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   163488篇
  免费   10391篇
  国内免费   1243篇
耳鼻咽喉   2258篇
儿科学   3114篇
妇产科学   3760篇
基础医学   24444篇
口腔科学   3418篇
临床医学   15464篇
内科学   31241篇
皮肤病学   4452篇
神经病学   12086篇
特种医学   8343篇
外科学   22047篇
综合类   2206篇
现状与发展   5篇
一般理论   81篇
预防医学   9788篇
眼科学   4332篇
药学   13777篇
中国医学   1598篇
肿瘤学   12708篇
  2023年   988篇
  2022年   2740篇
  2021年   4832篇
  2020年   2469篇
  2019年   3588篇
  2018年   4418篇
  2017年   3244篇
  2016年   4204篇
  2015年   5658篇
  2014年   6924篇
  2013年   8439篇
  2012年   12664篇
  2011年   12286篇
  2010年   7287篇
  2009年   6093篇
  2008年   9274篇
  2007年   9159篇
  2006年   8421篇
  2005年   8001篇
  2004年   7136篇
  2003年   6207篇
  2002年   5388篇
  2001年   4406篇
  2000年   4048篇
  1999年   3296篇
  1998年   1391篇
  1997年   1084篇
  1996年   1052篇
  1995年   932篇
  1994年   822篇
  1993年   718篇
  1992年   1611篇
  1991年   1604篇
  1990年   1394篇
  1989年   1300篇
  1988年   1211篇
  1987年   1078篇
  1986年   1059篇
  1985年   919篇
  1984年   698篇
  1983年   589篇
  1982年   430篇
  1981年   414篇
  1980年   387篇
  1979年   542篇
  1978年   433篇
  1977年   423篇
  1976年   380篇
  1974年   366篇
  1972年   336篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
In this new colorimetric assay for Factor XIII in plasma, 5-(biotinamido)pentylamine is used as the amine substrate. Factor XIII, a zymogen, is transformed by thrombin and Ca2+ to active Factor XIIIa, and the incorporation of 5-(biotinamido)pentylamine into N,N-dimethylcasein is used to measure catalytically active Factor XIIIa. The biotinylated enzymatic product is immobilized onto 96-well microtiter plates, complexed with streptavidin-beta-galactosidase, and the absorbance at 405 nm is monitored for production of p-nitrophenol from p-nitrophenyl-beta-D-galactopyranoside. Concentrations of N,N-dimethylcasein, 5-(biotinamido)pentylamine, Ca2+, and thrombin were chosen to allow near-maximum velocity of amine incorporation. A linear relationship was obtained between assay product and plasma volume, from 0.5 to 50 microL of plasma. Results correlated well (r greater than 0.924) with those from the most frequently utilized radiometric filter-paper assay for Factor XIII. The method appears to be ideal for routine diagnostic estimation of Factor XIII in plasma because of its simplicity, its lack of use of radioisotopes, and its potential for assay of large numbers of samples by use of microtiter plates and automated plate readers.  相似文献   
82.
83.
Transforming growth factor-β1 (TGF-β1) is known to be a potent growth inhibitor for many cell types, including most epithelial cells. In skin keratinocytes, TGF-β1 has been shown to inhibit growth and to rapidly reduce c-mycexpression. However, the molecular mechanism of TGF-β1 action on cell growth of cervical carcinoma has not yet been elucidated. We thus assessed the effect of TGF-β1 on the growth of cervical carcinoma cell lines. Two cervical squamous carcinoma cell lines, CUMC-3 and CUMC-6, were incubated with varying concentrations of TGF-β1, and growth inhibition was evaluated with tetrazolium-based colorimetric assay. After culture in TGF-β1 for 24 h, inhibition of growth was detected in a dose-dependent manner at concentrations of 0.1–10 ng/ml in both cell lines. This effect of TGF-β1 on cultured carcinoma cells was associated with apoptotic process including oligonucleosomal ladder DNA and apoptotic body formations. Northern blot analysis revealed c-mycmRNA expression was suppressed by 10 ng/ml of TGF-β1 following 3 h of treatment in both cell lines. Western blot analysis showed that the level of p27Kip1protein was increased after TGF-β1 treatment in both cell lines. These results suggest that the mechanisms by which TGF-β1 inhibits the growth of cervical carcinoma are complex and may include effects on down-regulation of c-mycgene, and overexpression of p27Kip1protein.  相似文献   
84.
