全文获取类型
收费全文 | 860篇 |
免费 | 185篇 |
国内免费 | 367篇 |
专业分类
化学 | 658篇 |
晶体学 | 48篇 |
力学 | 55篇 |
综合类 | 61篇 |
数学 | 120篇 |
物理学 | 470篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 23篇 |
2020年 | 26篇 |
2019年 | 9篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 27篇 |
2015年 | 44篇 |
2014年 | 42篇 |
2013年 | 61篇 |
2012年 | 57篇 |
2011年 | 68篇 |
2010年 | 79篇 |
2009年 | 93篇 |
2008年 | 91篇 |
2007年 | 67篇 |
2006年 | 102篇 |
2005年 | 88篇 |
2004年 | 58篇 |
2003年 | 58篇 |
2002年 | 61篇 |
2001年 | 50篇 |
2000年 | 56篇 |
1999年 | 30篇 |
1998年 | 17篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 15篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1965年 | 2篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有1412条查询结果,搜索用时 15 毫秒
151.
The authors introduce a new idea related to Montel-type theorems in higher dimension and prove some Montel-type criteria for normal families of holomorphic mappings and normal holomorphic mappings of several complex variables into p^N (C) for continuously moving hyperplanes in pointwise general position. The main results are also true for continuously moving hypersurfaces in pointwise general position. Examples are given to show the sharpness of the results. 相似文献
152.
建立了Fe(Ⅲ)-磺基水杨酸褪色光度法测定硫普罗宁的新方法.结果表明,在酸性介质中,硫普罗宁分子中的巯基(—SH)可将Fe3+还原为Fe2+,采用磺基水杨酸作为Fe3+的显色剂,借褪色分光光度法间接测定了硫普罗宁含量.显色体系最大吸收波长为480nm,硫普罗宁在0.50-4.0μg/mL浓度范围内与AA呈良好的线性关系,线性回归方程为△A=0.0065+ 13C(μg/mL),线性相关系数r=0.9997,检出限为0.00016μg/mL.方法成功用于实际药品中硫普罗宁的含量测定. 相似文献
153.
在实赋范线性空间中利用锥方向高阶广义邻接导数研究带约束的集值优化在超有效解意义下的高阶Mond-Weir对偶问题.在广义锥-凸假设下,利用锥方向高阶广义邻接导数的性质借助凸集分离定理得到了强对偶定理.利用超有效点的标量化定理得到逆对偶定理. 相似文献
154.
针对不同时段内被评价对象增益的不同,提出了一种基于"又好又快发展"思想的动态综合评价方法.首先依据时序立体数据信息,求出被评价对象的增益水平;然后通过均值相对运算、规范化和一致性运算,定义出各被评价对象各指标在某一时刻的相对发展增益权、均衡发展增益权和可持续发展增益权,并进一步计算综合增益权;最后依据激励思想给出增益权与静态综合评价值的合成规则.通过2006-2010年中部六省三次产业"又好又快发展"水平评价的实例分析,证明了方法的科学性. 相似文献
155.
An optical bandpass filter (OBF) is an important element whose properties considerably influence the output performance of a single side band multicarrier source based on a re-circulating frequency shifter. The influence of the OBF in the loop on the output spectrum is theoretically analyzed. Numerical simulations and experiments are Mso carried out. Results show that the steepness and deepness of a nonflat-top filter influence the stability of the spectrum of an output multicarrier. To obtain multicarrier output with tone to noise ratio (TNR) 〉26 dB and error vector magnitude (EVM) 〈0.25, the steepness ratio of the filter should be greater than 0.75 and deepness should be larger than 0.99. 相似文献
156.
A modified transition model is given based on the shear stress transport (SST) turbulence model and an intermittency transport equation. The energy gradient term in the original model is replaced by flow strain rate to saving computational costs. The model employs local variables only, and then it can be conveniently implemented in modern computational fluid dynamics codes. The fifth-order weighted compact nonlinear scheme and the fourth-order staggered scheme are applied to discrete the governing equations for the purpose of minimizing discretization errors, so as to mitigate the confusion between numerical errors and transition model errors. The high-order package is compared with a second-order TVD method on simulating the transitional flow of a flat plate. Numerical results indicate that the high-order package give better grid convergence property than that of the second-order method. Validation of the transition model is performed for transitional flows ranging from low speed to hypersonic speed. 相似文献
157.
158.
对华东师范大学数学系编写的数学分析教材以及陈纪修等编写的数学分析教材课后一道反常积分习题给出反例,并通过增加条件,得到正确结论. 相似文献
159.
160.
Qiu-Chen Peng Dr. Yu-Bing Si Jia-Wang Yuan Qi Yang Zi-Ying Gao Dr. Yuan-Yuan Liu Dr. Zhao-Yang Wang Dr. Kai Li Prof. Shuang-Quan Zang Prof. Ben Zhong Tang 《Angewandte Chemie (International ed. in English)》2023,62(40):e202308194
X-ray imaging technology has achieved important applications in many fields and has attracted extensive attentions. Dynamic X-ray flexible imaging for the real-time observation of the internal structure of complex materials is the most challenging type of X-ray imaging technology, which requires high-performance X-ray scintillators with high X-ray excited luminescence (XEL) efficiency as well as excellent processibility and stability. Here, a macrocyclic bridging ligand with aggregation-induced emission (AIE) feature was introduced for constructing a copper iodide cluster-based metal–organic framework (MOF) scintillator. This strategy endows the scintillator with high XEL efficiency and excellent chemical stability. Moreover, a regular rod-like microcrystal was prepared through the addition of polyvinyl pyrrolidone during the in situ synthesis process, which further enhanced the XEL and processibility of the scintillator. The microcrystal was used for the preparation of a scintillator screen with excellent flexibility and stability, which can be used for high-performance X-ray imaging in extremely humid environments. Furthermore, dynamic X-ray flexible imaging was realized for the first time. The internal structure of flexible objects was observed in real time with an ultrahigh resolution of 20 LP mm−1. 相似文献