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   1319篇
  免费   75篇
  国内免费   8篇
耳鼻咽喉   35篇
儿科学   18篇
妇产科学   37篇
基础医学   122篇
口腔科学   17篇
临床医学   107篇
内科学   356篇
皮肤病学   55篇
神经病学   75篇
特种医学   195篇
外科学   96篇
综合类   7篇
预防医学   57篇
眼科学   3篇
药学   74篇
中国医学   3篇
肿瘤学   145篇
  2023年   7篇
  2022年   6篇
  2021年   23篇
  2020年   19篇
  2019年   12篇
  2018年   31篇
  2017年   17篇
  2016年   24篇
  2015年   31篇
  2014年   32篇
  2013年   45篇
  2012年   48篇
  2011年   42篇
  2010年   25篇
  2009年   36篇
  2008年   45篇
  2007年   55篇
  2006年   55篇
  2005年   50篇
  2004年   50篇
  2003年   44篇
  2002年   39篇
  2001年   33篇
  2000年   29篇
  1999年   38篇
  1998年   25篇
  1997年   31篇
  1996年   32篇
  1995年   20篇
  1994年   31篇
  1993年   17篇
  1992年   29篇
  1991年   36篇
  1990年   37篇
  1989年   51篇
  1988年   37篇
  1987年   22篇
  1986年   38篇
  1985年   26篇
  1984年   23篇
  1983年   8篇
  1982年   15篇
  1981年   11篇
  1980年   13篇
  1979年   6篇
  1978年   5篇
  1977年   12篇
  1976年   8篇
  1975年   9篇
  1968年   4篇
排序方式: 共有1402条查询结果,搜索用时 15 毫秒
1.
Gross cystic disease of the breast (GCD) is rarely seen after the menopause. Recent work has shown that by measuring electrolytes in the breast cyst fluid (BCF) it is possible to identify two principal classes of cyst, designated Type 1 (K+/Na+ greater than 1.5) and Type 2 (K+/Na+ less than 0.66). A smaller, intermediate class (Type 3) also appears to exist. We measured K+, Na+ and dehydroepiandrosterone sulphate (DHA-S) in 38 BCF samples aspirated from 33 women with GCD who had undergone spontaneous menopause at least 1 yr previously. Statistically significant correlations were found between DHA-S and cations (positive in relation to K+, P less than 0.001; negative in relation to Na+, P less than 0.001). The distribution of cyst types was shifted with respect to that characteristic of cases that occur at an earlier age: whereas Type 1 cysts predominate in menstruating women, Type 2 cysts proved more numerous in the post-menopausal subjects. The difference was statistically validated (P less than 0.001). The results seem to indicate a sharp reduction in high K+, high DHA-S cysts after the menopause, which may be paralleled by a decrease in the associated apocrine metaplasia. In view of the major biochemical differences between Type 1 and Type 2 cysts and of the suggested differences as regards cancer risk, classification of post-menopausal patients with GCD by cyst type is critical prior to any clinical trial or follow-up.  相似文献   
2.
Proximal femoral focal deficiency, an uncommon congenital anomaly, necessitates early radiologic classification for surgical planning and treatment. Objective radiographic criteria, including femoral length index, acetabular depth index, acetabular angle index, and shape of the proximal femur were determined in 49 patients before cartilaginous ossification of the femoral capital epiphysis; final classification was based on follow-up radiographs or findings at arthrography or surgery. These parameters were analyzed to determine the accuracy and contributions of each in classification. Correct classification into one of three groups was possible in 86% of cases with use of three of the parameters: femoral length index, acetabular depth index, and shape of the proximal femur. The acetabular angle was found to contribute insignificantly to classification. Magnetic resonance imaging, used in only one case, depicted the nonossified cartilaginous femoral capital epiphysis, thus obviating the need for invasive diagnostic procedures and facilitating early classification.  相似文献   
3.
Hispanic and African American adolescents are more likely than white Anglo youth to harbor misconceptions about acquired immunodeficiency syndrome (AIDS) and are also more likely to engage in intravenous drug use and sexual intercourse. This paper describes the development of an AIDS prevention curriculum that uses an interactive videodisc program to teach skills for interventions. Focus group and expert panel studies yielded suggests for intervention vignettes and scenes relevant to Hispanic and African American adolescents. The authors then developed and produced a sample curriculum, specifically designed for Hispanic youth. Content was designed to build knowledge, attitudes, and skills in handling situations where young persons are at risk for human immunodeficiency virus (HIV) infection. The feasibility of the finished pilot product was tested with adolescents and with professionals who serve ethnic and racial minority youth. Adults and Hispanic adolescent viewers rated the videodisc as enjoyable, interesting, and likely to achieve positive effects with the intended target population. Findings suggest that the interactive videodisc is a useful way to interest and help Hispanic adolescents learn ways of reducing their risk of contracting and spreading HIV infection through lifestyle practices. This developmental research in the use of interactive videodisc also provides a basis for further investigation.  相似文献   
4.
