全文获取类型
收费全文 | 48909篇 |
免费 | 3149篇 |
国内免费 | 177篇 |
专业分类
耳鼻咽喉 | 880篇 |
儿科学 | 1105篇 |
妇产科学 | 988篇 |
基础医学 | 7132篇 |
口腔科学 | 797篇 |
临床医学 | 4248篇 |
内科学 | 10039篇 |
皮肤病学 | 1086篇 |
神经病学 | 4869篇 |
特种医学 | 2021篇 |
外国民族医学 | 4篇 |
外科学 | 8511篇 |
综合类 | 338篇 |
一般理论 | 31篇 |
预防医学 | 2699篇 |
眼科学 | 1527篇 |
药学 | 2957篇 |
中国医学 | 104篇 |
肿瘤学 | 2899篇 |
出版年
2023年 | 222篇 |
2022年 | 424篇 |
2021年 | 855篇 |
2020年 | 507篇 |
2019年 | 900篇 |
2018年 | 1033篇 |
2017年 | 791篇 |
2016年 | 928篇 |
2015年 | 1054篇 |
2014年 | 1470篇 |
2013年 | 1881篇 |
2012年 | 2789篇 |
2011年 | 2886篇 |
2010年 | 1819篇 |
2009年 | 1620篇 |
2008年 | 2670篇 |
2007年 | 2844篇 |
2006年 | 2625篇 |
2005年 | 2720篇 |
2004年 | 2534篇 |
2003年 | 2483篇 |
2002年 | 2440篇 |
2001年 | 1101篇 |
2000年 | 1027篇 |
1999年 | 1014篇 |
1998年 | 662篇 |
1997年 | 579篇 |
1996年 | 492篇 |
1995年 | 494篇 |
1994年 | 418篇 |
1993年 | 389篇 |
1992年 | 671篇 |
1991年 | 629篇 |
1990年 | 527篇 |
1989年 | 552篇 |
1988年 | 473篇 |
1987年 | 465篇 |
1986年 | 490篇 |
1985年 | 419篇 |
1984年 | 348篇 |
1983年 | 304篇 |
1982年 | 230篇 |
1981年 | 216篇 |
1980年 | 184篇 |
1979年 | 258篇 |
1978年 | 179篇 |
1977年 | 178篇 |
1975年 | 164篇 |
1974年 | 171篇 |
1973年 | 198篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
A case-control study was conducted to test the hypothesis that chronic ingestion of trihalomethanes (THMs), occurring as chlorination byproducts in drinking water, carries a risk of colon cancer. Lifetime residential and water source histories and information on water-drinking habits, diet, sociodemographics, medical and occupation histories, lifestyle and other factors were obtained by questionnaire from a statewide sample of newly-diagnosed colon cancer cases (N = 347), controls with cancer of other sites (N = 639) and general population controls (N = 611). Since no data on past THM levels exists, it was necessary to devise a scheme to generate THM estimates for all Wisconsin water sources. For this, a statistical model based on quantitative THM measures and routinely-recorded data taken at 81 municipal water facilities was used in conjunction with individual residential histories to estimate lifetime and period-specific THM exposure for each case and control. Logistic regression was used to estimate odds ratios adjusted for age, sex and urban living, for colon cancer and THM exposure. The study results indicate that THM in Wisconsin drinking water does not pose a significant colon cancer risk. Odds ratios for exposure to the middle and highest category of lifetime cumulative THM were 1.05 (95% Cl = 0.66-1.68) and 0.93(95%Cl = 0.55-1.57) respectively, relative to the cancer control group, and 1.10 (95%Cl = 0.68-1.78) and 0.73 (95% Cl = 0.44-1.21) respectively, relative to the general population controls.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
92.
93.
