全文获取类型
收费全文 | 111671篇 |
免费 | 6478篇 |
国内免费 | 5100篇 |
专业分类
化学 | 48006篇 |
晶体学 | 1130篇 |
力学 | 8990篇 |
综合类 | 363篇 |
数学 | 36218篇 |
物理学 | 28542篇 |
出版年
2023年 | 778篇 |
2022年 | 936篇 |
2021年 | 1188篇 |
2020年 | 1519篇 |
2019年 | 1441篇 |
2018年 | 11388篇 |
2017年 | 11175篇 |
2016年 | 7689篇 |
2015年 | 2534篇 |
2014年 | 2288篇 |
2013年 | 3037篇 |
2012年 | 6779篇 |
2011年 | 13536篇 |
2010年 | 7740篇 |
2009年 | 8075篇 |
2008年 | 8860篇 |
2007年 | 10641篇 |
2006年 | 2087篇 |
2005年 | 2905篇 |
2004年 | 2750篇 |
2003年 | 2947篇 |
2002年 | 1954篇 |
2001年 | 1035篇 |
2000年 | 1042篇 |
1999年 | 967篇 |
1998年 | 857篇 |
1997年 | 771篇 |
1996年 | 803篇 |
1995年 | 682篇 |
1994年 | 585篇 |
1993年 | 531篇 |
1992年 | 400篇 |
1991年 | 405篇 |
1990年 | 368篇 |
1989年 | 284篇 |
1988年 | 242篇 |
1987年 | 209篇 |
1986年 | 182篇 |
1985年 | 175篇 |
1984年 | 117篇 |
1983年 | 102篇 |
1982年 | 100篇 |
1981年 | 66篇 |
1980年 | 62篇 |
1979年 | 48篇 |
1914年 | 45篇 |
1913年 | 40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
1.
In this paper, we study vanishing and splitting results on a complete smooth metric measure space \((M^n,g,\mathrm {e}^{-f}\mathrm {d}v)\) with various negative m-Bakry-Émery Ricci curvature lower bounds in terms of the first eigenvalue \(\lambda _1(\Delta _f)\) of the weighted Laplacian \(\Delta _f\), i.e., \(\mathrm {Ric}_{m,n}\ge -a\lambda _1(\Delta _f)-b\) for \(0<a\le \dfrac{m}{m-1}, b\ge 0\). In particular, we consider three main cases for different a and b with or without conditions on \(\lambda _1(\Delta _f)\). These results are extensions of Dung and Vieira, and weighted generalizations of Li-Wang, Dung-Sung, and Vieira.
相似文献2.
Designs, Codes and Cryptography - Large sets of combinatorial designs has always been a fascinating topic in design theory. These designs form a partition of the whole space into combinatorial... 相似文献
3.
Nonlinear Dynamics - This article considers a reaction–diffusion predator–prey model with schooling behavior both in predator and prey species and subject to the homogeneous Neumann... 相似文献
4.
Song Zi-Long Zhu Yun Liu Jing-Rui Guo Shu-Ke Gu Yu-Cheng Han Xinya Dong Hong-Qiang Sun Qi Zhang Wei-Hua Zhang Ming-Zhi 《Molecular diversity》2021,25(1):205-221
Molecular Diversity - Based on the strategy of diversity-oriented synthesis and the structures of natural product pimprinine and streptochlorin, two series of novel pimprinine derivatives... 相似文献
5.
Hu Duo-Duo Gao Qian Dai Jing-Cheng Cui Ru Li Yuan-Bo Li Yuan-Ming Zhou Xiao-Guo Bian Kang-Jie Wu Bing-Bing Zhang Kai-Fan Wang Xi-Sheng Li Yan 《中国科学:化学(英文版)》2022,65(4):753-761
Science China Chemistry - A light-induced, nickel-catalyzed three-component arylsulfonation of 1,3-enynes in the absence of photocatalyst is reported. This methodology exhibited mild conditions,... 相似文献
6.
Qi-Feng Zhou 《高分子科学》2022,40(1):1-1
The year 2022 marks the 40th anniversary of the Chinese Journal of Polymer Science(CJPS)—a true milestone to be celebrated!In the early stage of the reform and opening,there was an increasing demand for international academic communications.To facilitate these communications. 相似文献
7.
Hanghang Zhou Dr. Ying Luo Dr. Jun Xu Dr. Lidan Deng Prof. Dr. Zheng Wang Prof. Dr. Hong He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(68):e202202044
Cubic-like CaTaO2N photocatalysts with high crystallinity and uniform particle size were successfully prepared by the flux-assisted nitridation method. The growth of CaTaO2N single crystals under different synthesis conditions was systematically investigated to understand the effects of the crystallinity and optical property on photocatalytic performance of CO2 reduction. Moreover, the modification of CaTaO2N single crystals with core-shell Ni−Ag bicomponent cocatalyst by two-step decoration process gave a 2.4 times higher amount of CO evolution than the deposition of sole Ag cocatalyst, because of the synergistic effects of bicomponent cocatalyst on the interfacial electron transfer and surface catalytic process. This study provides a valuable way to construct high-crystalline photocatalysts with effective bicomponent cocatalyst for visible-light-driven CO2 reduction with H2O. 相似文献
8.
Guo Jiayun Ma Dongge Sun Fulin Zhuang Guilin Wang Qi Al-Enizi Abdullah M. Nafady Ayman Ma Shengqian 《中国科学:化学(英文版)》2022,65(9):1704-1709
Science China Chemistry - The heterojunction constructed of covalent organic frameworks (COFs) with adjustable structure and other photocatalysts has great potential in the field of photocatalysis.... 相似文献
9.
Nonlinear Dynamics - In this paper, the high-order coupled variable coefficient nonlinear Schrödinger equations is studied. The double-hump soliton solutions for the equations are obtained... 相似文献
10.
Hongjin Wang Tengfei Long Hao Zhang Meng Li Qi Sun Xin Zhai Lixin Sun 《Biomedical chromatography : BMC》2022,36(4):e5301
3,4-Difluorobenzyl(1-ethyl-5-(4-((4-hydroxypiperidin-1-yl)-methyl)thiazol-2-yl)-1H-indol-3-yl)carbamate (NAI59), a small molecule with outstanding therapeutic effectiveness to anti-pulmonary fibrosis, was developed as an autotaxin inhibitor candidate compound. To evaluate the pharmacokinetics and plasma protein binding of NAI59, a UPLC–MS/MS method was developed to quantify NAI59 in plasma and phosphate-buffered saline. The calibration curve linearity ranged from 9.95 to 1990.00 ng/mL in plasma. The accuracy was −6.8 to 5.9%, and the intra- and inter-day precision was within 15%. The matrix effect and recovery, as well as dilution integrity, were within the criteria. The chromatographic and mass spectrometric conditions were also feasible to determine phosphate-buffered saline samples, and it has been proved that this method exhibits good precision and accuracy in the range of 9.95–497.50 ng/mL in phosphate-buffered saline. This study is the first to determine the pharmacokinetics, absolute bioavailability, and plasma protein binding of NAI59 in rats using this established method. Therefore, the pharmacokinetic profiles of NAI59 showed a dose-dependent relationship after oral administration, and the absolute bioavailability in rats was 6.3%. In addition, the results of protein binding showed that the combining capacity of NAI59 with plasma protein attained 90% and increased with the increase in drug concentration. 相似文献