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   82783篇
  免费   4781篇
  国内免费   9篇
  2021年   1028篇
  2020年   906篇
  2019年   962篇
  2018年   2228篇
  2017年   1947篇
  2016年   2650篇
  2015年   3492篇
  2014年   3611篇
  2013年   4754篇
  2012年   5554篇
  2011年   4900篇
  2010年   3200篇
  2009年   2429篇
  2008年   3923篇
  2007年   3700篇
  2006年   3671篇
  2005年   3067篇
  2004年   3086篇
  2003年   2744篇
  2002年   2519篇
  2001年   2068篇
  2000年   1948篇
  1999年   1501篇
  1998年   680篇
  1997年   503篇
  1996年   544篇
  1995年   478篇
  1992年   942篇
  1991年   843篇
  1990年   830篇
  1989年   900篇
  1988年   738篇
  1987年   769篇
  1986年   694篇
  1985年   754篇
  1984年   630篇
  1983年   552篇
  1979年   673篇
  1978年   490篇
  1977年   490篇
  1975年   588篇
  1974年   627篇
  1973年   596篇
  1972年   552篇
  1971年   499篇
  1970年   538篇
  1969年   615篇
  1968年   574篇
  1967年   482篇
  1966年   468篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
161.
Flávio Resende 《Planta》1936,25(4):665-666
Ohne ZusammenfassungMit 1 Textabbildung (3 Einzelbildern).  相似文献   
162.
163.
164.
1. The cardiac pacemaker cells of the frog Caudiverbera caudiverbera are centrally located in the sinus venosus. These cells are rounded, smaller than contractile fibres and have large nuclei. 2. Intracellular recording confirmed the existence of primary and transitional pacemaker cells. 3. Action potentials from primary cells were resistant to blockade by tetrodotoxin (TTX), but were abolished by verapamil suggesting that their bioelectric activity is dependent on a slow inward current. 4. Transitional cells appeared to have two different inward currents contributing to the upstroke: a fast TTX-sensitive and a slow verapamil-sensitive current.  相似文献   
165.
1. The feeding pattern influences the inhibitory effects of malonyl-CoA on carnitine palmitoyltransferase-I. 2. The sensitivity of liver carnitine palmitoyltransferase-I to malonyl-CoA is increased in rats meal-fed when compared to rats fed ad libitum. 3. Moreover, liver carnitine palmitoyltransferase-I of meal-fed rats remains more sensitive to inhibition by malonyl-CoA during a 24 hour fast than liver carnitine palmitoyltransferase-I of rats previously fed ad libitum.  相似文献   
166.
This study focuses on assessing the reproduction mode of an important model species for evolutionary and behavioural ecology by using digital image analysis: the European bitterling Rhodeus amarus (Bloch, 1782). Specifications of mode of reproduction were determined using oocyte size distribution, seasonal dynamics in mean oocyte diameter and total number of oocytes in ovary samples gained from April to July 2007. The rapid oocyte count was enabled by using lucia image analysis software, which also provided measurement and colour estimations of oocytes. Bitterling ovaries showed features typical for indeterminate spawners, i.e. a continuous distribution of oocyte size over the reproductive season and recruitment of new pre‐vitelogenic oocytes in the second half of the reproductive season. These results are consistent with the view that the European bitterling is a batch spawning fish with indeterminate fecundity.  相似文献   
167.
168.
Summary The child with iminoglycinuria is in our observation. Hyperprolinuria was seen at 5 months by screening program. The child was repeatedly examined in the hospital and was seen last time at 16 months. IQ was 67, in the urine were excessive amounts of glycine, proline a hydroxyproline. In the blood aminoacids were in normal levels. In the child was noticed the same increase of proline in the blood as in the control child of the same age following loading test with L-proline, indicating normal intestinal absoption. Both parents and father's sister's 2-year-old mentally retarded child exhibit excessive glycinuria. The father, his sister, father's father, and grandfather are partialy, congenitaly deaf.  相似文献   
169.
DNA complexes with polypeptides (Lys-Ala-Ala)1)] and (Lys-Ala-Ala)34 have been studied using the methods of thermal melting and circular dichroism. Derivative melting curves of (Lys-Ala-Ala)10 DNA differed substantially from those of (Lys-Ala-Ala)34 prepared either by salt gradient dialysis or by direct mixing. Melting curves of the former complex were unimodal or bimodal with Tm increasing continuously withn input lysin-to-DNA phosphate ratio (r); those of the latter complex consisted of three separate transitions with Tm values almost independent of r. Complete reversibility of binding in the (Lys-Ala-Ala)10-DNA system but a slow redistribution of (Lys-Ala-Ala)34 on DNA at low temperature were found in the redistribution experiments Much faster redistribution from denatured to native DNA occurs at the temperature of melting, contributing to the unusual trimodal melting pattern. Circular dichroism curves are very similar for both complexes and indicate little change of DNA conformation upon polypeptide binding.  相似文献   
170.
Ohne Zusammenfassung  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