全文获取类型
收费全文 | 6953篇 |
免费 | 437篇 |
国内免费 | 11篇 |
专业分类
7401篇 |
出版年
2024年 | 21篇 |
2023年 | 84篇 |
2022年 | 285篇 |
2021年 | 408篇 |
2020年 | 154篇 |
2019年 | 200篇 |
2018年 | 299篇 |
2017年 | 193篇 |
2016年 | 282篇 |
2015年 | 409篇 |
2014年 | 404篇 |
2013年 | 505篇 |
2012年 | 501篇 |
2011年 | 487篇 |
2010年 | 293篇 |
2009年 | 247篇 |
2008年 | 288篇 |
2007年 | 297篇 |
2006年 | 246篇 |
2005年 | 191篇 |
2004年 | 184篇 |
2003年 | 145篇 |
2002年 | 139篇 |
2001年 | 95篇 |
2000年 | 71篇 |
1999年 | 54篇 |
1998年 | 43篇 |
1997年 | 36篇 |
1996年 | 28篇 |
1995年 | 31篇 |
1994年 | 25篇 |
1993年 | 25篇 |
1992年 | 55篇 |
1991年 | 40篇 |
1990年 | 52篇 |
1989年 | 49篇 |
1988年 | 39篇 |
1987年 | 32篇 |
1986年 | 34篇 |
1985年 | 31篇 |
1984年 | 39篇 |
1983年 | 33篇 |
1982年 | 34篇 |
1981年 | 35篇 |
1980年 | 40篇 |
1979年 | 18篇 |
1978年 | 30篇 |
1977年 | 19篇 |
1974年 | 22篇 |
1973年 | 20篇 |
排序方式: 共有7401条查询结果,搜索用时 0 毫秒
51.
Mohamed Yara Ahmed Hassaneen H. M. El-Dessouky Mohamed A. Safwat Gehan Hassan Naglaa Abu-Mandil Amr Khalda 《Molecular biology reports》2021,48(7):5497-5502
Molecular Biology Reports - A cluster of many risk factors for type 2 diabetes and cardiovascular disease is used to describe the metabolic syndrome (MetS). Moreover, genetic differences associated... 相似文献
52.
Ahmed M. Elazzazy T.S. Abdelmoneim O.A. Almaghrabi 《Saudi Journal of Biological Sciences》2015,22(4):466-475
Twenty three morphologically distinct microbial colonies were isolated from soil and sea water samples, which were collected from Jeddah region, Saudi Arabia for screening of the most potent biosurfactant strains. The isolated bacteria were selected by using different methods as drop collapse test, oil displacement test, blue agar test, blood hemolysis test, emulsification activity and surface tension. The results showed that the ability of Virgibacillus salarius to grow and reduce surface tension under a wide range of pH, salinities and temperatures gives bacteria isolate an advantage in many applications such as pharmaceutical, cosmetics, food industries and bioremediation in marine environment. The biosurfactant production by V. salarius decreased surface tension and emulsifying activity (30 mN/m and 80%, respectively). In addition to reducing the production cost of biosurfactants by tested several plant-derived oils such as jatropha oil, castor oils, jojoba oil, canola oil and cottonseed oil. In this respect the feasibility to reusing old frying oil of sunflower for production rhamnolipids and sophorolipids, their use that lead to solve many ecological and industrial problems. 相似文献
53.
Dengue fever is the most prevalent arboviral disease in the tropical and sub-tropical regions of the world. The present report describes molecular detection and serotyping of dengue viruses in acute phase blood samples collected from New Delhi, India. Phylogenetic and molecular clock analysis of dengue virus serotype 1 and 3 strains were also investigated. Dengue virus infection was detected in 68.87% out of 604 samples tested by RT-PCR between 2011 & 2014. Dengue serotype 1 was detected in 25.48% samples, dengue serotype 2 in 79.56% samples and dengue serotype 3 in 11.29% samples. Dengue serotype 4 was not detected. Co-infection by more than one dengue serotype was detected in 18.26% samples. Envelope gene of 29 DENV-1 and 14 DENV-3 strains were sequenced in the study. All the DENV-1 strains grouped with the American African genotype. All DENV-3 strains were found to belong to Genotype III. Nucleotide substitution rates of dengue 1 and 3 viruses were determined in the study. Time to the most recent common ancestor (TMRCA) of dengue 1 viruses was determined to be 132 years. TMRCA of DENV-3 viruses was estimated to be 149 years. Bayesian skyline plots were constructed for Indian DENV-1 and 3 strains which showed a decrease in population size since 2005 in case of DENV- 1 strains while no change was observed in recent years in case of DENV-3 strains. The study also revealed a change in the dominating serotype in Delhi, India in recent years. The study will be helpful in formulating control strategies for the outbreaks. In addition, it will also assist in tracking the movement and evolution of this emerging virus. 相似文献
54.
Mansi Garg Resham L Gurung Sahar Mansoubi Jubed O Ahmed Anoushka Davé Felicity Z Watts Alessandro Bianchi 《EMBO reports》2014,15(8):871-877
Elongation of the telomeric overhang by telomerase is counteracted by synthesis of the complementary strand by the CST complex, CTC1(Cdc13)/Stn1/Ten1. Interaction of budding yeast Stn1 with overhang‐binding Cdc13 is increased by Cdc13 SUMOylation. Human and fission yeast CST instead interact with overhang‐binding TPP1/POT1. We show that the fission yeast TPP1 ortholog, Tpz1, is SUMOylated. Tpz1 SUMOylation restricts telomere elongation and promotes Stn1/Ten1 telomere association, and a SUMO‐Tpz1 fusion protein has increased affinity for Stn1. Our data suggest that SUMO inhibits telomerase through stimulation of Stn1/Ten1 action by Tpz1, highlighting the evolutionary conservation of the regulation of CST function by SUMOylation. 相似文献
55.
