全文获取类型
收费全文 | 1603篇 |
免费 | 113篇 |
国内免费 | 4篇 |
专业分类
1720篇 |
出版年
2024年 | 5篇 |
2023年 | 14篇 |
2022年 | 49篇 |
2021年 | 77篇 |
2020年 | 67篇 |
2019年 | 90篇 |
2018年 | 73篇 |
2017年 | 49篇 |
2016年 | 69篇 |
2015年 | 83篇 |
2014年 | 79篇 |
2013年 | 105篇 |
2012年 | 134篇 |
2011年 | 118篇 |
2010年 | 67篇 |
2009年 | 43篇 |
2008年 | 64篇 |
2007年 | 72篇 |
2006年 | 77篇 |
2005年 | 50篇 |
2004年 | 44篇 |
2003年 | 32篇 |
2002年 | 31篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 19篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1972年 | 4篇 |
1969年 | 9篇 |
1968年 | 4篇 |
1967年 | 4篇 |
排序方式: 共有1720条查询结果,搜索用时 15 毫秒
1.
The objective of this study is to compare the thermal stress changes in the tooth microstructures and the hydrodynamic changes of the dental fluid under hot and cold stimuli. The dimension of the microstructures of eleven cats’ teeth was measured by scanning electron microscopy, and the changes in thermal stress during cold and hot stimulation were calculated by 3D fluid–structure interaction modeling. Evaluation of results, following data validation, indicated that the maximum velocities in cold and hot stimuli were ??410.2?±?17.6 and +?205.1?±?8.7 µm/s, respectively. The corresponding data for maximum thermal stress were ??20.27?±?0.79 and +?10.13?±?0.24 cmHg, respectively. The thermal stress caused by cold stimulus could influence almost 2.9 times faster than that caused by hot stimulus, and the durability of the thermal stress caused by hot stimulus was 71% greater than that by cold stimulus under similar conditions. The maximum stress was on the tip of the odontoblast, while the stress in lateral walls of the odontoblast and terminal fibril was very weak. There is hence a higher possibility of pain transmission with activation of stress-sensitive ion channels at the tip of the odontoblast. The maximum thermal stress resulted from the cold stimulus is double that produced by the hot stimulus. There is a higher possibility of pain transmission in the lateral walls of the odontoblast and terminal fibril by releasing mediators during the cold stimulation than the hot stimulation. These two reasons can be associated with a greater pain sensation due to intake of cold liquids. 相似文献
2.
Mangoes (Mangifera indica) are grown in many warm regions of the world; for example, in Australia, Brazil, India, South America, and the United States (California and Florida), and along the shores of the Mediterranean sea (Egypt, Italy, and Spain). In Egypt, many varieties yielding delicious fruits are grown in large quantities (50,000 tons annually). Mango kernels are used for feeding mammals and chickens. Starch has been isolated from mango and its physical properties studied.The aim of the present work was to study the polysaccharides present in mango kernels. 相似文献
3.
Jaydari Amin Esmaeili Fard Barzegar Peyman Forouharmehr Ali Kakanezhadifard Ali Nazifi Narges 《International journal of peptide research and therapeutics》2019,25(3):1127-1133
International Journal of Peptide Research and Therapeutics - Query fever is an important disease caused by Coxiella burnetii, therefore vaccination against this disease is so crucial. Com1 is one... 相似文献
4.
O M Amin 《The Journal of parasitology》1987,73(2):278-289
Pomphorhynchus bulbocolli Linkins in Van Cleave, 1919, was considerably more common in fishes of the river-connected Tichigan Lake than of the landlocked Silver Lake, southeastern Wisconsin. It is reported from 17 species of principal, accessory, and occasional definitive hosts (new record in Moxostoma carinatum) and from 13 species of paratenic hosts (new records in Amia calva, Ictalurus punctatus, Lepomis cyanellus, and Pomoxis nigromaculatus). Infection patterns were influenced by fish species, feeding behavior, temperature, availability of intermediate host, type of water body, fish movement, and changes in fish host community. Host roles are not fixed but are often interchangeable. A seasonal cycle in prevalence, intensity, and maturation was evident, with greatest abundance and maturation during summer and recruitment during summer and autumn. Recruitment of new infections, development, and release of eggs, however, occurred all year. Sex ratio changed from near equal in new infections to one more highly in favor of females in older adults. Female fish were considerably more frequently and heavily infected than males. No relationship with fish age (size) was evident. Worms were mostly attached in posterior intestinal locations but initial establishment sites correlated with temperature. Translocation of P. bulbocolli due to competitive exclusion in concurrent infections was not observed. The significance of extraintestinal larval forms in the cycle of transmission was noted. 相似文献
5.
6.
The heat shock consensus sequence is not sufficient for hsp70 gene expression in Drosophila melanogaster. 总被引:24,自引:13,他引:11
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A hybrid gene in which the expression of an Escherichia coli beta-galactosidase gene was placed under the control of a Drosophila melanogaster 70,000-dalton heat shock protein (hsp70) gene promoter was constructed. Mutant derivatives of this hybrid gene which contained promoter sequences of different lengths were prepared, and their heat-induced expression was examined in D. melanogaster and COS-1 (African green monkey kidney) cells. Mutants with 5' nontranscribed sequences of at least 90 and up to 1,140 base pairs were expressed strongly in both cell types. Mutants with shorter 5' extensions (of at least 63 base pairs) were transcribed and translated efficiently in COS-1 but not at all in D. melanogaster cells. Thus, in contrast to the situation in COS-1 cells, the previously defined heat shock consensus sequence which is located between nucleotides 62 and 48 of the hsp70 gene 5' nontranscribed DNA segment is not sufficient for the expression of the D. melanogaster gene in homologous cells. A second consensus-like element 69 to 85 nucleotides upstream from the cap site is postulated to be also involved in the heat-induced expression of the hsp70 gene in D. melanogaster cells. 相似文献
7.
8.
9.
J. V. Amin 《Plant and Soil》1969,31(2):365-373
10.
A. V. Gussev N. M. Ali K. N. Abdul-Ameer S. M. Amin K. Molnár 《Systematic parasitology》1993,25(3):229-237
Four new Dactylogyrus species are described and two redescribed from cyprinids of the River Tigris, Iraq. These are as follows: Dactylogyrus barbioides n. sp. from Barbus grypus; D. orbus n. sp. from Barbus lacerta; D. barbuli n. sp. from Barbus barbulus; D. macrostomi n. sp. from Cyprinion macrostomi; D. pavlovskyi Bychowsky, 1949 from Barbus grypus and Barbus sharpeyi; and D. inutilis Bychowsky, 1949 from Barbus xanthopterus. A phylogenetic and zoogeographical analysis is presented. 相似文献