全文获取类型
收费全文 | 14795篇 |
免费 | 1259篇 |
国内免费 | 443篇 |
学科分类
医药卫生 | 16497篇 |
出版年
2024年 | 44篇 |
2023年 | 207篇 |
2022年 | 398篇 |
2021年 | 612篇 |
2020年 | 538篇 |
2019年 | 496篇 |
2018年 | 498篇 |
2017年 | 502篇 |
2016年 | 499篇 |
2015年 | 504篇 |
2014年 | 915篇 |
2013年 | 1062篇 |
2012年 | 813篇 |
2011年 | 910篇 |
2010年 | 660篇 |
2009年 | 647篇 |
2008年 | 629篇 |
2007年 | 593篇 |
2006年 | 551篇 |
2005年 | 474篇 |
2004年 | 409篇 |
2003年 | 423篇 |
2002年 | 347篇 |
2001年 | 281篇 |
2000年 | 225篇 |
1999年 | 243篇 |
1998年 | 225篇 |
1997年 | 222篇 |
1996年 | 194篇 |
1995年 | 179篇 |
1994年 | 174篇 |
1993年 | 151篇 |
1992年 | 151篇 |
1991年 | 132篇 |
1990年 | 132篇 |
1989年 | 135篇 |
1988年 | 125篇 |
1987年 | 99篇 |
1986年 | 105篇 |
1985年 | 166篇 |
1984年 | 133篇 |
1983年 | 94篇 |
1982年 | 93篇 |
1981年 | 101篇 |
1980年 | 90篇 |
1979年 | 71篇 |
1978年 | 50篇 |
1977年 | 52篇 |
1976年 | 43篇 |
1975年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
BACKGROUND: The distribution of house dust mite allergen (Der p1) in living rooms with smooth floor coverings, as measured in the middle compared with the border of the floor was investigated. It was hypothesized that activity causes displacement of Der p1, from the middle towards the border. METHODS: Dust samples from the middle and border of 50 floors with smooth coverings were collected and analysed on Der p1 content in a standardized way. RESULTS: The Der p1 exposure expressed as per unit area (ng/m2) showed that border samples contained significantly more Der p1 compared with middle samples (median: 2.57 vs 0.27, respectively, P = 0.023). Presence of pets and presence of more than two inhabitants increased the difference. When expressed as per unit weight of dust (ng/g), significant differences were only detected when comparing Der p1 content of samples collected in households with three or more inhabitants [median: 2 (border) vs 53 (middle), respectively; P = 0.035]. CONCLUSIONS: The Der p1 is unequally distributed on living room floors with smooth coverings, most likely because of displacement of dust from the middle towards the border due to activity. Expression as ng/g of dust and ng/m2 could not obviously be interchangeable. 相似文献
103.
Dong Qiu Terence Cosgrove Andrew M. Howe 《Macromolecular chemistry and physics.》2005,206(22):2233-2238
Summary: The surfactant‐free synthesis of latex polymers of styrene and sodium styrenesulfonate (NaSS) was investigated. The development of size and size distribution of the particles was studied by photo‐correlation spectroscopy (PCS) and transmission electronic microscopy (TEM). The effects of NaSS concentration and the order of addition of reactants were examined in detail. The results showed that the particle size decreases with an increase in the styrene sulfonate concentration. The polydispersity index can be reduced by mixing NaSS with styrene homogeneously before adding initiator, but this leads to a slightly larger mean particle size.
104.
The intracellular distribution of acetylcholinesterase (AChE) was determined in adult rat anterior gracilis muscles. Echothiophate iodide (ECHO), a water-soluble cholinesterase inhibitor, was applied to muscles in situ to eliminate extracellular and/or extracellularly oriented enzyme. Control and ECHO-treated muscles were either cut into 1-mm segments and assayed for AChE activity or cytochemically stained for AChE. Subsequent analysis by light and electron microscopy showed that the AChE stain inside myofibers was highly localized and clearly visible only in the zone immediately underlying the point of nerve-muscle contact. Biochemical assay of muscle segments showed intracellular AChE to be most highly concentrated in regions containing large numbers of endplates (approximately twice the activity of endplate-free areas). Since such "endplate-rich" segments are in fact mostly extra-synaptic tissue, we conclude that intracellular AChE of adult rat gracilis myofibers, although present along the length of the cell, is more than two times as concentrated in sub-synaptic areas as compared to extra-synaptic areas. This result must be carefully considered when attempting to identify "endplate-specific" AChE activity of mammalian muscle, and further points to the importance of neural influences on AChE metabolism/regulation. 相似文献
105.
