全文获取类型
收费全文 | 7987篇 |
免费 | 835篇 |
国内免费 | 529篇 |
专业分类
化学 | 5589篇 |
晶体学 | 96篇 |
力学 | 419篇 |
综合类 | 46篇 |
数学 | 700篇 |
物理学 | 2501篇 |
出版年
2024年 | 18篇 |
2023年 | 121篇 |
2022年 | 226篇 |
2021年 | 297篇 |
2020年 | 276篇 |
2019年 | 270篇 |
2018年 | 206篇 |
2017年 | 212篇 |
2016年 | 315篇 |
2015年 | 288篇 |
2014年 | 370篇 |
2013年 | 561篇 |
2012年 | 703篇 |
2011年 | 696篇 |
2010年 | 492篇 |
2009年 | 433篇 |
2008年 | 545篇 |
2007年 | 460篇 |
2006年 | 433篇 |
2005年 | 370篇 |
2004年 | 319篇 |
2003年 | 263篇 |
2002年 | 260篇 |
2001年 | 168篇 |
2000年 | 133篇 |
1999年 | 127篇 |
1998年 | 106篇 |
1997年 | 83篇 |
1996年 | 92篇 |
1995年 | 77篇 |
1994年 | 58篇 |
1993年 | 60篇 |
1992年 | 54篇 |
1991年 | 53篇 |
1990年 | 27篇 |
1989年 | 25篇 |
1988年 | 24篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1973年 | 4篇 |
1971年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有9351条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
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
56.
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
57.
有机化合物在光窗上的结焦严重地影响激光引发化学反应及光学原位实时探测。本文报道在1,2-二氯丙烷反应系统中,光窗结焦现象同时存在于激光引发反应及热反应过程中,对光窗在300℃条件 下的结焦机理研究表明,少量氧气在光窗结焦过程中起关键作用。结焦前驱体的红外光谱研究表明,前驱体的可能结构为1-丙炔-1,3-二醇的缩聚体。该化合物极易通过缩聚反应形成更大的分子,最终导致光 窗结焦。对系统及反应物进行彻底除氧,光窗结焦现象大为改善。 相似文献
58.
Ceria-supported copper-palladium catalysts have been tested in the hydrogenation of 1,3-butadiene. The SMSI behavior of the bimetallic catalysts depended on the temperature of reduction. They were analyzed by H2 chemisorption and XPS. 相似文献
59.
SynthesisandCrystalStructureof(Et_4N)_2[Pd_2(mp)_2(mpH)_2]ShiJi-Cheng;HuangXiao-Ying;WenTing-Bin;DengYu-Heng;ChengChang-Neng;Li?.. 相似文献
60.
A nonenzymatic glucose sensor with good selectivity for the ascorbic acid oxidation is presented. After the gold polycrystalline electrode was subjected to amalgamation treatment, two advantageous effects were observed. One is the enhancement of the surface roughness and the other is an increase in the catalytic current in the glucose oxidation. Besides the known first effect, the latter provided another advantageous effect in a fabrication of nonenzymatic glucose sensor. Using a gold electrode subjected to amalgamation treatment for 60 s, two calibration curves for glucose oxidation at two different potentials of ?0.1 V and 0.25 V were obtained and compared. At the potential of ?0.1 V, at which no ascorbic acid was oxidized and no interference effect was observed, a current sensitivity of 16 μA cm?2 mM?1 from zero to 10 mM glucose concentration range was obtained. At the other potential of 0.25 V, at which ascorbic acid was easily oxidized, a satisfactory calibration curve with negligible ascorbic acid interference was also obtained together with a more enhanced current sensitivity of 32 μA cm?2 mM?1. 相似文献