全文获取类型
收费全文 | 4564篇 |
免费 | 740篇 |
国内免费 | 425篇 |
专业分类
化学 | 3064篇 |
晶体学 | 57篇 |
力学 | 309篇 |
综合类 | 27篇 |
数学 | 488篇 |
物理学 | 1784篇 |
出版年
2024年 | 18篇 |
2023年 | 117篇 |
2022年 | 171篇 |
2021年 | 197篇 |
2020年 | 185篇 |
2019年 | 185篇 |
2018年 | 172篇 |
2017年 | 138篇 |
2016年 | 253篇 |
2015年 | 234篇 |
2014年 | 262篇 |
2013年 | 344篇 |
2012年 | 423篇 |
2011年 | 423篇 |
2010年 | 290篇 |
2009年 | 237篇 |
2008年 | 272篇 |
2007年 | 261篇 |
2006年 | 255篇 |
2005年 | 203篇 |
2004年 | 145篇 |
2003年 | 114篇 |
2002年 | 89篇 |
2001年 | 82篇 |
2000年 | 92篇 |
1999年 | 83篇 |
1998年 | 75篇 |
1997年 | 57篇 |
1996年 | 60篇 |
1995年 | 55篇 |
1994年 | 29篇 |
1993年 | 40篇 |
1992年 | 42篇 |
1991年 | 27篇 |
1990年 | 26篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 2篇 |
1983年 | 8篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有5729条查询结果,搜索用时 15 毫秒
971.
Xiaofei Tong Jingguo Bi Yufei Duan Lixiang Li Licheng Wang 《Entropy (Basel, Switzerland)》2022,24(10)
DBTRU was proposed by Thang and Binh in 2015. As a variant of NTRU, the integer polynomial ring is replaced by two binary truncated polynomial rings . DBTRU has some advantages over NTRU in terms of security and performance. In this paper, we propose a polynomial-time linear algebra attack against the DBTRU cryptosystem, which can break DBTRU for all recommended parameter choices. The paper shows that the plaintext can be achieved in less than 1 s via the linear algebra attack on a single PC. 相似文献
972.
In the development of simplex mixed-effects models, random effects in these mixed-effects models are generally distributed in normal distribution. The normality assumption may be violated in an analysis of skewed and multimodal longitudinal data. In this paper, we adopt the centered Dirichlet process mixture model (CDPMM) to specify the random effects in the simplex mixed-effects models. Combining the block Gibbs sampler and the Metropolis–Hastings algorithm, we extend a Bayesian Lasso (BLasso) to simultaneously estimate unknown parameters of interest and select important covariates with nonzero effects in semiparametric simplex mixed-effects models. Several simulation studies and a real example are employed to illustrate the proposed methodologies. 相似文献
973.
With the rapid development of power, energy, electronic information, rail transit, and aerospace industries, nanocomposite electrical insulating materials have been begun to be widely used as new materials. Polymer/inorganic nanocomposite dielectric materials possess excellent physical and mechanical properties. In addition, numerous unique properties, such as electricity, thermal, sound, light, and magnetic properties are exhibited by these materials. First, the macroscopic quantum tunneling effect, small-size effect, surface effect, and quantum-size effect of nanoparticles are introduced. There are a few anomalous changes in the physical and chemical properties of the matrix, which are caused by these effects. Second, the interaction mechanism between the nanoparticles and polymer matrix is introduced. These include infiltration adsorption theory, chemical bonding, diffusion theory, electrostatic theory, mechanical connection theory, deformation layer theory, and physical adsorption theory. The mechanism of action of the interface on the dielectric properties of the composites is summarized. These are the interface trap effect, interface barrier effect, and homogenization field strength effect. In addition, different interfacial structure models were used to analyze the specific properties of nanocomposite dielectric materials. Finally, the research status of the dielectric properties of nanocomposite dielectric materials in the electrical insulation field is introduced. 相似文献
974.
Libo He Yang Liu Junling Xu Jingjing Li Guohua Cheng Jiaxiu Cai Jinye Dang Meng Yu Weiyan Wang Wei Duan Ke Liu 《Molecules (Basel, Switzerland)》2022,27(20)
Advanced glycation end products (AGEs) are the compounds produced by non-enzymatic glycation of proteins, which are involved in diabetic-related complications. To investigate the potential anti-glycation activity of Myriocin (Myr), a fungal metabolite of Cordyceps, the effect of Myr on the formation of AGEs resulted from the glycation of bovine serum albumin (BSA) and the interaction between Myr and BSA were studied by multiple spectroscopic techniques and computational simulations. We found that Myr inhibited the formation of AGEs at the end stage of glycation reaction and exhibited strong anti-fibrillation activity. Spectroscopic analysis revealed that Myr quenched the fluorescence of BSA in a static process, with the possible formation of a complex (approximate molar ratio of 1:1). The binding between BSA and Myr mainly depended on van der Waals interaction, hydrophobic interactions and hydrogen bond. The synchronous fluorescence and UV-visible (UV-vis) spectra results indicated that the conformation of BSA altered in the presence of Myr. The fluorescent probe displacement experiments and molecular docking suggested that Myr primarily bound to binding site 1 (subdomain IIA) of BSA. These findings demonstrate that Myr is a potential anti-glycation agent and provide a theoretical basis for the further functional research of Myr in the prevention and treatment of AGEs-related diseases. 相似文献
975.
