全文获取类型
收费全文 | 154073篇 |
免费 | 12633篇 |
国内免费 | 5993篇 |
专业分类
耳鼻咽喉 | 1975篇 |
儿科学 | 2070篇 |
妇产科学 | 2485篇 |
基础医学 | 22056篇 |
口腔科学 | 2929篇 |
临床医学 | 17417篇 |
内科学 | 26367篇 |
皮肤病学 | 3557篇 |
神经病学 | 10583篇 |
特种医学 | 7209篇 |
外国民族医学 | 54篇 |
外科学 | 17415篇 |
综合类 | 11409篇 |
现状与发展 | 22篇 |
一般理论 | 41篇 |
预防医学 | 9616篇 |
眼科学 | 4656篇 |
药学 | 14870篇 |
67篇 | |
中国医学 | 4831篇 |
肿瘤学 | 13070篇 |
出版年
2024年 | 301篇 |
2023年 | 1673篇 |
2022年 | 4483篇 |
2021年 | 6213篇 |
2020年 | 4103篇 |
2019年 | 4459篇 |
2018年 | 4958篇 |
2017年 | 4012篇 |
2016年 | 4774篇 |
2015年 | 6578篇 |
2014年 | 7939篇 |
2013年 | 8027篇 |
2012年 | 11803篇 |
2011年 | 12070篇 |
2010年 | 7268篇 |
2009年 | 5886篇 |
2008年 | 8278篇 |
2007年 | 8002篇 |
2006年 | 7737篇 |
2005年 | 7345篇 |
2004年 | 5551篇 |
2003年 | 4983篇 |
2002年 | 4311篇 |
2001年 | 3509篇 |
2000年 | 3395篇 |
1999年 | 3343篇 |
1998年 | 1834篇 |
1997年 | 1709篇 |
1996年 | 1341篇 |
1995年 | 1251篇 |
1994年 | 1081篇 |
1993年 | 802篇 |
1992年 | 1320篇 |
1991年 | 1255篇 |
1990年 | 1159篇 |
1989年 | 1117篇 |
1988年 | 1062篇 |
1987年 | 975篇 |
1986年 | 828篇 |
1985年 | 765篇 |
1984年 | 562篇 |
1983年 | 448篇 |
1982年 | 308篇 |
1981年 | 305篇 |
1980年 | 240篇 |
1979年 | 381篇 |
1978年 | 298篇 |
1977年 | 216篇 |
1974年 | 244篇 |
1973年 | 249篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
在28例成人标本上经骼骨钻孔和非髂骨钻孔法做经皮穿刺L_5S_1椎间盘后1/3,分层解剖观测,探针依次经过皮肤,肌肉,纤维环至髓核;并观察针与临近最下腰动脉脊支。股神经,闭孔神经和腰骶干的解剖关系。实验表明:遵循操作规则,使用锥形扩张器,用上述两种方法穿刺L_5S_1椎间盘后1/3都是安全,可行的。 相似文献
72.
