全文获取类型
收费全文 | 3271篇 |
免费 | 261篇 |
国内免费 | 117篇 |
出版年
2023年 | 82篇 |
2022年 | 65篇 |
2021年 | 93篇 |
2020年 | 101篇 |
2019年 | 133篇 |
2018年 | 110篇 |
2017年 | 117篇 |
2016年 | 105篇 |
2015年 | 95篇 |
2014年 | 119篇 |
2013年 | 280篇 |
2012年 | 95篇 |
2011年 | 164篇 |
2010年 | 119篇 |
2009年 | 182篇 |
2008年 | 155篇 |
2007年 | 168篇 |
2006年 | 144篇 |
2005年 | 151篇 |
2004年 | 114篇 |
2003年 | 109篇 |
2002年 | 79篇 |
2001年 | 52篇 |
2000年 | 58篇 |
1999年 | 62篇 |
1998年 | 51篇 |
1997年 | 28篇 |
1996年 | 37篇 |
1995年 | 42篇 |
1994年 | 41篇 |
1993年 | 37篇 |
1992年 | 37篇 |
1991年 | 43篇 |
1990年 | 23篇 |
1989年 | 26篇 |
1988年 | 15篇 |
1987年 | 27篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 33篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 17篇 |
1980年 | 23篇 |
1979年 | 23篇 |
1978年 | 20篇 |
1977年 | 26篇 |
1976年 | 16篇 |
1975年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有3649条查询结果,搜索用时 15 毫秒
1.
Chemotaxonomic Screening of Seed Oils from the Family Saxifragaceae and Comparison with Data on Seed Oils from Grossulariaceae Obtained from Literature 下载免费PDF全文
Seeds of 25 members of the family Saxifragaceae, 1 × Astilbe, 1 × Darmera, 1 × Leptarrhena, 1 × Tellima, 3 × Mitella, and 18 × Saxifraga were investigated regarding oil content, as well as composition and content of fatty acids and vitamin E active compounds. The results were compared with results obtained from literature for members of the genus Ribes belonging to the closely related family Grossulariaceae to find chemometric differences between the different genera and between members of the family Saxifragaceae and Grossulariaceae, respectively. Members of the family Saxifragaceae are dominated by high amounts of linoleic and α‐linolenic acid which together account for about 80% of the total fatty acids. While α‐linolenic acid is characteristic for members of the genus Saxifraga, in other genera, linoleic acid is predominant. In comparison to members of the family Saxifragaceae members of the family Grossulariaceae also contain γ‐linolenic acid and stearidonic acid which allow a significant differentiation between both families. By principle component analysis, members of both families were divided into three distinct groups, i) species with a high content of α‐linolenic acid (genus Saxifraga), ii) species with high amounts of γ‐linolenic acid and stearidonic acid (genus Ribes), and iii) species with higher amounts of linoleic acid (other members of the family Saxifragaceae). The composition of the vitamin E active compounds was characterized by a high content of γ‐tocopherol in most members of the family Saxifragaceae, but no chemotaxonomic relevance. 相似文献
2.
P. David Josephy Jody J. Weadge Joseph Meissner Filomena Ng 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2008,654(1):64-68
Zero-valent nickel compounds are organometallic chemicals that are used in synthetic applications and may also occur as intermediates in nickel-catalyzed hydrogenation reactions used in food processing. Few studies have been performed on their possible genotoxic actions. We have tested two commercially available examples of this class of compounds. Solubility and stability were examined. Mutagenicity testing did not confirm a previous report that bis(1,5-cyclooctadiene)nickel is positive in the Ames assay. No stimulation of lipid peroxidation was observed in studies of bovine erythrocytes exposed in vitro. Our results do not indicate that zero-valent nickel compounds have genotoxic effects. 相似文献
3.
《Microbes and infection / Institut Pasteur》2015,17(2):109-117
Ebola virus infection can cause Ebola virus disease (EVD). Patients usually show severe symptoms, and the fatality rate can reach up to 90%. No licensed medicine is available. In this review, development of therapeutics for treatment of Ebola virus infection and EVD will be discussed. 相似文献
4.
From dilution series in defined mineral medium, a marine iregular coccoid methanogenic bacterium (strain MTP4) was isolated
that was able to grow on methanethiol as sole source of energy. The strain also grew on dimethylsulfide, mono-, di-, and trimethylamine,
methanol and acetate. On formate the organism produced methane without significant growth. Optimal growth on MT, with doubling
times of about 20 h, occurred at 30°C in marine medium. The isolate required p-aminobenzoate and a further not identified
vitamin. Strain MTP4 had a high tolerance to hydrogen sulfide but was very sensitive to mechanical forces or addition of detergents
such as Triton X-100 or sodium dodecylsulfate. Methanethiol was fermented by strain MTP4 according to the following equation:
相似文献
5.
