首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9631篇
  免费   392篇
  国内免费   175篇
耳鼻咽喉   71篇
儿科学   116篇
妇产科学   117篇
基础医学   1680篇
口腔科学   449篇
临床医学   415篇
内科学   1385篇
皮肤病学   50篇
神经病学   844篇
特种医学   173篇
外科学   1713篇
综合类   865篇
预防医学   470篇
眼科学   38篇
药学   1495篇
  1篇
中国医学   178篇
肿瘤学   138篇
  2023年   56篇
  2022年   95篇
  2021年   143篇
  2020年   135篇
  2019年   139篇
  2018年   163篇
  2017年   159篇
  2016年   173篇
  2015年   210篇
  2014年   401篇
  2013年   445篇
  2012年   363篇
  2011年   394篇
  2010年   298篇
  2009年   427篇
  2008年   456篇
  2007年   458篇
  2006年   433篇
  2005年   420篇
  2004年   298篇
  2003年   305篇
  2002年   258篇
  2001年   247篇
  2000年   252篇
  1999年   282篇
  1998年   239篇
  1997年   239篇
  1996年   201篇
  1995年   233篇
  1994年   244篇
  1993年   192篇
  1992年   183篇
  1991年   138篇
  1990年   148篇
  1989年   127篇
  1988年   107篇
  1987年   150篇
  1986年   113篇
  1985年   122篇
  1984年   95篇
  1983年   55篇
  1982年   77篇
  1981年   61篇
  1980年   60篇
  1979年   54篇
  1978年   54篇
  1977年   54篇
  1976年   45篇
  1975年   32篇
  1973年   36篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
71.
Summary A method is described for the growth of calcium oxalate dihydrate in normal urine. Soluble chlorophyllin, at a concentration of 20 g/ml inhibited the crystallisation and the growth kinetics of the dihydrate crystals. The inhibitory capacity of chlorophyllin was compared with previous results. Data obtained suggest that the food and drug colourant chlorophyllin might be useful in the treatment of calcium oxalate stone disease.  相似文献   
72.
Zusammenfassung Zusätzlich wurden physikalische und chemische Untersuchungen über den Einfluß von dynamischem Interferenzstrom (DIC) auf die Knochenheilung durchgeführt, nachdem bei 24 Schwarzkopfschafen eine Querosteotomie des Radius vorgenommen worden war. Nach instabiler Osteosynthese wurde die Osteotomiezone wiederholt mit DIC verschiedener mA—Stärken behandelt. (Methodische Einzelheiten sind in Teil I beschrieben). Die Behandlung mit dynamischem Interferenzstrom führte im behandelten Gewebe zu steigenden Temperaturen, die von den mA—Stärken abhängig waren. Weiterhin wurden Zusammenhänge zwischen DIC—mA—Intensität und dem Vorkommen von Hydroxyprolin, einer kollagenspezifischen Aminosäure, nachgewiesen, welches eine erhöhte Calcifizierungsaktivität zur Folge hatte. Messungen des Calcium— und Phosphorgehaltes im neugebildeten Knochengewebe wiesen bei den mit DIC behandelten Tieren vollständige Mineralisation zu einem viel früheren Zeitpunkt als bei den unbehandelten, nach gleichem Verfahren operierten Kontrolltieren auf. Ob DIC einen spezifischen Reiz auf die Knochenneubildung heilender Knochen ausübt, ist noch nicht vollständig geklärt.
Bone healing and Dynamic Interferential Current (DIC)
Summary In the course of supplementary physical and chemical investigations of the influence ofDynamicInterferential Current (DIC) on bone healing 24 black-head sheep were subjected to transversal osteotomy of the radius. After an instable osteosynthesis the site was exposed to repeated therapy with DIC of varying mA intensity. (Methodological details are described in part 1.) DIC therapy resulted in altering the temperatures in the treated tissue, dependent on the mA intensity. Further associations were verified between DIC intensity and the occurrence of hydroxyprolin, an amino acid specific collagen, which also reflected increased calcifying activity. Measurements of the calcium and phosphorus levels in the regenerated (newly forming) bone tissue documented full mineralization in the DIC-treated animals at a much earlier date than in the untreated controls that had undergone similar operations. Whether DIC specifically stimulates osteogenesis within healing bones is still unclear.
  相似文献   
73.
