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   3168篇
  免费   323篇
  国内免费   15篇
耳鼻咽喉   14篇
儿科学   142篇
妇产科学   123篇
基础医学   420篇
口腔科学   32篇
临床医学   251篇
内科学   632篇
皮肤病学   30篇
神经病学   258篇
特种医学   199篇
外科学   442篇
综合类   119篇
一般理论   3篇
预防医学   340篇
眼科学   89篇
药学   210篇
  1篇
中国医学   4篇
肿瘤学   197篇
  2021年   39篇
  2019年   40篇
  2018年   38篇
  2017年   42篇
  2016年   37篇
  2015年   47篇
  2014年   52篇
  2013年   84篇
  2012年   135篇
  2011年   110篇
  2010年   76篇
  2009年   85篇
  2008年   121篇
  2007年   102篇
  2006年   121篇
  2005年   92篇
  2004年   92篇
  2003年   101篇
  2002年   98篇
  2001年   106篇
  2000年   82篇
  1999年   87篇
  1998年   62篇
  1997年   61篇
  1996年   56篇
  1995年   56篇
  1994年   44篇
  1993年   54篇
  1992年   88篇
  1991年   79篇
  1990年   71篇
  1989年   78篇
  1988年   86篇
  1987年   83篇
  1986年   86篇
  1985年   80篇
  1984年   52篇
  1983年   54篇
  1982年   51篇
  1981年   45篇
  1980年   32篇
  1979年   39篇
  1978年   42篇
  1977年   40篇
  1976年   32篇
  1974年   27篇
  1973年   32篇
  1971年   24篇
  1969年   22篇
  1967年   27篇
排序方式: 共有3506条查询结果,搜索用时 15 毫秒
11.
12.
There has been concern about the number of interval cancers which have been detected within the National Breast Screening Programme. A series of 134 women presenting with interval cancers was studied by prospective audit and the rate and radiological classification of the tumours determined. The cancers were classified as true (67), false-negative (22), unclassifiable (28), occult (12), and minimal sign (5). The interval cancer rate did not achieve the new National Guidelines in either the first 2 years or the 3rd interval year. The false-negative cancers presented mainly in the 1st interval year, whereas the true cancers were predominantly confined to the 2nd and 3rd years. These data suggest that alterations to the screening programme may be beneficial. It may be, however, that the programme is still on the learning curve and this should be taken into account when interpreting these data.  相似文献   
13.
Acute effects of cypermethrin, a pesticide used to treat ectoparasite infestations of salmon, were assessed using the calanoid copepod Acartia tonsa. A. tonsa has been widely used for hazard assessment of chemicals in the marine environment using acute toxicity tests, but only with randomly selected adults, assuming a sex ratio of 1:1. The present study assesses the environmental hazard of cypermethrin by exposing nauplii and adult males and females, separately. Our results showed that the naupliar stages were 28 times more sensitive to cypermethrin than adults after 96 h of exposure, with LC50s of 0.005 μg L−1 and 0.142 μg L−1, respectively. Significant differences in sensitivity between sexes were only found during the first 24 h of exposure, with males being approximately twice as sensitive as females. The results of age-related variation in sensitivity are supported by studies with other species of copepods and toxicants, where the increased capacity of the adults for detoxification, the allometric differences in weight and size, and the molting process are given as explanations. Variation in sensitivity between sexes is discussed in terms of faster depuration rates in females through egg production and implications of feeding rate changes after 24 h of exposure. Our results suggested that standard toxicity test methods using A. tonsa are unsatisfactory because the most sensitive life stage is not included and sex-related differences in tolerance are not taken into account. We also found that cypermethrin caused significant mortality in Acartia at exposures concentrations from one to three orders of magnitudes lower than the recommended field treatment concentration for copepodic infestations. Received: 27 April 2001/Accepted: 1 July 2001  相似文献   
14.
Identifying blood biomarkers may be of particular value in neurologic disorders such as stroke because of the difficulty in directly studying the brain and its blood vessels. Markers of brain injury, inflammation, excitotoxicity, and oxidative damage have been evaluated for their value in stroke diagnosis, treatment, and management, but none has proved to be sensitive or specific enough for routine clinical use. However, new cellular and molecular profiling approaches using the peripheral blood offer the potential for identifying panels of genes and proteins by increasing specificity while maintaining sensitivity. Furthermore, the first biomarker for predicting stroke risk associated with atherosclerosis (lipoprotein-associated phospholipase A2) was recently approved by the United States Food and Drug Administration. The ultimate aim for stroke biomarkers is to develop rapid, easy to use, widely available, and inexpensive diagnostic tests that can be used in the clinic and in clinical trials.  相似文献   
15.
