全文获取类型
收费全文 | 2248篇 |
免费 | 117篇 |
国内免费 | 75篇 |
专业分类
耳鼻咽喉 | 10篇 |
儿科学 | 173篇 |
妇产科学 | 29篇 |
基础医学 | 257篇 |
口腔科学 | 58篇 |
临床医学 | 257篇 |
内科学 | 518篇 |
皮肤病学 | 75篇 |
神经病学 | 158篇 |
特种医学 | 428篇 |
外国民族医学 | 1篇 |
外科学 | 103篇 |
综合类 | 44篇 |
预防医学 | 88篇 |
眼科学 | 25篇 |
药学 | 104篇 |
2篇 | |
肿瘤学 | 110篇 |
出版年
2021年 | 11篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 31篇 |
2017年 | 22篇 |
2016年 | 22篇 |
2015年 | 40篇 |
2014年 | 47篇 |
2013年 | 57篇 |
2012年 | 36篇 |
2011年 | 38篇 |
2010年 | 89篇 |
2009年 | 85篇 |
2008年 | 53篇 |
2007年 | 89篇 |
2006年 | 51篇 |
2005年 | 56篇 |
2004年 | 28篇 |
2003年 | 23篇 |
2002年 | 31篇 |
2001年 | 45篇 |
2000年 | 38篇 |
1999年 | 35篇 |
1998年 | 132篇 |
1997年 | 159篇 |
1996年 | 133篇 |
1995年 | 112篇 |
1994年 | 116篇 |
1993年 | 100篇 |
1992年 | 34篇 |
1991年 | 49篇 |
1990年 | 49篇 |
1989年 | 64篇 |
1988年 | 61篇 |
1987年 | 57篇 |
1986年 | 52篇 |
1985年 | 57篇 |
1984年 | 34篇 |
1983年 | 25篇 |
1982年 | 29篇 |
1981年 | 32篇 |
1980年 | 25篇 |
1978年 | 14篇 |
1977年 | 19篇 |
1976年 | 28篇 |
1975年 | 21篇 |
1974年 | 8篇 |
1972年 | 8篇 |
1971年 | 13篇 |
1968年 | 8篇 |
排序方式: 共有2440条查询结果,搜索用时 15 毫秒
131.
Matter D Grosshans E Muller J Furderer C Mathelin C Warter S Bellocq JP Maillot C 《Journal de radiologie》2002,83(5):599-609
132.
Hans JM van Grinsven Mary H Ward Nigel Benjamin Theo M de Kok 《Environmental health : a global access science source》2006,5(1):26-6
Several authors have suggested that it is safe to raise the health standard for nitrate in drinking water, and save money
on measures associated with nitrate pollution of drinking water resources. The major argument has been that the epidemiologic
evidence for acute and chronic health effects related to drinking water nitrate at concentrations near the health standard
is inconclusive. With respect to the chronic effects, the argument was motivated by the absence of evidence for adverse health
effects related to ingestion of nitrate from dietary sources. An interdisciplinary discussion of these arguments led to three
important observations. First, there have been only a few well-designed epidemiologic studies that evaluated ingestion of
nitrate in drinking water and risk of specific cancers or adverse reproductive outcomes among potentially susceptible subgroups
likely to have elevated endogenous nitrosation. Positive associations have been observed for some but not all health outcomes
evaluated. Second, the epidemiologic studies of cancer do not support an association between ingestion of dietary nitrate
(vegetables) and an increased risk of cancer, because intake of dietary nitrate is associated with intake of antioxidants
and other beneficial phytochemicals. Third, 2–3 % of the population in Western Europe and the US could be exposed to nitrate
levels in drinking water exceeding the WHO standard of 50 mg/l nitrate, particularly those living in rural areas. The health
losses due to this exposure cannot be estimated. Therefore, we conclude that it is not possible to weigh the costs and benefits
from changing the nitrate standard for drinking water and groundwater resources by considering the potential consequences
for human health and by considering the potential savings due to reduced costs for nitrate removal and prevention of nitrate
pollution. 相似文献
133.
随着禽流感病毒H5N1的不断蔓延,越来越有可能发生人类流感的大流行。如果现在发生流感的大流行,不仅还没有有效的疫苗,而且还可能造成抗病毒药物的缺乏。目前尚没有证据表明抗流感药物神经氨酸酶抑制剂(neuraminidaseinhibitor对)禽流感和流感大流行的病毒有效,给予神经氨酸酶抑制剂后,感染H5N1禽流感病毒的患者的死亡率仍然很高。而且流感病毒的耐药会进一步限制抗病毒药物的疗效。假如继发性细菌感染是流感常见且重要的致命性并发症,那么抗生素在人类流感大流行中将占有重要的一席地位。 相似文献
134.
