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   83868篇
  免费   4785篇
  国内免费   9篇
  2023年   473篇
  2021年   1069篇
  2020年   941篇
  2019年   977篇
  2018年   2270篇
  2017年   1983篇
  2016年   2693篇
  2015年   3568篇
  2014年   3666篇
  2013年   4840篇
  2012年   5662篇
  2011年   4992篇
  2010年   3261篇
  2009年   2489篇
  2008年   3997篇
  2007年   3763篇
  2006年   3718篇
  2005年   3140篇
  2004年   3139篇
  2003年   2784篇
  2002年   2545篇
  2001年   2078篇
  2000年   1931篇
  1999年   1503篇
  1998年   683篇
  1997年   481篇
  1996年   540篇
  1995年   474篇
  1992年   935篇
  1991年   847篇
  1990年   829篇
  1989年   909篇
  1988年   744篇
  1987年   756篇
  1986年   690篇
  1985年   758篇
  1984年   627篇
  1983年   550篇
  1979年   673篇
  1978年   490篇
  1977年   491篇
  1975年   585篇
  1974年   626篇
  1973年   596篇
  1972年   548篇
  1971年   491篇
  1970年   536篇
  1969年   610篇
  1968年   574篇
  1967年   479篇
排序方式: 共有10000条查询结果,搜索用时 843 毫秒
51.
52.
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   
53.
54.
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   
55.
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   
56.
57.
58.
The in vitro determination of the effects of some pharmacological agents on the outer diameter and axial tension of human Fallopian tube ampullar segments showed that some drugs may act on the circular and longitudinal smooth muscle layers relatively separately. PGF2 alpha elicited an excitatory response in both muscle layers while norepinephrine and isoproterenol decreased the activity. Oxytocin and indomethacin had relatively limited effects on the spontaneous motility of the ampullar segments. The calcium antagonist verapamil inhibited the spontaneous periodic activity.  相似文献   
59.
60.
A strain of 1,507 typised donors enables 15.97 average donors to be selected for a thrombocyte transfusion in one of 75 patients selected at random with HLA antibodies being previously determined (1 to 66 donors per patient). HLA compatible donors were found for 72 patients (97.33 per cent). More than 5 HLA compatible donors could be found for 58 patients. The high number of compatible donors is based on the fact that among 1,507 donors there were 156 HLA homozygotes and 556 donors with 3 HLA-A or B-antigens respectively. Compatibility in the ABO-system was not taken into account.  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