全文获取类型
收费全文 | 8766篇 |
免费 | 860篇 |
国内免费 | 62篇 |
专业分类
耳鼻咽喉 | 55篇 |
儿科学 | 176篇 |
妇产科学 | 162篇 |
基础医学 | 1235篇 |
口腔科学 | 211篇 |
临床医学 | 1035篇 |
内科学 | 1891篇 |
皮肤病学 | 80篇 |
神经病学 | 966篇 |
特种医学 | 596篇 |
外科学 | 997篇 |
综合类 | 200篇 |
一般理论 | 2篇 |
预防医学 | 844篇 |
眼科学 | 272篇 |
药学 | 526篇 |
中国医学 | 9篇 |
肿瘤学 | 431篇 |
出版年
2021年 | 136篇 |
2020年 | 81篇 |
2019年 | 135篇 |
2018年 | 143篇 |
2017年 | 111篇 |
2016年 | 105篇 |
2015年 | 133篇 |
2014年 | 189篇 |
2013年 | 295篇 |
2012年 | 444篇 |
2011年 | 396篇 |
2010年 | 234篇 |
2009年 | 217篇 |
2008年 | 361篇 |
2007年 | 389篇 |
2006年 | 361篇 |
2005年 | 328篇 |
2004年 | 336篇 |
2003年 | 267篇 |
2002年 | 317篇 |
2001年 | 260篇 |
2000年 | 209篇 |
1999年 | 208篇 |
1998年 | 143篇 |
1997年 | 116篇 |
1996年 | 156篇 |
1995年 | 125篇 |
1994年 | 113篇 |
1993年 | 112篇 |
1992年 | 221篇 |
1991年 | 192篇 |
1990年 | 196篇 |
1989年 | 219篇 |
1988年 | 208篇 |
1987年 | 193篇 |
1986年 | 170篇 |
1985年 | 190篇 |
1984年 | 148篇 |
1983年 | 128篇 |
1982年 | 84篇 |
1981年 | 83篇 |
1980年 | 84篇 |
1979年 | 110篇 |
1978年 | 94篇 |
1977年 | 95篇 |
1975年 | 79篇 |
1974年 | 85篇 |
1973年 | 78篇 |
1972年 | 70篇 |
1970年 | 70篇 |
排序方式: 共有9688条查询结果,搜索用时 15 毫秒
91.
Detection of either rapidly cytolytic macrophages or NK cells in "activated" peritoneal exudates depends on the method of analysis and the target cell type 总被引:1,自引:1,他引:1 下载免费PDF全文
The nature of the cytotoxic cells present in the peritoneal cavity of rats treated with Bacille Calmette-Guérin (BCG) or Corynebacterium parvum was investigated using a 6 hr chromium release assay and a quantitative method of analysis based on consideration of target-cell killing as an enzyme-substrate reaction. When the results of cell-fractionation experiments were evaluated in terms of recovery of total lytic units and when appropriate target cells (such as sarcoma Mc7) were used, the simultaneous presence of both cytotoxic macrophages and NK cells in peritoneal exudates could be readily demonstrated. With certain other target cells different results were obtained. Thus, with normal thymocytes, normal hepatocytes, or myeloma P3NSI as targets, NK cells were preferentially detected, whereas with leukaemias L5178Y, P815, and EL4 as targets, cytotoxic macrophages were preferentially detected. These findings resolve the previously conflicting reports concerning the nature of cytotoxic cells in activated peritoneal exudates. 相似文献
92.
Glycogen synthesis and metabolism of lactic acid after exercise 总被引:1,自引:0,他引:1
93.
94.
