全文获取类型
收费全文 | 85989篇 |
免费 | 1734篇 |
国内免费 | 1628篇 |
专业分类
化学 | 30427篇 |
晶体学 | 922篇 |
力学 | 7159篇 |
综合类 | 77篇 |
数学 | 32738篇 |
物理学 | 18028篇 |
出版年
2024年 | 50篇 |
2023年 | 197篇 |
2022年 | 370篇 |
2021年 | 379篇 |
2020年 | 450篇 |
2019年 | 454篇 |
2018年 | 10695篇 |
2017年 | 10540篇 |
2016年 | 6445篇 |
2015年 | 1292篇 |
2014年 | 800篇 |
2013年 | 984篇 |
2012年 | 4485篇 |
2011年 | 11239篇 |
2010年 | 6155篇 |
2009年 | 6499篇 |
2008年 | 7129篇 |
2007年 | 9168篇 |
2006年 | 618篇 |
2005年 | 1631篇 |
2004年 | 1775篇 |
2003年 | 2187篇 |
2002年 | 1263篇 |
2001年 | 428篇 |
2000年 | 453篇 |
1999年 | 283篇 |
1998年 | 292篇 |
1997年 | 246篇 |
1996年 | 297篇 |
1995年 | 219篇 |
1994年 | 171篇 |
1993年 | 173篇 |
1992年 | 108篇 |
1991年 | 110篇 |
1990年 | 93篇 |
1989年 | 108篇 |
1988年 | 88篇 |
1987年 | 82篇 |
1986年 | 84篇 |
1985年 | 82篇 |
1984年 | 61篇 |
1983年 | 51篇 |
1982年 | 51篇 |
1981年 | 48篇 |
1980年 | 50篇 |
1979年 | 46篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
23.
24.
Kai He Tsegaye TadesseTsega Xi Liu Jiantao Zai Xin‐Hao Li Xuejiao Liu Wenhao Li Nazakat Ali Xuefeng Qian 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):12029-12035
The modulation of electron density is an effective option for efficient alternative electrocatalysts. Here, p‐n junctions are constructed in 3D free‐standing FeNi‐LDH/CoP/carbon cloth (CC) electrode (LDH=layered double hydroxide). The positively charged FeNi‐LDH in the space‐charge region can significantly boost oxygen evolution reaction. Therefore, the j at 1.485 V (vs. RHE) of FeNi‐LDH/CoP/CC achieves ca. 10‐fold and ca. 100‐fold increases compared to those of FeNi‐LDH/CC and CoP/CC, respectively. Density functional theory calculation reveals OH? has a stronger trend to adsorb on the surface of FeNi‐LDH side in the p‐n junction compared to individual FeNi‐LDH further verifying the synergistic effect in the p‐n junction. Additionally, it represents excellent activity toward water splitting. The utilization of heterojunctions would open up an entirely new possibility to purposefully regulate the electronic structure of active sites and promote their catalytic activities. 相似文献
25.
26.
27.
28.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
29.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective. 相似文献
30.
The theory of tree-growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree-growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree-structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data. 相似文献