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   1697篇
  免费   178篇
  国内免费   22篇
耳鼻咽喉   17篇
儿科学   62篇
妇产科学   10篇
基础医学   231篇
口腔科学   32篇
临床医学   233篇
内科学   284篇
皮肤病学   24篇
神经病学   117篇
特种医学   210篇
外科学   188篇
综合类   76篇
一般理论   1篇
预防医学   139篇
眼科学   24篇
药学   153篇
  2篇
肿瘤学   94篇
  2022年   14篇
  2021年   38篇
  2020年   15篇
  2019年   25篇
  2018年   36篇
  2017年   26篇
  2016年   16篇
  2015年   27篇
  2014年   36篇
  2013年   56篇
  2012年   70篇
  2011年   55篇
  2010年   52篇
  2009年   50篇
  2008年   64篇
  2007年   80篇
  2006年   57篇
  2005年   64篇
  2004年   64篇
  2003年   55篇
  2002年   59篇
  2001年   47篇
  2000年   55篇
  1999年   44篇
  1998年   39篇
  1997年   39篇
  1996年   42篇
  1995年   35篇
  1994年   31篇
  1993年   33篇
  1992年   39篇
  1991年   39篇
  1990年   38篇
  1989年   59篇
  1988年   43篇
  1987年   46篇
  1986年   41篇
  1985年   53篇
  1984年   30篇
  1983年   17篇
  1982年   15篇
  1981年   19篇
  1980年   21篇
  1979年   25篇
  1978年   14篇
  1977年   25篇
  1976年   17篇
  1975年   4篇
  1973年   5篇
  1972年   8篇
排序方式: 共有1897条查询结果,搜索用时 93 毫秒
91.
OBJECTIVE: This study investigated whether cancer patients with and without major depression exhibit immune system abnormalities similar to those reported in medically healthy, depressed subjects without cancer. METHOD: The study subjects consisted of patients diagnosed with pancreatic, esophageal, or breast cancer. Other groups consisted of subjects with major depression (without cancer) and healthy comparison subjects. Subjects' diagnoses were made with the Structured Clinical Interview for DSM-III-R. Severity of depression was measured with the Hamilton Depression Rating Scale. Plasma concentrations of interleukin-6 (IL-6) and postdexamethasone cortisol were measured. RESULTS: Cancer patients with depression had markedly higher plasma concentrations of IL-6 than healthy comparison subjects and cancer patients without depression. Although significant correlations were found between Hamilton depression scale scores and plasma concentrations of postdexamethasone cortisol, no significant correlations were found between plasma IL-6 and postdexamethasone cortisol concentrations. CONCLUSIONS: Higher than normal plasma IL-6 concentrations were associated with a diagnosis of major depression in cancer patients. IL-6 may contribute to sickness behavior that has overlapping symptoms with major depression.  相似文献   
92.
The toxicity of Ni(II), Co(II) and Cu(II) in animals, and that of Cd(II) in cultured cells, has been associated with generation of the promutagenic lesion 8-oxo-7,8-dihydroguanine (8-oxoguanine) in DNA, among other effects. One possible source of this base may be 8-oxo-7,8- dihydro-2'-deoxyguanosine-5'-triphosphate (8-oxo-dGTP), a product of oxidative damage to the nucleotide pool, from which it is incorporated into DNA. To promote such incorporation, the metals would have to inhibit specific cellular 8-oxo-dGTPases that eliminate 8-oxo-dGTP from the nucleotide pool. The present study was designed to test such inhibition in vitro on 8-oxo-dGTPases from two different species, the human MTH1 protein and Escherichia coli MutT protein. In the presence of Mg(II), the natural activator of 8-oxo-dGTPases, all four metals were found to inhibit both enzymes. For MTH1, the IC50 values (+/- SE; n = 3-4) were 17 +/- 2 microM for Cu(II), 30 +/- 8 microM for Cd(II), 376 +/- 71 microM for Co(II) and 801 +/- 97 microM for Ni(II). For MutT, they were 60 +/- 6 microM for Cd(II), 102 +/- 8 microM for Cu(II), 1461 +/- 96 microM for Ni(II) and 8788 +/- 1003 microM for Co(II). Thus, Cu(II) and Cd(II) emerged as much stronger inhibitors than Ni(II) and Co(II), and MTH1 appeared to be generally more sensitive to metal inhibition than MutT. Interestingly, in the absence of Mg(II), the activity of the enzymes could be restored by Co(II) to 73% of that with Mg(II) alone for MutT, and 34% for MTH1, the other metals being much less or non-effective. The difference in sensitivity to metal inhibition between the two enzymes may reflect the differences in the amino acid ligands, especially the cysteine ligand, outside their evolutionarily conserved Mg(II)-binding active sites, which might indicate predominantly non-competitive or uncompetitive mechanism of the inhibition. The overall results suggest that inhibition of 8-oxo- dGTPases may be involved in the mechanisms of induction of the 8- oxoguanine lesion in DNA by the metal ions studied, especially the non- redox-active Cd(II) cation.   相似文献   
93.
