全文获取类型
收费全文 | 9206篇 |
免费 | 535篇 |
国内免费 | 32篇 |
专业分类
耳鼻咽喉 | 110篇 |
儿科学 | 225篇 |
妇产科学 | 227篇 |
基础医学 | 1320篇 |
口腔科学 | 886篇 |
临床医学 | 692篇 |
内科学 | 1898篇 |
皮肤病学 | 178篇 |
神经病学 | 834篇 |
特种医学 | 202篇 |
外科学 | 875篇 |
综合类 | 47篇 |
预防医学 | 1061篇 |
眼科学 | 131篇 |
药学 | 540篇 |
中国医学 | 72篇 |
肿瘤学 | 475篇 |
出版年
2023年 | 76篇 |
2022年 | 174篇 |
2021年 | 287篇 |
2020年 | 221篇 |
2019年 | 320篇 |
2018年 | 358篇 |
2017年 | 226篇 |
2016年 | 278篇 |
2015年 | 312篇 |
2014年 | 425篇 |
2013年 | 514篇 |
2012年 | 777篇 |
2011年 | 810篇 |
2010年 | 405篇 |
2009年 | 333篇 |
2008年 | 540篇 |
2007年 | 566篇 |
2006年 | 472篇 |
2005年 | 412篇 |
2004年 | 370篇 |
2003年 | 370篇 |
2002年 | 278篇 |
2001年 | 191篇 |
2000年 | 157篇 |
1999年 | 127篇 |
1998年 | 52篇 |
1997年 | 34篇 |
1996年 | 26篇 |
1995年 | 38篇 |
1994年 | 28篇 |
1993年 | 22篇 |
1992年 | 50篇 |
1991年 | 63篇 |
1990年 | 43篇 |
1989年 | 38篇 |
1988年 | 29篇 |
1987年 | 25篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 14篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 13篇 |
1974年 | 17篇 |
1973年 | 14篇 |
1971年 | 20篇 |
1970年 | 21篇 |
1967年 | 12篇 |
1966年 | 14篇 |
排序方式: 共有9773条查询结果,搜索用时 31 毫秒
41.
Permeability of pure lipid bilayers to melatonin 总被引:9,自引:1,他引:8
Ernane J.X. Costa Roberto Harzer Lopes M. Teresa Lamy-Freund 《Journal of pineal research》1995,19(3):123-126
Abstract: Melatonin, the chief hormone of the pineal gland, has been reported to interact with a variety of different cells. This ubiquitously acting hormone has been found to interact with protein receptors both at the cell membrane and in the nucleus. Moreover, melatonin was recently shown to be a very potent hydroxyl radical scavenger. The present work focuses on the interaction of melatonin with pure lipid bilayers. It is shown that melatonin can cross multilamellar lipid vesicles, which are used here as model systems for the lipid phase of biological membranes. Thus, the data prove that melatonin can easily pass through the cell membrane and bath every part of the cell, as previously suggested in the literature. Melatonin lipid association constant was calculated based on the change of the hormone fluorescence intensity due to its penetration into the hydrophobic lipid phase. Though melatonin was recently shown to be highly soluble in aqueous media, its lipid association constant is rather high, indicating that the biological action of the hormone is likely to be at the membrane level, either via its interaction with membrane receptors, and/or as a lipoperoxidation radical scavenger. 相似文献
42.
43.
Maria Guiomar A Bahia Vicente Tadeu Lopes Buono 《Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics》2005,100(2):249-255
OBJECTIVE: The changes in fatigue resistance of nickel-titanium rotary ProFile instruments after clinical use for shaping 10 curved molar root canals were evaluated in this study. STUDY DESIGN: Twenty-five sets of files #20, #25, and #30 and tapers .04 and .06 were divided into 2 groups, one with 10 sets of new files that were tested in a fatigue test bench device as a control. The other, experimental group, with 15 sets of clinically used files, was tested in the same device. The Student t test was employed to compare mean values of the measured parameters. RESULTS: A statistically significant decrease in the number of cycles to failure was determined for the clinically used files, as compared with the new ones. The fracture point was the same for all files tested. CONCLUSIONS: The clinical use of ProFile instruments for shaping curved canals reduces their fatigue resistance. 相似文献
44.
