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   3369篇
  免费   165篇
  国内免费   14篇
耳鼻咽喉   36篇
儿科学   152篇
妇产科学   272篇
基础医学   312篇
口腔科学   48篇
临床医学   262篇
内科学   730篇
皮肤病学   37篇
神经病学   288篇
特种医学   81篇
外科学   496篇
综合类   17篇
一般理论   1篇
预防医学   128篇
眼科学   98篇
药学   171篇
中国医学   1篇
肿瘤学   418篇
  2023年   11篇
  2022年   19篇
  2021年   58篇
  2020年   33篇
  2019年   46篇
  2018年   74篇
  2017年   49篇
  2016年   54篇
  2015年   73篇
  2014年   89篇
  2013年   138篇
  2012年   175篇
  2011年   191篇
  2010年   110篇
  2009年   90篇
  2008年   182篇
  2007年   236篇
  2006年   242篇
  2005年   255篇
  2004年   242篇
  2003年   231篇
  2002年   186篇
  2001年   49篇
  2000年   41篇
  1999年   49篇
  1998年   39篇
  1997年   25篇
  1996年   32篇
  1995年   47篇
  1994年   33篇
  1993年   36篇
  1992年   36篇
  1991年   44篇
  1990年   25篇
  1989年   18篇
  1988年   25篇
  1987年   32篇
  1986年   29篇
  1985年   16篇
  1984年   23篇
  1983年   30篇
  1982年   16篇
  1981年   20篇
  1980年   15篇
  1979年   8篇
  1978年   16篇
  1977年   15篇
  1975年   6篇
  1974年   6篇
  1973年   6篇
排序方式: 共有3548条查询结果,搜索用时 15 毫秒
61.
We compared exhaled breath condensate (EBC) and induced sputum (IS) for assessing inflammation in pulmonary diseases in patients with obstructive lung disease (n = 20), persistent cough >6 months (n = 20), interstitial lung disease (n = 25) and controls (n = 10). EBC was collected by suspending a Teflon perfluoroalkoxy tube installed in an ice-filled container and connected to a polypropylene test tube. IS was recovered after 20’ inhalation of 3% saline with an ultrasonic nebulizer, and 300 cells were differentially counted in cytospin Giemsa-stained slides. H202 was measured by a method based on oxidation of phenolsulfonphthalein (phenol red) mediated by horseradish peroxidases and H202. Pulmonary function tests were performed by conventional methods. H202 levels in EBC and % eosinophils in IS were significantly different between groups. A positive and significant correlation was found between % eosinophils in IS and the levels of H202 in EBC for each group and for all patients combined.  相似文献   
62.
Studies of visual function in behaving subjects require that stimuli be positioned reliably on the retina in the presence of eye movements. Fixational eye movements scatter stimuli about the retina, inflating estimates of receptive field dimensions, reducing estimates of peak responses, and blurring maps of receptive field subregions. Scleral search coils are frequently used to measure eye position, but their utility for correcting the effects of fixational eye movements on receptive field maps has been questioned. Using eye coils sutured to the sclera and preamplifiers configured to minimize cable artifacts, we reexamined this issue in two rhesus monkeys. During repeated fixation trials, the eye position signal was used to adjust the stimulus position, compensating for eye movements and correcting the stimulus position to place it at the desired location on the retina. Estimates of response magnitudes and receptive field characteristics in V1 and in LGN were obtained in both compensated and uncompensated conditions. Receptive fields were narrower, with steeper borders, and response amplitudes were higher when eye movement compensation was used. In sum, compensating for eye movements facilitated more precise definition of the receptive field. We also monitored horizontal vergence over long sequences of fixation trials and found the variability to be low, as expected for this precise behavior. Our results imply that eye coil signals can be highly accurate and useful for optimizing visual physiology when rigorous precautions are observed.  相似文献   
63.
