全文获取类型
收费全文 | 4001篇 |
免费 | 540篇 |
国内免费 | 393篇 |
专业分类
化学 | 2854篇 |
晶体学 | 33篇 |
力学 | 174篇 |
综合类 | 45篇 |
数学 | 594篇 |
物理学 | 1234篇 |
出版年
2024年 | 8篇 |
2023年 | 75篇 |
2022年 | 131篇 |
2021年 | 129篇 |
2020年 | 142篇 |
2019年 | 153篇 |
2018年 | 148篇 |
2017年 | 125篇 |
2016年 | 192篇 |
2015年 | 178篇 |
2014年 | 252篇 |
2013年 | 282篇 |
2012年 | 324篇 |
2011年 | 315篇 |
2010年 | 231篇 |
2009年 | 214篇 |
2008年 | 256篇 |
2007年 | 209篇 |
2006年 | 205篇 |
2005年 | 168篇 |
2004年 | 140篇 |
2003年 | 123篇 |
2002年 | 146篇 |
2001年 | 125篇 |
2000年 | 71篇 |
1999年 | 68篇 |
1998年 | 61篇 |
1997年 | 41篇 |
1996年 | 38篇 |
1995年 | 43篇 |
1994年 | 48篇 |
1993年 | 35篇 |
1992年 | 34篇 |
1991年 | 41篇 |
1990年 | 30篇 |
1989年 | 16篇 |
1988年 | 15篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 16篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1971年 | 5篇 |
1962年 | 3篇 |
排序方式: 共有4934条查询结果,搜索用时 15 毫秒
961.
The analytical conditions for resonant and stationary waves inrotating disks are presented. These conditions are derived from anonlinear plate theory pertaining to initial configurations and areapplicable to rotating disks with initial waviness and/or undergoinglarge-amplitude displacements. The rotational speeds at which theresonant and stationary waves occur for a 3.5-inch diameter computermemory disk are computed. The resonant waves for linear and nonlinear,rotating disks are simulated numerically. It is found that some diskmodes exhibit a hardening effect under which the rotational speeds forthe resonant and stationary waves increase with increasing waveamplitude, while other modes experience a softening effect with thoserotational speeds decreasing with increasing wave amplitude. Therotating-disk resonant spectrum presented in this paper is relevant tothe disk drive industry for determining the range of operationalrotation speed. 相似文献
962.
Zengshun Jiang Xingqi An Yuqin Zhang Xuan Liu Xifeng Qin Yanjie Zhao Huilin Wang Guiyuan Liu Hongsheng Song 《中国光学快报(英文版)》2021,(4):56-61
After the three-dimensional self-affine fractal random surface simulation, we use the optical scattering theory to calculate the deep Fresnel region speckle(DFRS) under consideration of the more strict shadowing effect. The evolution of DFRS with the scattering distance and the intensity probability distribution are studied. It is found that the morphology of the scatterer has an antisymmetric relationship with the intensity distribution of DFRS, and the effect of micro-lenses on the scattering surface causes the intensity probability distribution of DFRS to deviate from the Gaussian speckle in the high light intensity area. 相似文献
963.
964.
为理解绕水翼云空化流动的发展机理和探究水翼吸力面开孔射流的影响,采用密度修正的RNG k-ε湍流模型和Schnerr-Sauer空化模型对原始NACA66(mod)水翼和采用射流后的水翼的云空化非定常过程进行模拟和对比分析;采用在水翼吸力面近壁区设立监测线的方法对近壁区的流场进行监测,得到近壁区汽相体积分数、回射流速度、压力及压力梯度的时空分布云图;开展了云空化流场特性的涡动力学分析,进而分析水翼云空化的发生机理和射流抑制空化的抑制机理.结果表明:游离型空泡在下游溃灭时产生强烈的局部高压,其向上游传播导致前缘空穴的一次回缩,而空穴的二次回缩受回射流的影响.回射流的发展区域受限于较高的压力梯度,高的压力梯度一直存在,但回射流在一个周期内的首次出现需要时间的积累.在水翼吸力面射流使得射流孔附近压力升高,弥补了由于空化和绕流造成的压降,压力梯度增大,抗逆压能力增强,对回射流起到阻挡作用;另一方面,射流使得回射流区域面积和回射流的强度也有所减小,从而对云空化的发展起到抑制的效果.Q准则的涡结构云图相比于汽相体积分数云图能显示复杂的流动结构,前缘附着型空穴和尾缘游离型空穴内存在旋涡,回射流对空穴... 相似文献
965.
