全文获取类型
收费全文 | 11733篇 |
免费 | 881篇 |
国内免费 | 3篇 |
出版年
2023年 | 89篇 |
2022年 | 171篇 |
2021年 | 366篇 |
2020年 | 295篇 |
2019年 | 301篇 |
2018年 | 433篇 |
2017年 | 350篇 |
2016年 | 538篇 |
2015年 | 655篇 |
2014年 | 698篇 |
2013年 | 835篇 |
2012年 | 1023篇 |
2011年 | 927篇 |
2010年 | 570篇 |
2009年 | 499篇 |
2008年 | 631篇 |
2007年 | 624篇 |
2006年 | 561篇 |
2005年 | 419篇 |
2004年 | 396篇 |
2003年 | 389篇 |
2002年 | 336篇 |
2001年 | 190篇 |
2000年 | 174篇 |
1999年 | 147篇 |
1998年 | 97篇 |
1997年 | 79篇 |
1996年 | 73篇 |
1995年 | 58篇 |
1994年 | 58篇 |
1993年 | 56篇 |
1992年 | 67篇 |
1991年 | 56篇 |
1990年 | 37篇 |
1989年 | 57篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 34篇 |
1984年 | 37篇 |
1983年 | 36篇 |
1982年 | 25篇 |
1981年 | 14篇 |
1980年 | 15篇 |
1979年 | 11篇 |
1978年 | 14篇 |
1977年 | 9篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1971年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Arhur G. Steinberg Celia P. Milstein Carla L. McLaughlin Alan Solomon 《Immunogenetics》1974,1(1):108-117
A Bence Jones protein with phenotype Inv (1, –2) was isolated from the urine of a patient with multiple myeloma. Inv typing of the patient's relatives established the presence of anInv
1 allele in the kindred, and that the patient's genotype wasInv
1/Inv
3. Hence, the absence of Inv (2) in the Bence Jones protein was shown to be genetic and not an artifact caused by the disease. The tryptic peptide-containing residues 191 through 194 were isolated and shown to be composed of Leu, Tyr, Ala, Cys, with Leu at the amino end. Hence, the residue at 191 is the same as that present in Inv (1, 2) Bence Jones proteins. More detailed study of the tryptic peptides established that residue 153 is Val rather than Ala as in all other K chains thus far studied. The primary sequence: Ala153, Leu191 determines Inv (1, 2); Ala153, Val191 determines Inv (3); and Val153, Leu191 determines Inv (1). The Val153, Val191 sequence has not been observed. It may correspond to Inv (–). These data are strikingly similar to the data for the Kern and Oz isotypes (changes at 154 and 191, respectively) in the chain. As in the case of theK chain, only three of the four possible combinations have been observed. The implications of this parallelism and of crystallographic findings on chains, reported by others, are discussed. 相似文献
53.
54.
The better his understanding of some of the ways in which an organic deficit might affect normal development of the handicapped child, the more able the family physician will be to offer guidance to the family aimed at preventing the development of secondary problems. He can thus be instrumental in helping a child achieve his maximal potential.First, it is important to take into account how the parents'' emotional and intellectual responses to having a defective child may interfere markedly in normal parent-child relationship. Second, ways in which each deficit will limit a child''s exposure to stimuli must not be over-looked. Third, one must consider how a deficit may indirectly distort the normal learning patterns when parents do not make age appropriate demands. Fourth, it is important to understand how specific interference in the area of language skills may cause further developmental retardation. Fifth, one must be aware of special problems that an organically handicapped child must face in the society outside of the family. Last of all, in an older child, one must consider the need for a full scale evaluation to sort out primary and secondary factors in the picture. 相似文献
55.
56.
57.
Changes in polyamine content during in vivo maturation and in vitro culture of maize (Zea mays L.) pollen were studied. The endogenous content of free, conjugated and bound polyamines was analyzed during 30 days of pollen evolution, in both developmental pathways (microsporogenesis and androgenesis). The induction of androgenesis from cold-pretreated uninucleate pollen results, in most of cases, in a lower total polyamine content than that of the in vivo uninucleate pollen. These differences indicate that polyamine metabolism is altered during the induction of androgenesis, and this could be a consequence of increased polyamine assimilation. In general, pollen stages that involve cell division (tetrades, pre-anthesis pollen and four-day cultured pollen) are characterized by a predominance of free Spd. The increase of Spd and Spm in 15-day cultured pollen, when the first embryoids are formed, outline the possible implication of these polyamines in embryogenetic processes. Furthermore, these findings may contribute to the improvement of maize androgenesis yield, especially in recalcitrant genotypes, by the exogenous application of polyamines or polyamine-inhibitors to the culture medium.Abbreviations PAs
polyamines
- Put
putrescine
- Spd
spermidine
- Spm
spermine
- S
free polyamine fraction
- SH
conjugated polyamine fraction
- PH
bound polyamine fraction 相似文献
58.
59.
60.