全文获取类型
收费全文 | 13554篇 |
免费 | 1817篇 |
国内免费 | 1356篇 |
专业分类
化学 | 10056篇 |
晶体学 | 197篇 |
力学 | 708篇 |
综合类 | 80篇 |
数学 | 1387篇 |
物理学 | 4299篇 |
出版年
2024年 | 28篇 |
2023年 | 217篇 |
2022年 | 291篇 |
2021年 | 475篇 |
2020年 | 543篇 |
2019年 | 546篇 |
2018年 | 420篇 |
2017年 | 409篇 |
2016年 | 625篇 |
2015年 | 602篇 |
2014年 | 727篇 |
2013年 | 1034篇 |
2012年 | 1210篇 |
2011年 | 1246篇 |
2010年 | 881篇 |
2009年 | 791篇 |
2008年 | 910篇 |
2007年 | 761篇 |
2006年 | 749篇 |
2005年 | 607篇 |
2004年 | 558篇 |
2003年 | 436篇 |
2002年 | 485篇 |
2001年 | 334篇 |
2000年 | 240篇 |
1999年 | 227篇 |
1998年 | 168篇 |
1997年 | 149篇 |
1996年 | 132篇 |
1995年 | 110篇 |
1994年 | 99篇 |
1993年 | 82篇 |
1992年 | 76篇 |
1991年 | 89篇 |
1990年 | 57篇 |
1989年 | 50篇 |
1988年 | 55篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 36篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1975年 | 10篇 |
1971年 | 10篇 |
1970年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In this paper, a natural R
+
n+1
extension of singular integrals, i.e.,T
κ:f→K*φ
t
*t with K a standard C-Z kernel and ϕ usual one, is investigated. One of the main results is: Let (dμ, udx) ∈C1 and u-Mw, w∈A∞, then Tk is of type (Lp(udx), Lp(dμ)). As a related topic, a maximal operator
is proved to be of type
, where
, provided (dμ, udx) ∈C1 and u∈ A∞.
Supported by National Science Foundation of China 相似文献
102.
103.
104.
105.
106.
本文拟定的纸色谱法是以苯-乙酸乙酯-甲醇-乙酸(9:2:1:1)作展开剂,将血卟啉衍生物(HPD)分离为五部份,分别测定各部份浸取液的荧光发射光谱,作为一种对血卟啉衍生物组份作对比鉴定的参考方法。采用Ward的高效液相色谱程序对比研究结果表明,国产与美国产HPD的组份近似,均以血卟啉为主要组份,而前者血卟啉的含量较高;二者还均含有羟乙基乙烯基衍生物和羟基乙酸酯,初步研究了血卟啉衍生物在甲醇-水溶剂系统中的高效液相色谱行为,进一步将血卟啉衍生物分离为九部份,有利于单一组份研究。 相似文献
107.
Cheng-shen Zhu Xin Kang Su-qin He Liu-yang Wang Li-yun Lu College of Materials Engineering Zhengzhou University Zhengzhou China 《高分子科学》2002,(6):551-557
The montmorillonites (MMTs), layered, smectite-type silicates, were premodified by two different methods priorto the polymer melt intercalation. In one case MMTs were modified with cetyltrimethylammonium bromide (CTAB), andtermed as organomontmorillonites (OMMTs); in the other case MMTs were modified by nylon, and the products were calledmodified montmorillonites (MMMTs). The effects of CTAB and nylon on the MMTs were investigated by using TG andWAXD. The results show that interlayer spacings of CTAN and nylon modified MMTs are larger than that of sodium MMTs.Then, polyamide 66 (PA 66)/MMT nanocomposites were obtained through the method of melt intercalation of polymers. Thenanocomposites were characterized by WAXD, TEM and Molau experiments. The results indicate that the MMTs dispersehomogeneously in the PA 66 matrix. The mechanical properties of nanocomposites, such as tensile properties and flexuralproperties, were also measured and show a tendency to increase with increase of MMT content and reach the maximumvalues at 5phr MMT content. The heat distortion temperature (HDT) of the nanocomposites (7 phr) is about 32 K higher thanthat of pure PA 66. 相似文献
108.
109.
110.
Ji-Hyun Seo Ju-Woon Lee Jae-Hun Kim Eui-Baek Byun Soo-Young Lee Il-Jun Kang Myung-Woo Byun 《Radiation Physics and Chemistry》2007,76(11-12):1855-1857
Egg allergy is one of the most serious of the immediate hypersensitivity reactions to foods. Such an allergic disorder is mediated by IgE antibodies stimulated by T-helper type 2 (Th2) lymphocytes. This study was undertaken to evaluate changes of allergenicity and cytokine profiles by exposure of irradiated ovalbumin (OVA), a major allergen of egg white, in the OVA-allergic mice model. OVA solutions (2 mg/ml in 0.01 M phosphate buffered saline (PBS) were gamma-irradiated to 50 and 100 kGy. The allergenicity in the OVA-allergy-induced mice model was remarkably reduced when challenged with irradiated OVA. Cultures of spleen cells harvested from OVA-sensitized mice showed a significant decrease in Th2 cytokine levels of ILs-4 and -5 with a concomitant increase in Th1 cytokine levels of IL-12 when co-cultured with irradiated OVA. However, IFN-γ level decreased dependant on the radiation dose of co-cultured OVA. The levels of IgEs and Th2-cytokine were reduced dependant on the radiation dose. These data show that the irradiated OVA could downregulate the activity of Th2 lymphocytes in OVA-sensitized mice. 相似文献