全文获取类型
收费全文 | 713篇 |
免费 | 202篇 |
国内免费 | 33篇 |
专业分类
儿科学 | 31篇 |
妇产科学 | 5篇 |
基础医学 | 100篇 |
口腔科学 | 14篇 |
临床医学 | 85篇 |
内科学 | 153篇 |
皮肤病学 | 2篇 |
神经病学 | 55篇 |
特种医学 | 62篇 |
外科学 | 55篇 |
综合类 | 50篇 |
预防医学 | 173篇 |
眼科学 | 52篇 |
药学 | 82篇 |
中国医学 | 1篇 |
肿瘤学 | 28篇 |
出版年
2018年 | 9篇 |
2017年 | 9篇 |
2015年 | 10篇 |
2014年 | 23篇 |
2013年 | 30篇 |
2012年 | 17篇 |
2011年 | 29篇 |
2010年 | 17篇 |
2009年 | 23篇 |
2008年 | 27篇 |
2007年 | 33篇 |
2006年 | 31篇 |
2005年 | 27篇 |
2004年 | 25篇 |
2003年 | 13篇 |
2002年 | 16篇 |
2001年 | 24篇 |
2000年 | 12篇 |
1999年 | 29篇 |
1998年 | 22篇 |
1997年 | 25篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 15篇 |
1991年 | 20篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 18篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 19篇 |
1979年 | 16篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 16篇 |
1975年 | 10篇 |
1973年 | 16篇 |
1972年 | 12篇 |
1971年 | 6篇 |
1970年 | 12篇 |
1969年 | 9篇 |
1968年 | 10篇 |
1966年 | 6篇 |
1965年 | 6篇 |
排序方式: 共有948条查询结果,搜索用时 15 毫秒
1.
Neuroimaging in Pineal Tumors 总被引:4,自引:0,他引:4
F Reis MD AV Faria MD PhD VA Zanardi MD PhD JR Menezes MD F Cendes MD PhD LS Queiroz MD PhD 《Journal of neuroimaging》2006,16(1):52-58
BACKGROUND AND PURPOSE: The authors report radiological findings in 11 tumors in the pineal region, which were histologically diagnosed as germinomas, pineocytomas pineoblastomas, ependymomas, teratomas, and astrocytomas. METHODS: Computed tomography (CT) was performed in seven patients and magnetic resonance imaging (MRI) was performed in all patients. RESULTS: CT showed a solid or solid/cystic mass with variable contrast enhancement. MRI showed a heterogeneous mass, with hypointense signal on T1 and iso/hyperintense signal on T2-weighted images (WI) and gadolinium enhancement. Extension to adjacent structures occurred in five patients and spread through the cerebral spinal fluid (CSF) in two. CONCLUSIONS: Pineal region tumors have no pathognomonic imaging pattern. MRI and CT are complementary in diagnosis and are important to determine localization, extension, and meningeal spread. 相似文献
2.
3.
K J Acheson E Ravussin D A Schoeller L Christin L Bourquin P Baertschi E Danforth E Jéquier 《Metabolism: clinical and experimental》1988,37(1):91-98
Seven lean healthy young men were studied for 6 weeks during exposure to pharmacologic inhibition or stimulation of the sympathetic nervous system. For a period of 2 weeks their beta-adrenergic receptors were either blocked with propranolol hydrochloride (160 mg/d) or stimulated with terbutaline sulphate (15 mg/d). After a further 2 weeks of placebo administration (500 mg lactose/d), the subjects crossed over to the drug they had not been taking at the beginning of the experiment for another 14 days. During the last five days of each 2-week period, the subjects consumed a weight-maintaining diet, composed of 12% protein, 48% carbohydrate, and 40% fat. They consumed exactly the same menus on the same days during the subsequent study periods. Body weight and physical activity were measured every day for 6 weeks. Daily heart rate and nitrogen excretion were measured continuously for days at the end of each 2-week period, the last two days of which were spent in a respiration chamber where energy expenditure and a variety of metabolic parameters were measured. In the respiration chamber on the propranolol, placebo, and terbutaline treatments, respectively, significant differences were observed in mean daily heart rate (65 +/- 3, 75 +/- 4, and 84 +/- 4 beats/min), mean sleeping heart rate (51 +/- 2, 56 +/- 3, and 62 +/- 3 beats/min), nitrogen excretion (13.6 +/- 0.7, 12.6 +/- 0.6, and 11.9 +/- 0.6 g/d), fat oxidation (+1,045 +/- 95, +1,243 +/- 148, and +1,278 +/- 84 kcal/d) and thyroid hormones (12.0 +/- 0.7, 15.7 +/- 0.9, and 17.2 +/- 1.0 T3/T4 ratio).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
5.
Structural proteins of Semliki Forest virus and its nucleocapsid 总被引:7,自引:0,他引:7
6.
