全文获取类型
收费全文 | 94760篇 |
免费 | 10033篇 |
国内免费 | 8837篇 |
专业分类
化学 | 42029篇 |
晶体学 | 647篇 |
力学 | 3623篇 |
综合类 | 375篇 |
数学 | 7220篇 |
物理学 | 23160篇 |
综合类 | 36576篇 |
出版年
2024年 | 363篇 |
2023年 | 1448篇 |
2022年 | 2626篇 |
2021年 | 2744篇 |
2020年 | 2670篇 |
2019年 | 2332篇 |
2018年 | 2114篇 |
2017年 | 2182篇 |
2016年 | 3085篇 |
2015年 | 3471篇 |
2014年 | 4175篇 |
2013年 | 5074篇 |
2012年 | 6008篇 |
2011年 | 7673篇 |
2010年 | 5092篇 |
2009年 | 5282篇 |
2008年 | 4815篇 |
2007年 | 4444篇 |
2006年 | 3894篇 |
2005年 | 3816篇 |
2004年 | 5228篇 |
2003年 | 3777篇 |
2002年 | 3232篇 |
2001年 | 2499篇 |
2000年 | 1947篇 |
1999年 | 2694篇 |
1998年 | 2564篇 |
1997年 | 2570篇 |
1996年 | 1999篇 |
1995年 | 1717篇 |
1994年 | 1758篇 |
1993年 | 2108篇 |
1992年 | 1705篇 |
1991年 | 1558篇 |
1990年 | 1375篇 |
1989年 | 1104篇 |
1988年 | 738篇 |
1987年 | 525篇 |
1986年 | 370篇 |
1985年 | 224篇 |
1984年 | 118篇 |
1983年 | 109篇 |
1982年 | 68篇 |
1981年 | 42篇 |
1980年 | 36篇 |
1979年 | 22篇 |
1977年 | 22篇 |
1976年 | 23篇 |
1975年 | 22篇 |
1972年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Zhen Xi 《中国科学:化学(英文版)》2015,(3):434-435
Redox-based post-translational modification of protein thiols has become an attractive strategy in cellular homeostasis and cell signaling.Due to the reductive end of the redox buffer network,the vicinal dithiol-containing proteins(VDPs)maintains an appropriate oxidation-reduction state of proteins through the reversible transformation from vicinal dithiols to disulfide,which is responsible for a variety of 相似文献
22.
23.
我国初步建立了财政性科技经费监管体系,但是在监督主体、监督制度等方面还存在缺陷,科技经费监督出现诸多问题。建立要加强宏观层面的统筹规划,建立由政府、承担单位和外部主体上下联动、横向联合的立体监督体系。 相似文献
24.
25.
以205/55R16乘用车轮胎为研究对象,采用计算流体动力学建立了考虑胎面花纹变形的轮胎滑水分析模型;以气-液二相流数值模型分析了轮胎的滑水性能,并将临界滑水速度仿真值与NASA滑水速度预测值及轮胎发生滑水时力平衡下的速度进行对比.在此基础上,引入仿生减阻理念,研究了夹角为60°、高度为0.6mm的仿生对称V形结构对花纹沟排水量和水流阻力的影响,并将其结构特征信息等效移植到接地区轮胎花纹沟底,进行了仿生花纹轮胎的滑水性能分析.结果表明:所建滑水分析模型可用来分析轮胎滑水时的流体运动特性;相对原花纹轮胎,仿生非光滑花纹沟轮胎通过提高接地区花纹沟内水流速度,降低了胎面动水压力,提高了临界滑水速度. 相似文献
26.
Lijuan Shen Li Li Sheng Lu Xiaohan Zhang Jie Liu Junlin An Guojun Zhang Bo Wu Fei Wang 《中国颗粒学报》2015,(3):10-15
We conducted measurements of black carbon(BC) aerosol in Jiaxing,China during autumn from September 26 to November 30,2013.We investigated temporal and diurnal variations of BC,and its correlations with meteorological parameters and other major pollutants.Results showed that hourly mass concentrations of BC ranged from 0.2 to 22.0 μg/m3,with an average of 5.1 μg/m3.The diurnai variation of BC exhibited a bimodal distribution,with peaks at 07:00 and 18:00.The morning peak was larger than the evening peak.The mass percentages of BC in PM2.5 and PM10 were 7.1%and 4.8%,respectively.The absorption coefficient of BC was calculated to be 44.4 Mm-1,which accounted for 11.1%of the total aerosol extinction.BC was mainly emitted from local sources in southwestern Jiaxing where BC concentrations were generally greater than 11 μg/m3 during the measurement period.Correlation analysis indicated that the main sources of BC were motor vehicle exhaust,and domestic and industrial combustion. 相似文献
27.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
28.
29.
We investigate terahertz radiation(T-rays) from a pentacene organic diode at room temperature. The quantum chemistry calculation for frequency-related Huang–Rhys factor of pentacene is also carried out. The results demonstrate that the T-rays can come from a bending vibration of pentacene skeleton after the energy of pentacene exciton transferring to the vibrational excited state via electron–phonon coupling. Frequency and natural bond orbital analytics of pentacene and its derivatives are performed in order to explain the result and develop new materials to get higher emission. This work provides a new way to produce T-rays with a simple device at room temperature. 相似文献
30.
A nanomaterials-based novel molecular beacon has attracted growing attentions in fluorescent assays as many nanomaterials possess excellent quenching efficiency. In this work, a gold-based nanobeacon probe was established to detect organophosphorus pesticides for the first time. The constructed gold-based nanobeacon acted as a signal indicator and could display the decreasing of the intensity in the presence of targets, which competitively bound to single strand DNA. To achieve a high sensitive probe, some parameters including solution pH, temperature and reaction time were investigated and optimized. The gold-based nanobeacon probe assay was proved to be rapid and sensitive to achieve a detection limit of 0.035 μM for isocarbophos, 0.134 μM for profenofos, 0.384 μM for phorate and 2.35 μM for omethoate, respectively. The prepared nanobeacon effectively reduced the background and improved the detection sensitivity and selectivity. The probe is stable, easy to operate and does not need sophisticated instruments. These features makes the probe feasible for screening trace organophosphorus pesticides in real samples. 相似文献