全文获取类型
收费全文 | 3219篇 |
免费 | 256篇 |
国内免费 | 1篇 |
专业分类
3476篇 |
出版年
2023年 | 15篇 |
2022年 | 40篇 |
2021年 | 73篇 |
2020年 | 46篇 |
2019年 | 61篇 |
2018年 | 68篇 |
2017年 | 60篇 |
2016年 | 108篇 |
2015年 | 148篇 |
2014年 | 172篇 |
2013年 | 220篇 |
2012年 | 237篇 |
2011年 | 245篇 |
2010年 | 142篇 |
2009年 | 142篇 |
2008年 | 182篇 |
2007年 | 188篇 |
2006年 | 187篇 |
2005年 | 163篇 |
2004年 | 169篇 |
2003年 | 132篇 |
2002年 | 141篇 |
2001年 | 35篇 |
2000年 | 19篇 |
1999年 | 39篇 |
1998年 | 45篇 |
1997年 | 30篇 |
1996年 | 29篇 |
1995年 | 28篇 |
1994年 | 34篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 31篇 |
1990年 | 20篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有3476条查询结果,搜索用时 0 毫秒
111.
Margherita Conchedda Antonello Antonelli Aldo Caddori Flavio Gabriele 《Parasitology international》2010,59(3):454-459
To assess the current impact of human CE in Sardinia (Italy) and to monitor the changes over time, a survey has been carried out for the period 2001–2005 using hospital inpatient discharge reports (HDR) as information source, supplementing data wherever possible with additional information retrieved directly from medical records. The total of 726 admissions with “Echinococcosis” as primary diagnosis (annual rate of 8.9 per 100,000 inhabitants) concerned 540 CE cases with an annual mean incidence rate of 6.62 per 100,000 inhabitants. Male-to-female ratio was 1.36, suggesting a marked risk associated with traditional male occupations. Age-specific incidence showed increasing rates of clinical CE with age for both genders. The liver was found to be the most common localization, affecting 72% of patients, while pulmonary CE was more frequent in males than in females. CE risk was unevenly distributed in the island. The more pastoral areas had the highest probability of humans becoming infected, with an incidence rate of clinical cases of ~ 14.0 per 100,000 for areas with sheep/inhabitants index of > 6. Compared to the past, incidence rates appear to be decreasing both for pulmonary and hepatic localizations, while there is a reversal of the CE “urbanization” trend resulting in “ruralization”, accompanied by a greater degree of parasite ecological “isolation” and focus-points of infection risk. In spite of this decrease, the cost of hospital care alone (~4 million euros) suggests that the monetary plus non-monetary costs of CE are still very high but not fully recognised. 相似文献
112.
Michele Tonelli Matteo Simone Bruno Tasso Federica Novelli Vito Boido Fabio Sparatore Giuseppe Paglietti Sabrina Pricl Gabriele Giliberti Sylvain Blois Cristina Ibba Giuseppina Sanna Roberta Loddo Paolo La Colla 《Bioorganic & medicinal chemistry》2010,18(8):2937-2953
Seventy-six 2-phenylbenzimidazole derivatives were synthesized and evaluated in cell-based assays for cytotoxicity and antiviral activity against a panel of 10 RNA and DNA viruses. The most commonly affected viruses were, in decreasing order, CVB-2, BVDV, Sb-1, HSV-1, and YFV, while HIV-1 and VSV were not affected, and RSV, VV and Reo-1 were only susceptible to a few compounds. Thirty-nine compounds exhibited high activity (EC50 = 0.1–10 μM) against at least one virus, and four of them were outstanding for their high and selective activity against VV (24, EC50 = 0.1 μM) and BVDV (50, 51, and 53 with EC50 = 1.5, 0.8, and 1.0 μM, respectively). The last compounds inhibited at low micromolar concentrations the NS5B RdRp of BVDV and also of HCV, the latter sharing structural similarity with the former. The considered compounds represent attractive leads for the development of antiviral agents against poxviruses, pestiviruses and even HCV, which are important human and veterinary pathogens. 相似文献
113.
The Dof protein DAG1 mediates PIL5 activity on seed germination by negatively regulating GA biosynthetic gene AtGA3ox1 总被引:2,自引:0,他引:2
114.
Mitogen-Activated Protein Kinase-Activated Kinase RSK2 Plays a Role in Innate Immune Responses to Influenza Virus Infection 下载免费PDF全文
115.
