全文获取类型
收费全文 | 62021篇 |
免费 | 2516篇 |
国内免费 | 235篇 |
专业分类
耳鼻咽喉 | 720篇 |
儿科学 | 1514篇 |
妇产科学 | 1371篇 |
基础医学 | 8932篇 |
口腔科学 | 3934篇 |
临床医学 | 5669篇 |
内科学 | 12852篇 |
皮肤病学 | 1597篇 |
神经病学 | 5252篇 |
特种医学 | 1125篇 |
外科学 | 5356篇 |
综合类 | 277篇 |
一般理论 | 32篇 |
预防医学 | 7061篇 |
眼科学 | 960篇 |
药学 | 4469篇 |
12篇 | |
中国医学 | 391篇 |
肿瘤学 | 3248篇 |
出版年
2024年 | 282篇 |
2023年 | 690篇 |
2022年 | 1518篇 |
2021年 | 2625篇 |
2020年 | 1593篇 |
2019年 | 2222篇 |
2018年 | 2569篇 |
2017年 | 1801篇 |
2016年 | 1769篇 |
2015年 | 2174篇 |
2014年 | 2809篇 |
2013年 | 3430篇 |
2012年 | 5277篇 |
2011年 | 5692篇 |
2010年 | 2878篇 |
2009年 | 2379篇 |
2008年 | 3967篇 |
2007年 | 3853篇 |
2006年 | 3394篇 |
2005年 | 3007篇 |
2004年 | 2582篇 |
2003年 | 2268篇 |
2002年 | 2007篇 |
2001年 | 462篇 |
2000年 | 386篇 |
1999年 | 353篇 |
1998年 | 330篇 |
1997年 | 262篇 |
1996年 | 196篇 |
1995年 | 155篇 |
1994年 | 169篇 |
1993年 | 128篇 |
1992年 | 161篇 |
1991年 | 154篇 |
1990年 | 114篇 |
1989年 | 92篇 |
1988年 | 84篇 |
1987年 | 73篇 |
1986年 | 81篇 |
1985年 | 70篇 |
1984年 | 63篇 |
1983年 | 71篇 |
1982年 | 53篇 |
1981年 | 45篇 |
1980年 | 64篇 |
1979年 | 50篇 |
1977年 | 29篇 |
1975年 | 29篇 |
1973年 | 29篇 |
1968年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
It was reviewed a series of 2860 cerebral computed tomography (CCT) in order to compare the main reasons at referral to investigation with the CCT results and the costs with normal and abnormal CCT. It was also studied the age and sex of the patients. Data were collected from one out of three diagnostic centers in Salvador, Brasil, for a three years period. The 2860 CCT exclude all investigation carried out for the follow-up of a previously diagnosed abnormality. CCT abnormalities were detected in 1152 (40.3%). The following reasons showed the highest proportion of abnormal CCT, for males and females respectively: demential syndrome (91.7 and 83.3%); cerebrovascular accidents (85.1 and 73.6%); infectious and parasitary diseases (76.5 and 78.6%); tumors (65.8 and 55.4%); and head injuries, 63.6% for males. In the female group, 65.0% of the CCT were normal, in a range of 65.0 to 80.0% for the age groups under 54 years old. In the male group, the highest proportion of normal CCT was found in the age groups: 25-34 (68.4%), < 15 (62.9%) and 35-44 (62.7%). The most common reasons for normal CCT for males and females were: headache (81.3 and 87.5%); dizziness/vertigo (79.3 and 78.6%); seizures (67.3 and 70.0%); psychomotor deficiency (72.0 and 67.7%) and "endocrine disorders", 75.0% for each sex. The highest proportion of normal CCT (65.3%) was requested by medical "convenios". The cost with normal CCT reached US$565,225 and with the abnormal ones, US$381,247. Costs with normal CCT were 2.2 higher for medical "convenios" as compared to those of the National Institute of Security requests and 2.8 more than those of private medicine. 相似文献
82.
