全文获取类型
收费全文 | 23880篇 |
免费 | 4058篇 |
国内免费 | 3372篇 |
专业分类
化学 | 16778篇 |
晶体学 | 305篇 |
力学 | 1651篇 |
综合类 | 304篇 |
数学 | 3110篇 |
物理学 | 9162篇 |
出版年
2024年 | 70篇 |
2023年 | 358篇 |
2022年 | 666篇 |
2021年 | 760篇 |
2020年 | 793篇 |
2019年 | 855篇 |
2018年 | 759篇 |
2017年 | 767篇 |
2016年 | 1122篇 |
2015年 | 1159篇 |
2014年 | 1413篇 |
2013年 | 1792篇 |
2012年 | 1952篇 |
2011年 | 2161篇 |
2010年 | 1629篇 |
2009年 | 1632篇 |
2008年 | 1814篇 |
2007年 | 1568篇 |
2006年 | 1571篇 |
2005年 | 1292篇 |
2004年 | 1041篇 |
2003年 | 849篇 |
2002年 | 979篇 |
2001年 | 740篇 |
2000年 | 635篇 |
1999年 | 492篇 |
1998年 | 384篇 |
1997年 | 313篇 |
1996年 | 296篇 |
1995年 | 224篇 |
1994年 | 199篇 |
1993年 | 176篇 |
1992年 | 150篇 |
1991年 | 118篇 |
1990年 | 113篇 |
1989年 | 101篇 |
1988年 | 80篇 |
1987年 | 57篇 |
1986年 | 51篇 |
1985年 | 42篇 |
1984年 | 27篇 |
1983年 | 21篇 |
1982年 | 19篇 |
1981年 | 5篇 |
1980年 | 17篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Guosong Wu Xiaoqin Zeng Wenbin Ding Xingwu Guo Shoushan Yao 《Applied Surface Science》2006,252(20):7422-7429
Ceramic thin films have been widely used to protect the metal substrate as coatings in the past years. In order to improve the poor corrosion resistance of AZ31 magnesium alloy, the study in this paper used the electron beam evaporation method to prepare ceramic PVD films on its surface with TiO2 and Al2O3 as donors, respectively. Atomic force microscopy (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), Auger electron spectroscopy (AES) and X-ray diffraction (XRD) were used to investigate the surface morphology, composition and microstructure of the thin films. Both films deposited on AZ31 took on compact top surface morphologies and grew as amorphous structures on substrate. AES test not only showed that films compositions deviated the standard stoichiometric ratios, but also found that element Mg diffused into films and existed as magnesium oxide in the TiOx film as well as the AlOx film. In the electrochemical corrosion test, the AlOx coating on AZ31 exhibited the largest electrochemical impedance in a 3.5% NaCl solution. But it did not show better corrosion resistance than others for the poorer adhesion. Even if its thickness was small, the TiOx coating on AZ31 exhibited the best corrosion resistance in this study. According to the observation and analysis, the damage of these films on AZ31 in aggressive solutions was mainly due to the existence of pores, microcracks, vacancies and poor adhesion between coating and substrate. 相似文献
62.
63.
基于完全信息博弈理论,阐述了寡头垄断市场的排污收费古诺模型.建立了具有政府宏观调控机制的博弈模型,并对调控效果进行了分析. 相似文献
64.
Generalized KKM Type Theorems in FC-Spaces with Applications (I) 总被引:1,自引:0,他引:1
Xie Ping Ding 《Journal of Global Optimization》2006,36(4):581-596
The class KKM(X,Y) (resp., s-KKM(X,Y,Z)) of set-valued mappings with KKM (resp., s-KKM) property is introduced in FC-spaces without any convexity structure. Some generalized KKM (resp., s-KKM) type theorems are proved in FC-spaces under much weak assumptions. As applications, some new section theorems and coincidence theorems are established in FC-spaces. These theorems generalize many known results in literature. The further applications of these results will be given in a follow-up paper. 相似文献
65.
本文研究了由目标函数扰动的集值优化问题的有效点集所定义的集值映射的半连续性.讨论了目标函数扰动的集值优化问题在上半连续意义下的稳定性.特别地,在广义适定性条件下,证明了集值优化问题在上半连续意义下的稳定性. 相似文献
66.
67.
A family of skew Hadamard difference sets 总被引:1,自引:0,他引:1
Cunsheng Ding 《Journal of Combinatorial Theory, Series A》2006,113(7):1526-1535
In 1933 a family of skew Hadamard difference sets was described by Paley using matrix language and was called the Paley-Hadamard difference sets in the literature. During the last 70 years, no new skew Hadamard difference sets were found. It was conjectured that there are no further examples of skew Hadamard difference sets. This conjecture was proved to be true for the cyclic case in 1954, and further progress in favor of this conjecture was made in the past 50 years. However, the conjecture remains open until today. In this paper, we present a family of new perfect nonlinear (also called planar) functions, and construct a family of skew Hadamard difference sets using these perfect nonlinear functions. We show that some of the skew Hadamard difference sets presented in this paper are inequivalent to the Paley-Hadamard difference sets. These new examples of skew Hadamard difference sets discovered 70 years after the Paley construction disprove the longstanding conjecture on skew Hadamard difference sets. The class of new perfect nonlinear functions has applications in cryptography, coding theory, and combinatorics. 相似文献
68.
一种供应链中的知识管理绩效评价方法研究 总被引:7,自引:0,他引:7
作为知识管理的重要组成部分,知识管理绩效评价旨在帮助企业找出影响绩效提高的关键因素并及时采取有效措施,提高知识管理水平。本文从创造顾客价值、知识的获取能力、知识的共享与传播能力、知识的运用水平、知识的存量水平和知识管理平台等六个方面,分析了评价供应链的知识管理绩效应考虑的主要因素,建立了供应链的知识管理绩效评价指标体系,在此基础上,提出了运用D-S证据推理方法,对供应链知识管理绩效进行评价,并给出了证据推理的算法步骤,最后通过算例分析,说明该方法的有效性、实用性。 相似文献
69.
70.