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   761篇
  免费   53篇
  国内免费   5篇
耳鼻咽喉   6篇
儿科学   50篇
妇产科学   11篇
基础医学   56篇
口腔科学   15篇
临床医学   76篇
内科学   107篇
皮肤病学   9篇
神经病学   7篇
特种医学   143篇
外科学   127篇
综合类   30篇
预防医学   20篇
眼科学   4篇
药学   20篇
肿瘤学   138篇
  2023年   1篇
  2022年   9篇
  2021年   10篇
  2020年   4篇
  2019年   11篇
  2018年   14篇
  2017年   8篇
  2016年   15篇
  2015年   14篇
  2014年   34篇
  2013年   31篇
  2012年   15篇
  2011年   11篇
  2010年   13篇
  2009年   10篇
  2008年   15篇
  2007年   20篇
  2006年   14篇
  2005年   8篇
  2004年   17篇
  2003年   13篇
  2002年   12篇
  2001年   14篇
  2000年   14篇
  1999年   25篇
  1998年   40篇
  1997年   38篇
  1996年   41篇
  1995年   34篇
  1994年   37篇
  1993年   25篇
  1992年   13篇
  1991年   13篇
  1990年   7篇
  1989年   23篇
  1988年   23篇
  1987年   23篇
  1986年   25篇
  1985年   21篇
  1984年   19篇
  1983年   20篇
  1982年   6篇
  1981年   16篇
  1980年   10篇
  1979年   12篇
  1978年   4篇
  1977年   3篇
  1976年   7篇
  1975年   5篇
  1974年   2篇
排序方式: 共有819条查询结果,搜索用时 15 毫秒
31.
Kaplan  AP; Gruber  B; Harpel  PC 《Blood》1985,66(3):636-641
An enzyme-linked immunosorbent assay has been developed for the quantitation of activated Hageman factor-C1 inactivator (HF-C1 INH) complexes. Addition of increasing quantities of either of the major forms of activated Hageman factor (HFa or HFf) to normal plasma or to Hageman factor-deficient plasma leads to a dose-dependent increase in activated HF-C1 INH complexes. As little as 0.5 micrograms/mL of activated HF added to plasma can be detected, corresponding to activation of approximately 2% of plasma HF. The sensitivity of the assay is increased at least tenfold when complexes are formed in HF- deficient plasma, indicating competition between unactivated HF and activated HF-C1 INH complexes for binding to the antibody. Specificity is demonstrated in that addition of activated HF to hereditary angioedema plasma yields less than 1% of the activated HF-C1 INH complex formation obtained with normal plasma. Kaolin activation of HF- deficient plasma yields no detectable complex formation. Kaolin activation of prekallikrein-deficient plasma demonstrates a time- dependent increase in formation of activated HF-C1 INH complex consistent with the ability of HF in this plasma to autoactivate as the time of incubation with the surface is increased. Kaolin treatment of high-molecular weight (HMW) kininogen-deficient plasma yields an even more profound abnormality in the rate of formation of activated HF-C1 INH complexes reflecting the complex role of HMW kininogen in the initiation of contact activation. Although addition of corn inhibitor to plasma prevents activated HF-C1 INH complex formation, it does not inhibit activated HF sufficiently fast to prevent prekallikrein activation.  相似文献   
32.
Amrein  PC; Stossel  TP 《Blood》1980,56(3):442-447
