全文获取类型
收费全文 | 1817篇 |
免费 | 91篇 |
出版年
2022年 | 11篇 |
2021年 | 33篇 |
2020年 | 19篇 |
2019年 | 13篇 |
2018年 | 40篇 |
2017年 | 32篇 |
2016年 | 52篇 |
2015年 | 77篇 |
2014年 | 79篇 |
2013年 | 85篇 |
2012年 | 130篇 |
2011年 | 141篇 |
2010年 | 86篇 |
2009年 | 57篇 |
2008年 | 88篇 |
2007年 | 102篇 |
2006年 | 94篇 |
2005年 | 66篇 |
2004年 | 91篇 |
2003年 | 78篇 |
2002年 | 64篇 |
2001年 | 30篇 |
2000年 | 29篇 |
1999年 | 31篇 |
1998年 | 13篇 |
1995年 | 12篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1989年 | 10篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 9篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1974年 | 10篇 |
1973年 | 23篇 |
1972年 | 14篇 |
1971年 | 13篇 |
1970年 | 15篇 |
1969年 | 8篇 |
1968年 | 13篇 |
1967年 | 13篇 |
1966年 | 8篇 |
排序方式: 共有1908条查询结果,搜索用时 265 毫秒
1.
2.
Acid-catalysed condensation of methyl β-d-glycero-l-manno-heptopyranoside with cyclohexanone yielded an approximately 3:1 mixture of the 2,3:6,7- and 2,3:4,7-di-O-cyclohexylideneheptosides (1 and 2), which could be separated either as their benzoates (3 and 4) or as their methyl ethers (5 and 6). The latter compounds afforded the 4- and 6-methyl ethers (7 and 8) of d-glycero-l-manno-heptitol. 相似文献
3.
A new algorithm is proposed to determine the type-II restrictionendonucleases' recognition site knowing the digested DNA sequenceand fragment lengths in an actual case. The algorithm is implementedfor the Commodore 64 microcomputer.
Received on January 6, 1987; accepted on June 19, 1987 相似文献
4.
Adding noise to a visual image makes object recognition more effortful and has a widespread effect on human electrophysiological responses. However, visual cortical processes directly involved in handling the stimulus noise have yet to be identified and dissociated from the modulation of the neural responses due to the deteriorated structural information and increased stimulus uncertainty in the case of noisy images. Here we show that the impairment of face gender categorization performance in the case of noisy images in amblyopic patients correlates with amblyopic deficits measured in the noise-induced modulation of the P1/P2 components of single-trial event-related potentials (ERP). On the other hand, the N170 ERP component is similarly affected by the presence of noise in the two eyes and its modulation does not predict the behavioral deficit. These results have revealed that the efficient processing of noisy images depends on the engagement of additional processing resources both at the early, feature-specific as well as later, object-level stages of visual cortical processing reflected in the P1 and P2 ERP components, respectively. Our findings also suggest that noise-induced modulation of the N170 component might reflect diminished face-selective neuronal responses to face images with deteriorated structural information. 相似文献
5.
6.
Judit Kapocsi George T. Somogyi Nandor Ludvig Peter Serfozo Laszlo G. Harsing Jr. Russell J. Woods E. Sylvester Vizi 《Neurochemical research》1987,12(2):141-147
Neurochemical and pharmacological evidence has been obtained that noradrenergic varicosities (in mouse and rat vas deferens) and cholinergic varicosities (in the Auerbach's plexus) contain heterogenous alpha2-adrenoceptors through which the release of [3H]noradrenaline and [3H]acetylcholine can be modulated. The quantitative data also support the hypothesis that different noradrenaline and xylazine sensitive alpha2-adrenoceptors are present prejunctionally in the vas deferens and Auerbach's plexus preparations. Prazosin, although it has a presynaptic inhibitory effect on alpha2-adrenoceptors of noradrenergic axon terminals, has no effect on cholinergic axon terminals. These data suggest that there are two different types of alpha2-adrenoceptors at the presynaptic axon terminals.Special Issue Dedicated to Dr. Abel Lajtha 相似文献
7.
8.
Fixed bacteria of the protein A-rich Cowan I Staphylococcus strain were labelled with fluorescein isothiocyanate and used as the second-step reagent in an indirect immunofluorescent assay of specific cell-surface antigen expression. The results are documented with fluorescence microscopy and flow cytometry. 相似文献
9.
Identification of positive and negative regulatory regions controlling expression of the cartilage matrix protein gene. 总被引:2,自引:1,他引:1
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
I Kiss Z B?sze P Szabó R Altanchimeg E Barta F Deák 《Molecular and cellular biology》1990,10(5):2432-2436
A complex pattern of regulation of the cartilage matrix protein gene was revealed by transient expression experiments. A minimal promoter from positions -15 to +64 functioned in chondrocytes and fibroblasts. An enhancer located in the first intron exerted chondrocyte-specific stimulation on the minimal promoter activity. The same fragment, however, had a negative effect in fibroblasts. Between -334 and -15, a silencer was found which inhibited the gene expression driven from its homologous as well as heterologous promoters both in chondrocytes and fibroblasts. Additional positive and negative control regions were mapped further upstream of the promoter. 相似文献
10.
Judit Barabás György Barabás István Szabó Marten Veenhuis Wim Harder 《Archives of microbiology》1988,150(2):105-108
Membrane-bound penicillin-binding proteins (PBPs) of two Streptomyces griseus strains that sporulate well in liquid and solid medium have been investigated during the course of their life-cycle. The PBP patterns were analyzed by sodium dodecylsulphate polyacrylamide-gel electrophoresis and fluorography. One strain (No. 45 H) has only a single band (mol wt: 27,000) in early log phase, and two additional PBPs of higher mol wt (69,000 and 80,000) in the late log phase. The other strain (No. 2682) possessed two bands with mol wts 27,000 and 38,000 which did not change during its vegetative phase. In strain No. 2682, a new PBP with a mol wt of 58,000 appeared in spore membranes while one of those (mol wt 38,000) present in mycelial membranes disappeared. Our results suggest that appearance of the new PBP in the spore may be associated with the sporulation process. The major PBP band (mol wt: 27,000) present in all stages of the life cycle of these strains, may be characteristic of S. griseus while the other PBPs reflect certain stages of the life cycle. A new method was developed for the production of spore protoplasts by consecutive enzymatic treatments.Abbreviation PBP
penicillin-binding protein 相似文献