全文获取类型
收费全文 | 17610篇 |
免费 | 2326篇 |
国内免费 | 1442篇 |
专业分类
化学 | 7969篇 |
晶体学 | 94篇 |
力学 | 733篇 |
综合类 | 104篇 |
数学 | 1315篇 |
物理学 | 4839篇 |
综合类 | 6324篇 |
出版年
2024年 | 72篇 |
2023年 | 332篇 |
2022年 | 536篇 |
2021年 | 587篇 |
2020年 | 535篇 |
2019年 | 499篇 |
2018年 | 439篇 |
2017年 | 466篇 |
2016年 | 653篇 |
2015年 | 738篇 |
2014年 | 808篇 |
2013年 | 1051篇 |
2012年 | 1204篇 |
2011年 | 1311篇 |
2010年 | 875篇 |
2009年 | 970篇 |
2008年 | 1004篇 |
2007年 | 936篇 |
2006年 | 804篇 |
2005年 | 764篇 |
2004年 | 547篇 |
2003年 | 474篇 |
2002年 | 432篇 |
2001年 | 411篇 |
2000年 | 393篇 |
1999年 | 560篇 |
1998年 | 569篇 |
1997年 | 535篇 |
1996年 | 447篇 |
1995年 | 455篇 |
1994年 | 370篇 |
1993年 | 305篇 |
1992年 | 255篇 |
1991年 | 234篇 |
1990年 | 214篇 |
1989年 | 176篇 |
1988年 | 130篇 |
1987年 | 98篇 |
1986年 | 58篇 |
1985年 | 35篇 |
1984年 | 21篇 |
1983年 | 23篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
42.
混合氯化稀土催化合成DOP,DOM和DOA 总被引:1,自引:0,他引:1
本文报道:价廉的混合氯化稀土,对合成DOP等增塑剂有明显的催化效果。产品精制简单,转化率高,有应用前景。 相似文献
43.
The dendrite growth process of transparent NaBi(WO4)2 with small prandtl and high melting point was studied by using the in-situ observation system. According to the dynamic images and detailed information, there are two kinds of restriction effect on
the dendrite growth, the competition between arms and branches and the convection in the melt. The dendrite growth rate was
time dependent, and the rate of arm growth reached the maximum 5.8 mm/s in the diffusive-advective region and rapidly decreased
in the diffusive-convective region. The growth rate of branch had the same change trends as the arm’s. Based on the EPMA-EDS
data of solidification structure of quenched NaBi(WO4)2 melt, it was found that there were component differences from stoichiometric concentration in the melt near the interface
during the growth process.
Supported by the National Natural Science Foundation of China (Grant No. 50331040) and the Innovation Funds from Shanghai
Institute of Ceramics, Chinese Academy of Sciences (Grant No. SCX0623) 相似文献
44.
Zhengqian Luo Guoyong Sun Zhiping Cai Miaoling Si Qibo Li 《Optics Communications》2007,277(1):118-124
In this paper, continuous wave Yb3+-doped double-clad fiber lasers (DCFLs) with linear-cavity are investigated theoretically and numerically using the rate equations. Under the steady state conditions, the simplified analytic solutions of Yb3+-doped DCFLs under considering the scattering loss are deduced in the strongly pump condition. Compared with the known analytic solutions in published literatures, our analytic solutions are more accurate, especially, at higher reflectivity of output mirror. In addition, a fast and stable algorithm based on the Newton-Raphson method is proposed to simulate numerically Yb3+-doped DCFLs. The results by simplified analytic solutions are in good agreement with those by the numerical simulation. Moreover, we have performed the optimization of an Yb3+-doped DCFL using the simplified analytic solutions and the numerical simulations, respectively. 相似文献
45.
A mistake concerning the ultra LI-ideal of a lattice implication algebra is pointed out, and some new sufficient and necessary conditions for an LI-ideal to be an ultra LI-ideal are given. Moreover, the notion of an LI-ideal is extended to MTL-algebras, the notions of a (prime, ultra, obstinate, Boolean) LI-ideal and an ILI-ideal of an MTL-algebra are introduced, some important examples are given, and the following notions are proved to be equivalent in MTL-algebra: (1) prime proper LI-ideal and Boolean LI-ideal, (2) prime proper LI-ideal and ILI-ideal, (3) proper obstinate LI-ideal, (4) ultra LI-ideal.
This work was supported by the Zhejiang Provincial Natural Science Foundation of China (Grant No. Y605389) and K. C. Wong
Magna Fund in Ningbo University. 相似文献
46.
A route to the total synthesis of koumine has been suggested. Five 4-substituted 1, 2-d hydropyridine derivatives, which are supposed to be a conjugated diene of Diels-Alder reaction to produce the isoquinuclidine ring of koumine, have been synthesized. Only two of them were found to be able to undergo the Diels-Alder reaction. The stereochemistry of the reaction product has also been examined. 相似文献
47.
本文简述了乳浓聚合动力学研究的进展,着重于澳大利亚Sydney大学Gilbert等在乳液聚合阶段Ⅱ动力学方面的研究概况。介绍了不同水溶性单体的小尺寸种子乳液体系的SmithEwart递推方程的求解方法及其解析解形式和乳液聚合动力学数据的处理。同时讨论了该研究的局限性。 相似文献
48.
50.