The Cyanidiales is a group of asexual, unicellular red algae, which thrive in acidic and high temperature conditions around hot springs. These unicellular taxa have a relatively simple morphology and are currently classified into three genera, Cyanidium, Cyanidioschyzon and Galdieria. Little is known, however, about the biodiversity of Cyanidiales, their population structure and their phylogenetic relationships. Here we used a taxonomically broadly sampled three-gene data set of plastid sequences to infer a robust phylogenetic framework for the Cyanidiales. The phylogenetic analyses support the existence of at least four distinct Cyanidiales lineages: the Galdieria spp. lineage (excluding Galdieria maxima), the Cyanidium caldarium lineage, a novel monophyletic lineage of mesophilic Cyanidium spp. and the Cyanidioschyzon merolae plus Galdieria maxima lineage. Our analyses do not support the notion of a mesophilic ancestry of the Cyanidiales and suggest that these algae were ancestrally thermo-acidotolerant. We also used environmental polymerase chain reaction (PCR) for the rbcL gene to sample Cyanidiales biodiversity at five ecologically distinct sites at Pisciarelli in the Phlegrean Fields in Italy. This analysis showed a high level of sequence divergence among Cyanidiales species and the partitioning of taxa based on environmental conditions. Our research revealed an unexpected level of genetic diversity among Cyanidiales that revises current thinking about the phylogeny and biodiversity of this group. We predict that future environmental PCR studies will significantly augment known biodiversity that we have discovered and demonstrate the Cyanidiales to be a species-rich branch of red algal evolution. 相似文献
116.
Hendrik Greve Ietidal E. Mohamed Alexander Pontius Stefan Kehraus Harald Gross Gabriele M. König 《Phytochemistry Reviews》2010,9(4):537-545
Natural products play an important role in the development of anticancer drugs. To date, predominantly metabolites from plants
and bacteria served as lead structures for anticancer agents. Fungal metabolites and derivatives thereof are much less investigated
for their potential in cancer therapy. There are, however, some promising candidates derived from fungi in clinical phases
I and II studies. This review gives an overview on the role of natural products in cancer therapy and summarises some of the
latest results of our group in this area. 相似文献
117.
118.
Huaiwei Liu Yuanzhang Sun Kristine Rose M. Ramos Grace M. Nisola Kris Ni?o G. Valdehuesa Won–Keun Lee Si Jae Park Wook-Jin Chung 《PloS one》2013,8(12)
Embden-Meyerhof pathway (EMP) in tandem with 2-C-methyl-D-erythritol 4-phosphate pathway (MEP) is commonly used for isoprenoid biosynthesis in E. coli. However, this combination has limitations as EMP generates an imbalanced distribution of pyruvate and glyceraldehyde-3-phosphate (G3P). Herein, four glycolytic pathways—EMP, Entner-Doudoroff Pathway (EDP), Pentose Phosphate Pathway (PPP) and Dahms pathway were tested as MEP feeding modules for isoprene production. Results revealed the highest isoprene production from EDP containing modules, wherein pyruvate and G3P were generated simultaneously; isoprene titer and yield were more than three and six times higher than those of the EMP module, respectively. Additionally, the PPP module that generates G3P prior to pyruvate was significantly more effective than the Dahms pathway, in which pyruvate production precedes G3P. In terms of precursor generation and energy/reducing-equivalent supply, EDP+PPP was found to be the ideal feeding module for MEP. These findings may launch a new direction for the optimization of MEP-dependent isoprenoid biosynthesis pathways. 相似文献
119.
120.
Hofmann U Maier K Niebel A Vacun G Reuss M Mauch K 《Biotechnology and bioengineering》2008,100(2):344-354
An experimental set-up for acquiring metabolite and transient (13)C-labeling data in mammalian cells is presented. An efficient sampling procedure was established for hepatic cells cultured in six-well plates as a monolayer attached to collagen, which allowed simultaneous quenching of metabolism and extraction of the intracellular intermediates of interest. Extracellular concentrations of glucose, amino acids, lactate, pyruvate, and urea were determined by GC-MS procedures and were used for estimation of metabolic uptake and excretion rates. Sensitive LC-MS and GC-MS methods were used to quantify the intracellular intermediates of tricarboxylic acid cycle, glycolysis, and pentose phosphate pathway and for the determination of isotopomer fractions of the respective metabolites. Mass isotopomer fractions were determined in a transient (13)C-labeling experiment using (13)C-labeled glucose as substrate. The absolute amounts of intracellular metabolites were obtained from a non-labeled experiment carried out in exactly the same way as the (13)C-labeling experiment, except that the media contained naturally labeled glucose only. Estimation of intracellular metabolic fluxes from the presented data is addressed in part II of this contribution. 相似文献