全文获取类型
收费全文 | 22952篇 |
免费 | 828篇 |
国内免费 | 63篇 |
专业分类
化学 | 14775篇 |
晶体学 | 377篇 |
力学 | 713篇 |
综合类 | 1篇 |
数学 | 1774篇 |
物理学 | 6203篇 |
出版年
2023年 | 236篇 |
2022年 | 571篇 |
2021年 | 525篇 |
2020年 | 588篇 |
2019年 | 708篇 |
2018年 | 641篇 |
2017年 | 627篇 |
2016年 | 917篇 |
2015年 | 638篇 |
2014年 | 1050篇 |
2013年 | 1906篇 |
2012年 | 1544篇 |
2011年 | 1684篇 |
2010年 | 1095篇 |
2009年 | 925篇 |
2008年 | 1105篇 |
2007年 | 1090篇 |
2006年 | 853篇 |
2005年 | 744篇 |
2004年 | 589篇 |
2003年 | 462篇 |
2002年 | 416篇 |
2001年 | 251篇 |
2000年 | 241篇 |
1999年 | 181篇 |
1998年 | 123篇 |
1997年 | 150篇 |
1996年 | 177篇 |
1995年 | 170篇 |
1994年 | 162篇 |
1993年 | 180篇 |
1992年 | 215篇 |
1991年 | 157篇 |
1990年 | 146篇 |
1989年 | 160篇 |
1988年 | 135篇 |
1987年 | 134篇 |
1986年 | 115篇 |
1985年 | 165篇 |
1984年 | 181篇 |
1983年 | 134篇 |
1982年 | 143篇 |
1981年 | 132篇 |
1980年 | 143篇 |
1979年 | 146篇 |
1978年 | 148篇 |
1977年 | 133篇 |
1976年 | 96篇 |
1975年 | 92篇 |
1974年 | 91篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
Gurmessa Getahun Tadesse Singh Girija Shankar 《Research on Chemical Intermediates》2017,43(11):6447-6504
Research on Chemical Intermediates - Metal–carbenoids from α-diazocarbonyl compounds are well-known reactive intermediates with a long history of useful applications in synthetic organic... 相似文献
992.
Ratnakar N. Asolkar Ahilya Singh Paul R. Jensen William Aalbersberg Brad K. Carté Klaus-D. Feussner Ramesh Subramani Antonio DiPasquale Arnold L. Rheingold William Fenical 《Tetrahedron》2017,73(16):2234-2241
Six cytotoxic and antimicrobial metabolites of a new bromo-phenazinone class, the marinocyanins A-F (1–6), were isolated together with the known bacterial metabolites 2-bromo-1-hydroxyphenazine (7), lavanducyanin (8, WS-9659A) and its chlorinated analog WS-9659B (9). These metabolites were purified by bioassay-guided fractionation of the extracts of our MAR4 marine actinomycete strains CNS-284 and CNY-960. The structures of the new compounds were determined by detailed spectroscopic methods and marinocyanin A (1) was confirmed by crystallographic methods. The marinocyanins represent the first bromo-phenazinones with an N-isoprenoid substituent in the skeleton. Marinocyanins A-F show strong to weak cytotoxicity against HCT-116 human colon carcinoma and possess modest antimicrobial activities against Staphylococcus aureus and amphotericin-resistant Candida albicans. 相似文献
993.
994.
Vineet Singh 《Journal of Physics and Chemistry of Solids》2009,70(7):1074-1079
In the present study we have synthesized CdS semiconducting quantum dots by the chemical precipitation method using Thioglycerol as the capping agent. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) are employed to characterize the size, morphology and crystalline structure of the as-prepared material. The synthesized QPs have a mixture of cubical and hexagonal crystal symmetry with 12 nm average diameter. Ultraviolet-visible (UV-vis) absorption spectroscopy is used to calculate the band gap of the material and blue shift in absorption edge. Confinement of the optical phonon modes in the QPs is studied by Raman spectroscopy, while FTIR for identification of chemical bonds in the nanomaterial. Multiple cadmium and sulphur defects were observed by employing the photoluminescence (PL) method. 相似文献
995.
R. K. Gupta A. K. Sinha B. N. Raja Sekhar A. K. Srivastava G. Singh S. K. Deb 《Applied Physics A: Materials Science & Processing》2011,103(1):13-19
Controllable and uniform doping of nanowires (NWs) is the ultimate challenge prior to their effective application. Si NWs
amorphize and bend toward the impinging ions under ion irradiation as a result of viscous flow. We demonstrate that thermal
annealing induces a full recovery of the crystalline phase corresponding to the unbending of the NWs. The competition between
Solid Phase Epitaxy and Random Nucleation and Growth at the nanoscale is the key parameter controlling the recovery. 相似文献
996.
Shekhar Kumar U. Kamachi Mudali R. Natarajan 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):587-589
Tri-n-butyl phosphate (TBP) is the workhorse of solvent extraction operations in nuclear fuel cycle as well as an important industrial chemical. Its PVT properties are not available in literature. In this study, PVT properties of TBP, estimated using group contribution method, are reported. Wagner constants were also reported in the range of 273.15?K to critical temperature. 相似文献
997.
Kinetics of change in photoinduced currents (during illumination and after switching off light source) in the solid state
of some ferrocene derivatives, namely, ferrocenecarboxylic acid, acetylferrocene, ferrocenecarbaldehyde, hydroxymethyl ferrocene
have been studied in dry nitrogen gas atmosphere. Unusual/anomalous photocurrent versus time profiles were observed in some ferrocene derivatives at certain cell temperatures. The kinetics of current changes under
photoexcitation and after switching off the light source have been observed to be complicated in nature. Temperature-dependent
behavior of the studied kinetics indicates that charge carrier trapping/detrapping and recombination processes are significantly
temperature dependent. These processes have an important role in causing the temperature dependent unusual/anomalous photocurrent
versus time profiles in the ferrocene derivatives studied. 相似文献
998.
999.
1000.