全文获取类型
收费全文 | 4484篇 |
免费 | 482篇 |
国内免费 | 504篇 |
专业分类
化学 | 1701篇 |
晶体学 | 149篇 |
力学 | 640篇 |
综合类 | 55篇 |
数学 | 917篇 |
物理学 | 2008篇 |
出版年
2024年 | 8篇 |
2023年 | 33篇 |
2022年 | 64篇 |
2021年 | 77篇 |
2020年 | 91篇 |
2019年 | 76篇 |
2018年 | 75篇 |
2017年 | 97篇 |
2016年 | 128篇 |
2015年 | 99篇 |
2014年 | 211篇 |
2013年 | 302篇 |
2012年 | 241篇 |
2011年 | 264篇 |
2010年 | 238篇 |
2009年 | 302篇 |
2008年 | 309篇 |
2007年 | 319篇 |
2006年 | 248篇 |
2005年 | 303篇 |
2004年 | 275篇 |
2003年 | 193篇 |
2002年 | 192篇 |
2001年 | 152篇 |
2000年 | 138篇 |
1999年 | 137篇 |
1998年 | 126篇 |
1997年 | 117篇 |
1996年 | 82篇 |
1995年 | 80篇 |
1994年 | 66篇 |
1993年 | 63篇 |
1992年 | 75篇 |
1991年 | 38篇 |
1990年 | 30篇 |
1989年 | 32篇 |
1988年 | 30篇 |
1987年 | 27篇 |
1986年 | 22篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 14篇 |
1980年 | 4篇 |
1979年 | 20篇 |
1978年 | 12篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1973年 | 2篇 |
排序方式: 共有5470条查询结果,搜索用时 31 毫秒
1.
We numerically solve the time-dependent Ginzburg–Landau equations for two-gap superconductors using the finite-element technique. The real-time simulation shows that at low magnetic field, the vortices in small-size samples tend to form clusters or other disorder structures. When the sample size is large, stripes appear in the pattern. These results are in good agreement with the previous experimental observations of the intriguing anomalous vortex pattern, providing a reliable theoretical basis for the future applications of multi-gap superconductors. 相似文献
2.
Mariusz Marć Marek Tobiszewski Bożena Zabiegała Miguel de la Guardia Jacek Namieśnik 《Analytica chimica acta》2015
This review summarizes the different tools and concepts that are commonly applied in air quality monitoring. The monitoring of atmosphere is extremely important as the air quality is an important problem for large communities. Main requirements for analytical devices used for monitoring include a long period of autonomic operation and portability. These instruments, however, are often characterized by poor analytical performance. Monitoring networks are the most common tools used for monitoring, so large-scale monitoring programmes are summarized here. Biomonitoring, as a cheap and convenient alternative to traditional sample collection, is becoming more and more popular, although its main drawback is the lack of standard procedures. Telemonitoring is another approach to air monitoring, which offers some interesting opportunities, such as ease of coverage of large or remote areas, constituting a complementary approach to traditional strategies; however, it requires huge costs. 相似文献
3.
4.
We obtain expressions for the energy spectrum widths of Rayleigh waves corresponding to their deformational coupling to Fermi and Boltzmann electrons in a two-dimensional layer near the surface of a semibounded solid. We evaluate the nonequilibrium energy of Rayleigh waves that depends on these widths and is caused by the same coupling to the corresponding hot electrons. We show that this energy is independent of the degeneracy degree of the electrons and is given by the mean energy of free Rayleigh waves heated up to temperature of the electrons. We find conditions under which the thermodynamics is determined by this nonequilibrium energy of Rayleigh waves in films of a certain thickness with Fermi electrons near the surface and by the equilibrium energy of bulk phonons in thicker samples. All the results are obtained using the Keldysh diagram technique applied to the case of semibounded media. 相似文献
5.
6.
R. Bairava Ganesh Hitoshi Matsuo Takahiro Kawamura Yoshihiro Kangawa Koji Arafune Yoshio Ohshita Masafumi Yamaguchi Koichi Kakimoto 《Journal of Crystal Growth》2008,310(11):2697-2701
Multicrystalline silicon was grown by unidirectional solidification method using the accelerated crucible rotation technique. The application of the accelerated crucible rotation technique in unidirectional solidification method induced growth striations across the axial direction of the grown crystal. This striation pattern was observed from carbon concentration distribution, obtained by using Fourier transform infrared spectroscopy. The generated striation pattern was found to be weak and discontinuous. Some striations were absent, probably due to back melting, caused during each crucible rotation. From the growth striations and applied time period in crucible rotation, the growth rate was estimated by using Fourier transformation analysis. 相似文献
7.
CONG Fuzhong & LI YongSchool of Mathematics Information Science Shandong Institute of Business Technology Yantai China Office of Mathematics Changchun Flight Academy of the Air Force Changchun China Department of Mathematics Jilin University Changchun China 《中国科学A辑(英文版)》2004,47(5):675-686
An effective stability result for generalized Hamiltonian systems is obtained by applying the simultaneous approximation technique due to Lochak. Among these systems, dimensions of action variables and angle variables might be distinct. 相似文献
8.
本文提供了预条件不精确牛顿型方法结合非单调技术解光滑的非线性方程组.在合理的条件下证明了算法的整体收敛性.进一步,基于预条件收敛的性质,获得了算法的局部收敛速率,并指出如何选择势序列保证预条件不精确牛顿型的算法局部超线性收敛速率. 相似文献
9.
近年来,决定椭圆型方程系数反问题在地磁、地球物理、冶金和生物等实际问题上有着广泛的应用.本文讨论了二维的决定椭圆型方程系数反问题的数值求解方法.由误差平方和最小原则,这个反问题可化为一个变分问题,并进一步离散化为一个最优化问题,其目标函数依赖于要决定的方程系数.本文着重考察非线性共轭梯度法在此最优化问题数值计算中的表现,并与拟牛顿法作为对比.为了提高算法的效率我们适当选择加快收敛速度的预处理矩阵.同时还考察了线搜索方法的不同对优化算法的影响.数值实验的结果表明,非线性共轭梯度法在这类大规模优化问题中相对于拟牛顿法更有效. 相似文献
10.