Is urine leukocyte esterase test a useful screening method to predict Chlamydia trachomatis infection in women? 总被引:1,自引:0,他引:1 下载免费PDF全文
J M Chow J Moncada D Brooks G Bolan H Shaw J Schachter 《Journal of clinical microbiology》1996,34(3):534-536
We evaluated the use of the leukocyte esterase test (LET) on first-catch urine specimens from women as a screening test to predict infection with Chlamydia trachomatis. For diagnosis, we used Abbott's ligase chain reaction (LCR) on urine specimens and isolation by tissue culture (TC) on cervical brushes. Of 4,053 women attending sexually transmitted disease and family planning clinics, 4.3% (n = 174) were positive by TC and 5.9% (n = 239) were positive by LCR. When LET was compared to TC, the sensitivity, specificity, positive predictive value, and negative predictive value were 54.0, 67.0, 6.8, and 97.0%, respectively. The corresponding performance of LET versus LCR was 53.1, 67.3, 10.1, and 95.8%. Almost half of the laboratory-confirmed chlamydial infections were negative by LET. The low specificity probably reflects multiple causes of pyuria in women and results in a low positive predictive value. LET is neither sensitive nor specific as a predictor of chlamydial infection and cannot be recommended for use as a screening test for C. trachomatis with first-catch urine samples from females from low- or moderate-prevalence populations. 相似文献
95.
Matte U Yogalingam G Brooks D Leistner S Schwartz I Lima L Norato DY Brum JM Beesley C Winchester B Giugliani R Hopwood JJ 《Molecular genetics and metabolism》2003,78(1):37-43
In this study we have investigated a group of 29 Brazilian patients, who had been diagnosed with the lysosomal storage disorder, Mucopolysaccharidosis type I (MPS-I). MPS I is caused by a deficiency in the lysosomal hydrolase, alpha-L-iduronidase. Ninety percent of the MPS I patients in this study were genotyped and revealed 10 recurrent and thirteen novel IDUA gene mutations. Eight of these new mutations and three common mutations W402X, P533R, and R383H were individually expressed in CHO-K1 cells and analyzed for alpha-L-iduronidase protein and enzyme activity. A correlation was observed between the MPS I patient clinical phenotype and the associated mutant alpha-L-iduronidase protein/enzyme activity expressed in CHO-K1 cells. This was the first time that Brazilian MPS I patients had been thoroughly analyzed and highlighted the difficulties of mutation screening and clinical phenotype assessment in populations with high numbers of unique mutations. 相似文献
96.
Eshleman SH Guay LA Wang J Mwatha A Brown ER Musoke P Mmiro F Jackson JB 《Journal of acquired immune deficiency syndromes (1999)》2005,40(1):24-29
BACKGROUND: The HIVNET 012 trial in Uganda demonstrated that single-dose nevirapine (NVP) can prevent HIV-1 mother-to-child transmission. NVP resistance (NVPR) mutations were detected in 25% of women 6 to 8 weeks after NVP, with a higher rate of NVPR in women with subtype D than A. This study examined emergence and fading of specific NVPR mutations in women with these subtypes. METHODS: Plasma HIV-1 was analyzed with the ViroSeq genotyping system (Celera Diagnostics, Alameda, CA). Genotypes were obtained from paired samples collected 7 days and 6 to 8 weeks after NVP from 140 women, 83 with subtype A and 57 with subtype D. RESULTS: The rate of NVPR was similar in women with subtype A vs. D at 7 days but was higher in subtype D than A at 6 to 8 weeks. The higher rate of NVPR in subtype D was explained by at least 2 factors: Y181C faded from detection at a greater rate in women with subtype A (odds ratio = 3.06; 95% CI, 1.04, 8.90) and K103N accumulated at a greater rate in women with subtype D (odds ratio = 1.74; 95% CI, 0.62, 4.87). CONCLUSIONS: HIV-1 subtype influences selection and fading of HIV-1 variants with specific drug resistance mutations after antiretroviral drug exposure. 相似文献
97.
