全文获取类型
收费全文 | 318篇 |
免费 | 3篇 |
国内免费 | 5篇 |
专业分类
系统科学 | 12篇 |
现状及发展 | 211篇 |
研究方法 | 12篇 |
综合类 | 91篇 |
出版年
2021年 | 3篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2013年 | 2篇 |
2012年 | 6篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2008年 | 8篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1974年 | 13篇 |
1973年 | 17篇 |
1972年 | 2篇 |
1971年 | 8篇 |
1970年 | 17篇 |
1969年 | 10篇 |
1968年 | 12篇 |
1967年 | 10篇 |
1966年 | 5篇 |
1965年 | 9篇 |
1964年 | 2篇 |
1963年 | 1篇 |
排序方式: 共有326条查询结果,搜索用时 15 毫秒
151.
1 Results Adsorption using commercial activated carbon (CAC)[1] can remove heavy metals from wastewater[2-4].However,CAC remains an expensive material for heavy metal removal.Ion exchange techniques are also used but it generates volumetric sludge and increases the cost[5].Using naturally occurring seed polysaccharides can solve these problems but their solubility in water limits its application as an adsorbent.Guar gum is a commercially available,industrially important[6-7] polysaccharide material havi... 相似文献
152.
Synthesis of Schiff bases of naphtha[1,2-d]thiazol-2-amine and metal complexes of 2-(2′-hydroxy)benzylideneaminonaphthothiazole as potential antimicrobial agents 下载免费PDF全文
Objective: A series of 2-benzylideneaminonaphthothiazoles were designed and synthesized incorporating the lipophilic naphthalene ring to render them more capable of penetrating various biomembranes. Methods: Schiff bases were synthesized by the reaction of naphtha[1,2-d]thiazol-2-amine with various substituted aromatic aldehydes. 2-(2′-Hydroxy)benzylideneaminonaphthothiazole was converted to its Co(II), Ni(II) and Cu(II) metal complexes upon treatment with metal salts in ethanol. All the compounds were evaluated for their antibacterial activities by paper disc diffusion method with Gram positive Staphylococcus aureus and Staphylococcus epidermidis and Gram negative Escherichia coli and Pseudomonas aeruginosa bacteria. The minimum inhibitory concentrations of all the Schiff bases and metal complexes were determined by agar streak dilution method. Results: All the compounds moderately inhibited the growth of Gram positive and Gram negative bacteria. In the present study among all Schiff bases 2-(2′-hydroxy)benzylideneaminonaphthothiazole showed maximum inhibitory activity and among metal complexes Cu(II) metal complex was found to be most potent. Conclusion: The results obtained validate the hypothesis that Schiff bases having substitution with halogens, hydroxyl group and nitro group at phenyl ring are required for the antibacterial activity while methoxy group at different positions in the aromatic ring has minimal role in the inhibitory activity. The results also indicated that the metal complexes are better antibacterial agents as compared to the Schiff bases. 相似文献
153.
Susan Westfall Nikita Lomis Imen Kahouli Si Yuan Dia Surya Pratap Singh Satya Prakash 《Cellular and molecular life sciences : CMLS》2017,74(20):3769-3787
The gut microbiota is essential to health and has recently become a target for live bacterial cell biotherapies for various chronic diseases including metabolic syndrome, diabetes, obesity and neurodegenerative disease. Probiotic biotherapies are known to create a healthy gut environment by balancing bacterial populations and promoting their favorable metabolic action. The microbiota and its respective metabolites communicate to the host through a series of biochemical and functional links thereby affecting host homeostasis and health. In particular, the gastrointestinal tract communicates with the central nervous system through the gut–brain axis to support neuronal development and maintenance while gut dysbiosis manifests in neurological disease. There are three basic mechanisms that mediate the communication between the gut and the brain: direct neuronal communication, endocrine signaling mediators and the immune system. Together, these systems create a highly integrated molecular communication network that link systemic imbalances with the development of neurodegeneration including insulin regulation, fat metabolism, oxidative markers and immune signaling. Age is a common factor in the development of neurodegenerative disease and probiotics prevent many harmful effects of aging such as decreased neurotransmitter levels, chronic inflammation, oxidative stress and apoptosis—all factors that are proven aggravators of neurodegenerative disease. Indeed patients with Parkinson’s and Alzheimer’s diseases have a high rate of gastrointestinal comorbidities and it has be proposed by some the management of the gut microbiota may prevent or alleviate the symptoms of these chronic diseases. 相似文献
154.
Electrical stimulation of hypothalamic areas through stereotaxically implanted electrodes were carried out in conscious male rhesus monkeys. There was a significant increase in immunoreactive insulin (IRI) following laterla hypothalamus (LHA) stimulation. An opposite response was obtained from ventromedial hypothalamus (VMH). Thus, insulinogenic and insulinoprival responses were obtained from feeding and satiety, suggesting a significant role of insulin in the regulation of food intake. 相似文献
155.
156.
157.
Vijay P.Singh 《北京师范大学学报(自然科学版)》2010,46(3)
借助Shannon熵和最大熵原理提出了熵理论,并基于此理论,提出了一种水文模拟方法,结合两个实例阐述了该方法在下渗和流速分布模拟中的应用. 相似文献
158.
Bulk material of (Se80Te20)100 xAgx (0rxr4) system was prepared by using a conventional
melt quenching technique. Thin films of a-(Se80Te20)100 xAgx (0rxr4) were deposited by the
vacuum evaporation technique at a base pressure of 10 4 mbar onto well-cleaned glass substrates.
Temperature dependence of electrical conductivity in the temperature range of 263–333 K has been
studied. There is increase in the value of conductivity with increase in temperature as well as with
Ag content. The measurements of intensity dependence of photoconductivity show that the photoconductivity
increases with intensity as a power law where the power is found to be between 0.5 and
1.0, representing the continuous distribution of traps. Rise and decay of photocurrent with time at
room temperature at different light intensities for (Se80Te20)98Ag2 thin film samples have also been
reported. The results have been explained on the basis of the Dember voltage and interaction between
photoexcited holes and the trapped electrons on the surface. 相似文献
159.
A. Shah F. Nagao V. Sahgal H. Singh 《Cellular and molecular life sciences : CMLS》1985,41(11):1396-1398
Summary The gastrocnemius muscle of the rat showed no morphological, histometric or plasma membrane changes, after sciatic nerve stimulation with a 5 mA current for 30 to 60 min, 10 mA for 30 min and 15 mA for 5 min. However, 10 mA for 60 and 200 min gave rise to mitochondrial and plasma membrane abnormalities. These changes were absent after a rest period. The results indicated the sciatic nerve stimulation at 10 mA for 60 and 200 min caused reversible changes in the rat skeletal muscle mitochondria and plasma membrane. 相似文献
160.
C Kaschka-Dierich A Adams T Lindahl G W Bornkamm G Bjursell G Klein B C Giovanella S Singh 《Nature》1976,260(5549):302-306
Tumour biopsies from Burkitt lymphoma patients, as well as human nasopharyngeal carcinoma cells growing in athymic mice, contain Epstein-Barr virus DNA as covalently closed circular DNA. In addition integrated viral DNA sequences seem to be present. 相似文献