全文获取类型
收费全文 | 11261篇 |
免费 | 397篇 |
国内免费 | 11篇 |
专业分类
11669篇 |
出版年
2024年 | 29篇 |
2023年 | 58篇 |
2022年 | 137篇 |
2021年 | 204篇 |
2020年 | 158篇 |
2019年 | 190篇 |
2018年 | 281篇 |
2017年 | 250篇 |
2016年 | 362篇 |
2015年 | 575篇 |
2014年 | 659篇 |
2013年 | 796篇 |
2012年 | 952篇 |
2011年 | 880篇 |
2010年 | 535篇 |
2009年 | 506篇 |
2008年 | 671篇 |
2007年 | 606篇 |
2006年 | 557篇 |
2005年 | 520篇 |
2004年 | 448篇 |
2003年 | 423篇 |
2002年 | 367篇 |
2001年 | 230篇 |
2000年 | 194篇 |
1999年 | 171篇 |
1998年 | 79篇 |
1997年 | 73篇 |
1996年 | 51篇 |
1995年 | 33篇 |
1994年 | 39篇 |
1993年 | 28篇 |
1992年 | 65篇 |
1991年 | 61篇 |
1990年 | 51篇 |
1989年 | 48篇 |
1988年 | 45篇 |
1987年 | 37篇 |
1986年 | 32篇 |
1985年 | 34篇 |
1984年 | 21篇 |
1983年 | 24篇 |
1982年 | 16篇 |
1981年 | 11篇 |
1979年 | 20篇 |
1978年 | 15篇 |
1977年 | 11篇 |
1976年 | 16篇 |
1975年 | 14篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Ahmed H.E. Hassan Min Chang Cho Hye In Kim Ji Seul Yang Kyung Tae Park Ji Young Hwang Choon-Gon Jang Ki Duk Park Yong Sup Lee 《Bioorganic & medicinal chemistry》2018,26(18):5069-5078
CRA13; a peripheral dual CB1R/CB2R agonist with clinically proven analgesic properties, infiltrates into CNS producing adverse effects due to central CB1R agonism. Such adverse effects might be circumvented by less lipophilic compounds with attenuated CB1R affinity. Metabolism produces less lipophilic metabolites that might be active metabolites. Some CRA13 oxidative metabolites and their analogues were synthesized as less lipophilic CRA13 analogues. Probing their CB1R and CB2R activity revealed the alcohol metabolite 8c as a more potent and more effective CB2R ligand with attenuated CB1R affinity relative to CRA13. Also, the alcohol analogue 8b and methyl ester 12a possessed enhanced CB2R affinity and reduced CB1R affinity. The CB2R binding affinity of alcohol analogue 8b was similar to CRA13 while that of methyl ester 12a was more potent. In silico study provided insights into the possible molecular interactions that might explain the difference in the elicited biological activity of these compounds. 相似文献
2.
The objective of the experiment was to use starch processing waste as an alternative growth medium for cultivation of mycelia of the mushroom Phellinus linteus and to find an optimum condition under solid-state cultivation. Response surface analysis along with a central composite design was successfully applied to approximate the simultaneous effects of the substrate concentration (16-36 g l(-1)), pH (4.5-6.5), and temperature (25-35 degrees C) on the mycelial growth rate. In the model, pH and temperature significantly affected the mycelial growth but substrate concentration did not. The optimal substrate concentration, pH, and temperature for maximizing growth rate of P. linteus mycelia were found to be 16.5 g l(-1), pH 6.0, and 29.7 degrees C, respectively. Subsequent verification of these levels agreed with model predictions and the maximum mycelial growth rate at these conditions was 6.1 +/- 0.8 mm day(-1). Therefore, the results of the experiments suggest that starch processing waste could be utilized as a growth substrate for the cultivation of the mushroom mycelia of P. linteus, enhancing the usefulness of this byproduct of the starch manufacturing industry. This approach is likely to be useful for establishing similar parameters for the cultivation of other fungi. 相似文献
3.
4.
