全文获取类型
收费全文 | 33157篇 |
免费 | 2118篇 |
国内免费 | 208篇 |
专业分类
耳鼻咽喉 | 491篇 |
儿科学 | 843篇 |
妇产科学 | 376篇 |
基础医学 | 4161篇 |
口腔科学 | 489篇 |
临床医学 | 3364篇 |
内科学 | 7716篇 |
皮肤病学 | 247篇 |
神经病学 | 3270篇 |
特种医学 | 1692篇 |
外国民族医学 | 1篇 |
外科学 | 5354篇 |
综合类 | 324篇 |
一般理论 | 72篇 |
预防医学 | 2271篇 |
眼科学 | 428篇 |
药学 | 2019篇 |
中国医学 | 23篇 |
肿瘤学 | 2342篇 |
出版年
2023年 | 165篇 |
2022年 | 285篇 |
2021年 | 730篇 |
2020年 | 412篇 |
2019年 | 722篇 |
2018年 | 871篇 |
2017年 | 590篇 |
2016年 | 693篇 |
2015年 | 795篇 |
2014年 | 1143篇 |
2013年 | 1465篇 |
2012年 | 2347篇 |
2011年 | 2415篇 |
2010年 | 1424篇 |
2009年 | 1175篇 |
2008年 | 2166篇 |
2007年 | 2297篇 |
2006年 | 2174篇 |
2005年 | 2199篇 |
2004年 | 1936篇 |
2003年 | 1851篇 |
2002年 | 1794篇 |
2001年 | 320篇 |
2000年 | 261篇 |
1999年 | 326篇 |
1998年 | 447篇 |
1997年 | 382篇 |
1996年 | 342篇 |
1995年 | 307篇 |
1994年 | 261篇 |
1993年 | 249篇 |
1992年 | 190篇 |
1991年 | 217篇 |
1990年 | 190篇 |
1989年 | 186篇 |
1988年 | 162篇 |
1987年 | 173篇 |
1986年 | 144篇 |
1985年 | 169篇 |
1984年 | 176篇 |
1983年 | 137篇 |
1982年 | 163篇 |
1981年 | 143篇 |
1980年 | 126篇 |
1979年 | 75篇 |
1978年 | 82篇 |
1977年 | 74篇 |
1976年 | 70篇 |
1975年 | 48篇 |
1974年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Gregory Carey 《Behavior genetics》1991,21(5):433-444
The evolutionary implications of the path-analysis model most often used in human behavior genetics are examined. With directional selection, a model of pure vertical environmental transmission does not respond in a fully adaptive fashion. Unless the coefficients of transmission are exactly 0.50, the population mean will not equilibrate at the selective optimum over time. If there is both genetic and vertical environmental transmission, then the population mean can equilibrate at the selective optimum. In the presence of genetic transmission, vertical environmental transmission increases population fitness and has a strong effect on the rapid movement of the mean toward the selective optimum. This raises the intriguing paradox of why empirical evidence suggests that vertical environmental transmission is usually small when it possesses such important fitness properties.This work was supported in part by Grant DA05131 from the National Institute on Drug Abuse. 相似文献
82.
83.
Zhenfeng Xu Dajoie R Croslan Adalynn E Harris Gregory D Ford Byron D Ford 《Journal of cerebral blood flow and metabolism》2006,26(4):527-535
We have previously shown that neuregulin-1 (NRG-1) protects neurons from ischemic brain injury if administered before focal stroke. Here, we examined the therapeutic window and functional recovery after NRG-1 treatment in rats subjected to 90 mins of middle cerebral artery occlusion (MCAO) and 24 h of reperfusion. Neuregulin-1 (2.5 ng/kg bolus, 1.25 ng/kg/min infusion) reduced infarct volume by 89.2%+/-41.9% (mean+/-s.d.; n=8; P<0.01) if administered immediately after the onset of reperfusion. Neuroprotection was also evident if NRG-1 was administered 4 h (66.4%+/-52.6%; n=7; P<0.01) and 12 h (57.0%+/-20.8%; n=8; P<0.01) after reperfusion. Neuregulin-1 administration also resulted in a significant improvement of functional neurologic outcome compared with vehicle-treated animals (32.1%+/-5.7%; n=9; P<0.01). The neuroprotective effect of the single administration of NRG-1 was seen as long as 2 weeks after treatment. Neurons labeled with the neurodegeneration marker dye Fluoro-JadeB were observed after MCAO in the cortex, but the numbers were significantly reduced after NRG-1 treatment. These results indicate that NRG-1 is a potent neuroprotective compound with an extended therapeutic window that has practical therapeutic potential in treating individuals after ischemic brain injury. 相似文献
84.
Pernes JM; Vitoux JF; Brenoit P; Raynaud A; Parola JL; Roth JP; Angel CY; Fiessinger JN; Roncato M; Gaux JC 《Radiology》1986,158(2):481-485
Thirty-five patients hospitalized for recent angiographically documented arterial occlusion in the legs (27 femoropopliteal arteries and eight grafts) benefited from local fibrinolytic therapy delivered at the site of the occlusion with a 4- or 5-F catheter. This therapy combined a continuous urokinase (UK) infusion of 1,000 U/kg/hour and a lysyl plasminogen (LYS-PLG) infusion of 15 microkatals every 30 minutes. Angiographically confirmed lysis was obtained in 85% of the cases. Only 3% of the patients had major and 6% had minor groin hematomas. Only two patients had concentrations of fibrinogen as low as 100 mg/dl. Intravascular infusion of UK-LYS-PLG is as effective as streptokinase. Its excellent tolerance makes it a good alternative in the treatment of acute ischemia in the lower limbs. 相似文献
85.
