全文获取类型
收费全文 | 161029篇 |
免费 | 29367篇 |
国内免费 | 17609篇 |
专业分类
化学 | 127185篇 |
晶体学 | 1950篇 |
力学 | 7810篇 |
综合类 | 1090篇 |
数学 | 18059篇 |
物理学 | 51911篇 |
出版年
2024年 | 446篇 |
2023年 | 2493篇 |
2022年 | 4643篇 |
2021年 | 4869篇 |
2020年 | 6070篇 |
2019年 | 7006篇 |
2018年 | 5426篇 |
2017年 | 4941篇 |
2016年 | 9009篇 |
2015年 | 9263篇 |
2014年 | 10632篇 |
2013年 | 13283篇 |
2012年 | 14253篇 |
2011年 | 13969篇 |
2010年 | 11081篇 |
2009年 | 10735篇 |
2008年 | 10769篇 |
2007年 | 9457篇 |
2006年 | 8718篇 |
2005年 | 7503篇 |
2004年 | 5981篇 |
2003年 | 4923篇 |
2002年 | 5396篇 |
2001年 | 4189篇 |
2000年 | 3777篇 |
1999年 | 2918篇 |
1998年 | 2169篇 |
1997年 | 1912篇 |
1996年 | 1861篇 |
1995年 | 1639篇 |
1994年 | 1477篇 |
1993年 | 1197篇 |
1992年 | 1081篇 |
1991年 | 947篇 |
1990年 | 778篇 |
1989年 | 621篇 |
1988年 | 458篇 |
1987年 | 414篇 |
1986年 | 401篇 |
1985年 | 323篇 |
1984年 | 215篇 |
1983年 | 175篇 |
1982年 | 148篇 |
1981年 | 90篇 |
1980年 | 71篇 |
1979年 | 38篇 |
1978年 | 30篇 |
1976年 | 28篇 |
1975年 | 24篇 |
1957年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Sergio Ayala‐Mar Javier Donoso‐Quezada Roberto C. Gallo‐Villanueva Victor H. Perez‐Gonzalez Jos Gonzlez‐Valdez 《Electrophoresis》2019,40(23-24):3036-3049
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed. 相似文献
82.
当前锂离子动力电池电化学模型存在模型复杂、建模难度大、计算效率低、老化评估效果差的问题,本文提出一种考虑电池衰退老化的机理模型(ADME).本文首先通过有限差分法对伪二维(P2D)电化学模型进行离散降阶处理,得到简化伪二维(SP2D)模型.在SP2D模型的基础上,基于阴阳两极发生的副反应导致的衰退老化现象,提出一种考虑电池衰退老化的机理模型.其次,使用多变量偏差补偿最小二乘法实现模型参数辨识.最后通过动力电池衰退老化性能循环实验,对比分析了恒流、脉冲工况下SP2D模型和ADME模型的终端电压输出.结果表明:ADME模型较为简单、计算效率和估算精度高,可以有效评估电池容量老化衰退,得到理想的锂离子动力电池外特性曲线. 相似文献
83.
84.
85.
86.
87.
88.
Triazines are widely used in agriculture around the world as selective pre‐ and post‐emergence herbicides for the control of broad leaf and grassy weeds. With high toxicity and persistence, triazines can contaminate the environment and crops, so the development of rapid and sensitive methods for the determination of different triazines is necessary. Capillary electrophoresis comprises a group of techniques used to separate chemical mixtures. Analytical separation is based on different electrophoretic mobilities. This review focuses on the analysis of triazine herbicides with different modes of capillary electrophoresis, including capillary zone electrophoresis, micellar electrokinetic capillary electrophoresis, capillary electrochromatography and nonaqueous capillary electrophoresis. Determinations of triazines in various matrices such as surface water, groundwater, vegetables, soil and grains are emphasized. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
89.
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
90.
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