全文获取类型
收费全文 | 24242篇 |
免费 | 4613篇 |
国内免费 | 3804篇 |
专业分类
化学 | 17305篇 |
晶体学 | 336篇 |
力学 | 1827篇 |
综合类 | 265篇 |
数学 | 2648篇 |
物理学 | 10278篇 |
出版年
2024年 | 75篇 |
2023年 | 470篇 |
2022年 | 833篇 |
2021年 | 799篇 |
2020年 | 985篇 |
2019年 | 886篇 |
2018年 | 821篇 |
2017年 | 746篇 |
2016年 | 1158篇 |
2015年 | 1207篇 |
2014年 | 1446篇 |
2013年 | 1793篇 |
2012年 | 2194篇 |
2011年 | 2259篇 |
2010年 | 1623篇 |
2009年 | 1504篇 |
2008年 | 1714篇 |
2007年 | 1515篇 |
2006年 | 1560篇 |
2005年 | 1307篇 |
2004年 | 1021篇 |
2003年 | 856篇 |
2002年 | 820篇 |
2001年 | 695篇 |
2000年 | 553篇 |
1999年 | 570篇 |
1998年 | 400篇 |
1997年 | 368篇 |
1996年 | 417篇 |
1995年 | 334篇 |
1994年 | 321篇 |
1993年 | 241篇 |
1992年 | 226篇 |
1991年 | 188篇 |
1990年 | 161篇 |
1989年 | 141篇 |
1988年 | 122篇 |
1987年 | 79篇 |
1986年 | 76篇 |
1985年 | 55篇 |
1984年 | 33篇 |
1983年 | 28篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1975年 | 1篇 |
1966年 | 1篇 |
1957年 | 7篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
902.
Ultrathin Mn Doped Ni-MOF Nanosheet Array for Highly Capacitive and Stable Asymmetric Supercapacitor
Dengchao Zheng Hao Wen Xun Sun Xin Guan Jie Zhang Wenli Tian Hao Feng Dr. Hongjing Wang Prof. Yadong Yao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(71):17149-17155
In this study, we demonstrate that an Mn-doped ultrathin Ni-MOF nanosheet array on nickel foam (Mn0.1-Ni-MOF/NF) serves as a highly capacitive and stable supercapacitor positive electrode. The Mn0.1-Ni-MOF/NF shows an areal capacity of 6.48 C cm−2 (specific capacity C: 1178 C g−1) at 2 mA cm−2 in 6.0 m KOH, outperforming most reported MOF-based materials. More importantly, it possesses excellent cycle stability to maintain 80.6 % capacity after 5000 cycles. An asymmetric supercapacitor device utilizing Mn0.1-Ni-MOF/NF as the positive electrode and activated carbon as the negative electrode attains a high energy density of 39.6 Wh kg−1 at 143.8 Wkg−1 power density with a capacitance retention of 83.6 % after 5000 cycles. 相似文献
903.
Zixin Chen Dr. Min Chen Dr. Yunfeng Cheng Prof. Toshiyuki Kowada Dr. Jinghang Xie Dr. Xianchuang Zheng Prof. Jianghong Rao 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3298-3305
The condensation reaction between 6-hydroxy-2-cyanobenzothiazole (CBT) and cysteine has been shown for various applications such as site-specific protein labelling and in vivo cancer imaging. This report further expands the substrate scope of this reaction by varying the substituents on aromatic nitriles and amino thiols and testing their reactivity and ability to form nanoparticles for cell imaging. The structure–activity relationship study leads to the identification of the minimum structural requirement for the macrocyclization and assembly process in forming nanoparticles. One of the scaffolds made of 2-pyrimidinecarbonitrile and cysteine joined by a benzyl linker was applied to design fluorescent probes for imaging caspase-3/7 and β-galactosidase activity in live cells. These results demonstrate the generality of this system for imaging hydrolytic enzymes. 相似文献
904.
Periodic Solutions of Third-order Differential Equations with Finite Delay in Vector-valued Functional Spaces 下载免费PDF全文
In this paper, we study the well-posedness of the third-order differential equation with finite delay(P_3): αu'"(t) + u"(t) = Au(t) + Bu'(t) + Fut +f(t)(t ∈ T := [0,2π]) with periodic boundary conditions u(0) = u(2π), u'(0) = u"(2π),u"(0)=u"(2π) in periodic Lebesgue-Bochner spaces Lp(T;X) and periodic Besov spaces B_(p,q)~s(T;X), where A and B are closed linear operators on a Banach space X satisfying D(A) ∩ D(B) ≠ {0}, α≠ 0 is a fixed constant and F is a bounded linear operator from Lp([-2π, 0]; X)(resp. Bp,qs([-2π, 0]; X)) into X, ut is given by ut(s) = u(t + s) when s ∈ [-2π,0]. Necessary and sufficient conditions for the Lp-well-posedness(resp. B_(p,q)~s-well-posedness)of(P_3) are given in the above two function spaces. We also give concrete examples that our abstract results may be applied. 相似文献
905.
