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   13916篇
  免费   1445篇
  国内免费   440篇
耳鼻咽喉   167篇
儿科学   135篇
妇产科学   609篇
基础医学   2603篇
口腔科学   372篇
临床医学   903篇
内科学   1266篇
皮肤病学   449篇
神经病学   225篇
特种医学   209篇
外国民族医学   1篇
外科学   923篇
综合类   2257篇
现状与发展   2篇
一般理论   1篇
预防医学   1643篇
眼科学   56篇
药学   881篇
  7篇
中国医学   307篇
肿瘤学   2785篇
  2024年   30篇
  2023年   198篇
  2022年   396篇
  2021年   495篇
  2020年   520篇
  2019年   563篇
  2018年   532篇
  2017年   521篇
  2016年   531篇
  2015年   546篇
  2014年   869篇
  2013年   848篇
  2012年   756篇
  2011年   1023篇
  2010年   786篇
  2009年   786篇
  2008年   719篇
  2007年   756篇
  2006年   716篇
  2005年   541篇
  2004年   501篇
  2003年   473篇
  2002年   407篇
  2001年   407篇
  2000年   387篇
  1999年   302篇
  1998年   189篇
  1997年   163篇
  1996年   111篇
  1995年   94篇
  1994年   80篇
  1993年   49篇
  1992年   63篇
  1991年   31篇
  1990年   39篇
  1989年   38篇
  1988年   26篇
  1987年   22篇
  1986年   14篇
  1985年   33篇
  1984年   41篇
  1983年   19篇
  1982年   35篇
  1981年   29篇
  1980年   22篇
  1979年   17篇
  1978年   16篇
  1976年   12篇
  1975年   13篇
  1974年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
大学生儿童期心理虐待经历与个性特征的关系   总被引:2,自引:4,他引:2  
目的:了解大学生儿童期心理虐待和忽视状况及其与个性特征的关系。方法:应用儿童心理虐待与忽视量表和卡特尔16PF对216名大学生进行问卷调查。结果:①受试学生中心理虐待阳性者45人(20.83﹪);忽视阳性者88人(40.74﹪);不同性别的虐待和忽视阳性率均无统计学差异(P>0.05);②男生心理虐待总分均分、责骂均分、恐吓均分三项高于女生相应得分,差别具统计学意义(P<0.05);③虐待阳性组在乐群性、稳定性、兴奋性、有恒性、敢为性、自律性、内向与外向、感情用事与安详机警等多项个性因素上得分低于阴性组,在怀疑性、忧虑性、适应与焦虑三项上得分高于后者(P<0.05);④受试学生儿童期心理虐待和忽视与乐群性、稳定性、恃强性、兴奋性、有恒性、敢为性、自律性、内向与外向、感情用事与安详机警等人格因素呈负相关,与怀疑性、忧虑性、紧张性、适应与焦虑等个性因素呈正相关(P<0.05)。结论:①受试大学生儿童期心理虐待和忽视经历多见,男生儿童期心理虐待发生程度较女生重;②儿童期心理虐待和忽视与大学生外向乐观、开朗合群、情绪稳定等积极个性特征呈负相关,而与其多疑刚愎、抑郁自扰、对环境的适应能力不足等消极个性特征呈正相关。  相似文献   
72.
We previously reported that low levels of tyrosine (Tyr) and phenylalanine (Phe) alter the metastatic phenotype of B16-BL6 (BL6) murine melanoma and select for tumor cell populations with decreased lung colonizing ability. To more specifically characterize the effects of Tyr and Phe restriction on the malignant phenotype of BL6, we investigated in vitro attachment, invasion, proteinase expression, and chemotaxis of high and low metastatic BL6 variants. High metastatic variant cells were isolated from subcutaneous tumors of mice fed a nutritionally complete diet (ND cells) and low metastatic variant cells were isolated from mice fed a diet restricted in Tyr and Phe (LTP cells). Results indicate that attachment to reconstituted basement membrane (Matrigel) was significantly reduced in LTP cells as compared to ND cells. Attachment to collagen IV, laminin, and fibronectin were similar between the two variants. Invasion through Matrigel and growth factor-reduced Matrigel were significantly decreased in LTP cells as compared to ND cells. Zymography revealed the presence of M r 92 000 and M r 72 000 progelatinases, tissue plasminogen activator, and urokinase plasminogen activator in the conditioned medium of both variants; however, there were no differences in activity of these secreted proteinases between the two variants. Growth of the variants on growth factor-reduced Matrigel similarly induced expression of the M r 92 000 progelatinase. The variants exhibited similar chemotactic responses toward laminin. However, the chemotactic response toward fibronectin by LTP cells was significantly increased. MFR5, a monoclonal antibody which selectively blocks function of the 5 chain of the 5ß1 integrin, VLA-5, decreased the chemotactic response toward fibronectin of ND cells by 37%; the chemotactic response by LTP cells was reduced by 49%. This effect was specific for fibronectin-mediated chemotaxis since the chemotaxis toward laminin and invasion through Matrigel were not altered by the presence of MFR5. The surface expression of VLA-5 was significantly increased in LTP cells as compared to ND cells by flow cytometric analysis. These observations suggest that limitation of Tyr and Phe either directly modifies BL6 or selects for subpopulations with altered in vitro invasion, chemotaxis, and integrin expression.  相似文献   
73.
