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   515315篇
  免费   34115篇
  国内免费   617篇
耳鼻咽喉   6898篇
儿科学   16892篇
妇产科学   13541篇
基础医学   85260篇
口腔科学   14552篇
临床医学   44529篇
内科学   94062篇
皮肤病学   12246篇
神经病学   36326篇
特种医学   18548篇
外国民族医学   63篇
外科学   77294篇
综合类   8481篇
一般理论   118篇
预防医学   39043篇
眼科学   12176篇
药学   40700篇
中国医学   1007篇
肿瘤学   28311篇
  2018年   4953篇
  2015年   4544篇
  2014年   6105篇
  2013年   9600篇
  2012年   12941篇
  2011年   14343篇
  2010年   8342篇
  2009年   7811篇
  2008年   13762篇
  2007年   14772篇
  2006年   15037篇
  2005年   14457篇
  2004年   14144篇
  2003年   13489篇
  2002年   13337篇
  2001年   24144篇
  2000年   25141篇
  1999年   20633篇
  1998年   5468篇
  1997年   4734篇
  1996年   5071篇
  1995年   4644篇
  1994年   4332篇
  1993年   4152篇
  1992年   15768篇
  1991年   16359篇
  1990年   16471篇
  1989年   15832篇
  1988年   14643篇
  1987年   14475篇
  1986年   13646篇
  1985年   13010篇
  1984年   9655篇
  1983年   8262篇
  1982年   4568篇
  1981年   4239篇
  1979年   9431篇
  1978年   6871篇
  1977年   5779篇
  1976年   5609篇
  1975年   6402篇
  1974年   7637篇
  1973年   7137篇
  1972年   6966篇
  1971年   6692篇
  1970年   6178篇
  1969年   5900篇
  1968年   5570篇
  1967年   5020篇
  1966年   4455篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.

Purpose

Suppression of respiratory movement of the liver would be desirable for high-precision radiation therapy for liver tumors. We aimed to investigate the effect of our original device-free compressed shell fixation method and breathing instruction on suppression of respiratory movement. The characteristics of liver motion based on the movement of a fiducial marker were also analyzed.

Methods and Materials

First, respiratory amplitudes of the liver with the device-free compressed shell were analyzed from the data of 146 patients. The effect of this shell fixing method on liver movement was evaluated. Second, as another cohort study with 166 patients, interfractional internal motion of the liver for patients fixed in the shell was calculated using the fiducial marker coordinate data of images for position setting before daily irradiation. Third, in another 12 patients, intrafractional internal motion was calculated from the fiducial marker coordinate data using x-ray images before and after irradiation.

Results

The median respiratory movement without the shell, after fixing with the shell, and after instructing on the breathing method with the shell was 14.2 (interquartile range, 10.7-19.8), 11.5 (8.6-17.5), and 10.4 mm (7.3-15.8), respectively. Systematic and random errors of interfractional internal motion were all ≤2 mm in the left-right and anteroposterior directions and 3.7 and 3.0 mm, respectively, in the craniocaudal direction. Systematic and random errors of intrafractional internal motion were all ≤1.3 mm in the left-right and anteroposterior directions and 0.8 and 2.4 mm, respectively, in the craniocaudal direction.

Conclusions

The device-free compressed shell fixation method was effective in suppressing the respiratory movement of the liver. Irradiation position matching using the fiducial marker can correct the interfractional internal motion on each day, which would contribute to the reduction of the margin to be given around the target.  相似文献   
33.
34.
Mitochondria are known primarily as the location of the electron transport chain and energy production in cells. More recently, mitochondria have been shown to be signaling centers for apoptosis and inflammation. Reactive oxygen species (ROS) generated as by-products of the electron transport chain within mitochondria significantly impact cellular signaling pathways. Because of the toxic nature of ROS, mitochondria possess an antioxidant enzyme, superoxide dismutase 2 (SOD2), to neutralize ROS. If mitochondrial antioxidant enzymes are overwhelmed during severe infections, mitochondrial dysfunction can occur and lead to multiorgan failure or death. Pseudomonas aeruginosa is an opportunistic pathogen that can infect immunocompromised patients. Infochemicals and exotoxins associated with P. aeruginosa are capable of causing mitochondrial dysfunction. In this work, we describe the roles of SOD2 and mitochondrial ROS regulation in the zebrafish innate immune response to P. aeruginosa infection. sod2 is upregulated in mammalian macrophages and neutrophils in response to lipopolysaccharide in vitro, and sod2 knockdown in zebrafish results in an increased bacterial burden. Further investigation revealed that phagocyte numbers are compromised in Sod2-deficient zebrafish. Addition of the mitochondrion-targeted ROS-scavenging chemical MitoTEMPO rescues neutrophil numbers and reduces the bacterial burden in Sod2-deficient zebrafish. Our work highlights the importance of mitochondrial ROS regulation by SOD2 in the context of innate immunity and supports the use of mitochondrion-targeted ROS scavengers as potential adjuvant therapies during severe infections.  相似文献   
35.
36.
37.
38.
39.
Thyroid diseases are common, and use of levothyroxine is increasing worldwide. We investigated the influence of gender, race and socioeconomic status on the diagnosis and treatment of thyroid disorders using data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), a multicenter cohort study of civil servants (35-74 years of age) from six Brazilian cities. Diagnosis of thyroid dysfunction was by thyrotropin (TSH), and free thyroxine (FT4) if TSH was altered, and the use of specific medications. Multivariate logistic regression models were constructed using overt hyperthyroidism/hypothyroidism and levothyroxine use as dependent variables and sociodemographic characteristics as independent variables. The frequencies of overt hyper- and hypothyroidism were 0.7 and 7.4%, respectively. Using whites as the reference ethnicity, brown, and black race were protective for overt hypothyroidism (OR=0.76, 95%CI=0.64-0.89, and OR=0.53, 95%CI=0.43-0.67, respectively, and black race was associated with overt hyperthyroidism (OR=1.82, 95%CI=1.06-3.11). Frequency of hypothyroidism treatment was higher in women, browns, highly educated participants and those with high net family incomes. After multivariate adjustment, levothyroxine use was associated with female gender (OR=6.06, 95%CI=3.19-11.49) and high net family income (OR=3.23, 95%CI=1.02-10.23). Frequency of hyperthyroidism treatment was higher in older than in younger individuals. Sociodemographic factors strongly influenced the diagnosis and treatment of thyroid disorders, including the use of levothyroxine.  相似文献   
40.
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