首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3643篇
  免费   248篇
  国内免费   11篇
耳鼻咽喉   36篇
儿科学   198篇
妇产科学   67篇
基础医学   495篇
口腔科学   55篇
临床医学   242篇
内科学   701篇
皮肤病学   115篇
神经病学   343篇
特种医学   67篇
外科学   572篇
综合类   82篇
预防医学   262篇
眼科学   66篇
药学   360篇
  2篇
中国医学   18篇
肿瘤学   221篇
  2023年   32篇
  2022年   86篇
  2021年   135篇
  2020年   64篇
  2019年   96篇
  2018年   114篇
  2017年   87篇
  2016年   104篇
  2015年   87篇
  2014年   108篇
  2013年   165篇
  2012年   211篇
  2011年   209篇
  2010年   125篇
  2009年   95篇
  2008年   153篇
  2007年   178篇
  2006年   144篇
  2005年   151篇
  2004年   98篇
  2003年   121篇
  2002年   105篇
  2001年   68篇
  2000年   86篇
  1999年   83篇
  1998年   31篇
  1996年   23篇
  1995年   19篇
  1993年   20篇
  1992年   59篇
  1991年   53篇
  1990年   25篇
  1989年   40篇
  1988年   42篇
  1987年   41篇
  1986年   34篇
  1985年   32篇
  1984年   24篇
  1983年   32篇
  1982年   28篇
  1979年   20篇
  1976年   25篇
  1975年   28篇
  1974年   27篇
  1973年   23篇
  1972年   18篇
  1971年   27篇
  1970年   30篇
  1969年   25篇
  1968年   18篇
排序方式: 共有3902条查询结果,搜索用时 0 毫秒
11.
12.
13.
Incidence of the Carnation etched ring virus (CERV), the only DNA virus reported to date on carnation, was investigated by a bioassay using a partially purified virus as inoculum and then by a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Out of 61 carnation cultivars analyzed 41 (67%) were found positive. The virus positivity was verified by polymerase chain reaction (PCR) and nucleotide sequencing. The amplified 1349 bp fragment was by about 98% and 96% identical with respect to coat protein (CP) and enzymatic polyprotein genes, respectively, as compared to the sequences available in the database. In terms of amino acid sequence similarity, the homology values were 99% and 97%, respectively. Comparison with other caulimoviruses revealed that CERV is most closely related to the Cauliflower mosaic virus (CaMV). High genetic stability of CERV may be attributed to the fact that it has evolved from the same initial sequence in an original host. Because of global market of cut flowers and vegetative propagation it has been dispersed around the world.  相似文献   
14.
Sexual dimorphism in foot length proportionate to stature   总被引:1,自引:0,他引:1  
BACKGROUND: The preponderance of existing results suggests that, relative to stature, women have smaller feet than men. However, several investigations indicate that the relationship between foot length and stature may be curvilinear, a pattern that, due to the dimorphic nature of stature, would mask the true direction of pedal sexual dimorphism in published results. AIM: The study aimed to determine whether proportionate foot length is sexually dimorphic and, if so, the nature of that dimorphism. MATERIALS AND METHODS: Surveying genetically disparate populations (USA, Turkey, and Native North and Central American), we examined data from three previous anthropometric studies (Davis 1990, Parham et al. 1992, Ozaslan et al. 2003) and foot tracings from the Steggerda Collection at the US National Museum of Health and Medicine. Analyses explored sex differences in the ratio between foot length and stature, and tested for nonlinearity. RESULTS: Although varying in degree across populations, proportionate to stature, female foot length is consistently smaller than male foot length. CONCLUSION: Given the biomechanical challenges posed by pregnancy, smaller female proportionate foot length is somewhat surprising, as foot length affects dorsoventral stability. It is possible that the observed pattern reflects intersexual selection for small female foot size, a cue of youth and nulliparity.  相似文献   
15.
Six Food and Drug Administration (FDA)-licensed human immunodeficiency virus type 1 (HIV-1) and HIV-1/2 immunoassays, including five enzyme immunoassays and one rapid test, were challenged with up to 250 serum samples collected from various global sites. The serum samples were from individuals known to be infected with variants of HIV-1 including group M subtypes A, B, B', C, D, E, F, and G and group O. All immunoassays detected the vast majority of samples tested. Three samples produced low signal over cutoff values in one or more tests: a clade B sample, an untypeable sample with a low antibody titer, and a group O sample. It is concluded that HIV-1 immunoassays used in the United States are capable of detecting most HIV-1 group M variants.  相似文献   
16.