Human neutrophils and their products induce Shiga toxin production by enterohemorrhagic Escherichia coli
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The Shiga toxins (Stx) are critical virulence factors for Escherichia coli O157:H7 and other serotypes of enterohemorrhagic E. coli (EHEC). These potent toxins are encoded in the genomes of temperate lambdoid bacteriophages. We recently demonstrated that induction of the resident Stx2-encoding prophage in an O157:H7 clinical isolate is required for toxin production by this strain. Since several factors produced by human cells, including hydrogen peroxide (H2O2), are capable of inducing lambdoid prophages, we hypothesized that such molecules might also induce toxin production by EHEC. Here, we studied whether H2O2 and also human neutrophils, an important endogenous source of H2O2, induced Stx2 expression by an EHEC clinical isolate. Both H2O2 and neutrophils were found to augment Stx2 production, raising the possibility that these agents may lead to prophage induction in vivo and thereby contribute to EHEC pathogenesis. 相似文献
7.
Molecular characterization of a serotype O121:H19 clone,a distinct Shiga toxin-producing clone of pathogenic Escherichia coli
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tarr CL Large TM Moeller CL Lacher DW Tarr PI Acheson DW Whittam TS 《Infection and immunity》2002,70(12):6853-6859
Most illnesses caused by Shiga toxin-producing Escherichia coli (STEC) have been attributed to E. coli serotype O157:H7, but non-O157 STEC infections are now increasingly recognized as public health problems worldwide. The O121:H19 serotype is being isolated more frequently from clinical specimens and has been implicated in one waterborne outbreak. We used multilocus virulence gene profiling, a PCR-based assay, to characterize the virulence gene content of 24 isolates of serotype O121:H19 and nonmotile variants. We also performed multilocus enzyme electrophoresis and multilocus sequencing to establish the clonal relatedness of O121 isolates and to elucidate the relationship of O121 to common STEC clones. The 24 isolates were found to represent a single bacterial clone, as there was no allelic variation across 18 enzyme loci among the isolates. The complete nucleotide sequence of the intimin gene differed by four substitutions from that of the epsilon (Int- epsilon ) allele of O103:H2 strain PMK5. The typical O121 virulence gene profile was similar to the profiles of enterohemorrhagic E. coli (EHEC) clones of E. coli: it included a Shiga toxin 2 gene (stx(2)), two genes on the EHEC plasmid (toxB and ehxA), and the gene encoding intimin (eae). Despite the similarities, putative virulence genes distributed on O islands-large chromosomal DNA segments present in the O157:H7 genome-were useful for discriminating among STEC serotypes and the O121:H19 clone had a composite profile that was distinct from the profiles of the other major EHEC clones of pathogenic E. coli. On the basis of sequencing analysis with 13 housekeeping genes, the O121:H19 clone did not fall into any of the four classical EHEC and enteropathogenic E. coli groups but instead was closely related to two eae-negative STEC strains. 相似文献
8.
9.
Jiang WZ Jin NY Li ZJ Zhang LS Wang HW Zhang YJ Han WY 《第二军医大学学报》2006,27(4):434-434
To express the core protein of HIV-1 of Chinese prevalent strain (HIV-1 (CN)) in Pichia pastoris, the fulllength gag gene was inserted into the secretory expression vector pHILS1. Linearized recombinant plasmid pHILGAG by Sail was electrotransformed into the yeast strain GS115, and the yeast transformants were identified by PCR. To induce the interest protein to be expressed, the PCR positive transformants were inoculated in the medium of BMGY and BMMY, mRNA of the strain was detected by RT-PCR, and the expressed protein was analyzed by SDS-PAGE, Western blotting and thin layer scanning. mRNA (1.3 kb) was amplified by RT-PCR. SDS-PAGE and Western blotting analysis showed that the molecular mass of the expressed protein was 55 kD, which was similar to the expected value, and the expressed protein could react with McAb to HIV-1 p24. Thin layer scanning analysis demonstrated that the whole amount of the expressed protein was approximately 13 % of the soluble protein in the supernatant. The recombinant yeast had good genetic stability. The optimal expression conditions of the engineering yeast were as follows: BMMY medium, 80-90% of dissolved oxygen, 1% methanol, and 3-day-cultivation course. Gag proteins were expressed under the optimal expression condition and purified via gel filtration chromatography. The purity of the interest protein was up to 85 %. After the purified proteins were inoculated into BALB/c mice, the anti-HIV-1 antibodies in the immunized mice could be detected by Western blotting. 相似文献
10.
Philip Conaghan Charles Maxwell-Armstrong Nigel Bedforth Chris Gornall Bryn Baxendale Li-lin Hong Hyun-Mi Carty Austin G. Acheson 《Surgical endoscopy》2010,24(10):2480-2484