全文获取类型
收费全文 | 357篇 |
免费 | 16篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 14篇 |
2012年 | 36篇 |
2011年 | 38篇 |
2010年 | 15篇 |
2009年 | 17篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 37篇 |
2005年 | 23篇 |
2004年 | 14篇 |
2003年 | 12篇 |
2002年 | 17篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1981年 | 3篇 |
1978年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有373条查询结果,搜索用时 15 毫秒
261.
Dhaliwal S. S. Naresh R. K. Gupta R. K. Panwar A. S. Mahajan N. C. Singh Ravinder Mandal Agniva 《Reviews in Environmental Science and Biotechnology》2020,19(1):103-115
Reviews in Environmental Science and Bio/Technology - Measuring the influence of long-term agricultural tillage practices on soil organic carbon (SOC) is of great importance to farmers and... 相似文献
262.
Sarah M. Conklin Caroline A. Runyan Sherry Leonard Ravinder D. Reddy Matthew F. Muldoon Jeffrey K. Yao 《Prostaglandins, leukotrienes, and essential fatty acids》2010,82(2-3):111-119
Accumulating evidence finds a relative deficiency of peripheral membrane fatty acids in persons with affective disorders such as unipolar and bipolar depression. Here we sought to investigate whether postmortem brain fatty acids within the anterior cingulate cortex (BA-24) varied according to the presence of major depression at the time of death. Using capillary gas chromatography we measured fatty acids in a depressed group (n=12), and in a control group without lifetime history of psychiatric diagnosis (n=14). Compared to the control group, the depressed group showed significantly lower concentrations of numerous saturated and polyunsaturated fatty acids including both the n-3 and n-6 fatty acids. Additionally, significant correlations between age at death and precursor (or metabolites) in the n-3 fatty acid pathway were demonstrated in the depressed group but not in control subjects. In the n-6 fatty acid family, the ratio of 20:3(n-6)/18:2(n-6) was higher in patients than in control groups, whereas the ratio of 20:4(n-6)/20:3(n-6) was relatively decreased in patients. Lastly, a significant negative correlation between age and the ratio of 20:4(n-6) to 22:6(n-3) was found in patients, but not in controls. Taken together, decreases in 22:6(n-3) may be caused, at least in part, by the diminished formation of 20:5(n-3), which is derived from 20:4(n-3) through a Δ5 desaturase reaction. The present findings from postmortem brain tissue raise the possibility that an increased ratio of 20:4(n-6) to 22:6(n-3) may provide us with a biomarker for depression. Future research should further investigate these relationships. 相似文献
263.
264.
Jiang Y Bhargava V Lal HA Mittal RK 《American journal of physiology. Gastrointestinal and liver physiology》2011,301(6):G1014-G1019
Several studies from our laboratory show that axial stretch of the lower esophageal sphincter (LES) in an oral direction causes neurally mediated LES relaxation. Under physiological conditions, axial stretch of the LES is caused by longitudinal muscle contraction (LMC) of the esophagus. Because longitudinal muscle is composed of skeletal muscle in mice, vagal-induced LMC and LES relaxation are both blocked by pancuronium. We conducted studies in rats (thought to have skeletal muscle esophagus) to determine if vagus nerve-mediated LES relaxation is also blocked by pancuronium. LMC-mediated axial stretch on the LES was monitored using piezoelectric crystals. LES and esophageal pressures were monitored with a 2.5-Fr solid-state pressure transducer catheter. Following bilateral cervical vagotomy, the vagus nerve was stimulated electrically. LES, along with the esophagus, was harvested after in vivo experiments and immunostained for smooth muscle (smooth muscle α-actin) and skeletal muscle (fast myosin heavy chain). Vagus nerve-stimulated LES relaxation and esophageal LMC were reduced in a dose-dependent fashion and completely abolished by pancuronium (96 μg/kg) in six rats (group 1). On the other hand, in seven rats, LES relaxation and LMC were only blocked completely by a combination of pancuronium (group 2) and hexamethonium. Immunostaining revealed that the longitudinal muscle layer was composed of predominantly skeletal muscle in the group 1 rats. On the other hand, the longitudinal muscle layer of group 2 rats contained a significant amount of smooth muscle (P < 0.05). Our study shows tight coupling between axial stretch on the LES and relaxation of the LES, which suggests a cause and effect relationship between the two. We propose that the vagus nerve fibers that cause LMC induce LES relaxation through the stretch-sensitive activation of inhibitory motor neurons. 相似文献
265.
Mittal RK Bhargava V Lal H Jiang Y 《American journal of physiology. Gastrointestinal and liver physiology》2011,301(6):G1093-G1098
Myocardial blood flow occurs during the diastolic phase of the cardiac cycle, because myocardial contraction during the systolic phase impedes myocardial perfusion. Using laser Doppler perfusion technique, we studied the effect of esophageal contraction on the esophageal wall perfusion. Studies were conducted in rats. A laser Doppler probe was anchored to the esophageal wall, and wall perfusion was studied under various experimental conditions. Increase and decrease in the systemic blood pressure induced by different pharmacological agents was associated with the increase and decrease in the esophageal wall perfusion, respectively. Esophageal contractions induced by electrical stimulation of the vagus nerve and electrical stimulation of the muscle directly resulted in a reduction in the esophageal wall perfusion, in a dose-dependent fashion. Esophageal wall perfusion could be monitored by placing the Doppler probe on the esophageal mucosa or on the outside of the esophageal wall. Esophageal contraction impedes entry of blood into the esophageal wall. Future studies may investigate if ischemia of the esophageal wall induced by sustained esophageal contractions/esophageal spasm is the cause of esophageal pain symptoms in humans. 相似文献
266.
