全文获取类型
收费全文 | 1499885篇 |
免费 | 121222篇 |
国内免费 | 3709篇 |
专业分类
耳鼻咽喉 | 19363篇 |
儿科学 | 48834篇 |
妇产科学 | 42808篇 |
基础医学 | 212072篇 |
口腔科学 | 39374篇 |
临床医学 | 135794篇 |
内科学 | 302548篇 |
皮肤病学 | 34583篇 |
神经病学 | 126167篇 |
特种医学 | 57330篇 |
外国民族医学 | 467篇 |
外科学 | 224900篇 |
综合类 | 33751篇 |
现状与发展 | 3篇 |
一般理论 | 617篇 |
预防医学 | 117572篇 |
眼科学 | 33459篇 |
药学 | 104517篇 |
1篇 | |
中国医学 | 3462篇 |
肿瘤学 | 87194篇 |
出版年
2021年 | 12822篇 |
2019年 | 13537篇 |
2018年 | 18858篇 |
2017年 | 14361篇 |
2016年 | 16070篇 |
2015年 | 18076篇 |
2014年 | 25623篇 |
2013年 | 37729篇 |
2012年 | 52177篇 |
2011年 | 55105篇 |
2010年 | 32354篇 |
2009年 | 30806篇 |
2008年 | 50738篇 |
2007年 | 53572篇 |
2006年 | 53885篇 |
2005年 | 52097篇 |
2004年 | 49815篇 |
2003年 | 47187篇 |
2002年 | 45298篇 |
2001年 | 73786篇 |
2000年 | 75073篇 |
1999年 | 62383篇 |
1998年 | 18059篇 |
1997年 | 16230篇 |
1996年 | 16244篇 |
1995年 | 15413篇 |
1994年 | 13922篇 |
1993年 | 13113篇 |
1992年 | 46241篇 |
1991年 | 43852篇 |
1990年 | 41778篇 |
1989年 | 39822篇 |
1988年 | 36435篇 |
1987年 | 35624篇 |
1986年 | 33080篇 |
1985年 | 31534篇 |
1984年 | 24102篇 |
1983年 | 20245篇 |
1982年 | 12500篇 |
1981年 | 11029篇 |
1979年 | 20800篇 |
1978年 | 14699篇 |
1977年 | 12184篇 |
1976年 | 11444篇 |
1975年 | 11682篇 |
1974年 | 14052篇 |
1973年 | 13598篇 |
1972年 | 12680篇 |
1971年 | 11509篇 |
1970年 | 10939篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
Changes in the biophysical properties and ultrastructure of lungs, and intrapulmonary fibrin deposition in experimental acute pancreatitis
下载免费PDF全文
![点击此处可从《Gut》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Using an experimental model of acute pancreatitis in the rat, we have studied changes in the biophysical properties of lungs and intrapulmonary fibrin deposition in this condition. Acute pancreatitis is associated with a significant decrease in pulmonary compliance (p less than 0.01) and a significant increase in lung weight (p less than 0.01) compared with a control sham operation group. These changes are associated with a 24% increase in intrapulmonary 125I fibrinogen deposition (p less than 0.01), and an 18% increase in 125I fibrinogen deposition per gram of lung tissue (p less than 0.05) in acute pancreatitis, compared with a control sham operation group. The increased fibrinogen deposition is abolished by treatment with low dose heparin. Using the same animal model changes in pulmonary ultrastructure are shown using scanning electron microscopy. The results indicate that pulmonary abnormalities are associated with intrapulmonary fibrin deposition in experimental acute pancreatitis and these findings may be relevant to the well described respiratory complications of the condition in man. 相似文献
993.
Valve-related complications with the Hancock I porcine bioprosthesis. A twelve- to fourteen-year follow-up study 总被引:4,自引:0,他引:4
J M Bernal J M Rabasa J C Cagigas J R Echevarria M F Carrion J M Revuelta 《The Journal of thoracic and cardiovascular surgery》1991,101(5):871-880
Valve-related morbidity and mortality after heart valve replacement with the Hancock I porcine bioprosthesis has been retrospectively analyzed. From June 1974 through December 1976, 253 Hancock I bioprostheses (150 mitral and 103 aortic) were inserted in 220 selected patients who survived the operation and had follow-up until June 1989 (mean follow-up 13.5 years, with an accumulative follow-up of 2956.4 patient-years). One hundred seventeen patients had mitral valve replacement, 70 had aortic valve replacement, and 33 had combined mitral and aortic valve replacement. There were 27 thromboembolic events. The probability of being free from thromboembolism at 14 years was 81.0% +/- 7.4% for the mitral valve replacement group, 85.4% +/- 6.7% for the aortic group, and 67.1% +/- 18.4% for the mitral-aortic group. Fifteen episodes of prosthetic valve endocarditis occurred. There were 10 instances of nonstructural dysfunction (paravalvular leaks) in seven mitral valves (4.6%) and in three aortic valves (2.9%). One hundred twenty-two bioprostheses in 106 patients resulted in structural deterioration. The probability of freedom from structural deterioration at 14 years was 37.2% +/- 3.9% for the mitral group, 43.9% +/- 7.1% for the aortic group, and 30.1% +/- 8.9% for the mitral-aortic group. The logistic regression analysis between age at the time of operation and bioprosthetic life (structural deterioration-free period) demonstrates a linear regression curve (r = 0.53). There were 56 late deaths (27 patients died at reoperation). The actuarial survival rate (including hospital mortality) at 14 years was 57.2% +/- 5.4% for the entire series, with no statistically significant difference between groups. The probability of remaining free from valve-related morbidity and mortality at 14 years was 16.7% +/- 4.8% for the mitral group, 20.8% +/- 6.2% for the aortic group, and 14.0% +/- 7.0% for the mitral-aortic group. The long-term results of this series show that the clinical performance of the Hancock I porcine valve appears satisfactory during the first 6 years. The behavior of this bioprosthesis at 14 years' follow-up changes drastically, because only a minor group of patients is free from valve-related complications, justifying the restriction of its use for selected patients. 相似文献
994.
