全文获取类型
收费全文 | 1016篇 |
免费 | 106篇 |
国内免费 | 61篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 28篇 |
妇产科学 | 36篇 |
基础医学 | 200篇 |
口腔科学 | 11篇 |
临床医学 | 124篇 |
内科学 | 183篇 |
皮肤病学 | 9篇 |
神经病学 | 29篇 |
特种医学 | 156篇 |
外科学 | 167篇 |
综合类 | 49篇 |
预防医学 | 75篇 |
眼科学 | 7篇 |
药学 | 76篇 |
中国医学 | 1篇 |
肿瘤学 | 29篇 |
出版年
2021年 | 14篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 23篇 |
2012年 | 23篇 |
2011年 | 20篇 |
2010年 | 23篇 |
2009年 | 31篇 |
2008年 | 21篇 |
2007年 | 97篇 |
2006年 | 42篇 |
2005年 | 57篇 |
2004年 | 23篇 |
2003年 | 35篇 |
2002年 | 28篇 |
2001年 | 25篇 |
2000年 | 32篇 |
1999年 | 28篇 |
1998年 | 35篇 |
1997年 | 42篇 |
1996年 | 31篇 |
1995年 | 27篇 |
1994年 | 16篇 |
1993年 | 27篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 20篇 |
1989年 | 32篇 |
1988年 | 17篇 |
1987年 | 18篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 14篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1975年 | 20篇 |
1974年 | 14篇 |
1973年 | 13篇 |
1972年 | 13篇 |
1971年 | 12篇 |
1970年 | 11篇 |
1969年 | 10篇 |
1968年 | 13篇 |
1966年 | 19篇 |
1965年 | 8篇 |
排序方式: 共有1183条查询结果,搜索用时 118 毫秒
31.
Sergio Crosby Doanh Tran David Cocke El-Shazly M. Duraia Gary W. Beall 《Materials》2014,7(10):7048-7058
Hydrotalcites have many important applications in catalysis, wastewater treatment, gene delivery and polymer stabilization, all depending on preparation history and treatment scenarios. In catalysis and polymer stabilization, thermal decomposition is of great importance. Hydrotalcites form easily with atmospheric carbon dioxide and often interfere with the study of other anion containing systems, particularly if formed at room temperature. The dehydroxylation and decomposition of carbonate occurs simultaneously, making it difficult to distinguish the dehydroxylation mechanisms directly. To date, the majority of work on understanding the decomposition mechanism has utilized hydrotalcite precipitated at room temperature. In this study, evolved gas analysis combined with thermal analysis has been used to show that CO2 contamination is problematic in materials being formed at RT that are poorly crystalline. This has led to some dispute as to the nature of the dehydroxylation mechanism. In this paper, data for the thermal decomposition of the chloride form of hydrotalcite are reported. In addition, carbonate-free hydrotalcites have been synthesized with different charge densities and at different growth temperatures. This combination of parameters has allowed a better understanding of the mechanism of dehydroxylation and the role that isomorphous substitution plays in these mechanisms to be delineated. In addition, the effect of anion type on thermal stability is also reported. A stepwise dehydroxylation model is proposed that is mediated by the level of aluminum substitution. 相似文献
32.
Joshua J. Oliver Matthew J. Streitz Jessica M. Hyams Jackson P. Beall Brit Long Michael D. April 《The American journal of emergency medicine》2019,37(1):177.e5-177.e6
This paper discusses a possible weakness of the HEART Pathway specific to patients identified as high risk, requiring admission for inpatient risk stratification. Emergency Department (ED) crowding is at an all-time high and the possibility that many of these patients will board in the ED for a period of time before they are transported to an inpatient ward is becoming more likely. Given troponins peak at 6?h after the initial cardiac injury, it is plausible an initial troponin could still remain negative upon arrival. Extending the HEART Pathway to include a 3-hour delta troponin for admitted patients boarded in the emergency department may help alert the patient's inpatient team of those requiring more aggressive evaluations or more timely interventions. The case discussed herein highlights the course of a patient who was admitted to a medicine floor for chest pain along the HEART Pathway. After remaining in the ED for 3?h following admission a second troponin was drawn that resulted in the diagnosis of a non-ST segment myocardial infarction. The patient then received further management in the ED and a change in admission to the Cardiac Care Unit instead of the medicine floor. The patient ultimately received a Coronary Artery Bypass Graft during admission. If the patient had not had the second troponin while in the ED this care would have been delayed. 相似文献
33.
