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   1534篇
  免费   104篇
  国内免费   16篇
耳鼻咽喉   7篇
儿科学   51篇
妇产科学   31篇
基础医学   228篇
口腔科学   26篇
临床医学   152篇
内科学   235篇
皮肤病学   9篇
神经病学   161篇
特种医学   54篇
外科学   212篇
综合类   86篇
预防医学   83篇
眼科学   85篇
药学   101篇
中国医学   23篇
肿瘤学   110篇
  2023年   10篇
  2022年   12篇
  2021年   41篇
  2020年   12篇
  2019年   27篇
  2018年   25篇
  2017年   20篇
  2016年   32篇
  2015年   25篇
  2014年   43篇
  2013年   73篇
  2012年   87篇
  2011年   77篇
  2010年   58篇
  2009年   54篇
  2008年   65篇
  2007年   89篇
  2006年   75篇
  2005年   69篇
  2004年   79篇
  2003年   77篇
  2002年   60篇
  2001年   73篇
  2000年   66篇
  1999年   46篇
  1998年   27篇
  1997年   37篇
  1996年   24篇
  1995年   27篇
  1994年   13篇
  1993年   20篇
  1992年   31篇
  1991年   29篇
  1990年   18篇
  1989年   21篇
  1988年   24篇
  1987年   17篇
  1986年   10篇
  1985年   15篇
  1984年   3篇
  1983年   3篇
  1982年   8篇
  1981年   5篇
  1980年   11篇
  1979年   4篇
  1978年   3篇
  1977年   2篇
  1976年   1篇
  1975年   4篇
  1970年   1篇
排序方式: 共有1654条查询结果,搜索用时 15 毫秒
1.
The clinical and ultrasonographic (US) features of 15 cases of mesenteric or omental cyst are herein described. This series included seven male and eight female patients, whose age ranged from 2–89 years. Correct clinical diagnosis was made in two children only, but preoperative US examination accurately demonstrated the lesion in 11 of 13 patients (85%). These cystic lesions usually had a thin wall, internal septations, and fluid content with sedimentation. Enteric duplication cysts had a relatively thick wall merging with the muscle layer of bowel loop, and multiloculation was noted mainly with cystic lymphangiomas or pseudocysts. The diagnostic and surgical management of these lesions are briefly reviewed and their US appearance is illustrated.  相似文献   
2.
3.
Summary In order to investigate possible effects of smoking and drinking on the metabolism of toluence in occupational settings, 206 toluene-exposed men (mean age: 31.4 years) in shoemaking, painting, or surface-coating workshops together with 246 nonexposed control men (36.8 years) were studied for the time-weighted average intensities of exposure to toluene, hippuric acid concentration in shift-end urine samples, and the two social habits of smoking and drinking. The mean daily consumptions of cigarettes and ethanol were about 20 pieces and 10 g among smokers and drinkers, respectively. The geometric mean toluene concentration among the exposed subjects was about 20 ppm, with a maximum of 521 ppm. Regression analysis after classification of the subjects by smoking and drinking clearly demonstrated that the two social habits, when combined, markedly reduce the hippuric acid level in the urine of workers exposed to was a significant association between smoking and drinking habits, which hindered separate evaluation of the effects of the two habits on toluene metabolism. Comparison of the present results with the findings reported in the literature, however, suggested that the observed effects may be attributable to smoking rather than to drinking habits.  相似文献   
4.
Two triazaspirodienes, having similar phenoxy propyloxy side chain, were identified as potent mammalian dihydrofolate reductase inhibitors; one having a 6,5‐spiro bicyclic ring system (IC50 = 2.3 nm ) and the other a 6,6‐spiro bicyclic system (IC50 = 6.9 nm ). They also showed more than 50% antiproliferative activity against the MCF‐7 breast cancer cells at 20 μm . This study demonstrated the potential lead of the diamino‐triazaspirodienes in anticancer chemotherapeutical agents’ discovery.  相似文献   
5.
