首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   268篇
  免费   4篇
  2022年   2篇
  2021年   1篇
  2020年   1篇
  2019年   2篇
  2017年   2篇
  2016年   3篇
  2015年   8篇
  2014年   12篇
  2013年   20篇
  2012年   17篇
  2011年   12篇
  2010年   14篇
  2009年   9篇
  2008年   8篇
  2007年   9篇
  2006年   11篇
  2005年   12篇
  2004年   8篇
  2003年   14篇
  2002年   11篇
  2001年   10篇
  2000年   7篇
  1999年   5篇
  1998年   4篇
  1997年   1篇
  1996年   1篇
  1995年   5篇
  1994年   1篇
  1993年   1篇
  1992年   6篇
  1991年   3篇
  1990年   4篇
  1989年   6篇
  1988年   5篇
  1987年   5篇
  1986年   4篇
  1985年   6篇
  1984年   7篇
  1983年   3篇
  1982年   1篇
  1980年   2篇
  1979年   3篇
  1978年   1篇
  1976年   1篇
  1973年   1篇
  1971年   2篇
  1967年   1篇
排序方式: 共有272条查询结果,搜索用时 171 毫秒
71.
To quantitatively evaluate the effect of insulin on cardiac sympathetic nerve activity (SNA) and analyze clinical factors associated with insulin sensitivity for the regulation of SNA in diabetics, 29 Japanese type 2 diabetics without neuropathy were recruited. A 2-h control study and a 2-h hyperinsulinemic euglycemic glucose clamp study were performed. From the power spectral analysis of R-R intervals on ECG during both studies, two major components, the low-frequency (LF) and the high-frequency component (HF), were obtained. Then %LF was calculated as LF/(LF +HF), and the ratio of the average %LF during the last 30 min of the clamp or the control to the average %LF for the entire time for clamp or control (R-%LF) was used as a marker of changes in SNA. R-%LF was significantly higher during the clamp than in the control (1.07 +/- 0.04 vs. 1.03 +/- 0.03, P < 0.05). High responders (individual R-%LF during clamp > or = mean + 2SD in control) showed a higher basal mean blood pressure (BP) before the clamp (89 +/- 3 vs. 82 +/- 2, P < 0.03) but not a higher glucose infusion rate (GIR) compared with low responders (相似文献   
72.
The relation between the uptake of atmospheric CO(2) and insect's production of silk fiber has not yet been reported. Here, we provide the first quantitative demonstrations that four species of silkworms (Bombyx mori, Samia cynthia ricini, Antheraea pernyi, and Antheraea yamamai) and a silk-producing spider (Nephila clavata) incorporate atmospheric CO(2) into their silk fibers. The abundance of (13)C incorporated from the environment was determined by mass spectrometry and (13)C NMR measurements. Atmospheric CO(2) was incorporated into the silk fibers in the carbonyl groups of alanine, aspartic acid, serine, and glycine and the C(gamma) of aspartic acid. We show a simple model for the uptake of atmospheric CO(2) by silkworms. These results will demonstrate that silkworm has incorporated atmospheric CO(2) into silk fiber via the TCA cycle; however, the magnitude of uptake into the silk fibers is smaller than that consumed by the photosynthesis in trees and coral reefs.  相似文献   
73.
A cDNA containing the gene for Japanese flounder IgD consisted of 3240 bp encoding 998 amino acid residues. The amino acid sequence of the constant region of Japanese flounder IgD shares 38-80% identity with the sequences of previously reported teleost IgDs. The structure of the constant region of Japanese flounder IgD, which contains the micro1, delta1, delta2, delta3, delta4, delta5, delta6, delta7, and TM regions, is similar to the structures of the constant regions of the IgDs of channel catfish and Atlantic salmon. Southern blot hybridisation showed that the Japanese flounder IgD gene exists as a single locus. The Japanese flounder IgD gene was mainly detected in peripheral blood leucocytes (PBLs) and small amounts were detected in the spleen, head and trunk kidney, although IgM mRNA was detected in similar amounts in PBLs, the head kidney, and spleen. The copy number of IgM mRNA in Japanese flounder PBL was 56-fold higher than that of IgD.  相似文献   
74.
(1S,2R)-1-Phenyl-2-[(S)-1-aminopropyl]-N,N-diethylcyclopropanecarboxamide (PPDC, 4a), which is a conformationally restricted analogue of antidepressant milnacipran [(±)-1], is a new class of potent noncompetitive NMDA receptor antagonists. A series of PPDC analogues modified at the 1-phenyl moiety, that is, the analogue 6 lacking 1-phenyl group, the 1-(fluorophenyl) analogues 4b,c,d, the 1-(methylphenyl) analogues 4e–g and the 1-(naphthyl) analogues 4h,i were synthesized. Analogue 6, lacking the 1-phenyl group, was completely inactive showing that the aromatic moiety is essential for the NMDA receptor binding. Among the analogues synthesized, the 1-o-fluorophenyl and 1-m-fluorophenyl analogues 4b and 4c showed potent affinities for the NMDA receptor [IC50=0.16±0.001 μM (4b), 0.15±0.02 μM (4c)], which were improved to some extent compared to those of the parent compound PPDC (IC50=0.20±0.02 μM). On the other hand, compounds 4b and 4c showed none of the 5-HT-uptake inhibitory effect, while PPDC turned out to be a weak 5-HT-uptake inhibitor.  相似文献   
75.
76.