The ionophore A23187 produced a rapid transient increase in the rate of calcium uptake by isolated fetal rat bone cells. There was no effect on calcium efflux or total cellular calcium. The magnitude of the effect on influx was amplified when the cell were incubated at 4°C. Cellular metabolic functions and resorption of cultured fetal rat bones (release of45Ca from pre-labeled long bone) were affected by A23187 in a biphasic manner: cell cyclic AMP (cAMP) was increased by 0.1 and 0.3 g/ml of the ionophore, whereas 10 g/ml was either ineffective or lowered the cAMP levels. The high A23187 concentration abolished the stimulatory effects of parathyroid hormone and methylisobutylxanthine. Concentrations of 0.1 and 0.3 g/ml A23187 stimulated bone resorption. The effect was abolished by calcitonin. Ionophore concentrations above 1 g/ml produced less bone resorption. These higher concentrations antagonized the bone-resorbing effect of parathyroid hormone and 1,25-dihydroxyvitamin D3. A23187 at 5 and 10 g/ml decreased bone cell lactate and ATP. Thus at low concentrations, A23187 produced effects on bone similar to those of parathyroid hormone, suggesting that calcium is the primary initiator of PTH-induced bone resorption. At the higher concentrations A23187 may have a general inhibitory effect on cell metabolism.  相似文献   
74.
Summary The effects of ionophore X537A on the release of 3H-noradrenaline and its metabolites from the superfused guinea-pig left atrium were investigated. Concentrations of ionophore of 10 and 30 M greatly increased the release of tritium. Of the total increase in radioactivity elicited by X537A 44% was accounted for as noradrenaline and 50% was due to deaminated metabolites. The ionophore-evoked release of tritium was independent of the extracellular calcium ions and was not affected by agents which modify calcium movements such as verapamil, ryanodine, ruthenium red and tetracaine. X537A released 3H-noradrenaline from extragranular sites in MAO-inhibited atria from reserpine-treated animals and this release was also calcium independent. It is concluded that the ability of X537A to release noradrenaline from vesicular or cytoplasmic sites is not related to its ability to couple with and transport calcium ions through membranes. The ionophore might modify the ionic distribution outside and inside the neuronal membrane which would lead to leakage of the transmitter.  相似文献   
75.
钙离子拮抗剂治疗阿尔茨海默氏病的现状   总被引:4,自引:1,他引:4  
王羽  董志 《中国药业》2003,12(12):31-33
目的:介绍钙离子(Ca2 )拮抗剂治疗阿尔茨海默氏病(AD)的机制和研究进展。方法:查阅近年来国内外相关献。结果:应用Ca2 拮抗剂(如尼莫地平等)治疗AD,可促进受伤神经的再生和感觉运动功能的恢复,并有较好的临床疗效。结论:Ca2 自体平衡失调学说为AD发病机制中的重要组成,应用Ca2 拮抗剂治疗AD具有良好的前景。  相似文献   
76.
目的 探讨一氧化氮供体———硝普钠 (sodiumnitroprusside ,SNP)对豚鼠单离耳蜗外毛细胞钙电流的影响及作用机制。方法 利用急性分离的豚鼠耳蜗外毛细胞 ,在全细胞膜片钳电压钳记录技术下 ,通过分离离子电流成分的方法 ,记录豚鼠耳蜗外毛细胞全细胞钙电流。结果 SNP对内向钙电流有抑制作用 ,在钳制电位为 -60mV ,刺激电压为 + 10mV的条件下 ,10mmol/L的SNP能抑制 (61 12± 1 99) %的内向钙电流 ( x±s ,n =5)。从 5~ 8个细胞得到的量效关系曲线中 ,其半数作用浓度为 1 9mmol/L ,最大抑制浓度为 10 0mmol/L ,斜率为 0 98。作用的机制为SNP可选择性地阻断外毛细胞膜上的L 型钙通道 (n =6)。结论 SNP作为一氧化氮的一种供体 ,能影响豚鼠耳蜗外毛细胞的生理功能 ,是通过阻断外毛细胞L 型钙通道电流的内流来实现的  相似文献   
77.
