全文获取类型
收费全文 | 9994篇 |
免费 | 2166篇 |
国内免费 | 1422篇 |
专业分类
化学 | 7475篇 |
晶体学 | 177篇 |
力学 | 601篇 |
综合类 | 118篇 |
数学 | 1032篇 |
物理学 | 4179篇 |
出版年
2024年 | 53篇 |
2023年 | 302篇 |
2022年 | 492篇 |
2021年 | 602篇 |
2020年 | 593篇 |
2019年 | 562篇 |
2018年 | 466篇 |
2017年 | 419篇 |
2016年 | 553篇 |
2015年 | 678篇 |
2014年 | 733篇 |
2013年 | 847篇 |
2012年 | 1007篇 |
2011年 | 956篇 |
2010年 | 657篇 |
2009年 | 695篇 |
2008年 | 729篇 |
2007年 | 588篇 |
2006年 | 537篇 |
2005年 | 413篇 |
2004年 | 306篇 |
2003年 | 218篇 |
2002年 | 215篇 |
2001年 | 155篇 |
2000年 | 146篇 |
1999年 | 113篇 |
1998年 | 97篇 |
1997年 | 70篇 |
1996年 | 63篇 |
1995年 | 47篇 |
1994年 | 39篇 |
1993年 | 42篇 |
1992年 | 33篇 |
1991年 | 18篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1976年 | 2篇 |
1971年 | 2篇 |
1966年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
The Role of Processing Solvent on Morphology Optimization for Slot-Die Printed Organic Photovoltaics
Wang Lei Zhan Jun-Zhe Zhong Wen-Kai Zhu Lei Zhou Guan-Qing Hao Tian-Yu Zou Ye-Cheng Wang Zhen-Hua Wei Gang Zhang Yong-Ming Liu Feng 《高分子科学》2023,41(6):842-850
Chinese Journal of Polymer Science - The morphology manipulation of the active layers is important for improving the performance of organic photovoltaics (OPVs). The choice of processing solvent... 相似文献
142.
Wen‐Hao Chen Chang‐Ri Han Yang Hui Da‐Shuai Zhang Xin‐Ming Song Guang‐Ying Chen Xiao‐Ping Song 《Helvetica chimica acta》2015,98(5):724-730
Two new eremophilane‐type sesquiterpenoids, 1α‐hydroxyeremophila‐6,9,11‐trien‐8‐one ( 1 ), 4α‐hydroxyeremophila‐1,9‐diene‐3,8‐dione ( 2 ), and a new friedelane‐type triterpenoid, friedelane‐3α,16β‐diol ( 4 ), along with six known terpenoids, 3 and 5 – 9 , have been isolated from the stems of Drypetes congestiflora. Their structures and relative configurations were elucidated on the basis of detailed spectroscopic analyses and by comparison of their NMR data with those reported in the literature. All of the compounds, 1 – 9 , were isolated for the first time from this species. Compound 3 exhibited moderate cytotoxic activities against the A549 and B16F10 cell lines. 相似文献
143.
Yizhen Tang Jingyu Sun Xiujuan Jia Hao Sun Xiumei Pan Rongshun Wang 《Journal of computational chemistry》2010,31(7):1520-1527
The reaction of N2H4 with OH has been investigated by quantum chemical methods. The results show that hydrogen abstraction mechanism is more feasible than substitution mechanism thermodynamically. The calculated rate constants agree with the available experimental data. The calculated results show that the variational effect is small at lower temperature region, while it becomes significant at higher temperature region. On the other hand, the small‐curvature tunneling effect may play an important role in the temperature range 220?3000 K. Moreover, the calculated rate constants show negative temperature dependence at the temperatures below 500 K, which is in accordance with Vaghjiani's report that slightly negative temperature dependence is found over the temperature range of 258?637 K. The mechanism of the major product (N2H3) with OH has also been investigated theoretically to understand the title reaction thoroughly. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
144.
Yanfang Shen Tianying Xiong Hao Du Huazi Jin Jianku Shang Ke Yang 《Journal of Sol-Gel Science and Technology》2009,50(1):98-102
P, N, and Mo ternary co-doped nano TiO2 photocatalysts ((P, N, Mo)-TiO2) were prepared by a single step sol–gel method, which show much enhanced photocatalytic activities over Mo-TiO2, (P, N)-TiO2, un-doped TiO2 and Degussa P25 under visible light irradiation. The degradation rate of 0.72Mo–P-TiO2 is as high as 65.3%, which is about 6.7 times of that of Degussa P25. Possible reasons for the improvement of photocatalytic
activities were analyzed. 相似文献
145.
A general stereoselective synthetic route to 5-substituted and 5,8-disubstituted indolizidine alkaloids has been developed starting from commercially available L-proline. (-)-Indolizidines 209D and 209B were efficiently synthesized in 9.8% and 14.8% overall yields in seven and five-step reactions from readily available aldehyde 3 and ketone 10, respectively. The key steps of this synthesis involve a substrate-induced asymmetric addition of ethyl lithiopropiolate to aldehyde 3 or methyl ketone 10, and a two-step one-pot hydrogenation/cyclization sequence to construct the bicyclic skeleton. 相似文献
146.
Lin‐Bao Zhang Xin‐Qi Hao Zhan‐Jiang Liu Xin‐Xiang Zheng Shou‐Kun Zhang Jun‐Long Niu Mao‐Ping Song 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(34):10150-10153
A highly efficient cobalt(II)‐catalyzed alkynylation/annulation of terminal alkynes assisted by an N,O‐bidentate directing group is described. This protocol is characterized by wide substrate scope utilizing cheap cobalt catalysts, and offers a new approach to 3‐methyleneisoindolin‐1‐one, which can be converted into an oxadiazine salt in one step. Moreover, the directing group could be removed in three steps. 相似文献
147.
148.
The morphological transformation process of gold nanorods (Au-NRs) resulting from the reaction between tetracycline and iodine
was monitored by the plasmon resonance absorption (PRA) spectra and the scanning electron microscope (SEM) images. It was
found that iodine could fuse Au-NRs into sphericity with the lower aspect ratio and blue shift of the longitudinal PRA band.
It was found, however, that the presence of tetracycline, since it can react with I2, decreases the effective concentration of I2 and its fusion effect on Au-NRs. As a result, the longitudinal PRA of Au-NRs shifts to longer wavelength linearly with increasing
the concentration of tetracycline. With that, tetracycline can be detected in the range of 5.0×10∮5- 5.0×10−4 mol·L−1, with a limit of determination (LOD) of 2.4×10−6 mol·L−1 (3σ). Most foreign substances in the samples did not interfere in the detection, and tetracycline in the synthetic samples
could be detected with the recovery in the range of 92.8%–107.2%, and RSD lower than 4.3%. The concentration of tetracycline
in milk detected with standard addition method was so low that it accorded with the safety regulation.
Supported by the National Natural Science Foundation of China (Grant Nos. 30570465 and 20425517) 相似文献
149.
150.
The title reduction of nitroaromatics ArNO(2) by vinyl halide radical cations CH(2)[double bond]CH-X(+*)(X = Cl or Br) to form arylnitrenium ions ArNH(+) involves a change in oxidation number of nitrogen from +3 to -1. This novel reaction provides a new route for the generation of arylnitrenium ions, a highly selective method for the detection of explosives in mixtures, and offers clues to the carcinogenic activity of nitroaromatics in vivo. 相似文献