全文获取类型
收费全文 | 29939篇 |
免费 | 1371篇 |
国内免费 | 6篇 |
专业分类
31316篇 |
出版年
2023年 | 179篇 |
2022年 | 293篇 |
2021年 | 556篇 |
2020年 | 433篇 |
2019年 | 526篇 |
2018年 | 860篇 |
2017年 | 749篇 |
2016年 | 1009篇 |
2015年 | 1176篇 |
2014年 | 1366篇 |
2013年 | 1803篇 |
2012年 | 1717篇 |
2011年 | 1816篇 |
2010年 | 1151篇 |
2009年 | 914篇 |
2008年 | 1274篇 |
2007年 | 1342篇 |
2006年 | 1307篇 |
2005年 | 1090篇 |
2004年 | 943篇 |
2003年 | 929篇 |
2002年 | 803篇 |
2001年 | 638篇 |
2000年 | 549篇 |
1999年 | 427篇 |
1998年 | 223篇 |
1992年 | 334篇 |
1991年 | 323篇 |
1990年 | 257篇 |
1989年 | 281篇 |
1988年 | 297篇 |
1987年 | 297篇 |
1986年 | 274篇 |
1985年 | 303篇 |
1984年 | 250篇 |
1983年 | 206篇 |
1979年 | 277篇 |
1978年 | 190篇 |
1977年 | 158篇 |
1976年 | 157篇 |
1975年 | 199篇 |
1974年 | 287篇 |
1973年 | 278篇 |
1972年 | 267篇 |
1971年 | 261篇 |
1970年 | 267篇 |
1969年 | 260篇 |
1968年 | 208篇 |
1967年 | 207篇 |
1966年 | 186篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
W Y Mok R C Luiz?o M do S Barreto da Silva 《Applied and environmental microbiology》1982,44(3):570-575
A total of 2,886 bats captured in the Amazon Basin of Brazil were processed for the isolation of fungi. From the livers, spleens, and lungs of 155 bats (5.4%), 186 fungal isolates of the genera Candida (123 isolates), Trichosporon (26 isolates), Torulopsis (25 isolates), Kluyveromyces (11 isolates), and Geotrichum (1 isolate) were recovered. Seven known pathogenic species were present: Candida parapsilosis, C. guilliermondii, C. albicans, C. stellatoidea, C. pseudotropicalis, Trichosporon beigelii, and Torulopsis glabrata. Twenty-three culture-positive bats showed identical fungal colonization in multiple organs or mixed colonization in a single organ. The fungal isolation rates for individual bat species varied from 1 fungus per 87 bats to 3 fungi per 13 bats, and the mycoflora diversity for members of an individual fungus-bearing bat species varied from 16 fungi per 40 bats to 7 fungi per 6 bats. Of the 38 fungal species isolated, 36 had not been previously described as in vivo bat isolates. Of the 27 culture-positive bat species, 21 had not been previously described as mammalian hosts for medically or nonmedically important fungi. 相似文献
5.
6.
I P Grigor'ev A A Neokesari?ski? 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(9):288-289
The effects of different concentrations of L-ascorbic acid (Asc) on Na+-dependent binding of 3H-GABA and 3H-DL-glutamic acid to rat brain cortical synaptosomes were studied. Asc, at a concentration nearly equal to brain extracellular one (3 X 10(-4) M), had no effect on specific and nonspecific 5H-GABA binding. At higher concentrations (10(-3) M) Asc strongly inhibited, and at lower concentrations (10(-6) M) considerably stimulated 3H-GABA binding. At a concentration of 10(-5)-10(-3) M Asc tended to decrease 3H-DL-glutamic acid binding. 相似文献
7.
Ruzyłło E 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1953,7(49):1655-1660
8.
Maria João Feio Trefor B. Reynoldson Verónica Ferreira Manuel Augusto S. Graça 《Hydrobiologia》2007,579(1):55-68
We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive
model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to
September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model.
At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream
hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207
taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution
to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise
forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality,
substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to
reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream
sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model,
the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model
methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and
increasing the number of ellipses that define quality bands.
Handling editor: K. Martens 相似文献
9.
10.