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   3864篇
  免费   216篇
  国内免费   24篇
耳鼻咽喉   131篇
儿科学   121篇
妇产科学   77篇
基础医学   519篇
口腔科学   182篇
临床医学   360篇
内科学   1010篇
皮肤病学   96篇
神经病学   245篇
特种医学   81篇
外科学   461篇
综合类   15篇
预防医学   120篇
眼科学   76篇
药学   313篇
中国医学   10篇
肿瘤学   287篇
  2022年   23篇
  2021年   61篇
  2020年   40篇
  2019年   53篇
  2018年   66篇
  2017年   56篇
  2016年   56篇
  2015年   60篇
  2014年   73篇
  2013年   97篇
  2012年   187篇
  2011年   148篇
  2010年   105篇
  2009年   95篇
  2008年   175篇
  2007年   147篇
  2006年   137篇
  2005年   153篇
  2004年   156篇
  2003年   155篇
  2002年   164篇
  2001年   156篇
  2000年   165篇
  1999年   153篇
  1998年   44篇
  1997年   42篇
  1996年   41篇
  1995年   34篇
  1994年   30篇
  1993年   30篇
  1992年   98篇
  1991年   76篇
  1990年   85篇
  1989年   102篇
  1988年   89篇
  1987年   101篇
  1986年   91篇
  1985年   72篇
  1984年   58篇
  1983年   44篇
  1979年   50篇
  1978年   26篇
  1977年   26篇
  1975年   19篇
  1974年   29篇
  1972年   20篇
  1970年   19篇
  1968年   19篇
  1967年   18篇
  1966年   24篇
排序方式: 共有4104条查询结果,搜索用时 15 毫秒
121.
Chromosomal numerical abnormalities (CNA) are ubiquitous in human cancers. However, the question of when a CNA occurs in the course of tumor generation and progression, is controversial. Recent radiological scrutiny has enabled the identification of small peripheral lesions in the lung. A chromosome-wide investigation encompassing almost all the chromosomal centromeres was performed using modified fluorescence in situ hybridization on the archived pathological samples of 16 atypical adenomatous hyperplasia (AAH) and 30 lung adenocarcioma (AdCa) specimens including those smaller than 1 cm in size. The prevalence of the gain was more extensive in male than in female patients, and in non-smokers than in smokers. It tended to be greater in poorly differentiated AdCa, in moderately differentiated AdCa, and in well-differentiated AdCa cases, in that order. Most AAH had non-specific gains affecting all the examined chromosomes. The prevalence of the gain differed significantly between AAH and bronchioloalveolar carcinoma (BAC) 1 cm. It is proposed that the CNA is a distinct phenomenon occurring in the early or premalignant stage of lung AdCa, and that the CNA itself may not be a sequel in the carcinogenetic process, but a driving factor in carcinogenesis.  相似文献   
122.
An immunochromatographic test for the simultaneous detection of Babesia caballi- and B. equi-specific antibodies (BceICT) was developed using a recombinant B. caballi 48-kDa rhoptry protein (rBc48) and a recombinant truncated B. equi merozoite antigen 2 (rEMA-2t). An evaluation of the ability of the BceICT to detect antibodies in sera from uninfected horses and experimentally infected horses showed high sensitivities and specificities of 83.3% (10/12 sera) and 92.9% (52/56 sera), respectively, for the anti-B. caballi antibody and 94.1% (16/17 sera) and 88.2% (45/51 sera), respectively, for the anti-B. equi antibody. Results from the detection of antibodies in field-collected sera indicated that the BceICT results corresponded with those of enzyme-linked immunosorbent assays (ELISA), showing 91.8% correspondence (67/73 sera) for B. caballi and 95.9% correspondence (70/73 sera) for B. equi, and that the BceICT results also corresponded with the ICT for B. caballi and for B. equi, both of which were 98.2% (55/56 sera). The comparable results of the ICT and ELISA and the simplicity and rapidity of the performance of the ICT suggest that the BceICT would be a feasible test for the simultaneous serodiagnosis of both agents of equine babesiosis in the field.  相似文献   
123.
Butylated hydroxyanisole (BHA) and 1,2-bis(2-pyridyl)ethylene (2PY-e) are phase II drug metabolizing enzyme inducers which cause hepatomegaly without hepatocyte hypertrophy and induce glutathione S-transferase Yp (GST Yp, pi-class GST), which is known as a tumor marker. To evaluate the relationship between GST Yp induction and hepatocyte proliferation, male F344/DuCrj rats were treated with BHA, 2PY-e, or phenobarbital (PB) for three or seven days. All three chemicals caused increases in liver weight after three and seven days. Immunohistochemical examinations revealed that BHA and 2PY-e induced GST Yp in the hepatocytes of the periportal and centrilobular areas at three and seven days, respectively, whereas PB did not. Significant increases in the BrdU labeling indices were found in the livers of rats in each of the three-day treatment groups, but the labeling index of rat livers treated with BHA was decreased to the control level at seven days, although the high labeling indices of 2PY-e and PB persisted at seven days. Double immunostaining confirmed that BrdU-positive nuclei corresponded to GST Yp-positive hepatocytes in both BHA and 2PY-e treated rats. These results suggest that the GST Yp induction caused by BHA or 2PY-e has some kind of relationship with hepatocyte proliferation.  相似文献   
124.
