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   5906篇
  免费   393篇
  国内免费   26篇
耳鼻咽喉   18篇
儿科学   181篇
妇产科学   98篇
基础医学   798篇
口腔科学   120篇
临床医学   656篇
内科学   1335篇
皮肤病学   75篇
神经病学   798篇
特种医学   198篇
外科学   787篇
综合类   37篇
一般理论   1篇
预防医学   413篇
眼科学   104篇
药学   374篇
中国医学   14篇
肿瘤学   318篇
  2023年   25篇
  2022年   60篇
  2021年   121篇
  2020年   62篇
  2019年   114篇
  2018年   154篇
  2017年   99篇
  2016年   108篇
  2015年   129篇
  2014年   148篇
  2013年   257篇
  2012年   431篇
  2011年   452篇
  2010年   257篇
  2009年   239篇
  2008年   402篇
  2007年   434篇
  2006年   422篇
  2005年   419篇
  2004年   370篇
  2003年   346篇
  2002年   335篇
  2001年   73篇
  2000年   70篇
  1999年   75篇
  1998年   78篇
  1997年   73篇
  1996年   47篇
  1995年   51篇
  1994年   46篇
  1993年   43篇
  1992年   34篇
  1991年   20篇
  1990年   39篇
  1989年   21篇
  1988年   21篇
  1987年   16篇
  1986年   14篇
  1985年   21篇
  1984年   13篇
  1983年   14篇
  1982年   19篇
  1981年   17篇
  1979年   8篇
  1978年   9篇
  1977年   12篇
  1976年   10篇
  1975年   10篇
  1974年   17篇
  1963年   8篇
排序方式: 共有6325条查询结果,搜索用时 15 毫秒
71.
通过摇瓶发酵试验研究H2O2对枯草芽孢杆菌ATCC 21616生长代谢及产苷的影响.结果表明:添加时间、浓度以及两者的交互作用显著影响腺苷的积累,在12h添加20mg/L的H2O2最利于腺苷的合成,产苷量由7.03g/L增至7.79g/L.同时也研究了H2O2添加对代谢过程中糖耗及pH的影响.  相似文献   
72.
Background: The association between vitamin D and weight gain remains controversial due to important limitations in the studies. We investigated the relationship between vitamin D levels and 5 and 10 years of weight and waist circumference change in a population-based prospective cohort study. Methods: Prospective study including participants aged between 35 and 75 years living in the city of Lausanne, Switzerland. Weight and waist change at 5- and 10-year follow-up were assessed according to baseline vitamin D status (normal, insufficiency and deficiency). Results: A total of 3638 participants (47.9 % women, mean age 51.6 ± 10.4 years) were included for the 5-year follow-up. No association was found between vitamin D categories and weight change, multivariate-adjusted average ± standard error: 1.6 ± 0.3, 1.5 ± 0.2 and 1.2 ± 0.1 kg for normal, insufficiency and deficiency, respectively, p = 0.159. For waist change, the corresponding values were 3.3 ± 0.4, 3.3 ± 0.2 and 3.4 ± 0.2 cm, p = 0.792. For the 10-year follow-up, data from 2999 participants (45.8% women, mean age 50.8 ± 10.3 years) were used. No association was found for weight 2.3 ± 0.4, 2.3 ± 0.2 and 2.0 ± 0.2 kg, p = 0.588, or for waist 3.7 ± 0.4, 3.6 ± 0.3 and 4.2 ± 0.2 cm for normal, insufficiency and deficiency, respectively, p = 0.259. Conclusion: No association between vitamin D status and weight or waist gain at 5- and 10-year follow-up was found.  相似文献   
73.
Objective To assess whether hyponatremia in acute neurological patients is associated with the syndrome of inappropriate antidiuretic hormone secretion (SIADH) or with the cerebral salt-wasting syndrome (CSWS). Design Clinical, controlled, prospective study. Setting Department of intensive care of a tertiary care academic hospital. Patients Forty acute neurological patients with hyponatremia suggesting SIADH or CSWS (20) or with normonatremia (20). Interventions None. Measurements and main results Measurement of clinical and biological variables. Measurement of blood, plasma, and red blood cell volumes to discriminate SIADH and CSWS. Renal, adrenal and thyroid functions were normal in all patients. Average blood, plasma, and red blood cell volumes were 54, 37 and 17 ml/kg in control patients and 54, 37 and 18 ml/kg in hyponatremic patients, respectively. Conclusions The adequate blood volumes in hyponatremic patients confirm the diagnosis of SIADH and do not support the concept of CSWS. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
74.
75.
AIM: To assess the retinal function in patients with dense cataracts in resource poor settings in Kinshasa, DR Congo. METHODS: In a tertiary eye care center, the Purkinje entoptic test was performed as part of the ophthalmological examination in 98 eyes in patients with cataract, using a penlight. Totally 92 cataract patients including 86 patients suffered from unilateral and 6 from bilateral cataracts were included in the study. The investigator asked the patients about their perception of the vascular pattern most commonly described as a leafless or dead tree. Visual acuity≥6/60 was considered an indication of good visual function and visual acuity<6/60 of poor function. Following small incision cataract surgery, best corrected visual acuity (BCVA) was determined and compared with the preoperative findings. RESULTS: Out of 98 eyes, there were 80 (81.6%) where the Purkinje entoptic phenomenon was reported by the patients. After cataract surgery, out of the 80 eyes, there were 75 (93.8%) with a BCVA of better than 6/60, whereas in 5 eyes (6.2%), BCVA was 6/60 or less. Out of the 18 eyes (18.4%) where no Purkinje tree was recognized, there were 14 (77.8%) with BCVA of better than 6/60, whereas in 4 (22.2%) BCVA was 6/60 or less. CONCLUSION: The Purkinje entoptic test is successfully used for preoperative assessment of retinal function in patients with dense cataract. However, further investigation and refinement of the test is necessary to validate the method for use in sub-Saharan conditions.  相似文献   
76.
77.
78.
The broad aim underlying the present research was to investigate the distribution and homing of bone marrow‐derived macrophages in a rodent model of transient middle cerebral artery occlusion using MRI and ultrasmall superparamagnetic iron oxide (USPIO) to magnetically label bone marrow‐derived macrophages. The specific aim was to assess the intra‐carotid infusion route for bone marrow‐derived macrophage delivery at reperfusion. Fifteen Sprague–Dawley rats sustained 1 h of middle cerebral artery occlusion. USPIO‐labeled bone marrow‐derived macrophages were slowly injected for 5 min immediately after reperfusion in ischemic animals (n = 7), 1 h after the end of surgery in sham animals (n = 5) and very shortly after anesthesia in healthy animals (n = 3). Multiparametric MRI was performed at day 0, just after cell administration, and repeated at day 1. Immunohistological analysis included Prussian blue for iron detection and rat endothelial cell antigen‐1 for endothelium visualization. Intra‐carotid cell delivery brought a large number of cells to the ipsilateral hemisphere of the brain, as seen on both MRI and immunohistology. However, it was associated with high mortality (50%). The study of sham animals demonstrated that intra‐carotid cell delivery could induce ischemic lesions and may thus favor additional brain damage. The present study highlights severe drawbacks to the intra‐carotid delivery of macrophages at the time of reperfusion in this rodent model of transient cerebral ischemia. Multiparametric MRI appears to be a method of choice to monitor longitudinally the effects of cell infusion, allowing the assessment of both cell fate with the help of magnetic labeling and of potential tissue damage. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
79.
80.
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