全文获取类型
收费全文 | 23668篇 |
免费 | 1391篇 |
国内免费 | 31篇 |
出版年
2023年 | 205篇 |
2022年 | 417篇 |
2021年 | 882篇 |
2020年 | 531篇 |
2019年 | 565篇 |
2018年 | 791篇 |
2017年 | 737篇 |
2016年 | 977篇 |
2015年 | 1199篇 |
2014年 | 1466篇 |
2013年 | 1877篇 |
2012年 | 2117篇 |
2011年 | 1905篇 |
2010年 | 1083篇 |
2009年 | 974篇 |
2008年 | 1174篇 |
2007年 | 1110篇 |
2006年 | 941篇 |
2005年 | 847篇 |
2004年 | 709篇 |
2003年 | 592篇 |
2002年 | 522篇 |
2001年 | 342篇 |
2000年 | 297篇 |
1999年 | 279篇 |
1998年 | 129篇 |
1997年 | 95篇 |
1996年 | 104篇 |
1995年 | 94篇 |
1994年 | 74篇 |
1993年 | 72篇 |
1992年 | 174篇 |
1991年 | 163篇 |
1990年 | 130篇 |
1989年 | 107篇 |
1988年 | 143篇 |
1987年 | 110篇 |
1986年 | 93篇 |
1985年 | 98篇 |
1984年 | 94篇 |
1983年 | 58篇 |
1982年 | 54篇 |
1981年 | 68篇 |
1980年 | 56篇 |
1979年 | 76篇 |
1978年 | 45篇 |
1977年 | 58篇 |
1976年 | 43篇 |
1975年 | 41篇 |
1974年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Kyle M. Ewart Rebecca N. Johnson Rob Ogden Leo Joseph Greta J. Frankham Nathan Lo 《Molecular ecology resources》2019,19(6):1578-1592
Natural history museums harbour a plethora of biological specimens which are of potential use in population and conservation genetic studies. Although technical advancements in museum genomics have enabled genome‐wide markers to be generated from aged museum specimens, the suitability of these data for robust biological inference is not well characterized. The aim of this study was to test the utility of museum specimens in population and conservation genomics by assessing the biological and technical validity of single nucleotide polymorphism (SNP) data derived from such samples. To achieve this, we generated thousands of SNPs from 47 red‐tailed black cockatoo (Calyptorhychus banksii) traditional museum samples (i.e. samples that were not collected with the primary intent of DNA analysis) and 113 fresh tissue samples (cryopreserved liver/muscle) using a restriction site‐associated DNA marker approach (DArTseq?). Thousands of SNPs were successfully generated from most of the traditional museum samples (with a mean age of 44 years, ranging from 5 to 123 years), although 38% did not provide useful data. These SNPs exhibited higher error rates and contained significantly more missing data compared with SNPs from fresh tissue samples, likely due to considerable DNA fragmentation. However, based on simulation results, the level of genotyping error had a negligible effect on inference of population structure in this species. We did identify a bias towards low diversity SNPs in older samples that appears to compromise temporal inferences of genetic diversity. This study demonstrates the utility of a RADseq‐based method to produce reliable genome‐wide SNP data from traditional museum specimens. 相似文献
992.
Germline variants in oculocutaneous albinism genes and predisposition to familial cutaneous melanoma
Vaishnavi Nathan Peter A. Johansson Jane M. Palmer Madeleine Howlie Hayley R. Hamilton Karin Wadt Gran Jnsson Kelly M. Brooks Antonia L. Pritchard Nicholas K. Hayward 《Pigment cell & melanoma research》2019,32(6):854-863
Approximately 1%–2% of cutaneous melanoma (CM) is classified as strongly familial. We sought to investigate unexplained CM predisposition in families negative for the known susceptibility genes using next‐generation sequencing of affected individuals. Segregation of germline variants of interest within families was assessed by Sanger sequencing. Several heterozygous variants in oculocutaneous albinism (OCA) genes: TYR, OCA2, TYRP1 and SLC45A2, were present in our CM cohort. OCA is a group of autosomal recessive genetic disorders, resulting in pigmentation defects of the eyes, hair and skin. Missense variants classified as pathogenic for OCA were present in multiple families and some fully segregated with CM. The functionally compromised TYR p.T373K variant was present in three unrelated families. In OCA2, known pathogenic variants: p.V443I and p.N489D, were present in three families and one family, respectively. We identified a likely pathogenic SLC45A2 frameshift variant that fully segregated with CM in a family of four cases. Another four‐case family harboured cosegregating variants (p.A24T and p.R153C) of uncertain functional significance in TYRP1. We conclude that rare, heterozygous variants in OCA genes confer moderate risk for CM. 相似文献
993.
