全文获取类型
收费全文 | 8167篇 |
免费 | 1208篇 |
国内免费 | 584篇 |
专业分类
化学 | 2826篇 |
晶体学 | 41篇 |
力学 | 591篇 |
综合类 | 243篇 |
数学 | 2458篇 |
物理学 | 3800篇 |
出版年
2024年 | 34篇 |
2023年 | 175篇 |
2022年 | 514篇 |
2021年 | 392篇 |
2020年 | 269篇 |
2019年 | 217篇 |
2018年 | 189篇 |
2017年 | 315篇 |
2016年 | 386篇 |
2015年 | 292篇 |
2014年 | 502篇 |
2013年 | 637篇 |
2012年 | 499篇 |
2011年 | 506篇 |
2010年 | 463篇 |
2009年 | 520篇 |
2008年 | 496篇 |
2007年 | 510篇 |
2006年 | 416篇 |
2005年 | 345篇 |
2004年 | 290篇 |
2003年 | 267篇 |
2002年 | 265篇 |
2001年 | 198篇 |
2000年 | 208篇 |
1999年 | 165篇 |
1998年 | 155篇 |
1997年 | 123篇 |
1996年 | 124篇 |
1995年 | 71篇 |
1994年 | 83篇 |
1993年 | 76篇 |
1992年 | 40篇 |
1991年 | 35篇 |
1990年 | 35篇 |
1989年 | 20篇 |
1988年 | 21篇 |
1987年 | 12篇 |
1986年 | 22篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 9篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1977年 | 5篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1959年 | 4篇 |
排序方式: 共有9959条查询结果,搜索用时 0 毫秒
71.
72.
通过高频雷达一阶多普勒谱与海上风向的关系, 提出了一种基于神经网络和多波束采样法相结合预测海面风向的新方法. 在神经网络不同输入、输出参数情况下对扩展因子为奇数时的仿真数据进行了风向预测, 并在扩展因子为偶数时结合多波束采样法进行风向预测, 消除了风向的模糊性. 通过预测数据和仿真数据对比, 发现两者符合较好. 从神经网络和多波束采样法相结合的预测结果中可以看出, 风向的误差大约为4°—6°, 风向扩展因子的平均误差为0.26, 为预测海面风场的研究提供一种新的思路和方法. 相似文献
73.
通过对全液体空分装置不同流程组织形式进行分析和模拟计算、能耗与投资的比较,根据不同规格的产品要求,进行合适的流程形式选择,以可达到节能降耗的目的。 相似文献
74.
This study aims at figuring out the crucial topological ingredients which affect the outcomes of the ultimatum game located on different networks,encompassing the regular network,the random network,the small world network,and the scale-free network.With the aid of random interchanging algorithm,we investigate the relations between the outcomes of the ultimatum game and some topological ingredients,including the average range,the clustering coefficient and the heterogeneity,and so forth.It is found that for the regular,random and small-work networks,the average range and the clustering coefficient have evident impacts on the ultimatum game,while for the scale-free network the original degree heterogeneity and the underlying rich-club characterizations are the mainly important topologica ingredients that influence the outcomes of ultimatum game substantially. 相似文献
75.
76.
77.
为了实现快速检测果珍中的二氧化钛含量,提出了应用近红外光谱技术结合化学计量学的快速检测方法。研究采用了320份果珍样本进行光谱特性的检测,其中200个样本用来建模,120个样本进行预测。首先比较了标准正态变量校正(SNV)、变量标准化(Normalize)、多元散射校正(MSC)等6种不同的数据预处理方法对偏最小二乘法(PLS)建模预测效果的影响。然后将PLS模型与应用主成分(PC)建立的主成分-神经网络校正(PC-ANN)模型进行比较。结果表明,MSC预处理的效果最好,PLS模型的最佳主成分数为7,预测值与标准值的相关系数R2达0.900 8,预测标准误差RMSEP为0.05。PC-ANN模型预测值与标准值的R2为0.868 4,RMSEP为0.04。说明PLS模型比PC-ANN模型的预测效果好。同时本研究也说明能够应用可见/近红外技术对二氧化钛进行快速定量测定。 相似文献
78.
Correcting the systematic error of the density functional theory calculation: the alternate combination approach of genetic algorithm and neural network 下载免费PDF全文
The alternate combinational approach of genetic algorithm and neural network (AGANN) has been presented to correct the systematic error of the density functional theory (DFT) calculation.It treats the DFT as a black box and models the error through external statistical information.As a demonstration,the AGANN method has been applied in the correction of the lattice energies from the DFT calculation for 72 metal halides and hydrides.Through the AGANN correction,the mean absolute value of the relative errors of the calculated lattice energies to the experimental values decreases from 4.93% to 1.20% in the testing set.For comparison,the neural network approach reduces the mean value to 2.56%.And for the common combinational approach of genetic algorithm and neural network,the value drops to 2.15%.The multiple linear regression method almost has no correction effect here. 相似文献
79.
Adaptive co-evolution of strategies and network leading to optimal cooperation level in spatial prisoner’s dilemma game 下载免费PDF全文
We study evolutionary prisoner's dilemma game on adaptive
networks where a population of players co-evolves with their
interaction networks. During the co-evolution process, interacted
players with opposite strategies either rewire the link between them
with probability $p$ or update their strategies with probability
$1-p$ depending on their payoffs. Numerical simulation shows that
the final network is either split into some disconnected communities
whose players share the same strategy within each community or forms
a single connected network in which all nodes are in the same
strategy. Interestingly, the density of cooperators in the final
state can be maximised in an intermediate range of $p$ via the
competition between time scale of the network dynamics and that of
the node dynamics. Finally, the mean-field analysis helps to
understand the results of numerical simulation. Our results may
provide some insight into understanding the emergence of cooperation
in the real situation where the individuals' behaviour and their
relationship adaptively co-evolve. 相似文献
80.
Global synchronization of a class of directed dynamical networks with switching topologies is investigated. It is found that if there is a directed spanning tree in the fixed time-average of network topology and the time-average is achieved sufficiently fast, then the network will reach global synchronization for sufficiently large coupling strength. 相似文献