全文获取类型
收费全文 | 2436835篇 |
免费 | 181569篇 |
国内免费 | 5402篇 |
专业分类
耳鼻咽喉 | 32185篇 |
儿科学 | 81469篇 |
妇产科学 | 67305篇 |
基础医学 | 348686篇 |
口腔科学 | 70903篇 |
临床医学 | 220433篇 |
内科学 | 473379篇 |
皮肤病学 | 55338篇 |
神经病学 | 191012篇 |
特种医学 | 92486篇 |
外国民族医学 | 526篇 |
外科学 | 368122篇 |
综合类 | 56908篇 |
现状与发展 | 4篇 |
一般理论 | 872篇 |
预防医学 | 185143篇 |
眼科学 | 57754篇 |
药学 | 177613篇 |
9篇 | |
中国医学 | 5811篇 |
肿瘤学 | 137848篇 |
出版年
2019年 | 19031篇 |
2018年 | 27599篇 |
2017年 | 21028篇 |
2016年 | 23297篇 |
2015年 | 26474篇 |
2014年 | 36640篇 |
2013年 | 54395篇 |
2012年 | 74077篇 |
2011年 | 78378篇 |
2010年 | 46572篇 |
2009年 | 43573篇 |
2008年 | 72951篇 |
2007年 | 77706篇 |
2006年 | 78301篇 |
2005年 | 75056篇 |
2004年 | 72760篇 |
2003年 | 69268篇 |
2002年 | 66902篇 |
2001年 | 122270篇 |
2000年 | 125196篇 |
1999年 | 104182篇 |
1998年 | 28022篇 |
1997年 | 24772篇 |
1996年 | 24780篇 |
1995年 | 23774篇 |
1994年 | 21888篇 |
1993年 | 20323篇 |
1992年 | 80206篇 |
1991年 | 77747篇 |
1990年 | 75338篇 |
1989年 | 72590篇 |
1988年 | 65959篇 |
1987年 | 65051篇 |
1986年 | 61173篇 |
1985年 | 58359篇 |
1984年 | 43131篇 |
1983年 | 36571篇 |
1982年 | 21099篇 |
1981年 | 18900篇 |
1979年 | 38637篇 |
1978年 | 27191篇 |
1977年 | 23156篇 |
1976年 | 21631篇 |
1975年 | 22746篇 |
1974年 | 27578篇 |
1973年 | 26537篇 |
1972年 | 24556篇 |
1971年 | 22717篇 |
1970年 | 21145篇 |
1969年 | 19782篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Multilocus DNA fingerprinting reveals high rate of heritable genetic mutation in herring gulls nesting in an industrialized urban site. 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
C L Yauk J S Quinn 《Proceedings of the National Academy of Sciences of the United States of America》1996,93(22):12137-12141
Genotoxins, such as polycyclic aromatic compounds, are ubiquitous in urban and industrial environments. Our understanding of the role that these chemicals play in generating DNA sequence mutations is predominantly derived from laboratory studies with specific genotoxins or extracts of contaminants from environmental media. Most assays are not indicative of the germinal effects of exposure in situ to complex mixtures of common environmental mutagens. Using multilocus DNA fingerprinting, we found the mutation rate in herring gulls inhabiting a heavily industrialized urban harbor (Hamilton Harbour, Ontario) to be more than twice as high as three rural sites: Kent Island, Bay of Fundy; Chantry Island, Lake Huron; and Presqu'ile Provincial Park in Lake Ontario. Overall we found a mutation rate of 0.017 +/- 0.004 per offspring band in Hamilton, 0.006 +/- 0.002 at Kent Island, 0.002 +/- 0.002 from Chantry Island, and 0.004 +/- 0.002 from Presqu'ile Provincial Park. The mutation rate from the rural sites (pooled) was significantly lower than the rate observed in Hamilton Harbour (Fisher's exact test, two-tailed; P = 0.0006). These minisatellite DNA mutations may be important biomarkers for heritable genetic changes resulting from in situ exposure to environmental genotoxins in a free-living vertebrate species. 相似文献
992.
New latex reagent using monoclonal antibodies to capsular polysaccharide for reliable identification of both oxacillin-susceptible and oxacillin-resistant Staphylococcus aureus. 总被引:5,自引:5,他引:0
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J M Fournier A Bouvet D Mathieu F Nato A Boutonnier R Gerbal P Brunengo C Saulnier N Sagot B Slizewicz et al. 《Journal of clinical microbiology》1993,31(5):1342-1344
A new latex agglutination test (Pastorex Staph-Plus, Sanofi Diagnostics Pasteur), consisting of a mixture of latex particles coated with fibrinogen and immunoglobulin G for the detection of clumping factor and protein A and latex particles sensitized with monoclonal antibodies directed to Staphylococcus aureus serotype 5 and 8 capsular polysaccharides, was compared with three commercially available rapid agglutination methods for the identification of 220 isolates of S. aureus (61 oxacillin resistant) and 128 isolates of coagulase-negative staphylococci. The sensitivity for identification of S. aureus was high with the Pastorex Staph-Plus test (98.6%) compared with those of the other tests, which ranged from 91.8 to 84.5%. Test sensitivities for the identification of oxacillin-resistant S. aureus were as follows: Pastorex Staph-Plus, 95.1%; Pastorex Staph, 73.8%; Staphyslide, 72.1%; and StaphAurex, 49.2%. 相似文献
993.