I Mercanti F Michel L Thomachot D-A Loundou C Nicaise R Vialet J-N Di Marco P Lagier C Martin 《Archives de pédiatrie》2007,14(7):875-880
Transcutaneous bilirubinometry is an effective screening tool for neonatal jaundice in full-term babies. But its accuracy is not shown yet in preterm infants. METHODOLOGY: We carried out a prospective study in a neonatal intensive care unit. The study included 47 preterm infants. From birth, a transcutaneous bilirubin measurement (BTc) using the BiliCheck was made on the forehead of each newborn every 8 h. Blood sampling for determination of total serum bilirubin (BS) was combined with BTc: 1) if value of BTc was higher than limits values for phototherapy; 2) on the second day of life and 3) 4 hours after cessation of phototherapy. RESULTS: Mean gestational age was 30 week and mean birth weight was 1419 g. We studied 151 pairs of BTc and BS. Mean values obtained by BTc and BS were respectively 160.6+/-50 mumol/L and 190.6+/-61.4 mumol/L. A significant correlation between BTc and BS was found. But the limits of agreement were very wide. The negative predictive value (NPV) of BTc was above 90% in each group of gestational age. DISCUSSION: The need for phototherapy cannot be determined by BTc in preterm infants. But the BTc is reliable when its value is under the limits for phototherapy. CONCLUSION: With a very high incidence of neonatal jaundice (87%) in our cohort, a value of BTc under the limits for phototherapy has a good NPV in preterm infants. 相似文献
94.
95.
Nine patients have undergone single-stage radical cystectomy and ileal conduit urinary diversion two to fifty-one months after coronary artery bypass procedures. Two patients presenting with intractable angina at the time their malignant disease was being evaluated required bypass surgery before cystectomy could be undertaken. No significant cardiac morbidity occurred postoperatively, and all remain alive without evidence of malignant disease. 相似文献
96.
97.
Véronique Strijckmans Michel Bottlaender Humin Luo Michèle Ottavianil Daniel W. McPherson Christian Loc'h Chantal Fuseau Furn F. Knapp Bernard Mazière 《European journal of nuclear medicine and molecular imaging》1997,24(5):475-482
We studied the potential of three radiobrominated isomers of BrQNP, (Z(-,-)-[76Br]BrQNP,E(-,-)-[76Br]BrQNP andE(-,+)-[76Br]BrQNP), as suitable radioligands for imaging of central muscarinic cholinergic receptors in the human brain. These radioligands were stereospecifically prepared by electrophilic radiobromodestannylation of the respective tributylstannyl precursors using no-carrier-added [76Br]BrNH4 and peracetic acid. Preliminary pharmacological characterizations were determined by biodistribution, autoradiography, competition, displacement and metabolite studies in rats. The (-,-)-configuration presented important specific uptakes in brain muscarinic cholinergic receptor (mAChR)-rich structures and in heart, low metabolization rates and an apparent M2 selectivity. The (-,+)-configuration revealed more rapid clearance, lower uptake, a higher metabolization rate and an apparent M1 selectivity. Reversibility of the binding was confirmed for the three radiotracers. Positron emission tomography in the living baboon brain revealed high and rapid uptake in the brain and accumulation in the mAChR-rich structures studied. At 30 min p.i., theE(-,-)-radiotracer reached a plateau in cortex, pons and thalamus with concentrations of 29%, 24% and 19% ID/l, respectively.Z(-,-)-[76Br]BrQNP also accumulated in these structures, reaching a maximal uptake (27% ID/l) in the cortex 2 h p.i. At 5 min p.i. a plateau (17% ID/l) was only observed in the cortex for theE(-,+)-[76Br]BrQNP; by contrast, the other structures showed slow washout. After 3 weeks, the (-,-)-radiotracers were studied in the same baboon pretreated with dexetimide (1 mg/kg), a well-known muscarinic antagonist. In all the mAChR structures, the highly reduced uptake observed after this preloading step indicates that these radiotracers specifically bind to muscarinic receptors.Z(-,-)-[76Br]BrQNP, which is displaced in higher amounts from M2 mAChR-enriched structures, reveals an M2 affinity. The two isomers having the (-,-)-configuration are potential probes for investigating central muscarinic receptors. The absolute configuration on the acetate chiral centre influences their muscarinic subtype selectivity and thecis-trans isomerism of the vinyl moiety affects their specific fixation. 相似文献
98.
