全文获取类型
收费全文 | 2421篇 |
免费 | 148篇 |
国内免费 | 1篇 |
出版年
2024年 | 7篇 |
2023年 | 35篇 |
2022年 | 57篇 |
2021年 | 125篇 |
2020年 | 54篇 |
2019年 | 63篇 |
2018年 | 91篇 |
2017年 | 69篇 |
2016年 | 108篇 |
2015年 | 114篇 |
2014年 | 121篇 |
2013年 | 176篇 |
2012年 | 161篇 |
2011年 | 167篇 |
2010年 | 98篇 |
2009年 | 88篇 |
2008年 | 106篇 |
2007年 | 99篇 |
2006年 | 94篇 |
2005年 | 84篇 |
2004年 | 87篇 |
2003年 | 68篇 |
2002年 | 59篇 |
2001年 | 44篇 |
2000年 | 33篇 |
1999年 | 22篇 |
1998年 | 26篇 |
1997年 | 18篇 |
1996年 | 10篇 |
1995年 | 19篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1974年 | 10篇 |
1973年 | 10篇 |
1969年 | 9篇 |
1968年 | 6篇 |
排序方式: 共有2570条查询结果,搜索用时 17 毫秒
911.
Essam H. Ibrahim Mona Kilany Osama M.S. Mostafa Kamel H. Shaker Mohammed Alshehri Khalid M. Alsyaad Ali Alshehri Khalid Ali Khan Muhammad Qasim Nahla Kotb Abeer S. Alahmari Hamed A. Ghramh Saad M. Dajem 《Saudi Journal of Biological Sciences》2019,26(7):1716-1723
Natural products, including their purified materials, play a remarkable role in drug development. The Euphorbiaceae family, mainly Euphorbia tirucalli, is used in some traditional medicine, and has evidence that its latex comprises immunomodulatory properties and cytokine production. This study aimed to measure the in vivo production of chemokines (IL-1α, IL-1β, IL-12, and RANTES), TH1 cytokines (IFN-γ, TNF-α, GM-CSF, and IL-2) and TH2 cytokines (IL-4, IL-6, IL-10, and IL-13) in rats after treatments with ethanol latex extract of E. tirucalli. Vaccine treated and untreated rats were divided into seven groups to assess antimicrobial activities of the extracted components. After completion of the treatment schedule, blood was withdrawn and sera were collected. The results showed that the main component of the extract was a euphol compound. The extract showed antimicrobial activity and had the ability to modulate innate and adaptive immunity. Animals treated with extract for only 7 days before vaccination showed higher levels of antibody production. The extract showed antibacterial and antifungal activities. The extract could stimulate both adaptive and innate immunity. Pre-treatment with the extract increased immune responses in vaccinated animals, indicating the usefulness of the extract before immunization. 相似文献
912.
Idris Adewale Ahmed Maryam Abimbola Mikail Mohammad Rais Mustafa Muhammad Ibrahim Rozana Othman 《Saudi Journal of Biological Sciences》2019,26(7):1519-1524
Non-alcoholic fatty liver disease (NAFLD) is a multi-factorial disease and the most common of chronic liver diseases worldwide. The four clinical-pathological entities which are usually followed by NAFLD course include non-alcoholic steatosis, non-alcoholic steatohepatitis, advanced fibrosis/cirrhosis, and hepatocellular carcinoma. The cornerstones of NAFLD management and treatment, however, are healthy lifestyles such as dietary modifications, regular physical activity, and gradual weight loss. At present, no drugs or pharmacological agents have been approved for long-term treatment of NAFLD. Therefore, lifestyle modification is considered the main clinical recommendation and an initial step for the management of NAFLD. 相似文献
913.