Waters DL Brooks WM Qualls CR Baumgartner RN 《Mechanisms of ageing and development》2003,124(3):301-309
BACKGROUND: The decline in muscle mass (sarcopenia) with aging may be related to a decline in mitochondrial function. However, investigators have yet to reach a consensus as to whether a decline in mitochondrial function can be attenuated by physical activity has yet to reach a consensus. METHODS: Using dynamic 31PMRS to measure mitochondrial function, we measured baseline Phosphocreatine (PCr), inorganic phosphate (Pi), phosphodiester (PDE), [ADP], pH and recovery times (t(1/2)) for PCr and [ADP] following exercise, in 45 older (73+/-4 years, SD), and 20 younger subjects (25+/-4 years, SD) who were matched for body mass across high and low activity levels and within age and sex groupings. RESULTS: Baseline PCr, and Pi, were lower, and PDE higher in the older subjects compared to younger subjects (all P<0.01). The t(1/2)(ADP) was longer in older subjects (P<0.001) controlling for age and sex in the low activity group (P=0.02). In the older low activity groups, t(1/2)(PCr) was longer than high activity groups. Higher PDE levels were positively correlated with longer t(1/2)(PCr) in the older low activity females (both P<0.05). CONCLUSIONS: Our data suggests that mitochondrial function declines with age in healthy, exercising elderly adults and that the decline appears to be influenced by the level of physical activity. 相似文献
98.
K Matsui L Share D P Brooks J T Crofton R W Rockhold 《The American journal of physiology》1983,245(6):E611-E615
It is generally considered that the liver is primarily responsible for the extraction of vasopressin from the circulating blood by the splanchnic viscera. To investigate this matter further, measurements were made in the anesthetized dog of the concentrations of vasopressin in arterial, portal venous, and hepatic venous plasma, and of total splanchnic plasma flow and hepatic arterial plasma flow. The total splanchnic vasopressin extraction ratio was 12.9 +/- 1.0%. However, the concentration of vasopressin in portal venous plasma was consistently lower than in arterial plasma, and there was a substantial prehepatic extraction of vasopressin, averaging 10.5 +/- 0.8%. A quantitative evaluation of the contribution of the "prehepatic" viscera, i.e., viscera with venous drainage into the portal vein, is provided by the relevant clearances of vasopressin. The prehepatic and total splanchnic vasopressin clearances were 1.58 +/- 0.20 and 3.04 +/- 0.31 ml X min-1 X kg-1, respectively. Thus, the splanchnic viscera other than the liver were responsible for approximately half of the splanchnic clearance of vasopressin; the remainder could be attributed to the liver. Immunoreactive vasopressin was not found in the bile. In splenectomized dogs, in which venous blood was collected from the superior mesenteric vein, the vasopressin extraction ratio was 14.6 +/- 2.3%, suggesting that the prehepatic clearance of vasopressin occurs largely in the mesenteric bed. A more specific localization of the prehepatic clearance sites has not as yet been made. 相似文献
99.
Development, characterization, and anti-microbial efficacy of hydroxyapatite-chlorhexidine coatings produced by surface-induced mineralization 总被引:4,自引:0,他引:4
Campbell AA Song L Li XS Nelson BJ Bottoni C Brooks DE DeJong ES 《Journal of biomedical materials research》2000,53(4):400-407
The surface-induced mineralization (SIM) technique was used to produce hydroxyapatite (HAP) coatings on external fixation pins with the antimicrobial agent, chlorhexidine, incorporated within the coating. The SIM process involved surface modification of the substrate with organic functional groups followed by immersion in aqueous supersaturated calcium phosphate solutions. X-ray diffraction spectra confirmed that hydroxyapatite coatings were formed. Chlorhexidine was incorporated into the coating by placing the substrate into various chlorhexidine solutions in between mineralization cycles. Total uptake was measured by dissolution of the coating into a 0.1 M nitric acid solution and measuring the chlorhexidine concentration using UV spectroscopy at 251 nm. Release rates were measured by submersion of coated substrates into saline solutions and measuring chlorhexidine UV absorbency at 231 nm as a function of time. Results show an initial rapid release followed by a period of slower sustained release. The anti-microbial efficacy of the HAP-chlorhexidine coatings was evaluated in vitro using a Staphylococcus aureus cell culture. Initial results show a large "inhibition zone" formed around the chlorhexidine/HAP coating vs. coatings with HAP only. This preliminary work clearly demonstrates that SIM HAP coatings have great potential to locally deliver antimicrobial agents such as chlorhexidine at implantation sites, which may greatly reduce the incidence of pin tract infection that occurs in external fixation. 相似文献
100.