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   12492篇
  免费   628篇
  国内免费   99篇
耳鼻咽喉   64篇
儿科学   187篇
妇产科学   193篇
基础医学   1535篇
口腔科学   155篇
临床医学   759篇
内科学   3683篇
皮肤病学   223篇
神经病学   816篇
特种医学   600篇
外科学   2326篇
综合类   85篇
预防医学   221篇
眼科学   121篇
药学   836篇
  4篇
中国医学   42篇
肿瘤学   1369篇
  2024年   25篇
  2023年   107篇
  2022年   191篇
  2021年   334篇
  2020年   166篇
  2019年   212篇
  2018年   275篇
  2017年   230篇
  2016年   298篇
  2015年   318篇
  2014年   388篇
  2013年   434篇
  2012年   769篇
  2011年   870篇
  2010年   453篇
  2009年   437篇
  2008年   746篇
  2007年   911篇
  2006年   839篇
  2005年   856篇
  2004年   843篇
  2003年   855篇
  2002年   788篇
  2001年   152篇
  2000年   102篇
  1999年   156篇
  1998年   209篇
  1997年   181篇
  1996年   148篇
  1995年   143篇
  1994年   98篇
  1993年   119篇
  1992年   80篇
  1991年   61篇
  1990年   71篇
  1989年   50篇
  1988年   45篇
  1987年   41篇
  1986年   29篇
  1985年   19篇
  1984年   20篇
  1983年   22篇
  1982年   18篇
  1981年   11篇
  1980年   17篇
  1979年   10篇
  1978年   12篇
  1977年   8篇
  1975年   7篇
  1974年   7篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
This study was designed to determine the influence of ileal pouch capacity and anal sphincteric function on the clinical outcome after ileal pouch-anal anastomosis. A total of 24 patients who had undergone ileal pouch-anal anastomosis (J pouch) for ulcerative colitis were studied. The 24-hour stool frequency was found to be inversely correlated with the sensitivity threshold volume (STV), maximal tolerance volume (MTV), and distensibility, but was independent of the maximal resting pressure and maximal squeeze pressure. Patients experiencing nocturnal fecal incontinence had maximal resting pressures that were significantly lower than those of nocturnally continent patients. Among the patients with fecal incontinence, those with frequent soiling had lower resting pressures, STV, and distensibility than the patients with intermittent spotting. In addition, the STV in patients needing nocturnal evacuation were lower than those of patients who did not evacuate after falling asleep. The conclusions are as follows. Both stool frequency and the need for nocturnal pouch evacuation correlated directly with pouch volume. Anal incontinence was more common in patients with low internal sphincteric function. In addition, frequent and gross nocturnal incontinent patients demonstrate a worse function in both the anal sphincter and reservoir than those with intermittent spotting.  相似文献   
32.
Previously unreported effects of tissue storage were recently observed in the authors' experimental magnetic resonance (MR) studies. To evaluate the effect of elapsed time after excision and storage temperature on tissue relaxation time measurements, tissue samples from the liver, pancreas, kidney, testis, spleen, and brain were obtained in rats. T1 and T2 were first measured within 5 minutes of excision, and between subsequent measurements, tubes were kept in a water bath at 40°C, at room temperature (28°C), or in an ice bath (4°C). Cellular and organellar integrity was assessed with electron microscopy and correlated with the MR findings. At 40°C (20-MHz spectrometer), the T1 of liver decreased from 280 msec ± 8 to 212 msec ± 10 during the first 60 minutes; the T1 of pancreas decreased from 276 msec ± 3 to 208 msec ± 2. Other tissues showed less than a 5% decrease in T1. T2 changes were smaller than T1 changes in all tissues. Electron microscopy of pancreatic acinar cells showed postmortem changes in mitochondria evolving over the first 60 minutes after death. Manganese loading experiments implicated mitochondrial manganese stores in the observed enhanced postmortem decrease in T1. This study calls into question reported relaxation time data for liver and pancreas. MR studies of excised tissues must account for time and temperature to prevent systematic experimental errors.  相似文献   
33.