Abd El-Halim A. Saad Fawzy M. A. Ragab Hesham M. Abdel Fatah Nevine K. Ibrahim 《Molluscan research.》2019,39(1):82-88
Controlling the snail intermediate host of schistosomiasis is one of the strategies used to reduce disease incidence. In this study screening tests were carried out on the action of dried powder of eight algal species against Biomphalaria alexandrina snails. The most effective powders were from Dictyota dichotoma and Cystoseira barbata with LC50 values of 560 and 2200?ppm, respectively. Prolonged exposure to sublethal concentrations of these two powders caused adverse effects on snails' reproduction especially at LC25. Hatchability of exposed eggs was lowest at LC25 of C. barbata, and LC15 of D. dichotoma. The most pronounced effects on the hermaphrodite gland of snails were caused by high concentrations of both algal suspensions, where ova were either degenerated or deformed and there were detrimental effects on all spermatogenesis stages. The electrophoretic separation of haemolymph proteins showed that the concentration with most effect was the LC15 for both tested algae as they resulted in more bands than the control and also an elevation in total protein content. 相似文献
914.
Lily G. C. Genevier Tahira Jamil Dionysios E. Raitsos George Krokos Ibrahim Hoteit 《Global Change Biology》2019,25(7):2338-2351
As the Earth's temperature continues to rise, coral bleaching events become more frequent. Some of the most affected reef ecosystems are located in poorly monitored waters, and thus, the extent of the damage is unknown. We propose the use of marine heatwaves (MHWs) as a new approach for detecting coral reef zones susceptible to bleaching, using the Red Sea as a model system. Red Sea corals are exceptionally heat‐resistant, yet bleaching events have increased in frequency. By applying a strict definition of MHWs on >30 year satellite‐derived sea surface temperature observations (1985–2015), we provide an atlas of MHW hotspots over the Red Sea coral reef zones, which includes all MHWs that caused major coral bleaching. We found that: (a) if tuned to a specific set of conditions, MHWs identify all areas where coral bleaching has previously been reported; (b) those conditions extended farther and occurred more often than bleaching was reported; and (c) an emergent pattern of extreme warming events is evident in the northern Red Sea (since 1998), a region until now thought to be a thermal refuge for corals. We argue that bleaching in the Red Sea may be vastly underrepresented. Additionally, although northern Red Sea corals exhibit remarkably high thermal resistance, the rapidly rising incidence of MHWs of high intensity indicates this region may not remain a thermal refuge much longer. As our regionally tuned MHW algorithm was capable of isolating all extreme warming events that have led to documented coral bleaching in the Red Sea, we propose that this approach could be used to reveal bleaching‐prone regions in other data‐limited tropical regions. It may thus prove a highly valuable tool for policymakers to optimize the sustainable management of coastal economic zones. 相似文献
915.
Mathieu Coureuil Anne Jamet Emmanuelle Bille Herv Lcuyer Sandrine Bourdoulous Xavier Nassif 《Cellular microbiology》2019,21(11)
Neisseria meningitidis is a Gram‐negative bacterium that asymptomatically colonises the nasopharynx of humans. For an unknown reason, N. meningitidis can cross the nasopharyngeal barrier and invade the bloodstream where it becomes one of the most harmful extracellular bacterial pathogen. This infectious cycle involves the colonisation of two different environments. (a) In the nasopharynx, N. meningitidis grow on the top of mucus‐producing epithelial cells surrounded by a complex microbiota. To survive and grow in this challenging environment, the meningococcus expresses specific virulence factors such as polymorphic toxins and MDAΦ. (b) Meningococci have the ability to survive in the extra cellular fluids including blood and cerebrospinal fluid. The interaction of N. meningitidis with human endothelial cells leads to the formation of typical microcolonies that extend overtime and promote vascular injury, disseminated intravascular coagulation, and acute inflammation. In this review, we will focus on the interplay between N. meningitidis and these two different niches at the cellular and molecular level and discuss the use of inhibitors of piliation as a potent therapeutic approach. 相似文献
916.
