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   10268篇
  免费   579篇
  国内免费   162篇
耳鼻咽喉   163篇
儿科学   114篇
妇产科学   121篇
基础医学   1581篇
口腔科学   232篇
临床医学   758篇
内科学   2042篇
皮肤病学   399篇
神经病学   626篇
特种医学   598篇
外科学   1518篇
综合类   115篇
一般理论   3篇
预防医学   392篇
眼科学   207篇
药学   910篇
中国医学   144篇
肿瘤学   1086篇
  2024年   10篇
  2023年   80篇
  2022年   236篇
  2021年   418篇
  2020年   150篇
  2019年   267篇
  2018年   309篇
  2017年   239篇
  2016年   385篇
  2015年   464篇
  2014年   543篇
  2013年   566篇
  2012年   896篇
  2011年   800篇
  2010年   500篇
  2009年   408篇
  2008年   587篇
  2007年   578篇
  2006年   502篇
  2005年   476篇
  2004年   396篇
  2003年   337篇
  2002年   255篇
  2001年   269篇
  2000年   233篇
  1999年   164篇
  1998年   94篇
  1997年   78篇
  1996年   68篇
  1995年   69篇
  1994年   48篇
  1993年   49篇
  1992年   76篇
  1991年   58篇
  1990年   41篇
  1989年   49篇
  1988年   41篇
  1987年   43篇
  1986年   34篇
  1985年   37篇
  1984年   12篇
  1983年   15篇
  1982年   10篇
  1981年   16篇
  1980年   12篇
  1979年   9篇
  1978年   8篇
  1977年   10篇
  1976年   12篇
  1975年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Effects of plantago-mucilage A (P-MA) on the immune responses were studied in ICR mice. Mice were divided into 4 groups (10 mice/group), and P-MA at doses of 7, 21 and 63 mg/kg were orally administered to mice once a day for 21 consecutive days. Mice were immunized and challenged with sheep red blood cells (SRBC). P-MA at 63 mg/kg/day significantly increased the body weight gain and the relative weights of spleen and thymus, as compared with those in controls. However, there were no significant effects on liver weight due to P-MA treatment. Plaque forming cells (PFC) and hemagglutination (HA) titers to SRBC were significantly enhanced in mice dosed at 21 and 63 mg/kg/day P-MA, as compared with those in controls. Delayed-type hypersensitivity (DTH) reaction to SRBC, phagocyte activity and circulating leukocyte were also significantly increased in mice dosed at 63 mg/kg/day P-MA. These results demonstrate that P-MA markedly enhances both humoral immune and allergic reaction to SRBC at concentrations which don’t act on the relative weight of liver.  相似文献   
32.
We report a case of rare multiple internal resorptions. Etiology of multiple internal resorptions is unknown. Interestingly, the patient had an atopic dermatitis, which is possibly related to multiple and rapid internal resorptions.  相似文献   
33.
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   
34.
The UV-pattern of several flavones, their cytotoxicities against L1210 cell and their Inhibiting effects on ATPase from the cell seem to be correlated. 5,2′-Dihydroxy-6,7,8,6′-tetramethoxyflavone (ED50=2.3 ug/ml) and 5,2′,6′-trihydroxy-6,7,8-trimethoxyflavone (ED50=4.5 ug/ml), the most active flavones studied, have shown a narrow range of the absorbance ratio, Log εII/Log εI=1.073~1.109. They have inhibited the ATPase-activity to the greatest extent. These findings suggest that a certain angle between the flavone rings B and C plays an important role for the inhibition of the enzyme activity and thus the cytotoxicity.  相似文献   
35.
Summary: Purpose: A prospective series of 643 persons with epilepsy attending a reference neurologic center in Medellin, Colombia, was examined by computed tomography (CT scan) or serology or both with the enzyme-linked immunoelectrotransfer blot assay (EITB) to assess the prevalence of Taenia solium cysticercosis. Methods: All presenting patients were consecutively enrolled in the study. Five hundred forty-six persons underwent cerebral CT scans; 376 of them also had serum EITB performed. Results: Prevalence of neurocys@ercosis by CT scan was 13.92%. Overall prevalence of T. solium antibodies with EITB was 9.82%, but for those with late-onset epilepsy (onset after age 30 years), prevalence increased to 17.5% and 19% for those who originated from outside urban Medellin. Seroprevalence in individuals with mixed lesions (cysts and calcifications) was 88.2% and 64.10% in those with live cysts. Conversely, only 2.72% of persons with CT findings not related to neurocysticercosis had positive EITB tests. Conclusions: Our study shows that an important proportion of individuals with epilepsy have radiologic or serologic evidence of T. solium infection, suggesting that neurocysticercosis is an important etiology for epilepsy in Colombia.  相似文献   
36.
