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   21095篇
  免费   1688篇
  国内免费   80篇
耳鼻咽喉   267篇
儿科学   550篇
妇产科学   466篇
基础医学   2827篇
口腔科学   938篇
临床医学   1807篇
内科学   5080篇
皮肤病学   433篇
神经病学   1814篇
特种医学   733篇
外科学   3177篇
综合类   141篇
一般理论   11篇
预防医学   1581篇
眼科学   470篇
药学   1148篇
中国医学   92篇
肿瘤学   1328篇
  2023年   124篇
  2022年   387篇
  2021年   725篇
  2020年   425篇
  2019年   649篇
  2018年   804篇
  2017年   555篇
  2016年   571篇
  2015年   621篇
  2014年   880篇
  2013年   1015篇
  2012年   1557篇
  2011年   1495篇
  2010年   937篇
  2009年   762篇
  2008年   1168篇
  2007年   1244篇
  2006年   1084篇
  2005年   1042篇
  2004年   876篇
  2003年   828篇
  2002年   712篇
  2001年   380篇
  2000年   343篇
  1999年   378篇
  1998年   166篇
  1997年   157篇
  1996年   121篇
  1995年   113篇
  1994年   102篇
  1993年   104篇
  1992年   243篇
  1991年   220篇
  1990年   183篇
  1989年   203篇
  1988年   180篇
  1987年   154篇
  1986年   161篇
  1985年   159篇
  1984年   115篇
  1983年   97篇
  1982年   55篇
  1981年   68篇
  1979年   81篇
  1978年   63篇
  1976年   52篇
  1975年   55篇
  1974年   44篇
  1973年   55篇
  1972年   50篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
5H-Mebendazole and some related heterocyclic methyl carbamates were synthesized and their anthelmintic activity against Caenorhabditis elegans was determined. In order to study the influence of the heteroaromatic region with regard to the carbamate moiety on biological activity, the molecular electrostatic potentials (MEP) of all structures were calculated and a structure-activity relationship (SAR) was established. The electrostatic pattern of activity includes two minima of the carbamate moiety, a third heterocyclic minimum, and a pi-electronic region.  相似文献   
53.
Several parallels exist between preeclampsia and atherosclerosis. Both are multifactorial diseases that share risk factors such as obesity, insulin resistance, lipid abnormalities, and elevated serum homocysteine. There are also similarities in the biochemical changes seen in both diseases, including elevated serum triglycerides, decreased HDL cholesterol and enhanced formation of small, dense LDL particles as well as vascular atherosclerotic lesions. Chronic infection with Chlamydia pneumoniae has been linked to coronary artery disease. This study evaluated a possible link between the incidence of preeclampsia and infection with C. pneumoniae by examining the rate of seropositivity in 81 women with preeclampsia, and 206 women with normal pregnancies. Although our data confirmed well-known risk factors for preeclampsia such as obesity, diabetes, and hypertension, we found no difference in the rate of seropositivity between preeclampsia and normal pregnancy. On the contrary, the presence of chlamydial antibodies was lower in preeclampsia. Multiparous women with preeclampsia showed a significantly lower rate of seropositivity than multiparous normal women and nulliparous preeclamptics. In addition, women with a history of preeclampsia who developed preeclampsia in the current pregnancy also had a significantly lower rate of seropositivity.  相似文献   
54.
55.
Apical ballooning is a novel clinical entity reported in different contexts of physical and psychological stress, which is more common in middle-aged women. Of unknown etiology, the syndrome is characterized by a sudden and transient dilatation of the left ventricular apex in the absence of obstructive atherosclerotic coronary disease or evidence of myocardial necrosis, with total late recovery of ventricular function. The authors report the case of a 53-year-old woman who was admitted to the emergency room with left arm ischemia and low cardiac output, requiring ventilatory support. Left catheterization showed typical medial and apical myocardial dysfunction, with normal coronary arteries. Transesophageal echocardiography revealed a thrombus attached to the lower face of the aortic arch, which probably explained the thromboembolism of the arm but was unlikely to be the cause of the left ventricular dysfunction since there were no enzymatic or electrocardiographic signs of myocardial necrosis and normal wall motion was fully recovered.  相似文献   
56.
57.
58.
Thoracic trauma in children: an indicator of increased mortality   总被引:2,自引:0,他引:2  
This study was undertaken to assess the significance of thoracic trauma as a marker of morbidity and mortality in children. During a 34-month period, 2,086 children younger than 15 years old were consecutively admitted to a Level I pediatric trauma center with blunt or penetrating trauma. For each child we prospectively recorded Trauma Score (TS), Injury Severity Score, (ISS), medical, and etiologic data. One hundred four children (4.4%) presented with thoracic trauma. The most common mechanisms of injury were pedestrian injury (36%), motor vehicle crashes (32%), and armed assault (12%). The most common injuries were pulmonary contusion (48%), pneumothorax, hemothorax, or pneumohemothorax (39%), and rib fractures (32%). Multisystem injury was present in 82% of the children. The mean TS and ISS were 11 and 27, respectively, significantly worse than scores for children without thoracic injury (15 and 7; P less than .0001). Seventy-one percent of the children were admitted to the intensive care unit, where they stayed an average of 6 days; 20% required surgery. The mortality rate was 26%. Injuries to the heart or great vessels had the highest mortality rate (75%), followed by hemothorax (53%), lung laceration (43%), and rib fracture (42%). Mortality for children with isolated chest injury was 5%, compared with rates of 20% for abdominal and chest trauma, 35% for head and chest trauma, and 39% for trauma to the head, chest, and abdomen. Less than 5% of the admissions to a pediatric trauma center incurred thoracic injury.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
59.
An HPLC method is described for the simultaneous and rapid determination of sulfasalazine (salicylazosulfapyridine) and two of its metabolites, sulfapyridine and N-acetylsulfapyridine, in human serum. The range of quantitation is 0.1 to 12 micrograms/mL for sulfasalazine and sulfapyridine and 0.25 to 12 micrograms/mL for N-acetylsulfapyridine. Serum is mixed with acetonitrile containing the internal standard sulfamethazine and the ion-pairing agent tetraethylammonium chloride. The acetonitrile extract is concentrated and analyzed by HPLC, using a new polymer-based column, and detected by UV spectroscopy at 270 nm. This paper is the first both to describe the simultaneous analysis of all three of the compounds from serum and to present sulfasalazine concentration-time data following oral administration to humans.  相似文献   
60.
The mosquito control potential of the mosquitofish and Bacillus thuringiensis var. israelensis (Bti) were evaluated in experimental wild rice fields in Lake County, California. Fields were assigned one of six treatment: control, 1.1 kg/ha G. affinis, 3.4 kg/ha G. affinis, Bti only (6 kg/ha Vectobac granules), 1.1 kg/ha G. affinis plus Bti and 3.4 kg/ha G. affinis plus Bti. Gambusia affinis, at both release rates, significantly reduced the mosquito population at densities exceeding 100 fish/minnow trap. Treatments with Bti significantly reduced larval population; however, the populations in the fields without fish rebounded to pretreatment levels within two weeks. In fields stocked with G. affinis and treated with Bti, populations remained low after Bti treatment. Nontarget populations of arthropods were significantly lower in fields stocked with G. affinis than in fields without fish on one or more sampling dates.  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