全文获取类型
收费全文 | 29192篇 |
免费 | 4776篇 |
国内免费 | 3483篇 |
专业分类
化学 | 21395篇 |
晶体学 | 383篇 |
力学 | 1783篇 |
综合类 | 265篇 |
数学 | 3300篇 |
物理学 | 10325篇 |
出版年
2024年 | 21篇 |
2023年 | 509篇 |
2022年 | 582篇 |
2021年 | 893篇 |
2020年 | 1113篇 |
2019年 | 1059篇 |
2018年 | 908篇 |
2017年 | 860篇 |
2016年 | 1313篇 |
2015年 | 1321篇 |
2014年 | 1583篇 |
2013年 | 2169篇 |
2012年 | 2565篇 |
2011年 | 2719篇 |
2010年 | 1911篇 |
2009年 | 1706篇 |
2008年 | 1941篇 |
2007年 | 1716篇 |
2006年 | 1640篇 |
2005年 | 1472篇 |
2004年 | 1139篇 |
2003年 | 976篇 |
2002年 | 1025篇 |
2001年 | 718篇 |
2000年 | 610篇 |
1999年 | 608篇 |
1998年 | 515篇 |
1997年 | 427篇 |
1996年 | 449篇 |
1995年 | 433篇 |
1994年 | 351篇 |
1993年 | 323篇 |
1992年 | 284篇 |
1991年 | 269篇 |
1990年 | 262篇 |
1989年 | 205篇 |
1988年 | 176篇 |
1987年 | 132篇 |
1986年 | 117篇 |
1985年 | 116篇 |
1984年 | 60篇 |
1983年 | 60篇 |
1982年 | 44篇 |
1981年 | 37篇 |
1980年 | 22篇 |
1979年 | 17篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1974年 | 8篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results. 相似文献
23.
Zhengcheng Wang Shangyan Zhou Wei Liao Qian Zhou Meida Chen Jin Long Prof. Qingmei Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202201987
The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt1Fe3@NC/MWCNTs catalyst with moderate Fe3+ feeding content (0.86 mA/mgPt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mgPt). Furthermore, the CO oxidation initial potential of Pt1Fe3@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt1Fe3@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field. 相似文献
24.
Meihua Shen Dr. Xinpeng Zhao Dr. Lu Han Nanxi Jin Prof. Song Liu Prof. Tao Jia Prof. Zhijun Chen Prof. Xiuhua Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202104137
Solar-driven interfacial vaporization by localizing solar-thermal energy conversion to the air−water interface has attracted tremendous attention. In the process of converting solar energy into heat energy, photothermal materials play an essential role. Herein, a flexible solar-thermal material di-cyan substituted 5,12-dibutylquinacridone (DCN−4CQA)@Paper was developed by coating photothermal quinacridone derivatives on the cellulose paper. The DCN−4CQA@Paper combines desired chemical and physical properties, broadband light-absorbing, and shape-conforming abilities that render efficient photothermic vaporization. Notably, synergetic coupling of solar-steam and solar-electricity technologies by integrating DCN−4CQA@Paper and the thermoelectric devices is realized without trade-offs, highlighting the practical consideration toward more impactful solar heat exploitation. Such solar distillation and low-grade heat-to-electricity generation functions can provide potential opportunities for fresh water and electricity supply in off-grid or remote areas. 相似文献
25.
Science China Chemistry - 相似文献
26.
Nonlinear Dynamics - In this paper, we study a delayed diffusive predator–prey model with nonlocal competition in prey and habitat complexity. The local stability of coexisting equilibrium is... 相似文献
27.
将TiNi基记忆合金薄膜与光纤相结合可制成智能化、集成化且成本经济的微机电系统和微传感器件.本文采用磁控溅射法在二氧化硅光纤基底上制备TiNi记忆合金薄膜,系统讨论了溅射工艺参数以及后续退火处理对薄膜质量的影响.采用自研制光纤镀膜掩膜装置在直径为125μm的光纤圆周表面上形成均匀薄膜.实验表明:在靶基距、背底真空度、Ar气流量和溅射时间一定的条件下,溅射功率存在最佳值;溅射压强较大时,薄膜沉积速率较低,但薄膜表面粗糙度较小.进行退火处理后,薄膜形成较良好的晶体结构,Ti49.09Ni50.91薄膜中马氏体B19′相和奥氏体B2相共存,但以B19′为主.根据本文研究结果,在玻璃光纤基底上制备高质量的TiNi基记忆合金薄膜是可实现的,本工作为下一步研制微机电系统和微型传感器做了基础准备. 相似文献
28.
Crystallography Reports - A novel 3D metal coordination polymer, {[Na4(µ2-H2O)(DMF)2(BCT)2]?DMF}n (I) (DMF = N,N-dimethylformamide, H2BCT =... 相似文献
29.
Nonlinear Dynamics - To describe the particular mechanical behaviors of beams with both uniform and non-uniform cross sections, such as the bidirectional bending, torsion-bending coupling, the... 相似文献
30.
The Ramanujan Journal - In this paper we investigate several infinite products with vanishing Taylor coefficients in arithmetic progressions. These infinite products are closely related to... 相似文献