全文获取类型
收费全文 | 1552547篇 |
免费 | 119188篇 |
国内免费 | 3760篇 |
专业分类
耳鼻咽喉 | 20344篇 |
儿科学 | 51033篇 |
妇产科学 | 45184篇 |
基础医学 | 219747篇 |
口腔科学 | 41829篇 |
临床医学 | 135716篇 |
内科学 | 315756篇 |
皮肤病学 | 37877篇 |
神经病学 | 128485篇 |
特种医学 | 57023篇 |
外国民族医学 | 494篇 |
外科学 | 228326篇 |
综合类 | 33539篇 |
现状与发展 | 3篇 |
一般理论 | 520篇 |
预防医学 | 125095篇 |
眼科学 | 34347篇 |
药学 | 108965篇 |
1篇 | |
中国医学 | 3780篇 |
肿瘤学 | 87431篇 |
出版年
2021年 | 14129篇 |
2019年 | 14814篇 |
2018年 | 20798篇 |
2017年 | 15355篇 |
2016年 | 16959篇 |
2015年 | 18962篇 |
2014年 | 26509篇 |
2013年 | 39121篇 |
2012年 | 54122篇 |
2011年 | 56864篇 |
2010年 | 33156篇 |
2009年 | 31353篇 |
2008年 | 51607篇 |
2007年 | 54455篇 |
2006年 | 54799篇 |
2005年 | 53195篇 |
2004年 | 50623篇 |
2003年 | 48039篇 |
2002年 | 46318篇 |
2001年 | 76578篇 |
2000年 | 78213篇 |
1999年 | 64676篇 |
1998年 | 17992篇 |
1997年 | 16174篇 |
1996年 | 16263篇 |
1995年 | 15371篇 |
1994年 | 13875篇 |
1993年 | 13031篇 |
1992年 | 47523篇 |
1991年 | 45108篇 |
1990年 | 43052篇 |
1989年 | 40927篇 |
1988年 | 37488篇 |
1987年 | 36660篇 |
1986年 | 34111篇 |
1985年 | 32476篇 |
1984年 | 24725篇 |
1983年 | 20792篇 |
1982年 | 12662篇 |
1981年 | 11172篇 |
1979年 | 21605篇 |
1978年 | 15182篇 |
1977年 | 12575篇 |
1976年 | 11874篇 |
1975年 | 12225篇 |
1974年 | 14792篇 |
1973年 | 14327篇 |
1972年 | 13338篇 |
1971年 | 12113篇 |
1970年 | 11611篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A. Purohit S. Laffer† C. Metz-Favre A. Verot F. Kricek‡ R. Valenta† G. Pauli 《Clinical and experimental allergy》2005,35(2):186-192
BACKGROUND: Results from several studies indicate that the magnitude of immediate symptoms of type I allergy caused by allergen-induced cross-linking of high-affinity Fc epsilon receptors on effector cells (mast cells and basophils) is not always associated with allergen-specific IgE levels. OBJECTIVE: To investigate the association of results from intradermal skin testing, basophil histamine release and allergen-specific IgE, IgG1-4, IgA and IgM antibody levels in a clinical study performed in birch pollen-allergic patients (n = 18). METHODS: rBet v 1-specific IgEs were measured by quantitative CAP measurements and by using purified Fc epsilon RI-derived alpha-chain to quantify IgE capable of binding to effector cells. Bet v 1-specific IgG subclasses, IgA and IgM levels were measured by ELISA, and basophil histamine release was determined in whole blood samples. Intradermal skin testing was performed with the end-point titration method. RESULTS: Our study demonstrates on the molecular level that the concentrations of allergen-specific IgE antibodies capable of binding to Fc epsilon RI and biological sensitivities are not necessarily associated. A moderate association was found between cutaneous and basophil sensitivity. CONCLUSION: Our results highlight the quantitative discrepancies and limitations of the present diagnostic tools in allergy, even when using a single allergenic molecule. The quantity of allergen-specific serum IgE is only one component of far more complex cellular systems (i.e. basophil-based tests, skin tests) used as indirect diagnostic tests for IgE-mediated allergic sensitivity. 相似文献
992.
993.
Brain and spinal cord hemorrhage in long-term survivors of malignant pediatric brain tumors: a possible late effect of therapy 总被引:1,自引:0,他引:1
Three children with malignant primary CNS tumors treated with craniospinal radiotherapy developed intraparenchymal hemorrhages a median of 5 years following therapy in sites distant from the primary tumor. Radical surgical procedures disclosed fresh and old hematoma, gliosis, and necrosis in all 3 patients and an aggregation of abnormal microscopic blood vessels in two. No tumor was found. All 3 patients remain in long-term (greater than 10 years) continuous remission. 相似文献
994.