Proteases can complicate the characterization of proteins from cells, especially human polymorphonuclear leukocytes (PMN), which contain abundant neutral proteases. We tested the ability of agents to inhibit proteolysis, with special reference to the subunit polypeptides of the contractile proteins actin, myosin, and actin-binding protein (ABP). Phenylmethylsulfonyl fluoride (PMSF), O-phenanthroline, EGTA, EDTA, N- ethylmaleimide, alone or in combinations, failed to prevent extensive proteolysis of the PMN proteins during solubilization of cells with dodecyl sulfate. These inhibitors and also alpha-1-antitrypsin and soybean trypsin inhibitor similarly could not prevent proteolysis during homogenization of cells in cold isosomolar sucrose. Treatment of PMN with greater than or equal to mM diisopropylfluorophosphate (DFP) prior to solubilization or homogenization markedly inhibited proteolysis. PMSF and DFP were equally effective in inhibiting proteolysis in PMN extracts, suggesting that the efficacy of DFP may result from its permeation of intact cells and granules before barriers are disrupted by detergents or homogenization. Treatment of PMN with DFP under conditions inhibiting proteolysis did not affect their rate of phagocytosis. We recommend the use of DFP in future studies correlating functions and protein structure of PMN.  相似文献   
33.
Niskanen  E; Gorman  J; Isakson  PC 《Blood》1987,70(6):1784-1789
In this study we detected a factor that stimulates the proliferation of bone marrow-derived hematopoietic precursors in diffusion chambers implanted in mice. This factor, called diffusible colony-stimulating factor (D-CSF), was found in medium conditioned in the presence of spleen and peripheral blood cells from mice with B cell leukemia (BCL1). After the administration of D-CSF, the number of colonies formed in the plasma clot inside the chamber (CFU-DG) was increased, as were the number of hematopoietic precursors (CFU-MIX, CFU-S, CFU-C, and BFU-E) as judged by a subculture of diffusion chamber contents. Depletion of macrophages and T cells from the spleen cell suspension did not decrease the production of D-CSF, thereby indicating that it was derived from B cells. Neoplastic BCL1 cells appear to be the source because D-CSF could not be detected in medium conditioned with normal B cells. BCL1-conditioned medium (CM) did not enhance CFU-MIX, BFU-E, and CFU-C colony formation in vitro, which suggested that D-CSF is different from multi-CSF, EPA, or CSF. The addition of BCL1 CM to multi- CSF-, erythroid potentiating activity (EPA), and CSF (EL-4CM)- containing cultures had no effect on CFU-MIX, BFU-E, and CFU-C colony formation, thus indicating the absence of a synergistic or inhibitory activity. On the other hand, EL-4 CM, which stimulates CFU-MIX, BFU-E, and CFU-C in vitro, had no effect on CFU-DG in vivo. Biochemical characterization of BCL1 CM revealed that D-CSF is relatively heat stable and loses its bioactivity with protease treatments. It binds to lentil-lectin, according to gel-filtration chromatography has a relative molecular weight of approximately 43,000, and on reverse-phase high-performance liquid chromatography elutes with acetonitrile. These data also indicate that transformed B cells may serve as a source for hematopoietic regulators that act on hematopoietic precursors in vivo.  相似文献   
34.

