全文获取类型
收费全文 | 6120篇 |
免费 | 443篇 |
国内免费 | 6篇 |
出版年
2023年 | 40篇 |
2022年 | 69篇 |
2021年 | 183篇 |
2020年 | 106篇 |
2019年 | 118篇 |
2018年 | 183篇 |
2017年 | 134篇 |
2016年 | 225篇 |
2015年 | 307篇 |
2014年 | 323篇 |
2013年 | 438篇 |
2012年 | 522篇 |
2011年 | 526篇 |
2010年 | 311篇 |
2009年 | 287篇 |
2008年 | 368篇 |
2007年 | 411篇 |
2006年 | 348篇 |
2005年 | 327篇 |
2004年 | 269篇 |
2003年 | 258篇 |
2002年 | 238篇 |
2001年 | 48篇 |
2000年 | 28篇 |
1999年 | 39篇 |
1998年 | 47篇 |
1997年 | 55篇 |
1996年 | 28篇 |
1995年 | 36篇 |
1994年 | 31篇 |
1993年 | 34篇 |
1992年 | 22篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 6篇 |
1984年 | 21篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1973年 | 4篇 |
1960年 | 4篇 |
排序方式: 共有6569条查询结果,搜索用时 15 毫秒
991.
Maria Fesatidou Panagiotis Zagaliotis Charalampos Camoutsis Anthi Petrou Phaedra Eleftheriou Christophe Tratrat Micheline Haroun Athina Geronikaki Ana Ciric Marina Sokovic 《Bioorganic & medicinal chemistry》2018,26(16):4664-4676
In continuation of our efforts to develop new compounds with antimicrobial properties we describe design, synthesis, molecular docking study and evaluation of antimicrobial activity of seventeen novel 2-{[5-(adamantan-1-yl)-1,3,4-thiadiazol-2-yl]-imino}-5-arylidene-1,3-thiazolidin-4-ones. All compounds showed antibacterial activity against eight Gram positive and Gram negative bacterial species. Twelve out of seventeen compounds were more potent than streptomycin and all compounds exhibited higher potency than ampicillin. Compounds were also tested against three resistant bacterial strains: MRSA, P. aeruginosa and E. coli. The best antibacterial potential against ATCC and resistant strains was observed for compound 8 (2-{[5-(adamantan-1-yl)-1,3,4-thiadiazol-2-yl]-imino}-5-(4-nitrobenzylidene)-1,3thiazolidin-4-one). The most sensitive bacterium appeared to be S. typhimirium, followed by B. cereus while L. monocitogenes and M. flavus were the most resistant. Compounds were also tested for their antifungal activity against eight fungal species. All compounds exhibited antifungal activity better than the reference drugs bifonazole and ketokonazole (3-115 times). It was found that compound 8 appeared again to be the most potent. Molecular docking studies on E. coli MurB, MurA as well as C. albicans CYP 51 and dihydrofolate reductase were used for the prediction of mechanism of antibacterial and antifungal activities confirming the experimental results. 相似文献
992.
993.
Pathological lesions and global DNA methylation in rat prostate under streptozotocin‐induced diabetes and melatonin supplementation 下载免费PDF全文
994.
Vonoprazan‐ vs proton‐pump inhibitor‐based first‐line 7‐day triple therapy for clarithromycin‐susceptible Helicobacter pylori: A multicenter,prospective, randomized trial 下载免费PDF全文
995.
Eduard A. Shuralev Nikolai D. Shamaev Malik N. Mukminov Kisaburo Nagamune Yuji Taniguchi Taizo Saito Katsuya Kitoh Marina I. Arleevskaya Anastasiya Yu. Fedotova Diana R. Abdulmanova Natalya M. Aleksandrova Marina A. Efimova Aynur I. Yarullin Anna R. Valeeva Kamil S. Khaertynov Yasuhiro Takashima 《Parasitology international》2018,67(2):112-114
Toxoplasmosis, a most common zoonosis, is caused by the protozoan parasite Toxoplasma gondii. However, there is little epidemiological information on T. gondii infections in humans and livestock animals in Russia. Therefore, in this study, the seroprevalence of T. gondii in goats in Russia was investigated. A total of 216 goats from 32 farms were investigated and 95 of them were seropositive for T. gondii. The difference in seroprevalence between the examined regions was not statistically significant. We next collected serum samples from 99 cats and 181 humans in Kazan city, the state capital of the Republic of Tatarstan, Russia, and examined their T. gondii seroprevalences. Thirty-nine of the 99 cat samples and 56 of the 181 human samples showed seropositivity. Logistical regression analysis revealed that the cat breeding history of the human subjects, but not their sex or age is a significant risk factor for T. gondii seropositivity. These findings suggest that the natural environment in Russia may be widely polluted with T. gondii oocysts shed by cats, and ingestion of these oocysts provides a major route for human infection with this parasite. 相似文献
996.
