全文获取类型
收费全文 | 4666篇 |
免费 | 470篇 |
专业分类
5136篇 |
出版年
2022年 | 34篇 |
2021年 | 55篇 |
2020年 | 44篇 |
2019年 | 55篇 |
2018年 | 56篇 |
2017年 | 80篇 |
2016年 | 88篇 |
2015年 | 149篇 |
2014年 | 190篇 |
2013年 | 203篇 |
2012年 | 276篇 |
2011年 | 257篇 |
2010年 | 181篇 |
2009年 | 169篇 |
2008年 | 229篇 |
2007年 | 205篇 |
2006年 | 190篇 |
2005年 | 204篇 |
2004年 | 212篇 |
2003年 | 202篇 |
2002年 | 166篇 |
2001年 | 180篇 |
2000年 | 149篇 |
1999年 | 145篇 |
1998年 | 82篇 |
1997年 | 81篇 |
1996年 | 61篇 |
1995年 | 45篇 |
1994年 | 65篇 |
1993年 | 45篇 |
1992年 | 86篇 |
1991年 | 73篇 |
1990年 | 73篇 |
1989年 | 71篇 |
1988年 | 57篇 |
1987年 | 41篇 |
1986年 | 40篇 |
1985年 | 67篇 |
1984年 | 43篇 |
1983年 | 35篇 |
1982年 | 40篇 |
1981年 | 26篇 |
1980年 | 25篇 |
1979年 | 42篇 |
1978年 | 23篇 |
1977年 | 23篇 |
1976年 | 24篇 |
1974年 | 29篇 |
1973年 | 24篇 |
1972年 | 22篇 |
排序方式: 共有5136条查询结果,搜索用时 15 毫秒
61.
Fluid balance in exercise dehydration and rehydration with different glucose-electrolyte drinks 总被引:3,自引:0,他引:3
B Nielsen G Sj?gaard J Ugelvig B Knudsen B Dohlmann 《European journal of applied physiology and occupational physiology》1986,55(3):318-325
After exercise dehydration (3% of body weight) the restoration of water and electrolyte balance was followed in 6 male subjects. During a 2 h rest period after exercise, a drink of one of four solutions was given as 9 X 300 ml portions at 15 min intervals: control (C-drink), high potassium (K-drink), high sodium (Na-drink) or high sugar (S-drink). An exercise test (submaximal and supramaximal work) was performed before dehydration and after rehydration. Dehydration reduced plasma volume by 16%, a process reversed on resting even before fluid ingestion began, due to release of water accumulated in the muscles during exercise. After 2 h rehydration, plasma volume was above the initial resting value with all 4 drinks. The final plasma volumes after the Na-drink (+14%) and C-drink (+9%) were significantly higher than after the K- and S-drinks. The Na-drink favoured filling of the extracellular compartment, whereas the K- and S-drinks favoured intracellular rehydration. In spite of the higher than normal plasma volume after rehydration, mean heart rate during the submaximal test was 10 bpm higher after rest and rehydration than in the initial test, and was not different between the drinks. The amount of work which could be performed in the supramaximal test (105% VO2max) was 20% less after exercise dehydration and subsequent rest and rehydration than before. This reduction was similar for all drinks, and may be due to a decreased muscle glycogen content (70% of initial) at the time of the second test. 相似文献
62.
63.
E Hommel H H Parving E Mathiesen B Edsberg M Damkjaer Nielsen J Giese 《BMJ (Clinical research ed.)》1986,293(6545):467-470
The influence of angiotensin II on kidney function in diabetic nephropathy was assessed by studying the effect of 12 weeks'' monotherapy with captopril (25-50 mg twice a day) in 16 hypertensive insulin dependent diabetic patients with persistent albuminuria. In an initial one week randomised single blind trial of captopril versus placebo, captopril (for nine patients) reduced arterial blood pressure from 148/94 (SD11/6) to 135/88 (8/7) mm Hg (p less than 0.05) and albuminuria from 1549 (range 352-2238) to 1170 (297-2198) micrograms/min (p less than 0.05), while glomerular filtration rate remained stable. No significant changes occurred in seven patients treated with placebo. During the 12 weeks of captopril treatment arterial blood pressure in all patients fell from 147/94 (11/6) to 135/86 (13/7) mm Hg (p less than 0.01), albuminuria fell from 1589 (range 168-2588) to 1075 (35-2647) micrograms/min (p less than 0.01), and glomerular filtration rate fell from 99 (SD19) to 93 (25) ml/min/1.73 m2 (p less than 0.01). The renin-angiotensin system showed suppressed plasma concentrations of angiotensin II and increased concentrations of angiotensin I and renin. The study showed that glomerular filtration rate is not dependent on angiotensin II, that captopril reduces albuminuria, probably by lowering glomerular hypertension, and that captopril represents a valuable new drug for treating hypertension in diabetics dependent on insulin with nephropathy. 相似文献
64.
