全文获取类型
收费全文 | 5183篇 |
免费 | 539篇 |
国内免费 | 120篇 |
专业分类
耳鼻咽喉 | 32篇 |
儿科学 | 157篇 |
妇产科学 | 80篇 |
基础医学 | 740篇 |
口腔科学 | 87篇 |
临床医学 | 707篇 |
内科学 | 1074篇 |
皮肤病学 | 61篇 |
神经病学 | 268篇 |
特种医学 | 459篇 |
外国民族医学 | 1篇 |
外科学 | 636篇 |
综合类 | 128篇 |
一般理论 | 1篇 |
预防医学 | 520篇 |
眼科学 | 51篇 |
药学 | 328篇 |
中国医学 | 1篇 |
肿瘤学 | 511篇 |
出版年
2021年 | 75篇 |
2020年 | 45篇 |
2019年 | 75篇 |
2018年 | 66篇 |
2017年 | 64篇 |
2016年 | 100篇 |
2015年 | 90篇 |
2014年 | 117篇 |
2013年 | 153篇 |
2012年 | 197篇 |
2011年 | 214篇 |
2010年 | 153篇 |
2009年 | 158篇 |
2008年 | 172篇 |
2007年 | 221篇 |
2006年 | 198篇 |
2005年 | 222篇 |
2004年 | 159篇 |
2003年 | 139篇 |
2002年 | 132篇 |
2001年 | 133篇 |
2000年 | 153篇 |
1999年 | 130篇 |
1998年 | 142篇 |
1997年 | 128篇 |
1996年 | 138篇 |
1995年 | 107篇 |
1994年 | 96篇 |
1993年 | 84篇 |
1992年 | 108篇 |
1991年 | 103篇 |
1990年 | 112篇 |
1989年 | 134篇 |
1988年 | 105篇 |
1987年 | 114篇 |
1986年 | 98篇 |
1985年 | 131篇 |
1984年 | 84篇 |
1983年 | 55篇 |
1982年 | 65篇 |
1981年 | 44篇 |
1980年 | 62篇 |
1979年 | 46篇 |
1978年 | 46篇 |
1977年 | 66篇 |
1976年 | 60篇 |
1972年 | 44篇 |
1971年 | 47篇 |
1970年 | 58篇 |
1968年 | 43篇 |
排序方式: 共有5842条查询结果,搜索用时 15 毫秒
101.
102.
为探讨体外循环(CPB)导致心脏植物神经系统(CAS)损伤的机理,了解温血心停跳液能否防止CPB后心率变异性(HRV)的降低,采用对照方法观察了温血心停跳液与冷晶体心停跳液对狗HRV的影响。结果显示:CPB后温血心停跳液组(WB组)和冷晶体心停跳液组(CC组)的全频谱(TP)、低频(LF)和高频(HF)均较术前明显降低(P<0.05),而且CC组比WB组降低更明显(P<0.05),但LF/HF在组内及组间均无明显变化(P>0.05)。CPB后24小时平均心率(MHR)明显增加(P<0.05),且CC组高于WB组(P<0.05)。本研究表明:采用温血心停跳液或冷晶体心停跳液的CPB不会干扰CAS平衡,但均能使HRV降低,温血心停跳液不能防止HRV损害。 相似文献
103.
BACKGROUND AND OBJECTIVE: Recent developments in fiber laser technology have introduced highly efficient, compact sources with high output beam quality. The first laser-tissue interaction studies with a high-power 2-microm fiber laser were conducted. STUDY DESIGN/MATERIALS AND METHODS: Chicken breast and porcine muscle tissue samples were subjected to continuous wave (cw) irradiation at 800-mW and 5-W output power levels, with spot sizes of approximately 150 microm. After laser irradiation, samples were inspected with an optical microscope and prepared for histologic processing. RESULTS: Evaluation of surface changes in tissue samples indicated an interaction similar in nature to those previously demonstrated with other cw lasers, but with photothermal ablation characteristics typical of strongly absorbed lasers operating in the infrared wavelength region. An ablation velocity of 0.27 mm.sec(-1) in porcine tissue was determined at 800-mW incident power. Histopathologic analysis demonstrated the formation of lesions with minimal damage at boundaries and no evidence of carbonization. CONCLUSIONS: Results indicate that this fiber laser has the potential to fulfill applications in the medical field. 相似文献
104.
