全文获取类型
收费全文 | 1369篇 |
免费 | 124篇 |
国内免费 | 21篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 41篇 |
妇产科学 | 32篇 |
基础医学 | 206篇 |
口腔科学 | 11篇 |
临床医学 | 113篇 |
内科学 | 289篇 |
皮肤病学 | 24篇 |
神经病学 | 56篇 |
特种医学 | 96篇 |
外科学 | 154篇 |
综合类 | 38篇 |
一般理论 | 1篇 |
预防医学 | 144篇 |
眼科学 | 69篇 |
药学 | 115篇 |
中国医学 | 7篇 |
肿瘤学 | 112篇 |
出版年
2023年 | 13篇 |
2022年 | 32篇 |
2021年 | 46篇 |
2020年 | 21篇 |
2019年 | 32篇 |
2018年 | 48篇 |
2017年 | 21篇 |
2016年 | 28篇 |
2015年 | 30篇 |
2014年 | 60篇 |
2013年 | 58篇 |
2012年 | 71篇 |
2011年 | 74篇 |
2010年 | 70篇 |
2009年 | 52篇 |
2008年 | 65篇 |
2007年 | 60篇 |
2006年 | 63篇 |
2005年 | 61篇 |
2004年 | 49篇 |
2003年 | 49篇 |
2002年 | 43篇 |
2001年 | 35篇 |
2000年 | 25篇 |
1999年 | 28篇 |
1998年 | 25篇 |
1997年 | 27篇 |
1996年 | 20篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 20篇 |
1991年 | 13篇 |
1990年 | 18篇 |
1989年 | 20篇 |
1988年 | 12篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1977年 | 16篇 |
1975年 | 7篇 |
1973年 | 8篇 |
1971年 | 6篇 |
1970年 | 7篇 |
排序方式: 共有1514条查询结果,搜索用时 15 毫秒
41.
Considering the fungicidal threat to the sustainable agro-environment, the toxicological impacts of three fungicides, namely kitazin, hexaconazole and carbendazim, on the biological, chemical and morpho-anatomical changes of peas were assessed. Fungicide applications in general caused a slow but gradual reduction in growth, symbiosis and yields of peas, which, however, varied appreciably among species and concentrations of the three fungicides. Of the three fungicides, carbendazim had the most lethal effect, in which it delayed seed germination and also diminished the overall pea growth. Carbendazim at 3000 μg kg−1 maximally reduced the germination, SVI, size of roots and shoots and total dry matter accumulation in roots, shoots and whole plants distinctly by 40%, 84%, 72%, 73%, 68%, 75% and 73% (p ≤ 0.05), respectively. Hexaconazole at 120 μg kg−1 significantly (p ≤ 0.05) declined total chlorophyll, carotenoids, grain yields, grain protein, root P and shoot N by 19%, 28%, 46%, 69%, 48% and 51%, respectively, over the control. The synthesis of stress biomarkers and oxidative stress were increased with increasing dosage rates of fungicides. Proline content in roots, shoots, leaves and grains, MDA, electrolyte leakage and H2O2 of plants grown in soil treated with 288 μg kg−1 kitazin were increased significantly (p ≤ 0.05) by 73%, 52%, 41%, 24%, 59%, 40% and 27%, respectively, relative to the control. Antioxidant defence enzymes were greater in pea foliage. The SEM and CLSM images revealed an obvious alteration in root tips, enhanced cellular damage and cell death when plants were raised under fungicide stress. Also, morpho-anatomical variations in fungicide-treated foliage were visible in the SEM images. Overall, the present study suggests that a careful and secure strategy should be adopted before fungicides are chosen for enhancing pulse production in different agro-climatic regions.Considering the fungicidal threat to the sustainable agro-environment, the toxicological impacts of three fungicides, namely kitazin, hexaconazole and carbendazim, on the biological, chemical and morpho-anatomical changes of peas were assessed. 相似文献
42.
Romisuhani Ahmad Mohd Mustafa Al Bakri Abdullah Wan Mastura Wan Ibrahim Kamarudin Hussin Fakhryna Hannanee Ahmad Zaidi Jitrin Chaiprapa Jerzy J. Wysocki Katarzyna Boch Marcin Nabiaek 《Materials》2021,14(5)
The primary motivation of developing ceramic materials using geopolymer method is to minimize the reliance on high sintering temperatures. The ultra-high molecular weight polyethylene (UHMWPE) was added as binder and reinforces the nepheline ceramics based geopolymer. The samples were sintered at 900 °C, 1000 °C, 1100 °C, and 1200 °C to elucidate the influence of sintering on the physical and microstructural properties. The results indicated that a maximum flexural strength of 92 MPa is attainable once the samples are used to be sintered at 1200 °C. It was also determined that the density, porosity, volumetric shrinkage, and water absorption of the samples also affected by the sintering due to the change of microstructure and crystallinity. The IR spectra reveal that the band at around 1400 cm−1 becomes weak, indicating that sodium carbonate decomposed and began to react with the silica and alumina released from gels to form nepheline phases. The sintering process influence in the development of the final microstructure thus improving the properties of the ceramic materials. 相似文献
43.