Saleem Esmael Shahbaz Jihad Ibrahim Saleem Shamiran Salih Abdulrahman 《Nordic Journal of Botany》2015,33(1):50-56
Rhus coriaria var. zebaria from Duhok/Aqrae, Kurdistan, Iraq is described as a variety new to science. Field expeditions started in spring 2011, continued during 2012 and 2013 with the aim of collecting sumac specimens from different physiographic regions of Kurdistan, Iraq. A total of ten plants for each variety were sampled. An equal number of tagged herbarium specimens were prepared. The holotype was designated and deposited together with other herbarium specimens in the herbarium of the Faculty of Agriculture and Forestry, Univ. of Duhok. Morphological characters of the leaf, inflorescence, flowers, infructescence, and fruit were studied. The pH value of the pericarp in addition to the hilum length was measured. Results were compared with Rhus coriaria L. var. coriaria. The most distinctive feature of the new variety is the dull whitish brown color of the drupe pericarp of var. zebaria as compared to the reddish brown color of the drupe pericarp of var. coriaria. The whitish color of the drupes of var. zebaria, in combination with their larger size, represents diagnostic characters for distinguishing this variety. In contrast, most leaf characters are of little or no taxonomic value in this species. Only shape, apex and marginal teeths of the leaflets show minor differences for separating the two varieties. Female and male inflorescences and flowers characters show no significant differences. Both hilum length and pH value characters may be useful for taxonomic application if mean values are taken in consideration. 相似文献
917.
Julia Wallmeier Diana Bracht Hessa S. Alsaif Gerard W. Dougherty Heike Olbrich Sandra Cindric Mark Dzietko Christoph Heyer Norbert Teig Charlotte Thiels Eissa Faqeih Aqeela Al-Hashim Sameena Khan Ibrahim Mogarri Mohammed Almannai Wadha Al Otaibi Fowzan S. Alkuraya Cordula Koerner-Rettberg Heymut Omran 《American journal of human genetics》2021,108(7):1318-1329
918.
919.
Effective population size, levels of genetic diversity, gene flow, and genetic structuring were assessed in 205 colonial Roseate spoonbills from 11 breeding colonies from north, central west, and south Brazil. Colonies and regions exhibited similar moderate levels of diversity at five microsatellite loci (mean expected heterozygosity range 0.50–0.62; allelic richness range 3.17–3.21). The central west region had the highest Ne (59). F ST values revealed low but significant genetic structuring among colonies within the north and within the south regions. Significant global genetic structuring was found between the northern and central western populations as well as between the northern and southern populations. An individual-based Bayesian clustering method inferred three population clusters. Assignment tests correctly allocated up to 64% of individuals to their source regions. Collectively, results revealed complex demographic dynamics, with ongoing gene flow on a local scale, but genetic differentiation on a broader scale. Populations in the three regions may all be conserved, but special concern should be given to central western ones, which can significantly contribute to the species’ gene pool in Brazil. 相似文献
920.
Alexandra J. Candasamy Robert S. Haworth Friederike Cuello Michael Ibrahim Sriram Aravamudhan Marcus Krüger Mark R. Holt Cesare M. N. Terracciano Manuel Mayr Mathias Gautel Metin Avkiran 《The Journal of biological chemistry》2014,289(3):1282-1293
Telethonin (also known as titin-cap or t-cap) is a muscle-specific protein whose mutation is associated with cardiac and skeletal myopathies through unknown mechanisms. Our previous work identified cardiac telethonin as an interaction partner for the protein kinase D catalytic domain. In this study, kinase assays used in conjunction with MS and site-directed mutagenesis confirmed telethonin as a substrate for protein kinase D and Ca2+/calmodulin-dependent kinase II in vitro and identified Ser-157 and Ser-161 as the phosphorylation sites. Phosphate affinity electrophoresis and MS revealed endogenous telethonin to exist in a constitutively bis-phosphorylated form in isolated adult rat ventricular myocytes and in mouse and rat ventricular myocardium. Following heterologous expression in myocytes by adenoviral gene transfer, wild-type telethonin became bis-phosphorylated, whereas S157A/S161A telethonin remained non-phosphorylated. Nevertheless, both proteins localized predominantly to the sarcomeric Z-disc, where they partially replaced endogenous telethonin. Such partial replacement with S157A/S161A telethonin disrupted transverse tubule organization and prolonged the time to peak of the intracellular Ca2+ transient and increased its variance. These data reveal, for the first time, that cardiac telethonin is constitutively bis-phosphorylated and suggest that such phosphorylation is critical for normal telethonin function, which may include maintenance of transverse tubule organization and intracellular Ca2+ transients. 相似文献