Differentiated inhibition of DNA, RNA and protein synthesis in L1210 cells by 8-methoxypsoralen 总被引:1,自引:0,他引:1
The synthesis of DNA, RNA and protein was measured in L1210 cells following treatment with 8-methoxypsoralen in combination with long wavelength ultraviolet irradiation. The results show that the DNA synthesis is strongly inhibited (approximately 95%) at 200 ng/ml reaching a minimum within 2 hours while RNA synthesis is only weakly affected at this concentration (approximately 40% inhibition). At 2 micrograms/ml the RNA synthesis is inhibited approximately 90%. Even at this concentration only a moderate effect is seen on the protein synthesis. These results strongly indicate that the phototoxic action of 8-methoxypsoralen is primarily due to inhibition of DNA synthesis. 相似文献
65.
Masato Tawata Ryoji Kobayashi Myles L. Mace Thor B. Nielsen James B. Field 《Biochemical and biophysical research communications》1983,111(2):415-423
An actin polymerization stimulator was purified from bovine thyroid plasma membranes by DNase I affinity column chromatography. Although the molecular weight of the protein was about 42,000 (42K) by sodium dodecyl sulfate polyacrylamide gel electrophoresis, it did not comigrate with actin. In the presence of 30 mM KCl, the 42K protein facilitated formation of actin filaments when analyzed by a centrifugation method, accelerated the initial phase of actin polymerization as measured in an Ostwald viscometer and increased the length of filaments as shown by electron microscopy. The 42K protein also accelerated the initial phase of actin polymerization in the presence of 100 mM KCl and 2 mM MgCl2 but did not affect the final viscosity. The effect of the 42K protein was diminished by 5 uM cytochalasin B or 1 uM cytochalasin D. This 42K protein may anchor actin filaments onto the thyroid plasma membrane. 相似文献
66.
R Kubica B Nielsen A Bonnesen I B Rasmussen J Stok?osa B Wilk 《Acta physiologica Polonica》1983,34(5-6):569-579
Plasma volume was decreased by prolonged bicycle exercise, by passive heating in warm water, by sauna dehydration, and by diuretically induced dehydration in eleven well trained subjects. Blood samples from an arm vein were taken before and after this pre-treatment, as well as after a subsequent standard exercise test (SET) on a bicycle ergometer (50%, 70% and 105% of max VO2; the SET with no pre-treatment was used as a control condition. The changes in plasma concentration of Na+, K+ and Cl- were not proportional to the calculated plasma volume changes. The Na+ and Cl- concentrations always increased in the plasma, while plasma potassium concentration was increased after prolonged exercise, but decreased after the other types of dehydrations. The standard exercise test produced a pronounced fall in total calculated plasma potassium and in K+ concentration measured 3-5 min after exercise in all types of experiments. In the standard exercise test the calculated water loss from the plasma volume was relatively large. It amounted to about 2/3 of the total water loss in the standard exercise test and was independent of the pre-treatments. 相似文献
67.
A series of novel compounds in which a 9-acridinyl nucleus is linked to a psoralen nucleus in the 5- or 8-position via polyamines was prepared and examined. Their reversible binding to DNA and their irreversible binding to DNA and DNA cross-linking upon irradiation with UV-A light were examined. It was found that they were all less efficiently photoreactive than 8-methoxypsoralen (8-MOP), both in cross-linking and photobinding to DNA, whereas the ratio between their photobinding and cross-linking was 40-400 times that of 8-MOP. Compounds in which the linker was attached to the 5-position in psoralen showed smaller cross-linking and photobinding efficiencies and larger ratios between photobinding and cross-linking than those of psoralens attached in the 8-position. This strongly indicates that the 9-substituents of the acridines are oriented toward the minor groove. Flow linear dichroism studies showed that the compounds were DNA intercalating with the acridine moiety, whereas the psoralen moiety in no case was clearly intercalating. This conclusion was further supported by viscometry which also strongly indicated monointercalation. 相似文献
68.
Delayed type hypersensitivity against antigens of Fasciola hepatica has been repeatedly documented in infected hosts. Evidence has been presented to suggest that the delayed reactivity may develop earlier in the regional lymph nodes of the parasitized organ than in other lymph nodes of the body (Soulsby 1971). 相似文献
69.
70.