Erythropoietin (Epo) is the main erythropoietic hormone. Recombinant human Epo (rHuEpo) is thus used in clinical practice for the treatment of anemia. Accumulating data reveals that Epo exerts pleiotropic activities. We have previously shown an anti-neoplastic activity of Epo in murine multiple myeloma (MM) models, and in MM patients. Our findings that this anti-neoplastic effect operates via CD8+ T lymphocytes led us to hypothesize that Epo possesses a wider range of immunomodulatory functions. Here we demonstrate the effect of Epo on B lymphocyte responses, focusing on three experimental models: (i) tumor-bearing mice, (5T2 MM mouse); (ii) antigen-injected healthy mice; and (iii) antigen-injected transgenic mice (tg6), overexpressing human Epo. In the MM model, despite bone marrow dysfunction, Epo-treated mice retained higher levels of endogenous polyclonal immunoglobulins, compared to their untreated controls. In both Epo-treated wild type and tg6 mice, Epo effect was manifested in the higher levels of splenocyte proliferative response induced in vitro by lipopolysaccharide. Furthermore, these mice had increased in vivo production of anti-dinitrophenyl (DNP) antibodies following immunization with DNP-keyhole limpet hemocyanin. Epo-treated mice showed an enhanced immune response also to the clinically relevant hepatitis B surface antigen. These findings suggest a potential novel use of rHuEpo as an immunomodulator.  相似文献   
64.
65.
66.
67.
68.
The phenomenon of acute cholecystitis complicating an unrelated operation has been reported with increasing frequency, and may be preceded by a variety of operative procedures and a lack of previous biliary tract symptoms. Among eight such patients treated by us, seven developed acute cholecystitis postoperatively, and in one it was discovered during operation for bleeding duodenal ulcer. Two patients had undergone wide excision of the breast; two, highly selective vagotomy; one, nephrolithotomy; one, truncal vagotomy and gastroenterostomy; and one, left hemicolectomy and colostomy. In three patients, urgent cholecystectomy was performed, and four were treated conservatively with subsequent elective cholecystectomy. Histopathological studies revealed acute and chronic cholecystitis in all eight patients and cholelithiasis in four. One patient died in septic shock. Numerous contributing factors have been suggested, including hypovolemia and biliary stasis, as well as the presence of stones. It would appear that chronic cholecystitis or other biliary pathology, as found in our eight patients, is a major factor in the development of this manifestation.  相似文献   
69.
OBJECTIVE: Azathioprine and 6-mercaptopurine interact in purine metabolism and DNA synthesis, thus their potential mutagenic effects have been of concern in the management of inflammatory bowel disease (IBD), especially in patients of childbearing age. Although several clinical studies have indicated their safety in both reproduction and pregnancy, in a recent large epidemiological study concerns were raised about their adverse effects in pregnant patients with IBD, and experimental or basic data on this subject are limited. The aim of this study was to investigate sperm production, sperm quality, and reproductive outcome following prolonged 6-MP administration to male mice. MATERIAL AND METHODS: Highly inbred Balb/c adult male mice were used. 6-MP at doses of 2, 5, and 8 mg/kg (n = 9 for each group) was given daily for 51 days and the treatment group was compared with controls. After 45 days of treatment, the mice were mated with females. Following 13 days of pregnancy, the products of conception were evaluated and live fetuses were examined for gross malformations. Sperm production and morphology were examined after 51 days of 6-MP administration. RESULTS: Treatment with 6-MP at all doses did not affect sperm morphology and sperm production in the testicular tubules, as compared with controls (70% normal sperm). However, pregnancy rates were inversely related to escalating doses of 6-MP: 55%, 41%, 28%, and 16% for control, 2, 5, and 8 mg/kg groups, respectively. Resorption rates (abortions) were 21% in the control group as compared with 45-50% in all the treatment groups, but the incidence of major congenital malformations was not increased. CONCLUSIONS: Long-term 6-MP treatment in male mice did not impair sperm production and sperm morphology. However, a significantly high rate of embryonic resorption indicated occult sperm damage. Thus, normal sperm analysis does not necessarily imply that sperm damage at genetic level did not occur. It is difficult to extrapolate from these results to the clinical use of 6-MP/azathioprine in IBD patients; however, further basic genetic testing for DNA damage and clinical follow-up are warranted.  相似文献   
70.
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