全文获取类型
收费全文 | 181787篇 |
免费 | 13008篇 |
国内免费 | 4290篇 |
专业分类
耳鼻咽喉 | 1363篇 |
儿科学 | 2544篇 |
妇产科学 | 3051篇 |
基础医学 | 23678篇 |
口腔科学 | 3411篇 |
临床医学 | 12273篇 |
内科学 | 23588篇 |
皮肤病学 | 2273篇 |
神经病学 | 12050篇 |
特种医学 | 6438篇 |
外国民族医学 | 1篇 |
外科学 | 14854篇 |
综合类 | 23975篇 |
现状与发展 | 21篇 |
一般理论 | 8篇 |
预防医学 | 15368篇 |
眼科学 | 2336篇 |
药学 | 25729篇 |
53篇 | |
中国医学 | 12713篇 |
肿瘤学 | 13358篇 |
出版年
2024年 | 426篇 |
2023年 | 2479篇 |
2022年 | 5520篇 |
2021年 | 7565篇 |
2020年 | 6225篇 |
2019年 | 6106篇 |
2018年 | 6151篇 |
2017年 | 6728篇 |
2016年 | 6752篇 |
2015年 | 6321篇 |
2014年 | 7078篇 |
2013年 | 11050篇 |
2012年 | 8929篇 |
2011年 | 10864篇 |
2010年 | 6775篇 |
2009年 | 6871篇 |
2008年 | 8416篇 |
2007年 | 9382篇 |
2006年 | 8869篇 |
2005年 | 8219篇 |
2004年 | 7059篇 |
2003年 | 6328篇 |
2002年 | 5011篇 |
2001年 | 4494篇 |
2000年 | 3758篇 |
1999年 | 3207篇 |
1998年 | 2492篇 |
1997年 | 2604篇 |
1996年 | 2387篇 |
1995年 | 2066篇 |
1994年 | 2011篇 |
1993年 | 1691篇 |
1992年 | 1553篇 |
1991年 | 1461篇 |
1990年 | 1261篇 |
1989年 | 1032篇 |
1988年 | 993篇 |
1987年 | 901篇 |
1986年 | 832篇 |
1985年 | 1244篇 |
1984年 | 989篇 |
1983年 | 749篇 |
1982年 | 784篇 |
1981年 | 630篇 |
1980年 | 613篇 |
1979年 | 481篇 |
1978年 | 303篇 |
1977年 | 260篇 |
1976年 | 245篇 |
1975年 | 187篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
用毛细管区带电泳法同时测定复方马来酸依那普利片中两组分含量。以咖啡因为内标,20mmol/L硼砂—20mmol/L磷酸二氢钠(49∶51,pH86)为运行缓冲液,在7min内完成分离。马来酸依那普利和氢氯噻嗪的线性范围分别为80~640μg/mL(r=09999)和50~400μg/mL(r=09993)。平均回收率分别为1010%和1011%,RSD分别为10%和17%,n=5。 相似文献
992.
993.
Administration of either the muscarinic antagonist scopolamine or the benzodiazepine diazepam prior to training produced a dose-dependent impairment in the retention of one-trial inhibitory avoidance training in mice. To investigate the nature of this drug effect, the effects of scopolamine and diazepam were subsequently assessed on both acquisition and retention of inhibitory avoidance using a multiple-trial, training-to-criterion procedure. The training was conducted using either continuous trials in which the mouse was free to shuttle back and forth between shock and safe compartments or discrete trials in which the mouse was moved from the shock compartment of the safe compartment at the start of each trial. In either case, training continued until the mouse refrained from crossing into the shock compartment for a specified length of time on a single trial. Scopolamine (1.0 mg/kg) administered before training significantly increased the number of trials required to attain criterion, but did not affect retention when these mice were tested 2, 16, or 28 days later. In contrast, diazepam (1.0 mg/kg) did not significantly alter the number of trials necessary to reach criterion, but impaired retention of the inhibitory response in mice trained using discrete trials. The differences in the amnestic effects of scopolamine and diazepam revealed by this detailed analysis suggest that diazepam does not impair inhibitory avoidance performance through an effect on cholinergic function. 相似文献
994.