906.
Chaonan Xie Qin Li Gang Han Huan Liu Jien Yang Jincheng Li 《Biomedical chromatography : BMC》2019,33(5)
Tricaine methanesulfonate is one of most commonly used anesthetics in fish during blood sampling, artificial propagation and long‐distance transportation. In this study, an accurate method for the quantitative determination of tricaine in fish samples by a stable isotope dilution assay coupled with high‐performance liquid chromatography–triple quadrupole mass spectrometry was developed. Tricaine‐D5 was synthesized and used as an isotopically labeled internal standard for the determination of tricaine. The analytical performance of the method was validated for tricaine determination in marine fish and freshwater fish. The determination of tricaine was linear in the range of 2.0–200.0 μg L?1. The limit of detection and limit of quantitation for fish muscle tissues were 1.0 and 4.0 μg kg?1, respectively. Good recoveries were obtained in the range of 92.08–97.50%. The inter‐ and intra‐assay relative standard deviations (RSD values) were investigated, and the values were 0.39–3.01 and 0.85–2.77%, respectively. The values of CCα and CCβ were 10.21–10.43 and 10.42–10.87 μg kg?1, respectively. The clearance of MS‐222 from grass carp was further studied using our method. The results demonstrate that MS‐222 could be well absorbed and rapidly eliminated after bath administration. 相似文献
907.
Acta Mathematicae Applicatae Sinica, English Series - The generalized estimating equations(GEE) approach is perhaps one of the most widely used methods for longitudinal data analysis. While the GEE... 相似文献
908.
Qing Liu Yibin Liu Hua Zheng Chunmei Li Yi Zhang Qiuyu Zhang 《Journal of polymer science. Part A, Polymer chemistry》2020,58(8):1092-1104
Thermoset polymer elastomers that are capable of autonomous repairability upon physical damage at ambient temperature are highly desirable because of their thermal and environmental resistance, outstanding mechanical toughness and stability. To aim at this goal, we demonstrated that tris(diethylamino)phosphine was initially proven as an efficient catalyst for the aliphatic disulfide exchange at mild condition. By making use of the aliphatic disulfide bond reshuffling and elasticity of polyurethane elastomers, the inherently cross-linked polysulfide-based poly(thiourethane-urethane) elastomers were prepared and exhibited the ability to mend without extrinsic stimuli in the presence of phosphorus catalyst at room temperature after artificially damaged. The self-healing efficiency via the mechanical recovery approach was investigated to be mainly dependent upon the cross-linking density of polysulfide and hard segments chemistry, which in turns determined the molecular chain diffusion and reshuffling that was corroborated by the stress-relaxation study. The thermoset elastomer based on asymmetric diisocynate showed a maximum self-healing efficiency of 85.6% compared to 71.6% for the elastomer with symmetric monomer building blocks. The self-healable polymer was confirmed to be recyclable and reprocessable through a cut-compression processing cycle under a quite mild pressure and temperature thanks to the disulfide bond reshuffling. Meanwhile, the recycled thermoset elastomer well maintained the mechanical properties to its original material. 相似文献
909.
Li Xiang Yao Dongbao Zhou Junxiang Zhou Xiang Sun Xianbao Wei Bing Li Chengxu Zheng Bin Liang Haojun 《中国科学:化学(英文版)》2020,63(1):92-98
Signal amplification is an important issue in DNA nanotechnology and molecular diagnostics. In this work, we report a strategy for the catalytic self-assembly of spherical nucleic acids(SNAs) programmed by two-layer cascaded DNA circuits through integrating an entropy-driven catalytic network, a catalytic hairpin assembly circuit, and a facile SNA assembly-based reporter system. This integrated system could implement ~100,000-fold signal amplification in the presence of 1 p M of input target.Possessing powerful amplification ability of nucleic acid signal, our strategy should be of great potential in fabricating more robust dynamic networks to be applied for signal transduction, DNA computing, and nucleic acid-based diagnostics. 相似文献
910.