全文获取类型
收费全文 | 988篇 |
免费 | 88篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 53篇 |
妇产科学 | 7篇 |
基础医学 | 98篇 |
口腔科学 | 47篇 |
临床医学 | 98篇 |
内科学 | 169篇 |
皮肤病学 | 27篇 |
神经病学 | 22篇 |
特种医学 | 226篇 |
外科学 | 175篇 |
综合类 | 35篇 |
预防医学 | 55篇 |
眼科学 | 4篇 |
药学 | 35篇 |
肿瘤学 | 45篇 |
出版年
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 13篇 |
2015年 | 9篇 |
2014年 | 19篇 |
2013年 | 8篇 |
2012年 | 10篇 |
2011年 | 19篇 |
2010年 | 35篇 |
2009年 | 31篇 |
2008年 | 39篇 |
2007年 | 28篇 |
2006年 | 34篇 |
2005年 | 19篇 |
2004年 | 21篇 |
2003年 | 16篇 |
2002年 | 27篇 |
2001年 | 36篇 |
2000年 | 25篇 |
1999年 | 21篇 |
1998年 | 43篇 |
1997年 | 50篇 |
1996年 | 45篇 |
1995年 | 37篇 |
1994年 | 27篇 |
1993年 | 35篇 |
1992年 | 29篇 |
1991年 | 27篇 |
1990年 | 20篇 |
1989年 | 30篇 |
1988年 | 35篇 |
1987年 | 54篇 |
1986年 | 27篇 |
1985年 | 21篇 |
1984年 | 9篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 21篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 22篇 |
1975年 | 10篇 |
1972年 | 3篇 |
1934年 | 4篇 |
1933年 | 3篇 |
1930年 | 3篇 |
1927年 | 4篇 |
1926年 | 4篇 |
排序方式: 共有1098条查询结果,搜索用时 15 毫秒
71.
Jill R Stewart Rebecca J Gast Roger S Fujioka Helena M Solo-Gabriele J Scott Meschke Linda A Amaral-Zettler Erika del Castillo Martin F Polz Tracy K Collier Mark S Strom Christopher D Sinigalliano Peter DR Moeller A Fredrick Holland 《Environmental health : a global access science source》2008,7(Z2):S3
Innovative research relating oceans and human health is advancing our understanding of disease-causing organisms in coastal ecosystems. Novel techniques are elucidating the loading, transport and fate of pathogens in coastal ecosystems, and identifying sources of contamination. This research is facilitating improved risk assessments for seafood consumers and those who use the oceans for recreation. A number of challenges still remain and define future directions of research and public policy. Sample processing and molecular detection techniques need to be advanced to allow rapid and specific identification of microbes of public health concern from complex environmental samples. Water quality standards need to be updated to more accurately reflect health risks and to provide managers with improved tools for decision-making. Greater discrimination of virulent versus harmless microbes is needed to identify environmental reservoirs of pathogens and factors leading to human infections. Investigations must include examination of microbial community dynamics that may be important from a human health perspective. Further research is needed to evaluate the ecology of non-enteric water-transmitted diseases. Sentinels should also be established and monitored, providing early warning of dangers to ecosystem health. Taken together, this effort will provide more reliable information about public health risks associated with beaches and seafood consumption, and how human activities can affect their exposure to disease-causing organisms from the oceans. 相似文献
72.
Prevalence of risk factors for cardiovascular disease in Canadians 55 to 74 years of age: results from the Canadian Heart Health Surveys, 1986-1992 总被引:1,自引:1,他引:0 下载免费PDF全文
DB Langille MR Joffres KM MacPherson P Andreou SA Kirkland DR MacLean 《Canadian Medical Association journal》1999,161(8):S3-S9
BACKGROUND: By 2016, the proportion of Canadians older than 65 years of age will increase to 16%, and there will be an increase in the absolute number of cases of cardiovascular disease in older Canadians. The Canadian Heart Health Surveys database provides information about this population upon which health policy related to cardiovascular disease can be based. This paper presents for the first time population-based data on the risk factors for cardiovascular disease in older Canadians. METHODS: Canadians from all 10 provinces participated in surveys of cardiovascular risk factors; health insurance registries were used as sampling frames. In each province, probability samples of 2200 adults 18 to 74 years old not living in institutions, on reserves or in military camps were asked to participate in interviews and to undergo testing at clinics for major risk factors for cardiovascular disease. RESULTS: A total of 2739 men (response rate 70%) and 2617 women (response rate 66%) aged 55 to 74 years participated in the survey and also provided follow-up clinical measurements at the clinic. Overall, 52% of participants were hypertensive, 26% had isolated systolic hypertension, and 30% had a total blood cholesterol level of 6.2 mmol/L or greater. Rates of current smoking were lower in women than men (17% v. 22%). Overall, 87% of men and 78% of women who were current smokers smoked at least 10 cigarettes per day. Only slightly more than half of participants exercised at least once a week for at least 15 minutes, and almost half had a body mass index of 27 or greater. In only 4% was no major risk factor for cardiovascular disease detected. INTERPRETATION: Significant numbers of older Canadians have one or more major risk factors for cardiovascular disease. Many of these risk factors are amenable to modification. 相似文献
73.
