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   1350089篇
  免费   95173篇
  国内免费   2974篇
耳鼻咽喉   19976篇
儿科学   40602篇
妇产科学   38936篇
基础医学   189241篇
口腔科学   40389篇
临床医学   113914篇
内科学   264921篇
皮肤病学   30470篇
神经病学   107697篇
特种医学   54448篇
外国民族医学   435篇
外科学   210303篇
综合类   31141篇
现状与发展   6篇
一般理论   446篇
预防医学   92872篇
眼科学   31880篇
药学   101054篇
  4篇
中国医学   3020篇
肿瘤学   76481篇
  2018年   12030篇
  2016年   10922篇
  2015年   12250篇
  2014年   17143篇
  2013年   25922篇
  2012年   33856篇
  2011年   35757篇
  2010年   21271篇
  2009年   20688篇
  2008年   34352篇
  2007年   37483篇
  2006年   37997篇
  2005年   36737篇
  2004年   35738篇
  2003年   34680篇
  2002年   34137篇
  2001年   63962篇
  2000年   65608篇
  1999年   55657篇
  1998年   14796篇
  1997年   13572篇
  1996年   13072篇
  1995年   12326篇
  1994年   11574篇
  1992年   42907篇
  1991年   41414篇
  1990年   40673篇
  1989年   39685篇
  1988年   37072篇
  1987年   36514篇
  1986年   34997篇
  1985年   33207篇
  1984年   24906篇
  1983年   21120篇
  1982年   12720篇
  1981年   11616篇
  1979年   23990篇
  1978年   17130篇
  1977年   14900篇
  1976年   13418篇
  1975年   15309篇
  1974年   18127篇
  1973年   17602篇
  1972年   16863篇
  1971年   15755篇
  1970年   14940篇
  1969年   14376篇
  1968年   13498篇
  1967年   12054篇
  1966年   11285篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A review of hip radiographs of patients with severe hemophilia showed Legg-Calvé-Perthes disease in four of 63 patients examined before the era of specific treatment. In another series of 44 patients receiving prophylactic treatment, there was no evidence of Legg-Calvé-Perthes disease. A case report of a boy with severe hemophilia with hip joint bleeding that caused joint capsule distention and greatly increased intracapsular pressure is presented. Based on our findings, and previously published results, we suggest that Legg-Calvé-Perthes disease in hemophilia is caused by increased intracapsular pressure secondary to hemarthrosis.  相似文献   
992.
During a routine physical examination in 1976, a 54-year-old man was noted to suffer from hearing difficulty and continuing tinnitus of his right ear. He had, however, no further consultations for the next five years, although the symptom persisted and gradually worsened. In May 1981, he experienced complete hearing loss in his right ear. A computed tomography disclosed no abnormalities, and other laboratory tests were unremarkable. In September 1981, the patient began to complain of paresthesia of the right angle of the mouth and tongue, right-sided facial paralysis, and walking difficulty. A repeated computed tomography showed a tumor at the right cerebellopontine angle region. A clinical diagnosis of acoustic schwannoma was made. The first operation was performed in December 1981. Complete removal of the tumor was impossible because of its unexpected, unusual hardness. The pathologic diagnosis was a malignant mesenchymal tumor, compatible with a malignant nerve sheath tumor of the acoustic nerve. A second operation was performed in January 1982, but the rapid postoperative regrowth of the tumor necessitated a third operation in March 1982. The patient died in the next month. Family histories did not show any evidence of von Recklinghausen's disease, and neither did the patient have any clinical stigmata of this disease.  相似文献   
993.
To examine the possible role of transscleral outflow routes, enucleated human and porcine eyes underwent noncontact neodymium:yttrium aluminum garnet (Nd:YAG) laser cyclophotocoagulation 3 mm posterior to the limbus. Pars plana lesions were verified histologically. The eyes were perfused with saline solution at 50 mm Hg perfusion pressure, placing the tip of the needle into the hyaloid orbicular space. The outflow facility was 0.072 microliter/min/mm Hg in paired controls and 0.105 microliter/min/mm Hg in human lasered eyes, a difference of 31%. In porcine eyes the difference was 43%. Since concepts of aqueous production, impaired circulation, and inflammation do not apply to enucleated eyes, the increase may be related to pars plana transscleral flow facilitated by disruption of the neuroepithelial barrier.  相似文献   
994.
An 80-year-old man was evaluated for an epibulbar tumor on a phthisical eye. The initial biopsy diagnosis of the epibulbar tumor was poorly differentiated neoplasm. Exenteration of the phthisical eye and orbital contents showed an extensive pleomorphic adenocarcinoma of the nonpigmented epithelium of the ciliary body with extraocular extension. There was evidence of hyaluronic acid secretion and immunohistochemical staining was strong for vimentin, focal for epithelial membrane antigen and S-100 protein, and weak for neuron-specific-enolase. Electron microscopy demonstrated desmosomes between tumor cells, areas of thick, multilaminar basement membrane production surrounding individual tumor cells, and occasional intracytoplasmic intermediate filaments.  相似文献   
995.