《Bioorganic & medicinal chemistry》2019,27(12):2340-2344
A synthetic flavone derivative 2-(benzo[d][1,3]dioxol-5-yl)-4H-chromen-4-one (BDC) was synthesized by the one pot reaction method and assessed for α-glucosidase inhibitory activity. The BDC demonstrated dose dependent inhibition of α-glucosidase activity. A maximum inhibition (99.3 ± 0.26%) of α-glucosidase was observed at 27.6 µM. The maximum α-glucosidase inhibitory activity depicted by BDC 27.6 µM concentration was 22.4 fold over the maximum inhibition observed with acarbose (97.72 ± 0.59% at 669.57 µM), a standard commercial anti-diabetic drug. In contrast to acarbose that depicted competitive type inhibition, kinetic studies of α-glucosidase inhibition by BDC demonstrated non-competitive inhibition with Km of 0.71 mM−1 and a Vmax of 0.028 mmol/min. In silico studies suggest allosteric interaction of BDC with α-glucosidase at a minimum binding energy (ΔG) of −8.64 kcal/mol and Ki of 465.3 nM, whereas, acarbose interacted at the active site of α-glucosidase with ΔG of −9.23 kcal/mol and Ki of 172 nM. Thus BDC significantly inhibited α-glucosidase in comparison to acarbose. Moreover, BDC has been endorsed for drug likeness by evaluating it as per Lipinski rule of five. Thus, BDC can be a lead compound for the management of type-2 diabetes mellitus. 相似文献
6.
Ramaraj Sathasivam Ramalingam Radhakrishnan Abeer Hashem Elsayed F. Abd_Allah 《Saudi Journal of Biological Sciences》2019,26(4):709-722
Microalgae are one of the important components in food chains of aquatic ecosystems and have been used for human consumption as food and as medicines. The wide diversity of compounds synthesized from different metabolic pathways of fresh and marine water algae provide promising sources of fatty acids, steroids, carotenoids, polysaccharides, lectins, mycosporine-like amino acids, halogenated compounds, polyketides, toxins, agar agar, alginic acid and carrageenan. This review discusses microalgae used to produce biological substances and its economic importance in food science, the pharmaceutical industry and public health. 相似文献
7.
Cueva C Mingo S Muñoz-González I Bustos I Requena T del Campo R Martín-Álvarez PJ Bartolomé B Moreno-Arribas MV 《Letters in applied microbiology》2012,54(6):557-563
Aims: To investigate the effect of seven wine phenolic compounds and six oenological phenolic extracts on the growth of pathogenic bacteria associated with respiratory diseases (Pseudomonas aeruginosa, Staphylococcus aureus, Moraxella catarrhalis, Enterococcus faecalis, Streptococcus sp Group F, Streptococcus agalactiae and Streptococcus pneumoniae). Methods and Results: Antimicrobial activity was determined using a microdilution method and quantified as IC50. Mor. catarrhalis was the most susceptible specie to phenolic compounds and extracts. Gallic acid and ethyl gallate were the compounds that showed the greatest antimicrobial activity. Regarding phenolic extracts, GSE (grape seed extract) and GSE‐O (oligomeric‐rich fraction from GSE) were the ones that displayed the strongest antimicrobial effects. Conclusions: Results highlight the antimicrobial properties of wine phenolic compounds and oenological extracts against potential respiratory pathogens. The antimicrobial activity of wine phenolic compounds was influenced by the type of phenolic compounds. Gram‐negative bacteria were more susceptible than Gram‐positive bacteria to the action of phenolic compounds and extracts; however, the effect was species‐dependent. Significance and Impact of Study: The ability to inhibit the growth of respiratory pathogenic bacteria as shown by several wine phenolic compounds and oenological extracts warrants further investigations to explore the use of grape and wine preparations in oral hygiene. 相似文献
8.
《Bioorganic & medicinal chemistry letters》2014,24(7):1724-1729
A series of 11 novel amides of salinomycin were synthesized for the first time. All the obtained compounds were found to show potent antiproliferative activity against human cancer cell lines including the drug-resistant cancer cells. Four new salinomycin derivatives revealed good antibacterial activity against clinical isolates of methicillin-resistant Staphylococcus epidermidis (MRSE). 相似文献
9.
From the non-alkaloidal fractions of Delphinium venulosum, four known aromatic compounds cis and trans p-coumaric acids, p-hydroxybenzoic acid, protocatechuic acid methyl ester and a new aromatic compound 2,5,6-trihydroxypiperonylic acid methyl ester were isolated together with kaempferol, sitosterol and sitosteryl 3-glucoside. The structures of the compounds were established by spectral data. 相似文献
10.
M. A. C. Demeulemeester W. Rademacher A. Van de Mierop M. P. De Proft 《Plant Growth Regulation》1995,17(1):47-52
Root explants of chicory (Cichorium intybus L.) were cultured in vitro under continuous light or darkness. On a standard medium (no plant growth regulators added), flowering-stems were initiated under continuous light while under continuous dark, vegetative-stems were formed. Different types of GA (gibberellin) biosynthesis inhibitors were added to the culture medium. Paclobutrazol and compounds belonging to the group of cyclohexanetriones clearly reduced flowering-stem growth under light conditions and vegetative-stem growth under dark conditions. Under light conditions, flower bud initiation was not affected. These and other results suggest that GA1 may be synthesized during the in vitro culture period and that it controls flowering-stem growth but not floral initiation.Abbreviations CCC
chlormequat chloride
- GA
gibberellin
- LAB 198 999
3,5-dioxo-4-butyryl-cyclohexane carboxylic acid ethyl ester
- BAS 111..W
1-phenoxy-3-(1H-1,2,4-triazol-1-yl)-4-hydroxy-5,5-dimethylhexane 相似文献
|