全文获取类型
收费全文 | 2729篇 |
免费 | 239篇 |
国内免费 | 1308篇 |
出版年
2024年 | 44篇 |
2023年 | 110篇 |
2022年 | 137篇 |
2021年 | 160篇 |
2020年 | 181篇 |
2019年 | 176篇 |
2018年 | 139篇 |
2017年 | 178篇 |
2016年 | 179篇 |
2015年 | 157篇 |
2014年 | 130篇 |
2013年 | 204篇 |
2012年 | 168篇 |
2011年 | 179篇 |
2010年 | 140篇 |
2009年 | 209篇 |
2008年 | 214篇 |
2007年 | 218篇 |
2006年 | 198篇 |
2005年 | 144篇 |
2004年 | 115篇 |
2003年 | 97篇 |
2002年 | 92篇 |
2001年 | 82篇 |
2000年 | 59篇 |
1999年 | 61篇 |
1998年 | 37篇 |
1997年 | 43篇 |
1996年 | 40篇 |
1995年 | 42篇 |
1994年 | 29篇 |
1993年 | 25篇 |
1992年 | 34篇 |
1991年 | 27篇 |
1990年 | 29篇 |
1989年 | 27篇 |
1988年 | 14篇 |
1987年 | 18篇 |
1986年 | 36篇 |
1985年 | 18篇 |
1984年 | 14篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1973年 | 2篇 |
排序方式: 共有4276条查询结果,搜索用时 15 毫秒
51.
V. S. Rao 《Hydrobiologia》1977,53(1):13-32
Data on the ecology of Diatoms, Euglenineae and Myxophyceae in three freshwater ponds, differing in chemical composition and algal flora, situated in the vicinity of Hyderabad-India are presented. An attempt has been made to isolate various genera into groups, as their multiplication depended on particular ranges of a single chemical factor or set of factors. Several species could be separated into seasonal forms as they occur in particular periods of the year. Others could be grouped under indifferent forms as these are neither influenced by fluctuations in chemical factors nor by seasonal changes. 相似文献
52.
Eftihia Cayanis A. B. Lane T. Jenkins G. T. Nurse Doris Balinsky 《Biochemical genetics》1977,15(7-8):765-773
A new variant of the red cell enzyme glucose-6-phosphate dehydrogenase has been detected in a South African male of Indian descent and in several of his relatives. The enzyme variant is characterized by slow electrophoretic mobility, low Michaelis constants for the substrates glucose-6-phosphate and NADP, and increased utilization of the substrate analogues 2-deoxyglucose-6-phosphate and deamino-NADP relative to the normal (B+) enzyme. There is no evidence that the enzyme variant, for which the name G6PD Porbandar is suggested, is associated with any hematological abnormality.The Atomic Energy Board and the South African Medical Research Council provided support for part of this work. 相似文献
53.
DAVID H. LORENCE 《Botanical journal of the Linnean Society. Linnean Society of London》1978,76(3):207-247
A survey of the pteridophytes of Mauritius is presented, including a summary of their habitats, ecology, and phytogeographical affinities. Of the 186 infrageneric taxa recorded from the island, 8 are adventive or naturalized, and 27 are presumed rare or extinct. Major ecological groupings are presented and species are listed for both indigenous and secondary plant communities. 相似文献
54.
A case of somatic instability affecting aleurone colour in a strain of maize from India with flint background was analysed.
The somatic instability is localized to theC
1 (Inhibitor) allele ofC locus on the short arm of chromosome 9. Molecular tests indicated thatAc is not present in the Indian stock and the evidence is consistent with the involvement of theEn (Spm) transposable element in the instability. The presence of theEn (Spm)-like element in the stock would suggest that these elements have been present in the maize genome for a long time. A new
allele ofshrunken (sh1) gene with a somewhat unorthodox breeding behaviour is also described. 相似文献
55.
56.
57.
58.
Within the great expanse of the Brazilian Amazon Basin,Sphagnum has been greatly overlooked, in part because of its scarcity and in part because of the paucity of trained bryological collectors in the area. During a Projeto Flora Amazônica expedition in 1979, seven specimens ofSphagnum were collected, representing six species, five of which are newly described:S. amazonicum, S. dimorphophyllum, andS. subsecundoides in sectionSphagnum;S. curicuriariense andS. ripense in sect.Subsecunda. Also discussed areS. negrense Mitt. andS. sanguinale Warnst. 相似文献
59.
Laurence J. Dorr 《Brittonia》1992,44(1):53-13
In 1843 S. B. Buckley (1809–1884) traveled up the St. Johns River, Florida in search of plants, shells, and possibly other
natural history objects. Buckley encountered many difficulties in interior Florida and his trip did not live up to his original
expectations. It was unfortunate that the took years to distribute his plant specimens, since few botanists or naturalists
had preceded him into that poorly explored region. 相似文献
60.