RAG1/GFP knockin mice were exploited to isolate and characterize fetal lymphoid progenitors. CD11b and IL-7Ralpha are expressed in a developmental stage-dependent fashion, revealing how substantial numbers of early lymphoid progenitors were discarded or neglected in previous studies. The myeloerythroid potential of fetal progenitors in clonal assays declined in synchrony with activation of the RAG1 locus but was not completely extinguished. Lymphoid differentiation corresponded to patterns of gene expression previously found for adult marrow, but no fraction of fetal liver was enriched with respect to B + T progenitors. Also, unlike adults, fetal lymphoid progenitors transiently expressed endothelial cell markers. These findings help to reconcile discrepancies in previous reports and suggest that the fetal immune system arises via unique mechanisms.  相似文献   
125.
Charcot-Marie-Tooth disease type 4C (CMT4C) is an autosomal recessive peripheral neuropathy reported in several Algerian families. The gene locus of this disease has been narrowed to 5q31-33. Recently, a missense mutation in the gene for the kinesin superfamily KIF1B was reported as the cause of Charcot Marie Tooth disease type 2A (CMT2A). We suspected that Rab6KIFL, one of the kinesin superfamily proteins, might be involved in the pathophysiology of CMT4C, because Rab6KIFL gene is located in 5q31. The coding regions of the Rab6KIFL gene of genomic DNA derived from one Algerian family with CMT4C were analyzed by direct sequencing. No mutation in Rab6KIFL gene was found in this family. Further investigation is necessary to identify the causative gene for CMT4C.  相似文献   
126.
Regional lymph node metastasis in gastric cancer is a definitive indicator of the patient’s prognosis. The goal of this study was to identify the predictors for lymph node metastasis among all the possible histopathological parameters, especially by conducting an objective discrimination of the lymphatic and blood vessels. A total of 210 resected primary gastric cancers with or without lymph node metastasis were evaluated based on the conventional histopathological parameters together with immunohistochemistry using antisera-recognizing lymphatic endothelial hyaluronan receptor-1 (LYVE-1), von Willebrand factor, and lymphangiogenesis promoter vascular endothelial growth factor-C (VEGF-C) antibodies. A multivariate regression analyses of the results indicated that only lymphatic invasion was a significant independent predictor of lymph node metastasis at any stage of cancer invasion. VEGF-C expression was partially related to lymph node metastasis in early gastric cancer. The identification of lymphatic invasion by LYVE-1 antibody is therefore useful to predict regional lymph node metastasis in gastric cancer.  相似文献   
127.
128.
129.
Phenol oxidase (PO, EC 1.10.3.1) activity was detected in the hemolymph of the fourth instar nymphs of the argasid tick, Ornithodoros moubata, with peak levels corresponding to the days before the majority of the nymphs had molted, suggestive of a protective role of PO during the ecdysial phase. Higher PO activity was detected in plasma relative to the hemolymph and was negligible in hemocytes. The concentration of the hemolymph and plasma assayed clearly influenced the level of PO activity, and was significantly reduced ( P<0.005) after treatment with 1-phenyl-2 thiourea, a specific PO inhibitor. This is the first report of the existence of PO in the hemolymph and plasma of a soft tick species. The regulation of PO activity and its precise role in soft tick immunity, particularly during the ecdysial phase, are interesting and need to be examined further.  相似文献   
130.
The cellular localization of Babesia bovis rhoptry-associated protein 1 (RAP-1) and its erythrocyte-binding affinity were examined with anti-RAP-1 antibodies. In an indirect immunofluorescent antibody test, RAP-1 was detectable in all developmental stages of merozoites and in extracellular merozoites. In the early stage of merozoite development, RAP-1 appears as a dense accumulation, which later thins out and blankets the host cell cytoplasm, but retains a denser mass around newly formed parasite nuclei. The preferential accumulations of RAP-1 on the inner surface of a host cell membrane and bordering the parasite's outer surface were demonstrable by immunoelectron microscopy. An erythrocyte-binding assay with the lysate of merozoites demonstrated RAP-1 binding to both bovine and equine erythrocytes. Anti-RAP-1 monoclonal antibody 1C1 prevented the interaction of RAP-1 with bovine erythrocytes and significantly inhibited parasite proliferation in vitro. With the recombinant RAP-1, the addition of increasing concentrations of Ca(2+) accentuated its binding affinity with bovine erythrocytes. The present findings lend support to an earlier proposition of an erythrocytic binding role for RAP-1 expressed in B. bovis merozoites and, possibly, its involvement in the escape of newly formed merozoites from host cells.  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