全文获取类型
收费全文 | 20578篇 |
免费 | 3675篇 |
国内免费 | 3317篇 |
专业分类
化学 | 15788篇 |
晶体学 | 340篇 |
力学 | 1312篇 |
综合类 | 209篇 |
数学 | 2281篇 |
物理学 | 7640篇 |
出版年
2024年 | 57篇 |
2023年 | 441篇 |
2022年 | 723篇 |
2021年 | 819篇 |
2020年 | 889篇 |
2019年 | 940篇 |
2018年 | 794篇 |
2017年 | 795篇 |
2016年 | 1028篇 |
2015年 | 1040篇 |
2014年 | 1206篇 |
2013年 | 1584篇 |
2012年 | 1761篇 |
2011年 | 1871篇 |
2010年 | 1414篇 |
2009年 | 1303篇 |
2008年 | 1414篇 |
2007年 | 1146篇 |
2006年 | 1193篇 |
2005年 | 1001篇 |
2004年 | 846篇 |
2003年 | 701篇 |
2002年 | 713篇 |
2001年 | 645篇 |
2000年 | 495篇 |
1999年 | 429篇 |
1998年 | 334篇 |
1997年 | 270篇 |
1996年 | 290篇 |
1995年 | 221篇 |
1994年 | 212篇 |
1993年 | 197篇 |
1992年 | 150篇 |
1991年 | 139篇 |
1990年 | 115篇 |
1989年 | 92篇 |
1988年 | 66篇 |
1987年 | 50篇 |
1986年 | 55篇 |
1985年 | 38篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 16篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1971年 | 1篇 |
1959年 | 3篇 |
1957年 | 3篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
利用傅里叶变温红外光谱仪分别测定了三羟甲基甲胺(TAM)、季戊四醇(PE)及其二元体系变温红外谱。实验表明,多元醇分子中羟基吸收峰随温度升高耐发生位移向高波数移动,此结果既能反映多元醇及其二体系固-固相变的温度区间,又与转变热相对应,从而揭示了多元醇及其二元体系固-固相变贮热的机理。 相似文献
92.
We measured the time decay of the magnetic moment of high Tc superconductors YBa2Cu3O7-δ ceramic samples and found the memory effect which has hitherto been reported only in single crystals. The temperature and field ranges, especially the memory phenomenon in ceramic samples at liquid nitrogen temperature can only be understood in a combined picture of both flux creep and glass behaviour 相似文献
93.
94.
The grain boundary is an interface and the surface tension is one of its important thermodynamic properties. In this paper,
the surface tension of the ∑9 grain boundary for α-Fe at various temperatures and pressures is calculated by means of Computer
Molecular Dynamics (CMD). The results agree satisfactorily with the experimental data. It is shown that the contribution of
entropy to surface tension of grain boundary can be ignored.
The project supported by the National Natural Science Foundation of China and the Science Foundation of Chinese Academy of
Sciences. 相似文献
95.
两步相移实现投影栅相位测量轮廓术 总被引:9,自引:2,他引:7
提出一种新的投影栅相位测量方法--两步相移法。该方法只需两幅相移条纹图,因此计算量小,速度快。给出了实验及计算结果,并同四步相移法进行了比较,证明了该方法具有较高的精度。 相似文献
96.
97.
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
98.
We analyze an infinite horizon, single product, continuous review model in which pricing and inventory decisions are made simultaneously and ordering cost includes a fixed cost. We show that there exists a stationary (s,S) inventory policy maximizing the expected discounted or expected average profit under general conditions. 相似文献
99.
100.
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