The aim of this study was to evaluate if intraoperative vascular ultrasonography is of clinical value in the perioperative management of hepatic transplant patients. Fifteen intraoperative ultrasonographic examinations were performed on 13 patients (five female, eight male) during transplantation. These patients had clinically suspected vascular compromise. Among the 13 patients studied intraoperatively, five were correctly diagnosed as having hemodynamically significant vascular compromise. Of the intraoperative vascular sonographic examinations, the results of 13 were in concordance with the surgical impression as to whether further intervention was necessary or if the procedure could be terminated. Intraoperative sonography demonstrates potential to be of aid to the surgeon in recognition of vascular compromise.  相似文献   
85.
Emphysematous cystitis is characterized by gas collection within the bladder wall and lumen. We report two cases of emphysematous cystitis of the urinary bladder in a 67-year-old and a 63-year-old women. They presented with bladder irritation symptoms such as dysuria, hematuria and frequency. Urinalysis showed pyuria. Cystoscopic examination revealed that bladder mucosa was studded with vesicles varying in size and arranged in clumps. CT scans of the pelvis showed mottled gas bubbles within the bladder. They were treated with antibiotics. Four days after the treatment, the symptoms subsided and plain abdominal film showed no evidence of gas shadows in the pelvic cavity.  相似文献   
86.
We describe a novel human zinc finger cNDA, C2H2-171. This cDNA represents an mRNA which encodes a protein of 484 amino acids and a calculated molecular weight of 54 kD. Four zinc finger-like domains are found in the C-terminal end of the protein. At the N-terminus, C2H2-171 contains a POZ/tramtrack-like domain similar to that found in the tumor associated zinc finger proteins LAZ-3/BCL-6 and PLZ-F, as well as in non-zinc finger proteins. C2H2-171 RNA is preferentially expressed in the brain, and increases during the course of murine development, with maximal expression in the adult. C2H2-171 RNA is differentially expressed in brain regions, with the highest level of expression in the cerebellum. C2H2-171 RNA was expressed at high levels in primary cerebellar granule cell neurons compared to astrocytes. The gene encoding C2H2-171 is highly conserved in vertebrates, and maps to the terminus of human chromosome 1 (1q44-ter). This chromosomal location is associated with a number of cytogenetic aberrations including those involving brain developmental anomalies and tumorigenesis. These data suggest that C2H2-171 may play an important role in vertebrate brain development and function.  相似文献   
87.
Serological grouping of Treponema hyodysenteriae   总被引:2,自引:0,他引:2  
Two Australian isolates of Treponema hyodysenteriae which did not fit within the current serological grouping system for these bacteria were examined by agarose gel double immunodiffusion tests (AGDP). Isolate Vic1 was serologically unique, and we propose that it becomes the type organism for a new sixth serological group of T. hyodysenteriae (Group F). Isolate Q1 was unusual in that lipopolysaccharide (LPS) extracted from it reacted strongly in AGDP with serum raised against the type organism for serogroup D (A1), and also weakly with serum raised against the type organism for serogroup B (WA1). The nature of this cross-reactivity was examined by using cross-absorbed antisera in AGDP, and by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. The pattern of serological cross-reactivity between Q1, A1 and WA1 was complex and was not fully defined, but the isolate Q1 apparently shared low molecular weight 'serogroup' LPS antigens with A1, and shared higher molecular weight LPS antigens with WA1. On this basis Q1 was designated as belonging to serogroup D, although it was recommended that this be qualified as D (B) to indicate the presence of weak cross-reactivity with serogroup B. Such serological cross-reactivity may have significance in relation to the development of immunity to T.hyodysenteriae. Isolate Q1 may be a potentially useful organism for vaccine development because of its ability to induce a good serological response to LPS of treponemes from both serogroups D and B.  相似文献   
88.
Certain features of head-injured patients admitted to the Chang Gung Memorial Hospital in Taiwan during the period 1977 to 1987 were reviewed. The most common causes of injury were motorcycle accidents (56.3%) and street accidents with pedestrian injury (29.47%). The age groups with the greatest incidence of injury were aged 16-20 years, 21-25 years, and 25-30 years. The pedestrian group involving the highest incidence of injury was less than 10 years of age. Overall mortality was 17.26%. The injured pedestrian group had the highest mortality (19.1%). Initial clinical assessment was recorded using the Glasgow Coma Scale. Head-injured patients with a GCS less than 8 had a mortality in the injured pedestrian group of 46%, whereas the mortality rate in the motorcycle accident group was 41%. Additional features studied were time of occurrence of injury and pattern of injury. Information gathered from this study would suggest the need to establish a Head Injury Prevention Program in Taiwan. This of course implies major cooperation among the providers of health care delivery, the medical profession, legislators, and the government at all levels.  相似文献   
89.
90.
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