Abeer Hashem Ashwani Kumar Abeer M. Al-Dbass Abdulaziz A. Alqarawi Al-Bandari Fahad Al-Arjani Garima Singh Muhammad Farooq Elsayed Fathi Abd_Allah 《Saudi Journal of Biological Sciences》2019,26(3):614-624
Arbuscular mycorrhizal fungi (AMF) inoculation and biochar amendment has been reported to improve growth of several crop plants however their role in stress amelioration individually as well as in combination has not been worked out. This experiment was conducted to evaluate the application of AMF and biochar on the performance of chickpea under drought stress. The treatments included the individual as well as combined treatment of AMF and biochar to drought stressed and normal chickpea plants. Plants inoculation improved growth in terms of shoot and root length, leaf area and number of branches which was observed to show a steep decline due to drought stress. Drought declined the AMF colonization potential though biochar amendment ameliorated the negative effects of drought significantly by improving the spore population, number of mycelium, vesicle and arbuscules and the percentage of colonization as well. Increased chlorophyll synthesis in biochar and AMF treated plants was obvious, which lead to significant enhancement in the net photosynthetic efficiency. Drought stress also declined the relative water content (RWC) and membrane stability index (MSI), while treatment of biochar and AMF either individually or in combination mitigated the deleterious effects to considerable extent and caused a significant enhancement in RWC and MSI under normal conditions. Amendments with biochar and AMF inoculation increased the nitrogen fixation attributes including the number and weight of nodules, leghemoglobin content and activity of nitrate reductase enzyme leading to greater uptake and assimilation of nitrogen in them when compared to drought stressed plants. Drought stressed chickpea plants exhibited considerable reduction in uptake of nitrogen and phosphorous which was ameliorated by biochar and AMF treatments. It could be suggested that increase in growth and physiological attributes in chickpea due to biochar amendments and AMF inoculation under drought stress were plausibly due to their involvement in nitrogen and phosphorous uptake, chlorophyll synthesis and photosynthesis. 相似文献
994.
Noor Ahmad Shaik Huda M. Al-Kreathy Ghada M. Ajabnoor Prashant Kumar Verma Babajan Banaganapalli 《Saudi Journal of Biological Sciences》2019,26(3):439-448
The somatic mutations in ATP binding cleft of the tyrosine kinase binding domain of EGFR are known to occur in 15–40% of non-small cell lung cancer (NSCLC) patients. Although first and second generation anti-EGFR inhibitors are widely used to treat these patients, their therapeutic efficacy is modest and often results in adverse effects or drug resistance. Therefore, there is a need to develop novel as well as safe anti-EGFR drugs. The rapid emergence of computational drug designing provided a great opportunity to both discover and predict the efficacy of novel EGFR inhibitors from plant sources. In the present study, we designed several chemical analogues of edible curcumin (CUCM) compound and assessed their drug likeliness, ADME and toxicity properties using a diverse range of advanced computational methods. We also have examined the structural plasticity and binding characteristics of EGFR wild-type and mutant forms (S769L and K846R) against ligand molecules like Gefitinib, native CUCM, and different CUCM analogues. Through multidimensional experimental approaches, we conclude that CUCM-36 ((1E,4Z,6E)-1-(3,4-Diphenoxyphenyl)-5-hydroxy-7-(4-hydroxy-3-phenoxyphenyl)-1,4,6-heptatrien-3-one) is the best anti-EGFR compound with high drug-likeness, ADME properties, and low toxicity properties. CUCM-36 compound has demonstrated better affinity towards both wild-type (ΔG is ?8.5?kcal/Mol) and mutant forms (V769L & K846R; ΔG for both is >?9.20?kcal/Mol) compared to natural CUCM and Gefitinib inhibitor. This study advises the future laboratory assays to develop CUCM-36 as a novel drug compound for treating EGFR positive non-small cell lung cancer patients. 相似文献
995.
996.
997.
998.
Vicuna Requesens Deborah Gonzalez Romero Maria Elena Devaiah Shivakumar P. Chang Yeun-Kyung Flory Ashley Streatfield Stephen Ring Rebecca Phillips Cassie Hood Nathan C. Marbaniang Cyrus Dean Howard John A. Hood Elizabeth E. 《Transgenic research》2019,28(5-6):537-547
Transgenic Research - Expression of recombinant proteins in plants is a technology for producing vaccines, pharmaceuticals and industrial enzymes. For the past several years, we have produced... 相似文献
999.
1000.
Reddymasu Sreenivasulu Kotthireddy Thirumal Reddy Pombala Sujitha C. Ganesh Kumar Rudraraju Ramesh Raju 《Bioorganic & medicinal chemistry》2019,27(6):1043-1055
In recent years, indole-indazolyl hydrazide-hydrazone derivatives with strong cell growth inhibition and apoptosis induction characteristics are being strongly screened for their cancer chemo-preventive potential. In the present study, N-methyl and N,N-dimethyl bis(indolyl)hydrazide-hydrazone analog derivatives were designed, synthesized and allowed to evaluate for their anti-proliferative and apoptosis induction potential against cervical (HeLa), breast (MCF-7 and MDA-MB-231) and lung (A549) cancer cell lines relative to normal HEK293 cells. The MTT assay in conjunction with mitochondrial potential assays and the trypan blue dye exclusion were employed to ascertain the effects of the derivatives on the cancer cells. Further, mechanistic studies were conducted on compound 14a to understand the biochemical mechanisms and functional interactions with various signaling pathways triggered in HeLa and MCF-7 cells. Compound 14a induced apoptosis via caspase independent pathway through the participation of mitogen-activated protein kinases (MAPK) such as extracellular signal related kinase (ERK) and p38 as well as p53 pathways. It originates the activation of pro-apoptotic proteins such as Bak and Mcl-1s and also strongly induced the generation of reactive oxygen species. In downstream signaling pathway, activated p53 protein interacted with MAPK pathways, including SAPK/c-Jun N-terminal protein kinase (JNK), p38 and ERK kinases resulting in apoptotic cell death. The involvement of MAPK cascades such as p38, ERK and p38 on compound 14a induced apoptotic cell death was evidenced by the fact that the inclusion of specific inhibitors of p38, ERK1/2 and JNK MAPK (SB2035809, PD98059 and SP600125) prevented the compound 14a towards induced apoptosis. The results clearly showed that MAP kinase cascades were crucial for apoptotic response in compound 14a induced cellular killing and were dependent on p53 activity. Based on the results, compound 14a was identified as a promising candidate for cancer therapeutics and these findings furnish a basis for further in vivo experiments on anti-proliferative activity. 相似文献