Evidence that dopamine in the nucleus accumbens is involved in the ability of rats to switch to cue-directed behaviours. 总被引:2,自引:0,他引:2
R van den Bos G A Charria Ortiz A C Bergmans A R Cools 《Behavioural brain research》1991,42(1):107-114
Recently we have reported that injections of d-amphetamine into the nucleus accumbens enhanced the number of switches to cue-directed behaviours without an effect on the number of switches to non-cue-directed behaviours in a swimming test. In the present study we investigated to what extent this effect is mediated via the dopaminergic system in the nucleus accumbens. For that purpose drugs selective for D1- and D2-receptors were studied in this swimming test. It was found that the selective D2-agonist LY 171 555 (50 ng/0.5 microliters) enhanced the number of different cue-directed behaviours. The selective D2-antagonist raclopride (50 ng/0.5 microliters) decreased it. Furthermore an ineffective dose of raclopride attenuated the effect of LY 171 555. Both the selective D1-antagonist SCH 23390 (400 ng/0.5 microliters) and the selective D1-agonist SKF 38393 (50-400 ng/0.5 microliters) decreased the number of different cue-directed behaviours. The effect induced by SCH 23390 could not be blocked by SKF 38393. Similarly the effect induced by SKF could not be attenuated by SCH 23390. These data point to a role for dopamine D2-receptors in the ability to switch to cue-directed behaviours. The present findings do not yet allow the conclusion that D1-receptors are involved. 相似文献
995.
A survey of hospitals in New York State treating psychiatric patients with chemical abuse disorders.
Eighty-eight of 143 hospitals in New York State providing psychiatric inpatient treatment responded to a mailed questionnaire designed to determine the size of three subgroups of chemical abusers--alcohol abusers, drug abusers, and polychemical abusers--among inpatients with psychiatric diagnoses, as well as the availability of services for these patients. Data for New York City and its metropolitan area were analyzed separately. In 1987 almost one-third of psychiatric admissions both in and outside the metropolitan area had comorbid chemical abuse disorders. Seventy-five percent of patients in the metropolitan area with comorbid chemical abuse had a drug abuse disorder; in rural areas 88 percent of patients with chemical abuse disorders abused alcohol. Both hospital- and community-based aftercare services, especially in the metropolitan area, were less available to psychiatric patients with chemical abuse than to patients without these disorders. 相似文献
996.
R Benigni M Cotta-Ramusino C Andreoli 《Journal of toxicology and environmental health》1991,34(3):397-407
This paper is a quantitative analysis of the relationship between the chemical structure and the Salmonella mutagenicity of a number of chlorofluorocarbons (CFC). The molecules were characterized by both molecular orbital and physical chemical parameters. The results of the analysis indicated that the CFC mutagenicity is correlated with two parameters: the free energy of binding to biological receptors, and the energy of the highest occupied molecular orbital (HOMO). Since these are the same factors that would favor the cytochrome P-450-catalyzed metabolism, it would appear that the CFC mutagenicity is determined more by the rate of initial activation than by the rate of DNA attack. 相似文献
997.
V L Towle J C Witt S H Nader A T Reder R Foust J P Spire 《Electroencephalography and clinical neurophysiology》1991,80(5):339-346
Pattern visual evoked potentials were obtained from 46 patients with definite relapsing/remitting multiple sclerosis, using both a conventional 5-channel occipital array and a 3-D recording technique consisting of three bipolar derivations approximating the three dimensions of space. These three orthogonal wave forms were displayed as a 3-D Lissajous trajectory for each subject. Two of the 15 patients with completely normal conventional pattern VEPs had abnormalities of the orientation of the B-C curvilinear segment of the 3-D pattern VEPs. Delays in the first major occipital positive component (P100) were evident using both techniques; the correlation between P100 latency and the latency of the corresponding trajectory apex was r = 0.99 (P less than 0.01). Post-chiasmal MRI abnormalities were associated with 3-D VEP orientation abnormalities. Three-dimensional pattern VEPs are moderately more sensitive than conventional pattern VEPs at detecting dysfunction posterior to the optic chiasm in demyelinating disease and do not require the use of eccentric fixation to do so. 相似文献
998.
A Federico C Battisti M P Eusebi N de Stefano A Malandrini M Mondelli N Volpi 《European neurology》1991,31(6):366-371
We report the clinical, neurophysiological (comprehending electromyography, nerve conduction velocities, and multimodal evoked potentials), histological study of the nerve and muscle and the effect of vitamin E supplement in a 32-year-old case with chronic vitamin E deficiency subsequent to acquired intestinal malabsorption. An early diagnosis for an early treatment is essential in preventing severe neurological deterioration. 相似文献
999.
1000.
Gonadotrophin-releasing hormone agonists (GnRHAs) were investigated as contraceptive agents from the late 1970's to the mid-1980's. They were abandoned as they appeared to offer no advantage over conventional combination-type oral contraceptives (COCs). This conclusion appears to be incorrect. We propose here a contraceptive regimen of a depot formulation of a GnRHA plus add-back estrogen and intermittent progestogen. The dose of add-back sex-steroids is substantially less than that in COCs; this reduction in sex-steroids should lead to a major reduction in lifetime breast cancer occurrence. 相似文献