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   25698篇
  免费   2546篇
  国内免费   1410篇
耳鼻咽喉   220篇
儿科学   352篇
妇产科学   184篇
基础医学   2690篇
口腔科学   575篇
临床医学   2852篇
内科学   3720篇
皮肤病学   486篇
神经病学   1466篇
特种医学   1246篇
外国民族医学   5篇
外科学   3712篇
综合类   4286篇
现状与发展   4篇
一般理论   3篇
预防医学   1842篇
眼科学   552篇
药学   2249篇
  33篇
中国医学   1226篇
肿瘤学   1951篇
  2024年   95篇
  2023年   418篇
  2022年   987篇
  2021年   1348篇
  2020年   1122篇
  2019年   870篇
  2018年   895篇
  2017年   857篇
  2016年   847篇
  2015年   1218篇
  2014年   1419篇
  2013年   1619篇
  2012年   2240篇
  2011年   2231篇
  2010年   1608篇
  2009年   1346篇
  2008年   1532篇
  2007年   1518篇
  2006年   1392篇
  2005年   1203篇
  2004年   970篇
  2003年   972篇
  2002年   758篇
  2001年   463篇
  2000年   314篇
  1999年   213篇
  1998年   156篇
  1997年   133篇
  1996年   105篇
  1995年   91篇
  1994年   91篇
  1993年   55篇
  1992年   66篇
  1991年   46篇
  1990年   37篇
  1989年   35篇
  1988年   32篇
  1987年   42篇
  1986年   46篇
  1985年   37篇
  1984年   26篇
  1983年   22篇
  1982年   24篇
  1981年   21篇
  1980年   21篇
  1979年   21篇
  1978年   11篇
  1977年   9篇
  1976年   8篇
  1957年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Human endometrial stromal cells (ESC) can produce a variety of chemokines, especially after inflammatory stimulation. Interferon-gamma-inducible protein-10 (IP-10) is a potent chemoattractant for lymphocytes, and belongs to the family of non-ELR CXC chemokines. The expression of IP-10 in ESC after stimulation with interferon-gamma (IFN-gamma), interleukin-1 beta (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), or lipopolysaccharide (LPS) was evaluated using an enzyme-linked immunosorbent assay and Northern blot analysis. A small amount of IP-10 protein was detected in the culture media of unstimulated ESC. The expression of IP-10 mRNA was detected in ESC. IFN-gamma, IL-1 beta, TNF-alpha and LPS significantly stimulated the expression of IP-10 mRNA and protein in ESC. These results suggest that the production of IP-10 by ESC is regulated by inflammatory mediators. The modulation of IP-10 concentrations in the local environment may contribute to the normal and pathological processes of human reproduction by regulating leukocyte trafficking in the endometrium.  相似文献   
22.
Mitomycin (MMC), like many antineoplastic drugs, induces a predictable, dose-related, bone marrow depression in man and laboratory animals; this change is generally reversible. However, there is evidence that MMC may also cause a late-stage or residual bone marrow injury. The present study in female CD-1 mice investigated the haematological and bone marrow changes induced by MMC in a repeat dose study lasting 50 days. Control and MMC-treated mice were dosed intraperitoneally on eight occasions over 18 days with vehicle, or MMC at 2.5 mg/kg, autopsied (n = 6-12) at 1, 7, 14, 28, 42 and 50 days after the final dose and haematological changes investigated. Femoral nucleated bone marrow cell counts and levels of apoptosis were also evaluated and clonogenic assays carried out; serum levels of FLT3 ligand (FL) were assessed. At day 1 post-dosing, MMC induced significant reductions in RBC, Hb and haematocrit (HCT) values, and there were decreases in reticulocyte, platelet, and femoral nucleated cell counts (FNCC); neutrophil, lymphocyte and monocyte values were also significantly reduced. On days 7 and 14 post-dosing, all haematological parameters showed evidence of a return towards normal values, but at these times, and at day 28, values for RBC and FNCC remained significantly reduced in comparison with controls. At days 42 and 50 post-dosing, many haematological parameters in MMC-treated mice had returned to control levels; however, there remained evidence of late-stage effects on RBC, Hb and HCT values, and FNCC also continued to be significantly decreased. Results for granulocyte-macrophage colony-forming units and erythroid colonies showed a profound decrease immediately post-dosing, but a return to normal values was evident at day 50. Serum FL concentrations demonstrated very significant increases in the immediate post-dosing period, but a return to normal was seen at day 50 post-dosing; a relatively similar pattern was seen in the number of apoptotic femoral marrow nucleated cells. The histopathological examination of kidney tissues from MMC animals at day 42 and 50 post-dosing showed evidence of hydronephrosis with cortical glomerular/tubular atrophy and degeneration. It is therefore concluded that MMC administered on eight occasions over 18 days to female CD-1 mice at 2.5 mg/kg induced profound changes in haematological and bone marrow parameters in the immediate post-dosing period with a return to normal levels at day 50 post-dosing; however, there was evidence of mild but significant late-stage/residual effects on RBC and FNCC, and on cells of the erythroid lineage in the bone marrow.  相似文献   
23.