A slowly growing microaerophilic Helicobacter strain was isolated from the ceca and fecal pellets of Korean wild mice (Mus musculus molossinus). This bacterial strain possessed a pair of nonsheathed bipolar flagella, was positive for urease, catalase and oxidase, and reduced nitrate to nitrite. It proved susceptible to nalidixic acid and resistant to cephalodine, and did not hydrolyze hippurate. On the basis of phenotypic characteristics and 16S rRNA gene sequence analysis, the isolate represents a new species of the genus Helicobacter, for which the name Helicobacter muricola sp. nov. is proposed; the type strain of the new species is w-06T. 相似文献
5.
6.
Tissue expression and cellular localization of phospholipid hydroperoxide glutathione peroxidase (PHGPx) mRNA in male mice 总被引:1,自引:0,他引:1
Baek IJ Seo DS Yon JM Lee SR Jin Y Nahm SS Jeong JH Choo YK Kang JK Lee BJ Yun YW Nam SY 《Journal of molecular histology》2007,38(3):237-244
Phospholipid hydroperoxide glutathione peroxidase (PHGPx) is an ubiquitous antioxidant enzyme, but the exact expression pattern
in mammalian tissues is still unknown. The expression and cellular localization of PHGPx mRNA were examined in male mice using
real time-polymerase chain reaction and in situ hybridization techniques. The rank order of PHGPx mRNA expression across tissues exhibiting substantial levels of expression
was:testes ≫ heart > cerebrum ≥ ileum > stomach = liver = jejunum ≥ epididymis. In testes, PHGPx mRNA was highly expressed
in spermiogenic cells and Leydig cells. The signal was also expressed in the molecular layer, Purkinje cell layer, and white
matter of cerebellum, the pituicytes of neurohypophysis, the parafollicular cells and follicular basement membrane of thyroid,
the exocrine portion of pancreas, the tubular epithelium of kidney, the smooth muscle cells of arteries, and the red pulp
of spleen. In the gastrointestinal tract, PHGPx mRNA expression was mainly observed in the keratinized surface epithelium
of forestomach, the submucosal glands and serosa layers, and further the Paneth cells of intestines. PHGPx mRNA appeared to
be ubiquitously expressed in the parenchyma of heart, liver, and lung. These results indicate that PHGPx exhibits a cell-
and tissue-specific expression pattern in mice. 相似文献
7.
Chih-Chin Shih Chuan-Chin Huang Shou-Hsien Li Mei-Hsiu Hwang Ling-Ling Lee 《Conservation Genetics》2009,10(6):1845-1847
Ten polymorphic microsatellite markers were developed for the endangered Formosan black bear (Ursus thibetanus formosanus) from a partial genomic library enriched for GAAA repeat. Polymorphism of these loci was evaluated in 27 Formosan black bear specimens of unknown relationship. The number of alleles per locus ranged from 5 to 15 and the observed heterozygosity of each locus ranged from 0.556 to 0.889. These loci should provide useful molecular tools to study conservation genetics of the Formosan black bear and other Asiatic black bears. 相似文献
8.
9.
Cuong DV Warda M Kim N Park WS Ko JH Kim E Han J 《American journal of physiology. Heart and circulatory physiology》2007,293(3):H1457-H1465
In this study, dynamic changes in nitric oxide (NO) and mitochondrial superoxide (O(2)(*-)) were examined during anoxic preconditioning (AP) in rat heart model. AP and anoxia-reoxygenation (A/R) were performed on isolated hearts and single cardiomyocytes. The cellular insult in the form of infarct size and DNA damage were localized and correlated with NO synthases (endothelial and inducible) expression levels. The results showed that endocardium was the most affected region in AP groups, whereas the larger area of infarct was confined to mid- and epicardium in the A/R group. Interestingly, a high-level expression of immunofluorescent NO synthases was restricted to viable areas in the AP. In contrast to the gradual increase in O(2)(*-) level that occurred in the AP group, a sudden massive increase in its level was demonstrated at the onset of reoxygenation in the A/R group. The observed increase in NO production during reoxygenation in the AP group was attenuated by inducible NO synthase inhibitor. The study revealed, on a real-time basis, the role played by preconditioning for modulating NO and O(2)(*-) levels on behalf of cell survival. The results afford a better understanding of cardiac-adapting mechanism during AP and the role of inducible NO synthase in this important phenomenon. 相似文献
10.