135.
136.
Janjaap van der Net Patrick van der Torre Raoul HH Engelbert Vivian Engelen Femke van Zon Tim Takken Paul JM Helders 《Pediatric rheumatology online journal》2008,6(1):2
Objective
To describe the level of motor performance and functional skills in young children with JIA. 相似文献137.
Marijke JM Chin A Paw Amika S Singh Johannes Brug Willem van Mechelen 《The international journal of behavioral nutrition and physical activity》2008,5(1):41
Objectives
This paper aims to identify the mediating mechanisms of a school-based obesity prevention program (DOiT). 相似文献138.
Background
The Licensing Act 2003 (The Act) was implemented on the 24th November 2005 across England and Wales. The Act allowed more flexible and longer opening hours for licensed premises. We investigated the effect of The Act on alcohol related attendances to an inner city emergency department in Birmingham, UK. 相似文献139.
Although exposure of LLC-PK1 epithelial cell sheets to phorbol esters (TPA)
causes a near immediate and total decrease of transepithelial electrical
resistance (TER), continuation of exposure for 3 to 4 days results in a
tachyphylactic response as TER begins to return to control levels. Recovery
of TER is maximal by 5 to 6 days, but reaches only 70 to 80% of control
level. A reciprocal change in the transepithelial flux of D-mannitol
indicates that the TER decrease is indicative of an increase in tight
junction permeability. Exposure of cell sheets to TPA for several days also
results in the appearance of multilayered polyp- like foci (PLFs) across
the otherwise one cell layer thick cell sheets. The pattern of penetration
of the electron dense dye, ruthenium red, from the apical surface, across
the tight junction and into the lateral intercellular space indicates that
the tight junctions of the cell sheet become uniformly leaky after acute
exposure to TPA. However, when exposure is continued for several days, only
the junctions of cells in the PLFs manifest leakiness. The decrease in TER
following acute TPA exposure correlates with the translocation of protein
kinase C-alpha (PKC alpha) into a membrane-associated compartment. With
exposure of several days, only a trace of PKC alpha is visible by Western
immunoblot, and this is in the membrane-associated compartment.
Immunofluorescent microscopy indicates that the trace of PKC alpha seen in
the Western immunoblots is ascribable distinctly to cells of the PLFs.
Monolayer areas between PLFs show no discernible immunofluorescent signal.
The data therefore indicate that tight junction barrier function may be
restored in certain areas by the down regulation of PKC alpha from the
membrane-associated compartment. Failure to down regulate may result in the
paracellular leakiness and abnormal cell architecture of the PLFs. Possible
implications of this model for in vivo epithelial tumor promotion are
discussed.
相似文献
140.
Perkins SN; Hursting SD; Haines DC; James SJ; Miller BJ; Phang JM 《Carcinogenesis》1997,18(5):989-994
Transgenic mice with both alleles of the p53 tumor suppressor gene product
'knocked out' by gene targeting are susceptible to early development of
tumors, chiefly lymphomas and sarcomas. Compared with the control group,
administration of dehydroepiandrosterone (DHEA) at 0.3% of the diet to male
p53-deficient mice extended their lifespan by delaying death due to
neoplasms (from 105 to 166 days on study, P = 0.002), primarily by
suppressing lymphoblastic lymphoma (from 45 to 6% of neoplastic deaths, P =
0.010). Treatment with a synthetic DHEA analog,
16alpha-fluoro-5-androsten-17-one (compound 8354), at 0.15% of the diet
also increased lifespan, to 140 days for mice that developed tumors (P =
0.037). The effects of these steroids on lifespan and tumor development did
not appear to be strongly related to inhibition of food consumption and
weight gain, in that a group pair-fed with control diet to the reduced food
consumption of the DHEA-treated group developed and died of the same types
of neoplasms at the same rate as the controls fed ad libitum. The
chemopreventive effect of these steroids has been proposed to be due to
suppression of DNA synthesis by inhibition of glucose 6-phosphate
dehydrogenase, the rate-limiting enzyme of the pentose phosphate pathway.
Although DHEA and its analog are strong non- competitive inhibitors of this
enzyme in vitro, treatment with DHEA did not deplete cellular nucleotide
pools in the liver, as would have been predicted. The chemopreventive
effect of DHEA in this model may be due to steroid-induced thymic atrophy
and suppression of T cell lymphoma, permitting these mice to survive long
enough to develop tumors with longer latency.
相似文献