全文获取类型
收费全文 | 1837篇 |
免费 | 95篇 |
国内免费 | 1篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 45篇 |
妇产科学 | 144篇 |
基础医学 | 193篇 |
口腔科学 | 23篇 |
临床医学 | 182篇 |
内科学 | 205篇 |
皮肤病学 | 19篇 |
神经病学 | 303篇 |
特种医学 | 243篇 |
外科学 | 263篇 |
综合类 | 28篇 |
预防医学 | 84篇 |
眼科学 | 8篇 |
药学 | 91篇 |
1篇 | |
肿瘤学 | 88篇 |
出版年
2021年 | 23篇 |
2019年 | 21篇 |
2018年 | 31篇 |
2016年 | 24篇 |
2015年 | 35篇 |
2014年 | 28篇 |
2013年 | 49篇 |
2012年 | 60篇 |
2011年 | 66篇 |
2010年 | 30篇 |
2009年 | 30篇 |
2008年 | 55篇 |
2007年 | 54篇 |
2006年 | 50篇 |
2005年 | 57篇 |
2004年 | 50篇 |
2003年 | 48篇 |
2002年 | 55篇 |
2001年 | 46篇 |
2000年 | 54篇 |
1999年 | 45篇 |
1998年 | 27篇 |
1997年 | 39篇 |
1996年 | 36篇 |
1995年 | 41篇 |
1994年 | 32篇 |
1993年 | 22篇 |
1992年 | 40篇 |
1991年 | 43篇 |
1990年 | 40篇 |
1989年 | 45篇 |
1988年 | 52篇 |
1987年 | 45篇 |
1986年 | 48篇 |
1985年 | 40篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 27篇 |
1981年 | 22篇 |
1979年 | 24篇 |
1978年 | 22篇 |
1976年 | 23篇 |
1974年 | 26篇 |
1973年 | 23篇 |
1971年 | 26篇 |
1970年 | 23篇 |
1969年 | 19篇 |
1968年 | 19篇 |
1967年 | 18篇 |
1966年 | 17篇 |
排序方式: 共有1933条查询结果,搜索用时 15 毫秒
1.
2.
3.
STUDY OBJECTIVE: To assess the clinical utility of measuring urinary pregnanediol glucuronide in random samples in an infertility practice. DESIGN: Samples of urine were collected from patients approximately 3 weeks from their last menstrual period to ascertain if ovulation had occurred. Each sample was tested for specific gravity before analyzing for pregnanediol glucuronide. Simultaneous venipuncture was performed to compare results from the urinary assay to quantitative measures of serum progesterone (P). SETTING: All patients were randomly sampled. PATIENTS: Three hundred ninety women undergoing pituitary down regulation with leuprolide acetate were chosen for study because they routinely initiate medication after documentation of ovulation. OUTCOME MEASURES: The performance of the urinary pregnanediol glucuronide was evaluated as to its sensitivity, specificity, predictive value, and test efficiency compared with a serum measurement of 2.5 ng/mL and 10.0 ng/mL. RESULTS: The performance characteristics of the pregnanediol glucuronide assay were directly related to the hydration status of the patient at the time of sample collection. Regardless of urine specific gravity, if pregnanediol glucuronide was qualitatively detected (greater than 3 micrograms/mL), serum P was greater than 2.5 ng/mL. However, in cases in which pregnanediol glucuronide was undetected (less than 3 micrograms/mL), results were only accurate when the specific gravity was greater than or equal to 1.020. When comparing urinary pregnanediol glucuronide values to serum greater than 10 ng/mL, both specificity and predictive value of a positive test decreased because of increased numbers of false-positive results. CONCLUSIONS: The enzyme immunoassay measurement for pregnanediol glucuronide may replace the use of serum P in documenting the ovulatory status of many patients. However, all specimens must be checked for specific gravity and if less than 1.020, a serum P should be used to ensure accuracy. 相似文献
4.
5.