双歧杆菌对早产儿食道pH值的影响及临床意义   总被引:2,自引:0,他引:2  
目的为探讨双歧杆菌对早产儿食道pH值的影响,及其对早产儿易发生的消化道疾病的防治意义。方法我们采用便携式24hpH值自动记录仪,对61例早产儿进行了食道pH值的动态监测。结果口服双歧杆菌活菌制剂组的30例早产儿,食道pH值明显高于未服药的对照组,t=2.4093,P<0.05。总pH值<4的时间占总观察时间的百分比显著小于对照组。并且治疗组发生消化道疾患的人数也较对照组少。结论早产儿口服双歧杆菌活菌制剂可以减少胃食道反流等消化道疾病的发生。  相似文献   
24.
The early experience is reported here of the use of Intra-operative frozen-section service by telepathology using the Integrated Service Digital Network (ISDN), a commercially available system that is being connected between the Department of Pathology of Tottori University and Matsue City Hospital, a distance of 30 km. The transfer rate is currently 64kbit/s. The frozen-section service was conducted for a total of 117 tissue specimens (organs) from 100 patients between August 1993 and May 1995. The average time taken for examination of each specimen of frozen section was 13min, ranging between 2 and 42min. The average number of transmitted Images was 6.2. Six cases necessitated more than 11 transmitted Images to make a diagnosis, while 13 cases could be diagnosed from two images only. Correct and permissible diagnoses were obtained in 109 (93.2%) out of 117 specimens when comparing the telepathology diagnosis with that of direct microscopy. Improper or misdiag-nosis was made for eight cases (specimens), which were misinterpreted as papillary carcinoma in Basedow's disease, adenoma and hyperplasia in two pheochromocytomas, solid-tubular carcinoma in phyilodes tumor, mastopathy in invasive carcinoma, metastatic carcinoma in astrocytoma, follicular lymphoma in reactive hyperplasia, and lymphadenitis in follicular lymphoma. in retrospect, diagnosis of these cases should have been deferred. From the results, it was concluded that the Intraoperatlve frozen-section service by telepathology may be a worthwhile substitute for hospitals with limited accessibility to local pathology service, in spite of pitfalls in some cases. Well prepared, high-quality frozen sections, sufficient verbal communication with surgeons, and a rather conservative attitude on the part of a well-trained pathologist seem to be the essential Ingredients for reaching an accurate decision when using telepathology.  相似文献   
25.
26.
27.
Horimoto  T.  Limcumpao  J. A.  Xuan  X.  Ono  M.  Maeda  K.  Kawaguchi  Y.  Kai  C.  Takahashi  E.  Mikami  T. 《Archives of virology》1992,126(1-4):283-292
Summary Heterogeneity of 9 feline herpesvirus type 1 (FHV-1) strains consisting of the prototype C27 strain, one French isolate, six Japanese isolates, and the attenuated vaccine F2 strain was examined by biological, immunological, and molecular biological methods. No significant difference was observed in virus growth and antigenic properties among the strains in Crandell feline kidney cell cultures. Hemagglutination activity was also detected in all extracts of cells infected with each strain. However, in immunoblot analysis, a virus-structural immunogenic protein with an Mr of 36 kDa was lacking in 2 strains, one of which was the vaccine F2 strain, whereas the other immunogenic proteins including three kinds of major glycoproteins were detected in all strains without differences in electrophoretic mobilities. Furthermore, when restriction endonuclease analysis was performed to examine the genomic heterogeneity of strains, the cleavage patterns with the enzymeMluI showed a genomic heterogeneity between wild and vaccine strains. In contrast, only a slight variation in the sizes of some fragments was shown with most of the 7 other enzymes used. These results indicated that the lack of the 36 kDa protein and theMluI cleavage pattern could be used as markers of the vaccine F2 strain. The specific markers are important not only to control the quality of the vaccine but also to evaluate the vaccine immunity in FHV-1 infection in cats.  相似文献   
28.
Weak transcranial direct current stimulation (tDCS) of the human motor cortex results in excitability shifts which occur during and after stimulation. These excitability shifts are polarity-specific with anodal tDCS enhancing excitability, and cathodal reducing it. To explore the origin of this excitability modulation in more detail, we measured the input–output curve and motor thresholds as global parameters of cortico-spinal excitability, and determined intracortical inhibition and facilitation, as well as facilitatory indirect wave (I-wave) interactions. Measurements were performed during short-term tDCS, which elicits no after-effects, and during other tDCS protocols which do elicit short- and long-lasting after-effects. Resting and active motor thresholds remained stable during and after tDCS. The slope of the input–output curve was increased by anodal tDCS and decreased by cathodal tDCS. Anodal tDCS of the primary motor cortex reduced intracortical inhibition and enhanced facilitation after tDCS but not during tDCS. Cathodal tDCS reduced facilitation during, and additionally increased inhibition after its administration. During tDCS, I-wave facilitation was not influenced but, for the after-effects, anodal tDCS increased I-wave facilitation, while cathodal tDCS had only minor effects. These results suggest that the effect of tDCS on cortico-spinal excitability during a short period of stimulation (which does not induce after-effects) primarily depends on subthreshold resting membrane potential changes, which are able to modulate the input-output curve, but not motor thresholds. In contrast, the after-effects of tDCS are due to shifts in intracortical inhibition and facilitation, and at least partly also to facilitatory I-wave interaction, which is controlled by synaptic activity.  相似文献   
29.
30.
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