全文获取类型
收费全文 | 36028篇 |
免费 | 361篇 |
国内免费 | 277篇 |
专业分类
化学 | 14195篇 |
晶体学 | 307篇 |
力学 | 1525篇 |
综合类 | 12篇 |
数学 | 10580篇 |
物理学 | 10047篇 |
出版年
2021年 | 116篇 |
2020年 | 135篇 |
2019年 | 104篇 |
2018年 | 1355篇 |
2017年 | 1622篇 |
2016年 | 1103篇 |
2015年 | 803篇 |
2014年 | 760篇 |
2013年 | 1322篇 |
2012年 | 3457篇 |
2011年 | 2736篇 |
2010年 | 2056篇 |
2009年 | 1751篇 |
2008年 | 766篇 |
2007年 | 760篇 |
2006年 | 708篇 |
2005年 | 4494篇 |
2004年 | 3984篇 |
2003年 | 2389篇 |
2002年 | 587篇 |
2001年 | 383篇 |
2000年 | 170篇 |
1999年 | 265篇 |
1998年 | 199篇 |
1997年 | 159篇 |
1996年 | 123篇 |
1995年 | 124篇 |
1994年 | 115篇 |
1993年 | 92篇 |
1992年 | 245篇 |
1991年 | 217篇 |
1990年 | 190篇 |
1989年 | 167篇 |
1988年 | 167篇 |
1987年 | 127篇 |
1986年 | 111篇 |
1985年 | 130篇 |
1984年 | 114篇 |
1983年 | 106篇 |
1981年 | 93篇 |
1980年 | 98篇 |
1979年 | 108篇 |
1978年 | 109篇 |
1977年 | 106篇 |
1976年 | 145篇 |
1975年 | 90篇 |
1974年 | 113篇 |
1973年 | 126篇 |
1969年 | 89篇 |
1966年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
I Cserpan M Kalman M L Tj?rnhammar A Simoncsits 《Acta chemica Scandinavica (Copenhagen, Denmark : 1989)》1991,45(3):265-272
A general method to convert single-stranded, chemically synthesized oligonucleotides into cloned duplexes is described. Oligonucleotides supplied with 3'-terminal extensions that are complementary to 3'-protruding ends obtained by certain restriction enzymes can be cloned either directly or with the help of an adapter molecule into double-stranded vectors. Two methods have also been developed for consecutive cloning applications. According to these methods, the synthetic oligonucleotides (and their enzymatically prepared complementary strands) are joined, one after the other, inside a cloning vector, each joining requiring one cloning step. Synthetic genes are thus built up from oligonucleotides corresponding to only one strand of the DNA. The sequential assembly of the cloned duplex takes place in the 5' to 3' direction. Each oligonucleotide is supplied with a four-nucleotide-long 3'-terminal extension, but this sequence is eliminated when the joining takes place, leaving no limiting sequence between the oligonucleotides. The two consecutive cloning methods, the adapter and the polycloning site methods, are illustrated by the assembly of short artificial genes. 相似文献
92.
K. Prokeš 《Czechoslovak Journal of Physics》2002,52(2):253-258
Many materials exhibit various magnetic phenomena as a function of magnetic field, temperature and/or pressure. Usually, bulk magnetic measurements provide first information on the magnetic state of the material by measuring their response on the applied magnetic field. However, it is necessary to investigate materials also on a microscopic scale. This is often done by means of neutron scattering. In this contribution we discuss basic ideas of this method and we report on few experimental results obtained with a split-pair coil 14.5 T superconducting magnet which can be combined with dilution stick offering temperatures as low as 30 mK and/or with a small clamped-type pressure cell which offers pressure up to 1.0 GPa. 相似文献
93.
We have investigated the structure of spider dragline silk by X-ray diffraction over a broad temperature range from room temperature
up to thermal denaturation conditions. The dominating signal from the β-sheet crystallites is analyzed. Pronounced changes
of scattering intensity starting at temperatures around 150 °C are observed. These changes are discussed in view of the respective
lattice constants, crystal size, size distribution, crystallite number density and amino acid composition.
PACS 87.68.+z; 87.15.-v; 87.64.Bx 相似文献
94.
Andrzej Wi?nicki 《Journal of Mathematical Analysis and Applications》2002,267(1):158-172
We use a newly introduced concept of neocompactness to study problems from metric fixed point theory. In particular, we give a sufficient condition for a superreflexive Banach space X to have the fixed point property and obtain shorter proofs of some well-known results in that theory. 相似文献
95.
96.
The validity of local parton-hadron duality within the framework of HERWIG and JETSET event generators is investigated. We concentrate one
+
e
– annihilations in LEP 2 energy range as these interactions provide theoretically the cleanest condition for the discussion of this concept. We conclude that the concept of local parton-hadron duality is not valid in either of the two generators considered. 相似文献
97.
Š. Jakševičius 《Lithuanian Mathematical Journal》1992,32(2):174-180
Kaunas Academy of Agriculture, 4324 Noreikiškés, Lithuania. Translated from Lietuvos Matematikos Rinkinys, Vol. 32, No. 2,
pp. 221–228, April–June, 1992. 相似文献
98.
In vitro and in vivo proton T1 data are reported that demonstrate that the paramagnetic copper-D-penicillamine complex can be applied as a potential contrast agent to magnetic resonance imaging. 相似文献
99.
T Christensen E B Jensen F Junker H Dalb?ge F Abildgaard J J Led 《Acta chemica Scandinavica (Copenhagen, Denmark : 1989)》1992,46(1):97-99
Biosynthetic human growth hormone specifically 13C-labelled in the carbonyl positions of all 26 leucine residues has been obtained by recombinant DNA techniques using 13C-labelled leucine and an E. coli strain that requires leucine. It is shown that, on the whole, the labelling is specific with no significant mislabelling as would have been the case had the 13C-labelled leucine been metabolized. 相似文献
100.
L Jirovetz G Buchbauer W J?ger A Woidich A Nikiforov 《Biomedical chromatography : BMC》1992,6(3):133-134
After inhalation experiments with sandalwood oil and the pure fragrance compounds coumarin and alpha-terpineol, substances were detected and measured in the blood samples of test animals (mice) using gas chromatography/mass spectrometry (GC/MS) (MID) in connection with GC/FTIR (SWC), GC/AES (carbon and oxygen trace) and flame ionization detection/gas chromatography. Using tiglinic acid benzyl ester as the internal standard the following concentrations in serum could be found: alpha-santalol 6.1 ng/mL, beta-santalol 5.3 ng/mL and alpha-santalene 0.5 ng/mL. In separate inhalation experiments with coumarin and with alpha-terpineol the corresponding concentrations were 7.7 ng/mL and 6.9 ng/mL, respectively. 相似文献