Dkhil Mohamed A. Abdel Moneim Ahmed E. Bauomy Amira A. Khalil Mona Al-Shaebi Esam M. Al-Quraishy Saleh 《Molecular biology reports》2020,47(2):1161-1171
Molecular Biology Reports - Arsenic is a potent and toxic heavy metal found in the environment that causes health problems, including liver disease, in humans and animals. Chlorogenic acid (CA) is... 相似文献
56.
Al-Shammari Ahmed Majeed Jalill Raghad Dhyea Abdul Hussein Mohammed F. 《Molecular biology reports》2020,47(3):1691-1702
Molecular Biology Reports - Phytotherapy has been used to treat a different type of diseases including cancer for a long time, and it was a source for different active anti-tumor agents. Oncolytic... 相似文献
57.
Ahmed Kamal M. Shaheer Malik Ahmad Ali Shaik Shaik Azeeza 《Journal of Molecular Catalysis .B, Enzymatic》2009,58(1-4):132-137
A simple and efficient method for the synthesis of optically active γ-azidoalcohols is described. The lipase catalyzed kinetic resolutions of acetates of γ-azidoalcohols in aqueous as well as organic media have been studied. The enantiomerically pure γ-azidoalcohols obtained by the kinetic resolution in high enantiopurity have been utilized towards the synthesis of enantiomeric pairs of anti-depressant drugs, fluoxetine and duloxetine. 相似文献
58.
During murine embryonic development, primitive hematopoiesis occurs in the yolk sac (YS). Recent studies have shown that the YS also harbors definitive hematopoietic activity. However, the population of YS cells contributing to definitive hematopoiesis has not been identified. In this study, we characterized the hematopoietic cell populations in the YS of mouse embryos from E9.5 to E14.5 in view of the expression profiles of CD45 and c-Kit. The YS cells from E9.5 to E11.5 could be divided into six populations: CD45(-) c-Kit(-) , CD45(-) c-Kit(low) , CD45(-) c-Kit(high) , CD45(low) c-Kit(high) , CD45(high) c-Kit(high) and CD45(high) c-Kit(very low) . Among these populations, CD45(low) c-Kit(high) cells showed the highest multilineage hematopoietic colony-forming activity. Later in development, the YS cells from E12.5 to E14.5 lost the second and fourth populations (i.e., they retained CD45(-) c-Kit(-) , CD45(-) c-Kit(high) , CD45(high) c-Kit(high) and CD45(high) c-Kit(very low) cells), and concurrently with the disappearance of the CD45(low) c-Kit(high) population, no significant hematopoietic activity was found in any of the populations on and after E12.5. CD45(low) c-Kit(high) YS cells, which had a round morphology with a large nucleus, possessed the ability to differentiate into myeloid and B lymphoid cells when cultured with stromal cells. These findings suggest that CD45(low) c-Kit(high) YS cells include more undifferentiated cells than the other YS cell populations and possess in vitro potency to differentiate into multilineage hematopoietic cells. Furthermore, this cell population disappears from the YS at around E12.5, when the site of hematopoiesis has already shifted to the fetal liver and the placenta. 相似文献
59.
Mukhtar Ahmed Daoud Ali Abdel Halim Harrath Tajamul Hussain Nasser Al-Daghri Majed S. Alokail Ravindranath H. Aladakatti Mukhtar Ahmed G. Ghodesawar 《Comptes rendus biologies》2014,337(4):250-257
Boswellia papyrifera and Boswellia carterii diffuses smoke polluting air that adversely affects indoor environment that certainly harm human health. Therefore, this study aims at ascertaining the effect of these plants on gonadal hormones and molecular changes in rat spermatozoa. The animals were exposed to 4 g/kg body weight of B. papyrifera and B. carterii daily for 120 days along with suitable controls. Significant decreases in FSH, LH and testosterone levels were evidenced, along with a reduction of protein, sialic acid, and carnitine levels. In sperm physiology, sperm count, motility, speed decrease, whereas sperm anomalies increase. TEM observation indicates morphological changes in plasma and acrosomal membranes, cytoplasmic droplet in the tail region, vacuolated, and disorganization of the mitochondrial sheath. These findings demonstrate that B. papyrifera and B. carterii smoke affects the process of sperm formation and maturation, which indicates the detrimental effects of these plants on the reproductive system. 相似文献
60.
Ibrar Ahmed Peter J. Lockhart Esperanza M. G. Agoo Kyaw W. Naing Dzu V. Nguyen Dilip K. Medhi Peter J. Matthews 《Ecology and evolution》2020,10(23):13530
As an ancient clonal root and leaf crop, taro (Colocasia esculenta, Araceae) is highly polymorphic with uncertain genetic and geographic origins. We explored chloroplast DNA diversity in cultivated and wild taros, and closely related wild taxa, and found cultivated taro to be polyphyletic, with tropical and temperate clades that appear to originate in Southeast Asia sensu lato. A third clade was found exclusively in wild populations from Southeast Asia to Australia and Papua New Guinea. Our findings do not support the hypothesis of taro domestication in Papua New Guinea, despite archaeological evidence for early use or cultivation there, and the presence of apparently natural wild populations in the region (Australia and Papua New Guinea). 相似文献