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   81875篇
  免费   4598篇
  国内免费   9篇
  2023年   459篇
  2021年   935篇
  2020年   846篇
  2019年   817篇
  2018年   2199篇
  2017年   1931篇
  2016年   2624篇
  2015年   3454篇
  2014年   3529篇
  2013年   4673篇
  2012年   5496篇
  2011年   4815篇
  2010年   3130篇
  2009年   2314篇
  2008年   3891篇
  2007年   3665篇
  2006年   3638篇
  2005年   3047篇
  2004年   3063篇
  2003年   2743篇
  2002年   2503篇
  2001年   2060篇
  2000年   1923篇
  1999年   1473篇
  1998年   639篇
  1996年   509篇
  1992年   911篇
  1991年   837篇
  1990年   820篇
  1989年   893篇
  1988年   738篇
  1987年   758篇
  1986年   693篇
  1985年   760篇
  1984年   637篇
  1983年   555篇
  1982年   470篇
  1979年   677篇
  1978年   501篇
  1977年   497篇
  1975年   596篇
  1974年   647篇
  1973年   607篇
  1972年   560篇
  1971年   496篇
  1970年   544篇
  1969年   618篇
  1968年   581篇
  1967年   485篇
  1966年   472篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
51.
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   
52.
53.
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   
54.
55.
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   
56.
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   
57.
58.
59.
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   
60.
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