Background: A lung-protecting strategy is essential when ventilating acute lung injury/acute respiratory distress syndrome patients. Current emphasis is on limiting inspiratory pressure and volume. This study was designed to investigate the effect of peak inspiratory flow on lung injury.

Methods: Twenty-four rabbits were anesthetized, tracheostomized, ventilated with a Siemens Servo 300, and randomly assigned to three groups as follows: 1) the pressure regulated volume control group received pressure-regulated volume control mode with inspiratory time set at 20% of total cycle time, 2) the volume control with 20% inspiratory time group received volume-control mode with inspiratory time of 20% of total cycle time, and 3) the volume control with 50% inspiratory time group received volume-control mode with inspiratory time of 50% of total cycle time. Tidal volume was 30 ml/kg, respiratory rate was 20 breaths/min, and positive end-expiratory pressure was 0 cm H2O. After 6 h mechanical ventilation, the lungs were removed for histologic examination.

Results: When mechanical ventilation started, peak inspiratory flow was 28.8 +/- 1.4 l/min in the pressure regulated volume control group, 7.5 +/- 0.5 l/min in the volume control with 20% inspiratory time group, and 2.6 +/- 0.3 l/min in the volume control with 50% inspiratory time group. Plateau pressure did not differ significantly among the groups. Gradually during 6 h, Pao2 in the pressure regulated volume control group decreased from 688 +/- 39 to a significantly lower 304 +/- 199 mm Hg (P < 0.05) (mean +/- SD). The static compliance of the respiratory system for the pressure regulated volume control group also ended significantly lower after 6 h (P < 0.05). Wet to dry ratio for the pressure regulated volume control group was larger than for other groups (P < 0.05). Macroscopically and histologically, the lungs of the pressure regulated volume control group showed more injury than the other groups.  相似文献   

34.
35.
36.
Our previous studies demonstrated that sodium glucose cotransporter 1 (SGLT-1) was induced in the remnant ileum of total colectomized rats via the action of factors other than hyperaldosteronism. The aim of the present study was to clarify whether fecal stream is required for the enhancement of SGLT-1-mediated sodium transport. Twenty-seven pairs of ileal tissues were obtained from the proximal and distal side, respectively, of loop ileostomy after total proctocolectomy. Mucosae were mounted in an Ussing chamber to evaluate glucose-coupled sodium transport. Levels of SGLT-1 mRNA in proximal and distal mucosae were compared by Northern blotting. Villous height and crypt depth were measured to test for correlations between mucosal structure and SGLT-1-mediated sodium transport or mRNA expression levels. Both glucose-coupled sodium transport and expression of SGLT-1 mRNA were significantly lower in distal mucosae relative to proximal mucosae. In distal mucosae, villous height, but not crypt depth, was significantly lower than in proximal mucosae, demonstrating a positive correlation between villous height and SGLT-1 function and expression. Comparative studies of proximal and distal mucosae demonstrated that in addition to hormonal changes, fecal stream is required for full induction of the sodium transport system (which includes SGLT-1-mediated transport) in the remnant ileum following total proctocolectomy. Presented in part at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois, May 14–19, 2005 (poster presentation). This work was supported by Grants-in-Aid for Scientific Research 10557118 and 14657295 from the Ministry of Education, Science and Culture of Japan to K. Fukushima, and by Kanae Foundation to K. Fukushima.  相似文献   
37.
The sera from 55 children with acute lymphoblastic leukemia (ALL) treated with active immunotherapy were examined for the presence of antibodies against common ALL antigen (CALLA). A solid phase indirect radioimmunometric assay (IRA) was developed which enabled the detection of anti-CALLA antibody in patients' sera, utilizing the ability of affinity-purified CALLA to bind Ricinus communis agglutinin and anti-CALLA antibody simultaneously. Using IRA, anti-CALLA antibody activity could not be detected in a majority of patients. We concluded that the patients did not raise comparable antibodies against CALLA, indicating this antigen is not immunogenic for ALL patients.  相似文献   
38.
