全文获取类型
收费全文 | 14453篇 |
免费 | 1366篇 |
国内免费 | 54篇 |
专业分类
耳鼻咽喉 | 203篇 |
儿科学 | 323篇 |
妇产科学 | 237篇 |
基础医学 | 2278篇 |
口腔科学 | 475篇 |
临床医学 | 1511篇 |
内科学 | 2771篇 |
皮肤病学 | 371篇 |
神经病学 | 1370篇 |
特种医学 | 619篇 |
外国民族医学 | 1篇 |
外科学 | 2317篇 |
综合类 | 229篇 |
一般理论 | 11篇 |
预防医学 | 1380篇 |
眼科学 | 190篇 |
药学 | 782篇 |
2篇 | |
中国医学 | 3篇 |
肿瘤学 | 800篇 |
出版年
2021年 | 226篇 |
2020年 | 157篇 |
2019年 | 224篇 |
2018年 | 232篇 |
2017年 | 199篇 |
2016年 | 221篇 |
2015年 | 229篇 |
2014年 | 382篇 |
2013年 | 554篇 |
2012年 | 804篇 |
2011年 | 880篇 |
2010年 | 484篇 |
2009年 | 381篇 |
2008年 | 833篇 |
2007年 | 795篇 |
2006年 | 758篇 |
2005年 | 720篇 |
2004年 | 703篇 |
2003年 | 648篇 |
2002年 | 679篇 |
2001年 | 319篇 |
2000年 | 303篇 |
1999年 | 263篇 |
1998年 | 169篇 |
1997年 | 160篇 |
1996年 | 140篇 |
1995年 | 128篇 |
1994年 | 136篇 |
1993年 | 121篇 |
1992年 | 228篇 |
1991年 | 229篇 |
1990年 | 224篇 |
1989年 | 179篇 |
1988年 | 217篇 |
1987年 | 166篇 |
1986年 | 165篇 |
1985年 | 157篇 |
1984年 | 148篇 |
1983年 | 121篇 |
1982年 | 143篇 |
1981年 | 120篇 |
1980年 | 102篇 |
1979年 | 127篇 |
1978年 | 120篇 |
1976年 | 92篇 |
1975年 | 99篇 |
1974年 | 92篇 |
1973年 | 109篇 |
1972年 | 96篇 |
1971年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Allen D. Roses Margaret A. Pericak-Vance Ann M. Saunders Donald Schmechel Dmitry Goldgaber Warren Strittmatter 《Epilepsia》1994,35(S1):S20-S28
Summary: Strategies used in molecular genetics have changed modern neurology. The gene or genes responsible for several major neurologic diseases have now been identified using "reverse" or positional genetics. Unexpected new genetic mechanisms have been discovered in human neurologic diseases, including (a) identical mutations of the prion protein gene in Creutzfeldt-Jakob disease and fatal familial insomnia with the phenotypic expression directed by an accompanying polymorphism; (b) stable duplications of chromosome 17 in Charcot-Marie-Tooth disease (type 1 A) that involve many genes, only one of which appears to cause neuropathy; and (c) highly variable, dynamic mutations in myotonic dystrophy, fragile X syndrome, and Kennedy's syndrome that modulate variable expressivity in multiple tissues. There is growing recognition that neurologic diseases are often complex genetic diseases with multifactorial rather than simple modes of inheritance. For example, genetic association/linkage strategies have interacted with biochemistry and immunopathology studies to produce new insights into the disease mechanism of late-onset Alzheimer's disease. The role of apolipoprotein E in late-onset Alzheimer's disease is an example of how new analytical techniques of genetic disease can be applied to dissect multiple genes. Similar research strategies are suggested for the study of epilepsy as a complex disease. 相似文献
43.
The effect of acute administration of nicotine on the secretory function of the human parotid gland was investigated in 4 male volunteers. After intravenous infusion of 20 micrograms nicotine/kg b.w. within 10 min in all subjects an increased salivary amylase activity and protein concentration was observed. This phenomenon is believed to be caused by a stimulation of parotid beta-adrenoceptors secondary to a nicotine-induced release of catecholamines from the adrenals. 相似文献
44.
N Din H G Damude N R Gilkes R C Miller Jr R A Warren D G Kilburn 《Proceedings of the National Academy of Sciences of the United States of America》1994,91(24):11383-11387
Endoglucanase A (CenA) from the bacterium Cellulomonas fimi is composed of a catalytic domain and a nonhydrolytic cellulose-binding domain that can function independently. The individual domains interact synergistically in the disruption and hydrolysis of cellulose fibers. This intramolecular synergism is distinct from the well-known intermolecular synergism between individual cellulases. The catalytic domain corresponds to the hydrolytic Cx system and the cellulose-binding domain corresponds to the nonhydrolytic C1 system postulated by Reese et al. [Reese, E. T., Sui, R. G. H. & Levinson, H. S. (1950) J. Bacteriol. 59, 485-497] to be required for the hydrolysis of cellulose. 相似文献
45.
