全文获取类型
收费全文 | 18532篇 |
免费 | 1314篇 |
国内免费 | 566篇 |
专业分类
耳鼻咽喉 | 158篇 |
儿科学 | 373篇 |
妇产科学 | 342篇 |
基础医学 | 2971篇 |
口腔科学 | 276篇 |
临床医学 | 1588篇 |
内科学 | 2816篇 |
皮肤病学 | 425篇 |
神经病学 | 1153篇 |
特种医学 | 1147篇 |
外国民族医学 | 6篇 |
外科学 | 2391篇 |
综合类 | 2342篇 |
现状与发展 | 1篇 |
预防医学 | 900篇 |
眼科学 | 126篇 |
药学 | 1629篇 |
中国医学 | 442篇 |
肿瘤学 | 1326篇 |
出版年
2024年 | 14篇 |
2023年 | 167篇 |
2022年 | 333篇 |
2021年 | 497篇 |
2020年 | 509篇 |
2019年 | 446篇 |
2018年 | 400篇 |
2017年 | 486篇 |
2016年 | 606篇 |
2015年 | 671篇 |
2014年 | 1181篇 |
2013年 | 1171篇 |
2012年 | 1137篇 |
2011年 | 1382篇 |
2010年 | 1181篇 |
2009年 | 1170篇 |
2008年 | 1135篇 |
2007年 | 1140篇 |
2006年 | 1045篇 |
2005年 | 856篇 |
2004年 | 822篇 |
2003年 | 600篇 |
2002年 | 417篇 |
2001年 | 318篇 |
2000年 | 319篇 |
1999年 | 228篇 |
1998年 | 176篇 |
1997年 | 254篇 |
1996年 | 326篇 |
1995年 | 279篇 |
1994年 | 236篇 |
1993年 | 201篇 |
1992年 | 108篇 |
1991年 | 99篇 |
1990年 | 64篇 |
1989年 | 57篇 |
1988年 | 44篇 |
1987年 | 36篇 |
1986年 | 32篇 |
1985年 | 39篇 |
1984年 | 42篇 |
1983年 | 41篇 |
1982年 | 35篇 |
1981年 | 23篇 |
1980年 | 18篇 |
1979年 | 23篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1975年 | 5篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Dr. David M. Euhus MD Lucille Kimura PhD Bruce Arnold MD 《Annals of surgical oncology》1997,4(5):432-439
Background: Mice immunized with murine mammary carcinoma cells genetically engineered to secrete interleukin-2 (IL-2) are rendered resistant
to subsequent challenge with unmodified tumor cells, and in the case of mice bearing established tumors, the rate of development
of pulmonary metastases is reduced. Despite these encouraging animal results, little is known about the induction of antitumor
immunity by IL-2 gene transfer in human breast cancer.
Methods: Adenovirally mediated IL-2 gene transfer was performed in 12 tumor fragment cultures established from seven primary breast
cancers. Autologous tumor infiltrating lymphocytes (TILs) or peripheral blood mononuclear cells (PBMCs) were cocultured with
transduced tumor fragments, and changes in phenotype and cytotoxicity were measured.
Results: IL-2 was never detectable in the untransduced cultures, but it peaked at 5.0—1,324.8 ng/ml in the transduced cultures. Lymphocyte
counts declined in all untransduced cultures, but they increased two- to sevenfold in four transduced cultures. CD4:CD8 ratios
decreased from a mean of 2.11 at baseline to 1.27 after stimulation in coculture (p=0.03). Expansion of lymphocytes expressing
the natural killer cell phenotype (CD3−CD56+) occurred in only one culture, but the CD3+CD56+ population increased in four of six cultures. Lymphocytes from four of 10 cocultures generated significant cytotoxicity against
allogeneic breast cancer cells. Induction of cytotoxicity correlated with expansion of the CD3+CD56+ phenotype (R2=0.805, p=0.02).
Conclusions: IL-2 gene expression by human breast cancer causes expansion of CD3+CD56+ cytotoxic lymphocytes. This phenotype is consistent with that of a non-major histocompatibility complex (MHC)-restricted
cytokine induced killer cell population previously described.
Opinions, interpretations, conclusions and recommendations are those of the author and are not necessarily endorsed by the
U.S. Army.
Presented at the 49th Annual Cancer Symposium of The Society of Surgical Oncology, Atlanta, Georgia, March 21–24, 1996. 相似文献
52.
白细胞介素—2新的功能位点及其中枢镇痛作用 总被引:2,自引:0,他引:2
白细胞介素-2(IL-2)不仅是重要的免疫调节因子,而且还具有重要的中枢调节作用。本实验以钾离子透入引起大鼠甩尾反应为指标,发现侧脑室注射IL—2能显著提高动物痛阈,并能被纳洛酮所阻断,表示IL-2的中枢镇痛作用可能与阿片受体有关。利用基因定位突变技术获得的无免疫活性IL-2实查体仍具有中枢镇痛作用,表明IL—2分子上发挥镇痛和免疫调节作用的功能位点是相互独立的。纳洛酮能够阻断IL—2的中枢镇痛作用,而不能影响IL—2增殖CTLL-2细胞的作用,提示IL-2发挥镇痛和免疫调节作用可能通过不同的受体途径。IL-2分子中第45位Tyr残基突变为Val后,虽仍保留了免疫活性,但丧失了镇痛功能,表示45位Tyr残基是IL—2发挥中枢镇痛功能的关键残基之一。我们推测IL—2的镇痛功能位点可能在IL—2分子中第45位Tyr残基附近区域。 相似文献
53.
