全文获取类型
收费全文 | 9691篇 |
免费 | 1307篇 |
国内免费 | 3419篇 |
专业分类
化学 | 6627篇 |
晶体学 | 407篇 |
力学 | 567篇 |
综合类 | 142篇 |
数学 | 3631篇 |
物理学 | 3043篇 |
出版年
2024年 | 26篇 |
2023年 | 107篇 |
2022年 | 227篇 |
2021年 | 278篇 |
2020年 | 310篇 |
2019年 | 335篇 |
2018年 | 310篇 |
2017年 | 479篇 |
2016年 | 603篇 |
2015年 | 413篇 |
2014年 | 639篇 |
2013年 | 1078篇 |
2012年 | 898篇 |
2011年 | 889篇 |
2010年 | 792篇 |
2009年 | 792篇 |
2008年 | 786篇 |
2007年 | 744篇 |
2006年 | 624篇 |
2005年 | 566篇 |
2004年 | 473篇 |
2003年 | 365篇 |
2002年 | 387篇 |
2001年 | 319篇 |
2000年 | 262篇 |
1999年 | 255篇 |
1998年 | 210篇 |
1997年 | 181篇 |
1996年 | 164篇 |
1995年 | 146篇 |
1994年 | 131篇 |
1993年 | 91篇 |
1992年 | 79篇 |
1991年 | 45篇 |
1990年 | 60篇 |
1989年 | 40篇 |
1988年 | 34篇 |
1987年 | 19篇 |
1986年 | 12篇 |
1985年 | 23篇 |
1984年 | 18篇 |
1983年 | 18篇 |
1982年 | 28篇 |
1981年 | 33篇 |
1980年 | 31篇 |
1979年 | 20篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 20篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We study a system of quasilinear equations describing one-dimensional flow of a viscous compressible heat-conducting medium with a nonmonotone state function and mass force. The large-time behavior of solutions is considered for arbitrarily large initial data. In spite of possible nonuniqueness and discontinuity of the stationary solution, we prove L2-stabilization for the stress and heat flux as t → ∞ along with corresponding global energy estimates for them. The new method of proof utilizes a combination of energy type equalities for the stress and heat flux. Consequently, H1-stabilization of the velocity and temperature along with global estimates for their derivatives are valid as well. 相似文献
92.
给出模糊半群上的模糊同余的概念,并进一步研究它的一些基本代数性质。同时研究带有模糊半群上的模糊同余扩张性质(FCEPF)的半群类,得到一个半群有模糊半群上的模糊同余扩张性质、有模糊同余扩张性质(FCEP)、有同余扩张性质(CEP)三个条件是等价的。 相似文献
93.
QiaoHongYAO FuYouLI LuSHAN ChunHuiHUANG DongDongYIN 《中国化学快报》2003,14(11):1185-1188
A new photoresponsive D-π-A dye, mPS, has been designed and synthesized.Compared to the parent dye PS, IPCE values in the region from 400 nm to 560 nm was greatly improved upon changing the attaching group from the p- position to the o- position of the π-conjugation bridge. A solar cell based on mPS generated a remarkably high overall yield η of 5.4% under irradiation of 80.0 mW cm^-2 white light from a Xe lamp, Compared with PS, the overall yield η increased by 64%. 相似文献
94.
Shi Rong LI 《数学学报(英文版)》2005,21(4):797-802
For a finite group G, let T(G) denote a set of primes such that a prime p belongs to T(G) if and only if p is a divisor of the index of some maximal subgroup of G. It is proved that if G satisfies any one of the following conditions: (1) G has a p-complement for each p∈T(G); (2)│T(G)│= 2: (3) the normalizer of a Sylow p-subgroup of G has prime power index for each odd prime p∈T(G); then G either is solvable or G/Sol(G)≌PSL(2, 7) where Sol(G) is the largest solvable normal subgroup of G. 相似文献
95.
Jacquelyn A. Carioscia Lauren Schneidewind Casey O'Brien Robert Ely Caitlin Feeser Neil Cramer Christopher N. Bowman 《Journal of polymer science. Part A, Polymer chemistry》2007,45(23):5686-5696
The ability to prepare high Tg low shrinkage thiol–ene materials is attractive for applications such as coatings and dental restoratives. However, thiol and nonacrylated vinyl materials typically consist of a flexible backbone, limiting the utility of these polymers. Hence, it is of importance to synthesize and investigate thiol and vinyl materials of varying backbone chemistry and stiffness. Here, we investigate the effect of backbone chemistry and functionality of norbornene resins on polymerization kinetics and glass transition temperature (Tg) for several thiol–norbornene materials. Results indicate that Tgs as high as 94 °C are achievable in thiol–norbornene resins of appropriately controlled chemistry. Furthermore, both the backbone chemistry and the norbornene moiety are important factors in the development of high Tg materials. In particular, as much as a 70 °C increase in Tg was observed in a norbornene–thiol specimen when compared with a sample prepared using allyl ether monomer of analogous backbone chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5686–5696, 2007 相似文献
96.
Stan J. Surma 《Logica Universalis》2007,1(1):209-219
The connection presented in this paper mirror-links two metamathematical structures, the finitary closure operators, and the
compact consistency properties, in such a way that a specification of one structure induces a provably equivalent specification
of the other.
Mathematics Subject Classification (2000): Primary 06A15, Secondary 28E10 03B22 相似文献
97.
本文讨论了在区域提纯过程中,研究液态金属流的表面张力时提出的一个带有非负参数Q的两点边值问题.利用上、下解方法和Schauder不动点定理,证明了当0Q851时,该问题至少有一个解,对已有结果0Q<1进行了重要的改进. 相似文献
98.
本文研究弱一致Opial条件的性质;弱一致Opial条件与弱一致Opial条件的对偶性;证明当对偶空间有弱一致Opial条件时该Banach空间具有不动点性. 相似文献
99.
D—^3He聚变动力可行性研究 总被引:9,自引:3,他引:6
本文首先简要地讨论D-3He聚变的物理要求并与D-T聚变作相应的比较,然后运用目前的约束定律和第一稳定区β极限,对计划的近期ETR规模装置(如CIT,TIBER,FER,NET)进行D-3He得失相当和点火实验的可行性研究,并对高径比第二稳定区D-3He托卡马克堆进行参数学研究,最后指出潜在的缩短商用化进程可能性。 相似文献
100.
On the basis of Tsallis’ entropy and the joint probability factorization condition, two controversial problems existing in Tsallis’ statistics are investigated, where one is whether energy is extensive or not and the other is whether it is necessary to introduce the so-called generalized zeroth law of thermodynamics or not. The results obtained show clearly that like entropy, energy is also nonextensive in Tsallis’ statistics, and that the zeroth law of thermodynamics has been implicitly used in Tsallis’ statistics since 1988. Moreover, it is expounded that the standard energy additivity rule adopted by a great number of researchers is not suitable in Tsallis’ statistics, because its corollary is in contradiction with the zeroth law of thermodynamics. 相似文献