全文获取类型
收费全文 | 88524篇 |
免费 | 7290篇 |
国内免费 | 5983篇 |
专业分类
化学 | 24501篇 |
晶体学 | 1821篇 |
力学 | 4071篇 |
综合类 | 591篇 |
数学 | 25879篇 |
物理学 | 44934篇 |
出版年
2023年 | 261篇 |
2022年 | 251篇 |
2021年 | 453篇 |
2020年 | 792篇 |
2019年 | 1148篇 |
2018年 | 1091篇 |
2017年 | 832篇 |
2016年 | 700篇 |
2015年 | 611篇 |
2014年 | 1463篇 |
2013年 | 2230篇 |
2012年 | 1513篇 |
2011年 | 2226篇 |
2010年 | 2802篇 |
2009年 | 7486篇 |
2008年 | 8594篇 |
2007年 | 7122篇 |
2006年 | 6400篇 |
2005年 | 4504篇 |
2004年 | 4176篇 |
2003年 | 4441篇 |
2002年 | 5599篇 |
2001年 | 3979篇 |
2000年 | 3833篇 |
1999年 | 3600篇 |
1998年 | 3026篇 |
1997年 | 2125篇 |
1996年 | 1886篇 |
1995年 | 2275篇 |
1994年 | 2221篇 |
1993年 | 1653篇 |
1992年 | 1150篇 |
1991年 | 874篇 |
1990年 | 711篇 |
1989年 | 624篇 |
1988年 | 590篇 |
1987年 | 416篇 |
1985年 | 976篇 |
1984年 | 647篇 |
1983年 | 500篇 |
1982年 | 666篇 |
1981年 | 807篇 |
1980年 | 738篇 |
1979年 | 577篇 |
1978年 | 592篇 |
1977年 | 549篇 |
1976年 | 547篇 |
1975年 | 321篇 |
1974年 | 358篇 |
1973年 | 465篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Land exhibits diverse functions under the combined influence of natural and human forces. A production–living–ecology functional classification system was constructed by integrating land, ecosystem, and landscape functions. The land functional value was calculated by systematically integrating ecosystem service value assessments. The primary and secondary functions, as well as combinations of different land‐use types, were determined using vertical and horizontal comparison methods. The production–living–ecology ranges were then delineated in Puge County, which is a typical mountain county in China. The production–living–ecology functions identified were well connected with the current land‐use types. The “production–living–ecology” space in Puge County showed obvious multifunctionality and agglomeration. The function identification system proposed in this paper integrated multiple methods, overcame the difficulty of direct quantitative identification of land functions. The methods used to map and quantify land function will enhance our ability to understand and model land system changes and adequately inform policies and planning. Summary for Managers
- The function valuation method constructed in this paper could be used to reflect the multifunctionality and importance of land use and provide guidance and a quantitative basis for regional development planning.
- The spatial classification results provided in this paper could offer a valuable reference for the land management department to scientifically formulate land use planning.
- Under the goal of creating a group‐type urban development pattern and constructing an ecological protection pattern in Puge County, the hotspot analysis results of this paper can provide decision‐making tools and alternative spatial plans.
72.
Palle E.T. Jorgensen Erin P.J. Pearse 《Journal of Mathematical Analysis and Applications》2019,469(2):765-807
Motivated by applications to machine learning, we construct a reversible and irreducible Markov chain whose state space is a certain collection of measurable sets of a chosen l.c.h. space . We study the resulting network (connected undirected graph), including transience, Royden and Riesz decompositions, and kernel factorization. We describe a construction for Hilbert spaces of signed measures which comes equipped with a new notion of reproducing kernels and there is a unique solution to a regularized optimization problem involving the approximation of functions by functions of finite energy. The latter has applications to machine learning (for Markov random fields, for example). 相似文献
73.
74.
75.
76.
77.
78.
79.
Martin Costabel 《Mathematische Nachrichten》2019,292(10):2165-2173
We construct a bounded C1 domain Ω in for which the regularity for the Dirichlet and Neumann problems for the Laplacian cannot be improved, that is, there exists f in such that the solution of in Ω and either on or on is contained in but not in for any . An analogous result holds for Sobolev spaces with . 相似文献
80.
We prove that a WLD subspace of the space consisting of all bounded, countably supported functions on a set Γ embeds isomorphically into if and only if it does not contain isometric copies of . Moreover, a subspace of is constructed that has an unconditional basis, does not embed into , and whose every weakly compact subset is separable (in particular, it cannot contain any isomorphic copies of ). 相似文献