全文获取类型
收费全文 | 46507篇 |
免费 | 8030篇 |
国内免费 | 6211篇 |
专业分类
化学 | 32983篇 |
晶体学 | 636篇 |
力学 | 2910篇 |
综合类 | 487篇 |
数学 | 5682篇 |
物理学 | 18050篇 |
出版年
2024年 | 39篇 |
2023年 | 840篇 |
2022年 | 958篇 |
2021年 | 1368篇 |
2020年 | 1724篇 |
2019年 | 1701篇 |
2018年 | 1468篇 |
2017年 | 1379篇 |
2016年 | 2082篇 |
2015年 | 2113篇 |
2014年 | 2584篇 |
2013年 | 3308篇 |
2012年 | 3992篇 |
2011年 | 4301篇 |
2010年 | 3113篇 |
2009年 | 3051篇 |
2008年 | 3340篇 |
2007年 | 3066篇 |
2006年 | 2935篇 |
2005年 | 2276篇 |
2004年 | 1864篇 |
2003年 | 1602篇 |
2002年 | 1501篇 |
2001年 | 1206篇 |
2000年 | 1146篇 |
1999年 | 1023篇 |
1998年 | 884篇 |
1997年 | 781篇 |
1996年 | 760篇 |
1995年 | 690篇 |
1994年 | 608篇 |
1993年 | 489篇 |
1992年 | 477篇 |
1991年 | 371篇 |
1990年 | 340篇 |
1989年 | 261篇 |
1988年 | 225篇 |
1987年 | 195篇 |
1986年 | 170篇 |
1985年 | 169篇 |
1984年 | 109篇 |
1983年 | 83篇 |
1982年 | 61篇 |
1981年 | 38篇 |
1980年 | 18篇 |
1979年 | 10篇 |
1977年 | 7篇 |
1970年 | 3篇 |
1959年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
41.
Ding Q. Yao M. Wu Sh. Zeng M. Xue N. Wu D. Xu J. 《Journal of Applied Spectroscopy》2022,89(4):712-718
Journal of Applied Spectroscopy - Based on partial least squares (PLS) analysis, the effects of different smoothing points and different preprocessing methods on the accuracy and precision of the... 相似文献
42.
Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the... 相似文献
43.
三维层状双金属氢氧化物简称3D-LDHs,是在制备普通二维层状金属氢氧化物(2D-LDHs)的过程中,改变反应条件得到的三维结构产物.它的组成单元与二维产物相同为完整LDHs纳米片,基本保留了LDHs具有的碱性、阴离子可交换性和记忆效应等特点,同时又因三维结构获得了更大的比表面积、丰富的孔隙结构以及形成复合材料的能力,在吸附、催化和电化学等方面的应用性能得以增强.本文概述了3D-LDHs的组成结构、主要制备方法及产物形貌,并对未来的研究方向进行了展望. 相似文献
44.
45.
Chao Liu Liying Wang Lin Yang Famei Wang Chunhong Xu Jingwei Lv Guanglai Fu Xianli Li Qiang Liu Haiwei Mu Tao Sun Paul K. Chu 《Physics letters. A》2019,383(25):3200-3206
A single-polarization filter comprising a gold-coated photonic crystal fiber based on surface plasmon resonance is designed and investigated. The pattern matching and coupled polarization characteristics analyzed by the full-vector finite element method (FEM) and losses at 1,540 nm are achieved to 1,016.01739 dB/cm (x-pol core mode) and 33.81917 dB/cm (y-pol core mode). The crosstalk (CT) value of the 1,540 nm band is ?853.12653 dB for fiber length and the bandwidth is 850 nm. The working wavelength of the filter ranges from 1,280 nm to 1,540 nm by varying the diameter of outer air holes (), the diameter of inner air holes (), the metal film thickness (t), as well as the liquid refractive index (n). 相似文献
46.
Dekun Wu Dr. Qing Xu Dr. Jing Qian Prof. Xiaopeng Li Prof. Yuhan Sun 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3105-3111
Covalent organic frameworks (COFs) are a new class of crystalline porous polymers comprised mainly of carbon atoms, and are versatile for the integration of heteroatoms such as B, O, and N into the skeletons. The designable structure and abundant composition render COFs useful as precursors for heteroatom-doped porous carbons for energy storage and conversion. Herein, we describe a multifunctional electrochemical catalyst obtained through pyrolysis of a bimetallic COF. The catalyst possesses hierarchical pores and abundant iron and cobalt nanoparticles embedded with standing carbon layers. By integrating these features, the catalyst exhibits excellent electrochemical catalytic activity in the oxygen reduction reaction (ORR), with a 50 mV positive half-wave potential, a higher limited diffusion current density, and a much smaller Tafel slope than a Pt-C catalyst. Moreover, the catalyst displays superior electrochemical performance toward the hydrogen evolution reaction (HER), with overpotentials of −0.26 V and −0.33 V in acidic and alkaline aqueous solution, respectively, at a current density of 10 mA cm−2. The overpotential in the catalysis of the oxygen evolution reaction (OER) was 1.59 V at the same current density. 相似文献
47.
Dr. Jun Zeng Dr. Zhichao Wang Dr. Xin Huang Dr. Sabine S. Eckstein Prof. Dr. Xiaohui Lin Prof. Dr. Hailong Piao Prof. Dr. Cora Weigert Dr. Peiyuan Yin Prof. Dr. Rainer Lehmann Prof. Dr. Guowang Xu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(21):5427-5432
Mass spectrometry (MS) driven metabolomics is a frequently used tool in various areas of life sciences; however, the analysis of polar metabolites is less commonly included. In general, metabolomic analyses lead to the detection of the total amount of all covered metabolites. This is currently a major limitation with respect to metabolites showing high turnover rates, but no changes in their concentration. Such metabolites and pathways could be crucial metabolic nodes (e.g., potential drug targets in cancer metabolism). A stable-isotope tracing capillary electrophoresis–mass spectrometry (CE-MS) metabolomic approach was developed to cover both polar metabolites and isotopologues in a non-targeted way. An in-house developed software enables high throughput processing of complex multidimensional data. The practicability is demonstrated analyzing [U-13C]-glucose exposed prostate cancer and non-cancer cells. This CE-MS-driven analytical strategy complements polar metabolite profiles through isotopologue labeling patterns, thereby improving not only the metabolomic coverage, but also the understanding of metabolism. 相似文献
48.
Numerical Algorithms - A singularly perturbed Volterra integro-differential equation with an integrable singularity in the integral term is considered. The upwind difference method is used to... 相似文献
49.
Journal of Statistical Physics - In this paper, averaging principle for the time-dependent stochastic evolution equations (TDSEEs) with infinite delay is investigated. In proper non-Lipschitz... 相似文献
50.