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   3327篇
  免费   182篇
  国内免费   56篇
耳鼻咽喉   110篇
儿科学   15篇
妇产科学   48篇
基础医学   681篇
口腔科学   58篇
临床医学   308篇
内科学   811篇
皮肤病学   86篇
神经病学   237篇
特种医学   125篇
外科学   277篇
综合类   14篇
现状与发展   1篇
预防医学   119篇
眼科学   38篇
药学   326篇
中国医学   53篇
肿瘤学   258篇
  2023年   11篇
  2022年   80篇
  2021年   124篇
  2020年   55篇
  2019年   80篇
  2018年   110篇
  2017年   68篇
  2016年   104篇
  2015年   140篇
  2014年   148篇
  2013年   198篇
  2012年   315篇
  2011年   307篇
  2010年   202篇
  2009年   156篇
  2008年   239篇
  2007年   191篇
  2006年   173篇
  2005年   158篇
  2004年   140篇
  2003年   119篇
  2002年   99篇
  2001年   95篇
  2000年   67篇
  1999年   47篇
  1998年   19篇
  1997年   14篇
  1996年   8篇
  1995年   4篇
  1994年   9篇
  1993年   3篇
  1992年   9篇
  1991年   11篇
  1990年   12篇
  1989年   5篇
  1988年   8篇
  1987年   5篇
  1986年   4篇
  1985年   4篇
  1984年   2篇
  1983年   1篇
  1981年   1篇
  1979年   2篇
  1977年   1篇
  1976年   1篇
  1973年   7篇
  1972年   2篇
  1969年   3篇
  1968年   4篇
排序方式: 共有3565条查询结果,搜索用时 62 毫秒
1.
The objective of this study is to compare the effects of three different anesthetic combinations on the electroretinogram in the same animals under similar laboratory conditions. Thiopental–isoflurane (TI), medetomidine–ketamine (MK), and xylazine–ketamine (XK) were used on each of 12 healthy miniature schnauzer dogs (MS) with a period of at least 3 weeks in between subsequent anesthesia protocols, using the Dog Standard Protocol. The scotopic ERGs consisted of scotopic low stimulus strength (S) responses designated S1, S2, S3, S4, and S5, at 1, 5, 10, 15, and 20 min after dark adaptation, respectively, and scotopic standard stimulus strength (S-ST) responses. The photopic ERGs consisted of a photopic single flash (P) response and 31 Hz flicker (P-FL) responses. For S-ST (2.5 cd s/m2), the amplitude of the a-wave using TI was significantly lower than that using MK (adjusted P = 0.05) and XK (adjusted P = 0.03), and the implicit time of the a-wave was significantly shorter than that using MK (adjusted P = 0.04). For P (2.5 cd s/m2), the amplitude of the b-wave using XK was significantly higher than that using MK (adjusted P = 0.01). The implicit times of the b-wave using TI was significantly longer and shorter than that of MK for S1, S2 and P-FL and for S4 and S-ST, respectively, and than that of XK for S2 and P-FL and for S5 and S-ST, respectively. The results of the present study showed that TI affected both the amplitude and the implicit time of the a-wave for S-ST and the implicit time of the b-wave relatively more so than was the case when using XK or MK. Therefore, it appears that either XK or MK could be advantageous to use rather than TI for clinical studies.  相似文献   
2.
Korean hospitals are experiencing an increasing amount of financial difficulty due to government control of hospital rates since national health insurance has been implemented. The decision support system (DSS) was developed to provide cost and revenue information for the services rendered by each department in an effort to reduce costs. This information may be used to identify the causes of financial loss if cost exceeds revenue and to develop budgets for the next year. The DSS was developed using a micromainframe interface approach where the mainframe computer collects and summarises daily cost data and the micro computer allocates the data to each department.  相似文献   
3.
Activated nuclear factor-kappaB (NF-kappaB) and inducible nitric oxide synthase (iNOS) were detected immunohistochemically in pleuropneumonic lungs from 20 pigs naturally infected with Actinobacillus pleuropneumoniae. NF-kappaB was detected mainly in nuclei of inflammatory cells, confirming its activation. Intense immunolabelling for NF-kappaB and iNOS was seen within the lung lesions, but labelling was minimal in unaffected portions of the lung of infected pigs and in normal lung from uninfected (control) pigs. Examination of serial sections from the 20 infected lung samples demonstrated a close association between NF-kappaB and iNOS. This suggests that NF-kappaB plays a key role in triggering the activation of iNOS in porcine pleuropneumonia.  相似文献   
4.
We examined 11 naturally occurring isolates of Ehrlichia equi in horses and two human granulocytic ehrlichiosis agent isolates in California for sequence diversity in three genes. Ehrlichia equi isolates were from Sierra (n = 6), Mendocino (n = 3), Sonoma (n = 1), and Marin (n = 1) counties, and human granulocytic ehrlichiosis (HGE) agent isolates were obtained from Humboldt county. PCR with specific primers for 16S rRNA, 444 Ep-ank and groESL heat shock operon genes successfully produced amplicons for all 13 clinical samples. The 444 Ep-ank gene of the HGE agent and E. equi isolates from northern California is different from the eastern U.S. isolates BDS and USG3. The translated amino acid sequence of the groESL heat shock operon gene fragment is identical among E. equi, the HGE agent, and E. phagocytophila, with the exception of the northern Californian equine CASOLJ isolate. Microheterogeneity was observed in the 16S rRNA gene sequences of HGE agent and E. equi isolates from northern California. These results suggest that E. equi and the HGE agent found in California are similar or identical but may differ from the isolates of equine and human origin found in the eastern United States.  相似文献   
5.
