全文获取类型
收费全文 | 16922篇 |
免费 | 1696篇 |
国内免费 | 1675篇 |
专业分类
化学 | 3942篇 |
晶体学 | 235篇 |
力学 | 2144篇 |
综合类 | 287篇 |
数学 | 10848篇 |
物理学 | 2837篇 |
出版年
2024年 | 26篇 |
2023年 | 155篇 |
2022年 | 185篇 |
2021年 | 302篇 |
2020年 | 421篇 |
2019年 | 390篇 |
2018年 | 373篇 |
2017年 | 451篇 |
2016年 | 503篇 |
2015年 | 364篇 |
2014年 | 698篇 |
2013年 | 1226篇 |
2012年 | 859篇 |
2011年 | 972篇 |
2010年 | 955篇 |
2009年 | 1078篇 |
2008年 | 1166篇 |
2007年 | 1206篇 |
2006年 | 1018篇 |
2005年 | 956篇 |
2004年 | 827篇 |
2003年 | 878篇 |
2002年 | 718篇 |
2001年 | 597篇 |
2000年 | 572篇 |
1999年 | 510篇 |
1998年 | 453篇 |
1997年 | 379篇 |
1996年 | 294篇 |
1995年 | 279篇 |
1994年 | 232篇 |
1993年 | 151篇 |
1992年 | 149篇 |
1991年 | 127篇 |
1990年 | 98篇 |
1989年 | 79篇 |
1988年 | 84篇 |
1987年 | 58篇 |
1986年 | 65篇 |
1985年 | 76篇 |
1984年 | 65篇 |
1983年 | 32篇 |
1982年 | 65篇 |
1981年 | 56篇 |
1980年 | 37篇 |
1979年 | 27篇 |
1978年 | 19篇 |
1977年 | 16篇 |
1976年 | 14篇 |
1972年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
It is well known that the mathematical models provide very important information for the research of human immunodeficiency virus-type 1 and hepatitis C virus (HCV). However, the infection rate of almost all mathematical models is linear. The linearity shows the simple interaction between the T cells and the viral particles. In this paper, we consider the classical mathematical model with saturation response of the infection rate. By stability analysis we obtain sufficient conditions on the parameters for the global stability of the infected steady state and the infection-free steady state. We also obtain the conditions for the existence of an orbitally asymptotically stable periodic solution. Numerical simulations are presented to illustrate the results. 相似文献
142.
Jiqin Deng 《Journal of Mathematical Analysis and Applications》2007,332(1):475-486
In this paper, by using the fixed point theory, under quite general conditions on the nonlinear term, we obtain an existence result of bounded positive solutions of Schrödinger equations in two-dimensional exterior domains. 相似文献
143.
N. E. Tovmasyan H. A. Babayan 《Journal of Contemporary Mathematical Analysis (Armenian Academy of Sciences)》2007,42(4):198-204
The paper establishes some solvability conditions of the Cauchy problem for linear differential equation in the class of monotone increasing functions. The results are applied for clarifying the possibility of flight along a given trajectory under existence of braking forces. 相似文献
144.
145.
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
146.
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
147.
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
148.
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
149.
T. Charitat B. Fourcade 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(3):333-336
An o-ring takes spontaneously the shape of a chair when strong enough torsion is applied in its tangent plane. This state
is metastable, since work has to be done on the o-ring to return to the circular shape. We show that this metastable state
exists in a Hamiltonian where curvature and torsion are coupled via an intrinsic curvature term. If the o-ring is constrained to be planar (2d case), this metastable state displays a kink-anti-kink
pair. This state is metastable if the ratio is less than , where C and A are the torsion and the bending elastic constants [#!landau!#]. In three dimensions, our variational approach shows that
. This model can be generalized to the case where the bend is induced by a concentration field which follows the variations
of the curvature.
Received: 27 August 1997 / Revised: 23 October 1997 / Accepted: 12 November 1997 相似文献
150.
AClassofCauchyProblemforQuasilinearHyperbolicSystemswiththeWeaklyDissipativeTerms¥LiuFagui;YangQiao(NorthChinaInstituteofWate... 相似文献