全文获取类型
收费全文 | 167652篇 |
免费 | 19247篇 |
国内免费 | 15217篇 |
专业分类
化学 | 78350篇 |
晶体学 | 1234篇 |
力学 | 5997篇 |
综合类 | 730篇 |
数学 | 14212篇 |
物理学 | 39613篇 |
综合类 | 61980篇 |
出版年
2024年 | 519篇 |
2023年 | 2715篇 |
2022年 | 4155篇 |
2021年 | 4903篇 |
2020年 | 5088篇 |
2019年 | 4441篇 |
2018年 | 4350篇 |
2017年 | 4053篇 |
2016年 | 6003篇 |
2015年 | 6427篇 |
2014年 | 8405篇 |
2013年 | 10248篇 |
2012年 | 12240篇 |
2011年 | 12809篇 |
2010年 | 9699篇 |
2009年 | 9597篇 |
2008年 | 10418篇 |
2007年 | 9670篇 |
2006年 | 8788篇 |
2005年 | 7790篇 |
2004年 | 6006篇 |
2003年 | 5043篇 |
2002年 | 4805篇 |
2001年 | 4345篇 |
2000年 | 3784篇 |
1999年 | 4851篇 |
1998年 | 4040篇 |
1997年 | 3875篇 |
1996年 | 3722篇 |
1995年 | 3197篇 |
1994年 | 2907篇 |
1993年 | 2386篇 |
1992年 | 2104篇 |
1991年 | 1917篇 |
1990年 | 1583篇 |
1989年 | 1408篇 |
1988年 | 1084篇 |
1987年 | 777篇 |
1986年 | 594篇 |
1985年 | 367篇 |
1984年 | 227篇 |
1983年 | 169篇 |
1982年 | 134篇 |
1981年 | 85篇 |
1980年 | 71篇 |
1979年 | 34篇 |
1978年 | 30篇 |
1976年 | 28篇 |
1975年 | 28篇 |
1957年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
101.
新冠疫情暴发以来,中国政府和人民秉持人类命运共同体理念,运用一系列先进技术,在较短时间内扭转了国内疫情的严峻形势.在此背景下,为了更好地发挥中国方案在全球抗疫中的作用,文章运用内容分析法和归纳分析法,首先梳理了从人类命运共同体到人类卫生健康共同体的理论逻辑,其次探究了人类卫生健康共同体、全球科技合作与疫情防控之间的结构关系,最后分析了中国疫情防控的有效举措,进而得出结论:中国疫情防控工作的成效离不开人类命运共同体理念的指引和全球科技合作的开展,而中国在平台建设、机制整合及合作网络等领域的方案共享将有助于遏制全球疫情的蔓延. 相似文献
102.
103.
104.
105.
106.
107.
Francesco Segatta David M. Rogers Naomi T. Dyer Ellen E. Guest Zhuo Li Hainam Do Artur Nenov Marco Garavelli Jonathan D. Hirst 《Molecules (Basel, Switzerland)》2021,26(2)
A fully quantitative theory of the relationship between protein conformation and optical spectroscopy would facilitate deeper insights into biophysical and simulation studies of protein dynamics and folding. In contrast to intense bands in the far-ultraviolet, near-UV bands are much weaker and have been challenging to compute theoretically. We report some advances in the accuracy of calculations in the near-UV, which were realised through the consideration of the vibrational structure of the electronic transitions of aromatic side chains. 相似文献
108.
Jia Yang Xingang Li Wenjun Li Xin Xi Qian Du Feng Pan Songqing Liu 《Biomedical chromatography : BMC》2020,34(8):e4857
Because of its unpredictable side effects and efficacy, the anticancer drug docetaxel (DTX) requires improved characterisation of its pharmacokinetic profiles through population pharmacokinetic studies. A sensitive and rugged LC–MS/MS method for the detection of DTX in human plasma was developed and optimised using paclitaxel as an internal standard (IS). The plasma samples underwent rapid extraction using hybrid solid-phase extraction-protein precipitation. The analyte and IS were separated with an isocratic system on a Zorbax Eclipse Plus C18 column using water containing 0.05% acetic acid along with 20 μM of sodium acetate and methanol (30/70, v/v) as the mobile phase. Quantification was performed using a triple quadrupole mass spectrometer through multiple reaction monitoring in positive mode, using the m/z 830.3 → 548.8 and m/z 876.3 → 307.7 transitions for DTX and paclitaxel, respectively. The range of the calibration curve was 1–500 ng/mL for DTX, and the linear correlation coefficient was >0.99. The accuracies ranged from −4.6 to 4.2%, and the precision was no higher than 7.0% for the analytes. No significant matrix effect was observed. Both DTX and the IS showed considerable recovery. This method was finally applied to the establishment of a population pharmacokinetic model to optimise the clinical use of DTX. 相似文献
109.
Karen Beatriz Méndez-Rodríguez Nicté Figueroa-Vega César Arturo Ilizaliturri-Hernandez Mónica Cardona-Alvarado Jaime Antonio Borjas-García Carlos Kornhauser Juan Manuel Malacara Rogelio Flores-Ramírez Francisco Javier Pérez-Vázquez 《Biomedical chromatography : BMC》2020,34(12):e4956
Metabolomics is a potential tool for the discovery of new biomarkers in the early diagnosis of diseases. An ultra-fast gas chromatography system equipped to an electronic nose detector (FGC eNose) was used to identify the metabolomic profile of Volatile Organic Compounds (VOCs) in type 2 diabetes (T2D) urine from Mexican population. A cross-sectional, comparative, and clinical study with translational approach was performed. We recruited twenty T2D patients and twenty-one healthy subjects. Urine samples were taken and analyzed by FGC eNose. Eighty-eight compounds were identified through Kovats's indexes. A natural variation of 30% between the metabolites, expressed by study groups, was observed in Principal Component 1 and 2 with a significant difference (p < 0.001). The model, performed through a Canonical Analysis of Principal coordinated (CAP), allowed a correct classification of 84.6% between healthy and T2D patients, with a 15.4% error. The metabolites 2-propenal, 2-propanol, butane- 2,3-dione and 2-methylpropanal, were increased in patients with T2D, and they were strongly correlated with discrimination between clinically healthy people and T2D patients. This study identified metabolites in urine through FGC eNose that can be used as biomarkers in the identification of T2D patients. However, more studies are needed for its implementation in clinical practice. 相似文献
110.
Wenqing Zhang Dr. Jiuxing Li Prof. Dr. Bruno Salena Prof. Dr. Yingfu Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(3):592-596
DNA detection is usually conducted under nondenaturing conditions to favor the formation of Watson–Crick base-paring interactions. However, although such a setting is excellent for distinguishing a single-nucleotide polymorphism (SNP) within short DNA sequences (15–25 nucleotides), it does not offer a good solution to SNP detection within much longer sequences. Here we report on a new detection method capable of detecting SNP in a DNA sequence containing 35–90 nucleotides. This is achieved through incorporating into the recognition DNA sequence a previously discovered DNA molecule that forms a stable G-quadruplex in the presence of 7 molar urea, a known condition for denaturing DNA structures. The systems are configured to produce both colorimetric and fluorescent signals upon target binding. 相似文献