Ju-hong Jang Jeong Woong Lee Min Ji Cho Byungtae Hwang Min-Gi Kwon Dong-Hwan Kim Nam-Kyung Lee Jangwook Lee Young-Jun Park Yong Ryoul Yang Jinchul Kim Yong-Hoon Kim Tae Hyeon An Kyoung-Jin Oh Kwang-Hee Bae Jong-Gil Park Jeong-Ki Min 《Experimental & molecular medicine》2022,54(8):1250
Obesity is a growing global epidemic that can cause serious adverse health consequences, including insulin resistance (IR) and nonalcoholic fatty liver disease (NAFLD). Obesity development can be attributed to energy imbalance and metabolic inflexibility. Here, we demonstrated that lack of Kelch-like protein 3 (KLHL3) mitigated the development of obesity, IR, and NAFLD by increasing energy expenditure. KLHL3 mutations in humans cause Gordon’s hypertension syndrome; however, the role of KLHL3 in obesity was previously unknown. We examined differences in obesity-related parameters between control and Klhl3−/− mice. A significant decrease in body weight concomitant with fat mass loss and improved IR and NAFLD were observed in Klhl3−/− mice fed a high-fat (HF) diet and aged. KLHL3 deficiency inhibited obesity, IR, and NAFLD by increasing energy expenditure with augmentation of O2 consumption and CO2 production. Delivering dominant-negative (DN) Klhl3 using adeno-associated virus into mice, thereby dominantly expressing DN-KLHL3 in the liver, ameliorated diet-induced obesity, IR, and NAFLD. Finally, adenoviral overexpression of DN-KLHL3, but not wild-type KLHL3, in hepatocytes revealed an energetic phenotype with an increase in the oxygen consumption rate. The present findings demonstrate a novel function of KLHL3 mutation in extrarenal tissues, such as the liver, and may provide a therapeutic target against obesity and obesity-related diseases.Subject terms: Obesity, Homeostasis 相似文献
966.
967.
He Liu Mengnan An Hongyang Si Yuhang Shan Chuantao Xu Gang Hu Yunbo Xie Dongyang Liu Shujun Li Rui Qiu Chong Zhang Yuanhua Wu 《Molecules (Basel, Switzerland)》2022,27(17)
As an important microbial resource, Actinomycetes, especially Streptomyces, have important application values in medicine and biotechnology. Streptomyces fungicidicus SYH3 was isolated from soil samples in tomato-growing areas and showed good inhibitory effects on Alternaria solani in tomato. To obtain pure active compounds, SYH3 fermentation broth was subjected to XAD-16 macroporous resin and silica gel column chromatography. Combined with the repeated preparation and separation of preparative high-performance liquid chromatography (HPLC), a total of four monomer compounds were obtained after activity tracking. Compound 4 was identified as a new six-membered lactone ring compound named 6-(5-hydroxy-6-methylheptyl)-5,6-dihydro-2H-pyran-2-one by 1D and 2D nuclear magnetic resonance (NMR) data and mass spectrometry (MS). The other three active compounds belong to the cyclodipeptide, and their half maximal inhibitory concentration (IC50) values against A. solani were 43.4, 42.9, and 30.6 μg/mL, respectively. Compound 4 significantly inhibited the spore germination and induced swollen and deformed local hyphae of A. solani with an IC50 value of 24.9 μg/mL. Compound 4 also had broad-spectrum antifungal activity and had a good antifungal effect on the tested plant-pathogenic fungi. The modes of action of new compound (4) still require further investigation, representing a novel and effective anti-fungal agent for future application. 相似文献
968.
