全文获取类型
收费全文 | 10429篇 |
免费 | 1961篇 |
国内免费 | 764篇 |
专业分类
化学 | 3166篇 |
晶体学 | 79篇 |
力学 | 920篇 |
综合类 | 172篇 |
数学 | 4514篇 |
物理学 | 4303篇 |
出版年
2023年 | 107篇 |
2022年 | 155篇 |
2021年 | 306篇 |
2020年 | 339篇 |
2019年 | 386篇 |
2018年 | 342篇 |
2017年 | 441篇 |
2016年 | 482篇 |
2015年 | 404篇 |
2014年 | 557篇 |
2013年 | 986篇 |
2012年 | 622篇 |
2011年 | 678篇 |
2010年 | 584篇 |
2009年 | 630篇 |
2008年 | 693篇 |
2007年 | 634篇 |
2006年 | 565篇 |
2005年 | 510篇 |
2004年 | 442篇 |
2003年 | 465篇 |
2002年 | 391篇 |
2001年 | 310篇 |
2000年 | 275篇 |
1999年 | 271篇 |
1998年 | 208篇 |
1997年 | 217篇 |
1996年 | 165篇 |
1995年 | 155篇 |
1994年 | 122篇 |
1993年 | 90篇 |
1992年 | 73篇 |
1991年 | 67篇 |
1990年 | 54篇 |
1989年 | 51篇 |
1988年 | 36篇 |
1987年 | 46篇 |
1986年 | 35篇 |
1985年 | 52篇 |
1984年 | 34篇 |
1983年 | 19篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 11篇 |
1979年 | 23篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 11篇 |
1974年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
具有n个顶点且度序列为(m,2,…,2,1,…,1)(1的重数为m)的连通图不止一个(这些图均为树),而每个树对应唯一一个段序列(l1,l2,…,lm).通过对任意一树移动最长段的悬挂点到最短段悬挂点的方式得到另一树,比较前后两树的覆盖成本和反向覆盖成本,给出了具有最小覆盖成本和反向覆盖成本的极树,并且进一步给出了取得最小覆盖成本和反向覆盖成本的顶点. 相似文献
2.
For a general dyadic grid, we give a Calderón–Zygmund type decomposition, which is the principle fact about the multilinear maximal function on the upper half‐spaces. Using the decomposition, we study the boundedness of . We obtain a natural extension to the multilinear setting of Muckenhoupt's weak‐type characterization. We also partially obtain characterizations of Muckenhoupt's strong‐type inequalities with one weight. Assuming the reverse Hölder's condition, we get a multilinear analogue of Sawyer's two weight theorem. Moreover, we also get Hytönen–Pérez type weighted estimates. 相似文献
3.
Bilender P. Allahverdiev 《Mathematical Methods in the Applied Sciences》2019,42(1):229-236
In this study, maximal dissipative second‐order dynamic operators on semi‐infinite time scale are studied in the Hilbert space , that the extensions of a minimal symmetric operator in limit‐point case. We construct a self‐adjoint dilation of the dissipative operator together with its incoming and outgoing spectral representations so that we can determine the scattering function of the dilation as stated in the scheme of Lax‐Phillips. Moreover, we construct a functional model of the dissipative operator and identify its characteristic function in terms of the Weyl‐Titchmarsh function of a self‐adjoint second‐order dynamic operator. Finally, we prove the theorems on completeness of the system of root functions of the dissipative and accumulative dynamic operators. 相似文献
4.
Awatif Alqahtani Mohamed Jleli Bessem Samet 《Mathematical Methods in the Applied Sciences》2019,42(3):861-870
In this paper, some nonlocal in time differential inequalities of Sobolev type are considered. Using the nonlinear capacity method, sufficient conditions for the nonexistence of nontrivial global classical solutions are provided. 相似文献
5.
ABSTRACTA class of semilinear parabolic reaction diffusion equations with multiple time delays is considered. These time delays and corresponding weights are to be optimized such that the associated solution of the delay equation is the best approximation of a desired state function. The differentiability of the mapping is proved that associates the solution of the delay equation to the vector of weights and delays. Based on an adjoint calculus, first-order necessary optimality conditions are derived. Numerical test examples show the applicability of the concept of optimizing time delays. 相似文献
6.
《Discrete Mathematics》2021,344(12):112601
7.
8.
9.
Corinne Rondeau-Mouro Mireille Cambert Laurent Blondel Yves Diascorn Léo Mbaya Nor Nadiah Binti Ahmad Nazari Sarah Helary Tiphaine Lucas 《Magnetic resonance in chemistry : MRC》2022,60(7):678-691
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample. 相似文献
10.