全文获取类型
收费全文 | 63204篇 |
免费 | 12269篇 |
国内免费 | 16331篇 |
专业分类
化学 | 48089篇 |
晶体学 | 1753篇 |
力学 | 3915篇 |
综合类 | 1857篇 |
数学 | 8868篇 |
物理学 | 27322篇 |
出版年
2024年 | 120篇 |
2023年 | 948篇 |
2022年 | 1865篇 |
2021年 | 2306篇 |
2020年 | 2461篇 |
2019年 | 2430篇 |
2018年 | 2157篇 |
2017年 | 2615篇 |
2016年 | 2644篇 |
2015年 | 3227篇 |
2014年 | 3902篇 |
2013年 | 5016篇 |
2012年 | 5453篇 |
2011年 | 5880篇 |
2010年 | 4966篇 |
2009年 | 5187篇 |
2008年 | 5495篇 |
2007年 | 4978篇 |
2006年 | 4900篇 |
2005年 | 4083篇 |
2004年 | 3147篇 |
2003年 | 2294篇 |
2002年 | 2235篇 |
2001年 | 2314篇 |
2000年 | 2361篇 |
1999年 | 1532篇 |
1998年 | 910篇 |
1997年 | 765篇 |
1996年 | 674篇 |
1995年 | 595篇 |
1994年 | 591篇 |
1993年 | 548篇 |
1992年 | 457篇 |
1991年 | 370篇 |
1990年 | 365篇 |
1989年 | 351篇 |
1988年 | 279篇 |
1987年 | 226篇 |
1986年 | 228篇 |
1985年 | 152篇 |
1984年 | 142篇 |
1983年 | 125篇 |
1982年 | 92篇 |
1981年 | 90篇 |
1980年 | 70篇 |
1979年 | 58篇 |
1978年 | 33篇 |
1977年 | 17篇 |
1965年 | 21篇 |
1959年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
11.
12.
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
13.
14.
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
15.
低维硅锗材料是制备纳米电子器件的重要候选材料,是研发高效率、低能耗和超高速新一代纳米电子器件的基础材料之一,有着潜在的应用价值。采用密度泛函紧束缚方法分别对厚度相同、宽度在0.272 nm~0.554 nm之间的硅纳米线和宽度在0.283 nm~0.567 nm之间的锗纳米线的原子排布和电荷分布进行了计算研究。硅、锗纳米线宽度的改变使原子排布,纳米线的原子间键长和键角发生明显改变。纳米线表层结构的改变对各层内的电荷分布产生重要影响。纳米线中各原子的电荷转移量与该原子在表层内的位置相关。纳米线的尺寸和表层内原子排列结构对体系的稳定性产生重要影响。 相似文献
16.
Mathematical Programming - Convergence analysis of accelerated first-order methods for convex optimization problems are developed from the point of view of ordinary differential equation solvers. A... 相似文献
17.
In this article,we study the initial boundary value problem of coupled semi-linear degenerate parabolic equations with a singular potential term on manifolds with corner singularities.Firstly,we introduce the corner type weighted p-Sobolev spaces and the weighted corner type Sobolev inequality,the Poincare′inequality,and the Hardy inequality.Then,by using the potential well method and the inequality mentioned above,we obtain an existence theorem of global solutions with exponential decay and show the blow-up in finite time of solutions for both cases with low initial energy and critical initial energy.Significantly,the relation between the above two phenomena is derived as a sharp condition.Moreover,we show that the global existence also holds for the case of a potential well family. 相似文献
18.
Nonlinear Dynamics - This paper investigates the guaranteed cost positive consensus for linear multi-agent systems (MASs) with multiple time-varying delays and switching topologies. First,... 相似文献
19.
Bingjie Chen Dr. Lianhai Zu Dr. Yao Liu Dr. Ruijing Meng Yutong Feng Prof. Chengxin Peng Feng Zhu Tianzi Hao Jiajia Ru Prof. Yonggang Wang Prof. Jinhu Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3161-3166
Incorporating nanoscale Si into a carbon matrix with high dispersity is desirable for the preparation of lithium-ion batteries (LIBs) but remains challenging. A space-confined catalytic strategy is proposed for direct superassembly of Si nanodots within a carbon (Si NDs⊂C) framework by copyrolysis of triphenyltin hydride (TPT) and diphenylsilane (DPS), where Sn atomic clusters created from TPT pyrolysis serve as the catalyst for DPS pyrolysis and Si catalytic growth. The use of Sn atomic cluster catalysts alters the reaction pathway to avoid SiC generation and enable formation of Si NDs with reduced dimensions. A typical Si NDs⊂C framework demonstrates a remarkable comprehensive performance comparable to other Si-based high-performance half LIBs, and higher energy densities compared to commercial full LIBs, as a consequence of the high dispersity of Si NDs with low lithiation stress. Supported by mechanic simulations, this study paves the way for construction of Si/C composites suitable for applications in future energy technologies. 相似文献
20.
Design of diamond-shape photonic crystal fiber polarization filter based on surface plasma resonance effect 下载免费PDF全文
A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber(PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio(ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems. 相似文献