首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   874940篇
  免费   49719篇
  国内免费   1304篇
耳鼻咽喉   10254篇
儿科学   29646篇
妇产科学   20505篇
基础医学   126223篇
口腔科学   21432篇
临床医学   75632篇
内科学   163949篇
皮肤病学   16791篇
神经病学   65286篇
特种医学   34396篇
外国民族医学   76篇
外科学   132253篇
综合类   17097篇
现状与发展   2篇
一般理论   160篇
预防医学   68818篇
眼科学   18990篇
药学   63057篇
  3篇
中国医学   2982篇
肿瘤学   58411篇
  2019年   5440篇
  2018年   29113篇
  2017年   22880篇
  2016年   25734篇
  2015年   8405篇
  2014年   10983篇
  2013年   16060篇
  2012年   27172篇
  2011年   41814篇
  2010年   30916篇
  2009年   23073篇
  2008年   38817篇
  2007年   42517篇
  2006年   22335篇
  2005年   22458篇
  2004年   23206篇
  2003年   23107篇
  2002年   20799篇
  2001年   36569篇
  2000年   37276篇
  1999年   30523篇
  1998年   8061篇
  1997年   6853篇
  1996年   7038篇
  1995年   6716篇
  1994年   6187篇
  1993年   5641篇
  1992年   22995篇
  1991年   23001篇
  1990年   22428篇
  1989年   22148篇
  1988年   20082篇
  1987年   19452篇
  1986年   18488篇
  1985年   17332篇
  1984年   12714篇
  1983年   10761篇
  1982年   5945篇
  1979年   11520篇
  1978年   8136篇
  1977年   6835篇
  1976年   6602篇
  1975年   7273篇
  1974年   8517篇
  1973年   8142篇
  1972年   7658篇
  1971年   7127篇
  1970年   6896篇
  1969年   6325篇
  1968年   5796篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Bromocriptine (0.5 mg/kg) and apomorphine (0.03 mg/kg) exert moderate aphrodisiac effect in sexually sluggish rats. This effect appears rapidly and reaches its peak within 24 h. Amphetamine (2 mg/kg) acts similarly but with a more rapid onset and offset of the effect. A single dose of (-)deprenyl, a selective inhibitor of MAO-B, exerts a much more potent effect in this test.  相似文献   
93.
94.
We review evidence suggesting that deaf speakers do not move their articulators toward the following open posture throughout closure and report results from a preliminary cinefluorographic study. Two prelingually deaf and two hearing speakers produced two different strings of alternating heterogeneous monosyllables as though speaking in time with a metronome (the so-called P-center task). Events traditionally associated with vowel production appeared evenly timed throughout the productions, and, in general, the deaf speakers performed similarly to the hearing speakers. We relate the results to Fowler's (1983) interpretation of the P-center phenomenon as an indicant of continuous vowel production.  相似文献   
95.
Biopsies from the diseased bones of patients with familial expansile osteolysis (FEO) were examined by light and electron microscopy. Focal concentrations of multinuclear osteoclasts were present, and these contained viral-like microcylindrical inclusions which appeared exclusive to their nuclei. No consistent relationship was found between osteoclast size and the number of osteoclast nuclei containing microcylindrical inclusions. Quantitative histomorphometry showed evidence of increased bone remodelling with high bone cell densities and a decrease of the reversal period in bone remodelling. The lesions contained prominent woven bone and fibrovascular tissue, together with mononuclear cells and adipocytes. Little bone was found in the most radiolucent lesions, which were almost totally occupied by adipocytes and fibrovascular tissue. Serology did not reveal any significant differences between the viral antibody titres of patients and their age- and sex-matched controls. The present study suggests that intranuclear viral-like microcylindrical inclusions of osteoclasts are not a specific feature of Paget's disease, and are found in other disorders of osteoclast function, including pycnodysostosis, osteopetrosis, giant cell tumours, and familial expansile osteolysis.  相似文献   
96.
A tracer kinetic procedure was developed for the measurement of monoamine oxidase type B (MAO-B) activity using L-[11C]deprenyl and positron emission tomography (PET). The kinetic model consisted of two tissue compartments with irreversible binding to the second compartment (three rate constants). In addition, a blood volume component was included. Special attention was given to the accurate measurement of the plasma and whole blood input functions. The method was applied to the measurement of the dose-response curve of a reversible MAO-B inhibitor (Ro 19-6327). From the results, it followed that the rate constant for irreversible binding (k3) appeared to be a better index of MAO-B activity than the net influx constant Ki. Furthermore, regional analysis demonstrated that Ki, but not k3, was flow dependent. This implies that full kinetic analysis is required for an accurate assessment of MAO-B activity.  相似文献   
97.
The expression of two heat shock proteins, HSP72 and p57, in addition to ubiquitin, has been studied immunocytochemically in nine amyotrophic lateral sclerosis (ALS) cases and 10 age-matched controls. HSP72 and p57 antibodies did not identify the characteristic ubiquitin-immunoreactive inclusions present in anterior horn cells in ALS spinal cord. Antibodies to HSP72, but not to p57 or ubiquitin, strongly labelled structures corresponding to polyglucosan bodies in spinal grey matter. Such immunoreactive profiles were more abundant in ALS cases, although they were also present in control material. They were sometimes identified by haematoxylin and eosin and periodic acid Schiff reaction, but were not labeled by phosphotungstic acid haematoxylin or by antibodies to glial fibrillary acidic protein. Although ubiquitin, HSP72 and p57 are stress-induced proteins, they are expressed differently and might therefore have different significance in neuronal degeneration.  相似文献   
98.
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   
99.
A 65-year-old man with spontaneous rupture of the esophagus survived with a direct suture of the esophagus 15 hours after the onset of symptoms. Endoscopic examination of the esophagus was especially of great help in determining the surgical procedure in this patient, and we want to stress the importance of prompt diagnosis and immediate surgery for this disease.  相似文献   
100.
Effects of dexamethasone on central and peripheral ACTH systems in the rat   总被引:1,自引:0,他引:1  
To investigate the simultaneous effects of dexamethasone on peripheral and central adrenocorticotropic hormone (ACTH) systems, rats were treated with dexamethasone or saline for 4 days. Pituitary, plasma, hypothalamus and cerebrospinal fluid (CSF) were then collected and analyzed for ACTH immunoreactivity. Additionally, hypothalamic tissue extracts were analyzed for corticotropin-releasing hormone (CRH) immunoreactivity. Dexamethasone significantly lowered peripheral levels of ACTH as measured in pituitary and plasma. Hypothalamic ACTH content significantly increased while CSF ACTH significantly decreased with dexamethasone treatment. Hypothalamic CRH concentrations showed a small but statistically insignificant decrease. These results suggest that prolonged exposure to dexamethasone affects central as well as peripheral ACTH activity, corroborate our previous findings in rhesus monkeys of decreased CSF ACTH in response to prolonged dexamethasone treatment, suggest that dexamethasone may inhibit the release of ACTH from hypothalamic neurons into the CSF, and provide evidence that the effect of dexamethasone on pituitary ACTH content is of greater magnitude than its effect on hypothalamic CRH.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号