全文获取类型
收费全文 | 1375篇 |
免费 | 116篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 87篇 |
妇产科学 | 18篇 |
基础医学 | 178篇 |
口腔科学 | 63篇 |
临床医学 | 113篇 |
内科学 | 345篇 |
皮肤病学 | 21篇 |
神经病学 | 87篇 |
特种医学 | 161篇 |
外科学 | 147篇 |
综合类 | 51篇 |
一般理论 | 1篇 |
预防医学 | 40篇 |
眼科学 | 54篇 |
药学 | 75篇 |
中国医学 | 1篇 |
肿瘤学 | 43篇 |
出版年
2023年 | 6篇 |
2021年 | 19篇 |
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 39篇 |
2017年 | 22篇 |
2016年 | 36篇 |
2015年 | 36篇 |
2014年 | 46篇 |
2013年 | 61篇 |
2012年 | 59篇 |
2011年 | 64篇 |
2010年 | 63篇 |
2009年 | 67篇 |
2008年 | 57篇 |
2007年 | 65篇 |
2006年 | 46篇 |
2005年 | 55篇 |
2004年 | 39篇 |
2003年 | 41篇 |
2002年 | 29篇 |
2001年 | 21篇 |
2000年 | 16篇 |
1999年 | 17篇 |
1998年 | 47篇 |
1997年 | 44篇 |
1996年 | 46篇 |
1995年 | 40篇 |
1994年 | 24篇 |
1993年 | 29篇 |
1992年 | 15篇 |
1991年 | 26篇 |
1990年 | 11篇 |
1989年 | 24篇 |
1988年 | 27篇 |
1987年 | 18篇 |
1986年 | 20篇 |
1985年 | 23篇 |
1984年 | 13篇 |
1983年 | 17篇 |
1982年 | 7篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 15篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1971年 | 6篇 |
排序方式: 共有1500条查询结果,搜索用时 0 毫秒
61.
Effect of tobacco use (by chewing or smoking) on semen quality has been seen. Semen analysis of 119 tobacco chewers and 219 smokers was compared with those of 288 control patients. Some decrease in the ejaculate volume, sperm density, and total count was observed in tobacco users, but it was statistically insignificant. No difference was found in other parameters, like motility and morphology. It is concluded that tobacco use by chewing or smoking is not associated with impaired semen quality in males selected from an idiopathically hypofertile population. 相似文献
62.
An important reason to improve methods for isolating platelet-rich plasma (PRP) is the potential use of autogenous platelet growth factors. In addition to the Curasan PRP kit (Curasan, Kleinostheim, Germany) and the platelet concentrated collection system (PCCSTM) system, two new methods for the preparation of PRP by the surgeon are now available. This study compared the suitability of these new methods for the preparation of PRP. Whole blood was drawn from 54 healthy donors (33 men and 21 women) aged 23-79 years (38.0 +/- 17.7 years). PRP was prepared from each donor's blood using both the Smart PRePTM system (Harvest Technologies Corporation, Munich, Germany) and the Friadent-Schütze method (PRP kit; Friadent-Schütze, Vienna, Austria). The platelet count in donor whole blood was 276 810 +/- 59 440 /microl. Platelet counts differed significantly between the Smart PRP preparation (1227 890 +/- 312 440 platelets/microl) and the Friadent-Schütze PRP preparation (1440 500 +/- 501 700 platelets/microl) (sign test, P < 0.001). The Smart PRePTM system had a significantly higher collection efficiency (63.4 +/- 7.9%) than the Friadent-Schütze kit (49.6 +/- 13.6%) (sign test, P < 0.001). The leukocyte contents in the two platelet concentrates were similar (Smart PRePTM, 19 261 +/- 8082 platelets/microl; Friadent-Schütze, 21 691 +/- 16 430). Transforming growth factor (TGF)-beta1 and platelet-derived growth factor (PDGF)-AB were higher in the Friadent-Schütze PRP (TGF-beta1, 196.8 +/- 109.6 ng/ml; PDGF-AB, 251.6 +/- 115.4 ng/ml) than in the Smart PRePTM (TGF-beta1, 77.2 +/- 54.8 ng/ml; PDGF-AB, 208 +/- 85.2 ng/ml). The sign test indicated significant differences between the two methods in the concentrations of TGF-beta1 (P < 0.001) and PDGF-AB (P < 0.01). Insulin-like growth factor (IGF)-1 levels in the two PRP preparations were similar (Friadent-Schütze PRP, 72.8 +/- 22.3 ng/ml; Smart PRePTM, 91.4 +/- 21.3 ng/ml). The Smart PRePTM system was superior with respect to ease of handling and preparation time. It also had a significantly higher platelet collection efficiency than the Friadent-Schütze PRePTM kit. The Friadent-Schütze PRP kit offers a slight advantage in the resulting PRP platelet concentration. However, this is easily compensated for in the Smart PRePTM system by reducing the volume of the resulting PRP. 相似文献
63.
This study evaluates the influence of genetic polymorphism at GSTM1, GSTM3 and GSTT1 gene loci on oral cancer risk among Indians habituated to the use of, smokeless tobacco, bidi or cigarette. DNA extracted from white blood cells of 297 cancer patients and 450 healthy controls by the proteinase K phenol-chloroform extraction procedure were analyzed by the polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism (RFLP) analyses. Lifetime tobacco exposure was evaluated as a risk factor in relation to the polymorphism at the GST gene loci using logistic regression analysis. There was no significant difference in the distribution of the GSTM3 and GSTT1 genotypes between oral cancer patients and controls. In contrast, a significant 3-fold increase in risk was seen for patients with the GSTM1 null genotype (age adjusted OR = 3.2, 95% CI 2.4-4.3). The impact of the GSTM1 null genotype on oral cancer risk was also analyzed in separate groups of individuals with different tobacco habits. The odds ratio associated with the GSTM1 null genotype was 3.7 (95% CI 2.0-7.1) in tobacco chewers, 3.7 (5% CI 1.3-7.9) in bidi smokers and 5.7 (95% CI 2.0-16.3) in cigarette smokers. Furthermore, increased lifetime exposure to chewing tobacco appeared to be associated with a 2-fold increase in oral cancer risk in GSTM1 null individuals. The results suggest that the GSTM1 null genotype is a risk factor for development of oral cancer among Indian tobacco habitues. 相似文献
64.
