全文获取类型
收费全文 | 374篇 |
免费 | 31篇 |
专业分类
405篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 30篇 |
2014年 | 21篇 |
2013年 | 26篇 |
2012年 | 48篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 29篇 |
2007年 | 16篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 9篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 5篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 3篇 |
排序方式: 共有405条查询结果,搜索用时 0 毫秒
401.
Lasse Efskind Tore Godal Tove Grude Per F. Marton Jeanne Mossige Sian Høglo 《Cancer immunology, immunotherapy : CII》1978,3(3):207-209
Summary A rapid and progressive thymus atrophy in B6D2 mice following transplantation of Lewis lung carcinoma cells is reported. Spleen weight, however, increased in tumor-carrying animals. Tumor extracts failed to induce these alterations. The mechanism of these perturbations of the immune system in tumor-carrying animals is discussed.This work was supported by the Norwegian Cancer Society 相似文献
402.
403.
Why the free floating macrophyte Stratiotes aloides mainly grows in highly CO2-supersaturated waters
We examined how the freely floating macrophyte, Stratiotes aloides L., sampled from a CO2-supersaturated pond, changes leaf morphology, photosynthesis and inorganic carbon acquisition during its different submerged and emerged life stages in order to evaluate whether S. aloides requires consistently supersaturated CO2 conditions to grow and complete its life cycle. Submerged rosettes formed from over-wintering turions had typical traits of submerged plants with high specific leaf area and low chlorophyll a concentrations. Emergent leaf parts of mature, floating specimens had typical terrestrial traits with stomata, low specific leaf area and high chlorophyll a content, while offsets formed vegetatively and basal, submerged parts of mature plants showed traits in between. All submerged leaf types exhibited some ability to use HCO3− but only rosettes formed from turions had efficient HCO3− use. Rosettes also had the highest CO2 affinity and maximum CO2-saturated photosynthesis in water. Half-saturation constants for CO2 (21–74 μM CO2) were for all submerged leaf parts 5–140 times lower than the concentrations of free CO2 in the pond (350–2800 μM CO2). Emergent leaves were less efficient in water but had significantly higher photosynthesis than submerged, mature leaf parts in air, and rates of photosynthesis of emergent leaves in air were three to five times higher than rates of CO2-saturated photosynthesis of the three submerged leaf types in water. Underwater photosynthetic rates estimated at CO2 concentrations corresponding to air equilibrium were not sufficiently high to support any noticeable growth except for rosettes, in which bicarbonate utilization combined with high CO2 affinity resulted in photosynthetic rates corresponding to almost 34% of maximum rates at high free CO2. We conclude that S. aloides requires consistently high CO2-supersaturation to support high growth and to complete its life cycle, and we infer that this requirement explains why S. aloides mainly grows in ponds, ditches and reed zones that are characterized by strong CO2-supersaturation. 相似文献
404.
Beetle genitalia are usually described only for taxonomic purposes without considering the possible function of structures.
Exceptions are sporadic detailed studies on single species. We studied genital structures in the subfamilies of Cerambycidae
and outlined assumptions on the function of these structures and the implications for the phylogeny of the Cerambycidae. We
found that male genitalia in particular are taxon-specific on a higher taxonomic level; e.g., the parameres are widely variable
in Cerambycinae, while in most Lamiinae species they appear relatively uniform and differ from those of the Cerambycinae.
Internal sac structures are very different among the various subfamilies. Small backwards-pointing spines are the most common
armature of the internal sac. The female genitalia are less variable, although ovipositor morphology may differ among subfamilies.
In most species, the connection between the mates during copulation is achieved by the long internal sac and the ovipositor
only, whereas the median lobe and parameres are in contact with the female abdomen only at the beginning of copulation. Cerambycinae
and Lepturinae have a basal swelling of the endophallus to prevent it from sliding back into the male abdomen during copulation.
The long internal sac functions in connecting the mates and guaranteeing the sperm transfer. 相似文献
405.
Kenneth Klingenberg Barfod Lasse Smidt Karen A. Krogfelt Lars Andrup 《Biocontrol Science and Technology》2010,20(9):1001-1011
Translocation of viable cells from a Bacillus thuringiensis israelensis-based biopesticide to inner organs in a mouse model was studied. Mice were exposed to the originally formulated product through the lungs and gastrointestinal tract by intratracheal instillation. Colony forming units (CFU) were grown from lungs, caecum, spleen and liver on Bacillus cereus-specific agar (BCSA) after 24 h and finally determined to be biopesticide strain B. t. israelensis by large plasmid profile. No CFU were found in spleen or liver of the control mice or in any aerosol background or material. We have shown that viable cells from the commercial product can translocate to spleen and liver of immunocompetent mice in a dose-dependent manner. Furthermore, we discuss the methods of exposure and how bacterial translocation should be taken into consideration when evaluating the safety of novel or reintroduced biopesticides in the future. 相似文献