全文获取类型
收费全文 | 6675篇 |
免费 | 435篇 |
国内免费 | 11篇 |
专业分类
7121篇 |
出版年
2024年 | 20篇 |
2023年 | 79篇 |
2022年 | 268篇 |
2021年 | 389篇 |
2020年 | 146篇 |
2019年 | 184篇 |
2018年 | 273篇 |
2017年 | 184篇 |
2016年 | 267篇 |
2015年 | 403篇 |
2014年 | 384篇 |
2013年 | 494篇 |
2012年 | 487篇 |
2011年 | 468篇 |
2010年 | 282篇 |
2009年 | 236篇 |
2008年 | 279篇 |
2007年 | 296篇 |
2006年 | 231篇 |
2005年 | 181篇 |
2004年 | 177篇 |
2003年 | 138篇 |
2002年 | 136篇 |
2001年 | 96篇 |
2000年 | 71篇 |
1999年 | 55篇 |
1998年 | 41篇 |
1997年 | 38篇 |
1996年 | 28篇 |
1995年 | 29篇 |
1994年 | 24篇 |
1993年 | 24篇 |
1992年 | 54篇 |
1991年 | 39篇 |
1990年 | 50篇 |
1989年 | 47篇 |
1988年 | 37篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 29篇 |
1984年 | 38篇 |
1983年 | 33篇 |
1982年 | 32篇 |
1981年 | 34篇 |
1980年 | 40篇 |
1979年 | 18篇 |
1978年 | 27篇 |
1977年 | 19篇 |
1974年 | 22篇 |
1973年 | 20篇 |
排序方式: 共有7121条查询结果,搜索用时 0 毫秒
231.
A common issue in bioinformatics is that computational methods often generate a large number of predictions sorted according to certain confidence scores. A key problem is then determining how many predictions must be selected to include most of the true predictions while maintaining reasonably high precision. In nuclear magnetic resonance (NMR)-based protein structure determination, for instance, computational peak picking methods are becoming more and more common, although expert-knowledge remains the method of choice to determine how many peaks among thousands of candidate peaks should be taken into consideration to capture the true peaks. Here, we propose a Benjamini-Hochberg (B-H)-based approach that automatically selects the number of peaks. We formulate the peak selection problem as a multiple testing problem. Given a candidate peak list sorted by either volumes or intensities, we first convert the peaks into -values and then apply the B-H-based algorithm to automatically select the number of peaks. The proposed approach is tested on the state-of-the-art peak picking methods, including WaVPeak [1] and PICKY [2]. Compared with the traditional fixed number-based approach, our approach returns significantly more true peaks. For instance, by combining WaVPeak or PICKY with the proposed method, the missing peak rates are on average reduced by 20% and 26%, respectively, in a benchmark set of 32 spectra extracted from eight proteins. The consensus of the B-H-selected peaks from both WaVPeak and PICKY achieves 88% recall and 83% precision, which significantly outperforms each individual method and the consensus method without using the B-H algorithm. The proposed method can be used as a standard procedure for any peak picking method and straightforwardly applied to some other prediction selection problems in bioinformatics. The source code, documentation and example data of the proposed method is available at http://sfb.kaust.edu.sa/pages/software.aspx. 相似文献
232.
Silvia Maioli Ann B?vner Zeina Ali Maura Heverin Muhammad-Al-Mustafa Ismail Elena Puerta Maria Olin Ahmed Saeed Marjan Shafaati Paolo Parini Angel Cedazo-Minguez Ingemar Bj?rkhem 《PloS one》2013,8(7)
We previously described a heterozygous mouse model overexpressing human HA-tagged 24S-hydroxylase (CYP46A1) utilizing a ubiquitous expression vector. In this study, we generated homozygotes of these mice with circulating levels of 24OH 30–60% higher than the heterozygotes. Female homozygous CYP46A1 transgenic mice, aged 15 months, showed an improvement in spatial memory in the Morris water maze test as compared to the wild type mice. The levels of N-Methyl-D-Aspartate receptor 1, phosphorylated-N-Methyl-D-Aspartate receptor 2A, postsynaptic density 95, synapsin-1 and synapthophysin were significantly increased in the hippocampus of the CYP46A1 transgenic mice as compared to the controls. The levels of lanosterol in the brain of the CYP46A1 transgenic mice were significantly increased, consistent with a higher synthesis of cholesterol. Our results are discussed in relation to the hypothesis that the flux in the mevalonate pathway in the brain is of importance in cognitive functions. 相似文献
233.
