全文获取类型
收费全文 | 5711篇 |
免费 | 1147篇 |
国内免费 | 828篇 |
专业分类
化学 | 2784篇 |
晶体学 | 70篇 |
力学 | 278篇 |
综合类 | 125篇 |
数学 | 611篇 |
物理学 | 1415篇 |
无线电 | 2403篇 |
出版年
2024年 | 27篇 |
2023年 | 129篇 |
2022年 | 230篇 |
2021年 | 273篇 |
2020年 | 248篇 |
2019年 | 239篇 |
2018年 | 215篇 |
2017年 | 273篇 |
2016年 | 261篇 |
2015年 | 339篇 |
2014年 | 386篇 |
2013年 | 448篇 |
2012年 | 504篇 |
2011年 | 467篇 |
2010年 | 429篇 |
2009年 | 437篇 |
2008年 | 439篇 |
2007年 | 404篇 |
2006年 | 336篇 |
2005年 | 282篇 |
2004年 | 172篇 |
2003年 | 142篇 |
2002年 | 139篇 |
2001年 | 127篇 |
2000年 | 135篇 |
1999年 | 95篇 |
1998年 | 59篇 |
1997年 | 53篇 |
1996年 | 51篇 |
1995年 | 38篇 |
1994年 | 26篇 |
1993年 | 30篇 |
1992年 | 33篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 22篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 18篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有7686条查询结果,搜索用时 406 毫秒
81.
Borole Abhijeet P. Sublette Kerry L. Fisher J. Berton Raterman Kevin T. Kemp Nan P. McInerney Michael J. 《Applied biochemistry and biotechnology》1996,57(1):817-826
Applied Biochemistry and Biotechnology - The addition of gas condensate hydrocarbons to saturated soil from a gas production site stimulated sulfate reduction under anaerobic and oxygen-limiting... 相似文献
82.
二水草酸锌脱水的热分解动力学研究 总被引:10,自引:0,他引:10
提出一种多升温速率-等温法确定机理函数g(α)的新方法;并用迭代的等转化率法求出较为可靠的活化能Ea;在Ea和g(α)的基础上计算出指前因子A.用该法对二水草酸锌(ZnC2O4•2H2O)脱水反应的热分解动力学三因子进行了求算,得出Ea为87.22 kJ•mol-1, A为4.2120×108~7.2328×108 s-1;以及随机成核和随后生长型机理函数Am(Avrami-Erofeer),其积分形式g(α)=[-ln(1-α)] 1/m和微分形式f(α)=m(1-α)•[-ln(1-α)](1-1/m),调节因子m=1.85~2.00. 相似文献
83.
SHI Wei-Feng JIANG Nan WANG Jian-Bo 《有机化学》2003,23(Z1):17-17
In the process of preparing α-diazo carbonyl compound 2 by imidation of 1, we unexpectedly observed a direct conversion of the hydroxyl group into trichloroacetylamino group. In this presentation, we report this unprecedented reaction, as well as the Rh2(OAc)4-catalyzed reaction of the resulting β-(trichloroacetyl)amino β-diazo carbonylcompounds 3. [ 1] 相似文献
84.
民参军是军民融合的重要组成内容,政府支持对于民参军的顺利进行发挥着关键作用。本文通过建立军民融合背景下的地方政府支持与民企参军行为的演化博弈模型,考察了参与者的决策演化过程,分析了参与者的进化稳定策略及影响因素。研究表明,增加地方政府对民企的资金奖励、加大民企参军税收优惠、民企资金收益率的提升,以及积极参军成本的降低,会使民企策略选择向积极参军方向演化,但却使地方政府行为向弱力度支持策略演化;而提升中央政府对地方政府的资金补助,降低地方政府支持民企积极参军的服务成本,不仅促使民企选择积极参军策略,还能促使地方政府选择强力度支持策略。最后,对模型结果进行算例分析,验证了结论的合理性。研究结果可以为当前民参军实践提供一定的理论指导。 相似文献
85.
