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   4494篇
  免费   308篇
  国内免费   48篇
耳鼻咽喉   99篇
儿科学   85篇
妇产科学   47篇
基础医学   677篇
口腔科学   92篇
临床医学   339篇
内科学   896篇
皮肤病学   166篇
神经病学   329篇
特种医学   389篇
外科学   696篇
综合类   26篇
预防医学   198篇
眼科学   51篇
药学   393篇
中国医学   50篇
肿瘤学   317篇
  2023年   22篇
  2022年   67篇
  2021年   133篇
  2020年   73篇
  2019年   89篇
  2018年   146篇
  2017年   89篇
  2016年   160篇
  2015年   182篇
  2014年   287篇
  2013年   281篇
  2012年   374篇
  2011年   364篇
  2010年   198篇
  2009年   202篇
  2008年   241篇
  2007年   233篇
  2006年   243篇
  2005年   245篇
  2004年   200篇
  2003年   169篇
  2002年   169篇
  2001年   85篇
  2000年   75篇
  1999年   78篇
  1998年   20篇
  1997年   20篇
  1996年   36篇
  1995年   21篇
  1994年   14篇
  1993年   17篇
  1992年   34篇
  1991年   37篇
  1990年   26篇
  1989年   22篇
  1988年   29篇
  1987年   19篇
  1986年   25篇
  1985年   15篇
  1984年   13篇
  1983年   14篇
  1982年   11篇
  1979年   14篇
  1978年   5篇
  1977年   8篇
  1976年   6篇
  1975年   7篇
  1974年   8篇
  1972年   4篇
  1969年   3篇
排序方式: 共有4850条查询结果,搜索用时 62 毫秒
11.
Angiostrongylus (Parastrongylus) eosinophilic meningitis   总被引:1,自引:0,他引:1  
Angiostrongylus (Parastrongylus) cantonensis is the commonest cause of eosinophilic meningitis in the world. Infective third-stage larvae develop in slugs and snails. Humans are infected primarily in the central nervous system after ingesting an infected intermediate host. Damage by motile worms, inflammatory responses to foreign bodies, and possible toxicity of worm substances work in concert to produce the pathologic and clinical picture of neurologic angiostrongyliasis. This disease manifests itself by headache, paresthesias, generalized weakness, and occasionally visual disturbances and extraocular muscular paralysis. Eosinophilic pleocytosis is the major laboratory finding. Although the diagnosis of neurologic angiostrongyliasis is usually made clinically, serologic methods such as ELISA (enzyme-linked immunosorbent assay) can be helpful. Occasionally, living larvae can be identified histologically in the CSF, eye, or other tissue. There is no specific treatment for this disease. Corticosteroids may be useful to relieve increased intracranial pressure. The role of anthelmintic drugs, such as thiabendazole and ivermectin, is not yet known. The prognosis of neurologic angiostrongyliasis is usually good; however, fatal and chronic cases do occur. Appropriate preparation of food, control of mollusks and planarians, and elimination of rodents are important measures in limiting the further spread of eosinophilic meningitis caused by A. cantonensis.  相似文献   
12.
Nutrition resources in Chinese have been developed for the patients in St. Paul's Hospital's Renal Program. The goal was to support this patient subgroup to understand and practice the complicated diet guidelines within their own language and cultural contexts.  相似文献   
13.
BACKGROUND: Overall neocortical gray matter (NCGM) volume has not been studied in first-episode schizophrenia (FESZ) at first hospitalization or longitudinally to evaluate progression, nor has it been compared with first-episode affective psychosis (FEAFF). METHODS: Expectation-maximization/atlas-based magnetic resonance imaging (MRI) tissue segmentation into gray matter, white matter (WM), or cerebrospinal fluid (CSF) at first hospitalization of 29 FESZ and 34 FEAFF, plus 36 matched healthy control subjects (HC), and, longitudinally approximately 1.5 years later, of 17 FESZ, 21 FEAFF, and 26 HC was done. Manual editing separated NCGM and its lobar parcellation, cerebral WM (CWM), lateral ventricles (LV), and sulcal CSF (SCSF). RESULTS: At first hospitalization, FESZ and FEAFF showed smaller NCGM volumes and larger SCSF and LV than HC. Longitudinally, FESZ showed NCGM volume reduction (-1.7%), localized to frontal (-2.4%) and temporal (-2.6%) regions, and enlargement of SCSF (7.2%) and LV (10.4%). Poorer outcome was associated with these LV and NCGM changes. FEAFF showed longitudinal NCGM volume increases (3.6%) associated with lithium or valproate administration but without clinical correlations and regional localization. CONCLUSIONS: Longitudinal NCGM volume reduction and CSF component enlargement in FESZ are compatible with post-onset progression. Longitudinal NCGM volume increase in FEAFF may reflect neurotrophic effects of mood stabilizers.  相似文献   
14.