The intraocular pressure and the anteroposterior length of the eye are of great clinical importance for the diagnosis and management, before and after surgery, of congenital glaucoma. It is well-known that normal intraocular pressure in children is different from the normal levels in adults. We performed measurements of intraocular pressure and axial length in 141 children who had been admitted for eye problems other than glaucoma. The intraocular pressures were measured with the Perkins hand-held applanation tonometer at the beginning of general anesthesia. Simultaneously, A-scan ultra-sound measurements of the axial lengths of the eyes were made. In 10 children under the age of two years, the intraocular pressure was 11.85 +/- 1.35 mmHg. In 79 children from two to seven years, the intraocular pressure was 12.80 +/- 1.73 mmHg. In 52 children from seven to 15 years, the intraocular pressure was 13.31 +/- 1.79 mmHg. The axial lengths of the eyes in children under the age of two years, from two to seven years, and from seven to 15 years, were 21.31 +/- 0.97 mm, 22.04 +/- 0.92 mm, and 23.22 +/- 1.00 mm, respectively. These results were considered to be guidelines for measuring intraocular pressure and axial length in children suspected of having congenital glaucoma. The differences of intraocular pressures stated by other authors are due to early measurement of the intraocular pressure at the beginning of general anesthesia.  相似文献   
996.
This study has shown that the retinae of Prototherian (egg-laying) mammals possess two neuronal types that are present in non-mammalian retinae, but absent or morphologically different in the retinae of Eutherian (placental) mammals. First, endogenous serotonin-like immunoreactivity has been localized in a population of presumptive amacrine cells in the platypus retina, the first such report in a mammalian retina. Second, the protein kinase C-immunoreactive (PKC-IR) bipolar cells in the echidna retina appear similar to the PKC-IR bipolars in the chicken retina, in that their dendrites give rise to a Landolt's club and their axons are multistratified. By contrast, the PKC-IR rod bipolar cells in the rabbit and in the brushtail possum, a Metatherian (marsupial) mammal, have no Landolt's clubs and their axons form terminal lobes in the innermost stratum of the inner plexiform layer.  相似文献   
997.
The study examines whether the order of administering 2 doses of quinpirole (0.5 and 8 mg/kg) affects the development of behavioral sensitization, as measured by the amount of forward progression and mouthing. Results show that injection of the high dose greatly enhances the subsequent locomotor response to the low dose of quinpirole, but not vice versa. Mouthing activity is not influenced by order of administration but is significantly greater at the higher dose of quinpirole. The present findings are consistent with a hypothesis that locomotor sensitization involves down-regulation of a D1 tone normally inhibitory to D2 locomotor activation.  相似文献   
998.
The influence of beta-blockers in short- and long-term application on the epithelium of the cornea was studied in rabbits with intact tear film, concentrating not on the completeness of the drug group but on general differences. The new unpreserved beta-blocker timolol was compared on an exemplary level with the following beta-blocker formulas: (1) beta-blocker eye drops with 0.01% of the preservative benzalkonium chloride; (2) beta-blocker eye drops with 0.005% of the preservative benzalkonium chloride, and (3) beta-blocker eye drops with 0.004% of the preservative benzalkonium chloride and the tear substitute polyvinyl alcohol. Exposure time in the short-term test was 30 min, in long-term tests the time was 24 weeks. Any cell damages observed were of only minor importance and rarely of clinical relevance; however, it could be shown that micromorphological cell reactions differed as a function of the preservative concentration. Complete absence of preservatives causes no difference in micromorphologically relevant changes in comparison with the control group. Drugs without preservatives are thus a meaningful alternative for patients with allergies, sensitive eyes or existing impairment of the precorneal film.  相似文献   
999.
Efficacy of diltiazem in the treatment of diffuse oesophageal spasm   总被引:1,自引:1,他引:0  
Calcium antagonist relax smooth muscle, a possible useful concept in treatment of diffuse oesophageal spasm. Therefore the effects of oral diltiazem (60 mg t.d.s.) and placebo were compared in eight patients with diffuse oesophageal spasm in a 10-week double-blind crossover study. The patients recorded the severity of chest pain and/or dysphagia in daily pain diaries using visual analogue scales. Chest pain index and dysphagia index were calculated by multiplying frequency with daily intensity of each individual symptom. When compared to placebo, diltiazem did not significantly change the overall dysphagia index and chest pain index. An individual sizeable reduction of dysphagia was attained on diltiazem in four out of six patients and in six out of eight patients suffering from chestpain. Side effects were not seen during diltiazem therapy. Diltiazem, in our study, did not yield in a significant improvement of symptoms in diffuse oesophageal spasm. Diltiazem, however, can offer relief in selected individual patients suffering from diffuse oesophageal spasm.  相似文献   
1000.
A series of 5-alkyl-5-phenylbarbituric acid analogues were shown to be potent hypolipidemic agents in rats and mice at 20 mg/kg/day. This dose is lower than that required for hypolipidemic activity for clofibrate and nicotinic acid derivatives in rodents and man. These new derivatives reduced both serum cholesterol and triglyceride levels in rodents by either the oral or intraperitoneal route of administration. Previous studies have demonstrated that similar heterocyclic compounds, i.e. cyclic imides, glutarimides and hydantoins are potent hypolipidemic agents in rodents. The barbituric acid derivatives probably interfered with de novo synthesis of cholesterol and fatty acids in the early steps since the agents inhibit the activities of ATP-dependent citrate lyase and acetyl-CoA synthetase. Triglyceride synthesis may be blocked since the agents inhibited the rate limiting enzyme, sn-glycerol-3-phosphate-acyl-transferase. Rat tissue lipids especially cholesterol and triglycerides were reduced after 14 days treatment. Fecal lipids were increased in cholesterol and phospholipid content by selected compounds. The rat serum lipoprotein after 14 days drug administration showed reduced VLDL-cholesterol and HDL-triglyceride contents. The modulation of the lipid content of the serum lipoproteins by the barbituric acids suggest that these agents may be helpful in treating clinical hyperlipidemic disease states.  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