全文获取类型
收费全文 | 709篇 |
免费 | 54篇 |
国内免费 | 38篇 |
专业分类
化学 | 92篇 |
晶体学 | 2篇 |
力学 | 19篇 |
综合类 | 3篇 |
数学 | 593篇 |
物理学 | 92篇 |
出版年
2023年 | 6篇 |
2022年 | 22篇 |
2021年 | 17篇 |
2020年 | 21篇 |
2019年 | 22篇 |
2018年 | 19篇 |
2017年 | 17篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 25篇 |
2013年 | 64篇 |
2012年 | 29篇 |
2011年 | 36篇 |
2010年 | 31篇 |
2009年 | 42篇 |
2008年 | 32篇 |
2007年 | 46篇 |
2006年 | 35篇 |
2005年 | 33篇 |
2004年 | 34篇 |
2003年 | 25篇 |
2002年 | 28篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 21篇 |
1998年 | 17篇 |
1997年 | 14篇 |
1996年 | 18篇 |
1995年 | 3篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有801条查询结果,搜索用时 0 毫秒
51.
52.
The menace of insect pests is a topic of major concern throughout the world. Chemical pesticides are conventionally used to control these insect pests. However, the adverse effects of these synthetic pesticides, such as high toxicity from residues in food, contamination of water and the environment resulting in human health hazard and resistance of the pest to the pesticides have necessitated development of some nonconventional approaches of biological pest control. In this research, we have focused on a mathematical model of biological pest control using the sterile insect release technique. Unlike most of the existing modeling studies in this field that mainly deal with the pest population only, we have incorporated the crop population as a distinct dynamical equation together with the fertile and sterile insect pests. Local stability analysis is performed around the crop and fertile insect free axial equilibrium, the fertile‐insect‐free boundary equilibrium, the crop‐free boundary equilibrium and the equilibrium point of coexistence. From the study we have derived a number of thresholds for the SIRR (the main parameter for our study) that cause existence and or extinction of the crop population as well as the fertile insect pests. A global study of the model system using comparison arguments revealed existence of a global attractor for the system. Numerical simulations are done to support and augment analytical results. 相似文献
53.
Núñez-Regueira L. Rodríguez-Añón J. Proupín-Castiñeiras J. Romero-García A. 《Journal of Thermal Analysis and Calorimetry》2001,66(1):281-292
Calorific values and flammability changes during a year for forest waste originating from silviculture task in Galicia (NW
Spain) are reported. These waste materials are becoming to be used as alternative fuels.
The present study was made on several hardwood forest species. These forest species occupy nowadays approximately 30% of the
total forest surface of Galicia.
Calorific values were measured by static bomb calorimeter in an oxygen atmosphere. Flammability was determined using a standard
epiradiator. Simultaneously, some other parameters such as elementary chemical composition, heavy metal contents, moisture,
density, ash percentage after combustion in the bomb, and main bioclimatic characteristics, were also determined.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
54.
主要建立了奇异一阶周期系统的多重正解,证明了在适当的条件下这个问题至少存在两个解.第一个正解的存在性是利用非线性L eray-Schauder抉择定理得到的,第二个解是利用K rasnoselsk ii锥不动点定理得到的. 相似文献
55.
WANGYOUBIN ZHAOAIMIN YANJURANG 《高校应用数学学报(英文版)》1998,13(4):391-396
The necessary and sufficient conditions for the oscillations of every solution of the nonlinear delay equation x(t) f(x(t l)) g(x([t-k]))=0 are oblained. 相似文献
56.
57.
Mathematical Notes - 相似文献
58.
利用Mawhin连续性定理研究了具有多偏差变元的Rayleigh方程周期解的存在性,得到了一些新的结果,补充和完善了已有的结果. 相似文献
59.
Danilo šuster 《Acta Analytica》2004,19(33):45-54
Modal arguments for incompatibility of freedom and determinism are typically based on the “transfer principle” for inability
to act otherwise (Beta). The principle of agglomerativity (closure under conjunction introduction) is derivable from Beta.
The most convincing counterexample to Beta is based on the denial of Agglomeration. The defender of the modal argument has
two ways to block counterexamples to Beta: (i) use a notion of inability to act otherwise which is immune to the counterexample
to agglomerativity; (ii) replace Beta with a logically stronger principle Beta 2. I argue that the second strategy fails because
the strengthened principle and Agglomeration together entail Beta. So this strategy makes sense only if Beta 2 is applied
without Agglomeration. But if Beta 2 is used without Agglomeration, then the incompatibilist will undercut the rationale for
the premise of his argument. I illustrate this point with the analysis of Warfield (1996) and his use of Beta 2 in the so
called direct argument for incompatibilism. 相似文献
60.
Jürgen Appell 《Journal of Mathematical Analysis and Applications》2007,332(2):1134-1147
Using a continuation theorem for contractions, the existence, uniqueness, and an approximation method for a class of nonlinear boundary value problems on an unbounded interval is obtained. The results apply in particular to the problem in the title. 相似文献