全文获取类型
收费全文 | 105890篇 |
免费 | 850篇 |
国内免费 | 948篇 |
专业分类
化学 | 73729篇 |
晶体学 | 32篇 |
力学 | 792篇 |
综合类 | 284篇 |
数学 | 1062篇 |
物理学 | 31789篇 |
出版年
2023年 | 93篇 |
2022年 | 115篇 |
2021年 | 102篇 |
2020年 | 83篇 |
2019年 | 76篇 |
2018年 | 121篇 |
2017年 | 70篇 |
2016年 | 155篇 |
2015年 | 129篇 |
2014年 | 294篇 |
2013年 | 218篇 |
2012年 | 9182篇 |
2011年 | 12790篇 |
2010年 | 2228篇 |
2009年 | 525篇 |
2008年 | 9984篇 |
2007年 | 10161篇 |
2006年 | 10363篇 |
2005年 | 9879篇 |
2004年 | 7804篇 |
2003年 | 5810篇 |
2002年 | 5218篇 |
2001年 | 3272篇 |
2000年 | 4062篇 |
1999年 | 975篇 |
1998年 | 354篇 |
1997年 | 329篇 |
1996年 | 1715篇 |
1995年 | 1126篇 |
1994年 | 1488篇 |
1993年 | 1984篇 |
1992年 | 1731篇 |
1991年 | 741篇 |
1990年 | 699篇 |
1989年 | 623篇 |
1988年 | 519篇 |
1987年 | 467篇 |
1986年 | 566篇 |
1985年 | 503篇 |
1984年 | 86篇 |
1983年 | 67篇 |
1982年 | 61篇 |
1981年 | 52篇 |
1979年 | 51篇 |
1977年 | 47篇 |
1976年 | 65篇 |
1975年 | 76篇 |
1974年 | 52篇 |
1973年 | 43篇 |
1948年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Some hydrodynamic aspects of 3-phase inverse fluidized bed 总被引:2,自引:0,他引:2
Krishna S.V.S.R. Bandaru D.V.S. Murthy K. Krishnaiah 《中国颗粒学报》2007,5(5):351-356
Hydrodynamics of 3-phase inverse fluidized bed is studied experimentally using low density particles for different liquid and gas velocities. The hydrodynamic characteristics studied include pressure drop, minimum liquid and gas fluidization velocities and phase holdups. The minimum liquid fluidization velocity determined using the bed pressure gradient, decreases with increase in gas velocity. The axial profiles of phase holdups shows that the liquid holdup increases along the bed height, whereas the solid holdup decreases down the bed. However, the gas holdup is almost uniform in the bed. 相似文献
52.
A sufficient condition for the order of approximation of a continuous 2π periodic function with a givenmajorant for the modulus of continuity by the [F, d_n] means of its Fourier serier to be of Jackson order isobtained. This sufficient condition is shown to be not enough for the order of approximation by partial sums oftheir Fourier series to be of Jackson order. The error estimate is shown to be the best possible. 相似文献
53.
The present paper establishes sufficient conditions for the uniformly bounded of any solution of (1.1) and which tend to zero as t → ∞. 相似文献
54.
This paper studies the problem of uniformly dissipative solutions of somefifth order non-linear differential equations by the use of frequency domaintechnique. We use the generalized theorem of Yacubovich on dissipativity toobtain some new sufficient conditions of the existence of solutions that aredissipative for (1.1) and (1.2). 相似文献
55.
ZHANG Zhi-Li WANG Hong-Tao WANG Xiao-Wei MA Xiao-Yan LIU Jun-Yi R.J. Griff B.T. Golding 《有机化学》2003,23(Z1):10-10
Cobalamin-dependent methionine synthase plays a crucial role in folate metabolism and such would appear to be an excellent target for rational antifolate drug design. However, to date, no anticancer agents directed at this enzyme are available, but the enzyme is efficiently and specifically inhibited by N2O and this has proven invaluable for evaluating the biochemical consequence of enzyme inhibition and for mechanistic studies. [1,2] 2,5-Diamino-4-oxo-6-(3-butenyl) pyrimidine, a key intermediate in synthetic inhibitors of methionine synthase, was first synthesized using γbutenyl-β-ketoester and guanidine carbonate (Scheme 1). [3] 相似文献
56.
One of the Prussian blue analogs, molecular magnet Cu3^Ⅲ [Fe^Ⅲ (CN)6]2.11.6H2 O, was investigated by Moessbauer spectroscopy. It was found that transition temperature was around Tc = 18.5 K from paramagnetic phase to ferromagnetic phase. The β value of the critical exponent is around 0.338 at magnetic ordering temperature.Therefore, the ferromagnetic coupling interaction of Cu-Fe cyanide could be clearly explained by spin wave theory. 相似文献
57.
kofi A.Annan 《高等数学研究》2003,(2)
2002西安模拟联合国大会隆重举行 联合国秘书长科菲.安南先生发来贺信(英文)@kofi A.Annan 相似文献
58.
Xinghua Wang 《计算数学(英文版)》2003,(2)
The convergence problem of the family of Euler-Halley methods is considered under the Lipschitz condition with the L-average, and a united convergence theory with its applications is presented. 相似文献
59.
曼合布拜·热合木 《新疆大学学报(理工版)》2003,(1)
讨论了一类具有扩散率和 III类功能性反应的非自治捕食系统 ,证明了在适当条件下 ,系统是持久的 ,进一步如果系统是周期系统 ,则在一定条件下存在惟一全局稳定的周期解 . 相似文献
60.
Chen Yongnian 《模糊系统与数学》1995,(1)
ANTIFUZZYVECTORSPACES(Ⅱ)ChenYongnian(DepartmentofMathematics,XinjiangNormalUniversity,830054,Xinjiang,P.R.China)ANTIFUZZYVECT... 相似文献