全文获取类型
收费全文 | 6556篇 |
免费 | 660篇 |
国内免费 | 26篇 |
出版年
2022年 | 66篇 |
2021年 | 113篇 |
2020年 | 50篇 |
2019年 | 90篇 |
2018年 | 113篇 |
2017年 | 100篇 |
2016年 | 151篇 |
2015年 | 313篇 |
2014年 | 343篇 |
2013年 | 394篇 |
2012年 | 457篇 |
2011年 | 478篇 |
2010年 | 305篇 |
2009年 | 236篇 |
2008年 | 313篇 |
2007年 | 310篇 |
2006年 | 324篇 |
2005年 | 282篇 |
2004年 | 266篇 |
2003年 | 195篇 |
2002年 | 191篇 |
2001年 | 188篇 |
2000年 | 163篇 |
1999年 | 106篇 |
1998年 | 64篇 |
1997年 | 53篇 |
1996年 | 56篇 |
1995年 | 44篇 |
1994年 | 51篇 |
1993年 | 41篇 |
1992年 | 113篇 |
1991年 | 80篇 |
1990年 | 84篇 |
1989年 | 96篇 |
1988年 | 63篇 |
1987年 | 69篇 |
1986年 | 49篇 |
1985年 | 71篇 |
1984年 | 54篇 |
1983年 | 51篇 |
1982年 | 56篇 |
1980年 | 33篇 |
1979年 | 50篇 |
1978年 | 40篇 |
1977年 | 39篇 |
1976年 | 38篇 |
1975年 | 50篇 |
1974年 | 48篇 |
1973年 | 57篇 |
1971年 | 31篇 |
排序方式: 共有7242条查询结果,搜索用时 15 毫秒
1.
Wen-Yeh Hsieh Tang-Ching Kuan Kun-Shan Cheng Yan-Chiou Liao Mu-Yuan Chen Pei-Heng Lin Yuan-Chang Hsu Chen-Yi Huang Wei-Hua Hsu Sheng-Yao Yu Chih-Sheng Lin 《International journal of biological sciences》2012,8(8):1197-1205
Objective: Pleural effusion is common problem, but the rapid and reliable diagnosis for specific pathogenic effusions are lacking. This study aimed to identify the diagnosis based on clinical variables to differentiate pleural tuberculous exudates from other pleural effusions. We also investigated the role of renin-angiotensin system (RAS) and matrix metalloproteinase (MMPs) in the pathogenesis of pleural exudates.Experimental design: The major components in RAS and extracellular matrix metabolism, including angiotensin converting enzyme (ACE), ACE2, MMP-2 and MMP-9 activities, were measured and compared in the patients with transudative (n = 45) and exudative (n = 80) effusions. The exudative effusions were come from the patients with tuberculosis (n = 20), pneumonia (n = 32), and adenocarcinoma (n = 28).Results: Increased ACE and equivalent ACE2 activities, resulting in a significantly increased ACE/ACE2 ratio in exudates, were detected compared to these values in transudates. MMP-9 activity in exudates was significantly higher than that in transudates. The significant correlation between ACE and ACE2 activity that was found in transudates was not found in exudates. Advanced analyses showed significantly increased ACE and MMP-9 activities, and decreased ACE2 activity in tuberculous pleural effusions compared with those in pneumonia and adenocarcinoma effusions. The results indicate that increased ACE and MMP-9 activities found in the exudates were mainly contributed from a higher level of both enzyme activities in the tuberculous pleural effusions.Conclusion: Interplay between ACE and ACE2, essential functions in the RAS, and abnormal regulation of MMP-9 probably play a pivotal role in the development of exudative effusions. Moreover, the ACE/ACE2 ratio combined with MMP-9 activity in pleural fluid may be potential biomarkers for diagnosing tuberculous pleurisy. 相似文献
2.
Somatic embryogenesis and plantlet formation were obtained from 60–75 day old cell cultures of carnation. Callus was generated on MS basal medium supplemented with 2,4-dichchlorophenoxy acetic acid (2,4-D). Removal of 2,4-D during subsequent subculturing of cell suspensions resulted in formation of embroids. These somatic embryos originated from single cells and their early development proceeded normally with clearly defined apical and root meristems. Some embryos developed into plants and were acclimatized to ex vitro conditions. 相似文献
3.
4.
M T Hsieh H C Chen P H Hsu T Shibuya 《Proceedings of the National Science Council, Republic of China. Part B, Life sciences》1986,10(1):43-48
Previously, it was found that the ancient Chinese remedy of Suanzaorentang could be a promising anxiolytic drug (Chen and Hsieh, 1985a, Chen and Hsieh, 1985b). To understand the mechanism of the action of Suanzaorentang, the effects of Suanzaorentang on behavior changes and central monoamines and their metabolites were studied in rats. It was found that Suanzaorentang significantly (1) prolonged the period from the onset of clonic to tonic convulsions induced by pentylenetetrazol or picrotoxin, (2) prolonged the sleep duration induced by hexobarbital, (3) reduced locomotor activity, (4) enhanced the hypomotility induced by alpha-MT, (5) reduced the locomotor stimulation produced by levodopa plus benserazide, and (6) reduced central HVA, VMA, and 5-HIAA, but had no significant effects on central DA, NA, and 5-HT. These facts implied that Suanzaorentang decreased the turnover rate of central monoamines and central catecholaminergic activity. 相似文献
5.
6.
7.
Summary The kinetics of thermal deactivation for thermostable DNA polymerase enzymes were investigated by using the experimental data published elsewhere (Nielson et al. 1996. Strategies. 9, 7–8). The order of deactivation (a) and the deactivation rate constants (k
d) were determined for different Taq DNA polymerase enzymes and were found to be of first order. 相似文献
8.
9.
Jean L. Santos Paulo R. Yamasaki Chung Man Chin Célio H. Takashi Fernando R. Pavan Clarice Q.F. Leite 《Bioorganic & medicinal chemistry》2009,17(11):3795-3799
New phthalimide derivatives were easily prepared through condensation of phthalic anhydride and selected amines with variable yields (70–90%). All compounds (3a–l) were evaluated against Mycobacterium tuberculosis H37Rv using Alamar Blue susceptibility. The compounds 3c, 3i, and 3l have the minimum inhibitory concentrations (MICs) of 3.9, 7.8, and 5.0 μg/mL, respectively, and could be considered new lead compounds in the treatment of tuberculosis and multi-drug resistant tuberculosis. 相似文献
10.