全文获取类型
收费全文 | 288121篇 |
免费 | 1488篇 |
国内免费 | 449篇 |
专业分类
化学 | 131087篇 |
晶体学 | 4470篇 |
力学 | 16786篇 |
综合类 | 10篇 |
数学 | 44845篇 |
物理学 | 92860篇 |
出版年
2020年 | 2008篇 |
2019年 | 2567篇 |
2018年 | 11108篇 |
2017年 | 11764篇 |
2016年 | 8367篇 |
2015年 | 3020篇 |
2014年 | 4393篇 |
2013年 | 8684篇 |
2012年 | 10638篇 |
2011年 | 18969篇 |
2010年 | 12588篇 |
2009年 | 12939篇 |
2008年 | 16964篇 |
2007年 | 20091篇 |
2006年 | 6855篇 |
2005年 | 11463篇 |
2004年 | 8458篇 |
2003年 | 8231篇 |
2002年 | 6480篇 |
2001年 | 5756篇 |
2000年 | 4449篇 |
1999年 | 3172篇 |
1998年 | 2736篇 |
1997年 | 2774篇 |
1996年 | 2714篇 |
1995年 | 2311篇 |
1994年 | 2411篇 |
1993年 | 2306篇 |
1992年 | 2592篇 |
1991年 | 2722篇 |
1990年 | 2626篇 |
1989年 | 2701篇 |
1988年 | 2622篇 |
1987年 | 2644篇 |
1986年 | 2492篇 |
1985年 | 3125篇 |
1984年 | 3214篇 |
1983年 | 2693篇 |
1982年 | 2655篇 |
1981年 | 2622篇 |
1980年 | 2424篇 |
1979年 | 2821篇 |
1978年 | 2793篇 |
1977年 | 2902篇 |
1976年 | 2934篇 |
1975年 | 2719篇 |
1974年 | 2654篇 |
1973年 | 2807篇 |
1972年 | 2125篇 |
1971年 | 1978篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Khusnutdinov R. I. Shchadneva N. A. Mayakova Yu. Yu. Aminov R. I. 《Russian Journal of Organic Chemistry》2021,57(6):950-953
Russian Journal of Organic Chemistry - Binder-free iron- and nickel-containing micro-, meso-, and macroporous zeolites FeHY and NiHY were found to effectively catalyze Knoevenagel condensation of... 相似文献
62.
Elasasy M. E. A. Elnaggar D. H. Hafez N. A. Abdel Azab M. E. Amr A. E. Omran M. M. Mohamed A. M. 《Russian Journal of General Chemistry》2021,91(5):915-925
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity.... 相似文献
63.
64.
65.
Journal of Applied and Industrial Mathematics - We consider the optimization of the short wave phased antenna arrays as a quadratic programming problem. The penalty function method and the gradient... 相似文献
66.
Ahmed Waqar Chowdhury Z. Z. Kazi S. N. Johan MR. Akram Naveed Oon C. S. Abdelrazek Ali H. 《Journal of Thermal Analysis and Calorimetry》2021,144(4):1517-1534
Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers... 相似文献
67.
M. Kroon E. Andreasson E. Persson Jutemar V. Petersson L. Persson M. Dorn P.A.T. Olsson 《Experimental Mechanics》2018,58(1):75-86
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters. 相似文献
68.
Indermeet Kohli Taylor L. Braunberger Amanda F. Nahhas Fatima N. Mirza Mohsen Mokhtari Alexis B. Lyons Nikiforos Kollias Eduardo Ruvolo Henry W. Lim Iltefat H. Hamzavi 《Photochemistry and photobiology》2020,96(1):208-214
Human skin is exposed to visible light (VL; 400–700 nm) and long-wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad-spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. Subjects were irradiated with 2 light sources (80–480 J cm−2): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4-mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm−2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm−2), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range. 相似文献
69.
70.