全文获取类型
收费全文 | 256036篇 |
免费 | 13447篇 |
国内免费 | 2246篇 |
专业分类
耳鼻咽喉 | 3262篇 |
儿科学 | 7583篇 |
妇产科学 | 5050篇 |
基础医学 | 36462篇 |
口腔科学 | 5763篇 |
临床医学 | 21466篇 |
内科学 | 55304篇 |
皮肤病学 | 6495篇 |
神经病学 | 22023篇 |
特种医学 | 8040篇 |
外国民族医学 | 116篇 |
外科学 | 31419篇 |
综合类 | 4407篇 |
现状与发展 | 6篇 |
一般理论 | 64篇 |
预防医学 | 22635篇 |
眼科学 | 5095篇 |
药学 | 18766篇 |
13篇 | |
中国医学 | 1692篇 |
肿瘤学 | 16068篇 |
出版年
2023年 | 1548篇 |
2022年 | 1618篇 |
2021年 | 4430篇 |
2020年 | 2836篇 |
2019年 | 4523篇 |
2018年 | 8189篇 |
2017年 | 5494篇 |
2016年 | 5497篇 |
2015年 | 6378篇 |
2014年 | 6904篇 |
2013年 | 10174篇 |
2012年 | 17545篇 |
2011年 | 17585篇 |
2010年 | 8934篇 |
2009年 | 6754篇 |
2008年 | 14866篇 |
2007年 | 15827篇 |
2006年 | 14621篇 |
2005年 | 14623篇 |
2004年 | 13229篇 |
2003年 | 12140篇 |
2002年 | 11445篇 |
2001年 | 6626篇 |
2000年 | 6836篇 |
1999年 | 6184篇 |
1998年 | 1418篇 |
1997年 | 1273篇 |
1996年 | 1141篇 |
1995年 | 1033篇 |
1994年 | 881篇 |
1992年 | 3467篇 |
1991年 | 3102篇 |
1990年 | 2942篇 |
1989年 | 2726篇 |
1988年 | 2556篇 |
1987年 | 2383篇 |
1986年 | 2221篇 |
1985年 | 2040篇 |
1984年 | 1451篇 |
1983年 | 1243篇 |
1979年 | 1221篇 |
1978年 | 860篇 |
1977年 | 811篇 |
1975年 | 816篇 |
1974年 | 987篇 |
1973年 | 997篇 |
1972年 | 936篇 |
1971年 | 922篇 |
1970年 | 863篇 |
1969年 | 905篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The major benefit of antenatal ultrasonography is to allow early diagnosis of urinary tract malformations before postnatal infection worsens the prognosis. In the majority of cases, there is a unilateral and moderate dilatation requiring a check-up only during the second week of life; treatment subsequently depends on the etiology of the uropathy and the consequences on the kidney. Unilateral severe dilatations and bilateral, but moderate, dilatations must be managed immediately after birth in a pediatric surgical center. In the rare cases of severe bilateral obstructive uropathy, in utero decompression by catheterisation or surgery is now considered to be uselessly invasive, considering that renal dysplasia is already present when the malformation is detected. 相似文献
992.
I A Cotgreave P Moldéus R Brattsand A Hallberg C M Andersson L Engman 《Biochemical pharmacology》1992,43(4):793-802
Here we describe a new class of organoselenium compounds possessing glutathione peroxidase-like activity. The parent compound, alpha-(phenylselenenyl)acetophenone (PSAP), increased the rate of reaction of glutathione with H2O2, tert-butylhydroperoxide, cumene hydroperoxide, linoleic acid hydroperoxide and dilinoleyl lecithin hydroperoxide by 7.0, 25.1, 34.1, 19.1 and 8.4-fold, respectively, as assessed by the oxidized glutathione (GSSG) reductase enzyme assay. Direct assay of the removal of hydrogen peroxide and glutathione from reaction mixtures confirmed the peroxidase-like activities of these selenoorganic compounds, but indicate that the conventional coupled GSSG reductase assay may be unsuitable for the assessment of the catalytic capacity of PSAP and Ebselen. One possible mechanism of catalysis by PSAP involves an initial oxidation at selenium. Thiol may then react with the selenoxide to yield a selenium (II) compound, H2O and a disulfide. Compounds derived from PSAP may provide potential selenium-based anti-inflammatory agents. 相似文献
993.
Thirty-four patients having chronic idiopathic headaches participated in a long-term study comparing autogenic relaxation training alone (REL) with combinations of relaxation and electromyographic biofeedback (REL + EMG) or relaxation and temperature biofeedback (REL + TEMP). Assignment to treatment conditions was balanced on demographics and clinical characteristics, as well as headache classification according to muscle contraction or vascular headache symptomatology. The results indicate that REL + TEMP produced no additional improvements over REL following the 8-week treatment program, or at 6-month, or 12-month follow-up. However, REL + EMG produced significantly greater reductions in headache activity measures than the REL and REL + TEMP conditions at all post-treatment time points. Headache activity continued to improve over the follow-up period independent of treatment condition. These data indicate that EMG biofeedback augments long-term clinical improvements in headache patients who undergo autogenic relaxation training. 相似文献
994.