Yersinia enterocolitica is an enteric bacterium and infections by this organism are mostly foodborne. It has been implicated to cause enterocolitis, terminal ilitis. diarrhoea, mesenteric lymphadenitis and arthritis in man. Due to paucity of information regarding histopathological and specially ultrastructural alterations in tissues affected, this study was planned with mice as the experimental model. Nine pathogenic Y.enterocoliticaisolates were used to infect 80 albino mice by oral and intraperitoneal route. Pathological alterations were studied by light and electron microscopy. Histopathological examination of intestines showed severe edema, purulent enteritis, goblet cell hyperplasia infiltration of mononuclear cells, thickening of mucosa and necrosis of the tips of villi. Liver showed congestion, hepatocellular degeneration and necrosis, atrophy of hepatocytes and microabcesses. The lungs revealed congestion, edema, haemorrhage and purulent ronchopneumonia, while kidneys showed mild necrotic changes and bacterial emboli in glomeruli. Ultrastructural changes were indicative of mitochondrial degeneration and their loss in kidneys, membranous degeneration with formation of myelin figures in lungs and disorganization, disruption and bleb formation of microvilli in intestines. Y.enterocolitica caused significant histopathological and ultrastructural alterations in experimentally infected mice. Variation in pathogenicity of different strains of Y.enterocolitica was also observed.  相似文献   
17.
The human epidermal growth factor receptor (HER) family of receptor tyrosine kinase has been extensively studied in breast cancer; however, systematic studies of EGFR gene amplification and protein overexpression in breast carcinoma are lacking. We studied EGFR gene amplification by chromogenic in situ hybridization (CISH) and protein expression by immunohistochemistry in 175 breast carcinomas, using tissue microarrays. Tumors with >5 EGFR gene copies per nucleus were interpreted as positive for gene amplification. Protein overexpression was scored according to standardized criteria originally developed for HER-2. EGFR mRNA levels, as measured by Affymetrix U133 Gene Chip microarray hybridization, were available in 63 of these tumors. HER-2 gene amplification by fluorescence in situ hybridization (FISH) and protein overexpression by immunohistochemistry were also studied. EGFR gene amplification (copy number range: 7-18; median: 12) was detected in 11/175 (6%) tumors, and protein overexpression was found in 13/175 (7%) tumors. Of the 11 tumors, 10 (91%) with gene amplification also showed EGFR protein overexpression (2+ or 3+ by immunohistochemistry). The EGFR mRNA level, based on Affymetrix U133 chip hybridization data, was increased relative to other breast cancer samples in three of the five tumors showing gene amplification. Exons 19 and 21 of EGFR, the sites of hotspot mutations in lung adenocarcinomas, were screened in the 11 EGFR-amplified tumors but no mutations were found. Three of these 11 tumors also showed HER-2 overexpression and gene amplification. Approximately 6% of breast carcinomas show EGFR amplification with EGFR protein overexpression and may be candidates for trials of EGFR-targeted antibodies or small inhibitory molecules.  相似文献   
18.
Background/Purpose of the StudyC-arm-guided biopsy is a safe and effective technique for evaluating TB spine and is useful in planning therapy. The purpose of this study was to find a correlation between clinically and radiologically suspected TB spine and C-arm image-guided biopsy-proven cases and to study the complications encountered.MethodsAfter evaluating the clinical, laboratory, X-ray and MRI findings, 92 patients with provisionally diagnosed tubercular spine were subjected to C-arm image-guided biopsy.ResultsAmong our 92 cases, histopathology was positive in 55 cases (59.78%). Out of these 55 histologically positive cases, CBNAAT was positive in 42 cases and negative in the rest 13 cases. Overall, among the 92 cases, CBNAAT was positive in 51(55.43%) of cases, and out of these, histopathology turned out to be positive in 42 of cases. Out of 41 cases with negative CBNAAT, histopathology was suggestive of tuberculosis in 13. The strength of agreement between CBNAAT and histopathology was statistically significant (p < 0.0001; kappa = 0.511). No complication such as bleeding, nerve/cord injury, infection, injury to aorta or pneumothorax was encountered during and after the C-arm biopsy in any case.ConclusionC-arm image-guided biopsy is reasonably accurate and should be used as a tool for diagnosis of TB spine. We recommend histopathological examination as a key component for the diagnosis of TB spine, as it is precise and consumes relatively shorter time. CBNAAT is more rapid but is not a substitute for histopathology for spine TB diagnosis.  相似文献   
19.
Bulletin of Environmental Contamination and Toxicology - An experiment was conducted to study the effects of co-composted products of municipal solid waste (MSW) and pigeon pea biochar (PPB) on...  相似文献   
20.
Histamine1, receptor antagonists are being prescribed frequently in ENT practice. However, previously we found a fall of blood glucose with terfenadine and astemizole. Present study (double blind, randomized, single dummy and placebo controlled) evaluated the chronic effect (7 days of use) of clemastine, Loratidine and Certrizine on blood glucose level in patient of allergic rhinitis. Cetrizine produced a significant increase in post-prandial blood glucose (P<0.02) and a little rise in fasting blood glucose. Clamastine caused a little fall of fasting and a little rite of post-prandial blood glucose levels. The exact mechanisms involved in the effect of these drugs on blood glucose remain to be elucidated.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号