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   328949篇
  免费   38172篇
  国内免费   140篇
  2018年   2954篇
  2016年   4027篇
  2015年   5622篇
  2014年   6575篇
  2013年   9351篇
  2012年   10541篇
  2011年   10664篇
  2010年   7182篇
  2009年   6444篇
  2008年   9286篇
  2007年   9745篇
  2006年   9047篇
  2005年   8740篇
  2004年   8807篇
  2003年   8487篇
  2002年   8393篇
  2001年   14393篇
  2000年   14376篇
  1999年   11527篇
  1998年   4034篇
  1997年   4091篇
  1996年   3883篇
  1995年   3904篇
  1994年   3890篇
  1993年   3756篇
  1992年   9883篇
  1991年   9436篇
  1990年   9259篇
  1989年   8990篇
  1988年   8368篇
  1987年   8017篇
  1986年   7247篇
  1985年   7349篇
  1984年   6085篇
  1983年   5333篇
  1982年   4231篇
  1981年   3727篇
  1980年   3553篇
  1979年   6119篇
  1978年   4572篇
  1977年   4300篇
  1976年   3979篇
  1975年   4310篇
  1974年   4660篇
  1973年   4721篇
  1972年   4360篇
  1971年   4068篇
  1970年   3436篇
  1969年   3337篇
  1968年   2962篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
1.
The development of flow cytometric biomarkers in human studies and clinical trials has been slowed by inconsistent sample processing, use of cell surface markers, and reporting of immunophenotypes. Additionally, the function(s) of distinct cell types as biomarkers cannot be accurately defined without the proper identification of homogeneous populations. As such, we developed a method for the identification and analysis of human leukocyte populations by the use of eight 10-color flow cytometric protocols in combination with novel software analyses. This method utilizes un-manipulated biological sample preparation that allows for the direct quantitation of leukocytes and non-overlapping immunophenotypes. We specifically designed myeloid protocols that enable us to define distinct phenotypes that include mature monocytes, granulocytes, circulating dendritic cells, immature myeloid cells, and myeloid derived suppressor cells (MDSCs). We also identified CD123 as an additional distinguishing marker for the phenotypic characterization of immature LIN-CD33+HLA-DR- MDSCs. Our approach permits the comprehensive analysis of all peripheral blood leukocytes and yields data that is highly amenable for standardization across inter-laboratory comparisons for human studies.  相似文献   
2.
ImportanceSudden cardiac death is a leading cause of mortality in psychiatric patients. Long QT (LQT) is common in this population and predisposes to Torsades-de-Pointes (TdP) and subsequent mortality.ObjectiveTo estimate the cost-effectiveness of electrocardiographic screening to detect LQT in psychiatric inpatients.ResultsIn the base-case scenario, the numbers of patients needed to screen were 1128 and 2817 to avoid one TdP and one death, respectively. The ICER of systematic ECG screening was $8644 (95%CI, 3144-82 498) per QALY. The probability of cost-effectiveness was 96% at a willingness-to-pay of $50 000 for one QALY. In sensitivity analyses, results were sensitive to the case-fatality of TdP episodes and to the TdP reduction following the diagnosis of LQT.

Conclusion and Relevance

In psychiatric hospitals, performing systematic ECG screening at admission help reduce the number of sudden cardiac deaths in a cost-effective fashion.  相似文献   
3.
4.
5.
6.
T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignant neoplasm of the lymphocyte precursors that suffered malignant transformation arresting the lymphoid cell differentiation. Clinical studies revealed monoor, more rarely, oligoclonal nature of the disease. A precise identification of malignant clone markers is both the crucial stage of early diagnostics and the essential prognostic factor for therapeutic treatment. Here we present an improved system for unbiased detection of lymphoblastic clones in bone marrow aspirates of T-ALL patients. The system based on multiplex PCR of rearranged T-cell receptor locus (TRB) and straightforward sequencing of the resulted PCR fragments. Testing of the system on genomic DNA from Jurkat cell line and four clinical bone marrow aspirates revealed a set of unique TRB rearrangements that precisely characterize each of tested samples. Therefore, the outcome of the system produces highly informative molecular genetic markers for further monitoring of minimal residual disease in T-ALL patients.  相似文献   
7.
Four classes of Xanthomonas campestris mutants were identified with respect to pectate lyase. Pectate lyase production in the wild-type and classes I and IIb mutants was partially dependent on the growth-phase whereas in classes IIa and III it was totally dependent. Enzyme activity in some of the mutants was constitutive and resistant to catabolite repression.  相似文献   
8.
Abstract: The glial fibrillary acidic protein (GFAP) content was investigated using immunoblotting techniques in the septum and hippocampus of the rat after bilateral lateral fimbria transection. Seven days after surgery GFAP content increased significantly both in the septum (140% of control) and hippocampus (120% in dorsal, the less denervated, and 145% in the most denervated ventral part), indicating the occurrence of reactive gliosis. The GM1 treatment caused statistically significant attenuation of GFAP increment in all hippocampal parts. In contrast, GM1 treatment has no influence on the increase of GFAP content in the septum. Results suggest a differential effect of GM1 on the two gliotic reactions formed as a consequence of the lesion at the level of the source of innervation (septum) and the target (hippocampus).  相似文献   
9.
10.
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