全文获取类型
收费全文 | 15884篇 |
免费 | 2466篇 |
国内免费 | 1713篇 |
专业分类
化学 | 11651篇 |
晶体学 | 194篇 |
力学 | 843篇 |
综合类 | 74篇 |
数学 | 1545篇 |
物理学 | 5756篇 |
出版年
2024年 | 60篇 |
2023年 | 321篇 |
2022年 | 562篇 |
2021年 | 583篇 |
2020年 | 636篇 |
2019年 | 643篇 |
2018年 | 579篇 |
2017年 | 508篇 |
2016年 | 740篇 |
2015年 | 780篇 |
2014年 | 980篇 |
2013年 | 1209篇 |
2012年 | 1404篇 |
2011年 | 1479篇 |
2010年 | 1064篇 |
2009年 | 909篇 |
2008年 | 1048篇 |
2007年 | 953篇 |
2006年 | 840篇 |
2005年 | 727篇 |
2004年 | 544篇 |
2003年 | 458篇 |
2002年 | 426篇 |
2001年 | 305篇 |
2000年 | 308篇 |
1999年 | 253篇 |
1998年 | 226篇 |
1997年 | 198篇 |
1996年 | 183篇 |
1995年 | 145篇 |
1994年 | 185篇 |
1993年 | 129篇 |
1992年 | 125篇 |
1991年 | 96篇 |
1990年 | 90篇 |
1989年 | 85篇 |
1988年 | 45篇 |
1987年 | 31篇 |
1986年 | 36篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
141.
142.
143.
144.
Nitric oxide (NO) is one of the most important intercellular signaling molecules, and plays important roles in various biological systems. In this work, a unique RuII complex, tris[(5-(4-methylamino-3-aminobenzylamino)-1,10-phenanthroline)] ruthenium(II) hexafluorophosphate [Ru(MAA-phen)3][PF6]2, has been designed and synthesized as a luminescent probe for the detection of NO in aqueous media. The complex itself is almost non-luminescent, but can specifically react with NO under the aerobic conditions to afford its highly luminescent triazole derivative in aqueous media, [Ru(MTA-phen)3]2+ (MTA-phen: methyl-trazolebenzylamino-1,10-phenanthroline), accompanied by a 302-fold increase in luminescence intensity at 598 nm with a 130 nm Stokes shift. The luminescence response of [Ru(MAA-phen)3]2+ to NO is rapid, highly specific without interferences of other reactive oxygen/nitrogen species, and highly stable against the pH changes in the range of pH 4.5–9.5. These features enable [Ru(MAA-phen)3]2+ to be used as a probe for the highly selective and sensitive luminescence detection of NO in weakly acidic, neutral, and weakly basic media. 相似文献
145.
Jie Song Eunji Lee Byoung‐Ki Cho 《Journal of polymer science. Part A, Polymer chemistry》2013,51(2):446-456
A well‐defined (PEO‐PS)2‐PLA miktoarm terpolymer ( 1 ) was synthesized by stepwise click reactions of individually prepared poly(ethylene oxide) (PEO), polystyrene (PS, polymerized by atom transfer radical polymerization), and polylactide (PLA, polymerized by ring‐opening polymerization) blocks. As characterized by differential scanning calorimetry and small‐angle X‐ray scattering techniques, the terpolymer self‐assembled into a hexagonal columnar structure consisting of PLA/PEO cylindrical cores surrounded by PS chains. In contrast, the ion‐doped sample ( 1‐Li+ ) with lithium concentration per ethylene oxide = 0.2 exhibited a three‐phase lamellar structure, which was attributed to the microphase separation between PEO and PLA blocks and to the conformational stabilization of the longest PLA chain. The two‐phase columnar morphology before the ion doping was used to prepare a nanoporous material. PLA chains in the cylindrical core region were hydrolyzed by sodium hydroxide, producing nanopores with a pore diameter of about 14 nm. The resulted nanoporous material sank to the bottom in water, because of water‐compatible PEO chains on the walls. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
146.
Laser-induced breakdown spectroscopy(LIBS) is used to determine the total nitrogen(TN) and total phosphorus(TP) in soil.Quantitative determinations are conducted using the line intensity of the analyte element and element concentration.Calibration models are obtained using ten samples for TN and seven samples for TP.The rest samples are used to validate the results.Strong linear correlations are obtained from the determined TN and TP concentrations.LIBS is a powerful tool for analyzing soil samples to determine nutrient elements by selecting calibration and validation samples with similar matrix composition. 相似文献
147.
In this letter, we discuss the increase in the average cluster size by lowering the stagnation temperature of the methane (CH4) gas. The Coulomb explosion experiments are conducted to estimate the cluster size and the size distribution. The average CH4 cluster sizes Nay of 6 230 and 6 580 are acquired with the source conditions of 30 bars at 240 K and 60 bars at 296 K, respectively. Empirical estimation suggests a five-fold increase in the average size of the CH4 clusters at 240 K compared with that at room temperature under a backing pressure of 30 bars. A strong nonlinear Hagena parameter relation (Г^*∝ T0^-3.3) for the CH4 clusters is revealed. The results may be favorable for the production of large-sized clusters by using gases at low temperature and high back pressures. 相似文献
148.
基于改进的Newman和Ziff算法以及有限尺寸标度理论, 通过对表征渗流相变特征物理量的序参量、平均集团尺寸、二阶矩、标准偏差及尺寸不均匀性的数值模拟, 分析研究了Erdös Rényi随机网络上Achlioptas爆炸渗流模型的相变性质.研究表明: 尽管序参量表现出了不连续相变的特征, 但序参量以及其他特征物理量仍具有连续相变的幂律标度行为.因此严格地说, Erdös Rényi随机网络中的爆炸渗流相变是一种奇异相变, 它既不是标准的不连续相变, 又与常规随机渗流表现出的连续相变处于不同的普适类.
关键词:
Erdös Rényi随机网络
爆炸渗流模型
相变
幂律标度行为 相似文献
149.
基于k·p微扰法计算了单轴〈111〉应力作用下硅的价带结构, 并与未受应力时体硅的价带结构进行了比较. 给出了单轴〈111〉应力作用下硅价带顶处能级的移动、分裂以及空穴有效质量的变化情况. 计算所得未受应力作用时硅价带顶处重空穴带、轻空穴带有效质量与相关文献报道体硅有效质量结果一致. 拓展了单轴应力硅器件导电沟道应力与晶向的选择范围,给出的硅价带顶处重空穴带、轻空穴带能级间的分裂值和有效质量随应力的变化关系可为单轴〈111〉应力硅其他物理参数的计算提供参考.
关键词:
单轴应力硅
k·p法')" href="#">k·p法
价带结构 相似文献
150.
开展了波长为532 nm、脉宽为8 ns的纳秒激光诱导空气等离子体射频电磁辐射特性实验研究,基于锥形天线探测空气等离子体在30-800 MHz频谱范围有较强的射频电磁辐射,是等离子体内电偶极子振荡变速运动造成的.实验结果表明:随激光能量增加,30-200 MHz范围内射频辐射强度逐渐变强,但360-600 MHz频率范围射频辐射强度逐渐变弱.等离子体射频辐射的空间分布依赖于入射激光的偏振方向,当激光偏振方向与天线放置方向一致时,该方向上空气等离子体的射频辐射强度高,谱线较丰富.射频辐射总功率随激光能量先增加后降低,采用等离子体电子密度变化对等离子体频率及等离子体衰减系数影响(制约)关系,对射频辐射总功率随激光能量的变化规律进行了解释. 相似文献