全文获取类型
收费全文 | 25667篇 |
免费 | 1421篇 |
国内免费 | 181篇 |
专业分类
耳鼻咽喉 | 330篇 |
儿科学 | 523篇 |
妇产科学 | 643篇 |
基础医学 | 3047篇 |
口腔科学 | 773篇 |
临床医学 | 1979篇 |
内科学 | 6911篇 |
皮肤病学 | 434篇 |
神经病学 | 2618篇 |
特种医学 | 899篇 |
外国民族医学 | 10篇 |
外科学 | 3745篇 |
综合类 | 90篇 |
一般理论 | 9篇 |
预防医学 | 1160篇 |
眼科学 | 320篇 |
药学 | 1638篇 |
1篇 | |
中国医学 | 45篇 |
肿瘤学 | 2094篇 |
出版年
2023年 | 166篇 |
2022年 | 362篇 |
2021年 | 707篇 |
2020年 | 416篇 |
2019年 | 585篇 |
2018年 | 678篇 |
2017年 | 497篇 |
2016年 | 608篇 |
2015年 | 655篇 |
2014年 | 976篇 |
2013年 | 1247篇 |
2012年 | 1924篇 |
2011年 | 1928篇 |
2010年 | 1136篇 |
2009年 | 1020篇 |
2008年 | 1737篇 |
2007年 | 1668篇 |
2006年 | 1617篇 |
2005年 | 1582篇 |
2004年 | 1456篇 |
2003年 | 1351篇 |
2002年 | 1245篇 |
2001年 | 247篇 |
2000年 | 247篇 |
1999年 | 264篇 |
1998年 | 223篇 |
1997年 | 200篇 |
1996年 | 207篇 |
1995年 | 183篇 |
1994年 | 149篇 |
1993年 | 135篇 |
1992年 | 170篇 |
1991年 | 113篇 |
1990年 | 145篇 |
1989年 | 110篇 |
1988年 | 115篇 |
1987年 | 116篇 |
1986年 | 89篇 |
1985年 | 92篇 |
1984年 | 103篇 |
1983年 | 85篇 |
1982年 | 77篇 |
1981年 | 72篇 |
1980年 | 68篇 |
1979年 | 52篇 |
1978年 | 49篇 |
1977年 | 38篇 |
1976年 | 36篇 |
1975年 | 33篇 |
1972年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
91.
92.
Summary A two-cell human embryo recovered from the Fallopian tube 82 h following the LH peak in plasma and 37 h after a single episode of intercourse was examined by transmission electron microscopy. At the time of recovery the embryo was denuded of cumulus cells, and both the zona pellucida and the two adjoining blastomeres were intact. The finding of two polar bodies in the perivitelline space, two nucleated blastomeres and remnants of the fertilizing sperm tail within the cytoplasm of one of them, were considered as evidences that the embryo was normally fertilized. Among the most compicuous features found were the presence of very distinct desmosome-like structure between blastomeres, and the cytoplasmic cell organelles distribution in three areas referred as: a sub-cortical, a middle and a perinuclear bands. An outstanding feature was the extensive blebbing of the nuclear envelope. In general, the features seem to correspond to a normally developing two-cell embryo undergoing cleavage at a normal rate. 相似文献
93.
The central effects of the new antihistamine loratadine and three reference antihistamine agents were studied in the cat. As a sensitive measure of drug action on the central nervous system (CNS) we evaluated changes in sleep-waking patterns. For comparison, diphenhydramine was studied as an example of an antihistamine having potent central effects; astemizole and terfennadine were used as examples of new agents claimed to be free of CNS effects. Diphenhydramine, given at 3 mg/kg p.o., increased spindle sleep, i.e., the electrophysiological correlate of drowsiness, and suppressed rapid eye movement (REM) sleep. In addition, cats displayed unusual sleep postures during the various sleep stages. Loratadine had little or no effect on the various features of sleep-waking patterns over a broad dose range (3 and 30 mg/kg p.o.). Astemizole, at 30 mg/kg p.p., significantly increased wakefulness and reduced both slow-wave sleep and REM. No significant changes of the sleep patterns occurred after the low dose of 3 mg/kg. Terfenadine reduced REM duration at 30 mg/kg p.o. but had no effects on sleep patterns at 3 mg/kg. The cat appeared to be a sensitive animal model to the central action of antihistamines since the reference drug diphenhydramine affected sleep-waking patterns at a dose that closely approximates the dose requirements for adverse CNS effects in man. Under the same conditions, loratadine was free of central actions at a dose range far above that effective either therapeutically or in standard tests in other animal species. Astemizole and terfenadine seemed to be devoid of CNS effects at doses similar to those effective as antihistamines in man, but they produced some central actions at higher doses. Comparing the clinically effective doses of the antihistamines examined, loratadine appears to be the least liable to produce adverse effects on the CNS function. 相似文献
94.
Mario Casmiro MD 《Neurosurgical review》1998,21(1):43-47
A 70-year-old female presented with the clinical triad of normal pressure hydrocephalus (NPH) and senile tremor. Neuroimaging disclosed findings of both NPH and empty sella (ES). A ventriculoperitoneal shunt did not modify the clinical course except for a mild and transient improvement, and shunt malfunction occured later on. The association of NPH and ES may result from a common underlying mechanism such as transient increases in intracranial pressure. 相似文献
95.
