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   24420篇
  免费   1237篇
  国内免费   146篇
耳鼻咽喉   174篇
儿科学   658篇
妇产科学   571篇
基础医学   2868篇
口腔科学   792篇
临床医学   2245篇
内科学   6469篇
皮肤病学   357篇
神经病学   2136篇
特种医学   663篇
外国民族医学   1篇
外科学   3320篇
综合类   94篇
一般理论   7篇
预防医学   1315篇
眼科学   293篇
药学   1564篇
中国医学   54篇
肿瘤学   2222篇
  2023年   142篇
  2022年   240篇
  2021年   483篇
  2020年   316篇
  2019年   445篇
  2018年   566篇
  2017年   418篇
  2016年   463篇
  2015年   558篇
  2014年   782篇
  2013年   986篇
  2012年   1535篇
  2011年   1625篇
  2010年   902篇
  2009年   895篇
  2008年   1502篇
  2007年   1616篇
  2006年   1530篇
  2005年   1536篇
  2004年   1382篇
  2003年   1195篇
  2002年   1202篇
  2001年   480篇
  2000年   459篇
  1999年   472篇
  1998年   255篇
  1997年   208篇
  1996年   207篇
  1995年   195篇
  1994年   160篇
  1993年   153篇
  1992年   291篇
  1991年   273篇
  1990年   248篇
  1989年   214篇
  1988年   195篇
  1987年   185篇
  1986年   182篇
  1985年   168篇
  1984年   147篇
  1983年   100篇
  1982年   87篇
  1981年   83篇
  1980年   63篇
  1979年   96篇
  1978年   62篇
  1977年   49篇
  1976年   53篇
  1975年   52篇
  1974年   44篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
41.
Menthol glucuronide was isolated from the urine of a healthy 70-kg female subject following ingestion of 400 mg of peppermint oil and 6 g of 99% [U-(13)C]glucose. Glucuronide (13)C-excess enrichment levels were 4-6% and thus provided high signal-to-noise ratios (SNRs) for confident assignment of (13)C-(13)C spin-coupled multiplet components within each (13)C resonance by (13)C NMR. The [U-(13)C]glucuronide isotopomer derived via direct pathway conversion of [U-(13)C]glucose to [U-(13)C]UDP-glucose was resolved from [1,2,3-(13)C(3)]- and [1,2-(13)C(2)]glucuronide isotopomers derived via Cori cycle or indirect pathway metabolism of [U-(13)C]glucose. In a second study, a group of four overnight-fasted patients (63 +/- 10 kg) with severe heart failure were given peppermint oil and infused with [U-(13)C]glucose for 4 hr (14 mg/kg prime, 0.12 mg/kg/min constant infusion) resulting in a steady-state plasma [U-(13)C]glucose enrichment of 4.6% +/- 0.6%. Menthol glucuronide was harvested and glucuronide (13)C-isotopomers were analyzed by (13)C NMR. [U-(13)C]glucuronide enrichment was 0.6% +/- 0.1%, and the sum of [1,2,3-(13)C(3)] and [1,2-(13)C(2)]glucuronide enrichments was 0.9% +/- 0.2%. From these data, flux of plasma glucose to hepatic UDPG was estimated to be 15% +/- 4% that of endogenous glucose production (EGP), and the Cori cycle accounted for at least 32% +/- 10% of GP.  相似文献   
42.
43.
Results of a recent study have demonstrated that exposure to multiple ethanol concentrations and repeated ethanol deprivation periods in Indiana ethanol-preferring (P) rats resulted in the development of an alcohol deprivation effect (ADE; the temporary increase in voluntary ethanol intake after a period of deprivation from ethanol) characterized by consumption of intoxicating amounts of ethanol. The current study was designed to possibly extend these results to Sardinian alcohol-preferring (sP) rats, generated with the same selective program previously used for P rats. To this aim, ethanol-naive sP rats were exposed initially to the home cage four-bottle choice [10%, 20%, and 30% (vol./vol.) ethanol solutions and water] for eight consecutive weeks. Subsequently, rats were divided into two groups: The first group had continuous access to the four-bottle regimen (nondeprived rats), and the second group was exposed to five cycles of 14-day periods of deprivation from ethanol and 14-day periods of reexposure to the four-bottle regimen. An ADE developed after each deprivation period. However, the extra intake of ethanol was limited to the first hour of each reaccess period. Magnitude of ADE did not change with repeated periods of deprivation. However, a shift in preference toward the two highest concentrations of ethanol solutions was evident from the first reexposure to ethanol and was maintained throughout the study. These results provide further evidence on the heterogeneity of ethanol-drinking behavior among rat lines selectively bred for high ethanol preference and consumption.  相似文献   
44.
OBJECTIVE: The present study tested the hypothesis that cortical electroencephalographic (EEG) rhythms. change across normal elderly (Nold), mild cognitive impairment (MCI), and Alzheimer's disease (AD) subjects as a function of the global cognitive level. METHODS: Resting eyes-closed EEG data were recorded in 155 MCI, 193 mild AD, and 126 age-matched Nold subjects. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha 1 (8-10.5 Hz), alpha 2 (10.5-13 Hz), beta 1 (13-20 Hz), and beta 2 (20-30 Hz). EEG cortical sources were estimated by LORETA. RESULTS: Occipital delta and alpha 1 sources in parietal, occipital, temporal, and 'limbic' areas had an intermediate magnitude in MCI subjects compared to mild AD and Nold subjects. These five EEG sources presented both linear and nonlinear (linear, exponential, logarithmic, and power) correlations with the global cognitive level (as revealed by mini mental state examination score) across all subjects. CONCLUSIONS: Cortical EEG rhythms change in pathological aging as a function of the global cognitive level. SIGNIFICANCE: The present functional data on large populations support the 'transitional hypothesis' of a shadow zone across normality, pre-clinical stage of dementia (MCI), and AD.  相似文献   
45.
