全文获取类型
收费全文 | 7629篇 |
免费 | 708篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 86篇 |
儿科学 | 316篇 |
妇产科学 | 193篇 |
基础医学 | 863篇 |
口腔科学 | 244篇 |
临床医学 | 841篇 |
内科学 | 1483篇 |
皮肤病学 | 77篇 |
神经病学 | 703篇 |
特种医学 | 450篇 |
外科学 | 845篇 |
综合类 | 203篇 |
一般理论 | 5篇 |
预防医学 | 879篇 |
眼科学 | 68篇 |
药学 | 622篇 |
中国医学 | 4篇 |
肿瘤学 | 490篇 |
出版年
2022年 | 43篇 |
2021年 | 110篇 |
2020年 | 71篇 |
2019年 | 128篇 |
2018年 | 124篇 |
2017年 | 116篇 |
2016年 | 120篇 |
2015年 | 133篇 |
2014年 | 172篇 |
2013年 | 231篇 |
2012年 | 365篇 |
2011年 | 392篇 |
2010年 | 216篇 |
2009年 | 212篇 |
2008年 | 312篇 |
2007年 | 327篇 |
2006年 | 309篇 |
2005年 | 293篇 |
2004年 | 342篇 |
2003年 | 289篇 |
2002年 | 259篇 |
2001年 | 230篇 |
2000年 | 230篇 |
1999年 | 199篇 |
1998年 | 142篇 |
1997年 | 144篇 |
1996年 | 157篇 |
1995年 | 113篇 |
1994年 | 101篇 |
1993年 | 97篇 |
1992年 | 159篇 |
1991年 | 133篇 |
1990年 | 200篇 |
1989年 | 165篇 |
1988年 | 140篇 |
1987年 | 157篇 |
1986年 | 136篇 |
1985年 | 157篇 |
1984年 | 114篇 |
1983年 | 106篇 |
1982年 | 51篇 |
1981年 | 60篇 |
1980年 | 42篇 |
1979年 | 81篇 |
1978年 | 48篇 |
1977年 | 63篇 |
1976年 | 67篇 |
1975年 | 42篇 |
1974年 | 62篇 |
1972年 | 51篇 |
排序方式: 共有8372条查询结果,搜索用时 0 毫秒
71.
72.
73.
Bone marrow and peripheral blood cultures of chronic lymphocytic leukemia patients were mitogenically stimulated with TPA (12-0-tetradecanylphorbol-13-acetate). Clonal cytogenetic abnormalities were detected in frequencies varying from 15% to 100%, in five of the six patients studied. Parallel studies with pokeweek mitogen showed a much lower level of stimulation and only two abnormal clones were detected. The chromosome abnormalities described in this study are similar to those reported in CLL by other authors, particularly with respect to trisomy 12 and deletion 11q. A significant frequency of hypodiploidy and chromosome deletion was also detected in this study, and further studies are underway to determine the significance of these findings. 相似文献
74.
Ford EC Chang J Mueller K Sidhu K Todor D Mageras G Yorke E Ling CC Amols H 《Medical physics》2002,29(12):2913-2924
We investigate the potential of megavoltage (MV) cone-beam CT with an amorphous silicon electronic portal imaging device (EPID) as a tool for patient position verification and tumor/organ motion studies in radiation treatment of lung tumors. We acquire 25 to 200 projection images using a 22 x 29 cm EPID. The acquisition is automatic and requires 7 minutes for 100 projections; it can be synchronized with respiratory gating. From these images, volumetric reconstruction is accomplished with a filtered backprojection in the cone-beam geometry. Several important prereconstruction image corrections, such as detector sag, must be applied. Tests with a contrast phantom indicate that differences in electron density of 2% can be detected with 100 projections, 200 cGy total dose. The contrast-to-noise ratio improves as the number of projections is increased. With 50 projections (100 cGy), high contrast objects are visible, and as few as 25 projections yield images with discernible features. We identify a technique of acquiring projection images with conformal beam apertures, shaped by a multileaf collimator, to reduce the dose to surrounding normal tissue. Tests of this technique on an anthropomorphic phantom demonstrate that a gross tumor volume in the lung can be accurately localized in three dimensions with scans using 88 monitor units. As such, conformal megavoltage cone-beam CT can provide three-dimensional imaging of lung tumors and may be used, for example, in verifying respiratory gated treatments. 相似文献
75.
Strains of Mycobacterium terrae complex which react with DNA probes for M. tuberculosis complex. 总被引:1,自引:3,他引:1 下载免费PDF全文
Following a recent report that two isolates of Mycobacterium terrae complex had given positive reactions with M. tuberculosis complex DNA probes, a joint study was undertaken to determine the extent of these findings in the clinical culture collection holdings of two state health laboratories. A total of 117 M. terrae complex strains (identified by standard biochemical methods) were subjected to M. tuberculosis complex probe testing with the two then-available kits (from Syngene, Inc., and Gen-Probe, Inc.). In addition to the two original isolates first reported, two further M. terrae complex isolates were found to react with the M. tuberculosis complex probes. Two modifications of the Accuprobe (Gen-Probe, Inc.) test method were evaluated. Extension of the selection time to 8 min was the most convenient modification and rendered the M. terrae complex isolates negative when tested with the Accuprobe M. tuberculosis complex probe. However, the effects of increased selection time on the overall sensitivity of the M. tuberculosis complex probe require further study. 相似文献
76.