Amadou Kane Edmond Ekué Creppy Angelika Roth Robert Röschenthaler Guy Dirheimer 《Archives of toxicology》1986,58(4):219-224
The distribution of a single low dose of [3H]ochratoxin A (OTA) in different tissues of male Wistar rats, after administration by intubation, was investigated after 5 h, 24 h and 48 h. This dose corresponds to concentrations encountered in naturally contaminated feed (4 ppm). The distribution of [3H]-label varied with the time elapsed after administration; at 5 h the highest specific label was found in the stomach contents and in decreasing order in: intestinal contents, lung, liver, kidney, heart, fat, intestine, testes, and the lowest in muscles, spleen and brain. With exception of brain, fat, stomach and lung, all tissues showed maximum levels at 24 h, after which time the label decreased steadily, whereas in fat it increased.After a 12-week feeding experiment, with doses of 288.8 g/kg corresponding to an intake of 4 ppm in feed each 48 h, the DNA in liver and kidneys was investigated for damage. By the alkaline elution method combined with micro-spectrofluorimetric determinations of DNA, evidence for DNA single-strand breaks was obtained. These findings support reports on the carcinogenic action of OTA. 相似文献
106.
Chung Y. Lui Myung G. Lee Win L. Chiou 《Journal of pharmacokinetics and pharmacodynamics》1984,12(6):597-610
The effects of plasma concentration and pH on the steady-state volume of distribution, Vss,of methotrexate (MTX) were studied in five conditioned male beagle-mongrel dogs. Steady-state plasma MTX concentrations of approximately 1, 20, and 100g/ml were targeted for by i.v. bolus doses followed by i.v. infusions. An isotonic solution of sodium bicarbonate or ammonium chloride was simultaneously infused for the purpose of inducing plasma pH change, while the infusion of an isotonic solution of sodium chloride served as a control. Plasma and urine concentrations of MTX were quantitated by a sensitive high-performance liquid chromatographic method, and the Vss
of MTX was estimated by a recently reported physiologically based method of Chiou and Lam. Statistically significant (p<0.05) concentration and plasma pHdependent Vss
of MTX were observed. Concentration dependence of Vss
was noted in sodium chloride and ammonium chloride infused dogs, but not in bicarbonate treated dogs. There was an average 50.0 and 44.8% increase in Vss
at 1 g/ ml relative to the two higher concentrations (20 and 100 g/ ml) for dogs treated with ammonium and sodium chloride, respectively. However, Vss
of MTX at the targeted concentrations of 20 and 100 g/ml was relatively constant. Plasma pHdependence of Vss
was observed only at the plasma concentration of 1 g/ml, and on the average, ammonium chloride and sodium chloride treatments resulted in 50.0 and 31.3% higher Vss,respectively, when compared with the bicarbonate treatment. These phenomena appear to be adequately explained by the reported tissue uptake kinetics of MTX.This research was supported in part by a grant from the National Cancer Institute, CA-29754.Abstracted from a dissertation submitted in 1984 by Chung Y. Lui to the Graduate College, University of Illinois at Chicago, in partial fulfillment of Doctor of Philosophy Degree requirements. 相似文献
107.
Chunmao Zhang Zhendong Guo Zongzheng Zhao Tiecheng Wang Liang Li Faming Miao Cheng Zhang Yuanguo Li Yuwei Gao 《Emerging infectious diseases》2021,27(7):1979
We analyzed size of severe acute respiratory coronavirus 2 (SARS-CoV-2) aerosol particles shed by experimentally infected cynomolgus monkeys. Most exhaled particles were small, and virus was mainly released early during infection. By postinfection day 6, no virus was detected in breath, but air in the isolator contained large quantities of aerosolized virus. 相似文献
108.
109.
目的:探讨手术绝经对身体脂肪分布的影响。方法:手术绝经者32例,进行术前及术后6个月的自身比较。用双能X线吸收仪(DEXA)测定体脂肪量、躯干脂肪量及下肢脂肪量,并计算体脂肪率、躯干脂肪量/下肢脂肪量比(T/L)、上半身型的百分比。结果:手术绝经者术后6个月下肢脂肪量明显低于手术前(P<0.05),T/L明显高于手术前(P<0.01),手术前后的上半身型各占19.4%和36.6%。结论:手术绝经也可能会使身体脂肪分布向上半身型移行,且最初可能是下肢脂肪量的减少。上半身型脂肪分布会引起一系列代谢合并症,应引起高度重视。 相似文献
110.
肝毒性中药及其与药性和有效成分的关系——对55种中药肝毒性文献资料的分析报告 总被引:13,自引:0,他引:13
目的 :研究有关文献资料中中药肝毒性的报告及其与四气、五味、归经、有效成分之间的关系。方法 :应用文献研究方法 ,对 55种具有肝毒性的中药进行统计归类分析研究。结果 :中药四气、五味、归经及其有效成分与肝毒性有一定相关性。肝毒性主要集中在寒、热类 ,苦、辛类 ,归肝、脾、肾经类和有效成分中碱、甙类药物方面。结论 :中药药性理论及有效成分均与肝毒性有一定的关系 ,应用归类分析的方法对文献资料进行分析研究是中药毒性研究中确实可行的方法。 相似文献