chemicals in bioreactors and for the study of cellular and molecular processes, as they offer the advantages of a simplified model system for the study of plants when compared with plants themselves or differentiated plant tissue cultures. The commonly used methods of initiation of a callus from a plant and subsequent steps from callus to cell suspension culture are presented in the protocol. This is followed by three different techniques for subculturing (by weighing cells, pipetting and pouring cell suspension) and four methods for growth measurement (fresh- and dry-weight cells, dissimilation curve and cell volume after sedimentation). The advantages and disadvantages of the methods are discussed. Finally, we provide a two-step (controlled rate) freezing technique also known as the slow (equilibrium) freezing method for long-term storage, which has been applied successfully to a wide range of plant cell suspension cultures. 相似文献
65.
Mustafa Karakse 《Plant Diversity》2022,44(6):577
This study aims to identify medicinal plants traditionally used to treat diseases by local people living in Güce district, north-eastern Turkey. The study was carried out between 2018 and 2021 using a two-part semi-structured, open-ended questionnaire with 165 local people. Data were analysed using use-report, frequency of citation, and informant consensus factor. Informants identified 128 vascular medicinal plant taxa belonging to 54 families and 106 genera. The most common plant taxa belong to Rosaceae (16 taxa/12.5%), Asteraceae (12 taxa/9.4%), and Lamiaceae (9 taxa/7%) families. The most frequently used preparation method reported was decoction (39.8%); the most commonly utilized plant parts were leaves (40.3%). Statistical analysis reveals that women in Güce district (df = 163, p = 0.043 < 0.05) possess the most traditional knowledge. The highest frequency of citation (61) and use report (92) were recorded for Tilia rubra subsp. caucasica, and the highest informant consensus factors were cited for respiratory system disorders (0.86), digestive system disorders (0.73), and skin disorders (0.71). This study reported nine plant taxa as medicinal plants for the first time, and documented a total of 293 new therapeutic uses. However, the study indicates that the transfer of traditional knowledge to future generations is limited (F = 3.355, p = 0.020). Action should be taken as soon as possible to preserve existing traditional knowledge and to ensure its transfer to future generations. 相似文献
66.
Mustafa alk Yildizhan Sengul Gurkan Zahide Mail Deniz Hintoglu Msrloglu Naile Fevziye Hafize Uzun 《Journal of Medical Biochemistry》2022,41(4):534
BackgroundTo investigate the relationship between irisin levels in serum and classification of subtype of acute ischemic stroke, National Institutes of Health Stroke Scale (NIHSS) and Modified Rankin Score (mRS) at the time of discharge from the hospital in Turkish patients who had their first acute ischemic stroke (AIS).MethodsSerum irisin levels were measured using enzyme linked immunosorbent assay (ELISA) 180 patients who applied to emergency department with the diagnosis of AIS from May 2021 to November 2021.ResultsA significant relationship was found between serum irisin levels and ischemic stroke aetiological factors (TAOST) (p=0.017). Increased serum irisin levels were detected in patients without neurological deficits with localization value than those with it (p<0.01). Serum irisin levels also have a negative correlation with high-density lipoprotein (HDL) value in ischemic stroke (r: -0.272, p<0.01).ConclusionsHigh serum irisin levels found in patients with stroke attributed to small vessel disease and in patients with ischemic stroke in whom we did not find any neurological deficits with a localization value. The results of the study show that serum irisin levels have an important role in the etiology of ischemic stroke. Although the question how the irisin is involved in the course of ischemic stroke and what the clinical reflection has not been answered, these findings are a pioneering study on this subject. 相似文献
67.
Chorismate derived C6C1 compounds in plants 总被引:6,自引:0,他引:6
68.
69.
A peptide nucleic acid/peptide amphiphile conjugate (PNA-PA) that self-assembles into fiber-shaped nanostructures was designed to bind oligonucleotides with high affinity and specificity. Oligonucleotide binding to PNA-PA nanofibers was studied using fluorescence polarization, and thermal stability was examined by UV-vis measurement of duplex melting temperatures. The self-assembled PNA-PA DNA system was observed to bind more strongly than the corresponding DNA-DNA duplex. We also observed single base specificity with a 16 degrees C in thermal stability. As expected from the previous PNA studies, PNA-PA RNA binding is also stronger than the corresponding RNA-RNA duplex. 相似文献
70.
Cowan CW Shao YR Sahin M Shamah SM Lin MZ Greer PL Gao S Griffith EC Brugge JS Greenberg ME 《Neuron》2005,46(2):205-217
Ephrin signaling through Eph receptor tyrosine kinases can promote attraction or repulsion of axonal growth cones during development. However, the mechanisms that determine whether Eph signaling promotes attraction or repulsion are not known. We show here that the Rho family GEF Vav2 plays a key role in this process. We find that, during axon guidance, ephrin binding to Ephs triggers Vav-dependent endocytosis of the ligand-receptor complex, thus converting an initially adhesive interaction into a repulsive event. In the absence of Vav proteins, ephrin-Eph endocytosis is blocked, leading to defects in growth cone collapse in vitro and significant defects in the ipsilateral retinogeniculate projections in vivo. These findings suggest an important role for Vav family GEFs as regulators of ligand-receptor endocytosis and determinants of repulsive signaling during axon guidance. 相似文献