Regulation of sperm function by reactive oxygen species 总被引:9,自引:0,他引:9
Ford WC 《Human reproduction update》2004,10(5):387-399
Sperm capacitation can be increased by the addition of reactive oxygen species (ROS) and decreased by antioxidants. Broadly consistent results have been achieved with a wide variety of methods and across different species. Exposure to ROS increases protein tyrosine phosphorylation consequent on an increase in cAMP and activation of tyrosine kinase and inhibition of tyrosine phosphatase. The measurement of ROS production by sperm is complicated by contamination of suspensions by leukocytes, laying many studies open to doubt. In human sperm the observation that extracellular NADPH could support superoxide production detected with the chemiluminescent probe lucigenin and had physiological effects similar to hydrogen peroxide led to the suggestion that they contained NADPH oxidase activity to generate ROS to support capacitation. However, the realization that lucigenin can signal superoxide artefactually, combined with failure to detect superoxide production using spin trapping techniques or to detect NADPH oxidase components in mature sperm, and confirmation of old reports that NADPH solution contains substantial amounts of hydrogen peroxide due to autoxidation, have undermined this hypothesis. Although the presence of significant NADPH oxidase activity in mature human sperm now seems less likely, other observations continue to suggest that they can make ROS in some way. There is stronger evidence that animal sperm can make ROS although these may be mainly of mitochondrial origin. 相似文献
77.
Stehbens James A.; Ford Mary E.; Kisker C. Thomas; Clarke William R.; Strayer Faye 《Journal of pediatric psychology》1981,6(1):61-68
Intelligence testing was completed on 38 newly diagnosed pediatriconcology patients and 29 hemophilia patients between 6 and I7years of age. A low Verbal/high Performance intelligence testpattern was displayed by 39% of the oncology patients as comparedto an expected frequency of 12/14% in the hemophilia controls.Increased amounts of prednisone, vincristine, and number ofdays between diagnosis and intelligence testing correlated withthe Verbal-Performance (V-P) discrepancy scores in the oncologypatients. These findings and previous studies suggest the needfor monitoring the intellectual, emotional, linguistic, andneuropsychological status of pediatric oncology patients beginningat the time of diagnosis. 相似文献
78.
Synergy between the genes for butyrylcholinesterase K variant and apolipoprotein E4 in late-onset confirmed Alzheimer's disease 总被引:5,自引:2,他引:5
The allelic frequency of the gene for the K variant of
butyrylcholinesterase (BCHE-K) was 0.17 in 74 subjects with late-onset (age
> 65 years) histopathologically diagnosed Alzheimer's disease (AD),
which was higher than the frequencies in 104 elderly control subjects
(0.09), in 14 early-onset cases of confirmed AD (0.07) and in 29 confirmed
cases of other dementia (0.10). The association of BCHE-K with late-onset
AD was limited to carriers of the epsilon 4 allele of the apolipoprotein E
gene (APOE), among whom the presence of BCHE-K gave an odds ratio of
confirmed late-onset AD of 6.9 (95% C.I. 1.65-29) in subjects > 65 years
and of 12.8 (1.9-86) in subjects > 75 years. In APOE epsilon 4 carriers
over 75 years, only 1/22 controls, compared with 10/24 confirmed late-onset
AD cases, had BCHE-K. We suggest that BCHE-K, or a nearby gene on
chromosome 3, acts in synergy with APOE epsilon 4 as a susceptibility gene
for late-onset AD.
相似文献
79.
80.
Ursula R. Kees Jette Ford Pamela R. Ranford Susanne E. Peroni Jaclyn A. Biegel Annette H. Parmiter Lavinia A. Hallam Michael L. N. Willoughby Dominic Spagnolo 《Genes, chromosomes & cancer》1994,9(2):129-135
We have established two cell lines, PER-452 and PER-453, from an 8-month-old girl with an extensive pineoblastoma. Characterization of these lines revealed that the proto-oncogenes MYC and MYCN were not amplified, but both cell lines showed MYCN expression comparable to a cell line with 200-fold MYCN amplification. Both cell lines contained an i( 17q). These results support the concept that pineoblastomas belong to a larger group of primitive neuroectodermal tumors of the central nervous system. These two cell lines provide a unique opportunity to investigate the molecular genetic mechanisms underlying these neoplasms further. Genes Chrom Cancer 9:129-135 (1994).© 1994 Wiley-Liss, Inc. 相似文献