Xiaomei Zhou Jianren Gu Yuanqing Cheng Huiqiu Jiang Lianfang Qian Guowei Xu Shafritz David 《中国癌症研究》1992,4(3):10-14
This is first report about the simultaneous over-expression of both Insulin-like growth factor (IGF-II) and its receptor (IGF-II
R) at mRNA level in human primary hepatic Cancer (PHC). In 10 PHC samples from China, IGF-II and IGF-II R were both over-expressed,
whereas only a background signal was detected in normal liver. In 5 pairs of PHC and its non-tumorous adjacent liver tissues
from South Africa, IGF-II and IGF-II R were also over-expressed in PHC. mRNA expression of IGF-II in all 5 cases and IGF-II
R in 4 of 5 cases were higher in cancer than non-tumorous adjacent liver tissues. These results strongly implicate that an
autocrine and/or paracrine mechanism might be involved in formation and progression of PHC. 相似文献
995.
A tissue equivalent phantom was used in the study and absored x-ray doses.It measuring for some important organs of head and neck by four routive sialography methods (panoramic conventional x-ray radioagraphy,tomography,fluoroscope,CT) and also the X-ray absorbed doses of thyroid and len when lead containing loop and spectacles of head containing glass were used for prevention.All the data were processed statistically and a compartive study of absorbed x-ray doses of four sialography methods:Doses of submandibular gland were higher in CT,tomography and fluoroscope among them,CT was the highest indicating that it was superior to other methods for accurately locating that it was superior to other methods for accurately locating the within-gland tumor.Fluoroscope will be use more frequently in clinic,because it can observe the living gland panoramic and normal radiography can be used routinely because they had the minimum doses in measured organs.2.The absorbed x-ray doses of len and thyroid decreased by 93%-% when prevention was taken in CT or fluoroscope,65%-85% doses was decreased in normal radiography or panoramic with prevention. 相似文献
996.
R Esturau P Iturralde S Férez O Galván J Rosado G Pérez J A González Hermosillo 《Archivos del Instituto de Cardiología de México》1991,61(3):205-210
From June 1988 to June 1990 we studied fifty patients who had implantation of a pacemaker. (31 females and 19 males). All of them underwent stress test with Bruce's protocol. Patients were divided in two groups; pacemaker-independent (PI) and pacemaker-dependent (PD). Over 50% of the patients inhibited the pacemaker with their own rhythm, most of them had sinus dysfunction. Complete A-V block was predominant in PD. The group of PI achieved more mets and had more oxygen consumption. Blood pressure response was similar in both groups. 相似文献
997.
The variability of blood pressure measured by oscillometry and the validity of this technique were studied in premature infants. Thirty premature babies whose postnatal age was six days or more had their blood pressure measured 11 times over a twenty-minute period for three consecutive days. Movements were found to have a very substantial influence on results that could not be reliably compared with values obtained invasively. No consistent pattern of variations of oscillometric results obtained during the eleven measurements of use for recommending a specific measurement time was found. Diastolic blood pressure fell gradually over the three-day study period. The most reliable of the eleven daily values was the lowest value for which good correlations were found between the three study days; this lowest value was not influenced by neonatal or postnatal factors. 相似文献
998.
We report the identification of a new frameshift mutation (936delTA) in exon 6b of the CFTR gene. In the screening of 486 unrelated Spanish CF patients we found a patient homozygous for 936delTA (with consanguineous parents) and a patient heterozygous for delta F508 and 936delTA. Genotype-phenotype correlation studies showed that 936delTA is associated with pancreatic insufficiency and chronic pulmonary colonisation. 相似文献
999.
Twelve young adults (age 21-25 years) and twelve older adults (age 57-65 years) performed a visual discrimination task (parallel lines) in which the following factors were manipulated: the difference in the length of the lines (3% and 9%), signal exposure duration (150, 750, and 2000 ms), and presentation modality (simultaneous and successive). The effect of repeating the task over three blocks was also controlled. Reaction time, sensitivity (d'), the decision criterion (beta), and the level of confidence the subjects had in their responses were measured and analyzed. The reaction time of the older subjects was longer than for younger ones. The difference remained constant across conditions. Signal detection analysis indicated that the ability to discriminate, as measured by d', was the same, on the whole, in the two age groups, but the sensitivity of the older was more affected by signal exposure duration than that of their younger counterparts. Contrary to what might have been expected, the older subjects used a more risky decision criterion than the younger subjects (preferring false alarms to omissions) and did not have significantly less confidence in their responses. Task repetition led to reduced reaction times and to a slightly higher level of confidence, but no age-related effects were found. The findings suggest that, in addition to a perceptual compensatory component, the longer reaction times of the older subjects include a decision-making component not necessary for their level of discrimination accuracy. The outcome of a lower criterion in the older group supports other findings according to which a more conservative decision strategy is not a general, systematic feature of the aged. 相似文献
1000.
M Nehéz G W Fischer H Scheufler R Schmidt T Sipos I Dési 《Ecotoxicology and environmental safety》1992,24(1):13-16
The organophosphorus herbicide buminafos (O,O-dibutyl-(1-butylaminocyclohexyl)-phosphonate) was tested for its acute toxic, cytogenetic, and embryotoxic activity on different strains of mice. The oral LD50 value for male NMRI mice was determined to be 3500 mg/kg. Single oral doses of 175, 1000, and 2000 mg/kg did not cause any significant enhancement in the percentage of chromosome aberrations in bone marrow cells of male NMRI mice. After oral administration of 500 and 1000 mg/kg buminafos to pregnant Halle:DBA and Halle:AB mice at Days 6-15 of gestation no embryotoxic effects were observed. The cytogenetic inactivity of buminafos in the bone marrow chromosome assay corresponds to negative findings in other mutagenicity tests. 相似文献