FERRARI R.; CURELLO S.; CECONI C.; CARGNONI A.; PASINI E.; VISIOLI O. 《European heart journal》1993,14(9):1258-1272
Nisoldipine was administered at 109M, a dose lackingnegative inotropism, to isolated and perfused rabbit heartssubmitted to 60 min ischaemia (1 ml.min1) followed by30 min reperfusion. The drug was delivered either 30 min beforeischaemia, at the onset and after 30 min of ischaemia and duringreperfusion only. Cardiac protection was evaluated in termsof recovery of left ventricular pressure during reperfusion,release of creatine phosphokinase (CPK), mitochondrial function,tissue content of adenosine triphosphate (ATP) and creatinephosphate (CP), calcium homeostasis and the occurrence of oxidativestress, established measuring content and release of reducedand oxidized glutathione. The cytoprotective action of nisoldipine occurs in the absenceof negative inotropism and is closely related to the time ofadministration. Optimal myocardial preservation is achievedwhen nisoldipine is given before or at the onset of ischaemia.Prophylactic administration of nisoldipine improved the recoveryof the developed pressure from 159±10 (SE) mmHg to 478±19mmHg, P<0.01 and reduced the release of CPK from 830±29to 229±27 mU. min1 g1 wet wt, P<0.01.The accumulation of tissue and mitochondrial calcium was reducedfrom58±11 and49±9 to 14±6 and 10±4 mmol.kg1 dry wt respectively, P<0.01. This resulted ina signficant (P<0.01) preservation of all indices of mitochondrialfunction, allowing a higher recovery of ATP and CP after reperfusion(from 4.1±0.7 and 10.0±0.6 to 16.1±1.0and 29.9±0.2 µmol.g1 dry wt respectively,P<0.001). Reperfusion-induced myocardial accumulation and release of oxidizedglutathione were reduced from 0.493±0.07 nmol.mg1protein and 0.768±0.063 nmol.min1g1 wetwt to 0.225±0.07 and 0.157±0.038 respectively,P<0.01. Similar data were obtained when nisoldipine was givenat the time of ischaemia, while administration 30 min afterthe onset of ischaemia showed only a trend towards protection.Nisoldipine lost its protective effect when given on reperfusion. A multifactorial analysis of the data suggest that the cardioprotectiveeffect of nisoldipine is related to the maintenance of membraneintegrity, possibly since nisoldipine is highly lipophilic. 相似文献
995.
The effects of inhibitory (gamma-aminobutyric acid (GABA) and glycine) and excitatory (L-glutamate and DL-homocysteate, DLH) amino acids on the excitability of respiratory bulbospinal neurons were studied in decerebrate, paralyzed, bilaterally vagotomized, artificially ventilated cats. Unit activities were recorded extracellularly in the medulla in both the ventrolateral portion of the nucleus tractus solitarius and the para-ambigual region in the vicinity of the nucleus ambiguus (dorsal and ventral respiratory groups, respectively). All neurons were bulbospinal since they could be antidromically activated by electrical stimuli to the spinal cord. We used variations in antidromic latency (ADL) as a measure of changes in excitability of the soma. All neurons exhibited variations in ADL related to the respiratory cycle, being shortest (minimum ADL) during neural activity and longest (maximum ADL) in the silent period. Neurons whose discharge frequencies fell during application of putative inhibitory amino acids showed an increase of minimum ADL compared to control, indicating hyperpolarization. Minimum ADL, in some cells, became shorter during application of excitatory amino acids, indicating depolarization; in others, mechanisms secondary to increased neuronal firing likely obscured their effects. The transient maximum ADL usually present at the onset of the silent period was increased by excitatory amino acids and, in some units, was reduced or eliminated by inhibitory amino acids. These effects are discussed in terms of a modulation by synaptic inputs and neurotransmitters of the cumulative afterhyperpolarization which follows bursts of action potentials. 相似文献
996.
用蝮蛇抗检酶治疗老年冠心病50例.通过对治疗前后血液流变学变化的观察,了解到蝮蛇抗栓酶能有效改善血浓浓粘聚状态,降低纤维蛋白原,是治疗冠心病的理想药物. 相似文献
997.
Rajiv Jalan Rebecca Gooday Ronan E. O'Carroll Doris N. Redhead Robert A. Elton Peter C. Hayes 《Journal of hepatology》1995,23(6)
Background/Aims: This study was designed to assess changes in: (a) neuropsychological tests, measures of memory, quality of life and scores for anxiety and depression; (b) liver function tests; and (c) the relationship between these following transjugular intrahepatic portosystemic stent-shunt.Methods: Twenty-nine patients undergoing transjugular intrahepatic portosystemic stent-shunt for recurrent variceal haemorrhage, 12 matched patients with cirrhosis and variceal haemorrhage manage with variceal band ligation and 16 normal controls were studied. Patients in any of the groups who were clinically encephalopathic were excluded from the study. Serial changes in the conventional liver function tests and Indocyanine green clearance, and psychometric function (Hospital Anxiety Depression Scale, Rivermead Behavioral Memory Test, Quality of Life and the memory and reaction sub-tests of the Cambridge Automated Neuropsychological Test Assessment Battery) were measured prior to and 1, 3, 9 and 15 months following transjugular intrahepatic portosystemic stent-shunt.Results: Over a mean follow up of 9.1 months in the transjugular intrahepatic portosystemic stent-shunt group (range 3–28), one patient (3%) developed clinically detectable encephalopathy. Sixty-seven percent of patients with cirrhosis showed evidence of subclinical encephalopathy as compared with the control population. Significant deterioration occurred in the reaction sub-tests of the Cambridge Automated neuropsychological Test Assessment Battery in patients, both in the transjugular intrahepatic portosystemic stent-shunt group and the controls with cirrhosis, during follow up. Transjugular intrahepatic portosystemic stent-shunt was followed by significant deterioration in levels of anxiety and psychological component of the quality of life. The Rivermead Behavioural Memory Test and the memory sub-test of the Cambridge Automated Neurpsychological Test Assessment Battery did, however, improve significantly at 1 and 15 months after transjugular intrahepatic portosystemic stent-shunt, respectively. Serum alanine aminotransferase, bilirubin and indocyanine green clearance deteriorated significantly following transjugular intrahepatic portosystemic stent-shunt (p<0.001, p<0.001 and p<0.0001, respectively). Significant correlation was observed between changes in the indocyanine green clearance and changes in the complex and simple reaction time subtests of the Cambridge Automated Neuropsychological Test Assessment Battery (r=0.6 and r=0.66, respectively).Conclusions: The results of this study showed that about 67% of patients with cirrhosis were subclinically encephalopathic and that temporary deterioration occurred in the Cambridge Automated Neuropsychological Test Assessment Battery during follow up, both in patients having transjugular intrahepatic portosystemic stent-shunt and in the controls with cirrhosis. These parallel the changes in the liver function tests and indocyanine green clearance. Temporary deterioration was also observed in the Quality of Life and Hospital Anxiety Depression Scale in the transjugular intrahepatic portosystemic stent-shunt group, although the measures of memory improved. Further studies should address the biochemical mechanisms of these changes and the role of prophylactic measures. 相似文献
998.
