全文获取类型
收费全文 | 4603篇 |
免费 | 299篇 |
国内免费 | 121篇 |
出版年
2024年 | 9篇 |
2023年 | 41篇 |
2022年 | 108篇 |
2021年 | 182篇 |
2020年 | 123篇 |
2019年 | 133篇 |
2018年 | 154篇 |
2017年 | 129篇 |
2016年 | 199篇 |
2015年 | 291篇 |
2014年 | 304篇 |
2013年 | 347篇 |
2012年 | 398篇 |
2011年 | 364篇 |
2010年 | 233篇 |
2009年 | 184篇 |
2008年 | 246篇 |
2007年 | 224篇 |
2006年 | 183篇 |
2005年 | 156篇 |
2004年 | 147篇 |
2003年 | 113篇 |
2002年 | 113篇 |
2001年 | 74篇 |
2000年 | 84篇 |
1999年 | 53篇 |
1998年 | 30篇 |
1997年 | 26篇 |
1996年 | 35篇 |
1995年 | 23篇 |
1994年 | 14篇 |
1993年 | 15篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 26篇 |
1989年 | 14篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 16篇 |
1985年 | 8篇 |
1983年 | 9篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1976年 | 7篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1971年 | 8篇 |
1969年 | 9篇 |
1968年 | 12篇 |
排序方式: 共有5023条查询结果,搜索用时 15 毫秒
971.
F Kh Se?fullin T A Atabekov B I Iskhanbekov Z Salikhodzhaev T T Rakhimov 《Radiobiologiia》1986,26(2):238-241
X-Irradiation of animals with a dose of 6 Gy brings about fatty degeneration of the liver and a concurrent destruction of the morphological status in functional activity of the insular apparatus. The administration of coamide promotes the recovery of the morphological and physiological status of the pancreas. 相似文献
972.
973.
Joong Sun Kim Yeonghoon Son Min Ji Bae Seung Sook Lee Sun Hoo Park Hae June Lee Soong In Lee Chang Geun Lee Sung Dae Kim Wol Soon Jo Sung Ho Kim In Sik Shin 《PloS one》2015,10(11)
Although safe doses of radiation have been determined, concerns about the harmful effects of low-dose radiation persist. In particular, to date, few studies have investigated the correlation between low-dose radiation and disease development. Asthma is a common chronic inflammatory airway disease that is recognized as a major public health problem. In this study, we evaluated the effects of low-dose-rate chronic irradiation on allergic asthma in a murine model. Mice were sensitized and airway-challenged with ovalbumin (OVA) and were exposed to continuous low-dose-rate irradiation (0.554 or 1.818 mGy/h) for 24 days after initial sensitization. The effects of chronic radiation on proinflammatory cytokines and the activity of matrix metalloproteinase-9 (MMP-9) were investigated. Exposure to low-dose-rate chronic irradiation significantly decreased the number of inflammatory cells, methylcholine responsiveness (PenH value), and the levels of OVA-specific immunoglobulin E, interleukin (IL)-4, and IL-5. Furthermore, airway inflammation and the mucus production in lung tissue were attenuated and elevated MMP-9 expression and activity induced by OVA challenge were significantly suppressed. These results indicate that low-dose-rate chronic irradiation suppresses allergic asthma induced by OVA challenge and does not exert any adverse effects on asthma development. Our findings can potentially provide toxicological guidance for the safe use of radiation and relieve the general anxiety about exposure to low-dose radiation. 相似文献
974.
薄壳山核桃(Carya illinoensis)富含酚类代谢物,具有显著的抗氧化活性。近年来,我国薄壳山核桃产业快速发展,种植面积迅速扩大。明确薄壳山核桃中的酚类代谢物组成及保健功效对于促进健康产业发展具有重要意义。迄今为止,从薄壳山核桃中已检测出酚类代谢物67个,其中包括单宁36个、类黄酮22个、酚酸9个,水解后检测出酚类代谢物苷元34个。该文主要对薄壳山核桃酚类代谢物的组成、提取方法、含量、药理活性及与采后贮藏特性的关系进行综述,以期为今后深入研究薄壳山核桃酚类代谢物与其生理活性的关系及挖掘薄壳山核桃酚类代谢物的保健价值提供依据。 相似文献
975.
976.
Excised roots of various ages from Crandon and Hansen clones of Populus alba x P. grandidentata were tested for their regeneration capacity. Sixty-day-old excised roots that contained root tips were found to be most suitable. The highest number of shoots (an average of 111 shoots/root segment with Crandon and 98 with Hansen) was obtained by adding 22M and 14M zeatin to the medium, respectively. The two clones of hybrid poplar responded similarly to growth regulator treatments; however, the number of shoots produced was greater from the root organs derived from Crandon clones. Regenerated shoots were rooted in basal Woody Plant Medium without any growth regulators. Successful transplantation into soil and growth was achieved with all plants. 相似文献
977.
G Iu Lipskaia V B Se?bil' L P Malyshkina V N Gidirim S G Drozdov 《Molekuliarnaia genetika, mikrobiologiia i virusologiia》1985,(9):27-32
Twelve poliovirus isolates of serotype 3 from patients with paralytic poliomyelitis have been analyzed by oligonucleotide mapping of the viral genomes. All the studied strains were isolated from patients in different regions of the Moldavian SSR in 1982. The maps of all isolates are similar but they do not practically possess any large oligonucleotides characteristic of the vaccine strain of type 3 poliovirus. It is concluded that a wild neurovirulent strain of type 3 poliovirus, that circulated in 1982 in the Moldavian SSR was the cause of paralytic poliomyelitis cases. All the studied isolates are suggested to have been derived relatively recently from the common ancestor. 相似文献
978.
本文对苯并[a]吖啶和苯并[c]吖啶衍生物中具有较确切致癌活性标度的40个化合物,进行了HMO计算。对计算所得的分子轨道参数进行了多元回归分析,建立了致癌活性与分子轨道参数的定量关系式。该式对致癌与非致癌物质的正确区分率为90%。 相似文献
979.
980.
L B Jorde S J Hasstedt E R Ritvo A Mason-Brothers B J Freeman C Pingree W M McMahon B Petersen W R Jenson A Mo 《American journal of human genetics》1991,49(5):932-938
A complex segregation analysis of autism in 185 Utah families was carried out using the mixed model. The 209 affected individuals in these families represent nearly complete ascertainment of the autistic cases born in Utah between 1965 and 1984. The sibling recurrence risk for autism was 4.5% (95% confidence limits 2.8%-6.2%). Likelihoods were maximized for major-gene models, a polygenic model, a sibling-effect model, and a mixed model consisting of major-gene and shared-sibling effects. The analysis provided no evidence for major-locus inheritance of autism. Subdivision of the sample according to the probands' IQ levels showed that sibling recurrence risk did not vary consistently with IQ level. A segregation analysis of families in which the proband had an IQ less than 50 also failed to provide evidence for a major locus. However, because of the etiologic heterogeneity of this disorder, genetic analysis of other meaningful subsets of families could prove informative. 相似文献