全文获取类型
收费全文 | 10057篇 |
免费 | 1281篇 |
国内免费 | 502篇 |
专业分类
化学 | 783篇 |
晶体学 | 15篇 |
力学 | 1146篇 |
综合类 | 354篇 |
数学 | 6731篇 |
物理学 | 2811篇 |
出版年
2024年 | 14篇 |
2023年 | 99篇 |
2022年 | 229篇 |
2021年 | 260篇 |
2020年 | 219篇 |
2019年 | 232篇 |
2018年 | 254篇 |
2017年 | 388篇 |
2016年 | 493篇 |
2015年 | 316篇 |
2014年 | 607篇 |
2013年 | 678篇 |
2012年 | 530篇 |
2011年 | 610篇 |
2010年 | 485篇 |
2009年 | 656篇 |
2008年 | 672篇 |
2007年 | 689篇 |
2006年 | 555篇 |
2005年 | 528篇 |
2004年 | 431篇 |
2003年 | 379篇 |
2002年 | 353篇 |
2001年 | 305篇 |
2000年 | 273篇 |
1999年 | 243篇 |
1998年 | 208篇 |
1997年 | 181篇 |
1996年 | 152篇 |
1995年 | 127篇 |
1994年 | 89篇 |
1993年 | 106篇 |
1992年 | 85篇 |
1991年 | 52篇 |
1990年 | 52篇 |
1989年 | 35篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 35篇 |
1984年 | 30篇 |
1983年 | 10篇 |
1982年 | 25篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
We consider a coefficient identification problem for a mathematical model with free boundary related to ductal carcinoma in situ (DCIS). This inverse problem aims to determine the nutrient consumption rate from additional measurement data at a boundary point. We first obtain a global‐in‐time uniqueness of our inverse problem. Then based on the optimization method, we present a regularization algorithm to recover the nutrient consumption rate. Finally, our numerical experiment shows the effectiveness of the proposed numerical method. 相似文献
33.
Since the driver pathway in cancer plays a crucial role in the formation and progression of cancer, it is very imperative to identify driver pathways, which will offer important information for precision medicine or personalized medicine. In this paper, an improved maximum weight submatrix problem model is proposed by integrating such three kinds of omics data as somatic mutations, copy number variations, and gene expressions. The model tries to adjust coverage and mutual exclusivity with the average weight of genes in a pathway, and simultaneously considers the correlation among genes, so that the pathway having high coverage but moderate mutual exclusivity can be identified. By introducing a kind of short chromosome code and a greedy based recombination operator, a parthenogenetic algorithm PGA-MWS is presented to solve the model. Experimental comparisons among algorithms GA, MOGA, iMCMC and PGA-MWS were performed on biological and simulated data sets. The experimental results show that, compared with the other three algorithms, the PGA-MWS one based on the improved model can identify the gene sets with high coverage but moderate mutual exclusivity and scales well. Many of the identified gene sets are involved in known signaling pathways, most of the implicated genes are oncogenes or tumor suppressors previously reported in literatures. The experimental results indicate that the proposed approach may become a useful complementary tool for detecting cancer pathways. 相似文献
34.
本文针对求矩阵方程AXB+CXD=F唯一解的参数迭代法,分析当矩阵A,B,C,D均是Hermite正(负)定矩阵时,迭代矩阵的特征值表达式,给出了最优参数的确定方法,并提出了相应的加速算法. 相似文献
35.
36.
Recently Dadush et al. (2017) have devised a polynomial submodular function minimization (SFM) algorithm based on their LP algorithm. In the present note we also show a weakly polynomial algorithm for SFM based on the recently developed linear programming feasibility algorithm of Chubanov (2017) to stimulate further research on SFM. 相似文献
37.
在实际路网情境下结合车道数、车道宽度、路口信号灯设置等路网物理特性,构建了考虑综合交通阻抗的多车型车辆调度模型,提出了两阶段求解策略:第1阶段设计了改进A-star精确解算法用于计算客户时间距离矩阵;第2阶段针对实际路网的特征设计了混合模拟退火算法求解调度方案。以大连市某配送中心运营实例进行路网情境仿真试验,结果表明:改进A-star算法较改进Dijkstra算法具有更短的路径搜索时间;混合模拟退火算法求解结果较实际调度方案优化了13.1% 的综合成本;路网增流、区域拥堵和路段禁行三类路网情境均能对配送方案的车辆配置、路径选择、客户服务次序、作业时间和违约费用等5方面内容产生干扰,调度计划的制定需要详细考虑这些因素的变化。 相似文献
38.
Abdelkader Krifa 《Journal of Difference Equations and Applications》2019,25(1):84-96
In this paper, we prove the possibility of optimization of some free parameters of Meixner-like discrete-time linear filters using orthonormal basis functions (OBF) in an analytical way. Since the z-transform of the Meixner filters is impossible and it is possible for Meixner-like filters, we are motivated to study closely the optimization of the Meixner-like's pole. As a result, the differential equation associated with Meixner-like filters has been developed. On the other hand, the effective width of the energy distribution in the transformation domain is a function of the free parameter (Meixner-like pole) and simple signal measurements and can be calculated by the second-order moment. Analytic minimization of the second-order moment gives an optimal value of the free parameter. To validate the effectiveness of the proposed approach, numerical results are used to determine the free parameters. 相似文献
39.
40.