全文获取类型
收费全文 | 32516篇 |
免费 | 5649篇 |
国内免费 | 2895篇 |
专业分类
化学 | 5375篇 |
晶体学 | 587篇 |
力学 | 1894篇 |
综合类 | 578篇 |
数学 | 13715篇 |
物理学 | 18911篇 |
出版年
2024年 | 37篇 |
2023年 | 250篇 |
2022年 | 459篇 |
2021年 | 626篇 |
2020年 | 687篇 |
2019年 | 654篇 |
2018年 | 708篇 |
2017年 | 992篇 |
2016年 | 1125篇 |
2015年 | 943篇 |
2014年 | 1763篇 |
2013年 | 2454篇 |
2012年 | 1969篇 |
2011年 | 2132篇 |
2010年 | 1784篇 |
2009年 | 2197篇 |
2008年 | 2363篇 |
2007年 | 2334篇 |
2006年 | 2162篇 |
2005年 | 1998篇 |
2004年 | 1661篇 |
2003年 | 1517篇 |
2002年 | 1341篇 |
2001年 | 1248篇 |
2000年 | 1151篇 |
1999年 | 991篇 |
1998年 | 869篇 |
1997年 | 817篇 |
1996年 | 598篇 |
1995年 | 552篇 |
1994年 | 467篇 |
1993年 | 345篇 |
1992年 | 293篇 |
1991年 | 217篇 |
1990年 | 205篇 |
1989年 | 149篇 |
1988年 | 138篇 |
1987年 | 116篇 |
1986年 | 94篇 |
1985年 | 110篇 |
1984年 | 91篇 |
1983年 | 53篇 |
1982年 | 78篇 |
1981年 | 65篇 |
1980年 | 45篇 |
1979年 | 38篇 |
1978年 | 30篇 |
1977年 | 27篇 |
1976年 | 31篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
1.
2.
4.
Tapasi Chand Laxmikanta Khamari Deepak Chopra Saptarshi Mukherjee Manmohan Kapur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(43):e202200723
A one-step Rh-catalyzed site-selective ortho-C−H alkynylation of perylene as well as naphthalene mono- and diimides is reported. A single step regioselective access to ortho-C−H alkynylated derivatives of these ryleneimides not only increases the step economy of the ortho-functionalization on these dyes but also provides a quick access route towards highly functionalized dyes that have potential optoelectronic applications. Increased solubility of tetra(triisopropylsilyl)acetylenyl PDIs in organic solvents greatly enhances their utility for further derivatization. 相似文献
5.
对晶体硅(c-Si)太阳能电池而言, 氧化铝(AlOx)是一种广泛使用的钝化材料, 因为它具有优异的沉积保形性和良好的钝化质量. 为了确保AlOx发挥其良好的钝化效果, 在沉积后退火并氢化处理是必不可少的. 通过在AlOx薄膜上沉积氢化氮化硅(SiNx:H)来实现氢化, 利用开尔文探针力显微镜研究了在不同热处理和氢化作用下, AlOx/SiNx:H双层薄膜功函数的变化, 并基于沉积薄膜所含氢与固定电荷展开了讨论. 发现钝化质量和功函数之间有相关性, 影响因素包括薄膜厚度、氢化与热处理顺序. 相似文献
6.
通过引入参数,构造了一个全平面上的、含双曲函数的非齐次核函数。利用正切函数的有理分式展开,建立了最佳常数因子与正切函数高阶导数相关联的Hilbert型积分不等式。 作为应用,通过赋予参数不同的值,建立了一些有意义的特殊结果。 相似文献
7.
8.
《Wave Motion》2018
Large cable net structures have been widely applied in aerospace engineering due to the feature of light-weight, high packaging efficiency, and high thermal stability. Structural vibrations induced by a variety of disturbances are inevitable in the space environment, resulting in the requirement of effective vibration control strategies for large cable net structures. Since the large cable net structures have many closely spaced vibrational modes in the range of low frequencies, traditional modal based control may cause modal truncation and spillover problems. In this paper, a wave-based boundary control strategy is adopted and its effectiveness to control the vibration of cable net structures is investigated, by transfer function analysis and numerical methods. It is found that the structural vibration can be absolutely resisted by applying the wave-based boundary controllers onto all the exterior nodes, when disturbances come from the external boundaries of the cable net. Our results in this paper can provide a theoretical basis for the vibration control of large cable net structures. 相似文献
9.
Close‐Packed Two‐Dimensional Silver Nanoparticle Arrays: Quadrupolar and Dipolar Surface Plasmon Resonance Coupling 下载免费PDF全文
Sukang Yun Soonchang Hong Jesus A. I. Acapulco Jr. Ho Young Jang Songyi Ham Kyungeun Lee Prof. Seong Kyu Kim Prof. Sungho Park 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(16):6165-6172
Silver nanoparticles (NPs) ranging in size from 40 to 100 nm were prepared in high yield by using an improved seed‐mediated method. The homogeneous Ag NPs were used as building blocks for 2D assembled Ag NP arrays by using an oil/water interface. A close‐packed 2D array of Ag NPs was fabricated by using packing molecules (3‐mercaptopropyltrimethoxysilane) to control the interparticle spacing. The homogeneous 2D Ag NP array exhibited a strong quadrupolar cooperative plasmon mode resonance and a dipolar red‐shift relative to individual Ag NPs suspended in solution. A well‐arranged 2D Ag NP array was embedded in polydimethylsiloxane film and, with biaxial stretching to control the interparticle distance, concomitant variations of the quadrupolar and dipolar couplings were observed. As the interparticle distance increased, the intensity of the quadrupolar cooperative plasmon mode resonance decreased and dipolar coupling completely disappeared. The local electric field of the 2D Ag NP array was calculated by using finite difference time domain simulation and qualitatively showed agreement with the experimental measurements. 相似文献
10.
Multi-sensor data fusion is an evolving technology whereby data from multiple sensor inputs are processed and combined. The data derived from multiple sensors can, however, be uncertain, imperfect, and conflicting. The present study is undertaken to help contribute to the continuous search for viable approaches to overcome the problems associated with data conflict and imperfection. Sensor readings, represented by belief functions, have to be fused according to their corresponding weights. Previous studies have often estimated the weights of sensor readings based on a single criterion. Mono-criteria approaches for the assessment of sensor reading weights are, however, often unreliable and inadequate for the reflection of reality. Accordingly, this work opts for the use of a multi-criteria decision aid. A modified Analytical Hierarchy Process (AHP) that incorporates several criteria is proposed to determine the weights of a sensor reading set. The approach relies on the automation of pairwise comparisons to eliminate subjectivity and reduce inconsistency. It assesses the weight of each sensor reading, and fuses the weighed readings obtained using a modified average combination rule. The efficiency of this approach is evaluated in a target recognition context. Several tests, sensitivity analysis, and comparisons with other approaches available in the literature are described. 相似文献