Iftikhar Ahmed Rosemary Greenwood Ben de Lacy Costello Norman M. Ratcliffe Chris S. Probert 《PloS one》2013,8(3)
Diagnosing irritable bowel syndrome (IBS) can be a challenge; many clinicians resort to invasive investigations in order to rule out other diseases and reassure their patients. Volatile organic metabolites (VOMs) are emitted from feces; understanding changes in the patterns of these VOMs could aid our understanding of the etiology of the disease and the development of biomarkers, which can assist in the diagnosis of IBS. We report the first comprehensive study of the fecal VOMs patterns in patients with diarrhea-predominant IBS (IBS-D), active Crohn''s disease (CD), ulcerative colitis (UC) and healthy controls. 30 patients with IBS-D, 62 with CD, 48 with UC and 109 healthy controls were studied. Diagnosis of IBS-D was made using the Manning criteria and all patients with CD and UC met endoscopic, histologic and/or radiologic criteria. Fecal VOMs were extracted by solid phase microextraction (SPME) and analyzed by gas chromatography-mass spectrometry (GC-MS). 240 VOMs were identified. Univariate analysis showed that esters of short chain fatty acids, cyclohexanecarboxylic acid and its ester derivatives were associated with IBS-D (p<0.05), while aldehydes were more abundant in IBD (p<0.05). A predictive model, developed by multivariate analysis, separated IBS-D from active CD, UC and healthy controls with a sensitivity of 94%, 96% and 90%; and a specificity of 82%, 80% and 80% respectively (p<0.05). The understanding of the derivation of these VOMs may cast light on the etiology of IBS-D and IBD. These data show that fecal VOMs analyses could contribute to the diagnosis of IBS-D, for which there is no laboratory test, as well as IBD. 相似文献
234.
235.
Shafiq Ullah Fiaz Ahmed Amin Badshah Ataf Ali Altaf Ramsha Raza Bhajan Lal Rizwan Hussain 《PloS one》2013,8(10)
Nano materials with high surface area increase the kinetics and extent of the redox reactions, thus resulting in high power and energy densities. In this study high surface area zinc oxide nanorods have been synthesized by surfactant free ethylene glycol assisted solvothermal method. The nanorods thus prepared have diameters in the submicron range (300∼500 nm) with high aspect ratio. They have uniform geometry and well aligned direction. These nanorods are characterized by XRD, SEM, Specific Surface Area Analysis, solubility in alkaline medium, EDX analysis and galvanostatic charge/discharge studies in Zn/AgO batteries. The prepared zinc oxide nanorods have low solubility in alkaline medium with higher structural stability, which imparts the improved cycle life stability to Zn/AgO cells. 相似文献
236.
Stephanie Melkonian Maria Argos Megan N. Hall Yu Chen Faruque Parvez Brandon Pierce Hongyuan Cao Briseis Aschebrook-Kilfoy Alauddin Ahmed Tariqul Islam Vesna Slavcovich Mary Gamble Parvez I. Haris Joseph H. Graziano Habibul Ahsan 《PloS one》2013,8(11)
Background
We utilized data from the Health Effects of Arsenic Longitudinal Study (HEALS) in Araihazar, Bangladesh, to evaluate the association of steamed rice consumption with urinary total arsenic concentration and arsenical skin lesions in the overall study cohort (N=18,470) and in a subset with available urinary arsenic metabolite data (N=4,517).Methods
General linear models with standardized beta coefficients were used to estimate associations between steamed rice consumption and urinary total arsenic concentration and urinary arsenic metabolites. Logistic regression models were used to estimate prevalence odds ratios (ORs) and their 95% confidence intervals (CIs) for the associations between rice intake and prevalent skin lesions at baseline. Discrete time hazard models were used to estimate discrete time (HRs) ratios and their 95% CIs for the associations between rice intake and incident skin lesions.Results
Steamed rice consumption was positively associated with creatinine-adjusted urinary total arsenic (β=0.041, 95% CI: 0.032-0.051) and urinary total arsenic with statistical adjustment for creatinine in the model (β=0.043, 95% CI: 0.032-0.053). Additionally, we observed a significant trend in skin lesion prevalence (P-trend=0.007) and a moderate trend in skin lesion incidence (P-trend=0.07) associated with increased intake of steamed rice.Conclusions
This study suggests that rice intake may be a source of arsenic exposure beyond drinking water. 相似文献237.
Abdel-Magied Nadia Elkady Ahmed A. Abdel Fattah Salma M. 《Biological trace element research》2020,193(2):410-413
Biological Trace Element Research - This report explains the employing of a combination test of traditional cell culture with a quantitative real-time PCR for assessment of the antiviral effect of... 相似文献
238.
Cai Gaochao Ahmed Mutez Ali Dippold Michaela A. Zarebanadkouki Mohsen Carminati Andrea 《Plant and Soil》2020,447(1-2):579-579
Plant and Soil - In the original version of this article, equations 4 and 9 unfortunately contained errors 相似文献
239.
240.
Saleh Ahmed A. Eltantawy Mohammed S. Gawish Esraa M. Younis Hassan H. Amber Khairy A. Abd El-Moneim Abd El-Moneim E. Ebeid Tarek A. 《Biological trace element research》2020,195(2):506-514
Biological Trace Element Research - The objectives of this study were to investigate the impact of dietary organic mineral mixture (manganese, zinc, and copper) supplementation on reproductive... 相似文献