Infradiaphragmatic extralobar pulmonary sequestration is an extremely rare congenital malformation. It is more frequently diagnosed in the antenatal period due to routine ultrasonic examination of the fetus or in the first 6 months of life, though on rare occasions it is discovered incidentally in adults. A 32-yr-old man presenting with epigastric discomfort and fever was referred. Computed tomographic scanning showed that a 16-cm, multiseptated, dumbbell-shaped, huge cystic tumor was located beneath the diaphragm. On the next day, 850 mL of thick yellowish pus was drained by sonography-guided fine needle aspiration for the purpose of infection control and diagnosis, but no microscopic organisms were found in repeated culture studies. Surgical removal of the cyst was performed through thoracoabdominal incision and most of these pathologic lesions were removed but we could not find the feeding arteries or any fistulous tract to surrounding structures. Histopathologic study revealed that it was extralobar pulmonary sequestration and culture study showed that many WBC and necrotic materials were found but there were no microorganisms in the cystic contents. We report the first case of an infected infradiaphragmatic retroperitoneal extralobar sequestration which was administered a staged management and achieved an excellent clinical course.  相似文献   
6.
7.
In our previous study we demonstrated that acupuncture at Shenmen (HT7) points suppressed a decrease of accumbal dopamine (DA) release in ethanol-withdrawn rats. Furthermore, here we found that it inhibited behavioral withdrawal signs of ethanol. In an effort to better understand the mechanisms underlying this inhibition, the potential role of GABA receptor system in acupuncture was investigated. Male Sprague–Dawley rats were treated with 3 g/kg/day of ethanol (20%, w/v) or saline by intraperitoneal injection for 21 days. Following 48 or 72 h of ethanol withdrawal, acupuncture was applied at bilateral HT7 for 1 min. The selective GABAA antagonist bicuculline and the selective GABAB antagonist SCH 50911 were injected intraperitoneally 20 min before acupuncture, respectively. Importantly, suppressive effects of acupuncture on DA deficiency were completely abolished by SCH 50911, but not by bicuculline, whereas ameliorating effects of acupuncture on ethanol withdrawal syndrome were completely blocked either by SCH 50911 or bicuculline. These results suggest that acupuncture at specific acupoint HT7 may normalize the DA release in the mesolimbic system and attenuate withdrawal syndrome through the GABAB receptor system in ethanol-withdrawn rats.  相似文献   
8.
9.
Intramucosal Helicobacter pylori (H. pylori) has been described in biopsy tissues and culture systems. However, the association of intramucosal H. pylori with histopathologic features has not been evaluated. The purpose of this study is to investigate the relationship between intramucosal H. pylori and inflammatory reactions in H. pylori infection. In 113 randomly selected human gastric biopsies and 20 murine stomachs, which were inoculated with SSI every day for a week, immunohistochemical analysis for intramucosal H. pylori was done and correlated with histologic parameters. Electron microscopic examination was done on murine stomachs. H. pylori infection was present in 104 gastric biopsies and 17 murine stomachs. Intraepithelial immunopositivity for H. pylori was detected in 27 of 104 (26%) biopsies and in 11 of 17 (65%) murine stomachs. Lamina proprial immunopositivity for H. pylori was present in 51 of 104 (48%) biopsies. Neutrophil-associated immunopositivity for H. pylori was observed in 22 of 90 (24%) biopsies with H. pylori chronic active gastritis. Lamina proprial and neutrophil-associated immunopositivity for H. pylori correlated significantly with the density of H. pylori and the grade of acute inflammatory reaction in H. pylori gastritis. Intramucosal location of H. pylori itself or its antigen is closely associated with acute inflammatory reactions and may play an important role in establishing a persistent infection in chronic H. pylori gastritis. Furthermore, lamina proprial and/or neutrophil-associated H. pylori appears to be more important than intraepithelial H. pylori in acute inflammatory reactions of H. pylori gastritis.  相似文献   
10.
The marginal zone macrophages of the spleen are implicated in the clearance of polysaccharides, but underlying mechanisms need to be pinpointed. SIGN-R1 is one of five recently identified mouse genes that are homologous to human DC-SIGN and encode a single, external, C-terminal C-type lectin domain. We find that a polyclonal antibody to a specific SIGN-R1 peptide reacts primarily and strongly with a subset of macrophages in the marginal zone of spleen and lymph node medulla. In both sites, SIGN-R1 exists primarily in an aggregated form, resistant to dissociation into monomers upon boiling in SDS under reducing conditions. Upon transfection into three different cell lines, high-mol.-wt forms bearing SIGN-R1 are expressed, as well as reactivity with ER-TR9, a mAb previously described to react selectively with marginal zone macrophages. SIGN-R1-expressing macrophages preferentially sequester dextrans following i.v. injection. Likewise, when phagocytic cells are enriched from spleen and tested in culture, dextran is selectively endocytosed by a subset of very large SIGN-R1(+) cells representing approximately 5% of total released macrophages. Uptake of FITC-dextran by these macrophages in vivo and in vitro is blocked by ER-TR9 and polyclonal anti-SIGN-R1 antibodies. Following transfection with SIGN-R1, cell lines become competent to endocytose dextrans. The dextran localizes primarily to compartments lacking transferrin receptor and the LAMP-1 CD107a panlysosomal antigen. Therefore, SIGN-R1 mediates the uptake of dextran polysaccharides, and it is predominantly expressed in the macrophages of the splenic marginal zone and lymph node medulla.  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