全文获取类型
收费全文 | 1000751篇 |
免费 | 106215篇 |
国内免费 | 816篇 |
专业分类
1107782篇 |
出版年
2018年 | 9617篇 |
2017年 | 9106篇 |
2016年 | 12820篇 |
2015年 | 16570篇 |
2014年 | 19736篇 |
2013年 | 28107篇 |
2012年 | 31528篇 |
2011年 | 32354篇 |
2010年 | 21965篇 |
2009年 | 20469篇 |
2008年 | 28831篇 |
2007年 | 29895篇 |
2006年 | 28107篇 |
2005年 | 26969篇 |
2004年 | 26678篇 |
2003年 | 25703篇 |
2002年 | 25177篇 |
2001年 | 45351篇 |
2000年 | 45282篇 |
1999年 | 35951篇 |
1998年 | 12812篇 |
1997年 | 13096篇 |
1996年 | 12382篇 |
1995年 | 11417篇 |
1994年 | 11042篇 |
1993年 | 11158篇 |
1992年 | 29286篇 |
1991年 | 28804篇 |
1990年 | 28015篇 |
1989年 | 27387篇 |
1988年 | 25230篇 |
1987年 | 23994篇 |
1986年 | 22307篇 |
1985年 | 22130篇 |
1984年 | 18020篇 |
1983年 | 15788篇 |
1982年 | 11852篇 |
1981年 | 10673篇 |
1980年 | 9977篇 |
1979年 | 16818篇 |
1978年 | 13243篇 |
1977年 | 11989篇 |
1976年 | 11257篇 |
1975年 | 12609篇 |
1974年 | 13435篇 |
1973年 | 13266篇 |
1972年 | 12023篇 |
1971年 | 10866篇 |
1970年 | 9577篇 |
1969年 | 9325篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
7.
A. A. Kepel' 《Russian Journal of Marine Biology》2000,26(6):450-452
The alga Analipus japonicus (Harv.) Wynne displays a distinct seasonal pattern in its development in Peter the Great Bay (Sea of Japan). In winter and spring, it occurs only in the form of basal crusts, and vertical axes develop in the summer–autumn period. It reproduces mostly asexually from July to November. Algae with unilocular sporangia occur very seldom, only in June and July. 相似文献
8.
9.
Comparison of bone marrow extracellular matrices. 总被引:1,自引:0,他引:1
M Lee I P Christopherson J M Lehman C J Bennett H T Cheung 《Biochimica et biophysica acta》1999,1428(2-3):300-304
We have compared the structure and composition of adult and fetal bovine bone marrow extracellular matrices. In contrast to fetal bone marrow, adult bone marrow has more oval fenestration and accumulation of adipocytes as well as lower protein content. These differences could be due to remodeling of bone marrow tissue as it develops. Zymogram analysis of matrix metalloproteinase (MMP) and tissue inhibitor of MMP (TIMP) activities showed that fetal, but not adult bone marrow extract contained a 96-kDa MMP and TIMP-1 and -2. These activities may contribute to the structural differences between adult and fetal bone marrow tissues. 相似文献
10.
Random Amplified Polymorphic DNA Variation among and within Selected Ixora (Rubiaceae) Populations and Mutants 总被引:1,自引:0,他引:1
RAJASEGER G.; TAN H. T. W.; TURNER I. M.; SAW L. G.; KUMAR P. P. 《Annals of botany》1999,84(2):253-257
Random amplified polymorphic DNA (RAPD) analysis was used tostudy variation among and within selectedIxora (Rubiaceae) populationsand mutants. Six populations of I. congesta yielded identicalbanding patterns suggesting genetic uniformity of this species.However, six populations of I. coccinea varieties (three red-flowered,two yellow-flowered and one red-flowered wild-type) exhibitedinfraspecific differences in RAPD profiles. Small and largeleaves of an atavistic mutant cultivar of I. coccinea were alsosubjected to RAPD analysis. An extra band was amplified in thelarge leaves that was absent in small leaves, suggesting thatthe phenotypic alteration in this taxon is due to genetic mutationrather than epigenetic changes. Similarly, an extra band wasdetected in the white sectors of I. Variegated compared to thegreen sectors, suggesting that the shoot apical meristems ofthis cultivar exist as a genetic chimera. DNA gel blot hybridizationwas performed to confirm the specificities of selected bands.Our study indicates that differences among individuals of variouspopulations and mutants may be detected using RAPD markers.Copyright 1999 Annals of Botany Company Ixora L., variegated variety, RAPD fingerprinting, DNA gel blot, intraspecific genetic similarity, atavistic mutant. 相似文献