全文获取类型
收费全文 | 12133篇 |
免费 | 890篇 |
国内免费 | 4篇 |
出版年
2021年 | 91篇 |
2020年 | 64篇 |
2019年 | 101篇 |
2018年 | 112篇 |
2017年 | 143篇 |
2016年 | 193篇 |
2015年 | 249篇 |
2014年 | 353篇 |
2013年 | 690篇 |
2012年 | 589篇 |
2011年 | 587篇 |
2010年 | 399篇 |
2009年 | 383篇 |
2008年 | 577篇 |
2007年 | 592篇 |
2006年 | 532篇 |
2005年 | 530篇 |
2004年 | 557篇 |
2003年 | 561篇 |
2002年 | 527篇 |
2001年 | 460篇 |
2000年 | 469篇 |
1999年 | 379篇 |
1998年 | 147篇 |
1997年 | 140篇 |
1996年 | 115篇 |
1995年 | 128篇 |
1994年 | 123篇 |
1993年 | 107篇 |
1992年 | 274篇 |
1991年 | 243篇 |
1990年 | 234篇 |
1989年 | 231篇 |
1988年 | 229篇 |
1987年 | 192篇 |
1986年 | 201篇 |
1985年 | 169篇 |
1984年 | 120篇 |
1983年 | 135篇 |
1982年 | 112篇 |
1981年 | 75篇 |
1980年 | 76篇 |
1979年 | 121篇 |
1978年 | 72篇 |
1977年 | 73篇 |
1975年 | 55篇 |
1973年 | 59篇 |
1972年 | 53篇 |
1970年 | 50篇 |
1968年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Nucleosides having an enol ester structure in the sugar portion were synthesized and their reaction with several types of electrophiles were carried out. This furnished a new method for constructing C-C bond at the 3'-position. 相似文献
5.
6.
Protective Effect of External Ca2+ on Elongation and the Intracellular Concentration of K+ in Intact Mung Bean Roots under High NaCl Stress 总被引:2,自引:0,他引:2
Nakamura Yoshiyuki; Tanaka Karo; Ohta Eiji; Sakata Makoto 《Plant & cell physiology》1990,31(6):815-821
The effects of Ca2+ in the external medium on intact mung beanroots under high NaCl stress were investigated. With increasingexternal concentrations of NaCl, mung bean roots showed suppressionof elongation and a decrease in the intracellular concentrationof K+. Addition of Ca2+ to the external medium alleviated theinhibition of root elongation under the high NaCl stress andmaintained a high intracellular concentration of K+ in the elongatingregion of the roots. This counter effect of Ca2+ against theNaCl stress on roots was correlated with the ratio of [Ca2+]/[Na+]2in the external medium. A value above 5.0 ? 104 mM1resulted in almost complete recovery of root elongation undervarious high concentrations of NaCl. Root elongation for 24h under NaCl stress was correlated with the extent to whichthe intracellular concentration of K+ was in excess of 10 mM.Maintenance of an adequate concentration of K+ in root cellsis essential for root elongation under salt stress. These findingsindicate that Ca2+ prevents the leakage of intracellular K+and thereby supports the elongation of roots under salt stress. (Received November 13, 1989; Accepted June 5, 1990) 相似文献
7.
8.
9.
Summary Regenerants derived from hairy roots of Ajuga reptans var. atropurpurea induced by infection with Agrobacterium rhizogenes MAFF03-01724 harboring pRi revealed a dwarfing response, i.e. decrease in leaf size, reduction in internode distance, and
increase in leaf number. These morphogenic alterations were accompanied by an increase in root mass and lack of floral differentiation.
In the pRi-transformed regenerants, the proportion of root mass to whole plant mass was higher than that of the untransformed
ones, although both kinds of regenerants were comparable on a fresh weight basis. High capacity of rooting and 20-hydroxyecdysone
production associated with the original hairy root line were stably maintained in clonal regenerants. 相似文献
10.
Hyperimmune and high-titered polyclonal pneumococcal antisera, specific for cross-reactive types within groups, were produced in adult rabbits. Purified capsular polysaccharide was injected intravenously into adult rabbits. One week later, these rabbits were given multiple intravenous injections of formalin-inactivated pneumococci of the cross-reactive type by an established method. Each of the resultant antisera were specific for the cross-reactive type indicating that the previous injection of the polysaccharide had induced epitope-specific tolerance. This method was successful for production of antisera against pneumococcal types 6A, 6B, 9N, 9V, 19F and 19A. Polyclonal rabbit pneumococcal antisera have some advantages over murine monoclonal antibodies for serologic studies and this method should be applicable for producing type-specific antibodies to cross-reactive polysaccharides of clinical interest. Further, this method is simpler and generally produces higher titered monovalent (factor) reagents than absorbed antisera. 相似文献