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   863510篇
  免费   70637篇
  国内免费   1843篇
耳鼻咽喉   12808篇
儿科学   24654篇
妇产科学   25125篇
基础医学   124416篇
口腔科学   25517篇
临床医学   75457篇
内科学   164803篇
皮肤病学   16998篇
神经病学   70215篇
特种医学   35287篇
外国民族医学   171篇
外科学   136425篇
综合类   24617篇
现状与发展   2篇
一般理论   264篇
预防医学   66929篇
眼科学   20536篇
药学   64796篇
中国医学   1595篇
肿瘤学   45375篇
  2018年   7358篇
  2015年   7750篇
  2014年   11140篇
  2013年   16819篇
  2012年   22772篇
  2011年   23903篇
  2010年   13892篇
  2009年   13095篇
  2008年   22636篇
  2007年   24682篇
  2006年   24557篇
  2005年   24191篇
  2004年   23745篇
  2003年   22878篇
  2002年   21973篇
  2001年   35884篇
  2000年   36514篇
  1999年   30944篇
  1998年   9235篇
  1997年   8562篇
  1996年   8492篇
  1995年   8014篇
  1994年   7749篇
  1992年   26693篇
  1991年   26122篇
  1990年   25654篇
  1989年   24708篇
  1988年   23260篇
  1987年   22924篇
  1986年   21779篇
  1985年   21118篇
  1984年   16399篇
  1983年   14008篇
  1982年   8872篇
  1981年   8208篇
  1980年   7676篇
  1979年   16751篇
  1978年   12126篇
  1977年   10190篇
  1976年   9338篇
  1975年   10156篇
  1974年   12648篇
  1973年   12146篇
  1972年   11548篇
  1971年   10692篇
  1970年   10223篇
  1969年   9914篇
  1968年   8905篇
  1967年   8236篇
  1966年   7656篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Abstract Perioscan requires a plaque sample to detect the presence of enzymes capable of degrading N-benzoyl-DL-arginine-2-naphthylamide (BANA) from relatively few anaerobic periodontal pathogens. Periocheck assays the presence of neutral proteases in crevicular fluid. The aim of this study was to compare these test kits with traditional clinical methods of detecting periodontal disease and to monitor the ability of the kits to reflect the response to initial therapy. 19 patients with moderately severe chronic periodontitis were seen before and after a course of oral hygiene and root instrumentation consisting of 4 appointments. Clinical measurements and test assays were collected at 5 diseased sites and 2 healthy sites in each subject. Complete data from 125 sites were available for statistical analysis. At baseline Periocheck had a sensitivity of 88% and a specificity of 61% whereas Perioscan had a sensitivity of 99% and a specificity of 55%, when related to the clinical diagnosis. A composite clinical assessment, based on improvement or deterioration of one whole unit change of the subjective clinical indices and 2mm changes or greater in probing depth or probing attachment level, revealed 75 sites which improved following treatment, whereas 45 sites did not change and 5 sites deteriorated. The probability that the tests agreed with the clinical outcome after treatment, was calculated as 50.4% for Periocheck and 52% for Perioscan. The diagnostic kits did not reliably reflect the clinical assessment of periodontal disease in the cross sectional study, or the outcome following treatment.  相似文献   
82.
83.
84.
The efficiency of two methods of detection of translocations induced in mouse stem cell spermatogonia by X-ray doses of 2, 5 and 7 Gy was compared: classical multivalent analysis at diakinesis-metaphase I of meiosis and observation via fluorescencein situ hybridization analysis of mitotic or meiotic stages. Specific DNA libraries for chromosomes 1, 11 and 13 were used. The results obtained indicate that (a) chromosomes 1, 11 and 13 are more involved in multivalent formation than expected on the basis of DNA content and (b) if the mitotic FISH analysis data are corrected for the observed over-representation, the frequencies of induced translocations are similar to those recorded in the classical multivalent studies, suggesting equal scoring efficiencies in both systems.  相似文献   
85.
Gonadoblastoma, a rare gonadal neoplasm, presents most frequently in phenotypic female or phenotypically male patients with dysgenetic gonads or undescended testes. To date, only 2 cases of gonadoblastoma have been reported in anatomically normal male patients with scrotal testes. Both of these patients presented with testicular masses and germ cell tumors. We report a case of a genotypically and phenotypically normal, fertile man with descended testes who on evaluation for chronic orchialgia had a gonadoblastoma unaccompanied by a germ cell neoplasm. The tumor was nonpalpable and was initially discovered on scrotal ultrasound.  相似文献   
86.
The fate of skin allografts exchanged among heterozygous and homozygous gynogenetic common carp siblings, and among newly developed inbred strains and F1 hybrids, is described. Heterozygous gynogenetic offspring were produced by fertilizing eggs with UV-irradiated sperm and by treating the resulting zygote with a cold shock (0 degree C, 45 min). The temperature shock causes retention of the second polar body, which allows the eggs to develop into normal diploid fry. Homozygous gynogenetic offspring were similarly produced by using a heat shock (40 degrees C, 2 min), which suppresses the first mitotic division. Skin allografts exchanged among heterozygous gynogenetic carp exhibited prolonged survival, with some allografts (21.8%) surviving for over 28 days. Furthermore, a strong histocompatibility locus was seen to segregate in this group. In contrast, skin allografts exchanged among homozygous gynogenetic siblings were all rejected within 14 days (MST 9.4 days). New homozygous inbred strains, designated JJ and MM, were produced by gynogenetic reproduction of homozygous female carps, while F1 hybrids were produced by crossing of these homozygous females with homozygous male siblings. All grafts exchanged among members of the same strain were permanently accepted. Likewise grafts from homozygous strain members were accepted by fish from the related F1-hybrids, while the reverse grafts were rejected. These results provide evidence for the idea that in the carp histocompatibility genes exist at least one major locus and multiple minor loci, which are codominantly expressed.  相似文献   
87.
Bladder mucosa in urethral reconstructions   总被引:6,自引:0,他引:6  
  相似文献   
88.
Effects of hypothermia on testicular ischemia   总被引:14,自引:0,他引:14  
The ischemic effects of prolonged testicular torsion have been well documented; however, prevention or arrest of the damaging effects of prolonged ischemia has been incompletely studied. Two groups of Sprague-Dawley rats were subjected to varying lengths of bilateral testicular ischemia. Group I underwent normothermic ischemia for two, four, and six hours. Likewise, Group II underwent similar time periods of ischemia, however, after thirty minutes of normothermic ischemia the scrotum of each animal was placed into an ice bath maintained at 4C. Two weeks postoperatively, bilateral orchiectomy was performed. Histology of the testes of the two groups was compared. Neither group revealed significant destruction of the germinal epithelium after two hours of ischemia. Group I revealed only 25% preservation of the germinal epithelium at four hours and only 8% preservation at six hours of ischemia. In contrast, Group II which received ice showed 90% preservation of germinal epithelium at four hours and 85% preservation at six hours of ischemia. We conclude that external ice application significantly preserves seminiferous tubules at four and six hours of ischemic injury in the rat testicle.  相似文献   
89.
Patient history and clinical examination are important for the diagnosis of degenerative joint disease. Here the typical statements of a patient suffering from early osteoarthritis are described and, as far as possible, explained. The joint in question must be systematically examined. Furthermore, the neighboring joints and soft-tissue structures, i.e., muscles, tendons etc., should be examined and evaluated with respect to their importance in hindering the functional chain. The neuroreflectory mechanisms involved herein are described.  相似文献   
90.
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