The amino acid intermediate homocysteine (Hcy) is formed during the metabolism of methionine to cysteine. Hyperhomocysteinemia (HHcy) is recognized as an independent risk factor for coronary atherosclerosis. The circulating levels of total Hcy (tHcy) can increase due to intake of foods rich in methionine or deficiencies of vitamins such as folate, pyridoxine and cyanocobalamin, which are required for the metabolism of Hcy. In addition, mutations in the genes coding for Hcy metabolizing enzymes can contribute to an increase in tHcy levels. Clinical and epidemiological studies have shown that an elevated level of tHcy measured in serum or plasma is a strong predictor of cardiovascular disease risk, which appears to be greatest in patients who have HHcy following a methionine load. Intimal hyperplasia (IH) (intima/media [I/M] ratio) is the universal response of a vessel to injury and may result in vasoconstriction when left unattended. The effect of dietary HHcy on balloon catheter-injured carotid artery and its modulation (if any) by the peroxisome proliferator-activated receptor agonist gamma rosiglitazone was evaluated in 12-week-old female Sprague-Dawley rats fed either a control diet or a diet containing 1% L-methionine. Once the rats were established on the diet, the group that was fed 1% L-methionine was further subdivided and either given an aqueous preparation of 3 mg/kg/day rosiglitazone or the vehicle via oral gavage for one week. This was followed by surgically injuring the left carotid artery using a Maverick Over-The-Wire catheter (2.0 mm × 20 mm, 3.2F; Boston Scientific, USA). The rats were continued on their respective diets and drug regimen for 21 days postsurgery. On day 22 of the procedure, the rats were sacrificed for collection of blood, the carotid arteries and liver for biochemical and histological evaluation. Compared with controls there was a significant increase in both tHcy levels and I/M ratio in the rats fed 1% L-methionine (5.4±0.28 μM versus 32.8±3.01 μM, P<0.002; and 0.175±0.05 versus 1.05±0.23, P<0.005, respectively). The effect of rosiglitazone in rats fed the control diet was not prominent. On the other hand, administration of rosiglitazone to the rats on the 1% L-methionine diet significantly reduced the levels of serum tHcy (16.6±2.1 μM versus 32.8±3.01 μM, P<0.001); however, the tHcy levels remained significantly elevated compared with animals on the control diet (P<0.002). The group receiving the L-methionine diet plus rosiglitazone had an inhibition in the development of IH compared with those receiving the L-methionine diet alone (I/M of 0.278±0.041 versus 1.05±0.23, P<0.01). Moreover, the development of IH in the group receiving the L-methionine diet plus rosiglitazone treatment was not significantly different from that observed in the group on the control diet without rosiglitazone (0.278±0.041 versus 0.175±0.05, respectively). These findings may have important implications in deciphering the molecular mechanisms involved in the augmentation of IH in HHcy and modulation of this process by rosiglitazone. 相似文献
44.
Adhesion of platelets to surface-bound fibrinogen under flow 总被引:2,自引:2,他引:2
After platelet activation, fibrinogen mediates platelet-platelet interactions leading to platelet aggregation. In addition, fibrinogen can also function as a cell adhesion molecule, providing a substratum for adhesion of platelets and endothelial cells. In this report, we studied the adhesion of platelets to surface-immobilized fibrinogen under flow in different shear rates. Heparinized whole blood containing mepacrine-labeled platelets was perfused for two minutes at various wall shear rates from 250 to 2,000 s-1 in a parallel plate flow chamber. The number of adherent fluorescent platelets was quantitated every 15 seconds with an epifluorescent videomicroscope and digital image processing system. When compared with platelet adhesion and aggregation seen on glass surfaces coated with type I bovine collagen, a significant increase in platelet adhesion was observed on immobilized fibrinogen up to wall shear rates of 800 s-1. The adherent platelets formed a single layer on fibrinogen-coated surfaces. Under identical conditions, no significant adhesion was observed on fibronectin- or vitronectin-coated surfaces. Although platelet adhesion to collagen was substantially inhibited by the platelet inhibitors prostaglandin E1 and theophylline, these inhibitors had no effect on platelet adhesion to fibrinogen. Platelets adhered to recombinant homodimeric wild-type (gamma 400-411) fibrinogen, but not to the recombinant homodimeric gamma' variant of fibrinogen. Platelet adhesion to recombinant fibrinogen with RGD to RGE mutations at positions alpha 95-97 and alpha 572-574 was similar to that with plasma-derived fibrinogen. These results show that platelets adhere to fibrinogen-coated surfaces under moderate wall shear rates, that the interaction is mediated by the fibrinogen 400-411 sequence at the carboxy-terminus of the gamma chain, and that the interaction is independent of platelet activation and the RGD sequences in the alpha chain. 相似文献
45.