Activins are members of the transforming growth factor-beta (TGFbeta) superfamily, which regulate cell differentiation processes. Here we report the first quantitative analysis of the expression of Activin/Inhibin ligands, type I and II receptors, as well as Smad proteins in fetal (E14-E16) and adult thymic subpopulations. Our data showed that Alk4, ActRIIA, ActRIIB, and Smads 2, 3, and 4, are expressed in fetal thymus (E14 > E15 > E16) and in thymocytes from adult mice (mostly in the double negative [DN] subpopulation). Ligand expression analysis showed that betaA, betaB, and alpha subunits were mainly detected in thymic stromal cells. Interestingly, alpha subunits were expressed at much higher levels compared to betaA and betaB subunits, demonstrating for the first time the potential role of Inhibins as important mediators during early T cell development. Our data indicate that Activin/Inhibin signaling could regulate the process of thymus organogenesis and early thymocyte differentiation, as it has been demonstrated for other members of the TGF-beta superfamily. 相似文献
83.
L. Freire-Maia A. D. Lemos Fernandes A. D. Azevedo Suely B. Oliveira W. Dias da Silva 《Inflammation research》1973,3(5):326-331
The intravenous injection of rabbit anti-rat kidney serum in rats produces, with a latency of 30 to 60 seconds, the triad sinus bradycardia (or S-A blockade), systemic hypotension and apnea. Recordings of the intracardiac pressures showed a rise in the right and a simultaneous fall in the left ventricular pressure, 30 to 60 seconds after the serum injection. These initial effects were followed by pulmonary edema and death. Bilateral vagotomy prevented the bradycardia and apnea, but not the intracardiac changes, edema and death. Atropine also prevented the bradycardia, but not the apnea, edema and death. Experiments using alpha and beta adrenergic blocking agents seem to indicate that the edema is not caused by the release of catecholamines. It is suggested that the edema could be explained by a rise in the pulmonary capillary pressure, due to the antigen-antibody reaction. The triad bradycardia, systemic hypotension and apnea seems to be the first sign of the pulmonary edema, is reflex in nature, and is assumed to be due to stimulation of J receptors in the lungs, by a mechanical effect (edema). Phenylbutazone and acetylsalicylic acid give a partial protection against the pulmonary edema. Ultramorphological observations of lungs with edema were described. 相似文献
84.
Albertini-Yagi CS Oliveira RC Vieira JE Negri EM de Oliveira LR Saldiva PH Lorenzi-Filho G 《Respiratory physiology & neurobiology》2005,145(1):101-110
The study objectives were to compare in vitro transportability and physical properties of respiratory mucus, obtained invasively by direct collection (DC) right after endotracheal intubation and non-invasively by sputum induction with 3% hypertonic saline solution inhalation (SI) 24 h before the anesthesia. Twenty-two patients with no pulmonary disease scheduled for elective abdominal surgical procedures were studied. The parameters analyzed and the main results are as follows. (1) Transportability by cilia (MCT), SI was higher than DC (0.94+/-0.25 and 0.62+/-0.25; P<0.001). There was a significant correlation between the two methods and DC could be estimated by: DC=0.21+(0.44 SI) (r=0.44; P<0.001). (2) Transportability by cough (CC), SI was higher than DC (68.23+/-32.1 and 33.58+/-19.04 mm; P=0.002). (3) Contact angle (CA), SI was lower than DC (10+/-3 degrees and 22+/-14 degrees ; P=0.025). (4) Rheological properties (no significant difference obtained between SI and DC). These results indicated that SI changes mucus physical properties and transportability in non-expectorators. 相似文献
85.
Delaugerre C Teglas JP Treluyer JM Vaz P Jullien V Veber F Rouzioux C Chaix ML Blanche S 《Journal of acquired immune deficiency syndromes (1999)》2004,37(2):1269-1275
Predictive factors of the virologic success of the use of lopinavir/ritonavir (LPV/r) in HIV-infected children are unknown, especially in children who have been pretreated with protease inhibitors (PIs). This longitudinal, single-center, observational study included 69 children (21 PI-naive and 48 PI-experienced) who had received LPV/r for at least 3 months. The mean (+/- SD) age was 10.3 +/- 4.8 years, and the mean baseline of CD4 percentage and HIV-1 RNA was 14.9% +/- 9.8% and 4.8 +/- 1.05 log10 copies/mL, respectively. The mean duration of follow-up was 16.5 +/- 8.3 months. At 6, 12, and 18 months, 52%, 57%, and 49% of all children, respectively, had a viral load less than 50 copies/mL. The risk of virologic failure, defined as 2 consecutive viral loads greater than 1000 copies/mL, was significantly higher when the children were previously treated with PIs and when the baseline LPV mutation score exceeded 3 mutations. In the pretreated children, the ratio of the plasma LPV maximal concentration to the baseline LPV score mutation was also associated with failure, independently of resistance score. Finally, in children failing an LPV-containing regimen, accumulation of additional PI-associated resistance mutations was evidenced in viral isolates from children with prior PI treatment, even with viral replication levels less than 10,000 copies/mL. In pretreated children, LPV plasma levels should be optimized in an attempt to achieve sufficient drug concentrations to overcome the resistance level. 相似文献
86.
