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排序方式: 共有4135条查询结果,搜索用时 15 毫秒
931.
932.
将均相沉淀法制备的ZnO粉体加入到TiO2前驱体中合成了ZnTiO3/TiO2异质复合材料,利用XRD、SEM、UV-Vis-DRS、BET以及FTIR等手段对其进行表征,同时在紫外光区测试了光催化氧化降解亚甲基蓝溶液的性能.结果表明,锌钛摩尔比和焙烧温度影响产物的组成、形貌和光催化性能,当锌钛摩尔比0.2、焙烧温度600 ℃,产物呈现出均匀棒状物形貌,具有介孔结构,-OH含量也最多,相对于纯TiO2具有更强的紫外吸收性能,并且出现红移现象,光照120 min后亚甲基蓝降解率可达到99;. 相似文献
933.
934.
gem‐Difluoroolefination of Diaryl Ketones and Enolizable Aldehydes with Difluoromethyl 2‐Pyridyl Sulfone: New Insights into the Julia–Kocienski Reaction 下载免费PDF全文
Bing Gao Dr. Yanchuan Zhao Dr. Mingyou Hu Dr. Chuanfa Ni Prof. Dr. Jinbo Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(25):7803-7810
The direct conversion of diaryl ketones and enolizable aliphatic aldehydes into gem‐difluoroalkenes has been a long‐standing challenge in organofluorine chemistry. Herein, we report efficient strategies to tackle this problem by using difluoromethyl 2‐pyridyl sulfone as a general gem‐difluoroolefination reagent. The gem‐difluoroolefination of diaryl ketones proceeds by acid‐promoted Smiles rearrangement of the carbinol intermediate; the gem‐difluoroolefination is otherwise difficult to achieve through a conventional Julia–Kocienski olefination protocol under basic conditions due to the retro‐aldol type decomposition of the key intermediate. Efficient gem‐difluoroolefination of aliphatic aldehydes was achieved by the use of an amide base generated in situ (from CsF and tris(trimethylsilyl)amine), which diminishes the undesired enolization of aliphatic aldehydes and provides a powerful synthetic method for chemoselective gem‐difluoroolefination of multi‐carbonyl compounds. Our results provide new insights into the mechanistic understanding of the classical Julia–Kocienski reaction. 相似文献
935.
J. H. Moon M. Ebihara B. F. Ni B. Arporn P. Setyo R. M. Theresia B. S. Wee N. A. Abd. Salim P. C. B. Pabroa 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(1):217-221
Since 2000, collaborative studies for applying NAA have been performed through the Forum for Nuclear Cooperation in Asia (FNCA)
sponsored by the Japanese Government. White rice is a main food for Asians and thus was selected as a common target sample
for a collaborative study in 2008. Seven Asian countries including China, Indonesia, Japan, Korea, Malaysia, Philippines and
Thailand, are greatly concerned about the composition of arsenic, heavy metals, and essential trace elements and took part
in this study. Rice samples were purchased and prepared by following a protocol that had been proposed for this study. Samples
were analyzed by their own NAA systems. In each country, more than 10 elements were examined and the results were compared.
These data will be very useful in the monitoring of the levels of food contamination and to evaluate the nutritional status
for people living in Asia. 相似文献
936.
Yao Meng Yizhou Liu Tao Li Tianli Feng Jiacheng Huang Zheng Ni Wenchao Qiao 《Molecules (Basel, Switzerland)》2022,27(3)
We report the surface morphology and the nonlinear absorption characteristics of MXene VCrC nanosheets prepared by the liquid-phase exfoliation method. The self-made MXene VCrC was applied as a saturable absorber in the Tm:YAP laser experiments, performing excellent Q-switching optical modulation characteristics in infrared range. With this absorber, a stable passively Q-switched 2 μm laser was achieved. Under an incident pump power of 3.52 W, a maximum output power of 280 mW was obtained with a T = 3% output coupler at a repetition frequency of 49 kHz. The corresponding pulse energy and peak power were 5.7 μJ and 6.6 W, respectively. The shortest pulse duration was 658 ns at the repetition rate of 63 kHz with a T = 1% output coupler. 相似文献
937.
研究了氟化钾催化下全氟环氧丙烷的自聚以及与全氟戊(或己)二酰氟的双官能团阴离子聚合。发现在常压力下氟化钾催化全氟环氧丙烷自聚的活性比文献报道的氟化铯催化活性小得多,但氟化钾催化全氟环氧丙烷和全氟戊(或己)二酰氟的双官能团聚合活性却比催化全氟环氧丙烷自聚的活性大。产物分离时两层中间的乳化层有催化作用,其结构可能为K~ ~-OCF_2R_fCF_2O~-K~ ,它还使全氟环氧丙烷在与全氟戊(或己)二酰氟的双官能团聚合中的自聚活性提高,类似于文献关于R_fO~-C_s~ 是活性催化剂的报道。对此催化作用提出解释。 相似文献
938.
Jingzhong Zhu Yinchang Zhao Muhammad Zulfiqar Shuming Zeng Jun Ni 《Physics letters. A》2018,382(21):1395-1400
The electronic and magnetic properties of Fe-, Co-, and Ni-decorated two dimensional (2D) BC3 are systematically investigated by first-principles calculations. We find that the Fe, Co, and Ni atoms can be strongly adsorbed on the hollow sites of 2D BC3. Fe and Co adatoms are more stable when adsorbed on the hollow sites of the carbon rings in the 2D BC3, while the hollow sites of boron-carbon rings in the 2D BC3 are the most stable sites for the adsorption of Ni adatoms. These proposed metal–BC3 complexes exhibit interesting electronic and magnetic behaviors. In particular, the Fe–BC3 and Co–BC3 complexes are metals with magnetic ground states , while the Ni–BC3 complex behaves as a nonmagnetic semiconductor with a direct bandgap. Furthermore, our magnetic analysis reveals that induced magnetism in the Fe–BC3 and Co–BC3 complexes arises from their local magnetic moments. Functionalization of 2D BC3 through these metal–adatom adsorption appears to be a promising way to extend its applications. 相似文献
939.
940.