The pattern and amount of blood loss following induction of therapeutic abortion using mifepristone (RU 486) and a prostaglandin E analogue (gemeprost) was studied in 222 women of less than 63 days amenorrhoea. A single oral dose of mifepristone (400, 500 or 600 mg) was followed 48 hours later by a half or 1 mg gemeprost vaginal pessary. Complete abortion occurred in 218 (98%) women without necessity for surgical evacuation of the uterus. Bleeding commonly occurred following administration of mifepristone and prior to prostaglandin administration. The median duration of bleeding following abortion was 13 days with a range of from 1 to 44 days. There was a wide individual variation in measured blood loss between women, from 14 to 512 ml, with a median loss of 74 ml. The amount of blood loss was independent of the dose of mifepristone or prostaglandin but was significantly correlated with gestation. These results confirm that the combination of mifepristone and gemeprost is a highly effective and safe method of inducing therapeutic abortion medically. As the amount of blood loss increases with increasing gestation, it is suggested that its use should be restricted to women with amenorrhoea less than or equal to 56 days.  相似文献   
16.
Combinations of murine recombinant interleukin 3 (IL-3), purified murine macrophage colony-stimulating factor (M-CSF), and human recombinant interleukin 1 alpha (IL-1 alpha) were used to determine the effects of growth factors on the measured radiosensitivity of different populations of murine colony-forming cells (CFC). The data showed that combinations of growth factors resulted in different values of CFC radiosensitivity, being less than values observed when colony growth was stimulated using a single factor. For various combinations of growth factors, Do values ranged from 106 +/- 8 to 175 +/- 24 cGy for progenitor cells in normal bone marrow; 74 +/- 3 to 171 +/- 18 cGy for primitive multipotent CFC enriched using fluorescence-activated cell sorting; and from 46 +/- 4 to 131 +/- 10 cGy for more mature granulocyte-macrophage CFC, enriched by counterflow centrifugal elutriation. Only combinations of three factors produced the high values of Do reported in experiments using unpurified conditioned medium as a stimulus for colony formation.  相似文献   
17.
BACKGROUND: It has been established that individuals who score high on measures of psychopathy demonstrate difficulty when performing tasks requiring the interpretation of other's emotional states. The aim of this study was to elucidate the relation of emotion and cognition to individual differences on a standard psychopathy personality inventory (PPI) among a nonpsychiatric population. METHODS: Twenty participants completed the PPI. Following survey completion, a mean split of their scores on the emotional-interpersonal factor was performed, and participants were placed into a high or low group. Functional magnetic resonance imaging data were collected while participants performed a recognition task that required attention be given to either the affect or identity of target stimuli. RESULTS: No significant behavioral differences were found. In response to the affect recognition task, significant differences between high- and low-scoring subjects were observed in several subregions of the frontal cortex, as well as the amygdala. No significant differences were found between the groups in response to the identity recognition condition. CONCLUSIONS: Results indicate that participants scoring high on the PPI, although not behaviorally distinct, demonstrate a significantly different pattern of neural activity (as measured by blood oxygen level-dependent contrast)in response to tasks that require affective processing. The results suggest a unique neural signature associated with personality differences in a nonpsychiatric population.  相似文献   
18.
The purpose of this study was to determine the accuracy of FirstTemp (Intelligent Medical Systems, Carlsbad, CA) tympanic thermometer readings compared with core body temperatures obtained via pulmonary artery catheter (PAC). Five measurements were obtained on 19 cardiovascular surgery patients. Tympanic thermometer measurements tended to be higher than PAC measurements. However, most of the differences were not clinically significant. Differences found between right and left ear measurements were most likely due to poor measurement technique. When the correct technique is used, nurses can be confident that tympanic temperature readings are clinically accurate.  相似文献   
19.
We have evaluated the effects on islet function of several manipulations of the substrate and tissue culture conditions in the short term culture of human islets. Specifically, we have studied the influence of several matrices, additions to the medium, and the use of basic fibroblast growth factor (FGF)-saporin mitotoxins to eliminate fibroblastoid cells from the cultures. The human islets were obtained from the Human Islet Transplant Center at Washington University Medical Center (St. Louis, MO). Substrates used to facilitate islet attachment were poly-L-lysine, gelatin, Matrigel, collagen, and bovine corneal endothelial cell matrix. RPMI-1640 medium was supplemented with either 22.2 mM glucose or 10 micrograms/mL human insulin. FGF-saporin mitotoxin was used at a concentration of 10 nM. The greatest improvement in islet cell function in either static or stimulated situations was obtained when we used bovine corneal endothelial cell matrix as the matrix, supplemented the medium with a high concentration of glucose or insulin, and eliminated fibroblast-like cells by exposing the cultures to basic FGF-saporin mitotoxin. The conditions described in this report could greatly improve the culture of human islets for use in clinical and laboratory research.  相似文献   
20.
A mesenteric cyst with milk of calcium in an adult patient is presented. Preoperative evaluation included plain film, ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI). To our knowledge, the presence of milk of calcium in a mesenteric cyst has not been previously described.  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