全文获取类型
收费全文 | 125154篇 |
免费 | 32577篇 |
国内免费 | 27708篇 |
专业分类
化学 | 65249篇 |
晶体学 | 1282篇 |
力学 | 6644篇 |
综合类 | 294篇 |
数学 | 12820篇 |
物理学 | 61843篇 |
无线电 | 37307篇 |
出版年
2024年 | 912篇 |
2023年 | 2254篇 |
2022年 | 2431篇 |
2021年 | 2632篇 |
2020年 | 3023篇 |
2019年 | 4064篇 |
2018年 | 3723篇 |
2017年 | 4447篇 |
2016年 | 5491篇 |
2015年 | 6159篇 |
2014年 | 6245篇 |
2013年 | 8474篇 |
2012年 | 9277篇 |
2011年 | 9913篇 |
2010年 | 12030篇 |
2009年 | 11872篇 |
2008年 | 6060篇 |
2007年 | 5400篇 |
2006年 | 5126篇 |
2005年 | 4830篇 |
2004年 | 5473篇 |
2003年 | 4447篇 |
2002年 | 4163篇 |
2001年 | 4150篇 |
2000年 | 3407篇 |
1999年 | 3583篇 |
1998年 | 3107篇 |
1997年 | 2769篇 |
1996年 | 3118篇 |
1995年 | 3371篇 |
1994年 | 3391篇 |
1993年 | 3424篇 |
1992年 | 2972篇 |
1991年 | 2594篇 |
1990年 | 2149篇 |
1989年 | 2148篇 |
1988年 | 1994篇 |
1987年 | 1242篇 |
1986年 | 1303篇 |
1985年 | 937篇 |
1984年 | 1009篇 |
1982年 | 927篇 |
1981年 | 756篇 |
1980年 | 782篇 |
1979年 | 535篇 |
1978年 | 534篇 |
1977年 | 634篇 |
1976年 | 1043篇 |
1972年 | 539篇 |
1971年 | 442篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Xiao Zhu Chen Yanxun Jiang Hongbo Hu Zhenzhen Lui John C. S. Min Geyong Dustdar Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of... 相似文献
2.
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was... 相似文献
3.
Potential Analysis - We establish some exact asymptotic results for a matching problem with respect to a family of beta distributions. Let X1,…,Xn be independent random variables with common... 相似文献
4.
Gürbüzbalaban Mert Ruszczyński Andrzej Zhu Landi 《Journal of Optimization Theory and Applications》2022,194(3):1014-1041
Journal of Optimization Theory and Applications - We consider a distributionally robust formulation of stochastic optimization problems arising in statistical learning, where robustness is with... 相似文献
5.
Hua Saixiang Zhu Huichao Wang Xiao Wu Mingyuan Wu Qingyun Liu Jiuyi Yang Jianjun Zhang Jianan 《Cellulose (London, England)》2022,29(13):7465-7475
Cellulose - Ultraviolet (UV) protective cotton fabric is a convenient and reliable way to protect human body from sunlight. Herein, a polymerizable UV-absorber,... 相似文献
6.
7.
Peng Li Haibin Jiang Ariel Barr Zhichu Ren Rui Gao Hua Wang Weiwei Fan Meifang Zhu Guiyin Xu Ju Li 《Advanced functional materials》2021,31(51):2105845
Mercury, lead, and cadmium are among the most toxic and carcinogenic heavy metal ions (HMIs), posing serious threats to the sustainability of aquatic ecosystems and public health. There is an urgent need to remove these ions from water by a cheap but green process. Traditional methods have insufficient removal efficiency and reusability. Structurally robust, large surface-area adsorbents functionalized with high-selectivity affinity to HMIs are attractive filter materials. Here, an adsorbent prepared by vulcanization of polyacrylonitrile (PAN), a nitrogen-rich polymer, is reported, giving rise to PAN-S nanoparticles with cyclic π-conjugated backbone and electronic conductivity. PAN-S can be coated on ultra-robust melamine (ML) foam by simple dipping and drying. In agreement with hard/soft acid/base theory, N- and S-containing soft Lewis bases have strong binding to Hg2+, Pb2+, Cu2+, and Cd2+, with extraordinary capture efficiency and performance stability. Furthermore, the used filters, when collected and electrochemically biased in a recycling bath, can release the HMIs into the bath and electrodeposit on the counter-electrode as metallic Hg0, Pb0, Cu0, and Cd0, and the PAN-S@ML filter can then be reused at least 6 times as new. The electronically conductive PAN-S@ML filter can be fabricated cheaply and holds promise for scale-up applications. 相似文献
8.