Signal transduction by the platelet Fc receptor 总被引:6,自引:1,他引:6
We have evaluated the mechanism by which crosslinking human platelet Fc receptor (FcR) for IgG triggers platelet aggregation and the platelet release reaction. Platelet FcR was crosslinked by incubating purified human platelets with anti-FcRII monoclonal antibody and F(ab')2 anti- mouse Ig. The resultant [Ca2+]i increase, monitored by Fura-2 and measured in the absence of extracellular Ca2+, reached a peak of 750 +/- 50 nmol/L. The effects of cyclooxygenase inhibitors, aspirin and indomethacin, and a phospholipase A2 inhibitor, dibromoacetophenone, were examined. Regardless of the inhibitor, at least 25% of the [Ca2+]i increase remained. Thrombin (0.2 U/mL) stimulated an immediate [Ca2+]i increase that reached 1.95 +/- 0.8 mumol/L. The [Ca2+]i increase generated by thrombin was only slightly reduced by these inhibitors. Crosslinking the FcRII of platelets resulted in a fivefold increase in the production of [3H]inositol phosphates, (IP) which, in the absence of extracellular Ca2+ was insensitive to aspirin. The activation of a [Ca2+]i increase along with the measured increases in IP indicate that FcRII crosslinking leads to the activation of phospholipase C (PLC). In contrast to thrombin, platelet activation via FcRII depends to a large extent on arachidonic acid metabolites. However, neither cyclooxygenase nor phospholipase A2 inhibitors completely blocked FcRII-stimulated [Ca2+]i increase. These observations led us to propose that crosslinking of platelet FcRII initially activates PLC. 相似文献
34.
CL Sanchez CS Biskup S Herpertz TJ Gaber CM Kuhn SH Hood FD Zepf 《The international journal of neuropsychopharmacology / official scientific journal of the Collegium Internationale Neuropsychopharmacologicum (CINP)》2015,18(10)
The neurotransmitters serotonin and dopamine both have a critical role in the underlying neurobiology of different behaviors. With focus on the interplay between dopamine and serotonin, it has been proposed that dopamine biases behavior towards habitual responding, and with serotonin offsetting this phenomenon and directing the balance toward more flexible, goal-directed responding. The present focus paper stands in close relationship to the publication by Worbe et al. (2015), which deals with the effects of acute tryptophan depletion, a neurodietary physiological method to decrease central nervous serotonin synthesis in humans for a short period of time, on the balance between hypothetical goal-directed and habitual systems. In that research, acute tryptophan depletion challenge administration and a following short-term reduction in central nervous serotonin synthesis were associated with a shift of behavioral performance towards habitual responding, providing further evidence that central nervous serotonin function modulates the balance between goal-directed and stimulus-response habitual systems of behavioral control. In the present focus paper, we discuss the findings by Worbe and colleagues in light of animal experiments as well as clinical implications and discuss potential future avenues for related research. 相似文献
35.
36.
Robert W. Wannemacher Francis A. Beall Peter G. Canonico Richard E. Dinterman Clayton L. Hadick Harold A. Neufeld 《Metabolism: clinical and experimental》1980,29(3):201-212
To investigate the effects of bacterial infection on glucose and alanine metabolism, a variety of studies were carried out in rat and monkey models. These included glucose turnover by a pulse-dose technique in infected rats; alanine and glucose production and utilization in control and septic monkeys; in vivo measurement of gluconeogenesis in rats, with and without an alanine load; the in vitro rate of glucose formation from various substrates by isolated liver perfusion and hepatic cells; and in vivo rates of oxidation of glucose labeled with 14C at the 1 or 6 carbon position. In rats, glucose turnover was markedly accelerated 24 hr after inoculation of either 104 or 107Streptococcus pneumoniae. Glucose utilization and production were also accelerated during illness and early recovery from a pneumococcal infection in monkeys. The rates of gluconeogenesis as measured by either a pulse technique in rats or continuous infusion of labeled alanine in monkey were significantly elevated during pneumococcal septicemia. During the agonal stages (107) of the pneumococcal infection in rat, an alanine load resulted in a decreased rate of labeled glucose production and an increase in plasma glucose when compared to values of fasted control rats. However, early illness caused similar or increased rates of glucose production from alanine in vivo. Similar reduced rates of glucose formation were observed when the isolated livers or hepatocytes from rats during the agonal stages of infection were perfused with excess quantities of gluconeogenic substrates. Thus, in the rat, gluconeogenic capacity (ability to form glucose from excess substrates) appears to decrease only during the agonal stages of pneumococcal infection. During acute pneumococcal sepsis in the rhesus monkey, alanine production and utilization were significantly elevated and it was estimated that over 90% of the newly produced alanine was utilized for glucose synthesis. When arterial-venous differences were measured across the hindquarters, significantly more alanine was released, presumably from skeletal muscle of the septic monkey, compared to the recovery period or in the control groups. Thus, the increase in glucose synthesis in both rat and monkey appears to be correlated with substrate availability and kinetic rate, rather than gluconeogenic capacity of the liver. The major increase in glucose utilization during both S. pneumoniae and Francisella tularensis live vaccine strain (LVS) infections in rat was a progressive elevation in the rate of oxidation via the pentose phosphate shunt in the rat. Further, the rate of oxidation appeared to be correlated with the magnitude of the bacteremia, which is an indication of the severity of the infection. Therefore, since glucose oxidation is necessary for a number of metabolic processes of various cells (such as phagocytosis and RNA synthesis), the increased glucose production during pneumococcal sepsis in the rat or rhesus monkey may not represent functional wastage to remove the excess alanine produced in skeletal muscle but a necessary process in the host defense mechanism against infectious disease. 相似文献
37.
