全文获取类型
收费全文 | 170848篇 |
免费 | 9798篇 |
国内免费 | 471篇 |
专业分类
耳鼻咽喉 | 2230篇 |
儿科学 | 5549篇 |
妇产科学 | 3589篇 |
基础医学 | 23116篇 |
口腔科学 | 7539篇 |
临床医学 | 12524篇 |
内科学 | 38343篇 |
皮肤病学 | 4340篇 |
神经病学 | 14180篇 |
特种医学 | 5383篇 |
外国民族医学 | 26篇 |
外科学 | 21045篇 |
综合类 | 1400篇 |
现状与发展 | 1篇 |
一般理论 | 60篇 |
预防医学 | 17812篇 |
眼科学 | 3156篇 |
药学 | 10357篇 |
1篇 | |
中国医学 | 688篇 |
肿瘤学 | 9778篇 |
出版年
2023年 | 889篇 |
2022年 | 1939篇 |
2021年 | 3615篇 |
2020年 | 2422篇 |
2019年 | 3416篇 |
2018年 | 4825篇 |
2017年 | 3619篇 |
2016年 | 3365篇 |
2015年 | 3942篇 |
2014年 | 5410篇 |
2013年 | 6839篇 |
2012年 | 10627篇 |
2011年 | 11118篇 |
2010年 | 5615篇 |
2009年 | 5062篇 |
2008年 | 8594篇 |
2007年 | 9230篇 |
2006年 | 8544篇 |
2005年 | 8820篇 |
2004年 | 8309篇 |
2003年 | 7587篇 |
2002年 | 5651篇 |
2001年 | 4953篇 |
2000年 | 4959篇 |
1999年 | 4353篇 |
1998年 | 1580篇 |
1997年 | 1329篇 |
1996年 | 1322篇 |
1995年 | 1121篇 |
1994年 | 1099篇 |
1993年 | 1006篇 |
1992年 | 2651篇 |
1991年 | 2577篇 |
1990年 | 2346篇 |
1989年 | 2349篇 |
1988年 | 2128篇 |
1987年 | 1971篇 |
1986年 | 1839篇 |
1985年 | 1764篇 |
1984年 | 1260篇 |
1983年 | 1021篇 |
1982年 | 579篇 |
1981年 | 522篇 |
1980年 | 506篇 |
1979年 | 923篇 |
1978年 | 609篇 |
1977年 | 484篇 |
1975年 | 546篇 |
1974年 | 540篇 |
1973年 | 541篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Human immunodeficiency virus infection in urban Rwanda. Demographic and behavioral correlates in a representative sample of childbearing women 总被引:9,自引:0,他引:9
S Allen C Lindan A Serufilira P Van de Perre A C Rundle F Nsengumuremyi M Carael J Schwalbe S Hulley 《JAMA》1991,266(12):1657-1663
OBJECTIVE.--To determine behavioral and demographic risk factors for human immunodeficiency virus (HIV) infection in central Africa. DESIGN.--Cross-sectional survey. SETTING.--Kigali, Rwanda. PARTICIPANTS.--A representative sample of 1458 childbearing women aged 19 to 37 years who were recruited from outpatient prenatal and pediatric clinics at the only community hospital in the city. MAIN OUTCOME MEASURE.--Antibodies to HIV assessed by enzyme immunoassay and confirmed by Western blot or indirect immunofluorescence. RESULTS.--The HIV seroprevalence was 32% overall. Infection rates were higher in women who were single, in those in steady relationships that began after 1981, and in the 33% of women reporting more than one lifetime sexual partner. Women in legal marriages or monogamous partnerships had lower rates of infection, but even low-risk women had prevalences on the order of 20%. History of venereal disease in the past 5 years, although the strongest risk factor in a multiple logistic analysis (odds ratio, 2.7; 95% confidence interval, 2.0 to 3.7), was reported by only 30% of those infected. Having a male sexual partner who drank alcohol or who had higher income were significant risk factors for HIV infection in the multivariate analysis, but use of oral contraceptives and having an uncircumcised partner were not. CONCLUSIONS.--The epidemic of the acquired immunodeficiency syndrome in Rwanda has spread beyond high-risk groups to the general population of women without known risk factors. For most of these women, a steady male partner is the source of their HIV risk and therefore a vital target for intervention efforts. 相似文献
32.
33.
Esparza-Gordillo Jorge; Goicoechea de Jorge Elena; Buil Alfonso; Berges Luis Carreras; Lopez-Trascasa Margarita; Sanchez-Corral Pilar; Rodriguez de Cordoba Santiago 《Human molecular genetics》2005,14(8):1107
Some MCP SNP and aHUS-associated MCP mutation 相似文献
34.
B Sarmento D C Ferreira L Jorgensen M van de Weert 《European journal of pharmaceutics and biopharmaceutics》2007,65(1):10-17
The aim of the present study was to probe the structural integrity of insulin after being entrapped into chitosan/alginate nanoparticles produced by ionotropic polyelectrolyte pre-gelation. By manipulating the alginate:chitosan mass ratio and the pH during nanoparticle production, desired nanoparticles with a mean size of 850 (+/-88)nm and insulin association efficiency of 81 (+/-2)% were obtained. Insulin secondary structure was assessed by Fourier transform infrared (FTIR) and circular dichroism (CD) after entrapment into nanoparticles and after release from the particles under gastrointestinal simulated conditions. FTIR second-derivative spectra and area-overlap compared to an insulin standard confirmed that no significant conformational changes of insulin occurred in terms of alpha-helix and beta-sheet content. Far-UV-CD spectra corroborated the preservation of insulin structure during the nanoparticle production procedure. The presented nanoparticulate system is a promising carrier for insulin oral delivery since it preserves insulin structure and therefore also, potentially, its bioactivity. 相似文献
35.
