全文获取类型
收费全文 | 22473篇 |
免费 | 1698篇 |
国内免费 | 43篇 |
专业分类
耳鼻咽喉 | 225篇 |
儿科学 | 909篇 |
妇产科学 | 588篇 |
基础医学 | 3037篇 |
口腔科学 | 656篇 |
临床医学 | 2571篇 |
内科学 | 4347篇 |
皮肤病学 | 314篇 |
神经病学 | 1808篇 |
特种医学 | 918篇 |
外科学 | 3065篇 |
综合类 | 376篇 |
一般理论 | 43篇 |
预防医学 | 2142篇 |
眼科学 | 346篇 |
药学 | 1399篇 |
1篇 | |
中国医学 | 16篇 |
肿瘤学 | 1453篇 |
出版年
2022年 | 141篇 |
2021年 | 329篇 |
2020年 | 228篇 |
2019年 | 363篇 |
2018年 | 396篇 |
2017年 | 327篇 |
2016年 | 332篇 |
2015年 | 420篇 |
2014年 | 578篇 |
2013年 | 759篇 |
2012年 | 1112篇 |
2011年 | 1206篇 |
2010年 | 651篇 |
2009年 | 551篇 |
2008年 | 1080篇 |
2007年 | 1178篇 |
2006年 | 1090篇 |
2005年 | 1079篇 |
2004年 | 949篇 |
2003年 | 941篇 |
2002年 | 809篇 |
2001年 | 636篇 |
2000年 | 626篇 |
1999年 | 523篇 |
1998年 | 250篇 |
1997年 | 214篇 |
1996年 | 218篇 |
1995年 | 221篇 |
1994年 | 199篇 |
1993年 | 181篇 |
1992年 | 471篇 |
1991年 | 455篇 |
1990年 | 435篇 |
1989年 | 431篇 |
1988年 | 397篇 |
1987年 | 355篇 |
1986年 | 307篇 |
1985年 | 383篇 |
1984年 | 292篇 |
1983年 | 261篇 |
1982年 | 161篇 |
1979年 | 211篇 |
1978年 | 183篇 |
1977年 | 156篇 |
1976年 | 152篇 |
1975年 | 159篇 |
1974年 | 158篇 |
1973年 | 197篇 |
1972年 | 159篇 |
1971年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Nelson T Yamagata Bruce L Miller Duncan McBride Linda Chang Francis Chiang Diana Nikas Diane Osborne Steven D Buchthal 《Journal of neuroimaging》1994,4(1):23-28
The chemical characteristics of 10 neoplastic and 11 infectious brain masses were studied by in vivo 1H magnetic resonance spectroscopy. In tumors, peak height ratios of n-acetyl-L-aspartate to choline were decreased compared to those in normal brain tissue and infectious masses (p < 0.02), but the ratios in normal brains and those with infections did not differ. N-acetyl-L-aspartate—to-creatine/phosphocreatine ratios were significantly lower in infectious masses and tumors compared to normal brain tissue (p = 0.003). However, in progressive multifocal leukoencephalopathy, N-acetyl-L-aspartate appeared relatively unchanged. Lactate was greater than choline in 9 of 11 brains with infection, 0 of 14 control brains, and 1 of 10 tumors. Lactate-to-choline ratios were significantly elevated in infectious masses compared with tumors (p < 0.01). 1H magnetic resonance spectroscopy is promising for the noninvasive diagnosis of focal brain masses. 相似文献
72.
73.
During a prospective evaluation of intravenous therapy with peripheral Teflon catheters in children, we found 30 episodes of phlebitis (10.4%). This rate is less than that reported in adults. Catheter colonization was not related to phlebitic episodes, and catheter-related infections did not occur. No patient's hospital course was prolonged because of phlebitis. Thirty percent of the episodes developed after the catheter was removed, and premonitory symptoms were not helpful in predicting the onset of phlebitis. Factors associated with an increased phlebitic risk were parenteral nutrition, administration of nafcillin sodium or aminoglycosides, and patient age. Parenteral nutrition prolonged the course of phlebitis. No factors hastened the onset of phlebitis. The duration of cannulation was not significantly related to phlebitis, suggesting that in some children the catheters can remain in place longer than 72 hours. 相似文献
74.