Impaired ability to conduct daily activities is a diagnostic criterion for dementia and a determinant of healthcare services utilization and caregiver burden. What predicts decline in instrumental activities of daily living (IADLs) is not well understood. This study examined measures of episodic memory, executive function, and MRI brain volumes in relation to baseline IADLs and as predictors of rate of IADL change. Participants were 124 elderly persons with cognitive function between normal and moderate dementia both with and without significant small vessel cerebrovascular disease. Random effects modeling showed that baseline memory and executive function (EXEC) were associated with baseline IADL scores, but only EXEC was independently associated with rate of change in IADLs. Whereas hippocampal and cortical gray matter volumes were significantly associated with baseline IADL scores, only hippocampal volume was associated with IADL change. In a model including cognitive and neuroimaging predictors, only EXEC independently predicted rate of decline in IADL scores. These findings indicate that greater executive dysfunction at initial assessment is associated with more rapid decline in IADLs. Perhaps executive function is particularly important with respect to maintaining IADLs. Alternatively, executive dysfunction may be a sentinel event indicating widespread cortical involvement and poor prognosis.  相似文献   
6.
We describe a novel alpha-thalassaemia-1 deletion that removes the entire zeta-alpha globin gene cluster. A Chinese couple were referred for counselling after two consecutive pregnancies ended with fetal hydrops. Gene mapping was used to demonstrate that the mother is heterozygous for the South-east Asia alpha-thalassaemia-1 deletion (zeta zeta zeta alpha alpha/zeta zeta--SEA), while the father carries an alpha-thalassaemia-1 deletion of more than 100 kilobases (zeta zeta alpha alpha/----). This newly discovered deletion extends for unknown distances 3' and 5' of the zeta-alpha globin gene cluster and has been designated (--HW).  相似文献   
7.
The metabolic disposition of 14C-labeled 4-chlorodiphenyl ether ([14C]4-CDE) was examined in rats following iv administration of a single dose (850 nmol/kg). [14C]4-CDE decayed rapidly from the blood since no unchanged [14C]4-CDE was detected in the blood beyond 2 hr after [14C]4-CDE administration. The dispositional kinetics of [14C]4-CDE in rats were best described by a two-compartment open pharmacokinetic model. Total radioactivity was excreted slowly from rats; about 41% and 33% of the administered dose were excreted into the urine and feces, respectively, within 1 week after chemical administration. About 5% of the total radioactivity administered to rats was excreted into the bile in 1 hr. The bulk of the radioactivity in the excreta was due to the presence of [14C]4-CDE metabolites. 14C-labeled 4'-hydroxy-4-CDE was the major metabolite and accounted for at least 90% of the radioactivity in the urine. The metabolic conversion of [14C]4-CDE to 14C-labeled 4'-hydroxy-4-CDE was corroborated by in vitro studies with liver microsomes of rats. In addition, [14C]4-CDE was converted by liver microsomes to reactive metabolites which bound irreversibly to microsomal protein. An arene oxide is suggested as the intermediate metabolite in the biotransformation of [14C]4-CDE by rats.  相似文献   
8.
9.
A 12-year-old girl with a history of fast myopia progression underwent advanced orthokeratology (ortho-k) treatment and suffered from recurrent lens binding and central corneal staining. The problem could not be fixed by lens fenestration and refitting with a less aggressive lens (three-zone ortho-k) design. After refitting with a lower target advanced ortho-k lens, these complications were no longer occurring, and the amount of power reduction was greater than expected considering the target designed for the refitted lenses. During the following 15 months of ortho-k lens wear, there was no clinically significant change to her refractive error. The patient and her parents were happy with the outcome, although the refractive error was not totally eliminated and she still needed to wear spectacles for clear vision. Possible etiologies of the complications are discussed.  相似文献   
10.
本文探讨了菊科9种植物和地胆草的4种对口商品药材基因组DNA提取与纯化的原理、方法通过对3种常用植物基因组DNA提取方法(CsCl梯度超速离心法、CTABCsCl梯度超速离心法和CTAB微量提取法)的条件摸索在DNA产率、纯度以及提取纯化过程中影响PCR扩增因子方面进行比较,认为CTAB微量提取法是植物类药材基因组DNA一种比较省时、有效、经济的提取方法  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