Our objective was to correlate p16, p21cip1, p27kip1, and cyclin E protein expression with the degree of dysplasia on ThinPrep Papanicolaou (Pap) smears using a modified immunoperoxidase staining. Smears read as normal, atypical squamous cells of undetermined significance (ASC-US), low-grade squamous intraepithelial lesion (LSIL), or high-grade SIL (HSIL) were identified and tested for high-risk human papillomavirus (HR-HPV). Additional smears were processed for immunoperoxidase for p16, p21cip1, p27kip1, and cyclin E. Thirty-four smears were satisfactory for study. The p16 was positive in all nine HSIL, in four of nine LSIL, and in one of seven ASC-US. The p27kip1 was positive in all nine HSIL, in eight of nine LSIL, and in one of seven ASC-US. The p21cip1 was positive in all nine HSIL, in one of nine LSIL, and in one of seven ASC-US. Cyclin E was positive in seven of nine HSIL and in one of nine LSIL and in none of the ASC-US smears. Normal smears were negative for all the antigens. There was poor correlation of protein expression and HR-HPV infection. We concluded that p16, p21cip1, p27kip1, and cyclin E can be demonstrated on Pap smears and they are expressed differentially in dysplastic cells, with highest expression in HSIL. The p21cip1 and cyclin E showed the greatest correlation with HSIL.  相似文献   
74.
75.
A novel HybProbe real-time LightCycler PCR assay was developed for confirmation of Neisseria gonorrhoeae in samples positive according to the COBAS AMPLICOR Chlamydia trachomatis/Neisseria gonorrhoeae PCR assay. The new assay amplifies 375 bp of the N. gonorrhoeae 16S rRNA gene and includes an internal amplification control introduced during DNA purification. The assay had 100% specificity because of the high specificity of the HybProbes and primers. Other Neisseria spp. failed to generate positive crossing-point values and melting peaks. The analytical sensitivity for N. gonorrhoeae DNA was 0.5 fg/PCR, corresponding to 0.3 CFU/PCR. Sensitivity was not impaired in the presence of higher DNA concentrations (>or=1000-fold) from Neisseria spp. other than N. gonorrhoeae. The sensitivity was similar to that reported for the COBAS AMPLICOR assay with cervical swab samples. To assess its clinical applicability as a confirmatory test, 38 (2.9%) of 1313 swabs that were positive according to the COBAS AMPLICOR assay were tested using the new in-house assay and the commercially available GenFlow Neisseria test. Twenty-one samples negative according to COBAS AMPLICOR also underwent confirmatory testing. Both confirmatory tests yielded identical results; the 21 negative samples remained negative, and only 11 (28.9%) of the samples positive according to COBAS AMPLICOR were positive after retesting, suggesting a low prevalence (0.84%) of N. gonorrhoeae infection in the study population. These data suggest that the novel real-time PCR assay is an excellent and easy to interpret confirmatory test for the existing COBAS AMPLICOR assay for N. gonorrhoeae.  相似文献   
76.
Infection with the human immunodeficiency virus HIV-1 is associated with the expansion of a CD14lowCD16high monocyte subset in peripheral blood. This subset, which represents a minor subpopulation of monocytes in healthy individuals, increases during HIV infection and, in patients with AIDS, may represent up to 40% of the total circulating monocyte cell population. The CD14lowCD16high circulating monocytes co-express MAX.1, p150,95 and HLADR which are typical of tissue macrophage markers. These cells also express higher levels of intracellular interleukin (IL)-1α and tumor necrosis factor (TNF)-α than the CD14highCD16low monocyte population from the same patients. The CD14lowCD16high cells also express low levels of CD35, CD11a and CD4 in common with normal monocytes. When cultured in vitro, monocytes from HIV-seropositive individuals differentiated within a few hours into an elongated fibroblastoid shape characteristic of migratory cells. Our results suggest that the expansion of the CD14lowCD16high monocyte subset, which produce high amounts of TNF-α and IL-1α, may participate in the immune dysfunction observed during HIV infection.  相似文献   
77.