随着调谐激光吸收光谱(tunable laser absorption spectroscopy, TLAS)技术在气体检测中的应用越来越广泛,二次谐波信号的质量与检测参数紧密相关,因而分析检测参数的优化方法很有意义。本文根据谱线预处理中的滤波参数、系统采样时间、锁相放大器的时间常数对信号的影响以及参数间的联系,总结检测参数的选取规律。根据滤波原理和不同浓度下信号的均方根误差(root mean squared error,RMSE)值选择合适的滤波阶数和窗宽。选择信噪比(signal-to-noise ratio,SNR)、RMSE、信号与噪声频域幅度之比(ratio of amplitude in frequency domain of signal to noise,fSNR)3种评价指标的曲线变化趋势进行时频分析,得到最佳采样周期数为30,结合实验系统具体参数可计算最佳采样时间。通过信号主频带与截止频率的关系和滤波效果选择合适的时间常数。综合分析3个检测参数并总结选取方法,可提高二次谐波信号的质量。本文提出的参数选取方法对提高二次谐波在实际应用中的准确度有... 相似文献
86.
With the expansion of smart grid and Internet of things (IoT) technology, edge computing has a wide variety of applications in these domains. The criteria for real-time monitoring and accuracy are particularly high in the field of online real-time monitoring of electricity lines. Based on edge technology, high-quality real-time monitoring can be performed for transmission lines using image processing techniques. Therefore, we propose an image denoising method, which can learn clean images using a stream-based generative model. The stream model uses a two-stage approach in the network to handle the different training periods of denoising separately. Experimental results show that the proposed method has good denoising performance. 相似文献
87.
88.
Zihao Zhang Zirong He Nan Wang Fengmei Wang Chongyu Du Jiafeng Ruan Qin Li Dalin Sun Fang Fang Fei Wang 《Advanced functional materials》2023,33(27):2214648
Rechargeable aqueous zinc batteries are promising energy storage devices because of their low cost, high safety, and high energy density. However, their performance is plagued by the unsatisfied cyclability due to the dendrite growth and hydrogen evolution reaction (HER) at the Zn anode. Herein, it is demonstrated that the concentrated hybrid aqueous/non-aqueous ZnCl2 electrolytes constitute a peculiar chemical environment for not only the Zn-ions but also water molecules. The high concentration of chloride ions substitutes the H2O molecular in the solvation structure of Zn2+, while the acetonitrile further interacts with H2O to decrease its activity. The hybrid electrolytes both inhibit the dendrite formation and HER, enabling an ultrahigh average Coulombic efficiency of 99.9% in the Zn||Cu half-cell and a highly reversible Zn plating/stripping with a low overpotential of 21 mV. Using this hybrid electrolyte, the Zn||polytriphenylamine (PTPAn) full cell deliveres a high discharge capacity of 110 mAh g−1, a high power density of 9200 W kg−1 at 100 °C and maintains 85% of the capacity for over 6000 cycles at 10 °C. This study provides a deep understanding between the solvation structure and columbic efficiency of Zn anode, thus inspiring the development for stable Zn batteries. 相似文献
89.
Ruyi Fang Yutao Li Nan Wu Biyi Xu Yijie Liu Arumugam Manthiram John B. Goodenough 《Advanced functional materials》2023,33(6):2211229
Inorganic/organic composite polymer electrolytes (CPEs) with good flexibility and electrode contact have been pursued for solid−state sodium-metal batteries. However, the application of CPEs for high energy density solid−state sodium-metal batteries is still limited by the low Na+ conductivity, large thickness, and low ion transference number. Herein, an ultra-thin single-particle-layer (UTSPL) composite polymer electrolyte membrane with a thickness of ≈20 µm straddled by a sodium beta−alumina ceramic electrolyte (SBACE) is presented. A ceramic Na+-ion electrolyte that bridges or percolates across an ultra-thin and flexible polymer membrane provides: 1) the strength and flexibility from the polymer membrane, 2) excellent electrolyte/electrode interfacial contact, and 3) a percolation path for Na+-ion transfer. Owing to this novel design, the obtained UTSPL-35SBACE membrane exhibits a high Na+-ion conductivity of 0.19 mS cm−1 and a transference number of 0.91 at room temperature, contributing to long−term cycling stability of symmetric sodium cells with a small overpotential. The assembled quasi-solid-state cell with the as−prepared UTSPL-35SBACE membrane displays superior cycling performance with a discharge capacity of 105 mAh g−1 at 0.5 °C rate after 100 cycles and excellent rate performance (82 mAh g−1 at 5 °C rate) at room temperature with the potassium manganese hexacyanoferrate (KMHCF)@CNTs/CNFs cathode, where KMHCF refers to potassium manganese hexacyanoferrate. 相似文献
90.