全文获取类型
收费全文 | 16528篇 |
免费 | 1585篇 |
国内免费 | 1695篇 |
专业分类
化学 | 3727篇 |
晶体学 | 229篇 |
力学 | 1929篇 |
综合类 | 307篇 |
数学 | 11018篇 |
物理学 | 2598篇 |
出版年
2024年 | 33篇 |
2023年 | 161篇 |
2022年 | 173篇 |
2021年 | 264篇 |
2020年 | 394篇 |
2019年 | 387篇 |
2018年 | 367篇 |
2017年 | 443篇 |
2016年 | 491篇 |
2015年 | 351篇 |
2014年 | 677篇 |
2013年 | 1212篇 |
2012年 | 823篇 |
2011年 | 973篇 |
2010年 | 946篇 |
2009年 | 1036篇 |
2008年 | 1133篇 |
2007年 | 1202篇 |
2006年 | 982篇 |
2005年 | 905篇 |
2004年 | 833篇 |
2003年 | 877篇 |
2002年 | 767篇 |
2001年 | 596篇 |
2000年 | 542篇 |
1999年 | 480篇 |
1998年 | 450篇 |
1997年 | 364篇 |
1996年 | 307篇 |
1995年 | 257篇 |
1994年 | 215篇 |
1993年 | 155篇 |
1992年 | 154篇 |
1991年 | 114篇 |
1990年 | 95篇 |
1989年 | 75篇 |
1988年 | 72篇 |
1987年 | 55篇 |
1986年 | 60篇 |
1985年 | 64篇 |
1984年 | 52篇 |
1983年 | 25篇 |
1982年 | 62篇 |
1981年 | 44篇 |
1980年 | 31篇 |
1979年 | 30篇 |
1978年 | 18篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1972年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
141.
章志飞 《浙江大学学报(理学版)》2003,30(6):609-611
利用Besov空间的热核刻画及压缩映射原理,研究半线性热方程ut-△u=u|u|a的初值问题,得到了当初值u0∈Lp0(Rn)且||u0||(B·)p-n (1/p0-1/p),∞(Rn)(p0=na/2,p>p0)充分小时,整体解的存在性及在一定条件下解的惟一性. 相似文献
142.
We show that the complex projection of a completely positive quaternionic map of quaternionic density matrices is a positive
map in the space of complex density matrices, and we briefly outline some of its properties. To illustrate this result, we
study the complex projection of a one-parameter quaternionic unitary dynamics of a spin-1/2 quantum system.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 151, No. 3, pp. 360–370, June, 2007. 相似文献
143.
关于《一类奇异边值问题的正解》的注记 总被引:3,自引:0,他引:3
文[4]通过构造反例断言文[1]中定理的必要性证明有误,本文首先指出文[4] 的这个断言不正确,然后对文[4]中定理2.1作了本质性的改进. 相似文献
144.
薛儒英 《浙江大学学报(理学版)》1991,(2)
本文讨论了半线性椭圆方程△u+f(u)=0在三种边界条件下正解的存在性和唯一性,给出了正解存在和唯一的一些条件. 相似文献
145.
g1.IntroductionWeconsiderthefollowingfirstorderquasilinearhyperbolicequationswithinternaIdissipa-tlveterm:U, A(U)U. F(U)=o(1.1)whereUeR2isunknownvectorfunction,A(U)is2X2knownsmoothmatrix,F(U)is2X2knownsmoothvectorfunction.Itiswell-knownthatCauchyproblemoftheequations(l.1)hasbeenwidelystudied(Ll-6J),however,theequations(l.1)withperiedicinitialdatahasbeenhardlystudiedandonesfindthatitiscomplicatedforproblemwithperiodicinitialdata.Becausetheperiodicdis-turbanceLlirectlyinfluencesthebounde… 相似文献
146.
Summary Hydroxypropyl methyl cellulose (HPMC) and polyethylene glycol 400 (PEG 400) content in HypoTears™ Daily Dose ophthalmic solution
are determined simultaneously by size exclusion chromatography. The retention times of HPMC and PEG 400 are 10.6 and 15.4
minutes, respectively. The method requires minimal sample pretreatment and is accurate and reproducible. The peak area response
from a refractive index detector versus HPMC and PEG 400 concentration is linear over the range of 50–150 % of their label
claims of 2.5 mg/mL and 10 mg/mL, respectively. The mean absolute recoveries of HPMC and PEG 400 at their label claim using
the described method are 98.9±1.3 % and 100.4±1.2 % (mean±SD, n=12), respectively. 相似文献
147.
AClassofCauchyProblemforQuasilinearHyperbolicSystemswiththeWeaklyDissipativeTerms¥LiuFagui;YangQiao(NorthChinaInstituteofWate... 相似文献
148.
Yi Zhan 《应用数学学报(英文版)》1997,13(3):235-242
In [1] we construct a unique bounded Hölder continuous viscosity solution for the nonlinear PDEs with the evolutionp-Laplacian equation and its anisotropic version as typical examples. In this part, we investigate the Lipschitz continuity of the free boundary of viscosity solution and its asymptotic spherical symmetricity, however, this result does not include the anisotropic case.This research is supported by the National Natural Sciences Foundation of China. 相似文献
149.
本文利用Liapunov-Schmidt方法获得了高维自治系统在共振情况下决定周期解个数的分支函数,并通过计算分支函数的主项,分析分支函数的零点,研究了具两对共轭特征根的四维系统多个周期解的共振分支问题. 相似文献
150.
F. Blanchini 《Journal of Optimization Theory and Applications》1991,71(3):465-484
The linear state feedback synthesis problem for uncertain linear systems with state and control constraints is considered. We assume that the uncertainties are present in both the state and input matrices and they are bounded. The main goal is to find a linear control law assuring that both state and input constraints are fulfilled at each time. The problem is solved by confining the state within a compact and convex positively invariant set contained in the allowable state region.It is shown that, if the controls, the state, and the uncertainties are subject to linear inequality constraints and if a candidate compact and convex polyhedral set is assigned, a feedback matrix assuring that this region is positively invariant for the closed-loop system is found as a solution of a set of linear inequalities for both continuous and discrete time design problems.These results are extended to the case in which additive disturbances are present. The relationship between positive invariance and system stability is investigated and conditions for the existence of positively invariant regions of the polyhedral type are given.The author is grateful to Drs. Vito Cerone and Roberto Tempo for their comments. 相似文献