Rao AS Camilleri M Eckert DJ Busciglio I Burton DD Ryks M Wong BS Lamsam J Singh R Zinsmeister AR 《American journal of physiology. Gastrointestinal and liver physiology》2011,301(5):G919-G928
Mucosal barrier dysfunction contributes to gastrointestinal diseases. Our aims were to validate urine sugar excretion as an in vivo test of small bowel (SB) and colonic permeability and to compare permeability in patients with irritable bowel syndrome-diarrhea (IBS-D) to positive and negative controls. Oral lactulose (L) and mannitol (M) were administered with (99m)Tc-oral solution, (111)In-oral delayed-release capsule, or directly into the ascending colon (only in healthy controls). We compared L and M excretion in urine collections at specific times in 12 patients with IBS-D, 12 healthy controls, and 10 patients with inactive or treated ulcerative or microscopic colitis (UC/MC). Sugars were measured by high-performance liquid chromatography-tandem mass spectrometry. Primary endpoints were cumulative 0-2-h, 2-8-h, and 8-24-h urinary sugars. Radioisotopes in the colon at 2 h and 8 h were measured by scintigraphy. Kruskal-Wallis and Wilcoxon tests were used to assess the overall and pairwise associations, respectively, between group and urinary sugars. The liquid in the colon at 2 h and 8 h was as follows: health, 62 ± 9% and 89 ± 3%; IBS-D, 56 ± 11% and 90 ± 3%; and UC/MC, 35 ± 8% and 78 ± 6%, respectively. Liquid formulation was associated with higher M excretion compared with capsule formulation at 0-2 h (health P = 0.049; IBS-D P < 0.001) but not during 8-24 h. UC/MC was associated with increased urine L and M excretion compared with health (but not to IBS-D) at 8-24 h, not at 0-2 h. There were significant differences between IBS-D and health in urine M excretion at 0-2 h and 2-8 h and L excretion at 8-24 h. Urine sugars at 0-2 h and 8-24 h reflect SB and colonic permeability, respectively. IBS-D is associated with increased SB and colonic mucosal permeability. 相似文献
267.
268.
The large subunit of the U2 auxiliary factor (U2AF) recognizes the polypyrimidine tract (Py-tract) located adjacent to the 3' splice site to facilitate U2 snRNP recruitment. While U2AF is considered essential for pre-mRNA splicing, its requirement for splicing on a genome-wide level has not been analyzed. Using Solexa sequencing, we performed mRNA profiling for splicing in the Schizosaccharomyces pombe U2AF(59) (prp2.1) temperature-sensitive mutant. Surprisingly, our analysis revealed that introns show a range of splicing defects in the mutant strain. While U2AF(59) inactivation (nonpermissive) conditions inhibit splicing of some introns, others are spliced apparently normally. Bioinformatics analysis indicated that U2AF(59)-insensitive introns have stronger 5' splice sites and higher A/U content. Most importantly, features that contribute to U2AF(59) insensitivity of an intron unexpectedly reside in its 5'-most 30 nucleotides. These include the 5' splice site, a guanosine at position 7, and the 5' splice site-to-branch point sequence context. A differential requirement (similar to U2AF(59)) for introns may also apply to other general splicing factors (e.g., prp10). Our combined results indicate that U2AF insensitivity is a common phenomenon and that varied intron features support the existence of unrecognized aspects of spliceosome assembly. 相似文献
269.
Arun Bhardwaj Gurpreet Kaur Hittu Gupta Shilpa Vij Ravinder K. Malik 《World journal of microbiology & biotechnology》2011,27(3):591-602
In the present study 14 bacteriocinogenic strains of Enterococcus faecium isolated from dairy foods and faecal sample were evaluated for the presence of virulence determinants, production of biogenic
amines and their susceptibility to various antibiotics. Genetic diversity among them was evaluated by RAPD-PCR method. Further,
they were evaluated for their probiotic potential under in vitro trials. The efaAfm was the only virulence trait detected in all E. faecium and tyramine was the only biogenic amine produced by 9 tested strains. No strain was resistant to all antibiotics and for
some strains, multiple resistances were observed. E. faecium FH 99 showed highest good ability to tolerate acid and bile, while good bile salt hydrolase activity and were able to assimilate
cholesterol from growth media. These results suggest that the tested E. faecium are generally free from virulence traits and having good probiotic potential and may be exploit in dairy industry and probiotic
preparations. 相似文献
270.
Janine S. Croser Monika M. Lulsdorf Ravinder K. Grewal Kayley M. Usher Kadambot H. M. Siddique 《In vitro cellular & developmental biology. Plant》2011,47(3):357-368
Routine production of haploid plants has not been reported for any legume, despite the major role these species play in sustainable
farming systems and human nutrition. It is within this context that we report a protocol for the induction of haploid development
in chickpea (Cicer arietinum L.) using isolated microspore culture. The cultivars “Rupali”, “Narayen”, and “Kimberley Large” were identified as responsive
to isolated microspore culture. Flower bud length and microspore developmental stage were correlated for these cultivars.
Depending on the cultivar, buds 2.85–3.5 mm in length contained uninucleate microspores. Microspores from donor plants grown
in winter and spring were more responsive than those grown in summer. A cold treatment (4°C) of between 24 and 48 h enhanced
microspore response in winter- and spring-grown material but was not effective in summer-grown material. A medium developed
by the authors was effective for microspore induction and early-stage embryo development. The addition of hormones to this
medium was promotive of microspore induction in winter- and spring-grown material, but not in summer-grown material. The initial
haploid division predominantly occurred via symmetrical division of the vegetative nucleus. Further research is under way
to convert pro-embryos into plants. 相似文献