OBJECTIVE: The aim of the study was the assessment of calcium-phosphorus-magnesium homeostasis in pregnant women after renal transplantation. METHODS: The study covered 64 pregnant women in the third trimester of gestation including: 33 women after renal transplantation (the study group) and 31 healthy pregnant women (the control group). Women from both groups were at the similar age: 30.8+/-4.7 vs. 31.3+/-5.0 years (NS) and at the same gestational age 34.8+/-2.4 vs. 35.3+/-2.6 weeks (NS). The mean body mass index (BMI) in the women from the study group before pregnancy was 21.49+/-2.81 vs. 22.1+/-3.02 in the control group (NS), BMI before delivery was 25.43+/-3.05 vs. 26.0+/-3.35 (NS), the percentage of the BMI increase during pregnancy was 18.7+/-7.68 vs. 17.65+/-7.13 (NS) and BMI increase during gestation was 3.93+/-1.56 vs. 3.90+/-1.54, respectively (NS). Arterial blood pressure at the time of blood samples collection for biochemical tests was 151.4+/-26.8/92.5+/-16.9 in women from the study group comparing to 115.0+/-6.0/68.0+/-7.0 mmHg (P<0.001) in the patients from the control group. The maximal blood pressure during pregnancy was 169.2+/-20.7/102.7+/-14.0 vs. 118.0+/-7.0/70.0+/-8.0 mmHg (P<0.001), respectively. We estimated serum levels of: total Ca, ionized Ca(2+), inorganic phosphorus (P(i)), Mg, total protein, albumin and blood morphology. Moreover, urine levels of Ca, P(i), Mg and protein were assessed. RESULTS: The pregnant women after renal transplantation presented increases in serum concentrations of total Ca (2.54+/-0.20 vs. 2.16+/-0.10 mmol/l; P<0.001) and ionized Ca(2+) (1.322+/-0.104 vs. 1.12+/-0.07 mmol/l; P<0.001) and the decrease in P(i) level (1.013+/-0.211 vs. 1.10+/-0.16 mmol/l; P<0.05), total protein (59.3+/-7.0 vs. 65+/-5 g/l; P<0.001) and albumin (461.6+/-65.65 vs. 493.2+/-59 micromol/l; P<0.05). Moreover, in the study group drop in red blood cells count to 3.71+/-0.56 vs. 4.01+/-0.35 x 10(12)/l (P<0.02) in the control group was detected. Despite increased volume of 24-h urine collection in the kidney recipients we observed significantly decreased urine 24-h calcium excretion 2.47+/-0.92 vs. 6.72+/-3.49 mmol (P<0.001) and simultaneous increase in urine Mg excretion 3.422+/-1.025 vs. 2.18+/-0.52 mmol/24 h (P<0.001). There was no difference in urine 24-h P(i) excretion between the study and the control group. The pregnant renal transplant recipients presented proteinuria of 1.19+/-1.9 g/24 h. CONCLUSIONS: Women after kidney grafting present vital aberrations in calcium-phosphorus-magnesium homeostasis during pregnancy. The most significant changes are associated with calcium metabolism (high increase in serum Ca levels and impairment of renal elimination of calcium). The observed changes may be influenced by the doses of immunosuppressive agents and disturbed renal function.  相似文献   
78.
Calcium renal lithiasis formation depends on the balance between thermodynamic (supersaturation) and kinetic (inhibitors, nucleants)factors. In this paper, the importance of both groups was evaluated using(a) the complete urine analysis data obtained from 32 healthy volunteers and 141 active stone-formers, and (b) a comprehensive computer model to calculate the supersaturation values of calcium oxalate monohydrate,hydroxyapatite and brushite in each urine sample. The results of this evaluation were used to assess the possible effectiveness of a given pharmacological treatment. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
79.
为探讨急性缺氧对家兔左心室舒张功能、心肌细胞内钙转运和能量代谢的影响。将23只家兔分为对照组(6只)、吸入5%低氧混合气的缺氧1组(H1)(12只)、吸入10%低氧混合气的缺氧2组(H2)(5只),用心导管法测定左心室压力下降最大速率(LVdp/dtmax)和压力下降时间常数(T值);测定心肌肌浆网(SR)钙ATP酶活性、心肌SR摄钙量、心肌组织ATP和磷酸肌酸(CrP)。结果,缺氧后LVdp/dtmax下降,T值延长;缺氧组心肌SR钙ATP酶活性及摄钙量下降;心肌线粒体钙含量升高;心肌组织ATP和CrP下降,心肌组织ATP与线粒体钙含量呈负相关。提示,急性缺氧可引起左心室舒张功能障碍并影响心肌SR钙转运和心肌能量代谢。  相似文献   
80.
After oral administration of the organic calcium channel blocker diltiazem to guinea pigs for 7 days, calcium ions were precipitated with potassium antimonate in the cochleae. The spatial distribution of the precipitates was studied by energy-filtering transmission electron microscopy and the amount of the ultrastructural reaction products formed was determined semiquantitatively by an image processing system. Compared with untreated control ears, the number of the formed precipitates was reduced drastically in the inner hair cells after diltiazem treatment. In addition, electron microscopic analysis revealed that the number of calcium precipitates attached at the basolateral membrane of the outer hair cells was clearly reduced when compared with untreated control specimens. A large number of histochemical reaction products could be identified in the basilar membrane and were also observed in the untreated control specimens. The spatial distribution of the calcium precipitates in the lamina reticularis was not affected by diltiazem treatment and calcium precipitates could be identified within different cell membranes. The technique used was considered to be helpful for identifying calcium channels ultrastructurally in intact undissected tissues and to support light microscopic analyses and patch-clamp electrophysiological measurements.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号