全文获取类型
收费全文 | 3807篇 |
免费 | 189篇 |
国内免费 | 27篇 |
专业分类
4023篇 |
出版年
2024年 | 13篇 |
2023年 | 82篇 |
2022年 | 183篇 |
2021年 | 315篇 |
2020年 | 157篇 |
2019年 | 186篇 |
2018年 | 252篇 |
2017年 | 154篇 |
2016年 | 228篇 |
2015年 | 275篇 |
2014年 | 291篇 |
2013年 | 294篇 |
2012年 | 311篇 |
2011年 | 251篇 |
2010年 | 164篇 |
2009年 | 143篇 |
2008年 | 142篇 |
2007年 | 129篇 |
2006年 | 91篇 |
2005年 | 79篇 |
2004年 | 57篇 |
2003年 | 46篇 |
2002年 | 35篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有4023条查询结果,搜索用时 15 毫秒
21.
Asma Haque Tayyaba Shaheen Tahsin Gulzar Mahmood ur Rahman Fatima Jalal Summera Sattar Beenish Ehsan Zafar Iqbal Muhammad Younas 《Bioinformation》2014,10(6):371-377
Wheat is a vital dietary component for human health and widely consumed in the world. Wheat rusts are dangerous pathogens
and contribute serious threat to its production. In present study, PCR-Based DNA Markers were employed to check the rust
resistance genes among 20 wheat genotypes and 22 markers were amplified. NTSYS-pc 2.2 was used to calculate genetic diversity
and Nei and Li''s coefficients ranged from 0.55 to 0.95. Cluster analysis was obtained using UPGMA (Unweighted Pair Group
Method of Arithmetic Average) algorithm. Maximum no. of genes (23) was amplified from TW-760010 genotype whereas
minimum no of genes (14) were amplified from TW-76005 genotype. The data gained from present study open up new ways to
produce new varieties by breeding rust resistant germplasm to avoid the economic and food loss and varieties with improved
characteristics. 相似文献
22.
Novel cyclization of 4-(substituted-phenylsulfonamido)butanoic acids to their corresponding 1-[(substituted-phenyl)sulfonyl]pyrrolidin-2-ones was successfully achieved by using polyphosphate ester (PPE). The reaction time was considerably reduced with corresponding increase in the yields, when polyphosphate ester (PPE) was used in combination with 4-(N,N-dimethylamino)pyridine (DMAP). All the synthesized compounds were screened for their antimicrobial activity. Minimum Inhibitory Concentration (MIC) values of synthesized compounds were also determined, and were found to be in the range of 0.09-1.0 mg. 相似文献
23.
24.
25.
Wasim Ahmed Xiaojing Yan Dekun Hu Muhammad Adnan Ri-Yuan Tang Zi-Ning Cui 《Bioorganic & medicinal chemistry》2019,27(19):115048
Pyrazole constitutes an important heterocyclic family covering a broad range of synthetic as well as natural products that exhibit numerous chemical, biological, agrochemical and pharmacological properties. In order to explore compounds with good fungicidal activity, a series of new pyrazole derivatives containing 5-phenyl-2-furan were designed and synthesized. In vitro and in vivo fungicidal activities were evaluated and the compound ethyl-1-(5-phenylfuran-2-carbonyl)-5-propyl-1H-pyrazole-3-carboxylate (I8) displayed significant fungicidal activity against various fungi, especially against P. infestans. The structures of the novel pyrazole derivatives were confirmed by 1H NMR, 13C NMR, MS, elemental analysis and X-ray single crystal diffraction. Further study showed that compound I8 might act on the synthesis of cell walls from morphological and ultrastructural studies by SEM and TEM. The results also revealed that compound I8 could block the nutritional transportation leading to cells senescence and death. These results suggested that the novel pyrazole derivatives proved to be promising lead compounds. 相似文献
26.
Muhammad Shahid Minhyung Kim Min Young Lee Austin Yeon Sungyong You Hyung L. Kim Jayoung Kim 《Proteomics》2019,19(11)
Metabolic alterations in prostate cancer (PC) are associated with progression and aggressiveness. However, the underlying mechanisms behind PC metabolic functions are unknown. The authors’ group recently reported on the important role of centromere protein F (CENPF), a protein associated with the centromere–kinetochore complex and chromosomal segregation during mitosis, in PC MRI visibility. This study focuses on discerning the role of CENPF in metabolic perturbation in human PC3 cells. A series of bioinformatics analyses shows that CENPF is one gene that is strongly associated with aggressive PC and that its expression is positively correlated with metastasis. By identifying and reconstructing the CENPF network, additional associations with lipid regulation are found. Further untargeted metabolomics analysis using gas chromatography‐time‐of‐flight‐mass spectrometry reveals that silencing of CENPF alters the global metabolic profiles of PC cells and inhibits cell proliferation, which suggests that CENPF may be a critical regulator of PC metabolism. These findings provide useful scientific insights that can be applied in future studies investigating potential targets for PC treatment. 相似文献
27.
