全文获取类型
收费全文 | 8750篇 |
免费 | 548篇 |
国内免费 | 92篇 |
专业分类
耳鼻咽喉 | 69篇 |
儿科学 | 360篇 |
妇产科学 | 219篇 |
基础医学 | 1271篇 |
口腔科学 | 223篇 |
临床医学 | 922篇 |
内科学 | 1715篇 |
皮肤病学 | 109篇 |
神经病学 | 871篇 |
特种医学 | 604篇 |
外科学 | 1259篇 |
综合类 | 80篇 |
一般理论 | 2篇 |
预防医学 | 594篇 |
眼科学 | 121篇 |
药学 | 467篇 |
1篇 | |
中国医学 | 27篇 |
肿瘤学 | 476篇 |
出版年
2022年 | 71篇 |
2021年 | 140篇 |
2020年 | 83篇 |
2019年 | 129篇 |
2018年 | 146篇 |
2017年 | 100篇 |
2016年 | 113篇 |
2015年 | 133篇 |
2014年 | 192篇 |
2013年 | 283篇 |
2012年 | 365篇 |
2011年 | 369篇 |
2010年 | 219篇 |
2009年 | 201篇 |
2008年 | 323篇 |
2007年 | 354篇 |
2006年 | 363篇 |
2005年 | 366篇 |
2004年 | 354篇 |
2003年 | 345篇 |
2002年 | 288篇 |
2001年 | 267篇 |
2000年 | 284篇 |
1999年 | 255篇 |
1998年 | 145篇 |
1997年 | 123篇 |
1996年 | 134篇 |
1995年 | 94篇 |
1994年 | 100篇 |
1993年 | 117篇 |
1992年 | 195篇 |
1991年 | 186篇 |
1990年 | 179篇 |
1989年 | 187篇 |
1988年 | 169篇 |
1987年 | 183篇 |
1986年 | 149篇 |
1985年 | 181篇 |
1984年 | 125篇 |
1983年 | 99篇 |
1982年 | 65篇 |
1981年 | 80篇 |
1979年 | 74篇 |
1978年 | 95篇 |
1977年 | 66篇 |
1975年 | 63篇 |
1974年 | 64篇 |
1973年 | 63篇 |
1972年 | 71篇 |
1971年 | 62篇 |
排序方式: 共有9390条查询结果,搜索用时 15 毫秒
91.
Acute ovarian torsion in children 总被引:11,自引:0,他引:11
BACKGROUND: Acute ovarian torsion (OT) is an uncommon cause of abdominal pain in children and is frequently confused with other conditions. METHODS: We reviewed the records (1983 to 1999) of all children treated for acute OT at our children's hospital. RESULTS: Mean child age (n = 51) was 12.5 +/- 0.3 years. Children presented with either right-sided (n = 29) or left-sided (n = 22) pain. Diagnosis of OT was confirmed preoperatively by ultrasound (73%) or computed tomography (CT) scan (10%) while nine children (17%) with right-sided pain underwent surgery for presumed appendicitis. Despite a relatively short time from diagnosis to surgery, all 51 children required salpingooophorectomy. Contralateral biopsy was performed in 29% and 57% had an appendectomy. Younger children more commonly had either a mature cystic teratoma or torsion with no underlying abnormality as an etiology compared with OT in older children that was more likely to result from either a follicular or corpus luteal cyst. Pathologic examination of the contralateral ovary and appendix was normal in all children who underwent biopsy and appendectomy. CONCLUSION: Ultrasonography with color doppler is helpful for differentiating acute OT from appendicitis. Although the twisted ovary can rarely be salvaged, the etiology is usually benign. Preoperative serum markers and contralateral ovary biopsy may be unnecessary. 相似文献
92.
93.
Brimacombe J Holyoake L Keller C Brimacombe N Scully M Barry J Talbutt P Sartain J McMahon P 《Anesthesiology》2000,93(1):26-31
BACKGROUND: There is controversy over (1) the relative incidence of sore throat between the face mask (FM) and laryngeal mask airway (LMA), (2) the efficacy of LMA intracuff pressure reduction as a mechanism for minimizing sore throat, and (3) the relative incidence of sore throat with the LMA between males and females. In a randomized double-blind study, the authors compared laryngopharyngeal, neck, and jaw discomfort with the FM and LMA at high and low cuff volumes in males and females. METHODS: Three hundred adult patients were randomly assigned to three equal-sized groups for airway management: (1) the FM, (2) the LMA with a fully inflated cuff (LMA-High), or (3) the LMA with a semi-inflated cuff (LMA-Low). Anesthesia was administered with propofol, nitrous oxide, oxygen, and isoflurane. In the FM group, a Guedel-type oropharyngeal airway and jaw thrust were used only if necessary. In the LMA groups, cuff inflation was achieved with either 15 or 30 ml for the size 4 (females) and 20 or 40 ml for the size 5 (males). The LMA was removed when the patient was awake. Patients were questioned 18-24 h postoperatively about surgical pain, sore throat, sore neck, sore jaw, dysphonia, and dysphagia, and about whether they were satisfied with their anesthetic. RESULTS: The incidence of sore throat was lower in the FM (8%) than the LMA-High (42%) and LMA-Low (20%) groups (both: P < or = 0.02). The incidence of sore neck was higher for the FM (14%) than the LMA-High group (6%; P = 0.05) but similar to the LMA-Low group (8%). The incidence of sore jaw was higher in the FM (11%) than the LMA-High (3%) and LMA-Low (3%) groups (both: P = 0. 02). There were no differences among groups for surgical pain or dysphonia. The incidence of dysphagia was lower in the FM (1%) than the LMA-High group (11%; P = 0.003), but similar to the LMA-Low group (1%). The incidence of sore throat and dysphagia was lower in the LMA-Low group than the LMA-High group for both males and females (all: P < or = 0.04). There were no differences in discomfort levels between males and females in any group. Two patients from the FM group and one from the LMA-High group were not satisfied with their anesthetic. These complaints were unrelated to postoperative morbidity. CONCLUSION: The LMA causes more sore throat and dysphagia but less jaw pain than the FM. Sore throat and dysphagia are more common with the LMA if the initial cuff volume is high. There are no differences in discomfort levels between males and females. However, these discomforts do not influence patient satisfaction after LMA or FM anesthesia. 相似文献
94.