Emanuele Lezoche M.D. Alessandro M. Paganini M.D. Ph.D. Francesco Carlei M.D. Francesco Feliciotti M.D. Davide Lomanto M.D. Ph.D. Mario Guerrieri M.D. 《World journal of surgery》1996,20(5):535-542
n
= 2), port site infection (
n
= 2), and subumbilical hematoma (
n
= 1). Major morbidity was bile leakage from the cystic duct stump in two cases due to clips or transcystic duct drainage displacement,
respectively. One elderly, high risk patient died after being referred for several failed attempts of endoscopic clearance;
she died from cardiogenic shock 3 days after successful laparoscopic treatment. Laparoscopic CBD exploration is feasible and
safe in most patients, with short-term results that compare favorably with the results of sequential ES/LC reported in the
literature. 相似文献
96.
Rainaldi Giuseppe; Meneveri Raffaella; Mariani Laura; Ginelli Enrico; Moretti Arcangela; Vatteroni Lucia 《Mutagenesis》1996,11(4):401-404
Clone CSA7 is a CHEF18 hamster cell line that shows an increasedintracellular accumulation of dCTP. To localize the mutationsthat accumulate spontaneously in a functional gene of such amutator phenotype, independent CSA7 mutants of the hypoxanthineguaninephosphoribosyl transferase (hprt) gene were isolated and screenedby a polymerase chain reactionsingle strand conformationpolymorphism technique. Sixty-two percent of mutants produceddetectable changes of the strand migration profile and the mutationswere preferentially localized in the exons 3 (31%) and 6 (62%).The sequencing of such exons revealed that the rate of C baseincorporation was the major mutation pathway and that the Abase of a GGA sequence was the preferential site of misincorporation.
3To whom correspondence should be addressed 相似文献
97.
Anne L Symons MDS PhD Mario Bortolanza BDSc Stephen Godden BDSc Gregory Seymour BDS MDSc PhD MRCPath 《Special care in dentistry》1993,13(3):96-101
Multiple sclerosis (MS) is an inflammatory disease of unknown etiology involving the central nervous system. Since MS affects the whole body, orofacial aspects of the disease must be expected, particularly since loss of muscular coordination may result in a diminished ability to maintain oral hygiene. This preliminary study examined the dental health status of 22 volunteer MS patients. A questionnaire collected data regarding medical and dental histories and socieo-demographic information. Extra- and intra-oral examinations were carried out on all subjects to determine the particular dental treatment needs of this special group. The DMFT and CPITN scores for this group did not indicate that MS patients were more susceptible to dental caries or periodontal disease. However, the prevalence of trigeminal neuralgia and symptoms of TMJ dysfunction in the group studied indicated that these conditions may be manifest in MS patients and warrant further investigations. 相似文献
98.
Massimo A Mariani MD PhD Tjalling W Waterbolk MD Tjark Ebels MD PhD 《The Annals of thoracic surgery》1998,66(6):2087-2089
We report the cases of 2 newborns who underwent at 7 days of age an arterial switch operation for transposition of the great arteries with a rare coronary anomaly: the left and right coronary arteries originated with a single ostium from sinus 1 and the sinus node artery had an isolated origin from sinus 2. The sinus node artery was reimplanted into the new aorta in both patients. Both babies were discharged in sinus rhythm. Preserving the vascularization of the sinus node may avoid the occurrence of postoperative atrial rhythm disturbances. 相似文献
99.
100.
Mario Perez-Reyes MD Robert E. Hicks PhD Jean Bumberry BS A. Robert Jeffcoat PhD C. Edgar Cook PhD 《Alcoholism, clinical and experimental research》1988,12(2):268-276
This is a report of the results of a placebo-controlled study in which the effects of the interaction between ethanol and marihuana on drug plasma concentrations, subjective ratings of intoxication, heart rate acceleration, and psychomotor performance were investigated. Six healthy, male, paid volunteers, moderate users of ethanol and marihuana, participated in the study. Ethanol (0.42 g/kg, 0.85 g/kg, or placebo) was administered over a 30-min interval. Fifteen minutes later the subjects smoked, in their customary manner, NIDA cigarettes containing 2.4% or 0.0004% (placebo) delta-9-tetrahydrocannabinol (THC). Each subject was tested in a single-blind, latin-square crossover design with the following six conditions: placebo ethanol/placebo marihuana; low dose ethanol/placebo marihuana; high dose ethanol/placebo marihuana; placebo ethanol/marihuana; low dose ethanol/marihuana; and high dose ethanol/marihuana. The variables measured in the study were: (a) subjective rating of ethanol and/or marihuana intoxication; (b) heart rate; (c) accuracy and latency of response in the Simulator Evaluation of Drug Impairment (SEDI) task; (d) blood ethanol concentration by gas chromatography; and (e) plasma concentration of THC by radioimmunoassay. The results indicate that the decrements due to ethanol in performance of skills necessary to drive an automobile were significantly enhanced by marihuana in an additive and perhaps synergistic manner. The administration of ethanol prior to marihuana smoking did not produce significant effects on the subjective rating of "high," heart rate acceleration, or THC plasma concentration. 相似文献