S. Leskinen-Kallio 《Clinical physiology and functional imaging》1994,14(3):329-335
Summary. The particular advantages of positron emission tomography (PET) technique are that it has higher sensitivity, higher resolution, and a higher quality of image than that found in conventional nuclear medicine. The possibility of quantification and the wide range of useful tracers have raised expectations of this new method. To date, most of the human PET cancer studies have been performed with [18F]fluorodeoxyglucose (FDG) or [11CJmethionine. These are good imaging agents for tumours. However, more specific radiopharmaceuticals are required if other features of tumour metabolism are to be observed, f11Thymidine may prove to be a good tracer for quantitative measurements of tumour proliferation and [18F]misonidazole has been suggested for imaging of hypoxia. 相似文献
54.
Molecular identification of a small supernumerary marker chromosome by in situ hybridization: diagnosis of an isochromosome 18p with probe L1.84 总被引:1,自引:0,他引:1
A dysmorphic child was found by cytogenetic analysis to have an extra small marker chromosome. The marker chromosome was shown to possess a chromosome 18 centromere by in situ hybridization, and probably represents an isochromosome 18p. Centromere specific probes should be of value in identifying extra small marker chromosomes, and thereby provide better understanding of the clinical significance of these. 相似文献
55.
Gérald Vanzetto Marc Janier Daniel Fagret Luc Cinotti Xavier André-Fouet Michel Comet Jacques Machecourt 《European journal of nuclear medicine and molecular imaging》1997,24(2):170-178
The best test presently available to ascertain residual viability within an infarct-related area involves the use of fluorine-18
fluorodeoxyglucose (FDG) to detect the persistence of some cellular metabolism. Rest reinjection of thallium-201 is a less
accurate alternative but is easy to perform. Iodinated fatty acids, which are used with standard gamma cameras, are proposed
as markers of cellular metabolism. This study was performed to assess the value of 16-iodo-3-methyl-hexadecanoic acid (MIHA)
as a marker of the residual cellular metabolism by comparison with FDG in patients with a recent myocardial infarction, and
to evaluate its contribution compared with the201Tl stress-redistribution-reinjection technique. Stress-redistribution-reinjection201T1 imaging, rest MIHA imaging and glucoseloaded FDG imaging were performed in 22 patients with recent myocardial infarction.
Out of the 628 myocardial segments obtained from the left ventricular analysis, 400 were hypoperfused (relative uptake <0.75
of maximum uptake on stress201T1 imaging), 177 of which were severely hypoperfused (relative uptake <0.50). Receiver operating characteristic (ROC) curves
for predicting metabolic myocardial viability with FDG were derived from the results in respect of (a)201T1 activity during exercise, redistribution and reinjection and (b) MIHA up-take, using the two FDG thresholds most commonly
considered to define metabolic viability (0.50 and 0.60). Analysis of the 400 hypoperfused segments demonstrated that201T1 reinjection was the most accurate test in predicting the presence of myocardial viability (area under the ROI curves=0.85
and 0.86 at the 0.50 and 0.60 FDG thresholds, respectively;P<0.05 vs other tests). The global predictive values of MIHA and201T1 reinjection were, respectively, 0.87 and 0.89 at the 0.50 FDG threshold (NS), and 0.82 and 0.87 at the 0.60 FDG threshold
(NS). When only the 177 severely hypoperfused segments were considered,201T1 reinjection remained the most accurate test (accuracy 0.84 at the 0.50 FDG threshold and 0.82 at the 0.60 FDG threshold),
while the accuracy of MIHA decreased significantly (0.78 at the 0.50 FDG threshold and 0.73 at the 0.60 FDG threshold,P<0.05 vs201T1 reinjection). In all circumstances, MIHA was less specific than201T1 reinjection for the detection of metabolic viability. In conclusion, in patients with recent myocardial infarction, MIHA
accurately detects the persistence of metabolic viability, but is not superior to201T1. 相似文献
56.