45.
Meyer-Fernandes JR Saad-Nehme J Peres-Sampaio CE Belmont-Firpo R Bisaggio DF Do Couto LC Fonseca De Souza AL Lopes AH Souto-Padrón T 《Parasitology research》2004,93(1):41-50
In this work, we describe the ability of living epimastigotes of Trypanosoma cruzi to hydrolyze extracellular ATP. In these intact parasites, there was a low level of ATP hydrolysis in the absence of any divalent metal (2.42±0.31 nmol Pi/h×108 cells). ATP hydrolysis was stimulated by MgCl2, and the Mg-dependent ecto-ATPase activity was 27.15±2.91 nmol Pi/h×108 cells. The addition of MgCl2 to the extracellular medium increased the ecto-ATPase activity in a dose-dependent manner. This stimulatory activity was also observed when MgCl2 was replaced by MnCl2, but not by CaCl2 or SrCl2. The apparent Km for Mg-ATP2– was 0.61 mM, and free Mg2+ did not increase the ecto-ATPase activity. This ecto-ATPase activity was insensitive to the inhibitors of other ATPase and phosphatase activities. To confirm that this Mg-dependent ATPase was an ecto-ATPase, we used an impermeant inhibitor, DIDS (4, 4.diisothiocyanostylbene 2-2-disulfonic acid) as well as suramin, an antagonist of P2 purinoreceptors and inhibitor of some ecto-ATPases. These two reagents inhibited the Mg2+-dependent ATPase activity in a dose-dependent manner. A comparison among the Mg2+-ecto-ATPase activities of the three forms of T. cruzi showed that the noninfective epimastigotes were less efficient at hydrolyzing ATP than the infective trypomastigote and amastigote stages. 相似文献
46.
Connective tissue growth factor expression and Smad signaling during mouse heart development and myocardial infarction. 总被引:5,自引:0,他引:5
Susana M Chuva de Sousa Lopes Alie Feijen Jeroen Korving Olexander Korchynskyi Jonas Larsson Stefan Karlsson Peter ten Dijke Karen M Lyons Roel Goldschmeding Pieter Doevendans Christine L Mummery 《Developmental dynamics》2004,231(3):542-550
Connective tissue growth factor (CTGF) is reported to be a target gene of transforming growth factor beta (TGFbeta) and bone morphogenetic protein (BMP) in vitro. Its physiological role in angiogenesis and skeletogenesis during mouse development has been described recently. Here, we have mapped expression of CTGF mRNA during mouse heart development, postnatal adult life, and after experimental myocardial infarction. Furthermore, we investigated the relationship between CTGF and the BMP/TGFbeta signaling pathway in particular during heart development in mutant mice. Postnatally, CTGF expression in the heart became restricted to the atrium. Strikingly, 1 week after myocardial infarction, when myocytes have disappeared from the infarct zone, CTGF and TGFbeta expression as well as activated forms of TGFbeta but not BMP, Smad effector proteins are colocalized exclusively in the fibroblasts of the scar tissue, suggesting possible cooperation between CTGF and TGFbeta during the pathological fibrotic response. 相似文献
47.
