首页 | 官方网站   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   577篇
  免费   20篇
  国内免费   19篇
生物科学   616篇
  2023年   10篇
  2022年   18篇
  2021年   23篇
  2020年   9篇
  2019年   16篇
  2018年   4篇
  2017年   10篇
  2016年   15篇
  2015年   16篇
  2014年   23篇
  2013年   24篇
  2012年   22篇
  2011年   31篇
  2010年   25篇
  2009年   26篇
  2008年   24篇
  2007年   27篇
  2006年   35篇
  2005年   13篇
  2004年   19篇
  2003年   21篇
  2002年   19篇
  2001年   7篇
  2000年   7篇
  1999年   8篇
  1998年   5篇
  1997年   12篇
  1996年   5篇
  1995年   12篇
  1994年   3篇
  1993年   12篇
  1992年   7篇
  1991年   11篇
  1990年   8篇
  1989年   7篇
  1988年   3篇
  1987年   6篇
  1986年   6篇
  1985年   7篇
  1984年   10篇
  1983年   5篇
  1982年   10篇
  1981年   4篇
  1980年   6篇
  1979年   5篇
  1978年   5篇
  1976年   3篇
  1975年   5篇
  1974年   2篇
  1973年   4篇
排序方式: 共有616条查询结果,搜索用时 15 毫秒
611.
《Endocrine practice》2021,27(4):312-317
ObjectiveObesity is increasing worldwide, and certain endocrine disorders may contribute to weight gain. While several studies have examined the association between weight gain and prolactinomas, the results are conflicting. Therefore, this study aimed to determine if body mass index (BMI) is higher among those with prolactinomas than those without.MethodsWe identified patients ≥18 years of age referred to an endocrine clinic between 2008 and 2018 with newly diagnosed prolactinomas. We extracted the relevant information, and comparative data was obtained from the 2015-2016 National Health and Nutrition Examination Survey.ResultsIn total, 34 cases met the inclusion criteria. One third of the patients described weight gain at presentation. Those with prolactinomas had a significantly higher BMI than the National Health and Nutrition Examination Survey population (median BMI, 29.8 kg/m2 vs 28.3 kg/m2, P = .0048). When stratified by sex, only men with prolactinomas had an increased BMI compared with the controls. Moreover, those with prolactinomas had a higher prevalence of class II obesity (BMI ≥ 35 kg/m2) than the survey population (35% vs 18%, P = .01). Among the prolactinoma patients, a correlation was observed between BMI and log-transformed prolactin levels (R2 = 0.4, P = .0002).ConclusionWeight gain can be a presenting symptom for patients with newly diagnosed prolactinomas. Those with prolactinomas have a higher BMI and an increased prevalence of class II obesity. These findings suggest that patients should be counseled regarding weight issues related to prolactinomas at presentation and should be a consideration in the investigative and treatment algorithm of prolactinomas.  相似文献   
612.
Nutrient composition of liquid-shake cultures significantly influenced conidial production by five isolates of Rhynchosporium alismatis after 6 days at 25 C. Lima bean broth at pH 7.5 produced the most conidia (4.99 x 10 7 /ml). The zwitterionic buffers PIPES and HEPES did not significantly affect broth pH, but did significantly affect yield of conidia. pH per se did not appear to affect yield directly. The medium in which an isolate was grown had a significant effect on the virulence of the resulting conidia as measured by disease severity scores in leaf discs of Alisma lanceolatum after 3 and 13 days. There was a significant difference between isolates, produced in the same medium, in the subsequent rate of disease development. The correlation between image analysis of diseased leaf discs with visual assessment was low, and it was considered that automatic assessment of disease severity was not cost-effective with the equipment used. Isolate DAR 73158 and lima bean broth are considered to be the combination of choice for further studies to explore the fitness of conidia produced in small-scale biofermentors.  相似文献   
613.
Summary The indirect immunoperoxidase method was used to identify albumin in hepatocytes of rats before and after periods of starvation. All hepatocytes in fed rats contained a relatively large amount of nascent albumin. Overnight fasting reduced the number of hepatocytes with a large amount of albumin to primarily those surrounding terminal hepatic venules. These were estimated to be about 30% of the population. The other cells had only a slight amount of albumin. After 48 h of fasting all hepatocytes contained a low level of albumin.  相似文献   
614.