Depressed levels of circulating menaquinones in patients with osteoporotic fractures of the spine and femoral neck 总被引:3,自引:0,他引:3
S.J. Hodges M.J. Pilkington T.C.B. Stamp A. Catterall M.J. Shearer L. Bitensky J. Chayen 《BONE》1991,12(6):387-389
Vitamin K1 functions in the conversion of glutamate residues, present in certain bone peptides, into the putatively active γ-carboxyglutamate form. We have shown previously that the circulating levels of vitamin K1 are depressed in osteoporotic patients. However, it is known that menaquinones (vitamin K2:MK) may be more effective than vitamin K1 in this conversion of the inactive to active form of glutamate residues. A procedure for measuring such menaquinones has now demonstrated a marked deficiency of MK-7 and MK-8 in patients with osteoporotic fractures. It is suggested that estimates of circulating levels of K1, MK-7, and MK-8 might provide a biochemical risk marker of osteoporotic fractures. 相似文献
995.
Long-term results of pectoralis major muscle transposition for infected sternotomy wounds. 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Annals of surgery》网站下载免费的PDF全文](/ch/ext_images/free.gif)
During an 11.5-year period, 100 consecutive patients (79 male, 21 female) underwent repair of an infected sternotomy wound. Sixty-five patients had failed attempts at wound closure by other physicians. Median age was 61.5 years (range, 5 to 85 years). Reconstruction included muscle in 79 patients, omentum in 4, and both in 15. A total of 175 muscles were transposed, including 169 pectoralis major, 3 rectus abdominis, 2 external oblique, and 1 latissimus dorsi. Median number of operations was four (range, 1 to 11). Mechanical ventilation was required in 30 patients. Two perioperative deaths occurred, one related to sepsis. Median follow-up was 4.2 years (range, 1.3 to 13.5 years). Twenty-six patients had recurrent infection. Median time from our closure to recurrence was 5.5 months (range, 0.3 to 27.6 months). Cause of recurrence was inadequate removal of cartilage in 16 patients, bone in 6, and retained foreign body in 4. Eighteen patients had the wound reopened with further resection; 10 had another muscle or omentum transposition. There were 30 late deaths, only one related to recurrent infection. At the time of death or last follow-up, 92 patients had a healed chest wall. Transposition of the pectoralis major muscle remains an excellent method of management for infected sternotomy wounds. Failure is directly related to persistent infection of cartilage, bone, or retained foreign bodies. 相似文献
996.
997.
Cloning and characterization of Ca(2+)-dependent and Ca(2+)-independent PKCs expressed in Aplysia sensory cells 总被引:2,自引:0,他引:2
K E Kruger W S Sossin T C Sacktor P J Bergold S Beushausen J H Schwartz 《The Journal of neuroscience》1991,11(8):2303-2313
We isolated cDNA clones from an Aplysia sensory-cell library encoding two isoforms of protein kinase C (PKC). Several isozyme-specific regions are conserved in the Aplysia kinases, notably the variable regions V5 in the Ca(2+)-dependent PKC (Apl I) and V1 in the Ca(2+)-independent PKC (Apl II). Neuronal proteins with the properties expected of these two isoforms can be identified with antibodies raised against peptides synthesized from the amino acid sequences deduced from the clones. Sacktor and Schwartz (1990) measured the proportion of kinase activity that can be translocated to membrane in Aplysia sensory neurons and ganglia by stimuli that produce the presynaptic facilitation underlying behavioral sensitization. Much less Apl I and Apl II are translocated, suggesting that still other isoforms of PKC exist in these cells. 相似文献
998.