Kurt F. Hauser Nazira El-Hage Shreya Buch Avindra Nath William R. Tyor Annadora J. Bruce-Keller Pamela E. Knapp 《Journal of neuroimmune pharmacology》2006,1(1):98-105
Opiate drug abuse exacerbates the pathogenesis of human immunodeficiency virus-1 (HIV-1) in the central nervous system through
direct actions on glia and neurons. Opiate abuse causes widespread disruption of astroglial and microglial function, and significant
increases in astroglial-derived proinflammatory cytokines and chemokines, which likely contributes to neuronal dysfunction,
death, and HIV encephalitis. Neurons are also directly affected by opiate–HIV-1 interactions. HIV-1 and the viral proteins
gp120 and Tat activate multiple caspase-dependent and caspase-independent proapoptotic pathways in neurons involving phosphatidylinositol
3-kinase (PI3 kinase)/Akt, as well as p38, c-Jun N-terminal kinase (JNK) and/or other mitogen-activated protein kinases (MAPKs).
Opiates appear to decrease the threshold for HIV-1-mediated neurotoxicity by sending convergent signals that exacerbate proapoptotic
events induced by viral and cellular toxic products. The synergistic proinflammatory and neurotoxic effects of opiate drugs
on glia and neurons are largely mediated through μ opioid receptors, which are expressed by subpopulations of astroglia, microglia,
and neurons. Opiate abuse intrinsically modifies the host response to HIV-1. Identification of how this occurs is providing
considerable insight toward understanding the mechanisms underlying HIV-1-associated dementia. 相似文献
65.
Decup F Six N Palmier B Buch D Lasfargues JJ Salih E Goldberg M 《Clinical oral investigations》2000,4(2):110-119
Bone sialoprotein (BSP), an osteogenic protein (OP), mixed with a carrier, was implanted in the pulp of rat first upper molars
(OP group). Cavities were prepared with dental burs and pulp perforation was carried out by pressure with the tip of a steel
probe. After 8, 14, and 30 days, the rats were killed and the pulps of the OP group were compared with (1) a sham group (S
group), (2) a group where the carrier was implanted alone (C group), and (3) capping with calcium hydroxide (Ca group). After
8 days, a few inflammatory cells were seen, mostly located at the pulp surface near the perforation. In the Ca group, a dentin
bridge started to form, in contrast to the other groups. After 15 days, globular structures were seen in the pulps of the
S and C groups. A reparative osteodentin bridge isolated the pulp from the cavity in the Ca group. Variable reactions were
seen in the OP group, with some evidence of cell and matrix alignments or plugs of osteodentin in continuity with an inner
layer of reparative dentin. After 30 days, irregular osteodentin formation was observed in the pulps of the S and C groups,
with a tendency for globular structures to merge, but with interglobular spaces filled by pulp remnants. In the Ca group,
osteodentin was observed in the mesial part of the pulp chamber. In the BSP-implanted group, the osteogenic protein stimulated
the formation of a homogeneous dentin-like deposit occupying most of the mesial part of the pulp. Apparently, BSP stimulates
the differentiation of cells which secrete an organized extracellular matrix more efficiently than any other capping material
used so far. Altogether, the results reported here support that bone sialoprotein displays novel bioactive properties and
is capable of stimulating in 1 month’s time the development of a thick reparative dentinal tissue in the pulp, occluding the
perforation and filling the mesial third of the pulp chamber.
Received: 13 October 1999 / Accepted: 6 December 1999 相似文献
66.
M Cole L Parker AW Craft S Bell G Dale AC McGill JA Seviour J Smith 《Archives of disease in childhood》1993,68(3):376-378
The relationship between homovanillic acid (HVA), vanillylmandelic acid (VMA), and creatinine in the urine of 6 month old babies has been studied and reference ranges in the form of centiles constructed for HVA and VMA against creatinine. Over 10,000 urine samples were collected from babies in four health districts in the north of England. HVA and VMA concentration, either independently or when divided by creatinine concentration, were dependent upon the absolute concentration of creatinine in the sample. After adjustment for creatinine significant differences in the mean concentration of HVA were found between sexes. No such differences were found for VMA. HVA and VMA were also found to be age dependent. Centiles were constructed using a procedure which makes no distributional assumptions about the data. The net effect of utilising these centiles was to increase the predictive value of a positive screening test from 20% to 40% without any increase in the false negative rate. 相似文献
67.
68.
69.
FOLIC ACID AND THE HALF-LIFE OF DIPHENYLHYDANTOIN IN MAN 总被引:2,自引:0,他引:2
P. Buch Andreasen J. Mølholm Hansen L. Skovsted K. Siersbæk-Nielsen 《Acta neurologica Scandinavica》1971,47(1):117-119
The half-life of diphenylhydantoin in man was investigated before and after treatment with high doses of folic acid and no significant changes were found. It thus seems unlikely that the possible influence of folic acid on diphenylhydantoin metabolism is mediated by an increased liver metabolism; the possibility, however, remains that the pattern of diphenylhydantoin-metabolites are altered. 相似文献
70.