全文获取类型
收费全文 | 2004篇 |
免费 | 173篇 |
国内免费 | 1篇 |
专业分类
2178篇 |
出版年
2023年 | 9篇 |
2022年 | 12篇 |
2021年 | 38篇 |
2020年 | 22篇 |
2019年 | 34篇 |
2018年 | 34篇 |
2017年 | 41篇 |
2016年 | 65篇 |
2015年 | 127篇 |
2014年 | 125篇 |
2013年 | 164篇 |
2012年 | 168篇 |
2011年 | 169篇 |
2010年 | 107篇 |
2009年 | 85篇 |
2008年 | 132篇 |
2007年 | 99篇 |
2006年 | 91篇 |
2005年 | 68篇 |
2004年 | 71篇 |
2003年 | 83篇 |
2002年 | 65篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 24篇 |
1998年 | 28篇 |
1997年 | 15篇 |
1996年 | 17篇 |
1995年 | 25篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 23篇 |
1991年 | 12篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 9篇 |
1974年 | 4篇 |
1972年 | 5篇 |
1971年 | 4篇 |
排序方式: 共有2178条查询结果,搜索用时 15 毫秒
11.
Lawrence D. Mayer Marcel B. Bally Michael J. Hope Pieter R. Cullis 《Chemistry and physics of lipids》1986,40(2-4):333-345
As a prerequisite for the use of liposomes for delivery of biologically active agents, techniques are required for the efficient and rapid entrapment of such agents in liposomes. Here we review the variety of procedures available for trapping hydrophilic and hydrophobic compounds. Considerations which are addressed include factors influencing the choice of a particular liposomal system and techniques for the passive entrapment of drugs in multilamellar vesicles and unilamellar vesicles. Attention is also paid to active trapping procedures relying on the presence of (negatively) charged lipid or transmembrane ion gradients. Such gradients are particularly useful for concentrating lipophilic cationic drugs inside liposomes, allowing trapping efficiencies approaching 100%. 相似文献
12.
Pieter Dullemeijer 《Acta biotheoretica》1985,34(2-4):111-123
An introduction to the 19th Lochmühle conference on Architecture in living structure, organized by P. Dullemeijer, W.F. Gutmann and G.A. Zweers, held from March 15–17, 1984 in the Aussenstelle des Forschungsinstituts Senckenberg der Senckenbergischen Naturforschenden Gesellschaft, Frankfurt am Main. 相似文献
13.
14.
15.
From the Silberberg Quarry, type locality of the Silberberg Formation (Martini &Ritzkowski 1968), some planktonic foraminifera are described:Globigerina officinalis Subbotina, Globigerina ouachitaensisHowe &Wallace,G. praebulloides leroyi Blow &Banner, G.praebulloides occlusa Blow &Banner which taxa are here suggested to form intergrading morphotypes within the range of variation of a population dominated byG. officinalis. In addition,G. cf.danvillensis Howe &Wallace is found. The planktonic fauna, together with some elements in the benthonic fauna, suggests a possible correlation with the Danville Landing Member of the Jackson Formation, Louisiana, traditionally ascribed to the Upper Eocene. There is some similarity with European Uppermost Eocene — Lower Oligocene faunas described by various authors. The Silberberg Formation was suggested to be a Neostratotype for the Latdorfian Stage of the Lower Oligocene byMartini &Ritzkowski (1968). It is suggested that the Silberberg Formation may well be coeval with the Upper Priabonian as proposed byCita 1969. 相似文献
16.
Biochemical Studies of Bacterial Sporulation and Germination XIV. Phospholipids in Bacillus megaterium 总被引:22,自引:12,他引:10 下载免费PDF全文
The principal phospholipids of Bacillus megaterium throughout the cycle of growth and sporulation were found to be phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, and a hitherto unidentified isomer of glycosaminyl-phosphatidylglycerol. Phosphatidylglycerol predominated during vegetative cell growth and then declined as spores developed, whereas diphosphatidylglycerol became more prominent during spore maturation. The latter phosphatide was relatively inaccessible in the vegetative cell and was more accessible in the spore, as judged by solvent extraction under various conditions. 相似文献
17.
Roelof-Jan Oostra Stephan Kemp Pieter A. Bolhuis Elisabeth M. Sleeker-Wagemakers 《Human genetics》1996,97(4):500-505
Leber’s hereditary optic neuropathy (LHON) is a maternally inherited disorder of the optic nerves. It has been proposed that
the specific mutations in the mitochondrial DNA (mtDNA) that are associated with LHON require and X-chromosomally encoded
permissive factor in order to become expressed. This would explain both the preponderance of male patients and the fact that
most carriers of specific mtDNA mutations remain unaffected. Although linkage studies have been negative so far, the existence
of such a factor has not been ruled out. We investigated the genealogical data of 24 large LHON pedigrees and concluded that
the presumed X-linked factor would be recessively inherited and that at least 57% of the affected females would be heterozygous.
Therefore, these females must be the victim of nonrandom X-chromosomal inactivation (skewed lyonization). However, analysis
of X-chromosomal methylation patterns in 16 LHON-affected females revealed substantial skewing in only 15%–20% of cases, which
is not significantly different from the patterns in 49 controls. Moreover, we found the frequency of LHON in daughters of
affected heterozygous females to be twice to three times as high as in daughters of unaffected heterozygous females, which
cannot be explained by an X-chromosomally inherited factor. We conclude that the results of our investigations do not support
the hypothesis that LHON is a digenic disease with an X-linked factor being the main cause of loss of vision in the presence
of relevant mtDNA mutations.
Received: 1 June 1995 / Revised: 20 September 1995 相似文献
18.
Kazutoyo Osoegawa Rie Susukida Saishi Okano Jun Kudoh Shinsei Minoshima Nobuyoshi Shimizu Pieter J. de Jong Juergen Groet Jane Ives Hans Lehrach Dean Nizetic Eiichi Soeda 《Genomics》1996,32(3):375
The major phenotypic features of Down syndrome have been correlated with partial trisomies of chromosome 21, allowing us to define the candidate gene region to a 4-Mb segment on the 21q22.2 band. We present here a high-resolution physical map with megabase-sized cosmid/PAC contigs. This ordered clone library has provided unique material for the integration of a variety of mappable objects, including exons, cDNAs, restriction sites, etc. Furthermore, our results have exemplified a strategy for the completion of the chromosome 21 map to sequencing. 相似文献
19.
Anthocyanin pigments responsible for purple and pink flower colours in the tribe Podalyrieae have been identified. The considerable variation in flower colour is not reflected in the chemical variation and the flower pigments are surprisingly conservative. Virgilia flowers always have the acetic acid esters of cyanidin-3-glucoside and peonidin-3-glucoside as major compounds, together with trace amounts of the coumaroyl ester of cyanidin-3-glucoside. Podalyria flowers invariably have the rather more stable coumaroyl ester of cyanidin. The data support a close affinity between the two genera but also show that flower colour is only partially homologous. 相似文献
20.
Suzanne A. Adjoa Claude Bouchard Pieter Coetzer Tim D. Noakes France T. Dionne 《Human genetics》1994,93(3):347-348
A DNA polymorphism of the nuclear-encoded subunit Va of the human cytochrome c oxidase (COX), a mitochondrial respiratory enzyme, is reported. No polymorphism was detected in genes for the subunits IV and Vb of the same enzyme. 相似文献