全文获取类型
收费全文 | 6887篇 |
免费 | 442篇 |
国内免费 | 11篇 |
专业分类
7340篇 |
出版年
2024年 | 20篇 |
2023年 | 81篇 |
2022年 | 277篇 |
2021年 | 405篇 |
2020年 | 152篇 |
2019年 | 190篇 |
2018年 | 291篇 |
2017年 | 190篇 |
2016年 | 275篇 |
2015年 | 414篇 |
2014年 | 401篇 |
2013年 | 515篇 |
2012年 | 504篇 |
2011年 | 478篇 |
2010年 | 295篇 |
2009年 | 242篇 |
2008年 | 282篇 |
2007年 | 294篇 |
2006年 | 236篇 |
2005年 | 190篇 |
2004年 | 181篇 |
2003年 | 139篇 |
2002年 | 141篇 |
2001年 | 98篇 |
2000年 | 76篇 |
1999年 | 60篇 |
1998年 | 39篇 |
1997年 | 34篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 25篇 |
1993年 | 25篇 |
1992年 | 54篇 |
1991年 | 42篇 |
1990年 | 53篇 |
1989年 | 47篇 |
1988年 | 39篇 |
1987年 | 32篇 |
1986年 | 38篇 |
1985年 | 30篇 |
1984年 | 38篇 |
1983年 | 34篇 |
1982年 | 32篇 |
1981年 | 34篇 |
1980年 | 40篇 |
1979年 | 21篇 |
1978年 | 27篇 |
1977年 | 19篇 |
1974年 | 22篇 |
1973年 | 20篇 |
排序方式: 共有7340条查询结果,搜索用时 15 毫秒
91.
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
92.
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
93.
Jiang Y. Tsui C. K. M. Ahmed S. A. Hagen F. Shang Z. Gerrits van den Ende A. H. G. Verweij P. E. Lu H. de Hoog G. S. 《Mycopathologia》2020,185(4):613-627
Mycopathologia - Emmonsia crescens is known as an environmental pathogen causing adiaspiromycosis in small rodents. As the generic name Emmonsia is no longer available for this species, its... 相似文献
94.
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
95.
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
96.
Jochen Baßler Yasar Luqman Ahmed Martina Kallas Markus Kornprobst Fabiola R. Calviño Marén Gnädig Matthias Thoms Gunter Stier Sherif Ismail Satyavati Kharde Nestor Castillo Sabine Griesel Sonja Bastuck Bettina Bradatsch Emma Thomson Dirk Flemming Irmgard Sinning Ed Hurt 《Protein science : a publication of the Protein Society》2017,26(2):327-342
Ribosome biogenesis in eukaryotic cells is a highly dynamic and complex process innately linked to cell proliferation. The assembly of ribosomes is driven by a myriad of biogenesis factors that shape pre‐ribosomal particles by processing and folding the ribosomal RNA and incorporating ribosomal proteins. Biochemical approaches allowed the isolation and characterization of pre‐ribosomal particles from Saccharomyces cerevisiae, which lead to a spatiotemporal map of biogenesis intermediates along the path from the nucleolus to the cytoplasm. Here, we cloned almost the entire set (~180) of ribosome biogenesis factors from the thermophilic fungus Chaetomium thermophilum in order to perform an in‐depth analysis of their protein–protein interaction network as well as exploring the suitability of these thermostable proteins for structural studies. First, we performed a systematic screen, testing about 80 factors for crystallization and structure determination. Next, we performed a yeast 2‐hybrid analysis and tested about 32,000 binary combinations, which identified more than 1000 protein–protein contacts between the thermophilic ribosome assembly factors. To exemplary verify several of these interactions, we performed biochemical reconstitution with the focus on the interaction network between 90S pre‐ribosome factors forming the ctUTP‐A and ctUTP‐B modules, and the Brix‐domain containing assembly factors of the pre‐60S subunit. Our work provides a rich resource for biochemical reconstitution and structural analyses of the conserved ribosome assembly machinery from a eukaryotic thermophile. 相似文献
97.
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
98.
Genomic analysis of the rhg1 locus: candidate genes that underlie soybean resistance to the cyst nematode 总被引:1,自引:0,他引:1
Ruben E Jamai A Afzal J Njiti VN Triwitayakorn K Iqbal MJ Yaegashi S Bashir R Kazi S Arelli P Town CD Ishihara H Meksem K Lightfoot DA 《Molecular genetics and genomics : MGG》2006,276(6):503-516
The rhg1 gene or genes lie at a recessive or co-dominant locus, necessary for resistance to all Hg types of the soybean (Glycine max (L.) Merr.) cyst nematode (Heterodera glycines I.). The aim here was to identify nucleotide changes within a candidate gene found at the rhg1 locus that were capable of altering resistance to Hg types 0 (race 3). A 1.5 ± 0.25 cM region of chromosome 18 (linkage group G) was shown to encompass rhg1 using recombination events from four near isogenic line populations and nine DNA markers. The DNA markers anchored two bacterial artificial chromosome (BAC) clones 21d9 and 73p6. A single receptor like kinase (RLK; leucine rich repeat-transmembrane-protein kinase) candidate resistance gene was amplified from both BACs using redundant primers. The DNA sequence showed nine alleles of the RLK at Rhg1 in the soybean germplasm. Markers designed to detect alleles showed perfect association between allele 1 and resistance to soybean cyst nematode Hg types 0 in three segregating populations, fifteen additional selected recombination events and twenty-two Plant Introductions. A quantitative trait nucleotide in the RLK at rhg1 was inferred that alters A47 to V47 in the context of H297 rather than N297. Contiguous DNA sequence of 315 kbp of chromosome 18 (about 2 cM) contained additional gene candidates that may modulate resistance to other Hg-types including a variant laccase, a hydrogen-sodium ion antiport and two proteins of unknown function. A molecular basis for recessive and co-dominant resistance that involves interactions among paralagous disease-resistance genes was inferred that would improve methods for developing new nematode-resistant soybean cultivars.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
99.
Jamil?Ahmed?SoomroEmail author Zeeshan?Noor?Shaikh Tennegedara?Buhary?Saheer Suhail?Ahmed?Bijarani 《International breastfeeding journal》2016,11(1):24
Background
Breastfeeding is considered to be an important measure to achieve optimum health outcomes for children, women’s return to work has frequently been found to be a main contributor to the early discontinuation of breastfeeding. The aim of the study is to assess workplace breastfeeding support provided to working mothers in Pakistan.Method
A workplace based cross-sectional survey was conducted from April through December 2014. Employers from a representative sample of 297 workplaces were interviewed on pre-tested and structured questionnaire. The response rate was 93.7 %. Prevalence of workplace breastfeeding facilities were assessed in the light of World Alliance for Breastfeeding Action (WABA) guidelines.Results
Among non-physical facilities, all workplaces offered 3 months paid maternity leave, 45 % of the sites were offering task adjustment to mothers during lactation period. Only 15 % of the sites were offering breastfeeding breaks to working mothers. Physical facilities that include a breastfeeding corner, refrigerator for storing breast milk, breast milk pump and nursery for childcare were provided in less than 7 % of the sites. Multinational organizations provided better support compared to national organizations.Conclusion
Support for continuation of breastfeeding by working women at workplaces is inadequate; hence, women discontinue breastfeeding earlier than planned. Policies need to be developed and enforced, employers and employees need to be educated and supportive environment needs to be created to encourage and facilitate breastfeeding friendly worksite environment.100.
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