氢脆具有很强的微观组织敏感性,威胁着各类高强结构材料的安全服役.采用激光-电弧复合焊工艺对BS960E型高强钢进行焊接,并对接头在原位电化学充氢的条件下进行慢应变速率(10-5s-1)拉伸试验,结合微观组织和断裂特征进行分析并对接头的氢脆行为进行研究.结果 表明,焊接热循环所形成的富马氏体中的细晶区可以使接头表现出一定的氢脆敏感性,马氏体较大的氢扩散系数和较低的氢溶解度以及氢在晶界上的快速扩散是引起接头对氢脆敏感的主要原因,通过控制焊接工艺参数可抑制焊接热循环所引起的马氏体转变量,能够降低BS960E型高强钢激光-电弧复合焊接头的氢脆敏感性. 相似文献
9.
This study is to numerically test the interfacial instability of ferrofluid flow under the presence of a vacuum magnetic field. The ferrofluid parabolized stability equations(PSEs) are derived from the ferrofluid stability equations and the Rosensweig equations, and the characteristic values of the ferrofluid PSEs are given to describe the ellipticity of ferrofluid flow. Three numerical models representing specific cases considering with/without a vacuum magnetic field or viscosity are created to mathematically examine the interfacial instability by the computation of characteristic values. Numerical investigation shows strong dependence of the basic characteristic of ferrofluid Rayleigh-Taylor instability(RTI) on viscosity of ferrofluid and independence of the vacuum magnetic field.For the shock wave striking helium bubble, the magnetic field is not able to trigger the symmetry breaking of bubble but change the speed of the bubble movement. In the process of droplet formation from a submerged orifice, the collision between the droplet and the liquid surface causes symmetry breaking. Both the viscosity and the magnetic field exacerbate symmetry breaking. The computational results agree with the published experimental results. 相似文献
10.
Lili Hou Axel Olesund Shameel Thurakkal Xiaoyan Zhang Bo Albinsson 《Advanced functional materials》2021,31(47):2106198
Developing high-performance visible-to-UV photon upconversion systems based on triplet–triplet annihilation photon upconversion (TTA-UC) is highly desired, as it provides a potential approach for UV light-induced photosynthesis and photocatalysis. However, the quantum yield and spectral range of visible-to-UV TTA-UC based on nanocrystals (NCs) are still far from satisfactory. Here, three different sized CdS NCs are systematically investigated with triplet energy transfer to four mediators and four annihilators, thus substantially expanding the available materials for visible-to-UV TTA-UC. By improving the quality of CdS NCs, introducing the mediator via a direct mixing fashion, and matching the energy levels, a high TTA-UC quantum yield of 10.4% (out of a 50% maximum) is achieved in one case, which represents a record performance in TTA-UC based on NCs without doping. In another case, TTA-UC photons approaching 4 eV are observed, which is on par with the highest energies observed in optimized organic systems. Importantly, the in-depth investigation reveals that the direct mixing approach to introduce the mediator is a key factor that leads to close to unity efficiencies of triplet energy transfer, which ultimately governs the performance of NC-based TTA-UC systems. These findings provide guidelines for the design of high-performance TTA-UC systems toward solar energy harvesting. 相似文献