Greene CM Van Beneden CA Javadi M Skoff TH Beall B Facklam R Abercrombie DR Kramer SL Arnold KE 《American journal of infection control》2005,33(2):108-113
BACKGROUND: Invasive group A streptococcus (GAS) affects approximately 10,500 persons annually; 1 in 5 patients >/=65 years die. In August 2001, CDC investigated a cluster of GAS deaths in a Georgia long-term care facility (LTCF). METHODS: We screened LTCF residents and staff for GAS carriage and conducted a retrospective cohort study among residents. We defined a case as GAS isolation associated with clinical infection. RESULTS: Eight cases were identified (median age: 79 years); 6 (75%) patients died. Carriage was similar in residents (10%) and staff (9%). All isolates among residents and 63% among staff were type emm 77. Risk factors for GAS disease or carriage among residents were receiving skin treatment (relative risk [RR] = 4.0, 95% confidence interval [CI] = 1.9-11.0) and having an infected or colonized roommate (RR = 2.0, 95% CI = 1.10-5.0). No wound care nurse carried GAS. Interventions included education about standardized infection control guidelines and appropriate hand hygiene; carriers were treated with antibiotics. No subsequent GAS cases were identified in the following year. CONCLUSIONS: Transmission of GAS in this outbreak likely occurred during wound care and ended with improved hand hygiene. This investigation highlights additional research and policy needs for control of severe GAS infections among the high-risk LTCF population. 相似文献
38.
Purified populations of natural killer (NK) cells were obtained from mice with severe combined immune deficiency (SCID). SCID spleen cells were cultured and activated with recombinant human interleukin-2 (rhIL- 2) in vitro. The activated NK cells were then transferred with syngeneic BALB/c bone marrow cells (BMC) and rhIL-2 into lethally irradiated syngeneic recipients to determine their effect on long-term hematopoietic reconstitution. On analysis, the transfer of rhIL-2- activated NK cells along with BMC resulted in significant increases in splenic and BM hematopoietic progenitor cells when compared with those for mice not receiving NK cells. Histologic and flow cytometric analysis showed a marked increase in granulocytic and megakaryocytic lineage cells present in the spleens of the mice receiving activated NK cells. Analysis of the peripheral blood indicated that the transfer of activated NK cells with BMC also significantly improved platelet and total white blood cell counts, with increases in segmented neutrophils. Erythroid recovery was not affected. Finally, lethally irradiated mice receiving activated NK cells and rhIL-2 along with limiting numbers of syngeneic BMC showed a marked increase in survival rate. These results show that the use of populations enriched for activated NK cells after syngeneic BM transplantation (BMT) has a profound enhancing effect on engraftment primarily affecting megakaryocytic and granulocytic cell reconstitution. Therefore, the transfer of activated NK cells and rhIL- 2 may be of clinical use to promote hematopoietic reconstitution after BMT. 相似文献
39.
Ng VL; Hurt MH; Fein CL; Khayam-Bashi F; Marsh J; Nunes WM; McPhaul LW; Feigal E; Nelson P; Herndier BG 《Blood》1994,83(4):1067-1078
Two B-cell lines, 2F7 and 10C9, were established by single cell cloning from biopsies obtained from two acquired immune deficiency syndrome patients with Burkitt's lymphoma. Representation of the original tumors was verified by demonstration of (1) identical biallelic rearrangement of Ig genes for 2F7 and (2) shared idiotype for 10C9. Both cell lines displayed cell-surface Ig and secreted Ig (IgM lambda for 2F7, IgM kappa for 10C9). IgMs from both cell lines immunoprecipitated actin; in addition, 2F7 IgM lambda immunoprecipitated recombinant human immunodeficiency virus type 1 (HIV-1) gp 160. 2F7 IgM lambda did not react with other autoantigens (double-stranded and single-stranded DNA, actin, bovine serum albumin, IgG), whereas 10C9 IgM kappa reacted with human IgG. The 2F7 IgM heavy-chain variable region (VH) showed a 95% nucleotide homology with a previously sequenced VHIII germline gene, hv3019b9, whereas the 10C9 IgM VH showed a 95% homology with a previously sequenced VHIV germline gene, VH4.21. Use of minimally modified VH genes and demonstration of reactivity with chronically present antigens (ie, actin, HIV-1 gp 160, or human IgG) suggests that B cells in HIV-1-infected individuals proliferating in response to chronic antigenic stimulation may be at increased risk for lymphomagenesis. 相似文献
40.