M.?OleastroEmail author M.?Gerhard A.?I.?Lopes P.?Ramalho J.?Cabral A.?Sousa Guerreiro L.?Monteiro 《European journal of clinical microbiology & infectious diseases》2003,22(2):85-91
The aim of this study was to evaluate the prevalence of virulence genotypes, namely cagA, vacA and babA2, of Helicobacter pylori strains isolated from Portuguese adults and children presenting gastroduodenal pathology. One hundred thirty-six strains
were studied, 82 isolated from adult patients (50 with nonulcerative gastritis and 32 with active peptic ulcer) and 58 isolated
from children (54 with nonulcerative gastritis and 4 with duodenal ulcer). Genotyping of cagA, vacA and babA2 was assessed by polymerase chain reaction. Overall, Helicobacter pylori strains carrying more virulent genotypes were much more prevalent in adults than in children, particularly the type I (vacAs1- and cagA-positive) and the triple-positive (vacAs1-, cagA- and babA2-positive) strains (P<0.001). A subpopulation of adults and children with nonulcerative gastritis was also studied, and differences in the prevalence
of virulent genotypes were observed, either for individual genotypes (P=0.017 for cagA, P=0.010 for vacAs1) or in combinations, i.e. the type I genotype (P=0.005) and the triple-positive strains (P=0.031). There was no difference between the two populations in the distribution of babA2 and m1/m2 genotypes. Considering the cohort effect in the epidemiology of Helicobacter pylori infection, these results suggest that different strains might circulate during different periods of time, or that, after
infection in childhood, individual strains will undergo changes during the course of infection.
Electronic Publication 相似文献
48.
Espinosa LE Li Z Gomez Barreto D Calderon Jaimes E Rodriguez RS Sakota V Facklam RR Beall B 《Journal of clinical microbiology》2003,41(1):373-378
To examine the type distribution of pathogenic group A streptococcal (GAS) strains in Mexico, we determined the emm types of 423 GAS isolates collected from ill patients residing in Mexico (Durango or Mexico City). These included 282 throat isolates and 107 isolates from normally sterile sites. Of the other isolates, 38 were recovered from other miscellaneous infections. A total of 31 different emm types were found, revealing a broad overlap between commonly occurring emm types in Mexico and the United States. The information obtained in this study is consistent with the possibility that multivalent, M type-specific vaccines prepared for GAS strain distribution within the United States could theoretically protect against the majority of GAS strains causing disease in the two cities surveyed in Mexico. 相似文献
49.
Marinho J Galvão-Castro B Rodrigues LC Barreto ML 《Journal of acquired immune deficiency syndromes (1999)》2005,40(5):625-628
OBJECTIVES: To investigate whether infection with human T-lymphotropic virus type 1 (HTLV-1) increases the risk of tuberculosis. DESIGN: A case-control study. SETTING: City of Salvador, Brazil. PARTICIPANTS: A total of 375 patients with tuberculosis (cases) and 378 individuals without tuberculosis (controls), matched by age and sex. MAIN OUTCOME MEASURE: Tuberculosis of lung or lymph node. MAIN EXPOSURE: Human HTLV-1 infection. RESULTS: The prevalence of HTLV-1 infection was 4.27% (16/375) in patients with tuberculosis and 1.32% (5/378) in controls, resulting in a crude odds ratio of 3.31 (95% CI, 1.20-9.13) and an adjusted odds ratio of 3.01 (95% CI, 1.06-8.58). CONCLUSION: HTLV-1 infection is associated with a first diagnosis of tuberculosis. This may have implications for tuberculosis control in places with high prevalence of HTLV-1. 相似文献
50.
A family study is presented in which the father of a girl with severe cystic fibrosis (CF) was also found to have CF but was mildly affected. He was diagnosed with three positive sweat tests including one after suppression with fludrocortisone. Genetic analysis showed that he is a compound heterozygote with the delta F508 CF mutation associated with haplotype B and a second CF mutation associated with haplotype C. In this unusual, fertile CF male, the late age of diagnosis (30 years) and the mild clinical picture suggest that the compound genotype (delta F508/other CF mutation) determines a much less severe form of the disease which might have gone unnoticed in the absence of a severely affected child. The implications of these findings for genetic counselling of families with CF are discussed. 相似文献