The purpose of this study was to investigate the histogenesis of experimental tumors in the rat esophagus. Thirty rats received 0.0015% N-methyl-N-amylnitrosamine (MNAN) in the drinking water for 12 weeks. Another 30 rats received tap water. All rats then received tap water until sacrifice. Rats from each group were sacrificed immediately after MNAN administration, four weeks after, and eight weeks after. One hour before sacrifice, [3H]TdR was injected by tail vein to label proliferating cells. The entire esophagus and stomach were removed and processed for light and electron microscopy and autoradiography. The overall frequency of esophageal tumors after MNAN was 83% and did not differ significantly among the three experimental groups. Tumors were primarily papillomas and squamous cell carcinomas and occurred with equal frequency in the upper, middle, and lower thirds of the esophagus. No tumors were found in the squamous-lined forestomach. Electron microscopy revealed abundant tonofilaments, free ribosomes, and mitochondria accompanied by vacuoles. By autoradiography, esophageal epithelial proliferation was markedly stimulated in nontumorous mucosa from all three experimental groups. We conclude that MNAN ingestion for 12 weeks reliably produces papillomas and squamous cell carcinomas throughout the rat esophagus, but not in the squamouslined forestomach, and that MNAN stimulated marked epithelial proliferation which is accompanied by thickening of the epithelium in nontumorus esophageal mucosa. 相似文献
86.
Theresa B Haddy Revonda B Mosher Patricia A Dinndorf Gregory H Reaman 《The Journal of adolescent health》2004,34(4):324-329
PURPOSE: To estimate the incidence and types of second neoplasms in survivors of childhood and adolescent cancer, as well as the characteristics of those who developed second neoplasms. METHODS: Survivors who were under age 21 years at initial diagnosis, off therapy, and in remission for 2 years are referred to the Long Term Survivors' Clinic (LTSC) at Children's National Medical Center (CNMC). This review includes patients entered in the clinic database from January 1, 1997 to August 30, 2002. RESULTS: Twenty-three (2.3%) of 987 childhood cancer survivors followed in the LTSC had 26 (2.6%) second and third neoplasms. The mean age was 6.7 years at initial diagnosis, 20.3 years at diagnosis of the second neoplasm, and 20.5 years at diagnosis of the third neoplasm. Of 10 female and 13 male patients, 15 were white, six black, one Hispanic, and one Asian. All but two of the patients received radiation. Nineteen neoplasms, including seven thyroid carcinomas, six central nervous system tumors (three meningiomas), three basal cell carcinomas, two breast cancers, and one soft tissue sarcoma, occurred at sites within or contiguous to radiation sites. Five patients died, but the majority of neoplasms were treatable and most patients had good outcomes. CONCLUSION: Indefinite follow-up in a long-term survivors' clinic is indicated for adolescent and adult survivors of childhood cancer, with routine examination and screening for recurrence of the initial cancer as well as late effects, including second neoplasms. 相似文献
87.
Frank P MacMaster Aileen Russell Yousha Mirza Matcheri S Keshavan S Preeya Banerjee Rashmi Bhandari Courtney Boyd Michelle Lynch Michelle Rose Jennifer Ivey Gregory J Moore David R Rosenberg 《Neuropsychopharmacology》2006,59(3):252-257
BACKGROUND: Abnormalities in the limbic-hypothalamic-pituitary-adrenal (LHPA) axis have been implicated in the pathogenesis of obsessive-compulsive disorder (OCD). To our knowledge, however, no prior study has measured pituitary gland volume in OCD. METHODS: Volumetric magnetic resonance imaging studies were conducted in 31 psychotropic drug-na?ve children (10 boys, 21 girls) aged 8-17 years and 31 case-matched healthy comparison subjects. RESULTS: Pituitary volume was significantly smaller in patients with OCD as compared with healthy control subjects (11% smaller). Smaller pituitary volume in patients with OCD was associated with increased compulsive but not obsessive symptom severity. Boys with OCD had smaller pituitary gland volumes compared with control boys (20% smaller). No significant differences in pituitary volume were observed between girls with OCD and control girls. Boys with OCD had significantly smaller pituitary volumes than girls with OCD (31% smaller), whereas control boys also had smaller pituitary gland volumes compared with control girls (21% smaller). CONCLUSIONS: These findings provide new evidence of reduced pituitary volume in pediatric OCD that seems to be more prominent in male patients. The observed alterations in pituitary volume are consistent with neuroendocrine studies that have reported abnormalities in the LHPA axis in OCD. 相似文献
88.
Effect of Multiple Freeze-Thaw Cycles on Detection of Measles, Mumps, and Rubella Virus Antibodies 下载免费PDF全文
Norman A. Pinsky Jeanne M. Huddleston Robert M. Jacobson Peter C. Wollan Gregory A. Poland 《Clinical and Vaccine Immunology : CVI》2003,10(1):19-21
We investigated the effect of multiple freeze-thaw cycles on mumps, measles, and rubella virus serum antibody levels with whole-virus immunoglobulin G enzyme-linked immunoassays. Fresh serum samples from nine healthy adult volunteers were divided into six sets of five aliquots each. Samples were taken through a total of 10 freeze-thaw cycles and stored at 4°C until assayed. Each assay measurement was done in replicates of five, and the mean value was reported. After completing 10 freeze-thaw cycles, we found no clinically or statistically significant effect on measured antibody levels and found no discernible detrimental effect on the ability to measure these antibodies by enzyme-linked immunoassays. 相似文献
89.
90.