The ganglioside GD3 has been described as a membrane component of human T cells which is involved in T cell growth. In the present study the activating function of GD3 for human CD4+ and CD8+ T cells was analyzed by five different monoclonal antibodies (mAb) directed against the GD3 molecule. Three mAb U5, Z21 and R24 induced strong proliferation of peripheral blood mononuclear cells and purified CD8+ and CD4+ T cells of normal donors containing less than 5% CD16+ natural killer (NK) cells. In contrast to CD4+ T cells, CD8+ T cells proliferated only weakly in the presence of 15% CD16+ NK cells. The proliferative response of purified CD4+ and CD8+ T cells (<5% NK cells) correlated with the antibody-dependent induction of integral and soluble interleukin-2 (IL-2) receptors and was reduced to 20% by an anti-IL-2 receptor antibody. Our results show, that the GD3 molecule represents an activation molecule for both CD4+ and CD8+ T cells and that CD16+ NK cells selectively inhibit anti-GD3 antibody-induced proliferation of CD8+ T cells.  相似文献   
78.
BACKGROUND: Type-specific persistence of human papillomavirus (HPV) infection can cause invasive cervical cancer. OBJECTIVES: To evaluate the efficacy of HPV detection and typing with a general polymerase chain reaction (PCR)-based genotyping array and to compare it with a type-specific PCR assay. STUDY DESIGN: Four hundred and thirty-three cervical samples were tested with a modified MY11/GP6+ PCR-based reverse-blot assay (EasyChip HPV Blot; King Car, Taiwan [hereafter HPV Blot]) and with 20 genotypes of L1-type-specific PCR (HPV-6, -11, -16, -18, -31, -33, -35, -39, -45, -51, -52, -53, -56, -58, -59, -62, -66, -68, -70, and -71 [CP8061]). RESULTS: The concordance of the two tests in determining HPV positivity was 96.8% (419/433), with a Cohen's kappa=0.93 (95% CI: 0.90-0.97) and McNemar's test of P=1.0, which indicates excellent agreement. The overall concordance of the two tests in the identification of type-specific HPV was 91.0% (394/433). Sensitivity (90-100%), specificity (99.2-100%), and accuracy (98.6-100%) rates of HPV Blot against the gold standard were satisfactory for HPV-16, -18, -58, -33, -52, -39, -45, -31, -51, -70 while HPV-71 (63.6%) had suboptimal sensitivity. Though the kappa values between the two tests for many individual genotypes could not be reliably calculated because of low positivity, the kappa values for HPV-16, -52, and -58 were excellent (0.93, 0.96, and 0.95, respectively). CONCLUSION: The modified MY11/GP6+ PCR-based HPV Blot assay is accurate and sensitive for detection and genotyping of HPV in cervical swab samples.  相似文献   
79.
We investigated the aberrant promoter hypermethylation of p16, p15 and p14 genes and loss of heterozygosity (LOH) at 9p21-22 in 48 cases of adenocarcinoma of the lung. The frequencies of hypermethylation of genes were as follows: p16, 25.0%; p15, 22.9%; and p14, 18.8%. The frequency of LOH at chromosome 9p21-22 was 60.9%. The frequency of two-hit inactivation of the p16 gene by hypermethylation and LOH was 21.7%. Two-hit inactivation of the p16 gene showed loss of protein expression and was significantly correlated with tumor size, tumor grade and the Ki-67 labeling index. Hypermethylation of the p16 gene was not significantly correlated with hypermethylation of the p15 and p14 genes, both of which are close to the p16 gene locus, suggesting that hypermethylation of these genes occurs selectivity. In conclusion, biallelic inactivation of the p16 gene by hypermethylation and LOH might cause loss of p16 expression and play an important role in the development of adenocarcinoma of the lung. Therefore, controlling and monitoring for hypermethylation of the p16 gene may be partially useful for treatment and early diagnosis of adenocarcinoma of the lung.  相似文献   
80.
目的:观察参杞合剂(SQ)在体内、外对小鼠腹水型肝癌细胞株(HcaF16A3)细胞周期及凋亡的影响。方法:用SQ对荷瘤小鼠连续胃饲治疗10d,观察其NK细胞/Mφ的杀伤活性及细胞周期的改变。用流式细胞仪检测SQ对HcaF16A3细胞增殖的抑制作用与诱导凋亡的作用。结果:SQ的抑瘤率为65.68%。流式细胞仪检测发现,SQ可使肿瘤细胞的细胞周期阻滞到S期,并在体外诱导其凋亡。结论:SQ在体内、外均有抑瘤作用,其机制与细胞周期阻滞继而诱发凋亡有关。  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