We reported a 57-year-old female patient recently suffering from frequent seizures such as motionless staring and oral automatism. Electroencephalograms showed spikes in the right sphenoidal derivation and magnetic resonance images revealed an abnormal region, most likely related with a migration disorder such as a focal cortical dysplasia. She was diagnosed as mesiotemporal lobe epilepsy associated with a migration disorder. Seizure disappeared after medication therapy was done. No previous literature has described such a case, thus this is the first report of an epilepsy associated with migration disorder newly onset in a patient older than 50 years old.  相似文献   
39.
成人先天性胆管扩张症手术治疗   总被引:20,自引:0,他引:20  
目的 探讨成人先天性胆管扩张症手术治疗的经验体会。方法 回顾分析1985年1月至2004年12月中国医科大学附属第一医院普外科收治的成人先天胆管扩张症68例手术治疗资料。依Flanigan分型:Ⅰ型59例,Ⅱ型3例,Ⅳ型6例。所有病例均行囊肿切除,结果 术后发生胆汁漏6例。胰漏3例,急性胰腺炎2例。死亡2例,56例经1-20年随访,随访率为82.3%。5例表现轻度胆管炎,2例吻合口狭窄。余下49例均痊愈,无胆管炎及胆管狭窄表现。结论 囊肿切除、胆管空肠Roux-en-Y吻合是成人先天性胆管扩张症的首选治疗。切除囊肿时,囊肿近端在尽量切净囊肿基础上行大口吻合,防止术后吻合口狭窄;囊肿远端在保证睫液引流通畅、不损伤胰管开口的基础上,尽量切净囊肿内膜。  相似文献   
40.
JC virus (JCV) is a causative agent of progressive multifocal leukoencephalopathy and belongs to Polyomavirus. In this article we describe our recent research relating to this virus. First, JCV's major capsid protein VP1 possesses a nuclear localization signal (NLS) and has the ability to construct a virus-like particle (VLP). We have investigated the mechanism of nuclear entry of JCV using VLP, and clarified the role of NLS. In vitro transport assay revealed that wild type VLP (wtVLP), but not deltaNLSVLP, entered the nuclei of cells. The nuclear transport of wtVLP was dependent on the addition of importins alpha and beta and was prevented by antibodies to nuclear pore complex (NPC). These results suggested that JCV VLP binds to cellular importins via the NLS of VP1 and is transported into the nucleus through the NPC. Second, a yeast two-hybrid screen of a human brain cDNA library demonstrated that the fasciculation and elongation protein zeta 1 (FEZ1) and the heterochromatin protein lalpha (HPla) are proteins that interacted with JCV agnoprotein (Agno). In vitro binding assay showed that Agno interacts directly with FEZ1 and HPlalpha. We have also shown that Agno induces the dissociation of FEZ1 from microtubules and dissociates the interaction between HPlalpha and lamin B receptor. We have demonstrated that interaction between Agno and these host proteins inhibited nuclear egress of JCV. Third, in order to inhibit JCV infection in infected cells, we synthesized siRNA which is specific for JCV Agno. Immunoblotting and immunocytochemical analysis demonstrated that expression levels of agnoprotein and VP1 were significantly inhibited by specific siRNA. In addition, levels of viral mRNAs and viral production were decreased in the cells transfected with Agno siRNA. Furthermore, viral production of cell treated with Agno siRNA was significantly inhibited. These results indicate that post-infection treatment with siRNAs, that targets JCV Agno suppresses virus production in JCV infected cells. Thus, siRNA directed against JCV encoding genes may provide a useful tool for suppression of JCV infection.  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