Researchers studied the convergence of the vertical posterior semicircular canal (PC), saccular nerves (SAC), utricular nerves (UT), and horizontal semicircular canal nerves (HC) on single vestibular neurons. The vestibular neurons were categorized by their innervating targets. Vestibular neurons were classified as vestibulospinal proper neurons (VS), vestibulo-ocular proper neurons (VO), vestibulo-oculo-spinal neurons sending axon collaterals to the extraocular motoneuron pools and spinal cord (VOS), and vestibular nucleus neurons without axons to the oculomotor nuclei or the spinal cord (V). Results indicate that the percentage of convergence of VS neurons was higher that that of neurons sending axons to the oculomotor nuclei (VO and VOS). They conclude that the convergence of canal and otolith inputs likely contributes mainly to vestibulospinal reflexes by sending inputs to the neck and other muscles during head inclination, which creates the combined stimuli of angular and linear acceleration.  相似文献   
77.
BACKGROUND: The helper-dependent adenovirus (HDAd) vector is less immunogenic and has a larger cloning capacity of up to 37 kb enough to carry the full-length dystrophin cDNA. However, high and long-term expression of dystrophin transduced to mature muscle still remains difficult. One of the main reasons for this is that the expression of the coxsackievirus and adenovirus receptor (CAR) is very low in mature muscle. METHODS: We have constructed two different HDAd vectors. One contains the LacZ and the murine full-length dystrophin expression cassette (HDAdLacZ-dys), and the other is a new, improved vector containing the CAR and the dystrophin expression cassette (HDAdCAR-dys). RESULTS: We initially demonstrated high dystrophin expression and prevention of the dystrophic pathology in mdx muscle injected during the neonatal phase with HDAdLacZ-dys. Furthermore, we demonstrated that repeated injections of HDAdCAR-dys into mature muscle led to approximately nine times greater dystrophin-positive fibers in number than a single injection, thereby recovering the expression of dystrophin-associated proteins. This data has also shown that HDAdCAR-dys enabled administration of adenovirus (Ad) vector to the host with pre-existing immunity to the same serotype of Ad. CONCLUSIONS: Repetitive injections of the HDAd vector containing the CAR and the dystrophin expression cassette could improve the efficiency of subsequent dystrophin gene transfer to mature mdx muscle. This result suggests that our new HDAd vector will provide a novel gene therapy strategy for Duchenne muscular dystrophy, raising the prospects for gene therapy of other hereditary myopathies.  相似文献   
78.
A major QTL for grain dormancy, QPhs.ocs-3A.1, derived from the highly dormant wheat Zenkoujikomugi (Zen), has been identified in a study made under a controlled environment. Further investigations were needed to dissect the precise position and expression of QPhs.ocs-3A.1 under different field conditions because the ability to detect genetic loci for grain dormancy traits is compromised by environmental effects and genotype/environment interactions. Group 4 chromosomes have also been shown to be possible sites of QTLs for grain dormancy. The objectives of this study were (1) to locate additional molecular markers in the QPhs.ocs-3A.1 region, (2) to identify QTLs on the group 4 chromosomes and (3) to elucidate their combined effects. We examined the recombinant inbred lines (RILs) from a cross between Chinese Spring (CS) and Zen over a 3-year period in one location and 1 year in a different location. In an interval mapping study QPhs.ocs-3A.1 was mapped to within the 4.6 cM region flanked by Xbarc310 and Xbcd907 at the proximal end of the short arm of chromosome 3A. QPhs.ocs-3A.1 was confirmed to be the predominant dormancy QTL since it explained a large portion (11.6–44.8%) of the phenotypic variation, and was strongly displayed under dormancy-breaking conditions or at low germination temperatures. For QPhs.ocs-4A.1, identified on the long arm of chromosome 4A, and QPhs.ocs-4B.1, on the centromeric region of the long arm of Chr 4B, the LOD peak positions and the desirable allele were consistent between the trials, while the LOD scores and contribution to the phenotypic variation varied. Transgressive segregants were observed among the 125 RILs and most of them had a combination of the three alleles conferring a higher dormancy: the Zen alleles at QPhs.ocs-3A.1 and QPhs.ocs-4A.1 and the CS allele at QPhs.ocs-4B1. This demonstrated a combined effect of the desirable alleles on accelerating grain dormancy, with their total effect being superior to that of Zen.  相似文献   
79.

Background  

The genetic epidemiology of ischemic stroke remains relatively unstudied, and information about the genetic epidemiology of ischemic stroke in populations with significant minority representation is currently unavailable.  相似文献   
80.
BACKGROUND: Preoperative diagnosis of cases of renal calculus complicated with papillary renal cell carcinoma (RCC) by image analysis is usually difficult. CASE: A 50-year-old man who had a past history of renal calculus suffered from macrohematuria and abdominal pain for one month was admitted to our hospital. Ultrasonographic examination revealed a 4-cm tumor shadow in the right kidney; it was hypovascular in arteriography. Papillary cell clusters with abundant cytoplasm were found by the cytologic examination of voided urine. Their nuclei were oval and situated eccentrically in the cytoplasm. The nuclear/cytoplasmic ratio was increased. Fine, granular chromatin was distributed evenly, and the nuclear membrane was thin and nearly smooth. Several small nucleoli were evident. All these findings were indicative of a diagnosis of papillary RCC. Histology of nephrectomy specimens confirmed the diagnosis. CONCLUSION: Voided urine cytology can be useful for screening and follow-up of patients with papillary RCC.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号