磁共振胰胆管造影在阻塞性黄疸诊断中的应用 总被引:7,自引:2,他引:7
目的 评价磁共振胰胆管造影 (MRCP)技术在阻塞性黄疸诊断中的临床应用价值。方法 采用GE超导0 .5T ,Vectra 2磁共振成像仪 ,快速自旋回波 (FSE)重T2 加权扫描及最大强度投影 (MIP)重建图像 ,对 48例阻塞性黄疸患者作MRCP检查 ,所有患者均经手术证实。结果 各种病变的MRCP图像均有其特征性表达 ,MRCP对阻塞性黄疸的定位准确率为 10 0 % ,定性准确率为 93 .8%。结论 MRCP对阻塞性黄疸的诊断是一种有效、安全、可靠的方法。 相似文献
74.
75.
Linkage of the MHC to familial multiple sclerosis suggests genetic heterogeneity. The Multiple Sclerosis Genetics Group 总被引:5,自引:0,他引:5
Haines JL; Terwedow HA; Burgess K; Pericak-Vance MA; Rimmler JB; Martin ER; Oksenberg JR; Lincoln R; Zhang DY; Banatao DR; Gatto N; Goodkin DE; Hauser SL 《Human molecular genetics》1998,7(8):1229-1234
Multiple sclerosis (MS) is a demyelinating autoimmune disease of the
central nervous system. While its etiology is not well understood, genetic
factors are clearly involved. Until recently, most genetic studies in MS
have been association studies using the case-control design testing
specific candidate genes and studying only sporadic cases. The only
consistently replicated finding has been an association with the HLA-DR2
allele within the major histocompatibility complex (MHC) on chromosome 6.
Using the genetic linkage design, however, evidence for and against linkage
of the MHC to MS has been found, fostering suggestions that sporadic and
familial MS have different etiologies. Most recently, two of four genomic
screens demonstrated linkage to the MHC, although specific allelic
associations were not tested. Here, a dataset of 98 multiplex families was
studied to test for an association to the HLA-DR2 allele in familial MS and
to determine if genetic linkage to the MHC was due solely to such an
association. Three highly polymorphic markers (HLA-DR, D6S273 and TNFbeta)
in the MHC demonstrated strong genetic linkage (parametric lod scores of
4.60, 2.20 and 1.24, respectively) and a specific association with the
HLA-DR2 allele was confirmed (TDT; P < 0.001). Stratifying the results
by HLA-DR2 status showed that the linkage results were limited to families
segregating HLA-DR2 alleles. These results demonstrate that genetic linkage
to the MHC can be explained by the HLA-DR2 allelic association. They also
indicate that sporadic and familial MS share a common genetic
susceptibility. In addition, preliminary calculations suggest that the MHC
explains between 17 and 62% of the genetic etiology of MS. This
heterogeneity is also supported by the minority of families showing no
linkage or association with loci within the MHC.
相似文献
76.
The results of Kr-81m/Tc-99m ventilation-perfusion (VP) lung scintigraphy were correlated with the results of pulmonary angiography for 74 patients suspected of having pulmonary embolism (PE). Among patients having a diagnostic scan, the sensitivity and specificity of scintigraphy were 91% and 94%, respectively. Also, 157 consecutive cases of Kr-81m/Tc-99m VP lung scintigraphy were reviewed, and the frequency of an indeterminate scan was found to be 22%. A similar frequency was found for VP scintigraphy with xenon-133. Of eight patients who had indeterminate scans due to the presence of a single VP mismatch, four were demonstrated to have PE by angiography. Kr-81m is an excellent agent for VP scanning in cases of suspected PE, offering accuracy in diagnosis as well as favorable physical properties. 相似文献
77.
78.
79.
Negative charge distribution and density on the surface of oxygenated normal and sickle red cells 总被引:2,自引:0,他引:2
Negative charges on the external surface of red cells were visualized by colloidal iron hydroxide labelling of 50% of the membrane area after osmotic hemolysis and glutaraldehyde fixation. Counts were made over randomly selected areas on electron micrographs at 350,000 x magnification. Statistical analyses showed that at the 95% level of confidence there was no significant difference between oxygenated normal (AA) and sickle (SS) cells in either the distribution or the density of negative charges. 相似文献
80.
Chest computed tomography (CT), including high-resolution CT with thin (1.5-mm) sections was used to evaluate proved (pathologically or clinically) lymphangitic spread (LS) of tumor in 12 patients. These appearances were compared with thin-section scans obtained in 11 healthy subjects. Thin-section CT demonstrated findings consistent with thickening of the normal lung interstitium. In all patients, thin sections showed an increase in the number of peripheral lines (1-2 cm in length) that were diffuse in generalized disease and localized in focal disease. Normal peripheral arcades were not increased in number, but the limbs forming the arcades were thickened in all patients. A diffuse increase in linear and curvilinear structures (reticular pattern) was seen toward the center of the lung. Polygonal structures 1-2 cm in diameter were seen in seven patients with LS but not in healthy subjects. Fissures were thickened in nine patients. Selected 1.5-mm-thick CT sections are recommended through abnormal areas (seen at CT or on chest radiographs) or if these are normal at three levels (midapex, hilus, and 3 cm above the diaphragm) when scanning patients with tumors known to cause LS. 相似文献