46.
Inhibition of murine hepatitis virus infections by the immunomodulator 2,3,5,6,7,8-hexahydro-2-phenyl-8,8-dimethoxy-imidazo[1,2a]pyridine (PR-879-317A). 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Antimicrobial agents and chemotherapy》网站下载免费的PDF全文](/ch/ext_images/free.gif)
R W Sidwell J H Huffman E W Call R P Warren L A Radov R J Murray 《Antimicrobial agents and chemotherapy》1987,31(7):1130-1134
PR-879-317A (2,3,5,6,7,8-hexahydro-2-phenyl-8,8-dimethoxy-imidazo [1,2a]pyridine) has been found to be a T-cell-selective immunomodulating agent. In the current studies, a series of experiments was designed to determine the potential antiviral activity of this compound in mice infected with murine hepatitis virus. In a comparative antiviral experiment, the activity seen was superior to that of levamisole, a known immunorestorative agent. This activity was characterized by an increase in the 21-day survival frequency, a decrease in hepatic discoloration, a decrease in the amount of infectious virus recoverable from the liver, and normalization of serum glutamic oxalacetate and pyruvate transaminase levels. A comparison of treatment routes indicated the relative efficacies as intraperitoneal greater than per os greater than intramuscular greater than or equal to subcutaneous. Alteration of the treatment schedule markedly affected the antiviral effect; prophylactic or therapeutic treatments once or twice daily for 3 days were usually effective. Single treatments begun 4 h before or 24 h after virus inoculation were highly efficacious. Three treatments administered on alternate days, beginning 48 h before virus inoculation, proved moderately effective. Thrice-daily treatments were ineffective, as were treatments with durations of greater than 3 days. The optimal dosage varied according to the treatment route and dosage schedule. When assessed for direct antiviral activity in vitro, PR-879-317A failed to demonstrate any significant activity against murine hepatitis virus. The positive in vivo activity noted might therefore be the result of immune modulation rather than a direct antiviral effect. 相似文献
47.
48.
Increased sensitivity of virus-infected cells to inhibitors of protein synthesis does not correlate with changes in plasma membrane permeability 总被引:3,自引:0,他引:3
J M Cameron M J Clemens M A Gray D E Menzies B J Mills A P Warren C A Pasternak 《Virology》1986,155(2):534-544
Semliki Forest virus-infected BHK cells or herpes simplex virus-infected Vero cells were incubated with the protein synthesis inhibitors hygromycin B and gougerotin. Infected cells take up no more [3H]hygromycin or [3H]gougerotin than do mock-infected cells, at a time p.i. at which either compound is more inhibitory to protein synthesis in infected, than in mock-infected cells. The concentrations of hygromycin and gougerotin required to inhibit protein synthesis in intact cells (irrespective of whether they are infected or not) are several orders of magnitude higher than those required in either permeabilized cells or in cell-free systems. Infected cells take up 86Rb+ at the same rate as mock-infected cells, their intracellular content of K+ is the same, and the activity of the Na+ pump is the same. It is concluded that the increased efficacy of hygromycin and gougerotin in virus-infected cells is a consequence of altered intracellular compartmentation and that increases in permeability of the plasma membrane, if any, are so small as to be undetectable by direct methods. 相似文献
49.
50.
Scott A. Christopher Stepan Melnyk S. Jill James Warren D. Kruger 《Molecular genetics and metabolism》2002,75(4):109-343
Elevated plasma homocysteine is associated with a variety of diseases in humans including coronary heart disease, stroke, peripheral vascular disease, and birth defects. However, the mechanism by which plasma homocysteine affects cells is unknown. We have examined the growth of isogenic wild-type and cystathionine beta-synthase (CBS) deficient yeast in response to homocysteine and its immediate metabolic precursor, S-adenosylhomocysteine (SAH). CBS deficient yeast export significantly more homocysteine into the media than wild-type yeast and have elevated internal pools of homocysteine and SAH. We found that 5 mM homocysteine added to the media had very little effect on the growth of wild-type or CBS deficient yeast, although intracellular homocysteine concentrations increased five- to tenfold. In contrast, as little as 25 microM S-adenosylhomocysteine inhibited the growth of CBS deficient yeast, but had no effect on wild-type yeast. Measurements of the intracellular S-adenosylmethionine (SAM) and SAH indicate that CBS deficient yeast contain reduced SAM/SAH ratios relative to wild-type, and this ratio is further reduced by adding SAH to the media. Growth inhibition by SAH in CBS deficient yeast can be totally reversed by addition of SAM to the media, indicating that the ratio and not absolute level is critical for cell growth. These results suggest that CBS plays a key role in the regulation of the SAM/SAH ratio inside cells and that excessive perturbations of this ratio can inhibit growth. We hypothesize that elevated extracellular homocysteine present in humans may reflect an altered intracellular SAM/SAH ratio and that this may be related to disease pathogenesis. 相似文献