全文获取类型
收费全文 | 1688篇 |
免费 | 50篇 |
国内免费 | 8篇 |
专业分类
化学 | 1147篇 |
晶体学 | 28篇 |
力学 | 26篇 |
数学 | 79篇 |
物理学 | 262篇 |
无线电 | 204篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 12篇 |
2020年 | 20篇 |
2019年 | 17篇 |
2018年 | 17篇 |
2017年 | 21篇 |
2016年 | 30篇 |
2015年 | 23篇 |
2014年 | 48篇 |
2013年 | 71篇 |
2012年 | 85篇 |
2011年 | 114篇 |
2010年 | 55篇 |
2009年 | 59篇 |
2008年 | 121篇 |
2007年 | 116篇 |
2006年 | 105篇 |
2005年 | 71篇 |
2004年 | 59篇 |
2003年 | 70篇 |
2002年 | 60篇 |
2001年 | 26篇 |
2000年 | 34篇 |
1999年 | 20篇 |
1998年 | 22篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 10篇 |
1994年 | 25篇 |
1993年 | 23篇 |
1992年 | 21篇 |
1991年 | 31篇 |
1990年 | 16篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 24篇 |
1985年 | 37篇 |
1984年 | 24篇 |
1983年 | 18篇 |
1982年 | 18篇 |
1981年 | 15篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 20篇 |
1975年 | 11篇 |
1974年 | 11篇 |
排序方式: 共有1746条查询结果,搜索用时 8 毫秒
101.
Ten samples of commercial blue mussels (Mytilus edulis) from Japan were analyzed for domoic acid by an indirect competitive enzyme immunoassay (idc-EIA) based on an anti-domoic acid monoclonal antibody. Domoic acid was found in all samples at low concentrations (0.11-1.81 ng/g mussel tissue). The presence of domoic acid was confirmed by liquid chromatography coupled with immunoaffinity chromatography using an anti-domoic acid monoclonal antibody as ligand. To our knowledge, this is the first reported detection of domoic acid, a causative agent of amnesic shellfish poisoning, in Japanese mussels. 相似文献
102.
黄花倒水莲皂甙Reinioside C在大鼠体内代谢产物的鉴定 总被引:3,自引:0,他引:3
为了探讨五环三萜皂甙ReiniosideC在大鼠体内代谢产物的结构,单剂量口服ReiniosideC,5h后放血处死,用制备型高效液相色谱方法对血液和各脏器进行提取分离,从大肠内容物和粪中,分离得到了7种代谢产物.用FAB-MS,1H NMR和13C NMR方法鉴定了它们的结构. 相似文献
103.
104.
Secondary 2-thiophenecarboxamides efficiently undergo unique triarylation accompanied by formal decarbamoylation under palladium catalysis. 3-Substituted thiophenes, especially having an electron-withdrawing group, can also be triarylated. 相似文献
105.
An efficient and practical procedure for the synthesis of esonarimod, (R,S)-2-acetylthiomethyl-4-(4-methylphenyl)-4-oxobutanoic acid (1), a new antirheumatic drug, has been developed. The intermediate, 2-methylene-4-(4-methylphenyl)-4-oxobutanoic acid (2), was prepared by Friedel-Crafts acylation of toluene with itaconic anhydride (3) in the presence of aluminum trichloride and nitrobenzene in 63% yield without silica gel column purification. Compound 1 was prepared by Michael addition of 2 with thioacetic acid (4) in 74% yield. Overall, 1 was obtained in 47% yield from 3. The structures and synthetic mechanisms of by-products (five compounds) of 2 were also clarified. 相似文献
106.
Controlled production of monodisperse double emulsions by two-step droplet breakup in microfluidic devices 总被引:13,自引:0,他引:13
Okushima S Nisisako T Torii T Higuchi T 《Langmuir : the ACS journal of surfaces and colloids》2004,20(23):9905-9908
A microfluidic device having both hydrophobic and hydrophilic components is exploited for production of multiple-phase emulsions. For producing water-in-oil-in-water (W/O/W) dispersions, aqueous droplets ruptured at the upstream hydrophobic junction are enclosed within organic droplets formed at the downstream hydrophilic junction. Droplets produced at each junction could have narrow size distributions with coefficients of variation in diameter of less than 3%. Control of the flow conditions produces variations in internal/external droplet sizes and in the internal droplet number. Both W/O/W emulsions (with two types of internal droplets) and oil-in-water-in-oil emulsions were prepared by varying geometry and wettability in microchannels. 相似文献
107.
Okada K Nagashima T Kameshima Y Yasumori A 《Journal of colloid and interface science》2002,248(1):111-115
The effect of crystallite size on the thermal phase change and porous properties of boehmite was investigated using boehmites with crystallite sizes of 2.9 to 24.4 nm and boehmite gels prepared by precipitation and hydrothermal methods. The dehydroxylation temperature of boehmite increases, its phase transition temperature from gamma- to theta-Al(2)O(3) decreases and the theta- to alpha-Al(2)O(3) transition temperature increases as the crystallite size of the boehmite increases. Boehmite with a crystallite size of approximately 5 nm shows the highest specific surface area and greatest thermal stability. This boehmite contains pores of about 2-3 nm radius, suggested to be responsible for the superior porous properties and thermal stability. 相似文献
108.
Yoshimoto S Ohashi F Ohnishi Y Nonami T 《Chemical communications (Cambridge, England)》2004,(17):1924-1925
Nanocomposites consisting of conducting polyaniline and clay minerals were successfully synthesized from mechanochemically intercalated anilinium fluoride; the nanocomposites prepared by the mechanochemical intercalation method contained much more polyaniline in the clay layers than those prepared by a conventional solution method. 相似文献
109.
H Nagase S Imaide T Yamada S Hirayama T Nemoto N Yamaotsu S Hirono H Fujii 《Chemical & pharmaceutical bulletin》2012,60(8):945-948
On the basis of the three-dimensional pharmacophore model of opioid κ agonists, we simplified the structure of nalfurafine (selective κ agonist) to find the essential structural moieties for binding the opioid receptors, especially κ receptor type. As a result, we found that the trans-fused decahydroisoquinoline derivatives without a phenol ring bound the opioid receptor in micromolar order and that both the amide side chain and the nitrogen substituted by the cyclopropylmethyl group were indispensable moieties for eliciting the κ selectivity. The simple decahydroisoquinoline without amide side chain also bound the opioid receptor without receptor type selectivity, suggesting that the message-address concept would be applicable to even these simple derivatives. These findings that the simple decahydroisoquinoline derivatives showed the affinities for the opioid receptors, especially some of the compounds showed κ selectivity, are the first example in the opioid field. 相似文献
110.
Shusuke Yamanaka Keita Kanda Toru Saito Yasutaka Kitagawa Takashi Kawakami Masahiro Ehara Mitsutaka Okumura Haruki Nakamura Kizashi Yamaguchi 《Chemical physics letters》2012
We assessed the applicability and basis set dependency of the B3LYP functional to investigate magnetic interactions of Mn complexes. For the purpose, we constructed a test set consisting of 16 Mn complexes with various oxidation states and structural motifs.The B3LYP results correctly reproduced magnetism and magneto–redox correlation of the standard μ-oxo motifs with superexchange paths, while it does not work for weak magnetic complexes. We also showed that a modest basis set yields results similar to those of triple-zeta plus diffuse-and-polarization functions. This basis set is expected to be a standard basis set for investigating magnetism of manganese complexes. 相似文献