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   1195篇
  免费   65篇
  国内免费   65篇
耳鼻咽喉   2篇
儿科学   58篇
妇产科学   29篇
基础医学   136篇
口腔科学   57篇
临床医学   165篇
内科学   248篇
皮肤病学   26篇
神经病学   41篇
特种医学   248篇
外科学   68篇
综合类   34篇
预防医学   56篇
眼科学   25篇
药学   92篇
中国医学   1篇
肿瘤学   39篇
  2021年   9篇
  2020年   4篇
  2019年   6篇
  2018年   4篇
  2017年   8篇
  2016年   11篇
  2015年   20篇
  2014年   21篇
  2013年   28篇
  2012年   25篇
  2011年   11篇
  2010年   30篇
  2009年   45篇
  2008年   27篇
  2007年   64篇
  2006年   31篇
  2005年   23篇
  2004年   26篇
  2003年   19篇
  2002年   34篇
  2001年   28篇
  2000年   26篇
  1999年   40篇
  1998年   69篇
  1997年   74篇
  1996年   76篇
  1995年   65篇
  1994年   43篇
  1993年   50篇
  1992年   17篇
  1991年   22篇
  1990年   20篇
  1989年   49篇
  1988年   28篇
  1987年   42篇
  1986年   22篇
  1985年   30篇
  1984年   24篇
  1983年   31篇
  1982年   23篇
  1981年   23篇
  1980年   21篇
  1979年   5篇
  1978年   9篇
  1977年   11篇
  1976年   6篇
  1975年   6篇
  1974年   3篇
  1966年   4篇
  1930年   2篇
排序方式: 共有1325条查询结果,搜索用时 15 毫秒
991.
A maintenance medium with a low oxidation-reduction (redox) potential, when gently bubbled with 5% oxygen in nitrogen or with air for various periods of time, gave a range of dissolved oxygen concentrations between 1.6 and 5.8 micrograms/l. Virulent Treponema pallidum (Nichols strain) inoculated into these media were assayed 24 and 48 hours later for motility and virulence and were compared with samples taken at zero time. Virulent T. pallidum survived best in the presence of 2.4 micrograms/l dissolved oxygen over a 48-hour period, which corresponded to a gaseous mixture of 3% oxygen in nitrogen. Higher concentrations of oxygen did not give significantly different results from anaerobic conditions over this period. Thus, until it can be grown in vitro, T. pallidum would appear to be a microaerophilic bacterium.  相似文献   
992.
Effect of breakfast cereals on short-term food intake   总被引:2,自引:0,他引:2  
We evaluated the effect of high-fiber cereals on short-term food intake. At 0730, 14 subjects ingested one of five cereals, plus milk and orange juice. At 1100 they were presented with a buffet lunch. There was a significant inverse correlation between fiber content of the cereals and energy intake at lunch. In a second study subjects ingested a very-high-fiber (VHF) cereal or a very-low-fiber (VLF) cereal. Fewer kcalories were ingested at lunch after ingestion of the VHF cereal than after ingestion of the VLF cereal. The degree of colonic microbial fermentation of the various cereals was evaluated by breath-hydrogen analysis. The higher-fiber cereals resulted in greater hydrogen production; however, this may not influence energy intake. The results of questionnaires that asked about hunger indicated that food intake can be reduced without the perception of feeling less hungry. Thus, we found that cereals containing relatively large quantities of dietary fiber may decrease short-term food intake.  相似文献   
993.
Alterations in intestinal permeability reflect one component of intestinal epithelial barrier function. The objective of this study was to assess the degree of derangement of intestinal permeability in critically ill patients and to investigate the relationship of this to markers of disease severity and sepsis. Sixteen patients admitted to the intensive care unit for a variety of problems were studied with the severity of illness and degree of sepsis recorded daily. A differential sugar absorption test, using lactulose and mannitol as markers, was performed, and in 10 patients this was repeated after an interval of between 4–11 days. The use of the lactulose/mannitol (L/M) ratio corrects for variables unrelated to permeability such as gastric emptying. The L/M ratio was significantly higher in patients (median 0.98) compared to normal controls (median 0.008). The ratios showed no relation to disease severity or sepsis. These results establish that increased intestinal permeability occurs in the general ICU patient but that it is not uniquely related to sepsis. The extent of this abnormality suggests that further study is required to show the various influences on this process.  相似文献   
994.
Administration of adenosine and agonists of the adenosine receptors to rats results in hypoactivity, hypothermia, muscle relaxation and antinociception. In the present study, we found that the adenosine ligand, N6-R-phenylisopropyladenosine (R-PIA), increased food intake in rats at a time in the day when rats normally eat very little food or none at all. Feeding was not reliably stimulated upon the first exposure to R-PIA, but was clearly increased following repeated administration of this agonist. Other adenosine agonists, namely 2-chloradenosine and 5'N-ethylcarboxamide adenosine, failed to alter feeding after a single injection or after repeated exposure. The adenosine antagonist, caffeine, did not block R-PIA's effect on food intake, whereas the opioid antagonist, naloxone, blocked R-PIA-induced eating. These data suggest that R-PIA stimulates feeding independent of the A1 or A2 adenosine receptors.  相似文献   
995.
Two independent samples that met DSM-III criteria for borderline personality disorder (BPD) were found to have similar patterns of object relations deficits as measured by group means and percentage of high scoring subjects on the four subscales of the Bell Objects Relation (OR) Inventory. Statistical comparison of the composite BPD group with affective, schizoaffective, and schizophrenic groups revealed that the pattern of OR deficits in BPD was significantly different from each of the other diagnostic groups. On the basis of scores from the Alienation subscale alone, BPD subjects could be distinguished from the other diagnostic groups with 77-82% predictive accuracy. The role of object relations deficits in BPD is discussed, along with potential contributions of the Bell OR Inventory to diagnostic efficiency.  相似文献   
996.
997.
The consumption of raw oysters contributes to food-borne diseases such as salmonellosis. Prevalence studies in our laboratory have shown that Salmonella spp. were present in 7.4% of U.S. market oysters, with the majority (78/101) of isolates being of the Salmonella enterica Newport serovar. E-tests were performed to assess the susceptibility of the S. Newport oyster isolates to antibiotics used for treatment of Salmonella infections. The oyster isolates were susceptible to Gentamicin, Trimethoprim/Sulphamethoxazole, and Ciprofloxacin, while for the most part they were resistant to Ampicillin and Tetracycline. Consistent with the uniform antibiotic susceptibility profile of these isolates, only three pulsed-field gel electrophoresis (PFGE) profiles were identified among the isolates. Of these three profiles, one was present in 63 of the 78 isolates, indicating not only the presence of S. Newport in oysters, but the predominance of a single PFGE type.  相似文献   
998.
Lymphocytes from patients with chronic lymphocytic leukaemia make large amounts of stable, rapidly labelled high molecular weight RNA, but ribosomal RNA methylation is normal. However, fewer ribosomes are available for protein synthesis than in normal lymphocytes.  相似文献   
999.
White blood cells from 22 patients with leukemia and lymphoma were studied for the presence of terminal deoxynucleotidyl transferase with a peroxidase-antiperoxidase method. The enzyme was detected in leukemic cells of 5 patients with acute lymphoblastic leukemia and 1 patient with chronic myelogenous leukemia, whereas 16 patients with different forms of leukemia or lymphoma were negative for this enzyme. Comparative studies using a biochemical and an indirect immunofluorescence assay revealed complete concordance between these three methods.  相似文献   
1000.
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