全文获取类型
收费全文 | 95篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
98篇 |
出版年
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 1篇 |
2012年 | 7篇 |
2011年 | 6篇 |
2010年 | 7篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1992年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 7篇 |
1959年 | 1篇 |
1949年 | 2篇 |
排序方式: 共有98条查询结果,搜索用时 8 毫秒
1.
B. M. HONIGBERG DIETER VOLKMANN ROLF ENTZEROTH ERICH SCHOLTYSECK 《The Journal of eukaryotic microbiology》1984,31(1):116-131
Two strains of Trichomonas vaginalis, JH162A, with low pathogenicity, and Balt 44, with high pathogenicity, as well as one highly pathogenic strain, KV-1, of Tritrichomonas foetus were studied by freeze-fracture electron microscopy. The protoplasmic faces (PFs) of the cell membranes of all three strains of both species had similar numbers of intramembranous particles (IMPs); however, the particles in the external faces (EFs) of these membranes were least abundant in Trichomonas vaginalis strain Balt 44 and most numerous in those of strain JH162A of this species. In Tritrichomonas foetus strain KV-1 the number of IMPs in the EF was close to but somewhat lower than that in the mild strain of the human urogenital trichomonad. In both species, the anterior, but not the recurrent, flagella had rosette-like formations, consisting of ~9 to 12 IMPs on both the PFs and EFs. The numbers and distribution of the rosettes appeared to vary among different flagella and in different areas of individual flagella of a single organism belonging to either species. The freeze-fracture electron micrographs provided a more complete understanding of the fine structure of undulating membranes of Trichomonadinae, as represented by Trichomonas vaginalis, and of Tritrichomonadinae (the Tritrichomonas augusta-type), as exemplified by Tritrichomonas foetus, than was gained from previous transmission and scanning electron microscope studies. Typically three longitudinal rows of IMPs on the PF of the recurrent flagellum of Trichomonas vaginalis were noted in the area of attachment of this flagellum to the undulating membrane. The functional aspects of the various structures and differences between certain organelles revealed in the two trichomonad species by the freeze-fracture method are discussed. 相似文献
2.
1. Studies of insect communities rarely support the parasitoid–host regulation hypothesis. Spatio‐temporal variation in parasitoid prevalence due to complex food web interactions or abiotic factors may prevent parasitoids from regulating hosts. 2. We examined the relative contribution of spatial (altitude) and temporal (years) sources to total variation in parasitoid prevalence rates in outbreaks of Epirrita autumnata Borkhausen and Operophtera brumata Linnaeus populations. We tested whether prevalence rates of generalist parasitoids were correlated between sympatric host populations and to what extent any of the parasitoids were host density dependent. 3. Four larval parasitoids (two specialists and two generalists) exhibited significantly structured spatio‐temporal dynamics over years and altitudes. The prevalence rates of one of the generalists were spatio‐temporally correlated between the two host species, while for the other they were not. 4. Three parasitoids showed tendencies for direct or delayed positive density dependence as expected from numerical and functional responses to their hosts. However, the effects were weak and minute compared to the variation attributed to year and altitude. 5. We conclude that unknown aspects of the larval parasitoid ecology that co‐vary with altitude and year in the study system dominate their prevalence dynamics and thus act to hinder density‐dependent responses that could potentially regulate host populations. 相似文献
3.
4.
JULES ANGST THOMAS D. MEYER ROLF ADOLFSSON PETER SKEPPAR MAURO CARTA FRANCO BENAZZI RU‐BAND LU YI‐HSUAN WU HAI‐CHEN YANG CHENG‐MEI YUAN PAOLO MORSELLI PETER BRIEGER JUDITH KATZMANN INES ALICE TEIXEIRA LEÃO JOSÉ ALBERTO DEL PORTO DORIS HUPFELD MORENO RICARDO A. MORENO ODEILTON T. SOARES EDUARD VIETA ALEX GAMMA 《World psychiatry》2010,9(1):41-49
This study examined the transcultural robustness of a screening instrument
for hypomania, the Hypomania Checklist-32, first revised version (HCL-32 R1).
It was carried out in 2606 patients from twelve countries in five geographic
regions (Northern, Southern and Eastern Europe, South America and East Asia).
In addition, GAMIAN Europe contributed data from its members. Exploratory
and confirmatory factor analyses were used to examine the transregional stability
of the measurement properties of the HCL-32 R1, including the influence of
sex and age as covariates. Across cultures, a two-factor structure was confirmed:
the first factor (F1) reflected the more positive aspects of hypomania (being
more active, elated, self-confident, and cogni-tively enhanced); the second
factor (F2) reflected the more negative aspects (being irritable, impulsive,
careless, more substance use). The measurement properties of the HCL-32 R1
were largely invariant across cultures. Only few items showed transcultural
differences in their relation to hypomania as measured by the test. F2 was
higher among men and in more severe manic syndromes; F1 was highest in North
and East Europe and lowest in South America. The scores decreased slightly
with age. The frequency of the 32 items showed remarkable similarities across
geographic areas, with two excep-tions: South Europeans had lower symptom
frequencies in general and East Europeans higher rates of substance use. These
findings support the interna-tional applicability of the HCL-32 R1 as a screening
instrument for hypomania. 相似文献
5.