37.
38.
Peripheral primitive neuroectodermal tumour (PNET)/Ewing's sarcoma (ES) and neuroblastoma (NB) are related tumours of neural crest origin with primitive neural characteristics. Fibroblast growth factor 2 (FGF2) is a critical signalling molecule for primitive neural crest cells. The treatment of NB cells with FGF2 variably affects biological characteristics such as growth and differentiation, while in PNET/ES, FGF2 predominantly induces apoptosis. The JK-GMS Askin tumour cell line can be induced to differentiate upon treatment with nerve growth factor (NGF), indicating the integrity of the cellular machinery necessary for differentiation. The present study assesses whether FGF2 can induce differentiation in JK-GMS cells. JK-GMS cells expressed high-affinity FGF receptors (FGFRs), and treatment with FGF2 induced phosphorylation of FGFR1 together with activation of extracellular signal-regulated kinases (ERK1/ERK2) and c-Jun N-terminal kinase (JNK). Subsequent biological effects were growth inhibition, neuronal differentiation, and apoptosis, and these changes were associated with increased expression of neurofilaments, reduction of c-myc and bcl-2 expression, and activation of caspase 3. Treatment of the cells with a specific inhibitor of the MAPK/extracellular signal-regulated kinase (MEK)-1, PD98059, predominantly inhibited the effects of FGF2 on growth, differentiation, and apoptosis, while an inhibitor of JNK reduced apoptosis, indicating that the ERK1/2 and JNK pathways are critical components of FGF2-mediated effects in JK-GMS cells. Additional comparative analyses of FGF2-mediated effects in two ES cell lines (CADO-ES, RD-ES) and a PNET cell line (SK-N-MC) showed pronounced differentiation in SK-N-MC, but not in CADO-ES or RD-ES cells. This study demonstrates that FGF2 can induce neuronal differentiation of PNET including Askin tumour. These findings clearly indicate that the FGF2-mediated signalling pathway plays a critical role in controlling the major properties of PNET cells and may provide a potential therapeutic target for PNET.  相似文献   
39.
Mutations in the Bruton's tyrosine kinase (BTK) gene are responsible for X-linked agammaglobulinemia (XLA). We identified BTK mutations in six patients with presumed XLA from unrelated Korean families. Four out of six mutations were novel: two missense mutations (P565T, C154Y), a point mutation in a splicing donor site (IVS11+1G>A), and a large deletion (a 6.1-kb deletion including BTK exons 11–18). The large deletion, identified by long-distance PCR, revealed Alu-Alu mediated recombination extended from an Alu sequence in intron 10 to another Alu sequence in intron 18, spanning a distance of 6.1 kb. The two known mutations consisted of one missense (G462D) mutation, and a point mutation in a splicing acceptor site (IVS7−9A>G). This study suggests that large genomic rearrangements involving Alu repeats are few but an important component of the spectrum of BTK mutations.  相似文献   
40.
Oxidative damage to mitochondrial DNA (mtDNA) increases with age in the brain and can induce G:C to T:A and T:A to G:C point mutations. Though rare at any particular site, multiple somatic mtDNA mutations induced by oxidative damage or by other mechanisms may accumulate with age in the brain and thus could play a role in aging and neurodegenerative diseases. However, no prior study has quantified the total burden of mtDNA point mutation subtypes in the brain. Using a highly sensitive cloning and sequencing strategy, we find that the aggregate levels of G:C to T:A and T:A to G:C transversions and of all point mutations increase with age in the frontal cortex (FCtx). In the substantia nigra (SN), the aggregate levels of point mutations in young controls are similar to the levels in the SN or FCtx of elderly subjects. Extrapolation from our data suggests an average of 2.7 (FCtx) to 3.2 (SN) somatic point mutations per mitochondrial genome in elderly subjects. There were no significant differences between Parkinson's disease (PD) patients and age-matched controls in somatic mutation levels. These results indicate that individually rare mtDNA point mutations reach a high aggregate burden in FCtx and SN of elderly subjects.  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