Molecular evidence and clinical importance of β‐arrestins expression in patients with acromegaly 下载免费PDF全文
Maria Caroline Alves Coelho Marina Lipkin Vasquez Luiz Eduardo Wildemberg Mari C. Vázquez‐Borrego Luciana Bitana Aline Helen da Silva Camacho Débora Silva Liana Lumi Ogino Nina Ventura Leila Chimelli Raul M. Luque Leandro Kasuki Mônica R. Gadelha 《Journal of cellular and molecular medicine》2018,22(4):2110-2116
β‐arrestins seem to have a role in endocytosis and desensitization of somatostatin receptor subtype 2 (sst2) and could be associated with the responsiveness to somatostatin receptor ligands (SRL) in patients with acromegaly. To investigate the in vivo correlation between β‐arrestins 1 and 2 with sst2, sst5 and dopamine receptor subtype 2 (D2) expressions, and the association of β‐arrestins with response to first‐generation SRL and invasiveness in somatotropinomas. β‐arrestins 1 and 2, sst2, sst5 and D2 mRNA expressions were evaluated by quantitative real‐time RT‐PCR on tumoral tissue of 96 patients. Moreover, sst2 and sst5 protein expressions were also evaluated in 40 somatotropinomas by immunohistochemistry. Response to SRL, defined as GH <1 μg/l and normal IGF‐I levels, was assessed in 40 patients. The Knosp‐Steiner criteria were used to define invasiveness. Median β‐arrestin 1, β‐arrestin 2, sst2, sst5 and D2 mRNA copy numbers were 478; 9375; 731; 156 ; and 3989, respectively. There was a positive correlation between β‐arrestins 1 and 2 (R = 0.444, P < 0.001). However, no correlation between β‐arrestins and sst2, sst5 (mRNA and protein levels) or D2 was found. No association was found between β‐arrestins expression and SRL responsiveness or tumour invasiveness. Although previous data suggest a putative correlation between β‐arrestins and sst2, our data clearly indicated that no association existed between β‐arrestins and sst2, sst5 or D2 expression, nor with response to SRL or tumour invasiveness. Therefore, further studies are required to clarify whether β‐arrestins have a role in the response to treatment with SRL in acromegaly. 相似文献
997.
Marina Mikhaylova Julia Bär Bas van Bommel Philipp Schätzle PingAn YuanXiang Rajeev Raman Johannes Hradsky Anja Konietzny Egor Y. Loktionov Pasham Parameshwar Reddy Jeffrey Lopez-Rojas Christina Spilker Oliver Kobler Syed Ahsan Raza Oliver Stork Casper C. Hoogenraad Michael R. Kreutz 《Neuron》2018,97(5):1110-1125.e14
998.
Marina García-Llorente Paula A. Harrison Pam Berry Ignacio Palomo Erik Gómez-Baggethun Irene Iniesta-Arandia Carlos Montes David García del Amo Berta Martín-López 《Biodiversity and Conservation》2018,27(7):1575-1597
Biodiversity conservation strategies that overlook the interests of local people are prone to create conflicts. The ecosystem service approach holds potential for more comprehensively integrating the social dimension into decision-making in protected areas, but its implementation in conservation policies is still in its infancy. This research assesses the extent to which ecosystem services have been implemented in conservation strategies in protected areas. The study was conducted in two outstanding Spanish protected areas, covering a wetland (Doñana Natural and National Parks) and a Mediterranean mountain system (Sierra Nevada Natural and National Parks). Data were collected from deliberative workshops with managers and researchers, face-to-face surveys with users and a review of management plans. We found that, beyond intrinsic values of ecosystems and biodiversity, these areas provide multiple ecosystem services that deserve further attention to ensure their sustained delivery. Our research shows that environmental managers and researchers have different perceptions and priorities regarding ecosystem services management compared with ecosystem service users. Environmental managers and researchers in both protected areas perceived that human-nature relationships and ecosystem services are already widely included in management plans, if often not explicitly. We found that different ecosystem service categories receive uneven attention in management plans. These contained measures to manage provisioning and cultural services whereas measures for managing regulating services were perceived to be largely absent. We conclude by summarizing insights on how the ecosystem service approach may enhance the consideration of social interests in the management of management protected areas. 相似文献
999.
Siem Jakob Veenstra Heinrich Rueeger Markus Voegtle Rainer Lueoend Philipp Holzer Konstanze Hurth Marina Tintelnot-Blomley Mathias Frederiksen Jean-Michel Rondeau Laura Jacobson Matthias Staufenbiel Ulf Neumann Rainer Machauer 《Bioorganic & medicinal chemistry letters》2018,28(12):2195-2200
New amino-1,4-oxazine derived BACE-1 inhibitors were explored and various synthetic routes developed. The binding mode of the inhibitors was elucidated by co-crystallization of 4 with BACE-1 and X-ray analysis. Subsequent optimization led to inhibitors with low double digit nanomolar activity in a biochemical and single digit nanomolar potency in a cellular assays. To assess the inhibitors for their permeation properties and potential to cross the blood-brain-barrier a MDR1-MDCK cell model was successfully applied. Compound 8a confirmed the in vitro results by dose-dependently reducing Aβ levels in mice in an acute treatment regimen. 相似文献