Dopamine differentially regulates dynorphin, substance P, and enkephalin expression in striatal neurons: in situ hybridization histochemical analysis. 总被引:14,自引:0,他引:14
Dopamine regulation of the levels of dynorphin, enkephalin, and substance P messenger RNAs in rat striatal neurons was analyzed with in situ hybridization histochemistry (ISHH). Relative levels of peptide mRNA expression in the patch and matrix compartments of the dorsolateral striatum were compared among control rats, rats treated for 10 d with apomorphine, rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal dopaminergic system, and rats with nigrostriatal dopaminergic lesions followed 2 weeks later by 10 d of apomorphine treatment. Image analysis of ISHH labeling demonstrated that the number of neurons expressing each peptide mRNA remained constant, whereas the relative level of peptide mRNA per neuron changed significantly, depending on the experimental treatment. Dynorphin mRNA expression increased following chronic apomorphine treatment: striatal patch neurons increased to an average of 100% above control values, whereas striatal matrix neurons showed only a 25% increase. Dynorphin mRNA expression decreased following 6-OHDA lesions: patch neurons showed an average 75% reduction in expression, whereas matrix neurons showed no significant change. In animals with 6-OHDA lesions followed by apomorphine treatment, both patch and matrix neurons showed an average increase in dynorphin expression of 300% above control levels. Changes in dynorphin mRNA levels with these treatments were matched by qualitative changes in dynorphin immunoreactivity both in the striatum and in striatonigral terminals in the substantia nigra. Neither substance P nor enkephalin mRNA levels showed a significant difference between the striatal patch and matrix compartments in any experimental condition (in the dorsolateral striatum). Substance P mRNA expression was increased an average of 50% after 10 d of apomorphine treatment and showed an average decrease of 75% following 6-OHDA lesions of the mesostriatal system. There was no significant change in the expression of substance P mRNA in striatal neurons compared to control values in rats with combined 6-OHDA lesion and apomorphine treatment. Enkephalin mRNA expression was not significantly altered by chronic apomorphine treatment but showed an average increase per cell of some 130% above control levels following 6-OHDA-induced lesions of the mesostriatal system. In animals with a 6-OHDA lesion and apomorphine treatment, enkephalin mRNA was also elevated but not significantly above the levels produced by the lesions alone. These data show that the expression of dynorphin, enkephalin, and substance P is differentially regulated by the mesostriatal dopaminergic system and, further, suggests that the mechanisms by which this regulation occurs may be different for the 3 peptide families. 相似文献
73.
74.
Magnetic resonance imaging confirmation of resolution of periodontoid pannus formation following C1/C2 posterior transarticular screw fixation. 总被引:3,自引:0,他引:3
Chronic odontoid fractures are considered unstable spinal lesions. Chronic instability in this region leads to the development of an inflammatory pannus, which can progress resulting in spinal cord compression radiographically and a myelopathy syndrome clinically. In this report we document three cases of reversal of pannus after C1/C2 transarticular screw fixation of an unstable odontoid fracture. Three patients were identified with chronic odontoid fractures and spinal cord compression due to periodontoid pannus formation. All patients presented with a progressive myelopathy syndrome. All patients underwent preoperative and postoperative magnetic resonance imaging (MRI) of the craniovertebral junction. C1/C2 transarticular screw fixation was performed for stabilization of C1/C2. Postoperatively there were no complications. Postoperative MRI at 6 months demonstrated resolution of the ventral pannus. Moreover, all patients exhibited improvement of preoperative neurological deficits. MRI is the imaging technique of choice for diagnosis and follow-up of patients with chronic odontoid fractures and ventral pannus. C1/C2 transarticular screw fixation provides a viable method for spinal stabilization in this region. In addition, stabilization can result in resolution of inflammatory pannus formation secondary to instability of the C1/C2 articulation. 相似文献
75.
Spontaneous neuronal hyperactivity in the medial and intralaminar thalamic nuclei of patients with deafferentation pain 总被引:6,自引:0,他引:6
Electrical activity was recorded from single cells in the thalamus of 10 patients with chronic pain associated with deafferentation. Under local anesthesia, these patients underwent either electrode implantation or thalamotomy for treatment of their pain. In eight of the 10 patients, single units were identified as discharging spontaneously in high-frequency, often rhythmic, bursts. The discharges were of two types: short bursts comprised of two to six spikes with a burst frequency of one to four per second; and long trains of 30 to 80 spikes of similar frequency. Reconstruction of electrode trajectories indicated that recordings were made from the region corresponding to the lateral aspect of the mediodorsal thalamic nucleus, the central lateral nucleus, a small part of the central median nucleus, and the parafascicular nucleus. In the eight patients in whom spontaneous neuronal burst activity was exhibited, it was impossible to study activity evoked by natural cutaneous stimulation due to the continuous spontaneous neuronal discharges. Both animal and human studies have suggested that pain related to deafferentation is accompanied by spontaneous hyperactivity in the dorsal horn of the spinal cord and in the ventral posterior thalamic nuclei. The authors present evidence of spontaneous neuronal hyperactivity in the intralaminar thalamic nuclei of patients with pain related to deafferentation. The findings suggest that spontaneous neuronal discharge in patients with pain related to deafferentation is more widespread in the central nervous system than has been previously appreciated. The results have important implications for the surgical treatment of chronic pain. 相似文献
76.