Myocardial metabolic imaging by means of fluorine-18 deoxyglucose/technetium-99m sestamibi dual-isotope single-photon emission tomography 总被引:2,自引:1,他引:1
Hans-Peter Stoll Nicola Hellwig Christof Alexander Cem Özbek Hermann Schieffer Erich Oberhausen 《European journal of nuclear medicine and molecular imaging》1994,21(10):1085-1093
The detection of preserved glucose uptake in hypoperfused dysfunctional myocardium by fluorine-18 deoxyglucose (FDG) positron emission tomography (PET) represents the method of choice in myocardial viability diagnostics. As the technique is not available for the majority of patients due to cost and the limited capacity of the PET centres, it was the aim of the present work to develop and test FDG single-photon emission tomography (SPET) with the means of conventional nuclear medicine. The perfusion marker sestamibi (MIBI) was used together with the metabolic tracer FDG in dual-isotope acquisition. A conventional SPET camera was equipped with a 511-keV collimator and designed to operate with simultaneous four-channel acquisition. In this way, the scatter of 18F into the technetium-99m energy window could be taken into account by a novel method of scatter correction. Thirty patients with regional wall motion abnormalities at rest were investigated. The results of visual wall motion analysis by contrast cine-ventriculography in nine segments/heart were compared with the results of quantitative scintigraphy. The scintigraphic patterns of MIBI and FDG tracer accumulation were defined as normal, matched defects and perfusion-metabolism mismatches. Spatial resolution of the system was satisfactory, with a full width at half maximum (FWHM) of 15.2 mm for 18F and 14.0 mm for 99mTe, as measured by planar imaging in air at 5 cm distance from the collimator. Image quality allowed interpretation in all 30 patients. 88% of segments without relevant wall motion abnormalities presented normal scintigraphic results. Seventy-five akinetic segments showed mismatches in 27%, matched defects in 44% and normal perfusion in 29%. We conclude that FDG-MIBI dual-isotope SPET is technically feasible with the means of conventional nuclear medicine. Thus, the method is potentially available for widespread application in patient care and may represent an alternative to the 201T1 reinjection technique. 相似文献
57.
30例新鲜胃癌标本,采用多聚酶链反应技术检测人类乳头瘤病毒16、18感染、并采用多聚酶链反应-单链构象多态性技术对p53基因突变进行检测。结果:HPV15阳性率为40.0%,未发现HPV18感染:P53基因突变率为50.0%,HPV16感染和P53基因突变同时存在者为16.7%。 相似文献
58.
To evaluate the effect of interleukin-8 (IL8) on glomerular basement membrane (GBM) sulfated compounds and albuminuria, we
infused IL8 in 1% bovine serum albumin (BSA) for 5 days into the left renal artery of Holtzman male rats at the rate of 10
μl/h using an osmotic pump. Control rats received 1% BSA. A significant increase in urinary albumin/creatinine ratio was seen
on the last day of IL8 infusion (0.38±0.11, mean ± SEM) when compared with albumin/creatinine ratio prior to infusion (0.19±0.04,
P = 0.04). No significant differences in urinary albumin excretion prior to and after infusion of 1% BSA were observed. On
the last day of infusion, rats were injected with 35sulfate (1.0 mCi/200 g body weight) intraperitoneally and killed after 8 h. Glomeruli were isolated and GBM obtained. After
5 days of IL8 administration, there was a significant increase in 35sulfate uptake by GBM of the infused kidney (76±10 cpm/dry glomerular weight, mean ± SEM) compared with the uptake seen in
the contralateral kidney (53±9, P = 0.05). The in vivo infusion of IL8 increased the 35sulfate uptake by GBM and augmented the urinary albumin/creatinine ratio, suggesting that IL8 may induce albuminuria by altering
the metabolism of the GBM sulfated compounds. This hypothesis needs to be confirmed by studies on glomerular charge selectivity
and GBM anionic sites during the course of the infusion. Moreover, the persistence of the effect needs to be evaluated by
prolonging the infusion for more than 5 days.
Received June 3, 1996; received in revised form and accepted October 18, 1996 相似文献
59.
That maternal inflammation adversely affects fetal brain development is well established. Less well understood are the mechanisms that account for neurodevelopmental disorders arising from maternal inflammation. This review seeks to begin an examination of possible sites and mechanisms of action whereby inflammatory cytokines - produced by the mother or by the fetal brain - could impact the developing fetus. We focus first on the placenta where cytokines maintain the immunological environment that prevents maternal rejection of the fetus. Following a brief examination of placental transfer of maternal cytokines, the focus turns on embryonic microglia, early and ubiquitous residents of the developing brain. Finally, a more intense examination of interleukin-6 (IL-6) and bone morphogenetic proteins (BMPs) provides examples of glial- or maternal-derived cytokines that are known to have profound effects on developing systems and that could, if dysregulated, have undesirable consequences for brain development. 相似文献
60.
4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane (Kryptofix® 2.2.2) is used in the routine preparation of [18F]-labeled tracers employed in positron emission tomography (PET) imaging. Confirming the absence of Kryptofix® in radiopharmaceuticals is a quality control criterion required before they can be released for human use. Analysis of Kryptofix® levels using the iodoplatinate spot-test can be complicated by false-positive results due to nitrogen containing tracers and/or false-negative results caused by added stabilizers. To overcome this issue, we have developed a universal TLC method for the rapid and reliable determination of Kryptofix® levels in the wide range of fluorine-18 radiopharmaceuticals we prepare, including complex multi-component formulations. 相似文献