全文获取类型
收费全文 | 20204篇 |
免费 | 1912篇 |
国内免费 | 849篇 |
专业分类
化学 | 14667篇 |
晶体学 | 144篇 |
力学 | 661篇 |
综合类 | 47篇 |
数学 | 2499篇 |
物理学 | 4947篇 |
出版年
2024年 | 37篇 |
2023年 | 264篇 |
2022年 | 354篇 |
2021年 | 402篇 |
2020年 | 499篇 |
2019年 | 513篇 |
2018年 | 397篇 |
2017年 | 382篇 |
2016年 | 784篇 |
2015年 | 818篇 |
2014年 | 923篇 |
2013年 | 1489篇 |
2012年 | 1731篇 |
2011年 | 1628篇 |
2010年 | 1048篇 |
2009年 | 887篇 |
2008年 | 1365篇 |
2007年 | 1236篇 |
2006年 | 1243篇 |
2005年 | 1082篇 |
2004年 | 905篇 |
2003年 | 739篇 |
2002年 | 659篇 |
2001年 | 372篇 |
2000年 | 310篇 |
1999年 | 245篇 |
1998年 | 208篇 |
1997年 | 223篇 |
1996年 | 251篇 |
1995年 | 175篇 |
1994年 | 168篇 |
1993年 | 166篇 |
1992年 | 117篇 |
1991年 | 99篇 |
1990年 | 102篇 |
1989年 | 76篇 |
1988年 | 65篇 |
1987年 | 55篇 |
1986年 | 85篇 |
1985年 | 102篇 |
1984年 | 77篇 |
1983年 | 48篇 |
1982年 | 61篇 |
1981年 | 61篇 |
1980年 | 64篇 |
1979年 | 49篇 |
1978年 | 53篇 |
1977年 | 39篇 |
1976年 | 51篇 |
1975年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
本文就薄膜法制样、用X-射线荧光谱法分析稀土样品时,试样面积和厚度对分析结果产生的影响作了定量研究,提出的有关分析条件和参数用于实际样品分析中,获得了满意的分析结果。 相似文献
63.
64.
Ultrasound treatment acceleration of solvent extraction for fumigant residues from wheat 总被引:1,自引:0,他引:1
Concerns about consumer and worker safety and the fate of fumigants have fuelled strong efforts to determine their residues in foodstuffs. Fumigants are usually extracted from commodities with solvent at room temperature (25 degrees C). In this paper, solvent extraction of methyl bromide, phosphine, carbonyl sulfide, and carbon disulfide using ultrasonic acceleration or heating was evaluated. Wheat samples plus solvent, in gas-tight bottles, were placed in an ultrasonic chamber or an oven (50 degrees C), and fumigants were released into the headspace over the solvent. Completeness of extraction was demonstrated within 2 h for ultrasonic extraction, 7-20 h for 50 degrees C heating, and 8-35 h for room temperature extraction. The rapidity of extraction was mainly due to ultrasonic vibration rather than increased temperature. 相似文献
65.
双波长分光光度法同时测定岩石矿物中的微量金和钯 总被引:2,自引:0,他引:2
本文提出以硫代米蚩酮为显色剂,用双波长分光光度法同时测定岩石矿物中的微量金和钯的方法,消除了测定金钯的相互干扰,该方法简便,快速,选择性好,用于矿石样品中金和钯的测定,结果满意。 相似文献
66.
67.
The monodisperse, porous poly(chloromethylstyrene-co-divinylbenzene) beads of 7.9 microm were prepared by a single-step swelling and polymerization method. The seed particles prepared by dispersion polymerization exhibited good absorption of the monomer phase. Based on this media, a weak cation-exchange (WCX) stationary phase for HPLC was synthesized by a new chemically modified method. The prepared resin has advantages of biopolymer separation, high column efficiency, low column backpressure, high protein mass recovery, and good resolution for proteins. The dynamic protein-loading capacity of the synthesized WCX packings was 18.2 mg/g. Five proteins were separated in 3.0 min using the synthesized WCX stationary phase. The experimental results show that the obtained WCX resin has very weak hydrophobicity. The WCX resin was also used for the rapid separation and purification of lysozyme from egg white in 5.0 min with only one step. The purity and specific bioactivity of the purified lysozyme were found to be more than 93% and 70 245 U/mg, respectively. 相似文献
68.
69.
A simply fabricated microfluidic device using a green organic light emitting diode (OLED) and thin film interference filter as integrated excitation source is presented and applied to fluorescence detection of proteins. A layer-by-layer compact system consisting of glass/PDMS microchip, pinhole, excitation filter and OLED is designed and equipped with a coaxial optical fiber and for fluorescence detection a 300 microm thick excitation filter is employed for eliminating nearly 80% of the unwanted light emitted by OLEDs which has overlaped with the fluorescence spectrum of the dyes. The distance between OLED illuminant and microchannels is limited to approximately 1 mm for sensitive detection. The achieved fluorescence signal of 300 microM Rhodamine 6G is about 13 times as high as that without the excitation filter and 3.5 times the result of a perpendicular detection structure. This system has been used for fluorescence detection of Rhodamine 6G, Alexa 532 and BSA conjugates in 4% linear polyacrymide (LPA) buffer (in 1 x TBE, pH 8.3) and 1.4 fmol and 35 fmol mass detection limits at 0.7 nl injection volume for Alexa and Rhodamine dye have been obtained, respectively. 相似文献
70.
毛细管电泳法快速分离和检测肠毒性大肠杆菌 总被引:4,自引:0,他引:4
建立了快速分离和检测引起仔猪腹泻的肠毒性大肠杆菌K88、K99和 987P细菌细胞的毛细管区带电泳方法 ,并进行了腹泻仔猪粪便中肠毒性大肠杆菌的应用检测分析。结果表明 ,在电泳缓冲液为 0 0 5mol/LNa2 CO3 NaHCO3(pH 9 9)、分离电压为 1 4 1kV、检测波长为 2 1 0nm的电泳条件下 ,E coliK88、K99和 987P的细胞分别具有单一、稳定的特征谱峰 ,其保留时间的相对标准偏差RSD≤ 0 9% ;在确定的实验条件下 ,实现了腹泻仔猪粪便中肠毒性大肠杆菌的快速检测分析 ,发现将出生 5d~ 6d的腹泻仔猪粪便引入培养基中增殖后主要检出K88。 相似文献