Previous work from our laboratory showed that spontaneous contractile activity of jejunal smooth muscle increases after small
bowel transplantation. Our aim was to determine whether small bowel transplantation alters the function of nonadrenergic,
noncholinergic (NANC) nerves. Seven groups of rats, (n ≥7 in each group) were studied as follows: 1 week after sham celiotomy
and 1 week and 8 weeks after 45 minutes of ischemia/ reperfusion (IR1 and IR8), jejunal and ileal transection and reanastomosis
(TR1 and TR8), or orthotopic small bowel transplantation (TX1 and TX8). Contractility of jejunal circular muscle strips was
studied in vitro. Spontaneous contractile activity increased in the IR1, TR1, and TX1 and TX1 and TX8 groups (P<0.01). Under NANC conditions, spontaneous activity increased in TR1 and in both TX1 and TX8 (P<0.01) despite the lack of an increase in the frequency of contraction in TX1. Electrical field stimulation inhibited contractile
activity at low frequencies, but under NANC conditions this inhibition persisted at higher frequencies. The calculated equieffective
frequency (F100) that produced a response equal to baseline contractile activity was similar in all groups, but under NANC conditions was
greater in TX1 (P<0.025). Functional alterations of NANC nerves are partly responsible for the increase in spontaneous activity in rat jejunal
circular muscle strips after a limited ischemia/reperfusion injury, after selective disruption of enteric neural continuity
(transection/reanastomosis), and after small bowel transplantation. These findings may provide important insight into graft
dysfunction after small bowel transplantation in humans.
Supported by United States Public Health Service grant DK 39337 from the National Institutes of Health and by the Mayo Foundation. 相似文献
99.
Michael P Hill Erwan Bezard Steven G McGuire Alan R Crossman Jonathan M Brotchie Ann Michel Renee Grimée Henrik Klitgaard 《Movement disorders》2003,18(11):1301-1305
Long-term dopamine replacement therapy of Parkinson's disease leads to the occurrence of dyskinesias. Altered firing patterns of neurons of the internal globus pallidus, involving a pathological synchronization/desynchronization process, may contribute significantly to the genesis of dyskinesia. Levetiracetam, an antiepileptic drug that counteracts neuronal (hyper)synchronization in animal models of epilepsy, was assessed in the MPTP-lesioned marmoset model of Parkinson's disease, after coadministration with (1) levodopa (L-dopa) or (2) ropinirole/L-dopa combination. Oral administration of levetiracetam (13-60 mg/kg) in combination with either L-dopa (12 mg/kg) alone or L-dopa (8 mg/kg)/ropinirole (1.25 mg/kg) treatments was associated with significantly less dyskinesia, in comparison to L-dopa monotherapy during the first hour after administration. Thus, new nondopaminergic treatment strategies targeting normalization of abnormal firing patterns in basal ganglia structures may prove useful as an adjunct to reduce dyskinesia induced by dopamine replacement therapy without affecting its antiparkinsonian action. 相似文献
100.
Prior studies of alterations in tumor expression of normal blood group antigens and A9/alpha 6 beta 4 integrin, an extracellular matrix receptor, have suggested that these immunohistologic markers reflect the biologic aggressiveness of head and neck squamous carcinomas. To confirm these preliminary observations, prospective long-term follow-up of 82 previously untreated head and neck squamous carcinoma patients was performed. All patients were treated with conventional therapy. Median follow-up was 57 months. Tumor immunohistology for ABH blood group and A9/alpha 6 beta 4 integrin expression was performed and correlated with measures of host cellular immunity, disease-free survival, and overall survival. Loss of blood group expression and high A9/alpha 6 beta 4 integrin expression were each directly related to an increased frequency of early tumor recurrence. The combination of both variables was significantly associated with both disease-free (P = .029) and overall survival (P = .05). Increased expression of A9/alpha 6 beta 4 was associated with impaired T-lymphocyte function (P = .005), and loss of blood group expression was associated with decreased peripheral blood levels of CD8+ T-lymphocytes (P = .013). The findings suggest that these phenotypic characteristics of antigen expression in head and neck squamous carcinomas are important markers of biologically aggressive cancers and impaired host immune response. The clinical use of these biologic staging parameters in the initial assessment of patients should allow selection of more aggressive primary treatment strategies for individual patients. 相似文献