Xin-Yao Liu Yu-Miao Wang Xiang-Yu Zhang Mei-Qi Jia Hong-Quan Duan Nan Qin Ying Chen Yang Yu Xiao-Chuan Duan 《Molecules (Basel, Switzerland)》2022,27(20)
Metastasis is an important cause of cancer-related death. Previous studies in our laboratory found that pregnane alkaloids from Pachysandra terminalis had antimetastatic activity against breast cancer cells. In the current study, we demonstrated that treatment with one of the alkaloid derivatives, (Z)-3β-ethylamino-pregn-17(20)-en (1), led to the downregulation of the HIF-1α/VEGF/VEGFR2 pathway, suppressed the phosphorylation of downstream molecules Akt, mTOR, FAK, and inhibited breast cancer metastasis and angiogenesis both in vitro and in vivo. Furthermore, the antimetastasis and antiangiogenesis effects of 1 treatment (40 mg/kg) were more effective than that of Sorafenib (50 mg/kg). Surface plasmon resonance (SPR) analysis was performed and the result suggested that HSP90α was a direct target of 1. Taken together, our results suggested that compound 1 might represent a candidate antitumor agent for metastatic breast cancer. 相似文献
976.
Hui-Hui Yang Hui-Ling Jiang Jia-Hao Tao Chen-Yu Zhang Jian-Bing Xiong Jin-Tong Yang Yu-Biao Liu Wen-Jing Zhong Xin-Xin Guan Jia-Xi Duan Yan-Feng Zhang Shao-Kun Liu Jian-Xin Jiang Yong Zhou Cha-Xiang Guan 《Experimental & molecular medicine》2022,54(11):2077
Necroptosis is the major cause of death in alveolar epithelial cells (AECs) during acute lung injury (ALI). Here, we report a previously unrecognized mechanism for necroptosis. We found an accumulation of mitochondrial citrate (citratemt) in lipopolysaccharide (LPS)-treated AECs because of the downregulation of Idh3α and citrate carrier (CIC, also known as Slc25a1). shRNA- or inhibitor–mediated inhibition of Idh3α and Slc25a1 induced citratemt accumulation and necroptosis in vitro. Mice with AEC-specific Idh3α and Slc25a1 deficiency exhibited exacerbated lung injury and AEC necroptosis. Interestingly, the overexpression of Idh3α and Slc25a1 decreased citratemt levels and rescued AECs from necroptosis. Mechanistically, citratemt accumulation induced mitochondrial fission and excessive mitophagy in AECs. Furthermore, citratemt directly interacted with FUN14 domain-containing protein 1 (FUNDC1) and promoted the interaction of FUNDC1 with dynamin-related protein 1 (DRP1), leading to excessive mitophagy-mediated necroptosis and thereby initiating and promoting ALI. Importantly, necroptosis induced by citratemt accumulation was inhibited in FUNDC1-knockout AECs. We show that citratemt accumulation is a novel target for protection against ALI involving necroptosis.Subject terms: Infection, Respiratory tract diseases 相似文献
977.
978.
Xingxing Lu Huan Xu Xiaoming Zhang Tengda Sun Yufan Lin Yongheng Zhang Honghong Li Xuesheng Li Xinling Yang Hongxia Duan Yun Ling 《Molecules (Basel, Switzerland)》2022,27(18)
Neonicotinoids are important insecticides for controlling aphids in agriculture. Growing research suggested that neonicotinoid insecticides are a key factor causing the decline of global pollinator insects, such as bees. Flupyrimin (FLP) is a novel nicotinic insecticide with unique biological properties and no cross-resistance, and is safe for pollinators. Using FLP as the lead compound, a series of novel compounds were designed and synthesized by replacing the amide fragment with a sulfonamideone. Their structures were confirmed by 1H NMR, 13C NMR and HRMS spectra. Bioassay results showed that compound 2j had good insecticidal activity against Aphis glycines with an LC50 value of 20.93 mg/L. Meanwhile, compound 2j showed significantly lower acute oral and contact toxicity to Apis mellifera. In addition, compound 2j interacted well with the protein in insect acetylcholine binding protein (AChBP). The molecular docking on honeybee nicotinic acetylcholine receptor (nAChR) indicated that the sulfonamide group of compound 2j did not form a hydrogen bond with Arg173 of the β subunit, which conforms to the reported low bee-toxicity conformation. In general, target compound 2j can be regarded as a bee-friendly insecticide candidate. 相似文献
979.
从理论上分析了中子在CCD相机拍摄图像中引起的瞬态干扰噪声的机理,并针对两种不同类型的CCD相机,在能量为14 MeV和2.5 MeV的低强度稳态中子源上开展了实验研究,分析了噪声特征与入射中子能量、入射角度、注量及CCD相机结构的关系。实验结果表明中子瞬态干扰噪声主要表现为脉冲噪声,且出现斑点现象,与理论分析结果相吻合。研究得出了噪声特征随入射中子注量变化的规律,比较了不同能量及不同入射角条件下的噪声特性,并分析了两种不同结构的CCD相机响应特性的差别。 相似文献
980.
由CT切片数据重建得到的三角网格模型常存在数据量大、狭长三角形多等问题,针对这些问题,研究了一种保持特征的高质量三角网格模型的简化优化方法。该方法分为网格简化和网格优化两个阶段。首先,采用基于曲面变化的二次误差度量计算边折叠代价,并按代价值的大小进行迭代的折叠简化,可较好地保持模型表面的特征;其次,通过二阶加权伞算子对简化模型中局部存在的狭长三角形进行优化处理,改善三角网格模型的质量。实验结果表明,该方法能够较好地保持特征区域的细节信息,并可靠地生成高质量、低几何误差的简化模型。 相似文献