全文获取类型
收费全文 | 34474篇 |
免费 | 2484篇 |
国内免费 | 1419篇 |
专业分类
耳鼻咽喉 | 255篇 |
儿科学 | 371篇 |
妇产科学 | 829篇 |
基础医学 | 7710篇 |
口腔科学 | 533篇 |
临床医学 | 2240篇 |
内科学 | 5289篇 |
皮肤病学 | 546篇 |
神经病学 | 1185篇 |
特种医学 | 1426篇 |
外国民族医学 | 4篇 |
外科学 | 1582篇 |
综合类 | 4297篇 |
现状与发展 | 5篇 |
预防医学 | 2596篇 |
眼科学 | 247篇 |
药学 | 3479篇 |
3篇 | |
中国医学 | 779篇 |
肿瘤学 | 5001篇 |
出版年
2024年 | 47篇 |
2023年 | 408篇 |
2022年 | 780篇 |
2021年 | 972篇 |
2020年 | 884篇 |
2019年 | 844篇 |
2018年 | 754篇 |
2017年 | 927篇 |
2016年 | 1066篇 |
2015年 | 1246篇 |
2014年 | 1740篇 |
2013年 | 2307篇 |
2012年 | 1601篇 |
2011年 | 1942篇 |
2010年 | 1581篇 |
2009年 | 1698篇 |
2008年 | 1672篇 |
2007年 | 1730篇 |
2006年 | 1685篇 |
2005年 | 1597篇 |
2004年 | 1455篇 |
2003年 | 1283篇 |
2002年 | 1150篇 |
2001年 | 1033篇 |
2000年 | 917篇 |
1999年 | 747篇 |
1998年 | 721篇 |
1997年 | 644篇 |
1996年 | 595篇 |
1995年 | 568篇 |
1994年 | 596篇 |
1993年 | 418篇 |
1992年 | 435篇 |
1991年 | 327篇 |
1990年 | 308篇 |
1989年 | 252篇 |
1988年 | 224篇 |
1987年 | 142篇 |
1986年 | 156篇 |
1985年 | 200篇 |
1984年 | 164篇 |
1983年 | 66篇 |
1982年 | 85篇 |
1981年 | 94篇 |
1980年 | 91篇 |
1979年 | 66篇 |
1978年 | 56篇 |
1977年 | 34篇 |
1976年 | 35篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
Chloroplast overexpression of rice caffeic acid O‐methyltransferase increases melatonin production in chloroplasts via the 5‐methoxytryptamine pathway in transgenic rice plants
下载免费PDF全文
![点击此处可从《Journal of pineal research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Recent analyses of the enzymatic features of various melatonin biosynthetic genes from bacteria, animals, and plants have led to the hypothesis that melatonin could be synthesized via the 5‐methoxytryptamine (5‐MT) pathway. 5‐MT is known to be synthesized in vitro from serotonin by the enzymatic action of O‐methyltransferases, including N‐acetylserotonin methyltransferase (ASMT) and caffeic acid O‐methyltransferase (COMT), leading to melatonin synthesis by the subsequent enzymatic reaction with serotonin N‐acetyltransferase (SNAT). Here, we show that 5‐MT was produced and served as a precursor for melatonin synthesis in plants. When rice seedlings were challenged with senescence treatment, 5‐MT levels and melatonin production were increased in transgenic rice seedlings overexpressing the rice COMT in chloroplasts, while no such increases were observed in wild‐type or transgenic seedlings overexpressing the rice COMT in the cytosol, suggesting a 5‐MT transport limitation from the cytosol to chloroplasts. In contrast, cadmium treatment led to results different from those in senescence. The enhanced melatonin production was not observed in the chloroplast COMT lines relative over the cytosol COMT lines although 5‐MT levels were equally induced in all genotypes upon cadmium treatment. The transgenic seedlings with enhanced melatonin in their chloroplasts exhibited improved seedling growth vs the wild type under continuous light conditions. This is the first report describing enhanced melatonin production in chloroplasts via the 5‐MT pathway with the ectopic overexpression of COMT in chloroplasts in plants. 相似文献
983.
984.
High pesticide exposure events and DNA methylation among pesticide applicators in the agricultural health study
下载免费PDF全文
![点击此处可从《Environmental and molecular mutagenesis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
985.
Effect of semen preparation technique and its incubation on sperm quality in the Moroccan population
下载免费PDF全文
![点击此处可从《Andrologia》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S. Aboulmaouahib A. Madkour I. Kaarouch B. Saadani O. Sefrioui N. Louanjli H. Copin R. Cadi M. Benkhalifa 《Andrologia》2017,49(6)
In in vitro fertilisation (IVF), sperm preparation as critical part and influencing the sperm quality is especially dependent on the chosen technique itself and incubation parameters including temperature and CO2. In this study, we compared firstly density‐gradient centrifugation technique (DGC) to the adapted DGC using the sperm pellet of 80% fraction (DGC/80P) in order to improve the sperm yield. Secondly, this study led to evaluate different sperm incubation conditions based on temperature effect (room temperature (RT = 23°C) versus 35°C) and in the other hand, with or without 5% CO2 during 24 hrs. Based on evaluating sperm conventional parameters and the DNA damage using TUNEL assay, our result showed that DGC/80P increased sperm quality compared to DGC with 25% of improvement. For temperature incubation effect after 24 hrs, 35°C increased the DNA damage and decreased the sperm quality while RT could improve sperm motility by 38%. Moreover, the sperm incubation with 5% CO2 after 24 hrs realised a negative impact on sperm parameters and its DNA damage. Indeed, for current IVF practice, a good sperm quality can be maintained for several hours at room temperature, while the sperm preparation is processed using the DGC/80P without CO2. 相似文献
986.