95.
Biosynthesis of the ansamycin antibiotic ansatrienin (mycotrienin) by Streptomyces collinus 总被引:1,自引:0,他引:1
T S Wu J Duncan S W Tsao C J Chang P J Keller H G Floss 《Journal of natural products》1987,50(1):108-118
The biosynthesis of ansatrienin (mycotrienin) has been studied in radioactive and stable isotope feeding experiments with Streptomyces collinus Tü 1892. The m-C7N unit of the ansa ring is efficiently and specifically derived from 3-amino-5-hydroxybenzoic acid; shikimic acid is not incorporated into this part of the molecule but does label the cyclohexanecarboyxlic acid moiety, providing all seven of its carbon atoms. Incorporation of methionine confirms origin of the methoxy group by transmethylation. The D-alanine moiety is derived directly from D-alanine rather than L-alanine. The terminal steps in the conversion of shikimic acid into cyclohexanecarboyxlic acid seem to be sequential reduction of 2,5-dihydrobenzoic acid and cyclohexene-1-carboxylic acid as evidenced by feeding experiments and the detection of a new ansatrienin containing a 1-cyclohexene instead of the cyclohexane moiety. 相似文献
96.
P C Leppert S Y Yu S Keller J Cerreta I Mandl 《American journal of obstetrics and gynecology》1987,157(5):1134-1139
Incompetence of the uterine cervix is a syndrome of painless, progressive dilatation and effacement occurring between the sixteenth and twenty-fourth weeks of gestation that represents abnormal functioning. It may serve as a model to elucidate normal function. Because the incompetent cervix results in painless opening of this organ without uterine contraction before term gestation, it is considered one of the causes of midtrimester spontaneous abortion, habitual spontaneous abortion, and early preterm labor. Untreated, it leads to rapid expulsion and often death of the fetus. We used light microscopy to compare decreased elastic fibers in incompetent cervices with those of normal nonpregnant and pregnant cervices. Morphologic analysis of this difference was extended to biochemical quantification of elastin content in one patient with cervical incompetence. The decrease in elastin suggests that one function of cervical elastin may be to maintain a closed and undilated cervix throughout gestation. There may be a relationship between changes in cross-linked elastin and the incompetent cervix; further studies are therefore indicated. 相似文献
97.
98.
Journal of Molecular Medicine - Nach einer Übersicht über die Entdeckung des Coxsackievirus und die bisherigen Virusisolierungen in außerdeutschen Ländern wird über die... 相似文献
99.
100.
Ryan C. Higgins Kathleen L. Keller Jane C. Aruma Travis D. Masterson Shana Adise Nicole Fearnbach Wendy M. Stein Laural K. English Bari Fuchs Alaina L. Pearce 《Maternal & child nutrition》2022,18(3)
Longer exclusive breastfeeding duration has been associated with differences in neural development, better satiety responsiveness, and decreased risk for childhood obesity. Given hippocampus sensitivity to diet and potential role in the integration of satiety signals, hippocampus may play a role in these relationships. We conducted a secondary analysis of 149, 7–11‐year‐olds (73 males) who participated in one of five studies that assessed neural responses to food cues. Hippocampal grey matter volume was extracted from structural scans using CAT12, weight status was assessed using age‐ and sex‐adjusted body mass index (%BMIp85), and parents reported exclusive breastfeeding duration and satiety responsiveness (Children''s Eating Behaviour Questionnaire). Separate path models for left and right hippocampus tested: (1) the direct effect of exclusive breastfeeding on satiety responsiveness and its indirect effect through hippocampal grey matter volume; (2) the direct effect of hippocampal grey matter volume on %BMIp85 and its indirect effect through satiety responsiveness. %BMIp85 was adjusted for maternal education, yearly income, and premature birth while hippocampal grey matter volume was adjusted for total intercranial volume, age, and study from which data were extracted. Longer exclusive breastfeeding duration was associated with greater bilateral hippocampal grey matter volumes. In addition, better satiety responsiveness and greater left hippocampal grey matter volume were both associated with lower %BMIp85. However, hippocampal grey matter volumes were not associated with satiety responsiveness. Although no relationship was found between breastfeeding and child weight status, these results highlight the potential impact of exclusive breastfeeding duration on the hippocampal structure. 相似文献