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   2713篇
  免费   317篇
  国内免费   1篇
  2021年   33篇
  2020年   24篇
  2019年   22篇
  2017年   39篇
  2016年   52篇
  2015年   81篇
  2014年   83篇
  2013年   124篇
  2012年   126篇
  2011年   119篇
  2010年   80篇
  2009年   70篇
  2008年   97篇
  2007年   104篇
  2006年   104篇
  2005年   96篇
  2004年   93篇
  2003年   77篇
  2002年   68篇
  2001年   71篇
  2000年   91篇
  1999年   64篇
  1998年   36篇
  1997年   46篇
  1996年   40篇
  1995年   35篇
  1994年   27篇
  1993年   39篇
  1992年   63篇
  1991年   41篇
  1990年   50篇
  1989年   55篇
  1988年   49篇
  1987年   49篇
  1986年   40篇
  1985年   40篇
  1984年   41篇
  1983年   34篇
  1982年   45篇
  1981年   33篇
  1980年   31篇
  1979年   59篇
  1978年   49篇
  1977年   42篇
  1976年   27篇
  1975年   33篇
  1974年   29篇
  1973年   22篇
  1971年   20篇
  1968年   21篇
排序方式: 共有3031条查询结果,搜索用时 31 毫秒
1.
J L Reynolds 《CMAJ》1993,148(2):130-131
  相似文献   
2.
3.
4.
Experiments were performed on four cats to characterize fasting gastric and small bowel motility and to assess the role of extrinsic vagal innervation in the control of that motor activity. A multilumen manometry tube was positioned to record pressure changes from the proximal small bowel and stomach. Transient vagal nerve blockade was accomplished by cooling the cervical vagosympathetic nerve trunks, previously isolated in skin loops on each side of the neck. Two characteristic patterns of basal activity were documented in the stomach: (i) regular phasic contractions of variable amplitude in the body of the stomach; and (ii) infrequent, irregular contractions of high amplitude in the distal antrum. In the duodenum, two predominant activity patterns were noted: (i) periods of continuous irregular activity; and (ii) irregular clusters of contractions separated by quiescent intervals. No typical migrating motor complex activity was seen in the basal gastric or small bowel recordings. Bilateral vagal blockade did not consistently change the general pattern of gastric or small bowel activity, but did appear to reduce gastric contractile activity, as measured by motility indices. We conclude that extrinsic vagal innervation does not play a major role in the control of fasting feline gastric and duodenal motility.  相似文献   
5.
6.
7.
8.
Polypeptide components of an excitable plasma membrane   总被引:4,自引:0,他引:4  
  相似文献   
9.
Levels of amide and ureide biogenic enzymes were compared in the plant cytosol fractions of root nodules from soybean ( Glycine max L. Merr., cv. Williams), pintobean ( Phaseolus vulgaris L. cv. Pinto) and Lupin ( Lupinus angustifolius L. cv. Frost). Enzymes of purine oxidation were found to be present in significant quantities only in ureide-transporting pintobean and soybean nodules. The levels of these enzymes were low in lupin, but this amide-exporter had significantly higher levels of asparagine synthetase. Enzymes of de novo purine biosynthesis and glycine biosynthesis were present at higher levels in pintobean and soybean, consistent with a role for de novo purine biosynthesis in ureide biogenesis. The low levels of these enzymes in lupin are consistent with a role in general purine and amino acid metabolism in these nodules, not directly related to the synthesis of transport compounds for fixed atmospheric nitrogen. Amino acid concentrations in soybean, pintobean and lupin nodules reflected the metabolic differences between amide and ureide plants. The comparative data presented are consistent with a pathway of ureide biogenesis using glutamine, glutamate and aspartate synthesized via reactions catalyzed by glutamine synthetase, glutamate synthase and aspartate aminotransferase in the de novo synthesis of purines followed by oxidation of these purines to produce the ureides allantoin and allantoic acid.  相似文献   
10.
The neuropsychiatric states of 50 patients with vitamin B12 deficiency and 34 patients with folate deficiency presenting with megaloblastosis in a general hospital were examined and compared. Abnormalities of the nervous system were found in two-thirds of both groups. Peripheral neuropathy was the most common condition associated with vitamin B12 deficiency and affective disorder with folate deficiency. The proportions of patients with organic mental change were similar in the two groups. Subacute combined degeneration of the cord was an uncommon complication and occurred only in the patients with vitamin B12 deficiency. There was no relation between haematological and neuropsychiatric abnormalities. The neuropsychiatry of megaloblastic anaemia seen in this study of patients presenting to haematologists or general physicians contrasts with that reported previously, before haematological techniques for separating the two deficiencies were introduced.  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