46.
Almost 90% of primary acute pericarditis are idiopathic. Between specifics forms, a very low percentage of cases are due to chronic rheumatic diseases. A case of adult Still's disease (juvenile chronic rheumatoid arthritis) with acute pericarditis being the first clinical manifestation (besides fever and general syndrome) is presented. Therapy with oral prednisone was rapidly effective, and pericardial effusion resolved after 3 weeks of treatment, as echocardiography showed.  相似文献   
47.
Dysfunction of neutrophils in patients infected with human immunodeficiency virus is at least partly responsible for secondary microbial diseases in these individuals, including invasive gastrointestinal (GI) candidiasis. Immunoregulatory disturbances associated with the development of AIDS in human immunodeficiency virus-infected patients exacerbates Candida albicans infection of the upper GI tract and frequently leads to oropharyngeal and esophageal candidiasis. In this article, we present the first report of a murine model of invasive GI candidiasis associated with an AIDS-related murine immunodeficiency syndrome that results from infection of C57BL/6 mice with a previously described retrovirus complex (LP-BM5). Mice of the inbred strain were infected with C. albicans by oral-intragastric inoculation as infants and with the retrovirus by the intraperitoneal route 30 days later. Control mice of the same strain were infected with C. albicans as above and subsequently infected with the avirulent, ecotropic helper virus (MBI-5). Animals were killed 90 days after retroviral challenge. Total and differential blood cell counts, CD4+ T-cell counts in the spleen, and the histopathology of the gastric mucosa of experimental and control animals were determined. The virulent LP-BM5-infected animals developed murine AIDS and showed eruptive and suppurative lesions, with associated C. albicans mainly in regions of the cardial-atrium fold of the stomach. Well-defined abscesses with entrapped C. albicans hyphae were observed in the region of the cardial-atrium fold of control mice. A significant increase in the number of C. albicans CFU in homogenized and plated segments of the GI tract was recognized in mice with murine AIDS versus the control animals. The murine model of GI candidiasis reported here permits examination of the nature of C. albicans interaction with the gastric mucosa both in the immunocompetent host under conditions in which the yeast exists predominantly as a commensal organism and in the immunosuppressed host during progressive stages of AIDS induced by a retroviral infection.  相似文献   
48.
The neuroendocrine and clinical effects of transdermal 17β-estradiol (rated at 50 μg/day; TTS 50) were studied in 40 postmenopausal women; ten additional postmenopausal women did not receive any drugs. The changes in LH and rectal temperature induced by the infusion of the opioid antagonist naloxone (10 mg i.v. bolus plus 10 mg/h for 4 h) were used to evaluate the central activity of endogenous opioid peptides. TTS 50 increased opioid activity, as evidenced by the restoration of the LH response (P < 0.01) and the enhancement of the hypothermic effect (P < 0.05) of naloxone. A greater reduction in hot flushes was observed in TTS 50-treated subjects than in untreated women, with the maximal effect of TTS 50 achieved after 3 months of therapy. TTS 50 did not modify the concentrations of circulating lipids, glucose or liver enzymes but reduced the biochemical parameters indicative of bone reabsorption. Bone density of the distal radius significantly increased during TTS 50 (P < 0.02), reaching its maximum value after 6 months of therapy. Thereafter bone density declined, but more slowly than in untreated women.

Our data suggest that TTS 50 has marked neuroendocrine effects, that it diminishes the incidence of hot flushes and reduces bone demineralization. By contrast, it has a very little, if any, metabolic impact on the liver or on glucose and lipid metabolism.  相似文献   

49.
STUDY OBJECTIVE: To compare the efficacy of propofol, methohexital, and midazalom in providing adequate sedation during administration of retrobulbar block and satisfactory postoperative amnesia. DESIGN: Retrospective chart review over a 4-month period. SETTING: Ambulatory patients in the main operating room of a university-affiliated hospital. PATIENTS: One hundred forty-seven ambulatory patients undergoing ophthalmologic surgery of less than 2 hours' duration under regional anesthesia consisting of retrobulbar or peribulbar block and intravenous (IV) sedation. INTERVENTIONS: One of three drugs--propofol 0.47 +/- 0.06 mg/kg, midazolam 0.02 +/- 0.005 mg/kg, or methohexital 0.45 +/- 0.16 mg/kg--was administered IV. Patients were observed for a minimum of 60 seconds or until adequate sedation was achieved, after which a retrobulbar or peribulbar block was performed. MEASUREMENTS AND MAIN RESULTS: Blood pressure, electrocardiogram, and oxygen saturation were monitored and recorded. Patients were observed for apnea, hiccups, pain on injection, excitement, tremor, grimacing, or verbal response during the block. The requirement for additional sedation intraoperatively was noted. Patients were questioned postoperatively in the ambulatory recovery room for recall of needle insertion or discomfort during the block, as well as about their satisfaction with the overall experience. CONCLUSIONS: Grimacing or verbal response during the retrobulbar or peribulbar block did not predict or correlate with patient recall. Propofol was equal to both midazolam and methohexital in providing adequate sedation and postoperative amnesia but possesses the added advantages of reduced postoperative vomiting, lower intraocular pressure, and earlier return-to-home readiness.  相似文献   
50.
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