Wang Zhang Xinjie Liu Xun Sun Rongchun Han Nianjun Yu Juan Liang An Zhou 《Molecules (Basel, Switzerland)》2022,27(19)
It is generally believed that fresh Dendrobium officinale (FDO) has more significant pharmacological activity than dried Dendrobium officinale (DDO); however, the difference has not been clearly shown. Our study compared their antioxidant properties both in vitro and in vivo, and the molecular weight arrangement and monosaccharide composition of the fresh Dendrobium officinale polysaccharides (FDOPs) and the dried Dendrobium officinale polysaccharides (DDOPs) were analyzed by HPLC-GPC and GC-MS. The results showed that the FDO and its polysaccharides had more significant effects on scavenging DPPH, ABTS, and hydroxyl radicals than the DDO. In addition, both the FDO and DDO significantly reduced lipid peroxidation levels and increased the SOD, T-AOC, CAT, and GSH levels in mice with acute liver damage caused by CCl4, while the FDO and its polysaccharides were more effective. Histopathological analysis further verified the protective effect of the Dendrobium polysaccharides on CCl4-induced liver injury. The determination of the polysaccharides revealed that the polysaccharide and mannose contents of the FDO were significantly higher than their dried counterparts, and the homogeneous arrangement of the polysaccharides in the FDO was degraded into three polysaccharide fragments of different molecular weights in the DDO. Overall, our data identified differences in the antioxidant activities of the FDO and DDO, as well as the reasons for these differences. 相似文献
969.
Seung Wha Jo Ji-Hyun An Dong-Shin Kim Eun Jung Yim Hyeon-Jin Kang Hyun-Jin Kim 《Molecules (Basel, Switzerland)》2022,27(19)
Aspergillus oryzae (A. oryzae) is an important starter in the fermentation of koji and moromi. However, the effect of different A. oryzae strains on the quality of moromi has rarely been studied. For this reason, this study analyzed the physicochemical properties, enzyme activity, sensory quality, and metabolite profiles of moromi samples fermented using two strains (A. oryzae KCCM12012P (moromi-1) and KCCM12804P (moromi-2)), which were newly isolated from fermented soy foods, and compared them to those of a commercialized A. oryzae strain (control). Amino-type nitrogen contents of moromi-1 and moromi-2 samples were higher than that of control moromi, and their amylase and protease activities were also higher. Moreover, metabolite profiles of moromi were significantly altered according to strains. In particular, the levels of many amino acids, peptides, nucleotides, and acidic compounds were altered, which resulted in changes in the sensory quality of moromi. Although volatile compounds were not investigated, the results suggested that the quality of moromi was significantly different for newly isolated strains, especially A. oryzae KCCM12804P, and they were superior to the commercial strain in terms of taste-related substances. Therefore, these strains could be used as good starters to produce moromi and soy sauce with good sensory quality. 相似文献
970.
Ji-Hae Joo Min-Hui Han Ja-I Kim Jong-Eun Kim Kyung-Hwan Jung Han Sun Oh Young Soo Chung Hyun Jin An Jae Duk Lee Gi-Seong Moon Hyang-Yeol Lee 《Molecules (Basel, Switzerland)》2022,27(23)
The root of Smilax china L. is used in traditional Korean medicine. We found that the Smilax china L. root extract has strong antimicrobial activity against two Cutibacterium acnes strains (KCTC 3314 and KCTC 3320). The aim of this study was to identify the beneficial properties of Smilax china L. extracts for their potential use as active ingredients in cosmetics for the treatment of human skin acne. The high-performance liquid chromatography (HPLC) and liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry (LC/QTOF/MS) methods were used to obtain the profile of secondary metabolites from the ethyl acetate-soluble fraction of the crude extract. Agar diffusion and resazurin-based broth microdilution assays were used to evaluate antimicrobial activity and minimum inhibitory concentrations (MIC), respectively. Among the 24 metabolites, quercetin, resveratrol, and oxyresveratrol were the most potent compounds against Cutibacterium acnes. Minimum inhibitory concentrations of quercetin, resveratrol, and oxyresveratrol were 31.25, 125, and 250 μg/mL, respectively. 相似文献