The aim of the present study was to determine if data on the number and acinar distribution of apoptotic bodies (AB) in normal liver could help in the understanding of cell kinetics in the liver, and the mechanism of early ethanol-induced liver damage. Normal male Sprague-Dawley rats were studied. They had free access to Purina chow and drinking water. Ethanol-treated rats received the drug at increasing concentration in drinking water for 5 weeks. The following parameters were measured: number of AB in the lobule, topographical localization, distance from terminal hepatic veins (THV), i.e. row of hepatocytes concerned, H1 being the closest to the THV. The results show that AB are rare in the normal liver and are always observed in zone 3, next to the THV. Of 149 THV examined, 56 showed one associated AB, exceptionally two. 74% of the AB were confined to the first row of hepatocytes (H1), 21% to H2, 4% to H3, and 1% to H4. In ethanol-treated rats the mean number of AB was 2 or 3 for each THV. 42% were found in H1, 32% in H2, 15% in H3, 7% in H4, and 4% in H5. The data show that AB are not randomly dispersed in normal liver but show a preferential acinar distribution. In addition, most AB are located in the row of liver cells immediately adjacent to the THV. If apoptosis is indeed an expression of physiological cell renewal, these findings support the concept that zone 3 contains older hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
5.
6.
Abstract Idiopathic Parkinson’s disease (IPD) patients have abnormal visual evoked potentials (VEPs) and pattern electroretinograms (PERGs), attributed to dopaminergic transmission deficiency in visual pathway, probably the retina. VEP abnormalities are not reported in multiple system atrophy (MSA). The aim of this study was to investigate and compare chromatic (Ch) red-green (R-G) and blue-yellow (B-Y), and luminance yellow-black (Y-Bk) PERGs in patients with MSA and IPD. We investigated 6 MSA patients (mean age: 62±7.4 years) not undergoing any pharmacological treatment, as well as 12 early IPD patients (mean age: 60.1±8.3 years) and 12 age-matched normal observers. ChPERGs were recorded monocularly in response to full-field equiluminant R-G, B-Y and Y-Bk horizontal gratings. In MSA only responses to R-G stimuli showed minimal insignificant changes (slight but not significant amplitude reduction without any significant latency delay); no significant abnormality was detected for B-Y and luminance Y-Bk stimuli. By contrast, in IPD all responses were reduced in amplitude and delayed in latency, above all for B-Y stimuli. Present data indicate that both chromatic and achromatic PERGs are virtually unaffected in MSA, whereas in early IPD they are clearly impaired, suggesting different pathogenic retinal mechanisms and a useful simple tool for distinguishing MSA from IPD.  相似文献   
7.
8.
The visualization of incorporation sites of the thymidine analog bromodeoxyuridine (BrdU) into DNA, detected by immunocytochemistry, has been proposed as an index of the percentage of S-phase cells in a variety of tissues and as an easy, less expensive alternative to autoradiography. This technique has not yet been applied to the study of physiological cell renewal in the normal liver. In the present study, results obtained with this method in the liver of normal young adult rats is reported. BrdU was administered in vivo and subsequent incorporation was detected by the PAP technique using monoclonal anti-BrdU antibodies. The nuclei exhibiting a positive reaction within the liver were few and accounted for about 0.45% of all hepatocytes. Positive cells were located preferentially in zone 1, which contained 82.7% of the labeled cells. Zone 2 contained 15.4%, while only 1.9% of the labeled cells were found in zone 3. Positive-staining Kupffer cell nuclei were rare (about 0.5% of all Kupffer cells) and were distributed randomly in the hepatic lobule. These findings provide quantitative data about hepatocyte renewal in the normal liver in the absence of a growth stimulus. The simplicity and the reproducibility of this technique suggests that further application of this method in situations assessing hepatic regeneration are indicated.  相似文献   
9.
10.
M A Orlandi 《Women & health》1986,11(3-4):237-251
Men and women have traditionally consumed cigarettes very differently, demonstrating widely varying patterns of prevalence during the past eight decades. For example, though the prevalence of smoking among men increased dramatically soon after the turn of the century, an analogous though less dramatic increase among women was not observed for another 25-30 years. Similarly, when a dramatic decrease in smoking prevalence among men was observed following the 1964 Surgeon General's Report, a comparable decrease among women was not seen until 15 years later. Such differences in smoking patterns have led to the widespread belief that giving up smoking is more difficult for women than it is for men. This paper reviews various studies which address this issue and suggests areas in which further research is needed.  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