首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9225篇
  免费   1683篇
  国内免费   1011篇
化学   6186篇
晶体学   90篇
力学   810篇
综合类   77篇
数学   1257篇
物理学   3499篇
  2024年   17篇
  2023年   195篇
  2022年   219篇
  2021年   317篇
  2020年   372篇
  2019年   351篇
  2018年   308篇
  2017年   291篇
  2016年   438篇
  2015年   435篇
  2014年   477篇
  2013年   655篇
  2012年   779篇
  2011年   869篇
  2010年   587篇
  2009年   568篇
  2008年   643篇
  2007年   503篇
  2006年   551篇
  2005年   402篇
  2004年   336篇
  2003年   269篇
  2002年   245篇
  2001年   206篇
  2000年   202篇
  1999年   204篇
  1998年   190篇
  1997年   190篇
  1996年   185篇
  1995年   150篇
  1994年   121篇
  1993年   113篇
  1992年   95篇
  1991年   76篇
  1990年   78篇
  1989年   67篇
  1988年   46篇
  1987年   38篇
  1986年   36篇
  1985年   26篇
  1984年   19篇
  1983年   15篇
  1982年   17篇
  1981年   4篇
  1980年   7篇
  1979年   2篇
  1975年   1篇
  1971年   1篇
  1959年   1篇
  1957年   2篇
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
1.
Journal of Radioanalytical and Nuclear Chemistry - This study presents a time-efficient method of analysing 210Pb, 210Bi, and 210Po in natural waters. The optimum pH (1.00), temperature...  相似文献   
2.
We consider concentrated vorticities for the Euler equation on a smooth domain Ω?R2 in the form of
ω=j=1NωjχΩj,|Ωj|=πrj2,Ωjωjdμ=μj0,
supported on well-separated vortical domains Ωj, j=1,,N, of small diameters O(rj). A conformal mapping framework is set up to study this free boundary problem with Ωj being part of unknowns. For any given vorticities μ1,,μN and small r1,,rNR+, through a perturbation approach, we obtain such piecewise constant steady vortex patches as well as piecewise smooth Lipschitz steady vorticities, both concentrated near non-degenerate critical configurations of the Kirchhoff–Routh Hamiltonian function. When vortex patch evolution is considered as the boundary dynamics of ?Ωj, through an invariant subspace decomposition, it is also proved that the spectral/linear stability of such steady vortex patches is largely determined by that of the 2N-dimensional linearized point vortex dynamics, while the motion is highly oscillatory in the 2N-codim directions corresponding to the vortical domain shapes.  相似文献   
3.
4.
张晶  潘亚妮  刘丁  牟伟明 《人工晶体学报》2018,47(12):2429-2435
在直拉法制备硅单晶的过程中,要得到优质的晶体必须建立合理的温度分布,而单晶炉内热场的分布与工艺参数的设定密切相关.其中以晶体转速、坩埚转速和拉速等三个工艺参数对热场分布的影响尤为显著.为了确定最佳热场分布下晶转、埚转及拉速的设定值,本文采用响应面算法通过方程拟合、回归分析等步骤求解这三个工艺参量与温度梯度之间的最佳函数模型,并在该模型下同时对这三个工艺参量进行优化分析,且通过仿真实验和拉晶实验表明该方法的有效性.  相似文献   
5.
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme.  相似文献   
6.
Ding  Hao  Wang  Jin-Ting  Lu  Li-Qiao  Pan  Jian-Wen 《Nonlinear dynamics》2021,104(4):3365-3384
Nonlinear Dynamics - Conventional tuned liquid column dampers (TLCDs) are deficient in multidirectionality. In contrast, toroidal TLCDs are designed to extend the application to multidirectional...  相似文献   
7.
8.
Ding  Q.  Yao  M.  Wu  Sh.  Zeng  M.  Xue  N.  Wu  D.  Xu  J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the...  相似文献   
9.
10.
The discharge of diverse pollutants has led to a complex water environment and posed a huge health threat to humans and animals. Self-propelled micromotors have recently attracted considerable attention for efficient water remediation due to their strong localized mass transfer effect. However, a single functionalized component is difficult to tackle with multiple contaminants and requires to combine different decontamination effects together. Here, we introduced a multifunctional micromotor to implement the adsorption and degradation roles simultaneously by integrating the poly(aspartic acid) (PASP) adsorbent with a MnO2-based catalyst. The as-prepared micromotors are well propelled in contaminated waters by MnO2 catalyzing hydrogen peroxide. In addition, the catalytic ramsdellite MnO2(R-MnO2) inner layer is decorated with Fe2O3 nanoparticles to improve their catalytic performance, contributing to an excellent degradation ability with 90% tetracycline (TC) removal in 50 minutes by enhanced Fenton-like reactions. Combining the attractive adsorption capability of poly (aspartic acid) (PASP), the composite micromotors offer an efficient removal of heavy metal ions in short time. Moreover, the designed micromotors are able to simultaneously remove antibiotic and heavy metals in mixed contaminants circumstance just in single treatment. This multifunctional micromotor with distinctive decontamination ability exhibits a promising prospective in treating multiple pollutants in the future.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号