目的:探讨EB病毒感染与人大肠癌发生的关系。方法:用原位分子杂交法对130例人大肠癌标本中EB病毒小分子RNA片段进行检测。结果:130例标本中有6例(4.48%)癌组织呈阳性反应,其中4例为男性,4例有明显淋巴细胞浸润。结论:EB病毒感染可能与我国部分大肠腺癌的发生有关,肿瘤细胞间质中大量淋巴细胞浸润可能是EB病毒感染的重要病理学特征。 相似文献
77.
目的:观察肝癌形成过程中明胶酶表达(蛋白及mRNA水平)的动态变化,探索明胶酶在肝癌生长浸润中的作用。方法:应用免疫组化法、明胶酶谱法和RT-PCR法对大鼠肝癌形成过程中各期明胶酶表达情况进行观察,并与正常对照组进行比较分析。结果:正常肝组织及肝硬化组织内明胶酶有表达,肝癌形成后主要在癌细胞内表达;明胶酶原在正常肝组织中有低表达,诱癌过程中呈持续增高趋势;明胶酶-2mRNA与其酶蛋白表达趋向一致。结论:在肝癌形成过程中明胶酶转录和翻译水平均呈持续增高趋势。 相似文献
78.
Changes in outcome with sphincter preserving surgery for rectal cancer in Korea, 1991-2000. 总被引:3,自引:0,他引:3
S-B Lim S C Heo M R Lee S-B Kang Y J Park K J Park H S Choi S-Y Jeong J-G Park 《European journal of surgical oncology》2005,31(3):242-249
AIM: To report the clinical and oncological data of patients operated on for rectal cancers 3-5 cm from the AV over a 10 year period, including the Sphincter preservation (SP) rate. METHODS: We reviewed medical records of 304 patients with rectal cancers 3-5 cm from the AV who underwent surgical resection from January 1991 through December 2000. The 10 years were divided into three periods based on the introduction of new surgical techniques, specifically, ultralow anterior resection (ULAR) with double stapling in March 1994 and ULAR with coloanal anastomosis in April 1997. The rates of SP, complications and patient survival during these periods were compared. RESULTS: The SP rate increased significantly over the 10 years, from 16.4% in period I (January 1991-February 1994), to 53.0% in period II (March 1994-March 1997), to 86.5% in period III (April 1997-December 2000) (p<0.001). Over time, the age of the patients increased (p=0.004), the length of the distal resection margin became shorter (p=0.005), and the rate of lymph node metastasis increased (p=0.016). The factors significantly influencing SP were the period (p<0.001) and the distance from the AV (p<0.001). Over time, morbidity did not increase, and overall and disease free survival rates did not decrease. In contrast, the overall survival of N2 cases significantly increased over time (p=0.0492). CONCLUSION: Over 10 years, the SP rate in rectal cancers 3-5 cm from the AV was significantly increased by the introduction of the double stapling and coloanal anastomosis techniques. These surgical methods, however, had no effect on morbidity, disease free survival and overall survival rates. 相似文献
79.
80.
A method for measuring flow based on the shifting of the rephasing pulse following slice selection in partial saturation is described. The technique is based on a partial saturation sequence and retains much of the high signal which is a feature of the use of this sequence. Images obtained while encoding for the flow signal compated with those when not encoding appear very similar. 相似文献