全文获取类型
收费全文 | 18967篇 |
免费 | 2406篇 |
国内免费 | 3478篇 |
专业分类
化学 | 13976篇 |
晶体学 | 309篇 |
力学 | 839篇 |
综合类 | 313篇 |
数学 | 2519篇 |
物理学 | 6895篇 |
出版年
2023年 | 181篇 |
2022年 | 412篇 |
2021年 | 457篇 |
2020年 | 494篇 |
2019年 | 499篇 |
2018年 | 435篇 |
2017年 | 518篇 |
2016年 | 583篇 |
2015年 | 697篇 |
2014年 | 791篇 |
2013年 | 1199篇 |
2012年 | 1382篇 |
2011年 | 1541篇 |
2010年 | 1150篇 |
2009年 | 1267篇 |
2008年 | 1450篇 |
2007年 | 1330篇 |
2006年 | 1212篇 |
2005年 | 1127篇 |
2004年 | 980篇 |
2003年 | 812篇 |
2002年 | 778篇 |
2001年 | 744篇 |
2000年 | 774篇 |
1999年 | 448篇 |
1998年 | 321篇 |
1997年 | 275篇 |
1996年 | 268篇 |
1995年 | 239篇 |
1994年 | 238篇 |
1993年 | 216篇 |
1992年 | 204篇 |
1991年 | 154篇 |
1990年 | 179篇 |
1989年 | 138篇 |
1988年 | 150篇 |
1987年 | 123篇 |
1986年 | 113篇 |
1985年 | 110篇 |
1984年 | 96篇 |
1983年 | 96篇 |
1982年 | 83篇 |
1981年 | 72篇 |
1980年 | 63篇 |
1979年 | 43篇 |
1978年 | 41篇 |
1977年 | 39篇 |
1976年 | 40篇 |
1974年 | 51篇 |
1973年 | 44篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
该文讨论了一类非线性抛物型方程组解的性质,利用微分方程上、下解方法证明了初值适当小时,方程存在整体解;初值适当大时,解在有限时间上爆破,推广了文献[1]的结果. 相似文献
32.
33.
YunXiaWANG LinJIA ZhenSHI 《中国化学快报》2003,14(6):561-564
The addition-hydrolysis reaction of benzimidazolium salt with some mono- and bifunctional amine nucleophiles is reported,and a novel method of biomimetic synthesis for formamides and heterocycle compounds is provided. 相似文献
34.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and
first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
35.
制作了掺杂rubrene和4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9,enyl)-4H-pyran(DCJTB)两种荧光染料的红光有机电致发光器件。N,N’-diphenyl-N,N’-bis(1-naphthyl)-(1,1’-biphenyl)-4,4’-diamine(NPB)和掺杂的Tri-(8-hydroxyquinoline)aluminum(Alq3)分别作为空穴和电子传输层。我们发现掺rubrene和DCJTB的器件性能与只掺DCJTB的器件性能相比有所提高。器件性能的改善是因为掺入的rubrene能够促进从Alq3到DCJTB的能量转移。根据荧光衰减曲线,计算出从Alq3到DCJTB、从Alq3到rubrene以及从rubrene到DCJTB的能量转移速率分别为1.04×109,3.89×109,2.79×109s-1。可以看出能量通过rubrene从Alq3到DCJTB的转移速率是能量直接从Alq3到DCJTB的2.7倍。 相似文献
36.
37.
The glow curve structures for LiF:Mg,Cu,Na,Si TL detectors with various dopant concentrations and sintering temperatures were investigated for the improvement of the glow curve structure and sensitivity of the TL detector. The dopant concentrations were varied over the following ranges: Mg (0–0.25 mol%), Cu (0–0.07 mol%), Na and Si (0–1.5 mol%). With increasing Cu concentration, the intensity of the main peak was intensified and reached a maximum at a concentration of 0.05 mol%. The high-temperature peak was reduced. The dependency of the main peak intensity on the Mg concentration exhibits a sharp maximum at 0.2 mol%. The intensity of the high-temperature peak tends to rise slightly with increasing Mg concentration. It was found that the optimum concentrations of the dopants in the LiF:Mg,Cu,Na,Si TL material are Mg: 0.2 mol%, Cu: 0.05 mol%, Na and Si: 0.9 mol%. The dependency of the main peak intensity on sintering temperature exhibits a very sharp maximum at 830°C. The high-temperature peak was rapidly reduced after 825°C. 相似文献
38.
39.
Jem‐Kun Chen I‐Kuan Lin Fu‐Hsiang Ko Chih‐Feng Huang Kuo‐Shen Chen Chia‐Hao Chan Feng‐Chih Chang 《Journal of Polymer Science.Polymer Physics》2004,42(22):4063-4074
Polybenzoxazine (PBZZ) thin films can be fabricated by the plasma‐polymerization technique with, as the energy source, plasmas of argon, oxygen, or hydrogen atoms and ions. When benzoxazine (BZZ) films are polymerized through the use of high‐energy argon atoms, electronegative oxygen atoms, or excited hydrogen atoms, the PBZZ films that form possess different properties and morphologies in their surfaces. High‐energy argon atoms provide a thermodynamic factor to initiate the ring‐opening polymerization of BZZ and result in the polymer surface having a grid‐like structure. The ring‐opening polymerization of the BZZ film that is initiated by cationic species such as oxygen atoms in plasma, is propagated around nodule structures to form the PBZZ. The excited hydrogen atom plasma initiates both polymerization and decomposition reactions simultaneously in the BZZ film and results in the formation of a porous structure on the PBZZ surface. We evaluated the surface energies of the PBZZ films polymerized by the action of these three plasmas by measuring the contact angles of diiodomethane and water droplets. The surface roughness of the films range from 0.5 to 26 nm, depending on the type of carrier gas and the plasma‐polymerization time. By estimating changes in thickness, we found that the PBZZ film synthesized by the oxygen plasma‐polymerization process undergoes the slowest rate of etching in CF4 plasma. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4063–4074, 2004 相似文献
40.
Jue Lu Chang K. Hong Richard P. Wool 《Journal of Polymer Science.Polymer Physics》2004,42(8):1441-1450
Some discovery work was done on the synthesis of clay nanocomposites based on renewable plant oils. Functionalized triglycerides, such as acrylated epoxidized soybean oil, maleinized acrylated epoxidized soybean oil, and soybean oil pentaerythritol maleates, combined with styrene were used as the polymer matrix. The miscibility of these monomers and clay organomodifier was assessed by solubility parameters. The formation of nanocomposites was confirmed by both X‐ray data and transmission electron microscopy. The morphology showed a mix of intercalated and partially exfoliated sheets. The flexural modulus increased 30% at only 4 vol % clay content, but there was no significant effect on flexural strength, glass‐transition temperature, and thermal stability. Property enhancement was related to the degree of exfoliation that depends on both the polarity and flexibility of the monomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1441–1450, 2004 相似文献