Graciela Uzcanga Eliana Lara Fernanda Gutiérrez Doyle Beaty Timo Beske Rommy Teran 《Critical reviews in microbiology》2017,43(2):156-177
Leishmaniasis is a common tropical disease that affects mainly poor people in underdeveloped and developing countries. This largely neglected infection is caused by Leishmania spp, a parasite from the Trypanosomatidae family. This parasitic disease has different clinical manifestations, ranging from localized cutaneous to more harmful visceral forms. The main limitations of the current treatments are their high cost, toxicity, lack of specificity, and long duration. Efforts to improve treatments are necessary to deal with this infectious disease. Many approved drugs to combat diseases as diverse as cancer, bacterial, or viral infections take advantage of specific features of the causing agent or of the disease. Recent evidence indicates that the specific characteristics of the Trypanosomatidae replication and repair machineries could be used as possible targets for the development of new treatments. Here, we review in detail the molecular mechanisms of DNA replication and repair regulation in trypanosomatids of the genus Leishmania and the drugs that could be useful against this disease. 相似文献
987.
Mahmud H. Abushhewa Mohamed H.S. Abushhiwa Matthew J. Nolan Aaron R. Jex Bronwyn E. Campbell Abdul Jabbar Robin B. Gasser 《Molecular and cellular probes》2010,24(6):346-351
We genetically classified Echinococcus granulosus from humans, cattle and camels in Libya utilizing DNA regions (designated pcox1 and pnad1) within the cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase 1 (nad1) mitochondrial genes, respectively. Polymerase chain reaction (PCR)-based single-strand conformation polymorphism (SSCP) analysis of pcox1 and pnad1 amplicons derived from genomic DNA samples from individual cysts (n = 176) revealed four distinct electrophoretic profiles for each locus. Direct sequencing of selected amplicons representing each of these profiles defined four different sequence types for each locus, which were present in five different combinations (designated haplotypes A–E) amongst all 176 isolates. Phylogenetic analysis of concatenated sequence data for these five haplotypes, together with a range of well-defined reference sequences, inferred that all cyst isolates from humans (n = 55) and a small number from cattle (13% of 38) belonged to the G1–G3 complex of E. granulosus (or E. granulosus sensu stricto), whereas most (87%) cysts from cattle and all 83 of them from camels were linked to the G6–G10 complex (or Echinococcus canadensis). The present study provides a foundation for future large-scale studies of the epidemiology and ecology of E. granulosus in Libya and other African countries. 相似文献
988.
989.
Eiji MUROI Fumihide OGAWA Toshifumi YAMAOKA Fumiko SUEYOSHI Shinichi SATO 《The Journal of dermatology》2010,37(1):81-84
We report a 4-year-old girl presenting with progressive linear scleroderma affecting the right leg. Biopsy specimen disclosed typical histopathological findings of localized scleroderma. Right leg magnetic resonance imaging (MRI) showed high signal areas on T2 -weighted images on the subcutaneous fatty tissue, muscles and bone marrow, suggesting that skin inflammation extended to the bone marrow. Oral corticosteroid therapy was instituted with improvement of both skin sclerosis and MRI findings. Our observations suggest that MRI examination should be considered in patients with localized scleroderma to evaluate the extension of the inflammation. 相似文献
990.
Romina F. Aromando Elisa M. Heber Verónica A. Trivillin David W. Nigg Amanda E. Schwint María E. Itoiz 《Journal of oral pathology & medicine》2009,38(5):448-454
Objective: The therapeutic success of different boron neutron capture therapy (BNCT) protocols employing the hamster cheek pouch oral cancer model has been previously reported by our laboratory. The aim of this study was to explore potential mechanisms of BNCT‐induced damage to tumor in terms of potential inhibition in DNA synthesis and induction of apoptosis in the tumors that underwent partial remission following application of the different BNCT protocols in this model. Materials and methods: We evaluated DNA synthesis employing incorporation of 5‐bromo‐2′‐deoxyuridine as an end‐point. Apoptosis was evaluated by immunohistochemistry employing the deoxynucleotidyl transferase‐mediated deoxyuridine triphosphate‐biotin nick end‐labeling technique and Bax and Bcl‐2 labeling. These studies were performed in tumors that underwent partial remission 1–30 days post‐BNCT mediated by boronophenylalanine (BPA), GB‐10 (Na210B10H10) or (BPA + GB‐10). Results: BNCT exerted a marked inhibitory effect on DNA synthesis in tumors for all the protocols under study. The inhibitory effect of BPA‐BNCT occurred as soon as 1 day post‐treatment (P < 0.001). Conversely, the effect of GB‐10‐BNCT became apparent 7–14 days after therapy (P < 0.001) and was sustained until killed at 30 days post‐treatment (P < 0.001). (GB‐10 + BPA)‐BNCT exerted a rapid and persistent effect, conceivably because of the combined effect of BNCT mediated by both boron compounds. The apoptosis studies did not show differences between the pre‐treatment group and any of the BNCT groups. Conclusions: One of the mechanisms involved in BNCT‐induced tumor control in our model would be an inhibitory effect on DNA synthesis. Apoptosis does not seem to have a significant role in BNCT‐induced tumor control in our model. 相似文献