全文获取类型
收费全文 | 1832943篇 |
免费 | 141561篇 |
国内免费 | 3773篇 |
专业分类
耳鼻咽喉 | 24380篇 |
儿科学 | 60254篇 |
妇产科学 | 51953篇 |
基础医学 | 271823篇 |
口腔科学 | 50166篇 |
临床医学 | 163857篇 |
内科学 | 357619篇 |
皮肤病学 | 43011篇 |
神经病学 | 145585篇 |
特种医学 | 68871篇 |
外国民族医学 | 523篇 |
外科学 | 274584篇 |
综合类 | 39750篇 |
现状与发展 | 3篇 |
一般理论 | 583篇 |
预防医学 | 143742篇 |
眼科学 | 41872篇 |
药学 | 133048篇 |
1篇 | |
中国医学 | 4122篇 |
肿瘤学 | 102530篇 |
出版年
2018年 | 20240篇 |
2017年 | 15365篇 |
2016年 | 17351篇 |
2015年 | 19406篇 |
2014年 | 27175篇 |
2013年 | 40798篇 |
2012年 | 55494篇 |
2011年 | 59195篇 |
2010年 | 34766篇 |
2009年 | 33098篇 |
2008年 | 55001篇 |
2007年 | 58494篇 |
2006年 | 59250篇 |
2005年 | 57247篇 |
2004年 | 54999篇 |
2003年 | 52462篇 |
2002年 | 50963篇 |
2001年 | 90990篇 |
2000年 | 93280篇 |
1999年 | 77189篇 |
1998年 | 21318篇 |
1997年 | 19093篇 |
1996年 | 19419篇 |
1995年 | 18351篇 |
1994年 | 16778篇 |
1993年 | 15818篇 |
1992年 | 58492篇 |
1991年 | 56955篇 |
1990年 | 55275篇 |
1989年 | 52866篇 |
1988年 | 48531篇 |
1987年 | 47648篇 |
1986年 | 44534篇 |
1985年 | 42483篇 |
1984年 | 32211篇 |
1983年 | 27170篇 |
1982年 | 16078篇 |
1981年 | 14432篇 |
1979年 | 28989篇 |
1978年 | 20672篇 |
1977年 | 17210篇 |
1976年 | 16427篇 |
1975年 | 17451篇 |
1974年 | 21045篇 |
1973年 | 20064篇 |
1972年 | 18999篇 |
1971年 | 17666篇 |
1970年 | 16561篇 |
1969年 | 15580篇 |
1968年 | 14738篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Bronchoalveolar lavage fluid neutrophils were studied by the cytologic methods in 58 patients with chronic bronchitis, 63 ones with bronchiectasis, and 8 normal controls. The study included cytospectrophotometry of myeloperoxidase and alkaline phosphatase activity and estimation of active oxygen-producing cells in the NBT test. Neutrophilic functional activity was different in the patients with chronic bronchitis and bronchiectasis. Neutrophilic myeloperoxidase and alkaline phosphatase activities were lower in the patients with chronic bronchitis than in those with bronchiectasis, whereas the counts of cells active in the NBT test were low in both patient populations. 相似文献
992.
This article describes the outcomes of a study involving family members of communication-impaired long-term care residents in a collaborative nursing/speech language pathology intervention designed to increase the residents' communication ability. Family members provided memorabilia and artifacts or produced audio or video tapes, for use in conjunction with a speech therapy enhancement program (STEP). Findings revealed that, despite a minimal improvement in speech ability, there was a dramatic increase in family members' satisfaction. 相似文献
993.
This study was undertaken to assess the role of the hypothalamus and medulla oblongata in regulation of liver circulation in anesthetized dogs. Blood pressure, flow in hepatic artery and portal vein, and shifts of blood volume in the liver were recorded. Stimulation of the anterior hypothalamus produced changes in arterial pressure which were followed by passive changes in hepatic arterial blood flow; changes in hepatic artery resistance were rather small. Stimulation of the medial and posterior hypothalamus increased hepatic arterial resistance by 65-170%. Liver portal blood flow during stimulation of most of the hypothalamic sites decreased, hepatic portal pressure rose and vascular portal venous resistance increased 2.5-3 times. Three areas only (sympatho-inhibitory area, paraventricular and lateral hypothalamic nuclei) when stimulated produced dilatation of hepatic portal and splanchnic vascular beds, thus increasing portal blood flow. All cases of stimulation led to the decrease of blood volume in the liver by 10-36%. Stimulation of medullary structures (n. tractus solitarii, reticular nn.) caused similar changes in hepatic circulation, however the amplitude of reaction was 1.5-6 times smaller than upon hypothalamic stimulation. Central impulses to the hepatic vessels are transmitted by sympathetic adrenergic nerve fibers through vascular alpha-adrenoreceptors. It is concluded that the hypothalamic level of the central nervous system, unlike the bulbar one, exerts considerable, differentiated, well coordinated and to some extent specific influences on hepatic circulation. 相似文献
994.
