全文获取类型
收费全文 | 10799篇 |
免费 | 1912篇 |
国内免费 | 1563篇 |
专业分类
化学 | 7722篇 |
晶体学 | 188篇 |
力学 | 699篇 |
综合类 | 151篇 |
数学 | 1464篇 |
物理学 | 4050篇 |
出版年
2024年 | 18篇 |
2023年 | 191篇 |
2022年 | 265篇 |
2021年 | 324篇 |
2020年 | 476篇 |
2019年 | 453篇 |
2018年 | 393篇 |
2017年 | 375篇 |
2016年 | 511篇 |
2015年 | 631篇 |
2014年 | 651篇 |
2013年 | 894篇 |
2012年 | 1070篇 |
2011年 | 1074篇 |
2010年 | 828篇 |
2009年 | 797篇 |
2008年 | 874篇 |
2007年 | 742篇 |
2006年 | 639篇 |
2005年 | 568篇 |
2004年 | 406篇 |
2003年 | 328篇 |
2002年 | 317篇 |
2001年 | 217篇 |
2000年 | 220篇 |
1999年 | 154篇 |
1998年 | 84篇 |
1997年 | 87篇 |
1996年 | 73篇 |
1995年 | 76篇 |
1994年 | 54篇 |
1993年 | 59篇 |
1992年 | 37篇 |
1991年 | 36篇 |
1990年 | 33篇 |
1989年 | 25篇 |
1988年 | 39篇 |
1987年 | 10篇 |
1986年 | 21篇 |
1985年 | 13篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 20篇 |
1977年 | 8篇 |
1973年 | 8篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
M. Boćkowski I. GrzegoryA. Kchahapuridze S. GierlotkaS. Porowski 《Journal of Crystal Growth》2010,312(18):2574-2578
In this work Ca3N2 was investigated as a potential flux for crystallization of GaN. Melting temperature of the potential flux at high N2 pressure evaluated by thermal analysis as 1380 °C is in good agreement with the theoretical prediction. It is shown that Ca3N2 present in the liquid gallium in small amount (1 at%) dramatically accelerates synthesis of GaN from its constituents. On the other hand, it does not influence significantly the rate of GaN crystallization from solution in gallium in temperature gradient for both unseeded and seeded configurations. However the habit and color of the spontaneously grown GaN crystals change drastically. For 10 mol% Ca3N2 content in the liquid Ga it was found that the GaN thick layer and GaN crystals (identified by micro-Raman scattering measurements) were grown on the substrate. For growth from molten Ca3N2 (100%) with GaN source, the most important observations were (i) GaN source material was completely dissolved in the molten Ca3N2 flux and (ii) after experiment, GaN crystals were found on the sapphire substrate. 相似文献
992.
993.
994.
995.
本文研究了丙三醇/水混合溶剂中十六烷基三甲基氯化铵(CTAC)溶液的粘度性质,考察了水杨酸钠(NaSal)浓度、CTAC浓度以及丙三醇体积分数等因素对CTAC胶束溶液粘度的影响,并与乙二醇/水混合溶剂中胶束的粘度进行比较。结果表明:在丙三醇/水混合溶剂中,当CTAC浓度一定时,CTAC溶液的相对粘度随着NaSal浓度的增大而增大;当NaSal浓度一定时,CTAC溶液的相对粘度随着CTAC浓度的增大出现最大值;CTAC溶液的相对粘度随着丙三醇体积分数的增大而下降。这种变化趋势与乙二醇/水混合溶剂中的粘度性质相类似。 相似文献
996.
Cancer immunotherapy is a revolutionary treatment method in oncology, which uses a human''s own immune system against cancer. Many immunomodulators that trigger an immune response have been developed and applied in cancer immunotherapy. However, there is the risk of causing an excessive immune response upon directly injecting common immunomodulators into the human body to trigger an immune response. Therefore, the development of intelligent stimuli-responsive immunomodulators to elicit controlled immune responses in cancer immunotherapy is of great significance. Nanotechnology offers the possibility of designing smart nanomedicine to amplify the antitumor response in a safe and effective manner. Progress relating to intelligent stimuli-responsive nano immunomodulators for cancer immunotherapy is highlighted as a new creative direction in the field. Considering the clinical demand for cancer immunotherapy, we put forward some suggestions for constructing new intelligent stimuli-responsive nano immunomodulators, which will advance the development of cancer immunotherapy.Progress relating to intelligent stimuli-responsive nano immunomodulators for cancer immunotherapy is highlighted. Suggestions for constructing new strategies have been put forward, which will advance the clinical development of cancer immunotherapy. 相似文献
997.
α-Arylpropanoic acids are pharmaceutically interesting compounds, some of them exhibit anti-flammatory and analgestic activities1. Even the enormous progress made in the synthesis of α-arylpropanoic acids by 1,2-aryl rearrangement of arylpropanone using thalium (III) nitrate1,2, silver (I) compounds,3,4 lead (IV) acetate5,6 and iodinate7 during the last decades. The route is, however, unsuitable for the preparation of pharmaceutical products (Naproxen, Ibuprofen and so on) because of the … 相似文献
998.
Lin XU En Bo WANG* Zhuang LI Hong Yu ZHANG Chao QIN Department of Chemistry Northeast Normal University Changchun Changchun Institute of Applied Chemistry Academia Sinica Changchun 《中国化学快报》2001,(12)
In recent years, there has been considerable interest in the fabrication of self-assembled ultrathin multilayer films, because of their availability to form nanostructured materials with tailored architecture and properties1. The layer-by-layer (LBL) self-assembly, initially developed for pairs of oppositely charged polyelectrolytes2, is an unusually simple and versatile technique to built up of ultrathin multilayer films. A special feature of the multilayer films is that the composition, t… 相似文献
999.
Yun Long ZHANG Liang Ren ZHANG* Zhen Jun YANG Ji Mei MIN Li He ZHANG* Yang LU Ning Bo GONG Qi Tai ZHENG National Research Laboratory of Natural Biomimetic Drugs Peking University Beijing Institue of Materia Medica Chinese 《中国化学快报》2001,(5)
Tubercidin (4-amino-7--D-riobofuranosyl-7-H-pyrrolo[2,3-d]pyrimidine) 1, an antibio-tic substance produced in the culture broth of Streptomyces tubericidus1, is an adenosine analog in which N-7 is replaced by a carbon atom. It has attracted much attention due to the biological activities for the growth inhibition of certain tumors, and many derivatives of tubercidin have been synthesized2-5.For the synthesis of tubercidin analogs, 4-chloro-7-H-pyrrolo[2,3-d]pyrimidine-2,3,5-tri-O-acetyl--D-r… 相似文献