Anti-CD40 antibody stimulates the VLA-4-dependent adhesion of normal and LFA-1-deficient B cells to endothelium. 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Immunology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We have demonstrated that anti-CD40 antibody stimulates the heterotypic adhesion of B cells to endothelial cells. This has been shown by using normal B lymphocytes and B-cell lines in a quantitative adhesion assay. When B cells, B-cell lines and Epstein-Barr virus (EBV)-transformed B cells from a patient with leucocyte adhesion deficiency (LAD) were stimulated with anti-CD40 antibody, they were found to adhere to both untreated and interleukin-1 (IL-1)-stimulated human umbilical vein endothelial cells (HUVEC), and to the lung carcinoma line A549. To identify the adhesion receptors responsible for this anti-CD40-induced adhesion, cells were pretreated with blocking antibodies prior to assay. Our results indicate that anti-CD40-stimulated adhesion of tonsillar B cells, B-cell lines RPMI-8866, JY, and an EBV-transformed LAD-cell line were predominantly dependent on the very late antigen-4 (VLA-4)-vascular cell adhesion molecule (VCAM) interaction. Anti-CD40-induced adhesion appears to be dependent on the activation of protein tyrosine kinase and protein kinase C and on the presence of divalent cations. 相似文献
994.
Xu Dai-gen He Han-zhen Zhang Guo-gao B. Gansewendt H. Peter H. M. Bolt 《华中科技大学学报(医学英德文版)》1993,13(2):100-104
Monohalogenated methanes (methyl chloride, methyl bromide and methyl iodide) are mutagenic and carcinogenic. The possible mechanism of these effects, DNA methylation, was studied. DNA adducts from orgnas of F344 rats exposed to these chemicals were separated and identified with high performance liquid chromatography (HPLC) and gaschro-matography/massspectrometry (GC/ MS). DNA adducts, 7-methylguanine (7-MeG) and O6-Methylguanine(08-MeG), incorporation of14C into de novo synthesis of nucleobases could be observed in enzymatic DNA hydrolysates by HPLC and determination of the radioactivity in the fractions. The formation of DNA add,ue,ts in the studied organs was only quantitatively different. The formation of O6-MeG was further pioved by analysing the acidic hydrolysates using HPLC with non-radioactive O6MeG as internal standard. 7-MeG and 3-MeA were identified with GC/MS analysis. 相似文献
995.
P. A. Milligan P. E. McGill C. W. Howden A. W. Kelman B. Whiting 《European journal of clinical pharmacology》1993,45(6):507-512
Summary A randomised crossover study was performed in subjects with rheumatoid arthritis (or other arthropathies) to investigate if any alteration in the steady pharmacokinetics of the NSAID piroxicam (a drug which is extensively metabolised via cytochrome P450) or its major metabolites occurred as a result of coadministering either cimetidine or nizatidine.Twelve females and 2 males with mean age, weight, and albumin concentrations of 58 years, 61 kg, and 40 g·L–1 respectively, completed the study. Comparisons were made between the following parameters: plasma piroxicam AUCs [AUC0-24(P)], plasma 5-hydroxypiroxicam AUCs [AUC0-24(5-OHP)], the ratio of these i.e. AUC0-24(5-OHP):AUC0-24(p), the % piroxicam daily dose excreted in urine as 5-hydroxypiroxicam (before and after glucuronidase incubation); and the mean of the steady state trough piroxicam, and 5-hydroxypiroxicam concentrations (obtained during each study phase in addition to the wash-out period).A statistically significant difference as a result of initiating either cimetidine or nizatidine was obtained only for the ratio AUC0-23(5-OHP):AUC0-24(P). This was indicative of a weak potential to inhibit piroxicam hydroxylation.No clinically significant alteration in the steady state pharmacokinetics of piroxicam occurred in these subjects as a result of cimetidine or nizatidine coadministration. Consequently it is unlikely that any adverse events would arise from these combinations. 相似文献
996.
997.
998.
Graham M. O'Hanlon Margaret B. Lowrie 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1995,103(2):243-250
Disruption of neuromuscular contact by nerve-crush during the early postnatal period causes increased activity and abnormal reflex responses in affected motoneurons, but such changes are not found after nerve-crush in adult animals. We found previously that neonatally lesioned cells develop an abnormal dendritic field, which may explain the functional changes. Here we have studied the dendritic morphology of the same motoneuron pool after nerve-crush at maturity in order to correlate the observed alterations in morphology with physiological findings. One to two months after sciatic nerve-crush in adult animals, motoneurons supplying the extensor hallucis longus muscles of the rat were retrogradely labelled with cholera toxin subunit-B conjugated to horseradish peroxidase. The dendritic tree of labelled cells was then analysed. Following adult nerve-crush, the dendritic tree of the motoneurons was smaller but did not display the localised increase in dendritic density seen after neonatal nerve-crush. These findings support the view that such specific morphological changes contribute to the physiological abnormalities seen only after neonatal nerve injury. 相似文献
999.
1000.