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   932115篇
  免费   66429篇
  国内免费   1346篇
耳鼻咽喉   12971篇
儿科学   24378篇
妇产科学   23237篇
基础医学   132899篇
口腔科学   28250篇
临床医学   80549篇
内科学   183436篇
皮肤病学   19232篇
神经病学   72183篇
特种医学   36825篇
外国民族医学   79篇
外科学   152115篇
综合类   18055篇
现状与发展   1篇
一般理论   234篇
预防医学   61765篇
眼科学   21315篇
药学   72547篇
  3篇
中国医学   2162篇
肿瘤学   57654篇
  2018年   8974篇
  2017年   7028篇
  2016年   7763篇
  2015年   8865篇
  2014年   11991篇
  2013年   17504篇
  2012年   24106篇
  2011年   25048篇
  2010年   14818篇
  2009年   14271篇
  2008年   24609篇
  2007年   25694篇
  2006年   26483篇
  2005年   25428篇
  2004年   24568篇
  2003年   23612篇
  2002年   23148篇
  2001年   54731篇
  2000年   56552篇
  1999年   46954篇
  1998年   10731篇
  1997年   9467篇
  1996年   9594篇
  1995年   8927篇
  1994年   8280篇
  1993年   7593篇
  1992年   35501篇
  1991年   33932篇
  1990年   32757篇
  1989年   31889篇
  1988年   29012篇
  1987年   28257篇
  1986年   26296篇
  1985年   25146篇
  1984年   17834篇
  1983年   15141篇
  1982年   7797篇
  1981年   6771篇
  1979年   15781篇
  1978年   10598篇
  1977年   9052篇
  1976年   7873篇
  1975年   8629篇
  1974年   10471篇
  1973年   9868篇
  1972年   9359篇
  1971年   8854篇
  1970年   8428篇
  1969年   7924篇
  1968年   7200篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
We used the laser flowmeter to measure and compare the effect of nitroglycerin (TNG), trimetaphan (TMP) and prostaglandin E1 (PGE1) on the blood flow of operating field during hypotension induced by each drug. The study was done in 33 patients (TNG:13, TMP:13 and PGE1:7) anesthetized with modified NLA who underwent radical mastectomy. We put the probe of the laser flowmeter on the skin of the opposite breast to the operating field and measured the skin blood flow change. Measurements were made before and during hypotension induced by each drug. TMP-induced hypotension decreased blood flow significantly (P less than 0.05), but TNG and PGE1 had no significant effect. Intraoperative blood losses of TNG and PGE1 group were not significantly larger than that of TMP group. From this study we conclude that TNG, TMP and PGE1 can dry the operating field and decrease intraoperative blood loss similarly. Therefore we should choose the drugs to induce hypotension considering the effect of the drug on blood flow of the important organs and each patient's complications.  相似文献   
972.
A 86-year-old man was admitted to our hospital because of swallowing disturbance and deterioration of consciousness. He had been aware of hearing disturbance on the right side for twelve months. Computed tomography (CT) scan demonstrated an inhomogeneous hyperdense mass lesion, 3.2 X 2.3 cm in size, at the right cerebello-pontine angle, and ventricular enlargement with intraventricular hemorrhage. Skull tomogram revealed destructive enlargement of the right jugular foramen. The angiogram showed avascular mass with elevation of anterior inferior cerebellar artery, and downward shift of posterior inferior cerebellar artery. Operative and histological findings were compatible with glossopharyngeal neurinoma of Antoni type A dominance. This tumor had numerous abnormal vessels probably causing massive hemorrhage. Only fifteen cases of intracranial neurinoma with symptomatic hemorrhage have been reported in the world literature. This case is reported as the sixteenth one and the first glossopharyngeal neurinoma among them. Possible etiology of such hemorrhage is discussed.  相似文献   
973.
The dynamic and functional state of soda lime can be more precisely assessed by measuring changes in wall temperatures of the absorption chambers rather than observing color change of the soda lime granules. We demonstrated in this report that the liquid crystal thermometer is an inexpensive and reliable measuring device for this purpose.  相似文献   
974.
We retrospectively reviewed 38 patients with primary penile squamous cell carcinoma (stage 1 in 22, stage 2 in 7 and stage 3 in 9) who were treated in our institution from 1963 through 1987. The incidence of regional nodal metastasis was correlated with tumor category, local infiltration and tumor grade. The incidence rate of nodal metastasis of G2 and G3 tumors was statistically higher than that of G1 tumors. Of 27 patients initially treated by radiotherapy and/or chemotherapy, 11 patients achieved complete response. G1 tumors and T1 to 2 tumors had such high response rates as 58 and 50 per cent, respectively, but 5 patients (45 per cent) had local recurrence at an average of 74 months after initial treatment. The 5-year survival rates of over-all, stage 1, 2 and 3 were 73, 90, 75 and 25 per cent, respectively. Patients with stage 3 disease had a statistical lower survival rate than those with stage 1 or 2 disease. Among 13 patients with regional nodal metastasis, none with G2 tumor survived three years, although 3 patients (60 per cent) of those with G1 tumor survived five years. These results suggest that tumor grade is the most prognostic factor for the regional nodal metastasis, the response of conservative treatment and the survival of metastasized patients.  相似文献   
975.