Objective

To collect, compile and evaluate publicly available national health accounts (NHA) reports produced worldwide between 1996 and 2010.

Methods

We downloaded country-generated NHA reports from the World Health Organization global health expenditure database and the Organisation for Economic Co-operation and Development (OECD) StatExtract website. We also obtained reports from Abt Associates, through contacts in individual countries and through an online search. We compiled data in the four main types used in these reports: (i) financing source; (ii) financing agent; (iii) health function; and (iv) health provider. We combined and adjusted data to conform with OECD’s first edition of A system of health accounts manual, (2000).

Findings

We identified 872 NHA reports from 117 countries containing a total of 2936 matrices for the four data types. Most countries did not provide complete health expenditure data: only 252 of the 872 reports contained data in all four types. Thirty-eight countries reported an average not-specified-by-kind value greater than 20% for all data types and years. Some countries reported substantial year-on-year changes in both the level and composition of health expenditure that were probably produced by data-generation processes. All study data are publicly available at http://vizhub.healthdata.org/nha/.

Conclusion

Data from NHA reports on health expenditure are often incomplete and, in some cases, of questionable quality. Better data would help finance ministries allocate resources to health systems, assist health ministries in allocating capital within the health sector and enable researchers to make accurate comparisons between health systems.  相似文献   
35.
36.
A genetic contribution to a broad range of epilepsies has been postulated, and particularly copy number variations (CNVs) have emerged as significant genetic risk factors. However, the role of CNVs in patients with epilepsies with complex phenotypes is not known. Therefore, we investigated the role of CNVs in patients with unclassified epilepsies and complex phenotypes. A total of 222 patients from three European countries, including patients with structural lesions on magnetic resonance imaging (MRI), dysmorphic features, and multiple congenital anomalies, were clinically evaluated and screened for CNVs. MRI findings including acquired or developmental lesions and patient characteristics were subdivided and analyzed in subgroups. MRI data were available for 88.3% of patients, of whom 41.6% had abnormal MRI findings. Eighty-eight rare CNVs were discovered in 71 out of 222 patients (31.9%). Segregation of all identified variants could be assessed in 42 patients, 11 of which were de novo. The frequency of all structural variants and de novo variants was not statistically different between patients with or without MRI abnormalities or MRI subcategories. Patients with dysmorphic features were more likely to carry a rare CNV. Genome-wide screening methods for rare CNVs may provide clues for the genetic etiology in patients with a broader range of epilepsies than previously anticipated, including in patients with various brain anomalies detectable by MRI. Performing genome-wide screens for rare CNVs can be a valuable contribution to the routine diagnostic workup in patients with a broad range of childhood epilepsies.  相似文献   
37.

Background

Tumor infiltrating lymphocytes (TIL) and histological regression in primary melanoma are generally considered indicators of the local immune response but their roles as prognostic factors have been variably reported. We examined the prognostic role of these variables in patients with high risk (T4) primary melanomas in a large series of patients with long-term follow-up.

Methods

From a prospectively maintained cohort of patients diagnosed between 1971 and 2004, 161 patients were retrospectively identified with primary thick melanomas (>4 mm), no clinical evidence of regional nodal disease (RND) at diagnosis and complete histopathologic data. Univariate and multivariate Cox regression models were performed to identify clinical and histopathologic predictors of disease-specific survival (DSS) and to identify subgroups with differential survival.

Results

Factors significantly associated with decreased DSS by univariate analysis included male gender, age ≥ 60 years, axial anatomic location, presence of ulceration, RND, absence of TIL, and presence of regression. In the final multivariate model, TIL and regression, as interacting variables, and RND status remained significantly associated with DSS. In the presence of TIL, concomitant regression was associated with significantly worse survival (p ≤ 0.0001). In the absence of TIL, there was no effect of regression on survival (p = 0.324).

Conclusions

Primary TIL and regression status and RND status are independently associated with melanoma-specific survival in patients with T4 melanomas; presence of TIL in the primary melanoma with concomitant radial growth phase regression is associated with a poor prognosis and may reflect an ineffective local regional immune response.  相似文献   
38.
39.
40.
Andrews  PC; Babior  BM 《Blood》1984,64(4):883-890
A study was conducted on the phosphorylation of proteins in the neutrophil cytosol in response to phorbol myristate acetate (PMA) and N- formyl-methionyl-leucyl-phenylalanine (fMLP). Autoradiography of gel electrophoretograms prepared from neutrophils incubated with 32Pi in the presence and absence of the activators showed nine proteins whose state of phosphorylation was affected by neutrophil activation. 32P was gained by eight of these proteins and was lost by the ninth. For all but one of these proteins, the change in the extent of labeling appeared to reach completion by one to two minutes. It was possible to quantitate the changes in 32P content of three of the nine proteins. One of these was the 20-kD protein that lost label when the neutrophils were activated. Quantitation showed that over half the 32P present in this protein in the resting state was gone within 0.2 minutes after activation. The other two were proteins weighing 11 and 69 kD. The phosphorylation characteristics of these two proteins differed, depending on whether activation had been carried out with PMA or fMLP. These differences in protein phosphorylation support other evidence suggesting that PMA and fMLP do not activate neutrophils by identical biochemical pathways. Differences in phosphorylation between resting and activated cells were not affected by dibutyryl cyclic guanosine monophosphate (cGMP), dibutyryl cyclic adenosine monophosphate (cAMP), theophylline, aspirin, hydrocortisone, or colchicine. The differences were abolished, however, by 30 mumol/L trifluoperazine. This finding is consistent with the hypothesis that the calcium/calmodulin system plays a biochemical role in the activation of neutrophils.  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