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   104912篇
  免费   6063篇
  国内免费   12篇
  2023年   594篇
  2021年   1176篇
  2020年   1082篇
  2019年   1061篇
  2018年   2834篇
  2017年   2504篇
  2016年   3407篇
  2015年   4485篇
  2014年   4590篇
  2013年   6121篇
  2012年   7124篇
  2011年   6267篇
  2010年   4102篇
  2009年   3029篇
  2008年   5011篇
  2007年   4799篇
  2006年   4790篇
  2005年   3970篇
  2004年   3979篇
  2003年   3574篇
  2002年   3293篇
  2001年   2675篇
  2000年   2559篇
  1999年   1961篇
  1998年   836篇
  1997年   595篇
  1996年   638篇
  1995年   592篇
  1992年   1231篇
  1991年   1128篇
  1990年   1060篇
  1989年   1127篇
  1988年   964篇
  1987年   973篇
  1986年   888篇
  1985年   949篇
  1984年   779篇
  1983年   684篇
  1979年   849篇
  1978年   598篇
  1977年   587篇
  1975年   694篇
  1974年   756篇
  1973年   720篇
  1972年   667篇
  1971年   603篇
  1970年   655篇
  1969年   723篇
  1968年   677篇
  1967年   569篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
61.
1. Male quails submitted 20 and 120 days to a low iron diet (7 ppm) were compared to female laying quails, exposed for 30 days to the same low iron regime, in order to compare the response of the iron metabolic control under a single (erythropoiesis) or a doubled (erythropoiesis and egg formation) iron demand. 2. Iron deposit in storage organs, the classical hematology and the intestinal iron absorption were analyzed in these animals. 3. In males, after 120 days, the iron deposits were reduced 50 and 75%, but hematological values (hematocrit and hemoglobin concentration) were normal, although in laying quails, after 30 days, an anemic condition was evident in both blood parameters and iron deposits, provoking an iron deficient erythropoiesis. 4. The enhancement of the intestinal iron uptake, confirms the anemic character of these birds.  相似文献   
62.
Four thalamic and cortical recordings were carried out in 5 patients. The thalamic-evoked potentials were typical and revealed a triphasic complex, but their latencies showed a relatively high standard deviation. They could be divided into two groups according to their latencies, both of which had low SD. These data suggested that there could be two types of latency of thalamic SEP, because the 4 patients' body sizes were very similar. More detailed surface, cortical and depth recordings are needed to resolve these questions.  相似文献   
63.
64.
The relationship between overnight postabsorptive (fasting) respiratory exchange ratio (RER) and plasma FFA concentrations was addressed using data from three separate protocols, each of which involved careful control of the antecedent diet. Protocol 1 examined the relationship between fasting RER and the previous daytime RER. In Protocol 2 fasting, RER and plasma palmitate concentrations were measured in 29 women and 31 men (body mass index <30 kg·m−2). Protocol 3 analyzed data from Nielsen et al. (Nielsen, S., Z. K. Guo, J. B. Albu, S. Klein, P. C. O''Brien, M. D. Jensen. 2003. Energy expenditure, sex and endogenous fuel availability in humans. J. Clin. Invest. 111: 981-988.) to understand how fasting RER and palmitate concentrations relate within individuals during four consecutive measurements. The results were as follows: 1) Fasting RER was correlated (r = 0.74, P < 0.001) with the previous day''s average RER, and less so with RER variability. 2) Fasting RER was correlated (r = −0.39, P = 0.007) with fasting plasma palmitate concentrations. 3) The pattern of the RER/palmitate relationship was similar within individuals and between individuals; a negative slope was observed significantly more often than a positive slope (χ2 test; P < 0.001). Our findings suggest that, despite a fixed food quotient, the slight departures from energy equilibrium in a controlled General Clinical Research Center environment can effect plasma FFA concentrations. We suggest that including indirect calorimetry as part of FFA metabolism studies may aid in data interpretation.  相似文献   
65.
66.
67.
Effect of precursors on biosynthesis of monensins A and B   总被引:1,自引:0,他引:1  
Precursors of monensins (acetate, propionate, butyrate, isobutyrate) affect the total production and the relative proportion of monensins A and B. Addition of propionate into the fermentation medium causes a prevalence of monensin B whereas butyrate and isobutyrate stimulate the production of monensin A and suppress the production of monensin B.  相似文献   
68.
Analogs of deamino-oxytocin and deamino-oxypressin containing a CH2-NH group instead of an amide bond between positions 8 and 9 were synthesized. All tested compounds exhibit significantly lowered biological activities.  相似文献   
69.
70.
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