Li Sun Roberto Tamma Tony Yuen Graziana Colaianni Yaoting Ji Concetta Cuscito Jack Bailey Samarth Dhawan Ping Lu Cosima D. Calvano Ling-Ling Zhu Carlo G. Zambonin Adriana Di Benedetto Agnes Stachnik Peng Liu Maria Grano Silvia Colucci Terry F. Davies Maria I. New Alberta Zallone Mone Zaidi 《Proceedings of the National Academy of Sciences of the United States of America》2016,113(1):164-169
Prior studies show that oxytocin (Oxt) and vasopressin (Avp) have opposing actions on the skeleton exerted through high-affinity G protein-coupled receptors. We explored whether Avp and Oxtr can share their receptors in the regulation of bone formation by osteoblasts. We show that the Avp receptor 1α (Avpr1α) and the Oxt receptor (Oxtr) have opposing effects on bone mass: Oxtr−/− mice have osteopenia, and Avpr1α−/− mice display a high bone mass phenotype. More notably, this high bone mass phenotype is reversed by the deletion of Oxtr in Oxtr−/−:Avpr1α−/− double-mutant mice. However, although Oxtr is not indispensable for Avp action in inhibiting osteoblastogenesis and gene expression, Avp-stimulated gene expression is inhibited when the Oxtr is deleted in Avpr1α−/− cells. In contrast, Oxt does not interact with Avprs in vivo in a model of lactation-induced bone loss in which Oxt levels are high. Immunofluorescence microscopy of isolated nucleoplasts and Western blotting and MALDI-TOF of nuclear extracts show that Avp triggers Avpr1α localization to the nucleus. Finally, a specific Avpr2 inhibitor, tolvaptan, does not affect bone formation or bone mass, suggesting that Avpr2, which primarily functions in the kidney, does not have a significant role in bone remodeling.Over the past decade, we have described direct actions of anterior and posterior pituitary hormones on the skeleton (1–8). We have shown that these actions are exerted via G protein-coupled receptors resident on both osteoblasts and osteoclasts. We also find that the skeleton is highly sensitive to the action of posterior pituitary hormones; for example, mice haploinsufficient in oxytocin (Oxt) have osteopenic bones, but lactation is normal; lactation is impaired only in Oxt−/− mice (2). Likewise, Tshr haploinsufficient mice are completely euthyroid with normal thyroid follicles but display significant osteopenia (4). The exquisite sensitivity of the skeleton to pituitary hormones comes as no surprise, considering that the pituitary gland and the skeleton are both evolutionarily more primitive than target endocrine organs (7).Apart from the known actions of growth hormone on the skeleton, Tsh, Fsh, Acth, Oxt, and vasopressin (Avp) have all been shown to regulate the formation and/or function of both osteoblasts and osteoclasts and thus to control bone remodeling in vivo (2–4, 6–8). The two neurohypophyseal hormones Oxt and Avp have opposing functions (2, 3). Oxt stimulates and Avp inhibits osteoblast formation. Consequently, the genetic deletion of the Oxt receptor (Oxtr) and Avp receptor 1α (Avpr1α) yields opposing phenotypes, notably osteopenia in Oxtr−/− mice and high bone mass in Avpr1α−/− mice (2, 3). These findings may explain the rapid recovery of bone loss at weaning when plasma Oxt levels are high (9) and also the profound loss of bone noted in chronic hyponatremic states, such as the syndrome of inappropriate antidiuretic hormone secretion (SIADH), in which serum Avp levels are elevated (3).We find high levels of Oxtr expression on both osteoclasts and osteoblasts (2, 10), in addition to their abundant expression in breast and uterine tissue, where they regulate lactation and parturition, respectively (11). Avpr1αs, in contrast, are distributed more ubiquitously, whereas Avpr2s are localized mainly in the kidney, where they regulate free water excretion (12). Osteoblasts express both Avpr1α and Avrpr2 (3). The only other known isoform, Avpr1β, is expressed predominantly in the pancreas and pituitary; it regulates ACTH secretion from pituitary corticotrophs (13). Sequence alignment shows that the binding sites of the Oxtr and Avprs are highly conserved, with specific amino acids within the predicted binding pocket providing ligand selectivity (14–16). The respective ligands Oxt and Avp also are homologous nonapeptides, differing in only two amino acids, and are known to interact with the other’s receptor with different affinities (17).To our knowledge, osteoblasts and osteoclasts are the only cells in which Oxtr, Avpr1α, and Avpr2 are coexpressed. We also have shown that osteoblastic Oxtrs undergo internalization and nuclear translocation upon binding to Oxt and that this action is independent of cytosolic Erk phosphorylation (18). Avpr1α activation by Avp also activates Erk phosphorylation within minutes (3). The homology between the ligands and their respective receptors and converging downstream signals suggest that Avp and Oxtr may share receptors with opposing or convergent signals. Here, we have explored these interactions in the regulation of osteoblastic bone formation by using mice lacking one or both receptors, chemical inhibitors, and physiological models of high bone turnover. 相似文献
46.