F R Nelson D Holloway A K Mohamed 《Journal of the American Mosquito Control Association》1986,2(3):296-299
In a laboratory study, the insect growth regulator, cyromazine, exerted a high level of biological activity on Aedes aegypti and Culex quinquefasciatus treated in the 4th larval instar. At 1.5 and 1.0 ppm this IGR produced 97 and 99% inhibition of emergence in adult Ae. aegypti, respectively. In Cx. quinquefasciatus, there was 99% inhibition at 1 ppm and complete inhibition at 1.5 ppm. The overall pupal mortality was higher than larval or adult stages of both species. This material induced different types of morphogenetic abnormalities in pupae and adults of the 2 species similar to those induced by other IGRs. However, most abnormalities were observed in the pupal stage. Adverse effects were not detected on the 4 mosquito predator species during the acute or posttreatment tests. 相似文献
75.
Heterotopic bone formation occurs in approximately 2% of severe burns. It occurs most frequently about the elbow and is not related to the location of the burn. Although bony encasement of the ulnar nerve is frequently found, signs and symptoms of ulnar nerve compression due to heterotopic bone have not been previously reported. Early anterior transposition of the nerve is recommended to prevent progressive neurologic loss if compressive symptoms are found in the face of developing heterotopic bone. 相似文献
76.
77.
78.
79.
J E Holden K Mori G A Dienel N F Cruz T Nelson L Sokoloff 《Journal of cerebral blood flow and metabolism》1991,11(2):171-182
The steady-state distribution volumes of glucose, 3-O-methylglucose, and 2-deoxyglucose (2DG) are known to change as the concentration of glucose in plasma ranges from hypo- to hyperglycemic values. Model estimates of the three distribution volumes were compared with distribution volume values experimentally measured in the brains of conscious rats as the concentration of glucose in plasma was varied from 2 to 28 mM. The dependence on plasma glucose concentration of the 2DG lumped constant, the factor that relates the phosphorylation rate of 2DG to the net rate of glucose utilization at unit specific radioactivity in the plasma, had been determined previously in separate series of experiments. The model was extended to incorporate this dependence of the lumped constant. In the model both the transport and the phosphorylation barriers were assumed to be single and saturable. The values of their respective half-saturation concentrations and the ratio of the two maximum velocities for glucose were assumed to be invariant over the entire range of plasma glucose concentration. Good agreement between measured and estimated values for the distribution volumes and the lumped constant was attained over the full range of plasma glucose concentration. The model estimates reflected the progressive transport limitation of the brain glucose content as plasma glucose levels were reduced to hypoglycemic values. The results also indicated that these changes should be evident in the time course of 2DG in brain following administration by bolus or continuous infusion, and thus that indexes of local lumped constant change could be derived from the time course data. 相似文献
80.
Mitochondrial function and mitochondrial DNA in a series of 64 patients suspected of having mitochondrial myopathy 总被引:1,自引:0,他引:1
C Marsac F Degoul G Bonne N Romero I Nelson M Fardeau D Fran?ois G Ponsot J P Harpey B Eymard 《Revue neurologique》1991,147(6-7):462-466
Biochemical results concerning 64 patients suspected of mitochondrial myopathies are presented. Four clinical groups were studied including 21 encephalomyopathies, 42 ocular myopathies, 8 isolated myopathies and 3 cardiomyopathies. In 26 cases, the coexistence of a normal mitochondrial DNA and a mutated mitochondrial DNA (heteroplasmy) was found (19 simple deletions, 4 multiple deletions and 3 punctual mutations) and all cases presented with ocular disorders (excepted 2 cases with MERRF). Furthermore, 1 complex I deficiency (1 ocular myopathy), 1 complex IV deficiency (1 adult encephalomyopathy type Leigh), 3 complexes I + IV deficiencies (2 cases with a cardiomyopathy and 1 familial MELAS) and 2 pyruvate (1 adult from of Leigh's encephalomyopathy) dehydrogenase deficiencies (clinically and genetically different) did not show evidence of mitochondrial DNA mutation. 相似文献