BACKGROUND: Cigars have been heavily promoted in recent years. The nature and extent of the resultant increase in cigar smoking needs to be understood before the public health implications can be assessed. METHODS: Data are from population-based surveys conducted in California adults (> or = 18 years) in 1990 (n = 24,296) and 1996 (n = 24,266). Trends in current (every day or some days) cigar use are described for demographic subgroups and by cigarette smoking status. RESULTS: Current cigar use has doubled in California, from 2.5% in 1990 to 4.9% in 1996. In 1996, fewer than 5% of cigar smokers smoked cigars daily; essentially all of the increase was from nondaily use in those under 45 years of age of both genders, particularly in 18- to 24-year-olds. Among males, increased cigar use was observed in all racial/ethnic groups except Asians, and was observed in those with higher educational attainment and higher incomes. In both years, current and former cigarette smokers had higher rates of cigar use than never smokers, but the increase in current cigar smoking was observed regardless of cigarette smoking status. In 1996, daily cigar smokers were more likely to be former cigarette smokers than nondaily cigar smokers. CONCLUSION: If more people begin to smoke cigars daily, or if cigar use leads young people to initiate cigarette smoking or leads former cigarette smokers to relapse to cigarette smoking, the recent trends in cigar use may have public health implications. 相似文献
105.
106.
The palpation and enucleation of occult insulinomas (less than 15 mm) can be a difficult surgical problem even with good arteriographic localization. In the authors' limited experience, confirmation of arteriographic findings by pancreatic venous sampling provided little additional localizing information. However, if arteriography is negative or equivocal, venous sampling can indicate the segment of pancreas to be "blindly" resected if the adenoma is not palpable. Venous sampling may be misleading in polyendocrine syndromes because of the frequency of multiple adenomas and variable hormone production. 相似文献
107.
A procedure for control of variceal bleeding has been described which involves "devascularization" of the distal one third of the esophagus and upper one half of the stomach combined with a Nissen fundoplication performed through a left lateral thoracotomy and an incision in the left diaphragm. Transection of the truncal vagi is required to effectively de vascularize the distal esophagus and, thus, pyloromyotomy or pyloroplasty is added. Six patients who were moderately high risk candidates underwent this procedure for control for persistent hemorrhage; five of these patients were operated on within 48 hours of admission. There was one postoperative mortality. The five survivors have not rebled, and there has been no evidence of encephalopathy or progressive liver deterioration over a mean follow-up of thirteen months. 相似文献
108.
The development of a quality assurance program for a nuclear pharmacy service is described. The program was established to complement and test the extensive quality control procedures in the nuclear pharmacy. Based on current nuclear pharmacy standards of practice and government regulations, audits were developed and tested for a 12-month period. Results of these audits were closely analyzed for their relevance and impact on the service. These results showed that the standards for the established quality control program were being met. It was concluded that the quality assurance program was a useful and practical tool. 相似文献
109.
PURPOSE: Hepatocellular carcinoma (HCC) is generally considered as a sex hormone-dependent tumor, and hormonal therapy has been proposed as a strategy for the treatment of HCC. The aim of the study is to investigate the effect of megestrol acetate, a synthetic progesteronal agent, on growth of HepG2 cells in vitro and in vivo. EXPERIMENTAL DESIGN: Cell growth in vitro was assessed by a colormetric method, and cell growth in vivo was assessed by tumor volumetrics. RESULTS: Megestrol acetate was shown to inhibit the growth of HepG2 cells in vitro in dose- and time-dependent manners with an IC (50) of 260 microm (24-h incubation). The growth of HepG2 cell-transplanted tumors in nude mice was also inhibited by i.p. injection of megestrol acetate (10 mg/kg/day). The tumor volumes of the megestrol acetate-treated group regressed to 59% of controls by week 6 and to 41% of controls by week 13. Apoptosis following G(1) arrest was observed in megestrol acetate-treated cells and may be a mechanism through which megestrol acetate inhibits HepG2 cells. Megestrol acetate was also demonstrated to have a beneficial effect on the weight gain of tumor-bearing nude mice, and the mean weight of the megestrol acetate-treated animals was higher than that of controls from week 4 of the treatment period, and the differences were statistically significant in week 5 and 6 (P < 0.05, compared with controls). No significant survival advantage was, however, demonstrated in the treatment group. CONCLUSIONS: This study showed that megestrol acetate inhibited the growth of HepG2 cells grown in vitro and in vivo. These data provide useful information for clinical study of megestrol acetate for the treatment of HCC. 相似文献
110.