全文获取类型
收费全文 | 43658篇 |
免费 | 3741篇 |
国内免费 | 3476篇 |
专业分类
50875篇 |
出版年
2024年 | 107篇 |
2023年 | 622篇 |
2022年 | 1462篇 |
2021年 | 2410篇 |
2020年 | 1559篇 |
2019年 | 2016篇 |
2018年 | 1950篇 |
2017年 | 1411篇 |
2016年 | 1924篇 |
2015年 | 2683篇 |
2014年 | 3206篇 |
2013年 | 3480篇 |
2012年 | 3936篇 |
2011年 | 3549篇 |
2010年 | 2139篇 |
2009年 | 1916篇 |
2008年 | 2205篇 |
2007年 | 1896篇 |
2006年 | 1629篇 |
2005年 | 1373篇 |
2004年 | 1245篇 |
2003年 | 1131篇 |
2002年 | 1014篇 |
2001年 | 903篇 |
2000年 | 750篇 |
1999年 | 714篇 |
1998年 | 416篇 |
1997年 | 399篇 |
1996年 | 409篇 |
1995年 | 353篇 |
1994年 | 326篇 |
1993年 | 238篇 |
1992年 | 335篇 |
1991年 | 248篇 |
1990年 | 200篇 |
1989年 | 184篇 |
1988年 | 118篇 |
1987年 | 112篇 |
1986年 | 77篇 |
1985年 | 92篇 |
1984年 | 34篇 |
1983年 | 38篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1950年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Smith GD Zhou L Rowe LR Jarboe EA Collins BT Bentz JS Wittwer CT Chadwick BE 《Acta cytologica》2011,55(6):576-583
Objective: To detect BRAF V600E mutation in thyroid fine-needle aspiration (FNA) slides and needle rinses (NR). Study Design: Tumor-enriched DNA was extracted from FNA smears, formalin-fixed paraffin-embedded (FFPE) sections, or NR specimens from 37 patients with confirmed papillary thyroid carcinoma or benign findings. An allele-specific primer selectively amplified the 1799 T>A BRAF mutation while simultaneously blocking amplification of wild-type (WT) BRAF with an unlabeled probe during PCR. Mutation detection was accomplished by melting analysis of the probe. Results: Allele-specific/blocking probe PCR confirmed the BRAF mutation status for 20 of 24 paired FNA/FFPE samples previously tested by fluorescent probe real-time PCR. For the other 4 cases, the sensitive PCR method detected the BRAF mutation in all paired FNA/FFPE samples. Previously, the mutation had been detected in only the FFPE samples. The BRAF mutation was also detected in some NR specimens. Conclusion: Treatment of patients with thyroid nodules is guided by FNA biopsy, which can be scantly cellular, necessitating a sensitive test that can detect low levels of BRAF V600E mutation in a WT background. We report increased detection of BRAF V600E in FNA specimens using allele-specific/blocking probe PCR, which has an analytical sensitivity of 0.01%. 相似文献
72.
73.
小麦秆锈抗性遗传及抗性基因研究进展 总被引:1,自引:0,他引:1
目前国际上已发现近80个小麦抗秆锈基因,其中45个抗秆锈基因已被正式定名,58个抗秆锈基因已定位在小麦特定染色体上,其中12个基因被标记。本文对小麦抗秆锈病基因抗源、抗秆锈性遗传、分子标记研究现状及存在问题加以综述,并对抗秆锈分子遗传前景进行展望。 相似文献
74.
75.
The effect of established infection on microvascular surgery 总被引:6,自引:0,他引:6
The success of microvascular anastomoses in the presence of staphylococcal infection was studied using rat femoral arteries. There was a spontaneous thrombosis rate of 19 percent in normal vessels that traversed the area of infection. Vessels with an anastomosis outside the area of infection had a similar thrombosis rate, but if the anastomotic site was within the infected area itself, the thrombosis rate increased to 75 percent. Inflammatory changes with subsequent fibrosis in the media and adventitia appeared responsible for the thrombosis. The intima was unaffected by the presence of infection. This study suggests that when a microvascular anastomosis is necessary in the presence of infection, the anastomosis should be placed outside the area of infection with a pedicle to traverse the infected area. 相似文献
76.
Jie Dai Jun Zhou Hongmei Liu Kaixun Huang 《Journal of biological inorganic chemistry》2016,21(8):1037-1046
Selenite and ebselen supplementation has been shown to possess anti-cataract potential in some experimental animal models of cataract, however, the underlying mechanisms remain unclear. The present study was designed to evaluate the anti-cataract effects and the underlying mechanisms of selenite and ebselen supplementation on galactose induced cataract in rats, a common animal model of sugar cataract. Transmission electron microscopy images of lens fiber cells (LFC) and lens epithelial cells (LEC) were observed in d-galactose-induced experimental cataractous rats treated with or without selenite and ebselen, also redox homeostasis and expression of proteins such as selenoprotein R (SELR), 15kD selenoprotein (SEP15), superoxide dismutase 1 (SOD1), catalase (CAT), β-crystallin protein, aldose reductase (AR) and glucose-regulated protein 78 (GRP78) were estimated in the lenses. The results showed that d-galactose injection injured rat lens and resulted in cataract formation; however, selenite and ebselen supplementation markedly alleviated ultrastructural injury of LFC and LEC. Moreover, selenite and ebselen supplementation could mitigate the oxidative damage in rat lens and increase the protein expressions of SELR, SEP15, SOD1, CAT and β-crystallin, as well as decrease the protein expressions of AR and GRP78. Taken together, these findings for the first time reveal the anti-cataract potential of selenite and ebselen in galactosemic cataract, and provide important new insights into the anti-cataract mechanisms of selenite and ebselen in sugar cataract. 相似文献
77.
Salvador promotes both cell cycle exit and apoptosis through the modulation of both cyclin E and Drosophila inhibitor of apoptosis protein in Drosophila. However, the cellular function of human Salvador (hSav1) is rarely reported. To screen for novel binding proteins that interact with hSav1, the cDNA of hSav1 was cloned into a bait protein plasmid, and positive clones were screened from a human fetal liver cDNA library by the yeast two-hybrid system. hSav1 mRNA was expressed in yeast and there was no self-activation and toxicity in the yeast strain AH109. Twenty proteins were found to interact with hSav1, including HS1 (haematopoietic cell specific protein1)-associated protein X-1 (HAX-1); neural precursor cell expressed, developmentally down-regulated 9, pyruvate kinase, liver and RBC, cytochrome c oxidase subunit Vb, enoyl coenzyme A hydratase short chain 1, and NADH dehydrogenase (ubiquinone) 1 beta subcomplex, demonstrating that the yeast two-hybrid system is an efficient method for investigating protein interactions. Among the identified proteins, there were many mitochondrial proteins, indicating that hSav1 may play a role in mitochondrial function. We also confirmed the interaction of HAX-1 and hSav1 in mammalian cells. This investigation provides functional clues for further exploration of potential apoptosis-related proteins in disease biotherapy. 相似文献
78.
Five new guaiane sesquiterpenes, 1 – 5 , were isolated from the culture broth of the endophytic fungus Xylaria sp. YM 311647, isolated from Azadirachta indica A. Juss . The structures of these compounds were elucidated on the basis of spectroscopic analyses, and their inhibitory activities against five pathogenic fungi were evaluated. All guaiane sesquiterpenes showed moderate or weak antifungal activities in a broth microdilution assay. 相似文献
79.
80.