Elisa A. Bradley Ali N. Zaidi Pamela Goldsmith Tracey Sisk David Colombo Sharon Roble David Bradley Curt Daniels 《International journal of cardiology》2014
Major adverse maternal cardiovascular-related events (MAMCRE) in aortopathy patients undergoing pregnancy are poorly defined. The aim was to assess for MAMCRE in pregnant patients with aortopathy or aortic enlargement in conotruncal defects (CTD), and determine if there are differences between groups. 相似文献
47.
Adriana Di Benedetto Li Sun Carlo G. Zambonin Roberto Tamma Beatrice Nico Cosima D. Calvano Graziana Colaianni Yaoting Ji Giorgio Mori Maria Grano Ping Lu Silvia Colucci Tony Yuen Maria I. New Alberta Zallone Mone Zaidi 《Proceedings of the National Academy of Sciences of the United States of America》2014,111(46):16502-16507
48.
The patented Optim coating was designed to prevent insulation abrasions on the Durata lead (St Jude Medical, St Paul, Minnesota) and avoid the problems that had afflicted its predecessor, the Riata silicone lead (St Jude Medical). We report a case of external insulation failure 8 months after implantation of a dual-coil Durata lead and consider the potential causes of the failure. 相似文献
49.
Asimina Dominari Donald Hathaway III Krunal Pandav Wanessa Matos Sharmi Biswas Gowry Reddy Sindhu Thevuthasan Muhammad Adnan Khan Anoopa Mathew Sarabjot Singh Makkar Madiha Zaidi Michael Maher Mourad Fahem Renato Beas Valeria Castaneda Trissa Paul John Halpern Diana Baralt 《World Journal of Virology》2020,9(5):67-78
Thymosin alpha 1 is a peptide naturally occurring in the thymus that has long been recognized for modifying, enhancing, and restoring immune function. Thymosin alpha 1 has been utilized in the treatment of immunocompromised states and malignancies, as an enhancer of vaccine response, and as a means of curbing morbidity and mortality in sepsis and numerous infections. Studies have postulated that thymosin alpha 1 could help improve the outcome in severely ill corona virus disease 2019 patients by repairing damage caused by overactivation of lymphocytic immunity and how thymosin alpha 1 could prevent the excessive activation of T cells. In this review, we discuss key literature on the background knowledge and current clinical uses of thymosin alpha 1. Considering the known biochemical properties including antibacterial and antiviral properties, time-honored applications, and the new promising findings regarding the use of thymosin, we believe that thymosin alpha 1 deserves further investigation into its antiviral properties and possible repurposing as a treatment against severe acute respiratory syndrome coronavirus-2. 相似文献
50.
Shahid Ahmed Nicholas Bosma Michael Moser Shahida Ahmed Bryan Brunet Janine Davies Corinne Doll Dorie-Anna Dueck Christina A. Kim Shuying Ji Duc Le Richard Lee-Ying Howard Lim John Paul McGhie Karen Mulder Jason Park Deepti Ravi Daniel J. Renouf Devin Schellenberg Ralph P. W. Wong Adnan Zaidi 《Current oncology (Toronto, Ont.)》2022,29(3):1796
The Western Canadian Gastrointestinal Cancer Consensus Conference (WCGCCC) convened virtually on 4 November 2021. The WCGCCC is an interactive multi-disciplinary conference attended by health care professionals, including surgical, medical, and radiation oncologists; pathologists; radiologists; and allied health care professionals from across four Western Canadian provinces, British Columbia, Alberta, Saskatchewan, and Manitoba, who are involved in the care of patients with gastrointestinal cancer. They participated in presentation and discussion sessions for the purpose of developing recommendations on the role of systemic therapy and its optimal sequence in patients with resectable metastatic colorectal cancer. 相似文献