Interobserver reliabilities were determined for the triceps, biceps, subscapular, suprailiac, and abdominal skinfolds in 77 children, 9-24 months of age. Technical errors of measurement (replicate variances) and coefficients of variation were compared to data on 12-17-year-olds from the U.S. Health Examination Survey (HES) to 2.5-7-year-old Guatamalan children. Of the five skinfolds, the between-observer variation was not significantly different from zero in four; in the case of the biceps fold, F-ratio was significant at p less than .01. Errors of measurement are less for these data than for the HES or Guatemalan studies. This difference is attributed to the larger means of the older children and youth, as well as to the greater error of measurement shown to exist for larger skinfolds.  相似文献   
615.
Ecology and ovarian function among Lese women of the Ituri Forest, Zaire   总被引:1,自引:0,他引:1  
Ovarian function is examined in 35 Lese women inhabiting the Ituri Forest of northeastern Zaire over a period of 4 months through measurements of progesterone in saliva samples collected twice weekly. Ovulatory frequency is found to be only 56% on average, with a pattern of age variation similar to that observed in western women, though lower in level at each age. Average luteal progesterone levels of the Lese women are lower than those of Boston controls even if only ovulatory cycles are considered. Women with the poorest nutritional status, inferred from longitudinal weight changes and weight for height, show the greatest compromise of ovarian function, and the average ovulatory frequency of the whole sample declines in parallel with a period of weight loss over four months. It is suggested that low ovulatory frequency and luteal insufficiency contribute to the low fecundity of the Lese population and that nutritional status is likely to be one of the ecological factors modulating this effect.  相似文献   
616.
Alterations in growth caused by neonatal malnutrition may be mediated in part by changes in insulin-like growth factor (IGF) and IGF binding protein (IGFBP) expression. Since the neonatal rat cerebellum undergoes a transient, proliferative growth phase in the first two weeks of life, this structure was used to determine whether alterations in circulating and tissue IGFs and IGFBPs may mediate effects of impaired nutrition on the developing central nervous system. Gravid rats were placed on a 4% (protein-calorie deprived, D) or 20% (control, C) protein diets one day prior to delivery and allowed to nurse their pups postpartum. Pups nursing from D mothers received a limited volume of milk and were calorically deprived. Some litters of D pups were foster fed by C mothers from day 8 to day 13 to constitute a recovery group (R). Cerebellar weight, protein, and DNA content in D pups were less than C, p<0.001. In R pups, DNA and protein returned to C levels by day 13. Between days 6 and 13, serum IGF-I levels rose from 158±18 to 210±18 ng/ml in C but remained low in D (47±6 ng/ml and 25±3 ng/ml), respectively. In R pups, serum IGF-I partially recovered during this time, and increased from 49±5 to 110±7 ng/ml. In cerebellar extracts, IGF-I levels in both C and D were lower at 13 days than at 6 days, p<0.05 and p<0.005, respectively. IGF-I levels in C were similar at day 9 and day 11 and were consistently higher than D (11.84±0.83 vs 8.56±0.92 ng/g, p<0.02 C vs D). In R, IGF-I was reduced on day 11, but was similar to C on day 13. Serum IGF-II in D was lower than C, p<0.01, and did not increase in the R group. Cerebellar IGF-II was virtually undetectable in either group. Immunoprecipitation and ligand blotting studies of serum demonstrated that circulating levels of 32–34 K IGFBPs were increased 3–4 fold in D vs C, reflecting high levels of IGFBP-1 and/or-2, while levels of 24 K IGFBP-4 were lower in D vs C. By contrast, immunoprecipitation and ligand blotting of cerebellar extracts detected IGFBP-2 and-4, but did not detect IGFBP-1. Further, tissue levels of IGFBP-2 were not increased in D vs C, and levels of IGFBP-4 also were not markedly affected by nutritional deprivation. These results suggest that alterations in tissue content and the availability of IGF-I only modestly contributed to the effects of impaired nutrition in the developing central nervous system.  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-23

京公网安备 11010802026262号