全文获取类型
收费全文 | 9042篇 |
免费 | 1149篇 |
国内免费 | 809篇 |
专业分类
化学 | 6093篇 |
晶体学 | 126篇 |
力学 | 426篇 |
综合类 | 44篇 |
数学 | 1138篇 |
物理学 | 3173篇 |
出版年
2023年 | 143篇 |
2022年 | 197篇 |
2021年 | 262篇 |
2020年 | 382篇 |
2019年 | 320篇 |
2018年 | 283篇 |
2017年 | 314篇 |
2016年 | 403篇 |
2015年 | 419篇 |
2014年 | 405篇 |
2013年 | 599篇 |
2012年 | 663篇 |
2011年 | 674篇 |
2010年 | 468篇 |
2009年 | 456篇 |
2008年 | 480篇 |
2007年 | 434篇 |
2006年 | 404篇 |
2005年 | 361篇 |
2004年 | 298篇 |
2003年 | 226篇 |
2002年 | 233篇 |
2001年 | 166篇 |
2000年 | 170篇 |
1999年 | 162篇 |
1998年 | 77篇 |
1997年 | 78篇 |
1996年 | 87篇 |
1995年 | 89篇 |
1994年 | 71篇 |
1993年 | 94篇 |
1992年 | 100篇 |
1991年 | 75篇 |
1990年 | 59篇 |
1989年 | 53篇 |
1988年 | 56篇 |
1987年 | 50篇 |
1986年 | 53篇 |
1985年 | 79篇 |
1984年 | 61篇 |
1983年 | 63篇 |
1982年 | 68篇 |
1981年 | 52篇 |
1980年 | 58篇 |
1979年 | 63篇 |
1978年 | 52篇 |
1977年 | 52篇 |
1976年 | 46篇 |
1974年 | 53篇 |
1973年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 299 毫秒
91.
Cynthia M. Allen Joseph M. Weber Johan E. van Lier 《Photochemistry and photobiology》1995,62(1):184-189
Abstract— Transmission of infectious diseases through blood transfusions is well known. Ultraviolet irradiation, solvents and detergents provide a means of sterilizing noncellular blood components. However these harsh methods are not applicable to cellular blood products. Recently, attempts have been made to sterilize biological fluids using photodynamic treatment and phthalocyanine (Pc) dyes have been advanced as photosensitizers for this purpose. We have evaluated a series of water-soluble Pc, chelated with different central metal ions, substituted to different degrees with sulfonato and r-butyl groups, for their effectiveness to reduce virus infectivity in red blood cell suspensions. Vaccinia virus cytopathogenicity was determined by endpoint serial dilutions in the CV-1 cell line. Anti-viral activity increased with the central metal ion in the following order: Ga(III) < Al(III) < Zn(II), and varied inversely with the degree of sulfonation. Furthermore, addition of a t -butyl group onto the trisulfonated dyes (PcS3 [ t -Bul) resulted in a 5–40-fold increase in anti-viral potency, suggesting that amphiphilicity enhances the photodynamic activity of the dye. Strong anti-viral photosensitizing properties cannot be the sole selection criterion. Of equal importance is the preservation of blood component integrity. Accordingly, the photohemolytic activity of the dyes was evaluated using the rate of hemolysis as a parameter and a toxicity index was defined. Among the most active dyes, the AlPcS3 ( t -Bu) complex exhibited the most favorable anti-viral properties combined with a low toxicity index. Our results suggest that trisulfophthalocyanines, bearing an additional t -butyl group to enhance amphiphilicity, are particularly promising dyes for photodynamic blood sterilization. 相似文献
92.
Kai Kang Cheng-you Kan Yi Du De-shan Liu 《高分子科学》2005,(5):479-485
Soap-free poly(methyl methacrylate-ethyl acrylate-methacrylic acid) latex particles with narrow size distribution were synthesized by seeded emulsion polymerization, and the porous particles were created by a stepwise alkali/acid treatment method. Effects of acid treatment conditions on the particle morphology were investigated. Results show that one to three pores were formed inside most of particles after post-treatment. At pH 7.0, when the treatment temperature was lower than 70℃, the size of particles and the volume of pores remained almost unchanged, and these two values increased significantly when the temperature was higher than 70℃. Both the particle size and the pore volume decreased with the increase of initial pH value and treatment time in the acid treatment. As the pH was below 4.0 and the treatment time was longer than 180 min, the particles shrunk in size. 相似文献
93.
94.
95.
Sensitive determination of free and plasma protein-bound dipyridamole by high-performance liquid chromatography 总被引:1,自引:0,他引:1
For many years dipyridamole (DP) has been used in the treatment of hypertension as a vasodilator, but recently it has been recognised as an anti-platelet aggregation agent and to potentiate anti-metabolite activity. A rapid and sensitive (20 nM) procedure for the determination of free and protein-bound DP in plasma, using reversed-phase high-performance liquid chromatography on an Ultrasphere XL ODS (3 microns) column (70 mm x 4.6 mm I.D.) with ultraviolet detection (280 nm), is reported. Free and bound DP were separated using ultrafiltration. Concentrations of DP between 0.1 and 10 microM were measured in plasma with a relative standard deviation of less than 9.6%. The subsequent determination of DP levels in patients orally administered 450 mg per day showed that DP binding to plasma protein is higher than 90%. 相似文献
96.
Kai Jun LUO Ming Gui XIE* Qing JIANG Testing Center of Sichuan Normal University Chengdu Research institute of Molecular Function Material Sichuan University Chengdu 《中国化学快报》2003,14(11)
Circularly polarized luminescent(CPL) materials possess special dissymmetric optical property, i.e. luminescent light having different intensities for left (L) and right(R) circularly polarized components. Recently, these materials have been applied in colour-image projection, stereoscopic displays and light-emitting diodes(LEDS)1-7. We have synthesized a new porphyrin derivative, tetra-4[4'-(2-methylbutoxy)benzoyloxy] phenyl porphyrin [T(MBBP)P], by introducing a chiral group, which p… 相似文献
97.
98.
The binding of palladium to high-molecular-mass compounds in palladium-treated lettuce is investigated as an example for a biological matrix. The total palladium concentration in lettuce leaves is 10.3 ng/g wet weight. After homogenization, high-molecular-mass compounds (> 10 kDa) are isolated by ultrafiltration. For separation of these palladium species a combination of preparative gel permeation chromatography (GPC) and preparative isotachophoresis (ITP) is used. Palladium is determined in separated fractions by using a highly sensitive total reflection X-ray fluorescence (TXRF) method after preconcentration. After GPC separation, four main fractions of palladium species are collected, each containing palladium in ng quantities (3-10 ng). Two of these fractions are further separated by ITP, yielding at least three main peaks per GPC fraction, each containing palladium in the range of 0.3-3 ng. These palladium containing peaks are characterized by high-performance size exclusion chromatography (HPSEC) and capillary isotachophoresis (cITP) in parallel. HPSEC enables the estimation of the molecular mass of six main palladium peaks, covering a molecular mass range of 69-200 kDa. It is also shown that the estimation of molecular mass after separation is more reliable than the respective estimation directly in the first GPC run. However, cITP reveals that each of the separated peaks is still a mixture of at least five different compounds. 相似文献
99.
Weber W 《Physical review letters》1987,58(13):1371-1374
100.