Orla A. Houlihan Richard Moore Muhammad F. Jamaluddin Adrinda Sharifah Henry Paul Redmond Seamus OReilly Linda Feeley Patrick Sheahan Kathy Rock 《Reports of Practical Oncology and Radiotherapy》2021,26(3):416
BackroundThe purpose of this study is to assess the impact of trimodal therapy [surgery, chemotherapy and external beam radiotherapy (EBRT)] in patients with anaplastic thyroid cancer (ATC) treated with curative intent.Materials and methodsRetrospective review of patients with ATC treated at a tertiary referral centre between January 2009 and June 2020. Data were collected regarding demographics, histology, staging, treatment and outcomes.ResultsSeven patients (4 female) were identified. Median age was 58 years (range 52–83 years). All patients received EBRT with concurrent doxorubicin. Six patients received surgery followed by chemoradiotherapy (CRT), and one underwent neoadjuvant CRT followed by surgery. Median radiological tumour size was 50mm (range 40–90 mm). Six patients had gross extrathyroidal extension and three had N1b disease. Prescribed radiotherapy schedules were 46.4 Gy in 29 bidaily fractions (n = 2, treated 2010), 60 Gy in 30 daily fractions (n = 2), 66 Gy in 30 fractions (n = 2) and 70 Gy in 35 fractions (n = 1; patient received neoadjuvant CRT). CRT was discontinued early for two patients due to toxicities. At median follow up of 5.8 months, 42.9% (3/7) patients were alive and disease-free. Only one patient developed a local failure. Three patients died from distant metastases without locoregional recurrence.ConclusionsDespite poor prognosis of ATC, selected patients with operable tumours may achieve high locoregional control rates with trimodal therapy, with possibility of long-term survival in select cases. 相似文献
28.
29.
In the present study, the relationship between the nutritional status of leaves and the development of symptoms of cotton leaf curl virus (CLCuV) in two cotton (Gossypium hirsutum L.) cultivars (i.e. CIM-240 and S-12) was investigated. The incidence of disease attack was found to be 100% in the S-12 cultivar and 16% in the CIM-240 cultivar. Geminivirus particles in infected leaves were confirmed by transmission electron microscope examination of highly specific geminivirus coat protein antisera-treated cell sap. The CLCuV impaired the accumulation of different nutrients in both cultivars. A marked decrease in the accumulation of Ca2+ and K+ was observed in infected leaves. However, the disease had no effect on leaf concentrations of Na+, N, and P. It was observed that the curling of leaf margins in CLCuV-infected plants was associated with the leaf Ca2+ content; leaf curling was severe in plants with a significant reduction in Ca2+ content.Moreover, leaf K+ content was found to be associated with resistance/susceptibility to CLCuV infection. 相似文献
30.
Structure and oligomerization of the PilC type IV pilus biogenesis protein from Thermus thermophilus
Type IV pili are expressed from a wide variety of Gram‐negative bacteria and play a major role in host cell adhesion and bacterial motility. PilC is one of at least a dozen different proteins that are implicated in Type IV pilus assembly in Thermus thermophilus and a member of a conserved family of integral inner membrane proteins which are components of the Type II secretion system (GspF) and the archeal flagellum. PilC/GspF family members contain repeats of a conserved helix‐rich domain of around 100 residues in length. Here, we describe the crystal structure of one of these domains, derived from the N‐terminal domain of Thermus thermophilus PilC. The N‐domain forms a dimer, adopting a six helix bundle structure with an up‐down‐up‐down‐up‐down topology. The monomers are related by a rotation of 170°, followed by a translation along the axis of the final α‐helix of approximately one helical turn. This means that the regions of contact on helices 5 and 6 in each monomer are overlapping, but different. Contact between the two monomers is mediated by a network of hydrophobic residues which are highly conserved in PilC homologs from other Gram‐negative bacteria. Site‐directed mutagenesis of residues at the dimer interface resulted in a change in oligomeric state of PilC from tetramers to dimers, providing evidence that this interface is also found in the intact membrane protein and suggesting that it is important to its function. Proteins 2010. © 2010 Wiley‐Liss, Inc. 相似文献