This describes a retrospective study in which 88 lung cancer patients and 137 district-matched controls were interviewed concerning the effects of diet on lung cancer risk among Hong Kong Chinese women who never smoked tobacco. Those in the lowest tertile of consuming fresh fruit or fresh fish had statistically significant adjusted relative risks (RRs) of 2.4 and 2.8, respectively. The protective effects of diet, i.e., higher consumption of leafy green vegetables, carrots, tofu, fresh fruit, and fresh fish, were confined mostly to those with adenocarcinoma or large cell tumors. Only fresh fruit was found to positively, and smoked meats to negatively, affect the risk of squamous or small cell tumors. Foods high in vitamin C, retinol, and calcium seemed to exert larger effects. Subjects from larger households were shown to be more frequent consumers of fresh vegetables, fruit, and fish. Because the lifetime weighted household size could be used as a surrogate index of past dietary quality, when it was combined with current dietary intakes of fresh fruit, the RR increased as either factor decreased in a dose-response manner. The adjusted RR was 5.8 at the lowest level. Further testing of the validity of the lifetime weighted household size as an index of past dietary quality is needed.  相似文献   
15.
OBJECTIVES: An investigation was conducted to determine whether ongoing transmission of Mycobacterium tuberculosis was occurring in a California state prison. METHOD: Prison pharmacy records were used to identify cases of active tuberculosis (TB). RESULTS: Ten of the 18 cases of active TB treated at the facility during 1991 were diagnosed at the prison that same year (an incidence of 184 per 100,000). Three inmates were infectious for a total of 7 months while imprisoned. The prevalence of TB skin test-positivity among inmates was 30%, and the incidence of new infection attributable to incarceration was 5.9 per 100 inmates per year. CONCLUSIONS: Transmission of M. tuberculosis may be occurring in the California prison system.  相似文献   
16.
Extensive studies have shown that the current assays used to identify cattle infected with Mycobacterium bovis or Mycobacterium avium subsp. paratuberculosis are not sufficiently sensitive and specific to detect all infected animals, especially animals recently infected with the pathogens. In the present report we show that these limitations might be overcome with a latex bead agglutination assay (LBAA). With the specific immunodominant epitope (ESAT6-p) of M. bovis, we developed an LBAA and enzyme immunoassay (EIA) for that purpose and compared them with the “gold standard” culture method and skin test for their efficacy in detecting bovine tuberculosis. When sera from control healthy cows (n = 10), M. avium subsp. paratuberculosis-positive cattle (naturally infected, n = 16; experimentally infected, n = 8), and M. bovis-positive cattle (naturally infected, n = 49;experimentally infected, n = 20) were applied to an EIA and an LBAA developed with ESAT6-p, the two tests showed similar sensitivity (97.1% by EIA, 95.7% by LBAA), high specificity (94.2% by EIA, 100% by LBAA), and a positive correlation (kappa value, 0.85; correlation rate, 93.2%; correlation coefficient, 0.64). Receiver operating characteristic analysis of EIA results and comparison with the culture method determined a suitable cutoff value at 0.469, with an area under the curve of 0.991 (95% confidence interval, 0.977 to 1.0). As LBAA didn't show any positive reactions with sera from uninfected control cows or M. avium subsp. paratuberculosis-infected cattle, which were confirmed to be free of M. bovis by culture or PCR, LBAA using the ESAT6-p can be a rapid and useful M. bovis diagnostic assay. The data suggest that rapid, sensitive, and specific assays can be developed with peptides containing immunodominant epitopes present in proteins uniquely expressed in M. bovis or M. avium subsp. paratuberculosis for differential diagnosis of cattle infected with M. bovis or M. avium subsp. paratuberculosis.  相似文献   
17.