The retention of [99mTc]-d,l-HM-PAO in the human brain after intracarotid bolus injection: a kinetic analysis 总被引:1,自引:0,他引:1
N A Lassen A R Andersen L Friberg O B Paulson 《Journal of cerebral blood flow and metabolism》1988,8(6):S13-S22
[99mTc]-d,l-HM-PAO (HM-PAO) was injected rapidly into the internal carotid artery and its retention in the brain was recorded by external scintillation cameras in eight human subjects. A model is described based on three compartments: the lipophilic tracer in the blood pool of the brain, the lipophilic tracer inside the brain, and the hydrophilic form retained in the brain. The retention curve initially drops abruptly, corresponding to the nonextracted fraction of the injectate leaving the brain; it then falls exponentially towards the asymptotic level of the fractional steady-state retention R. Cerebral blood flow (F) was measured using the xenon-133 intracarotid injection method. The first-pass extraction E of HM-PAO was calculated from F using an empiric regression equation. The residue curves for the whole brain after intracarotid HM-PAO injection were analyzed to yield a retention fraction (R') and the brain clearance backflux constant of lipophilic HM-PAO (k). From the kinetic model and the measured values of R', k, and F, the following parameter values could be calculated: the average retained fraction of all tracer supplied to the brain, R = 0.38 +/- 0.05 (mean +/- SD), the conversion rate constant (lipophilic to hydrophilic tracer) in the brain k3 = 0.80 +/- 0.12 min-1, the efflux rate constant (brain to blood) k2 = 0.69 +/- 0.11 min-1, the conversion/clearance ratio alpha = k3/k2 = 1.18 +/- 0.25, the influx (blood clearance) constant K1 = 0.45 +/- 0.11 ml/g/min, and the brain/blood partition ratio lambda = K1/k2 = 0.67 +/- 0.23 ml/g. Using the kinetic model and assuming constancy of alpha, an algorithm was developed that corrects for the blood flow dependent backflux of HM-PAO and results in a more linear relation between regional cerebral blood flow (rCBF) and HM-PAO distribution. 相似文献
6.
Morris R.S.; Paulson R.J.; Sauer M.V.; Lobo R.A. 《Human reproduction (Oxford, England)》1995,10(4):811-814
Ovarian hyperstimulation syndrome (OHSS) is a serious complicationof gonadotrophin usage but it is difficult to accurately predictits occurrence. Previous investigators have identified the combinationof high oestradiol concentrations and oocyte number as beingpredictive in 80% of cases. In this study we sought to identifythe incidence of severe OHSS in patients with high oestradiolconcentrations and large numbers of oocytes and to evaluatethe importance of pregnancy in the development of OHSS. Between1990 and 1993, we studied 139 cycles using two assisted reproductivetechniques [oocyte donor, n =72; in-vitro fertilization (IVF),n = 67] in which either oestradiol (>4000 pg/ml), oocytenumber (>25), or both were elevated. OHSS was diagnosed bystandard criteria. There were no cases of severe OHSS in theoocyte donor group and six in the IVF group. Among 10 patientswith oestradiol concentration >6000 pg/ml and >30 oocytes,only one had OHSS (10%). The relative risk of OHSS with pregnancywas 12 (confidence interval 2.1866.14). We conclude thatthe risk of OHSS even at high levels of stimulation is lowerthan previously believed. Secondly, donors have a very low riskof OHSS, probably because of the absence of pregnancy. As such,cryopreservation of all oocytes in IVF cycles is a reasonablealternative to cycle cancellation or use of adjunctive medication. 相似文献
7.
8.
A total of 143 patients underwent radical prostatectomy. Surgical specimens were evaluated with respect to local extent of disease, Gleason grade of the primary and relative nuclear roundness of the surgical specimen. The probability of disease control in the total population was 88 per cent at 5 years. Only 8 per cent of the patients who had disease confined to the specimen failed compared to 14 per cent of those who demonstrated extension outside of the surgical margins. The incidence of failure increased as a function of seminal vesicle involvement. Seminal vesicle involvement was greatest among patients with a Gleason grade greater than 7. Postoperative radiation did not offer any apparent advantage in patients with positive margins. 相似文献
9.
10.
Abstract— The anticonvulsant action of midazolam and clonazepam was studied in 168 immature rats in three age groups (12, 18 and 25 days old). Epileptic after-discharges of the spike-and-wave type accompanied by clonic seizures of facial and forelimb muscles induced by stimulation of sensorimotor cortex were used as a model. The solvent used for clonazepam exhibited a tendency to anticonvulsant action in 12-day-old rats. On the contrary, a proconvulsant action was seen in 25-day-old animals. The action of both benzodiazepines was identical and did not change substantially during development. The highest dose used (1 mg kg?1, i.p.) shortened the duration of epileptic after-discharges, the two lower doses (0·1 and 0·02 mg kg?1, i.p.) suppressed the progressive prolongation with repeated stimulations seen under control conditions. Motor correlates of stimulation remained practically uninfluenced by the two benzodiazepines, myoclonic seizures accompanying epileptic after-discharges were attenuated by the highest dose of both drugs. 相似文献