全文获取类型
收费全文 | 974篇 |
免费 | 93篇 |
国内免费 | 1篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 15篇 |
2017年 | 17篇 |
2016年 | 32篇 |
2015年 | 44篇 |
2014年 | 56篇 |
2013年 | 56篇 |
2012年 | 74篇 |
2011年 | 75篇 |
2010年 | 51篇 |
2009年 | 52篇 |
2008年 | 58篇 |
2007年 | 57篇 |
2006年 | 45篇 |
2005年 | 58篇 |
2004年 | 60篇 |
2003年 | 51篇 |
2002年 | 67篇 |
2001年 | 16篇 |
2000年 | 18篇 |
1999年 | 4篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有1068条查询结果,搜索用时 15 毫秒
1.
Aino Juslén Juha Pykälä Saija Kuusela Lauri Kaila Jaakko Kullberg Jaakko Mattila Jyrki Muona Sanna Saari Pedro Cardoso 《Biodiversity and Conservation》2016,25(3):569-585
For the first time ever, the International Union for Conservation of Nature Red List Index for habitat types was calculated for an entire country, Finland. The RLIs were based on species threat assessments from 2000 and 2010 and included habitat definitions for all 10,131 species of 12 organism groups. The RLIs were bootstrapped to track statistically significant changes. The RLI changes of species grouped by habitats were negative for all habitat types except for forests and rural biotopes which showed a stable trend. Trends of beetles and true bugs were positive in rural and forest habitats. Other 16 observed trends of species group and habitat combinations were negative. Several trends observed were in accordance with studies focusing on particular taxa and habitats, and drivers for their change. This study demonstrates the usefulness of the RLI as a tool for observing habitat change based on species threat assessment data. 相似文献
2.
A Jukkola J Risteli L Risteli 《Biochemical and biophysical research communications》1990,170(1):264-269
Sodium chlorate, a potent inhibitor of sulfation reactions, completely inhibits the formation of tyrosine-o-sulfate in type III procollagen in human fibroblasts, when used in concentrations that do not affect the incorporation of radioactive amino acids into protein. The unsulfated type III procollagen is secreted into the medium at a rate comparable, to those of sulfated type III procollagen and type I procollagen, which normally does not undergo sulfation. The enzymatic cleavage of the aminoterminal propeptide of type III procollagen is incomplete in fibroblast cultures, irrespective of the sulfation status of the protein. 相似文献
3.
The vegetation of semi-natural grasslands under modern, cereal/forage cropping in Finnish Karelia (n = 11) and old fashioned animal husbandry in adjacent Russian Karelia (n = 11) was compared in terms of their species composition. Each grassland site was paired with one in the other country which was as similar as possible in respect to its natural conditions. The species composition indicated differences in management between the two countries. The mean number of species was 4S.S in the Finnish sites and 52.6 in the Russian sites. A total of 12 species exhibited a statistical difference in their indicator values between the two countries. Traditional grassland species (e.g. Leontodon hispidus, Dianthus deltoides ), indicating grazing, hay making and old settlement, occurred more oñen in Russian sites, while species related to nutrient enrichment and cultivation (e.g. Urtica dioica, Elymus repens ) were more characteristic of Finnish sites. 相似文献
4.
5.
Johanna Schleutker Leena Haataja Martin Renlund Lea Puhakka Juha Viitala Leena Peltonen Pertti Aula 《Human genetics》1991,88(1):95-97
Summary Salla disease is an inherited lysosomal storage disorder caused by accumulation of free sialic acid in the lysosomes. Lamp genes, lamp A and lamp B (lysosome associated membrane proteins), are the first known genes encoding for human lysosomal membrane proteins. Absence of linkage in a large group of families shows that lamp genes are not involved in Salla disease. The lamp genes were localized, using Southern hybridization in hamster — human hybrid cell panels, to chromosomes 13 (lamp A) and X (lamp B). 相似文献
6.
Max Häggblom Juha Apajalahti Mirja Salkinoja-Salonen 《Applied microbiology and biotechnology》1986,24(5):397-404
Summary A polychlorophenol degrader, Rhodococcus chlorophenolicus, was shown to metabolize five different chlorinated guaiacols, namely tetrachloroguaiacol, 3,4,6-trichloroguaiacol, 3,5,6-trichloroguaiacol, 3,5-dichloroguaiacol and 3,6-dichloroguaiacol. Seven different intermediate metabolites, each with three hydroxyl or methoxyl groups, were identified. Four of these metabolites were also dehalogenation products, three carrying one chlorine atom less than the parent compound, and one metabolite from tetrachloroguaiacol where two chlorine atoms had been removed. Tetrachloroguaiacol was shown to undergo reductive dehalogenation. Demethylation of guaiacol to catechol was observed with the dichloroguaiacols, but not with polychloroguaiacols.Abbreviations DCG
dichloroguaiacol
- TCG
trichloroguaiacol
- TeCG
tetrachloroguaiacol
- DCC
dichlorocatechol
- TCC
trichlorocatechol
- TeCC
tetrachlorocatechol
- TCP
trichlorophenol
- TeCP
tetrachlorophenol
- PCP
pentachlorophenol. An example of numeration
- 346-TCG
3,4,6-trichloroguaiacol
- GLC
gas liquid chromatography 相似文献
7.