87.
The technique for ultrastructural localization of argyrophilic proteins was modified and NOR-Silver staining methods were applied to the study of the distribution of these proteins in the spermatic cells of Nucella lapillus (Gastropoda, Prosobranchia). Two types of selective silver deposits were found during the different phases of spermiogenesis and in mature spermatozoa. Argyrophilic nuclear, nucleolar and cytoplasmic proteins were simultaneously detected by improvement of a modified one-step silver technique. 相似文献
88.
Ana Velasco Victor Palomar-Asenjo Laura Ga?an Lluis Catasus Nuria Llecha Angel Panizo Victor Palomar-Garcia Miquel Quer Xavier Matias-Guiu 《Diagnostic molecular pathology》2005,14(2):109-114
The familial paraganglioma syndrome is an autosomal dominant disorder characterized by the presence of carotid body paragangliomas and, less frequently, paragangliomas of the glomus jugulare, glomus vagale, and adrenal pheochromocytomas. Germline mutations of the genes for succinate dehydrogenase subunits D, B, or C (SDHD, SDHB, SDHC) have been identified in some kindreds with familial paraganglioma. In this study, we report the clinicopathologic features of four different kindreds with familial paraganglioma, which were screened for germline mutations in the SDHD gene. DNA was obtained from tumor and normal tissue, as well as from peripheral blood. Mutation analysis was performed by single-strand conformation polymorphism analysis and DNA sequencing. SDHD germline mutations were detected in the affected family members of the four families, as well as in several asymptomatic carriers. An identical mutation in exon 4 of SDHD (334-337delACTG) was identified in two apparently unrelated kindreds. The third family showed a germline mutation in exon 2 (W43X). The mutations present in these three families had been previously described in Spanish families, suggesting a founder effect. The fourth family exhibited a mutation in exon 2 of SDHD (170-171delTT), which had not been previously identified. The affected family members of the four kindreds showed paragangliomas, located in the head and neck region, and all of them were benign. These results confirm that genetic testing of SDHD may be a powerful tool for the identification of the syndrome in patients with multiple or bilateral paragangliomas. 相似文献
89.
Rocha AM Rocha GA Santos A de Oliveira CA Queiroz DM 《Journal of clinical microbiology》2003,41(1):447-448
We validated a commercial enzyme-linked immunosorbent assay for the detection of anti-CagA antibodies in Brazilian patients with Helicobacter pylori infection. The test presented high sensitivity (97.4%) and specificity (88.9%) when employed in patients without gastric carcinoma. However, in gastric carcinoma patients, the test was neither sensitive nor specific enough to detect cagA-positive H. pylori infection. 相似文献
90.
Campos B Díez O Odefrey F Domènech M Moncoutier V Martínez-Ferrandis JI Osorio A Balmaña J Barroso A Armengod ME Benítez J Alonso C Stoppa-Lyonnet D Goldgar D Baiget M 《Human mutation》2003,21(4):452-452
A frame-shift 9254del5 mutation was independently identified in 12 families, eleven of them with Spanish ancestors, in a BRCA2 screening performed in 841 breast and/or ovarian cancer families and in 339 women with breast cancer diagnosed before the age of 40 at different centers in France and Spain. We sought to analyze in detail the haplotype and founder effects of the 9254del5 and to estimate the time of origin of the mutation. Eight polymorphic microsatellite markers and two BRCA2 polymorphisms were used for the haplotype analyses. The markers were located flanking the BRCA2 gene spanning a region of 6.1 cM. Our results suggest that these families shared a common ancestry with BRCA2 9254del5, which is a founder mutation originating in the Northeast Spanish, with an estimated age of 92 (95% CI 56-141) generations. 相似文献