L. van den Bemt M. P. de Vries L. van Knapen M. Jansen M. Goossens J. W. M. Muris C. P. van Schayck 《Clinical and experimental allergy》2006,36(2):233-237
BACKGROUND: Exposure to a high level of house dust mite allergens (HDMAs) is considered as a risk factor for HDM sensitization and development of asthma in genetically disposed people. Mattresses are one of the most important sources of HDMA in people's living environment. OBJECTIVE: The aim of this study was to evaluate the association between mattress characteristics and HDMA concentrations on mattresses. METHODS: Dust samples of mattress surfaces were taken to evaluate the level of Der p 1 allergen. All participants filled in a questionnaire about the type of mattress, the type of covering (upper layer) of the mattress, dwelling characteristics and cleaning habits. Humidity and temperature of the bedroom were measured at the time of dust sampling. RESULTS: One hundred and sixty-eight questionnaires were filled in. Synthetic upper layer of the mattress was associated with a higher level of Der p 1 compared with cotton upper layer (2.6 vs. 0.8 microg/g Der p 1). Moreover, higher relative humidity (RH) was associated with significant higher concentrations and density of Der p 1. CONCLUSIONS: Two factors were associated with lower levels of Der p 1 found on mattresses, namely: a cotton upper layer of the mattress compared with a layer of synthetic material and lower RH at the time of sampling. As far as we know, the association between type of upper layer and concentration of Der p 1 has not been described before and could lead to the formulation of practical advices in order to reduce HDMA concentrations on mattresses. 相似文献
36.
J B Ubbink W J Serfontein P J Becker L S de Villiers 《The American journal of clinical nutrition》1987,46(1):78-85
Plasma pyridoxal-5'-phosphate and pyridoxal levels increased significantly (p less than 0.05) when single, oral bolus doses of pyridoxine were increased from 10 to 25 and from 25 to 50 mg in nine female volunteers. However, when the dose was increased to 100 mg, plasma pyridoxal-5'-phosphate levels did not differ significantly from those recorded after the 50 mg dose. Within 3 h plasma pyridoxal levels rose with a factor of 3.85 compared with the 50 mg dose but high pyridoxal levels were eliminated from the circulation. Renal clearance of pyridoxal remained a constant, low percentage (less than 2.0%) of each pyridoxine supplement in spite of the observed very high circulating pyridoxal levels. Pyridoxine supplementation is discussed in relation to circulating pyridoxal-5'-phosphate and pyridoxal availability for cellular metabolism. 相似文献
37.
38.
We tested whether hypoglycemia, like hypoxia, would preferentially destroy GABAergic nerve cells in the neocortex. To this end, rat neocortex explants dissected from 6-day-old rat pups and cultured up to a developmental stage approximately comparable to that of the newborn human neocortex, were exposed to hypoglycemia for different periods. Quantitative light microscopic and immunocytochemical evaluation of the cultures demonstrated that hypoglycemia does not preferentially destroy GABAergic but rather non-GABAergic neurons, a finding quite opposite to what was found after hypoxia. Recent biochemical data from other laboratories which seem to support this difference in neuronal vulnerability are discussed. It is concluded that perinatal hypoglycemia may not form such a serious threat with respect to the genesis of epilepsy as does hypoxia. 相似文献
39.
Plasma D-dimer (DD) and thrombin--antithrombin III complex (TAT) were measured with ELISAs in 99 patients investigated by 102 ventilation--perfusion lung scintigraphy because of suspected pulmonary embolism. High-probability lung scan was associated with increased DD (more than 500 ng/ml) and TAT (more than 4.1 ng/ml) levels (sensitivity of 100 and 70%, respectively). The corresponding figures of specificity were 81 and 42%. In the 56 patients with low-probability or indeterminate probability scans, 31 (55%) had DD concentrations of less than 500 ng/ml. These preliminary data suggest that a plasma DD concentration of less than 500 ng/ml might rule out the diagnosis of pulmonary embolism in suspected patients with an inconclusive lung scanning. 相似文献
40.
Marcos Ribeiro Luciene Angelini Priscila Games Robles-Ribeiro Rafael Stelmach Ubiratan de Paula Santos Mario Terra-Filho 《The Journal of asthma》2007,44(5):371-375
Background. The European Community Respiratory Health Survey (ECRHS) questionnaire was planned to answer questions about the distribution of asthma. Our objective was to determine the cultural equivalence of the ECRHS into the Brazilian-Portuguese language. Methods. We translated the ECRHS according to international criteria. Results. Small cultural adaptations were necessary. Among the 80 participating patients, the Cronbach indices were higher (0.98-1.00) and the Kappa indices varied from 0.77 to 1.00. Conclusion. The study suggests that the Brazilian version of the ECRHS is conceptually equivalent to the original and similarly reliable and may be used in international studies involving Portuguese-speaking respiratory patients. 相似文献