Juha H. A. Apajalahti Mirja S. Salkinoja-Salonen 《Applied microbiology and biotechnology》1986,25(1):62-67
Summary An actinomycete, Rhodococcus chlorophenolicus, isolated from a pentachlorophenol-degrading mixed bacterial culture is a polychlorophenol degrader. It was shown to oxidize pentachlorophenol into carbon dioxide and to metabolize also 2,3,4,5-,2,3,4,6-, and 2,3,5,6-tetrachlorophenol, 2,3,4-, 2,3,5-, 2,3,6-, 2,4,6-, and 2,4,5-trichlorophenol, 2,5-, and 2,6-dichlorophenol and tetrachloro-p-hydroquinone in an inducible manner. Pentachlorophenol set on the synthesis of enzymes required for the metabolism of all these chlorophenols and of tetrachloro-p-hydroquinone. 2,4,5-, and 2,4,6-trichlorophenol and 2,5-, and 2,6-dichlorophenol were degraded by R. chlorophenolicus cells only if these had previous contact to pentachlorophenol. Other chlorophenols mentioned were able to set on the synthesis of enzymes for their own degradation. 2,3,4,5-, and 2,3,4,6-tetrachlorophenol, and 2,3,5-, 2,4,5-, and 3,4,5-trichlorophenol were more toxic to R. chlorophenolicus than the other chlorophenols, but nevertheless 2,3,4,5-, and 2,3,4,6-tetrachlorophenol and 2,3,5-trichlorophenol were readily degraded by the bacteria.Abbreviations DCP
dichlorophenol
- TCP
trichlorophenol
- TeCP
tetrachlorophenol
- PCP
pentachlorophenol
- TeCH
tetrachloro-p-hydroquinone
An example of numeration: 2345-TeCP, 2,3,4,5-tetrachlorophenol 相似文献
8.
Structural diversity and domain composition of a unique collagenous fragment (intima collagen) obtained from human placenta. 总被引:23,自引:3,他引:20 下载免费PDF全文
Intima collagen was obtained from pepsin digests of human placenta in two forms, which differ to some extent in the size of their constituent polypeptide chains (Mr 50 000-70 000). These chains are connected by disulphide bonds to large aggregates. The aggregates are arranged in a triple-helical conformation with a remarkably high thermal stability (Tm 41-62 degrees C) and are resistant to further proteolytic digestion. Reduction of as little as 5% of the disulphide bonds produces mainly monomeric triple helices (Mr about 160 000) with Tm 32 degrees C. Partially reduced material can be separated into triple-helical and non-collagenous domains by proteolysis. Pepsin releases a collagenous component with chains of Mr 38 000. Bacterial collagenase liberates two non-collagenous segments (Mr 15 000-30 000) rich in cystine. Treatment with collagenase before reduction separates intima collagen into a large fragment composed of collagenous (Tm 41 degrees C) and non-collagenous structures and a single non-collagenous segment. The data support the electron-microscopical model of intima collagen [Furthmayr, Wiedemann, Timpl, Odermatt & Engel (1983) Biochem. J. 211, 303-311], indicating that the basic unit of the fragment consists of a continuous triple helix joining two globular domains. 相似文献
9.
The interactions between phytoplankton and zooplankton were studied in two large lakes in the Saimaa lake system, Finland. Both are subjected to substantial waste water loading, and exhibit a clear trophic gradient between the loaded and unloaded areas. The phytoplankton and zooplankton were compared in terms of composition, abundance and biomass at 34–39 stations located in different parts of the lakes. At least four mechanisms were thought to affect the composition of plankton communities: (1) the amount of nutrients (trophic gradient), (2) grazing of algae by herbivores, (3) the effect of the algal species composition on feeding by zooplankters (large, colonial algae in the more loaded parts of the lakes) and (4) the regeneration and reorganization of nutrients. 相似文献
10.
Eutrophication and recovery of Lake Vesijärvi (south Finland): Diatom frustules in varved sediments over a 30-year period 总被引:2,自引:2,他引:0
Lake Vesijärvi was loaded by sewage from the City of Lahti for 60 years until 1976 when the discharge was diverted. Paleolimnological analyses of the varved bottom sediment indicate that the sedimentation rate within the Enonselka basin, the most eutrophic part of the lake, has been as high as 2 cm yr–1, and total phosphorus accumulation was 20–40 g P m–2 yr–1, during the last 20 years. Within the less eutrophic Laitialanselkä basin, the sedimentation rate did not exceed 1 cm yr–1, and the formation of varved sediment only began at the end of the 1960's, i.e. about 10 years later than in Enonselkä.Planktonic diatom production was highest in the Enonselka basin. The most abundant diatoms in the sediment between 1970–1985 were Asterionella formosa, Aulacoseira islandica and Stephanodiscus spp. Fragilaria crotonensis and Tabellaria fenestrata had low abundances in the middle of the 1970's but increased again at the end of the 1970's. Asterionella formosa and Diatoma elongatum reached their maxima between 1979–1984 when the hypolimnion of the Enonselk/:a basin was aerated artificially. In the Laitialanselkä basin, the production of planktonic diatoms has been lower and the species composition of the diatom community differed from that in Enonselkä. However, at the end of 1980's the total accumulation of diatoms in Laitialanselkä approached levels which were observed at the end of 1950's in Enonselkä, prior to the rapid eutrophication period.The production and thereby the sedimentation of diatoms has decreased towards the end of the 1980's in Enonselkä, indicating reduced nutrient availability in the lake water. This reduction was due to the decreased external loading of phosphorus as well as to the decreased release of phosphorus from the sediment as a result of improved oxygen balance in the hypolimnion. 相似文献