Johne's disease of cattle is widespread and causes significant economic loss to producers. Control has been hindered by limited understanding of the immune response to the causative agent, Mycobacterium avium subsp. paratuberculosis, and lack of an effective vaccine and sensitive specific diagnostic assays. The present study was conducted to gain insight into factors affecting the immune response to M. avium subsp. paratuberculosis. A persistent proliferative response to M. avium subsp. paratuberculosis purified protein derivative and soluble M. avium subsp. paratuberculosis antigens was detected in orally infected neonatal calves 6 months postinfection (p.i.) by flow cytometry (FC). CD4(+) T cells with a memory phenotype (CD45R0(+)) expressing CD25 and CD26 were the predominant cell type responding to antigens. Few CD8(+) T cells proliferated in response to antigens until 18 months p.i. gammadelta T cells did not appear to respond to antigen until 18 months p.i. The majority of WC1(+) CD2(-) and a few WC1(-) CD2(+) gammadelta T cells expressed CD25 at time zero. By 18 months, however, subsets of gammadelta T cells from both control and infected animals showed an increase in expression of CD25, ACT2, and CD26 in the presence of the antigens. Two populations of CD3(-) non-T non-B null cells, CD2(+) and CD2(-), proliferated in cell cultures from some control and infected animals during the study, with and without antigen. The studies clearly show multicolor FC offers a consistent reliable way to monitor the evolution and changes in the immune response to M. avium subsp. paratuberculosis that occur during disease progression.  相似文献   
18.
Since intimal smooth muscle cells (SMC) are an important feature of atherosclerotic fibrofatty plaques, we tested the hypothesis that endothelial cells (EC) regulate SMC proliferation in the process of neointimal formation. Using a porcine thoracic aortic organ culture (OC) system, we previously showed in a preliminary study that short-term porcine aortic explants incubated in 5% fetal bovine serum for 7 days promote neointimal formation only in the presence of endothelium or in conditioned media collected from proliferating OC with endothelium present. We now report that these organ cultures can be maintained in culture for up to 4 weeks. The surface cells stained positively for dil-acetylated-low-density lipoprotein throughout the 4-week period indicating the continued presence of EC while the neointimal cells stained positively for the smooth muscle actin-specific monoclonal antibodies alpha-SM1 and HHF-35 indicating their smooth muscle nature. The number of EC did not change during the 4-week incubation period, however, EC turnover peaked at 5 days and remained elevated but constant throughout. The number of intimal SMC doubled between day 0 (18.4 +/- 0.2 cells/field) and day 7 (41.5 +/- 0.9) and between day 7 and day 14 (75.8 +/- 10.1). The intimal SMC number then stabilized thereafter (day 21: 79.5 +/- 7.8, day 28: 73.8 +/- 12.1). Cell proliferation played a large part since autoradiography studies using nondenuded OC showed that intimal SMC thymidine index on day 0 was 1.4% +/- 0.4, peaked at the end of day 5 (25.7% +/- 4.1) and gradually decreased thereafter. The peak in the intimal SMC thymidine index occurred during a period of high EC turnover (maximum EC thymidine index on day 5: 21.8% +/- 2.1), and the stabilization of intimal SMC number observed beyond 2 weeks of incubation occurred when EC replication was reduced (day 14: 6.7% +/- 0.21). Incubation of organ cultures denuded of their endothelium in 5% fetal bovine serum showed a marked decrease in neointimal formation. However, denuded OC when incubated in conditioned medium collected from 4-day-old nondenuded OC (4DCM) enhanced neointimal formation of denuded OC. In contrast, the neointima of denuded OC incubated in 24-day-old nondenuded OC conditioned medium was similar to that of controls. The thymidine index of intimal SMC of denuded OC treated with 4DCM was markedly higher than that found with the control treatment at all time points.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
19.
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   
20.
Burkholderia pseudomallei is the causative agent of melioidosis, an infectious disease with protean clinical manifestations. The major route of infection is thought to be through subcutaneous inoculation of contaminated soil and water, although ingestion and inhalation of contaminated aerosols are also possible. This study examines infection through the intranasal route in a murine model to mimic infection through inhalation. Two strains of mice, C57BL/6 and BALB/c, exhibit differential susceptibilities to the infection, with the C57BL/6 mice being considerably more resistant. To examine host factors that could contribute to this difference, bacterial loads and cytokine profiles in the two strains of mice were compared. We found that infected BALB/c mice exhibited higher bacterial loads in the lung and spleen and that they produced significantly higher levels of gamma interferon (IFN-gamma) in the serum than C57BL/6 mice. Although tumor necrosis factor alpha and interleukin-1 could be detected in the nasal washes and sera of both strains of mice, the production in serum was transient and much lower than that of IFN-gamma. C57BL/6 mice also exhibited memory responses to bacteria upon reinfection, with the production of serum immunoglobulin G (IgG) and mucosal IgA antibodies. Thus, it is possible that the production of systemic and mucosal antibodies is important for protection against disease in C57BL/6 mice.  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