全文获取类型
收费全文 | 9466篇 |
免费 | 827篇 |
国内免费 | 12篇 |
出版年
2023年 | 33篇 |
2022年 | 105篇 |
2021年 | 200篇 |
2020年 | 104篇 |
2019年 | 145篇 |
2018年 | 191篇 |
2017年 | 185篇 |
2016年 | 271篇 |
2015年 | 463篇 |
2014年 | 508篇 |
2013年 | 649篇 |
2012年 | 800篇 |
2011年 | 769篇 |
2010年 | 509篇 |
2009年 | 425篇 |
2008年 | 653篇 |
2007年 | 600篇 |
2006年 | 560篇 |
2005年 | 541篇 |
2004年 | 491篇 |
2003年 | 441篇 |
2002年 | 434篇 |
2001年 | 97篇 |
2000年 | 68篇 |
1999年 | 92篇 |
1998年 | 113篇 |
1997年 | 74篇 |
1996年 | 62篇 |
1995年 | 39篇 |
1994年 | 53篇 |
1993年 | 45篇 |
1992年 | 30篇 |
1991年 | 36篇 |
1990年 | 43篇 |
1989年 | 28篇 |
1988年 | 34篇 |
1987年 | 33篇 |
1986年 | 29篇 |
1985年 | 20篇 |
1984年 | 34篇 |
1983年 | 18篇 |
1982年 | 34篇 |
1981年 | 27篇 |
1980年 | 27篇 |
1979年 | 33篇 |
1978年 | 18篇 |
1977年 | 16篇 |
1974年 | 23篇 |
1972年 | 23篇 |
1971年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 785 毫秒
11.
12.
13.
14.
15.
16.
17.
Yongru Sun Berthold M. Heil Günter Kahl Hans Willy Kohlenbach 《Plant Cell, Tissue and Organ Culture》1987,8(1):91-100
Calli were initiated from flower buds, gynoecia and inflorescence segments of Haworthia magnifica v. Poelln. and subcultured on solid medium. Two liquid culture steps were necessary to prepare the calli for the isolation of protoplasts capable of sustained cell divisions. Plants were regenerated from protoplast-derived calli. The influence of both the osmolality of the culture media and exudates on the viability of protoplasts and protoplast-derived cell colonies is briefly discussed. 相似文献
18.
An ultrastructural analysis of the gametogenetic phases in Branchiura sowerbyi, a tubificid oligochaete, has been accomplished. These phases mostly conform to the usual pattern for the family, however, some interesting peculiarities are pointed out. The regression of sexual apparatus after reproductive period and its regeneration up to a new period of sexual maturity, has been followed throughout the year. 相似文献
19.
Synopsis Young-of-the-year largemouth bass,Micropterus salmoides, were exposed to four concentrations of sulphuric acid (pH levels 7.2, 6.1, 4.8, and 3.7) for 30 days, and the frequencies of feeding acts and activity bouts, and time budgets were recorded. Juveniles at pH 6.1 and at pH 4.8 performed the two feeding acts, bites and orientations, more often, and spent more time feeding than bass at pH 7.2. Bass at pH 3.7, however, reduced feeding, and spent a significantly larger portion of their time hovering in the water column. Frequencies of comfort and agonistic acts increased with a decline in pH. Alterations of behavioural repertoires of young-of-the-year largemouth bass were useful indicators of sulphuric acid exposure. 相似文献
20.
The Putative Oncogene Pim-1 in the Mouse: Its Linkage and Variation among t Haplotypes 总被引:5,自引:3,他引:2
下载免费PDF全文
![点击此处可从《Genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pim-1, a putative oncogene involved in T-cell lymphomagenesis, was mapped between the pseudo-alpha globin gene Hba-4ps and the alpha-crystallin gene Crya-1 on mouse chromosome 17 and therefore within the t complex. Pim-1 restriction fragment variants were identified among t haplotypes. Analysis of restriction fragment sizes obtained with 12 endonucleases demonstrated that the Pim-1 genes in some t haplotypes were indistinguishable from the sizes for the Pim-1b allele in BALB/c inbred mice. There are now three genes, Pim-1, Crya-1 and H-2 I-E, that vary among independently derived t haplotypes and that have indistinguishable alleles in t haplotypes and inbred strains. These genes are closely linked within the distal inversion of the t complex. Because it is unlikely that these variants arose independently in t haplotypes and their wild-type homologues, we propose that an exchange of chromosomal segments, probably through double crossingover, was responsible for indistinguishable Pim-1 genes shared by certain t haplotypes and their wild-type homologues. There was, however, no apparent association between variant alleles of these three genes among t haplotypes as would be expected if a single exchange introduced these alleles into t haplotypes. If these variant alleles can be shown to be identical to the wild-type allele, then lack of association suggests that multiple exchanges have occurred during the evolution of the t complex. 相似文献