全文获取类型
收费全文 | 2358901篇 |
免费 | 175781篇 |
国内免费 | 5081篇 |
专业分类
耳鼻咽喉 | 32320篇 |
儿科学 | 74645篇 |
妇产科学 | 65662篇 |
基础医学 | 337017篇 |
口腔科学 | 69542篇 |
临床医学 | 210198篇 |
内科学 | 455095篇 |
皮肤病学 | 51909篇 |
神经病学 | 184676篇 |
特种医学 | 90521篇 |
外国民族医学 | 406篇 |
外科学 | 360710篇 |
综合类 | 58560篇 |
现状与发展 | 6篇 |
一般理论 | 751篇 |
预防医学 | 178469篇 |
眼科学 | 56605篇 |
药学 | 174552篇 |
7篇 | |
中国医学 | 5576篇 |
肿瘤学 | 132536篇 |
出版年
2018年 | 25106篇 |
2017年 | 19291篇 |
2016年 | 21356篇 |
2015年 | 24492篇 |
2014年 | 34370篇 |
2013年 | 50801篇 |
2012年 | 69686篇 |
2011年 | 73444篇 |
2010年 | 43308篇 |
2009年 | 40529篇 |
2008年 | 68585篇 |
2007年 | 73467篇 |
2006年 | 73764篇 |
2005年 | 71062篇 |
2004年 | 68898篇 |
2003年 | 65758篇 |
2002年 | 63466篇 |
2001年 | 114626篇 |
2000年 | 117229篇 |
1999年 | 97682篇 |
1998年 | 26761篇 |
1997年 | 23698篇 |
1996年 | 23625篇 |
1995年 | 22586篇 |
1994年 | 20964篇 |
1993年 | 19553篇 |
1992年 | 76262篇 |
1991年 | 73924篇 |
1990年 | 71579篇 |
1989年 | 68903篇 |
1988年 | 63483篇 |
1987年 | 62161篇 |
1986年 | 58668篇 |
1985年 | 56111篇 |
1984年 | 42045篇 |
1983年 | 35855篇 |
1982年 | 21035篇 |
1981年 | 19028篇 |
1979年 | 39009篇 |
1978年 | 27429篇 |
1977年 | 23256篇 |
1976年 | 21567篇 |
1975年 | 23010篇 |
1974年 | 28112篇 |
1973年 | 27099篇 |
1972年 | 25502篇 |
1971年 | 23678篇 |
1970年 | 22244篇 |
1969年 | 21051篇 |
1968年 | 19404篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Postpartum fatigue is a normal condition that most women experience. Breastfeeding is often associated in women's minds as contributing to the feeling of overall perceived fatigue, and many women indicate that they have ceased breastfeeding because of fatigue. However, the relationship between feeding choice and perceived fatigue has never been established. Two hundred and fifty-three women participated in a study examining whether perceived fatigue differed for bottle-feeding and breastfeeding women at 3 different times during the postpartum period (2-4 days, 6 weeks, and 12 weeks postpartum). Results showed no significant differences for these 2 groups, suggesting that perceived fatigue during the postpartum period is not dependent on feeding choice. Additional analyses examining other variables with a potential effect were nonsignificant. Because perceived physical fatigue does not appear to be dependent on feeding choice, women should be prepared for the feeling of perceived fatigue during the postpartum period while at the same time be reassured that feeding choice is not correlated. 相似文献
102.
103.
Caterina Proto Daniela Romualdi Rosa Maria Cento Rosario S Spada Giuseppina Di Mento Raffaele Ferri Antonio Lanzone 《Gynecological endocrinology》2006,22(4):213-218
BACKGROUND: In the central nervous system, several neuropeptides are believed to be involved in the pathophysiology of Alzheimer's disease (AD). Indeed, previous studies have documented that glucagon-like peptide 1 (GLP-1) possesses neurotropic properties and can reduce amyloid-beta peptide levels in the brain in vivo. Moreover, the concentrations of neuropeptide Y (NPY) seem to be altered in the cerebrospinal fluid of patients with AD and in subjects with major depression. Finally, among the modifications induced by aging, a dysregulation of the ghrelin-growth hormone (GH) system has been reported. METHODS: We investigated the plasma concentrations of these neuropeptides in 14 subjects with AD. Data obtained from these patients were compared with data from an age- and weight-matched healthy group. RESULTS: No significant differences were found between the two groups in relation to plasma levels of GLP-1, NPY, ghrelin and GH. Peripheral NPY concentrations were positively correlated with ghrelin levels in both groups, and with plasma GLP-1 concentration only in controls. CONCLUSION: On the basis of our results, peripheral levels of these neuropeptides seem not to serve as biochemical markers of AD. 相似文献
104.
105.
We present evidence to show that monoclonal antibodies to estrogen receptors (ER) in solid phase recognize the secondary estrogen binding sites with moderate to low affinity for estradiol (E2). An excellent quantitative agreement was found in five cytosols between the ER values obtained by the enzyme immunoassay (ER-EIA) and the amount of secondary estrogen binding sites measured by the assay involving dextran-coated charcoal (Clin Chem 1986;32:1496). The immunoreactive protein recognized by the antibody-coated beads, when allowed to react with ER(+) cytosols, is shown to bind [3H]estradiol only when the ligand concentration exceeds 8 nmol/L. Further biochemical and functional characterization of the immunoreactive protein is required to establish similarities/dissimilarities between this protein, high-affinity Type I ER sites, and the secondary sites such as Type II sites. 相似文献
106.
107.
A mechanistic QSAR study on N-nitrosamines (NA) was performed with the aid of the semiempirical MINDO/3 method. Both the chemical reactivity and the transport in biological medium were taken into account. The parent NA molecules and their first reaction intermediates in the metabolic activation pathway were examined for possible determinants of the relative carcinogenic potency. The correlations found support the previous suggestions concerning the metabolic C alpha radical hydroxylation of NA. The role of transport properties in the early stage of NA biotransformation was also demonstrated. 相似文献
108.
S Hummel J Slapke 《Zeitschrift für die gesamte innere Medizin und ihre Grenzgebiete》1988,43(12):319-323
In any case of acute bronchoconstriction the possibility of an adverse reaction to a drug should be considered. In many of such side reactions no allergic mechanism can be detected. Therefore, they are included into the category of pseudoallergic reactions (PAR). The clinically most important form of drug-induced bronchial asthma, analgesics asthma, belongs to this PAR group. A further risk for asthmatics are intravenous applications of contrast-media for roentgenography which in about 15% induce a severe, sometimes life-threatening pseudo-allergic adverse reaction. In asthmatics, the application of any beta-receptor blocking agents and also the use of parasympathicotonic eye drops for treatment of glaucoma are contraindicated. Paradoxical bronchial constriction following application of antiasthmatics are preponderantly caused by locally irritative actions, less frequently by genuine allergic phenomena or additive intolerance. The most reliable prophylaxis against drug-induced bronchial asthma consists in strong avoidance of all derivatives possibly capable to trigger any intolerance. A respective warning should entered into the emergency passport. 相似文献
109.
110.
The use of additional epidural sympathetic block during and after microvascular surgery in the lower extremities to prevent vasospasm is generally agreed on. However, a significant fall in the perfusion rate of the transplants was seen after application of bupivacaine (Marcain) via the epidural catheter. This effect has, to our knowledge, not been described before and is probably caused by the sympathectomy effect of this type of analgesia. 相似文献