A search for children presenting with signs or symptoms of cardiac rhabdomyomas was made through members of the paediatric section of the British Cardiac Society in order to establish their birth incidence, presenting features, clinical course, and the frequency of a concurrent diagnosis of tuberous sclerosis. Fifteen children were identified and 12 had tuberous sclerosis (80%). Heart failure was the presentation in six, five of whom died; six presented because of a murmur and three because of arrhythmias. The prevalence of echocardiographic evidence of cardiac rhabdomyomas in a population of patients with tuberous sclerosis was established. Twenty individuals had echocardiography and eight had echodensities consistent with cardiac rhabdomyomas. It is concluded that the minimum birth incidence for children presenting because of the effects of cardiac rhabdomyomas is 1/326,000 and a minimum of 80% have tuberous sclerosis. In a population of patients with tuberous sclerosis a minimum of 60% under 18 years have cardiac rhabdomyomas.  相似文献   
94.
To determine the outcome of congenital lung abnormalities, data were collected retrospectively between January 1991 and December 1996 on any foetus found to have a lung lesion on antenatal ultrasound. A total of 23 foetuses had lung lesions on antenatal ultrasound. In two foetuses the antenatal ultrasound showed bilateral enlarged "bright" echogenic lungs with evidence of hydrops. Both pregnancies were terminated and tracheal atresia was confirmed. In 15 foetuses the antenatal ultrasound appearance was of a unilateral "bright" echogenic lung. There was one case of bronchial atresia and two cases of congenital lobar emphysema, which all had surgery. In nine cases there was a reduction in the size of the lesion on serial antenatal ultrasounds and no lesion was detected after birth. In three cases a small lesion was present after birth on chest radiography. In six foetuses the antenatal ultrasound appearance was of unilateral cystic or mixed cystic and echogenic lung lesions. Two pregnancies were terminated; both had congenital cystic adenomatoid malformation. Four pregnancies were continued and three infants had surgery soon after birth and were confirmed to have had congenital cystic adenomatoid malformation. One infant has been managed conservatively. In conclusion, a definitive diagnosis cannot usually be made antenatally. A large lesion on initial scan does not necessarily predict a poor outcome. The natural history of small asymptomatic postnatal lesions is unknown and a long-term prospective study is needed to determine the outcome of these lesions.  相似文献   
95.
Inflicted traumatic brain injury (TBI) is a frequent consequence of physical child abuse in infants and children. Twenty-eight children who were 2-42 months of age when hospitalized for moderate to severe TBI were enrolled in a prospective, longitudinal study of neurobehavioral outcome following acquired brain injury. Relative to a comparison group, the children with inflicted TBI had significant deficits in cognitive, motor and behavioral domains when assessed with the Bayley Scales of Infant Development-II 1 and 3 months after the injury. Nearly half of the injured children showed persisting deficits in attention/arousal, emotional regulation and motor coordination. Greater injury severity, as indicated by lower coma scale scores, longer periods of unconsciousness and the presence of edema/cerebral infarctions was associated with poorer outcomes in all domains.  相似文献   
96.
97.
98.
99.
100.
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