Rajabi-Siahboomi Ali R. Bowtell Richard W. Mansfield Peter Davies Martyn C. Melia Colin D. 《Pharmaceutical research》1996,13(3):376-380
Purpose. The purpose of this study was to characterise the water mobility in the gel layer of hydrating HPMC tablets. Water mobility in the gel layer of different HPMCs was studied.
Methods. NMR imaging, a non-invasive technique, has been used to measure the spatial distribution of self-diffusion coefficient (SDC) and T2 relaxation times across the gel layer.
Results. It has been shown that there is a water mobility gradient across the gel layer of HPMC tablets. Although SDC and T2 relaxation times in the outer parts of the gel layer approached that of free water, in the inner parts they decreased progressively. Water mobility and SDC in the gel layer of different HPMCs appeared to vary with degree of substitution of the polymer and the lowest values were obtained across the gel layer of K4M tablets.
Conclusions. Water mobility varies across the gel layer of hydrating HPMC tablets and it is dependent on the degree of substitution of the polymer. 相似文献
999.
M. T. V. Chan P. J. Anderson J. C. N. Chan G. S. N. Lau J. A. J. H. Critchley 《European journal of clinical pharmacology》1997,52(4):285-288
Objective: A single oral dose of paracetamol (20 mg · kg−1) was given to 38 Chinese patients with non-insulin-dependent diabetes mellitus (NIDDM) who had either normal renal function
or varying degrees of renal impairment, with creatinine clearances ranging from 4 to 123 ml · min−1 · 1.73 m−2. The plasma and urinary concentrations of paracetamol and its major metabolites were measured by high-performance liquid
chromatography (HPLC).
Results: The absorption and elimination of paracetamol were unaffected by renal impairment. However, the area under the plasma concentration
time curve and the elimination half-life of paracetamol metabolites increased significantly with worsening renal insufficiency.
Mean renal clearances of paracetamol and its conjugates were significantly reduced in these subjects. There was no evidence
of altered metabolic activation with renal impairment.
Conclusion: The results demonstrate that paracetamol disposition is minimally affected by diabetic nephropathy; however, extensive accumulation
of conjugates may occur.
Received: 2 September 1996 / Accepted in revised form: 11 December 1996 相似文献
1000.
R. Gottschalk C. Seidl T. Löffler E. Seifried D. Hoelzer J.P. Kaltwasser 《Tissue antigens》1998,51(3):270-275
Abstract: Genetic hemochromatosis (GH) is closely associated with genes of the major histocompatibility complex (MHC) on chromosome 6. Recently, a candidate gene for GH, with structural similarities to MHC class I genes, designated HLA-H and presently named HFE, has been cloned. The HFE gene is localized telomeric to the MHC and several reports have indicated that the HFE gene is mutated in GH patients. In the present study we have analyzed the relationship of HFE gene variants and disease manifestation in GH patients and family members. Fifty-seven patients with GH, 73 family members and 153 healthy blood donors were studied for the amino acid dimorphism at codon 63 (His63Asp=H63D) and codon 282 (Cys282Tyr= C282Y) of the HFE gene. The codon 63 and 282 dimorphism were defined by PCR amplification of genomic DNA samples and restriction enzyme digestion using RsaI/SnaBI for C282Y and Bcll/Mbo 1 for H63D. Ferritin, transferrin serum levels and total iron-binding capacity were determined prior to therapeutic intervention. The Tyr-282 substitution occurred in 53 (93%) of patients compared with 8 (5.2%) of controls (OR=169, P >0.0001). Fifty-one (90%) patients were Tyr-282 homozygous. In contrast, the Asp-63 substitution was present in 5 (8.8%) of the patients compared with 34 (22%) of controls (OR=0.39, P =NS) with none of the patients being homozygous. In Tyr-282 homozygous GH patients serum ferritin levels, transferrin saturation, liver iron and liver iron index were elevated significantly compared to Tyr-282-negative patients, whereas no difference was observed between Tyr/Cys-282 heterozygous and Tyr-282-negative patients. 相似文献