全文获取类型
收费全文 | 52748篇 |
免费 | 3952篇 |
国内免费 | 4921篇 |
专业分类
化学 | 34999篇 |
晶体学 | 623篇 |
力学 | 1923篇 |
综合类 | 257篇 |
数学 | 13711篇 |
物理学 | 10108篇 |
出版年
2024年 | 101篇 |
2023年 | 722篇 |
2022年 | 1234篇 |
2021年 | 1176篇 |
2020年 | 1529篇 |
2019年 | 1593篇 |
2018年 | 1392篇 |
2017年 | 1511篇 |
2016年 | 1683篇 |
2015年 | 1657篇 |
2014年 | 2164篇 |
2013年 | 3482篇 |
2012年 | 2560篇 |
2011年 | 3399篇 |
2010年 | 2688篇 |
2009年 | 3445篇 |
2008年 | 3475篇 |
2007年 | 3290篇 |
2006年 | 2797篇 |
2005年 | 2419篇 |
2004年 | 2430篇 |
2003年 | 1943篇 |
2002年 | 2482篇 |
2001年 | 1398篇 |
2000年 | 1214篇 |
1999年 | 1119篇 |
1998年 | 916篇 |
1997年 | 794篇 |
1996年 | 908篇 |
1995年 | 842篇 |
1994年 | 782篇 |
1993年 | 561篇 |
1992年 | 540篇 |
1991年 | 374篇 |
1990年 | 298篇 |
1989年 | 314篇 |
1988年 | 272篇 |
1987年 | 234篇 |
1986年 | 193篇 |
1985年 | 207篇 |
1984年 | 185篇 |
1983年 | 92篇 |
1982年 | 173篇 |
1981年 | 198篇 |
1980年 | 162篇 |
1979年 | 150篇 |
1978年 | 125篇 |
1977年 | 113篇 |
1976年 | 97篇 |
1973年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Modular and quasimodular solutions of a specific second order differential equation in the upper-half plane, which originates from a study of supersingular j-invariants in the first author's work with Don Zagier, are given explicitly. Positivity of Fourier coefficients of some of the solutions as well as a characterization of the differential equation are also discussed. 相似文献
73.
微模塑法制备PMMA/SiO2二氧化硅杂化材料微结构 总被引:1,自引:0,他引:1
以摩尔比为 1∶1的甲基丙烯酸甲酯 (MMA)、甲基丙烯酸 (3 三乙氧基硅烷基 )丙酯 (ESMA)单体、0 .2 %(单体总量的质量分数 )的偶氮二异丁腈AIBN引发剂和四氢呋喃 (THF)溶剂 ,及 2 0 % (总质量分数 )的正硅酸乙酯TEOS合成出PMMA/SiO2 有机 无机杂化的杂化溶胶 .将溶胶在洗净的普通光学玻璃基片表面甩膜 .利用软刻蚀中的微模塑法 ,把有机硅弹性印章复制有精细图纹一面轻放在杂化溶胶膜上进行微模塑 ,外加 1N压力于12 0℃下处理 2h使溶胶凝胶化 .印章剥离后在基片表面就形成了PMMA/SiO2 有机 无机杂化材料的微图纹结构 .从微图纹的光学显微镜照片可以看出微模塑方法制备杂化材料复制的图纹精细度高 ,操作简单易行 ,是一类比较理想的微细图纹结构加工的方法 . 相似文献
74.
75.
Two groups of 10 speech-language pathology graduate students were each given 7 weeks of singing lessons to determine whether voice lessons could have an effect on their clinical and perceptual skills. Pre-, mid-, and posttests to measure various skills were designed and implemented. With use of paired sample statistical testing, statistically significant results were obtained. In addition, the subjective responses of the students show that the lessons were effective in improving pitch perception, breath control, and legato production or easy onset. This study supports efforts to integrate curricula in vocal performance and speech-language pathology. 相似文献
76.
J. Schropp 《Numerische Mathematik》1997,78(1):87-101
Summary. We use the qualitative properties of the solution flow of the gradient equation to compute a local minimum of a real-valued function . Under the regularity assumption of all equilibria we show a convergence result for bounded trajectories of a consistent,
strictly stable linear multistep method applied to the gradient equation. Moreover, we compare the asymptotic features of
the numerical and the exact solutions as done by Humphries, Stuart (1994) and Schropp (1995) for one-step methods. In the
case of -stable formulae this leads to an efficient solver for stiff minimization problems.
Received July 10, 1995 / Revised version received June 27, 1996 相似文献
77.
R. Grac M. Pugnet J.H. Collet B. Lambert C. De Matos H. L'Haridon A. Le Corre J.O. White 《Superlattices and Microstructures》1997,22(4):505-509
We report new results on the diffraction properties of photoinduced gratings in InGaAs/InGaAsP MQW structures. The original feature of this device is that the QWs are enclosed in an asymmetric Fabry–Perot microcavity in order to increase the diffraction efficiency. We observe oscillations in the diffraction efficiency due to resonant effects in the microcavity. The experimental spectra are compared with theory. Diffraction efficiency at 1.55 μm attains a maximum value of 2.7% at a write beam fluence of 260 μ J cm−2, and then decreases at higher fluences. We explain this phenomenon by an absorption saturation at high excitation. 相似文献
78.
The purpose of this paper is to give the Reid ``Roundabout Theorem' for quadratic functionals with general boundary conditions.
In particular, we describe the so-called coupled point and regularity condition introduced in [16] in terms of Riccati equation
solutions.
Accepted 27 February 1996 相似文献
79.
80.