995.
Characterization of unique ADTN-catecholamine binding sites in the iris root-ciliary body of rabbits
A binding site for tritiated 2-amino-6, 7-dihydroxy-1, 2,3,4-tetrahydronaphthalene (ADTN) has been partially characterized in the rabbit iris root-ciliary body. Binding of ADTN is proportional to protein content and requires at least 60 minutes to reach equilibrium. Binding is saturable, with a Kd of 27 +/- 1 nM and a Bmax of 2.1 +/- .3 pmol/mg protein (mean +/- SEM). Dopamine competes for this site with a Ki of 100 nM and apomorphine with a Ki of 180 nM. This site is not blocked by L-timolol, phenoxybenzamine, or by several DA1 and DA2 antagonists. It appears to be a new type of catecholamine binding site, of a type not observed outside the anterior eye. It is possible that some of the effects of dopamine on intraocular pressure are mediated through this binding site. 相似文献
996.
The extent to which repeated administration produces tolerance to nicotine-induced increases in dopamine transmission in the nucleus accumbens was investigated in rats. In vivo microdialysis was used to sample extracellular dopamine and metabolites after a nicotine challenge (0.35 mg/kg) in (1) naive rats, (2) acutely pretreated rats (1 prior nicotine injection), and (3) chronically pretreated rats (12-15 prior daily nicotine injections, 0.35 mg/kg per injection). Nicotine increased extracellular DA and its metabolites, and these increases were not significantly altered by either acute or chronic prior exposure to the drug. The failure to find evidence of tolerance is compatible with the hypothesis that the mesolimbic dopaminergic system is a substrate for the reinforcing properties of chronically administered nicotine. 相似文献
997.
Biodistributions of 201Tl in tumor bearing animals and inflammatory lesion induced animals 总被引:1,自引:0,他引:1
A Ando I Ando M Katayama S Sanada T Hiraki H Mori N Tonami K Hisada 《European journal of nuclear medicine》1987,12(11):567-572
The accumulation of 201Tl in tumor and inflammatory tissues were small. However, this nuclide showed a high concentration in viable tumor tissue, less in connective tissue (containing inflammatory tissue), and was not seen in necrotic tumor tissue regardless of the time after administration of 201Tl(I)-chloride. In inflammatory lesions, 201Tl accumulated in subcutaneous tissue infiltrated with neutrophils and macrophages, and quite large amounts of this nuclide were accumulated in subcutaneous tissue and sites where neutrophils were crowded. Most 201Tl existed in a free form in the fluid of tumor and inflammatory tissues regardless of the time after administration. A small amount of this nuclide was localized in the nuclear, mitochondrial and microsomal fractions in these tissues, and the nuclide was bound to protein in these fractions. The distribution of 201Tl(III)-chloride in tumor bearing animals was essentially the same as that of 201Tl(I)-chloride. 相似文献
998.
999.
1000.
The study concerned the effects of acute and chronic clomipramine administration to male rats on exploratory activity in a novel environment (hole-board) and on immobility in the forced swimming test. Acute clomipramine administration did not alter either exploratory activity on a hole-board as measured 3 or 20 h after drug administration, or immobility in the forced swimming test as measured 20 h after drug administration. Approximately 20 h after the last injection of clomipramine, the rats chronically treated with the drug showed reduced exploratory activity on the hole-board. In contrast, chronic clomipramine treatment significantly increased the activity in the forced swimming test. The effects of the drug on exploratory and forced swimming activities persisted for 14 days after the cessation of clomipramine administration. These data indicate that chronic clomipramine administration exerted profound and long-lasting effects on central nervous system function. The long-lasting action of the drug on behaviour in the forced swimming test might explain the long-term beneficial effect of antidepressant drugs in counteracting behavioral depression. 相似文献