M. D. Taylor M. L. de Ceballos S. Rose P. N. Chong P. Jenner C. D. Marsden 《Journal of neural transmission (Vienna, Austria : 1996)》1991,3(2):99-108
Summary Aged common marmosets were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 0.5–2.0 mg/kg/week i.p.) for 16 or 24 weeks, observed for a total of 30 weeks and then killed for measurement of biochemical pramaters in basal ganglia. The MPTP treatment induced a marked depletion in dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid levels in the caudate nucleus and putamen. In contrast, the concentrations of five neuropeptides: [Met5]-enkephalin, [Leu5]-enkephalin, cholecystokinin, substance P and neurotensin as measured by a combined HPLC/RIA method, remained unaltered in all basal ganglia regions examined. Enkephalin precursor levels, as reflected by cryptic [Met5]-enkephalin content, were increased in the putamen, but not in the caudate nucleus, as a consequence of MPTP administration. Cryptic [Leu5]-enkephalin content remained unchanged in the striatum of MPTP treated marmosets. Overall, these results suggest an increase in striatal [Met5]-enkephalin release following chronic MPTP treatment of aged marmosets. However, the chronic treatment of aged marmosets with MPTP does not reproduce the neuropeptide alterations characteristic of Parkinson's disease. 相似文献
999.
Ticlopidine and clopidogrel (SR 25990C) selectively neutralize ADP inhibition of PGE1-activated platelet adenylate cyclase in rats and rabbits 总被引:1,自引:0,他引:1
G Defreyn C Gachet P Savi F Driot J P Cazenave J P Maffrand 《Thrombosis and haemostasis》1991,65(2):186-190
Ticlopidine and its potent analogue, clopidogrel, are powerful inhibitors of ADP-induced platelet aggregation. In order to improve the understanding of this ADP-selectivity, we studied the effect of these compounds on PGE1-stimulated adenylate cyclase and on the inhibition of this enzyme by ADP, epinephrine and thrombin. Neither drug changed the basal cAMP levels nor the kinetics of cAMP accumulation upon PGE1-stimulation in rat or rabbit platelets, which excludes any direct effect on adenylate cyclase or on cyclic nucleotide phosphodiesterase. However, the drop in cAMP levels observed after addition of ADP to PGE1-stimulated control platelets was inhibited in platelets from treated animals. In contrast, the drop in cAMP levels produced by epinephrine was not prevented by either drug in rabbit platelets. In rat platelets, thrombin inhibited the PGE1-induced cAMP elevation but this effects seems to be entirely mediated by the released ADP. Under these conditions, it was not surprising to find that clopidogrel also potently inhibited that effect of thrombin on platelet adenylate cyclase. In conclusion, ticlopidine and clopidogrel selectively neutralize the ADP inhibition of PGE1-activated platelet adenylate cyclase in rats and rabbits. 相似文献
1000.
K Negishi K Sugawara S Shinagawa T Teranishi C H Kuo Y Takasaki 《Brain research. Developmental brain research》1991,63(1-2):71-83
Effects of a photoreceptor-specific biotoxin, tunicamycin (TM), injected intravitreally into the goldfish eye at one side, were explored on electroretinograms (ERGs) and proliferating cell nuclear antigen-immunoreactive (PCNA-ir) nuclei, representing the mitotic activity of rod precursors, in the retina at both sides. The eye-cup preparations were made for ERG recording, and the retinas were isolated and processed as cryosections or wholemounts by a routine immunohistochemical method for visinin (cones), opsin (rods), tyrosine hydroxylase (dopaminergic cells) and proliferating cell nuclear antigen (PCNA), at various intervals after intravitreal injection with TM (1.0 micrograms/eye). On some thin sections, autoradiographic study was combined following intravitreal injection with [3H]thymidine (TdR, 0.1 microCi/eye). The dose of TM used heavily destroyed cones and rods only in the treated retinas 2-15 days after injection, the photoreceptors being renewed for further 15-20 days. Approximately in parallel, ERGs were largely impaired 2-10 days after TM injection and recovered for 10-20 days. However, intravitreal TM altered the distribution and density of PCNA-ir nuclei in both treated and untreated retinas. The density of PCNA-ir nuclei reduced at first (on days 1 and 2), and then clustered and rapidly increased on days 3-5 and maintained at high levels with diffuse distribution over the whole area, particularly in the treated retinas, up to 60 days after TM injection; the maximum peak of 3.7 and 20 times the initial level was seen on day 20 in the outer nuclear layer (ONL) and inner nuclear layer (INL), respectively. PCNA-ir nuclei were found to be abundant in the ONL even after the photoreceptors and ERGs had been restored in the treated retinas on day 20, suggesting a kind of overproduction of retinal cells. The autoradiographic study provided comparable results to those obtained with PCNA immunohistochemistry. The mechanism by which damage to the treated retina causes rod precursor cells to proliferate in the untreated retina remains unresolved. 相似文献