The effects of chronic ethanol administration on vitamin B-6 metabolism were studied in female Long-Sleep (LS) and Short-Sleep (SS) mice. Animals were fed an ethanol containing liquid diet (AIN-76) for four weeks. Concentration of ethanol in the diet increased from 10 to 25% ethanol-derived calories (EDC) during weeks 1-3 and was maintained at 30% EDC for 1 additional week. We measured concentrations of pyridoxal 5'-phosphate (PLP) in plasma, erythrocytes and whole blood, and liver and brain PLP and pyridoxamine 5'-phosphate (PMP) in ethanol-fed and pair-fed control mice. Chronic ethanol administration significantly increased PMP and total (PLP + PMP) levels in the liver of SS mice. In LS mice ethanol feeding significantly decreased PMP and total (PLP + PMP) levels in the brain, but these values were still within normal limits. These results suggest that both control and ethanol-containing liquid diets are nutritionally adequate with respect to vitamin B-6, and that chronic ethanol administration does not adversely affect vitamin B-6 metabolism in adult mice.  相似文献   
976.
Tracheal implants have served as an important experimental pathology tool with which to study the toxic and/or carcinogenic effects of chemicals upon upper respiratory tract epithelium. Initial studies with this method utilized heterotopic rat tracheal transplants which were exposed to compounds of interest, and assessed for toxic and/or carcinogenic endpoints. Grafts containing rodent tissue have proved useful for studying the cellular and biochemical features of neoplastic progression at different time intervals following in vivo exposure to carcinogens. More recent studies have utilized epithelial denuded tracheal implants inoculated with respiratory cell populations, and xenografted into immunodeficient nu/nu mice. This technique permits the study of airway epithelium from a variety of species, including man. The advent of molecular pathology techniques such as in situ hybridization will further expand the uses of tracheal implant technology for studies with xenografted human tissues. Such implants should prove useful for the examination of species- and tissue-specific characteristics of growth and differentiation by providing a bridge between cell culture and whole animal studies.  相似文献   
977.
978.
Immunophenotyping of mononuclear leukocytes was performed in renal tissue obtained from 69 patients with different forms of glomerulonephritis (GN) and from ten donors' kidneys for transplantation used as controls. A panel of monoclonal antibodies was used in the immunoperoxidase technique on frozen sections to define B- and T-lymphocyte subpopulations, NK cells and monocytes/macrophages, as well as the expression of HLA class II antigens-DQ, -DR and -DP. Quantification of labelled leukocytes revealed a significant increase of CD4+ and CD8+ T-cells in glomeruli of rapidly progressive glomerulonephritis, membranoproliferative glomerulonephritis and even of focal gomerulosclerosis. The number of glomerular monocytes/macrophages was significantly increased only in rapidly progressive glomerulonephritis, whereas in membranoproliferative glomerulonephritis it was decreased. No differences to normal tissue were detected in glomeruli for all other types of inflammatory cells. Interstitial cells were mostly T-lymphocytes in all forms of glomerulonephritis. In all groups the CD4+/CD8+ ratio was somewhat greater than 1 and even about 2 in rapidly progressive glomerulonephritis. Only in particular case was this ratio inversed. High expression of HLA class II antigens was observed on interstitial mononuclear leukocytes, as a sign of their activation. The excess of HLA-DQ-positive cells over the sum of CD14+ and CD20+ cells provides evidence not only for presence of activated T-lymphocytes but perhaps also for accumulation of renal dendritic cells in the interstitium in glomerulonephritis associated with interstitial infiltration.  相似文献   
979.
Summary The authors report the third published case of a Lhermitte-Duclos disease diagnosed preoperatively with the help of MRI, stressing its possible extension beyond the limits of the posterior fossa. The pertinent literature is reviewed concerning the clinical and radiological picture of this disease, as well as the different pathogenic hypothesis.  相似文献   
980.
Summary The distribution of the enzyme nitric oxide synthase (NOS) was investigated at the ultrastructural level in synaptic structures of the hippocampal formation in relation to long-term potentiation (LTP), based on the histochemical NADPH-diaphorase (NADPH-d) staining with the tetrazolium salt BSPT. BSPT-formazan, the osmiophilic reaction product, was found to be selectively distributed and predominantly attached to membranes of the endoplasmic reticulum. In synaptic regions mainly the presynaptic sides showed labeling. Although several groups have demonstrated a principal involvement of NO in the LTP-mechanism, we found only a low, statistically insignificant increase in NADPH-d stained presynaptic areas of the dentate gyrus, where LTP was evoked. Postsynaptic elements also did not show any noticeable differences. Based on the present results, the predominantly presynaptic localization of NOS should be preferably considered in models describing a functional role of NO in LTP formation, despite the fact that we failed to reveal any indications for an LTP-related change in synaptically located NADPH-d.  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