全文获取类型
收费全文 | 7026篇 |
免费 | 680篇 |
国内免费 | 664篇 |
专业分类
化学 | 2967篇 |
晶体学 | 152篇 |
力学 | 740篇 |
综合类 | 93篇 |
数学 | 1936篇 |
物理学 | 2482篇 |
出版年
2024年 | 7篇 |
2023年 | 60篇 |
2022年 | 93篇 |
2021年 | 148篇 |
2020年 | 177篇 |
2019年 | 144篇 |
2018年 | 124篇 |
2017年 | 192篇 |
2016年 | 225篇 |
2015年 | 172篇 |
2014年 | 302篇 |
2013年 | 565篇 |
2012年 | 408篇 |
2011年 | 405篇 |
2010年 | 343篇 |
2009年 | 427篇 |
2008年 | 412篇 |
2007年 | 472篇 |
2006年 | 373篇 |
2005年 | 402篇 |
2004年 | 373篇 |
2003年 | 282篇 |
2002年 | 277篇 |
2001年 | 221篇 |
2000年 | 215篇 |
1999年 | 221篇 |
1998年 | 182篇 |
1997年 | 172篇 |
1996年 | 129篇 |
1995年 | 143篇 |
1994年 | 102篇 |
1993年 | 95篇 |
1992年 | 95篇 |
1991年 | 65篇 |
1990年 | 38篇 |
1989年 | 43篇 |
1988年 | 40篇 |
1987年 | 35篇 |
1986年 | 27篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 19篇 |
1980年 | 9篇 |
1979年 | 27篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1974年 | 5篇 |
排序方式: 共有8370条查询结果,搜索用时 15 毫秒
11.
A.J.?Lpez-Moreno 《Acta Mathematica Hungarica》2005,106(4):343-354
Summary We obtain preservation inequalities for Lipschitz constants of higher order in simultaneous approximation processes by Bernstein type operators. From such inequalities we derive the preservation of the corresponding Lipschitz spaces. 相似文献
12.
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
13.
14.
Omer Ozturk Steven N. MacEachern 《Annals of the Institute of Statistical Mathematics》2004,56(4):701-720
We develop a method of randomizing units to treatments that relies on subjective judgement or on possible coarse modeling
to produce restrictions on the randomization. The procedure thus fits within the general framework of ranked set sampling.
However, instead of selecting a single unit from each set for full measurement, all units within a set are used. The units
within a set are assigned to different treatments. Such an assignment translates the positive dependence among units within
a set into a reduction in variation of contrasting features of the treatments.
A test for treatment versus control comparison, with controlled familywise error rate, is developed along with the associated
confidence intervals. The new procedure is shown to be superior to corresponding procedures based on completely randomized
or ranked set sample designs. The superiority appears both in asymptotic relative efficiency and in power for finite sample
sizes. Importantly, this test does not rely on perfect rankings; rather, the information in the data on the quality of rankings
is exploited to maintain the level of the test when rankings are imperfect. The asymptotic relative efficiency of the test
is not affected by estimation of the quality of rankings, and the finite sample performance is only mildly affected. 相似文献
15.
16.
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
17.
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
18.
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
19.
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
20.