6.
OLE PETTER LAKSFORSMO VINDSTAD SNORRE B. HAGEN TINO SCHOTT ROLF A. IMS 《Ecological Entomology》2010,35(4):456-463
1. Wide temporal fluctuations in host abundance are a potential source of instability and stochasticity in the spatiotemporal population dynamics of associated parasitoid species. Within parasitoid guilds (i.e. parasitoids with similar modes of host utilisation), a conceivable outcome is guild organisation according to a lottery model, in which guild members attain local dominance by colonising previously emptied habitats during increasing host density, before other guild members. In the spatial dimension, an expected manifestation of such dynamics is variable guild structure even across homogeneous habitats. 2. We examined the extent of large‐scale spatial patterning of guild characteristics in larval parasitoid wasps associated with cyclically outbreaking populations of the geometrid moth Operophtera brumata in northern Fennoscandia. The study was performed at the onset of the crash‐phase of the geometrid's outbreak cycle, along a 70‐km transect in costal northern Norway, characterised by largely homogeneous environmental conditions, except for a small climatic gradient. 3. There was a distinct large‐scale spatial turnover in dominance among the major parasitoid groups (i.e. guild structure) in O. brumata along the transect, whereas the total prevalence rate of the guild and its diversity showed no consistent variation. Guild structure was unrelated to host density. 4. Although group‐specific responses to a slight spatial climatic gradient cannot be rejected as a causal mechanism, we conclude that our results are consistent with the expectation from large‐scale stochastic extinction‐recolonisation dynamics among functionally equivalent parasitoids relying on a host with strongly cyclic population fluctuations. 相似文献
7.
MARC KÉRY JOHN H. SPILLMANN CAMILLE TRUONG† ROLF HOLDEREGGER‡ 《Journal of Ecology》2006,94(5):980-986
8.
Cultivation of Leishmania donovani and Leishmania braziliensis in Defined Media: Nutritional Requirements 总被引:7,自引:0,他引:7
SYNOPSIS Nutritional requirements of promastigotes of Leishmania donovani and Leishmania braziliensis were studied in modifications of a simple defined culture medium. "Continuous growth," considered as propagation through 10 successive passages, was supported by inorganic salts, 14 l -amino acids (arginine, cysteine, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan, tyrosine, valine), glucose, adenosine, and a mixture of 11 vitamins and related growth factors. Purified defatted bovine serum albumin proved beneficial. The nutritional needs of the above species of Leishmania differ from those of 2 other hemoflagellate species, Leishmania tarentolae and Crithidia fasciculata , for which glucose, proline and glutamine were found to be nonessential. It is suggested that lower hemoflagellates may be capable of synthesizing these substrates de novo. Leishmania donovani and L. braziliensis required higher levels of folic acid than L. tarentolae , probably due to the fact that folates are involved as cofactors in the biosyntheses of pyrimidines and serine. Although the mixtures reported here cannot be regarded as "minimal essential" media, they are considerably less complex than the ones employed so far for cultivating hemoflagellates, and are therefore well suited for studies related to nutrition and biosynthetic capabilities of Trypanosomatids. 相似文献
9.
Cyclic AMP and Calcium in Relaxation in Intestinal Smooth Muscle 总被引:3,自引:0,他引:3
WE have studied the role of cyclic AMP in relaxation of smooth muscle and elucidated the mechanism of its action. 相似文献
10.
JUAN PEDRO FERRIO MATTHIAS CUNTZ CHRISTINE OFFERMANN ROLF SIEGWOLF MATTHIAS SAURER & ARTHUR GESSLER 《Plant, cell & environment》2009,32(10):1285-1296
Current models of leaf water enrichment predict that the differences between isotopic enrichment of water at the site of evaporation (Δe ) and mean lamina leaf water enrichment (ΔL ) depend on transpiration rates ( E ), modulated by the scaled effective length ( L ) of water isotope movement in the leaf. However, variations in leaf parameters in response to changing environmental conditions might cause changes in the water path and thus L . We measured the diel course of ΔL for 18 O and 2 H in beech seedlings under well-watered and water-limited conditions. We applied evaporative enrichment models of increasing complexity to predict Δe and ΔL , and estimated L from model fits. Water-limited plants showed moderate drought stress, with lower stomatal conductance, E and stem water potential than the control. Despite having double E , the divergence between Δe and ΔL was lower in well-watered than in water-limited plants, and thus, L should have changed to counteract differences in E . Indeed, L was about threefold higher in water-limited plants, regardless of the models used. We conclude that L changes with plant water status far beyond the variations explained by water content and other measured variables, thus limiting the use of current evaporative models under changing environmental conditions. 相似文献