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   3930194篇
  免费   292438篇
  国内免费   6740篇
耳鼻咽喉   56435篇
儿科学   124462篇
妇产科学   105524篇
基础医学   565095篇
口腔科学   112353篇
临床医学   361106篇
内科学   750614篇
皮肤病学   83421篇
神经病学   319409篇
特种医学   151307篇
外国民族医学   1277篇
外科学   590288篇
综合类   89532篇
现状与发展   13篇
一般理论   1601篇
预防医学   317302篇
眼科学   93796篇
药学   294057篇
  14篇
中国医学   7544篇
肿瘤学   204222篇
  2018年   42154篇
  2017年   31979篇
  2016年   35678篇
  2015年   40297篇
  2014年   57637篇
  2013年   87685篇
  2012年   119237篇
  2011年   126770篇
  2010年   75403篇
  2009年   71368篇
  2008年   119352篇
  2007年   127158篇
  2006年   128377篇
  2005年   124774篇
  2004年   120036篇
  2003年   115494篇
  2002年   113126篇
  2001年   175006篇
  2000年   180520篇
  1999年   152751篇
  1998年   45572篇
  1997年   40420篇
  1996年   40004篇
  1995年   38313篇
  1994年   35716篇
  1993年   33533篇
  1992年   121565篇
  1991年   118592篇
  1990年   115259篇
  1989年   111029篇
  1988年   102908篇
  1987年   101056篇
  1986年   95408篇
  1985年   91682篇
  1984年   69236篇
  1983年   59070篇
  1982年   35782篇
  1981年   32029篇
  1979年   64950篇
  1978年   46065篇
  1977年   38657篇
  1976年   36861篇
  1975年   39071篇
  1974年   47643篇
  1973年   45355篇
  1972年   42864篇
  1971年   40110篇
  1970年   37345篇
  1969年   35143篇
  1968年   32280篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Budesonide-containing Apulein ointment has been used for the treatment of 29 women suffering from vulvitis, pruritus vulvae caused by vaginal discharge, gestational inflamed hemorrhoid, hymenitis, and late postoperative suture inflammation. The ointment rapidly and completely controlled local infiltration and the accompanying subjective complaints. It did not cause local alteration, the consistency of the ointment met the requirements and it did not disturb the patients' making their toilet. According to the author's opinion the product is a potent antiphlogistic which proved to be a valuable adjuvant to target specific treatment of inflammatory processes of the external female genital organs and perianal regions.  相似文献   
992.
A case illustrating the potentially fatal complication of endogenous Gram Negative Aerobic Bacillus (GNAB) septicaemia secondary to nosocomial pneumonia is presented along with current theories as to its aetiology. The technique of selective decontamination of the digestive tract is designed and advocated to prevent such occurrences; oral and maxillofacial surgeons should be aware of this approach. It may be, however, that by using much simpler manoeuvres such as changes in policy regarding gastric stress ulcer prophylaxis, the already small risk of such an occurrence will be further reduced. Awareness of this condition will allow a higher index of suspicion when presented with catastrophic septic complications on the ITU and aid in more rational planning of antimicrobial therapy.  相似文献   
993.
OBJECTIVE: To measure the effect of androgens or aromatase activity as an index of androgen responsiveness in patients with androgen insensitivity. DESIGN: Genital skin fibroblasts were established in culture using primary skin explants obtained from normal males at the time of circumcision and from androgen insensitive patients who had surgery either for gonadectomy (complete androgen insensitivity syndrome) or for reconstruction of the external genitalia (partial androgen insensitivity syndrome). PATIENTS: Foreskin samples were obtained at the time of circumcision in 27 normal males. Scrotal or labia majora skin was obtained at the time of surgery from 14 patients with the complete and 22 with the partial forms of the androgen insensitivity syndrome. MEASUREMENTS: Basal and stimulated levels of aromatase activity were measured in genital skin fibroblasts following preincubation with natural and synthetic, nonmetabolizable androgens. RESULTS: Following a 48-hour preincubation with testosterone or dihydrotestosterone, there was a five to six-fold stimulation of aromatase activity in normal fibroblasts. Mibolerone, a synthetic androgen, produced similar results. The stimulatory effect was blocked by anti-androgens. Seven patients with partial androgen insensitivity, of whom four were either receptor deficient or showed a qualitative defect in androgen binding, had reduced mibolerone induced stimulation of aromatase activity. All ten patients with receptor negative complete androgen insensitivity had an absent response. There was no aromatase induction in a further three patients with complete androgen insensitivity who were receptor positive. Two siblings in the latter group had an exon deletion encoding for part of the DNA binding domain of the androgen receptor. CONCLUSIONS: Androgens stimulate aromatase activity in genital skin fibroblasts from normals. The response is mediated via the androgen receptor and can be decreased or absent in patients with the androgen insensitivity syndrome. This may be a useful in-vitro marker of androgen responsiveness in such patients.  相似文献   
994.
In 41 patients with recurrent sustained ventricular tachycardia and/or ventricular fibrillation an integrated pacemaker-defibrillator-system (PCD, Medtronic, model 7216 A or 7217 B) was implanted. In 21 out of 24 (88%) patients a new transvenous implantation technique in combination with a subcutaneous patch electrode was used. The implanted devices comprise antibradycardiac pacemaker functions, two different forms of antitachycardiac pacemaker functions (ramp and burst pacing), and internal cardioversion or defibrillation capabilities. During a mean follow-up of 8 months 147 episodes of ventricular tachycardia were detected, 131 of them were terminated successfully by antitachycardiac pacing; in 13 episodes internal cardioversion was applied to revert ventricular tachycardia. Twenty-seven episodes of ventricular fibrillation or rapid ventricular tachycardia (greater than 200/min) were detected and successfully terminated by internal defibrillation. In six patients with intermittent rapid atrial fibrillation, change of antiarrhythmic therapy was required to avoid activation of the device. The new integrated pacemaker-defibrillator systems improve therapy in patients with life-threatening tachyarrhythmias by reducing the number of internal cardioversions/defibrillations; the non-thoracotomy approach reduces the post operative risk.  相似文献   
995.
Ethanol account for a significant fraction of the energy intake of persons consuming even moderate amounts of alcohol. A recent study has shown that although alcohol does not reveal itself as a layer floating at the top of a drink, metabolically it behaves more like oil than sugar.  相似文献   
996.
This report describes the intracellular metabolism of 5-formyltetrahydrofolate into the various one-carbon substituted folate and polyglutamate pools in a human breast (MCF-7) and colon (HCT 116) carcinoma cell line. Metabolism into the one-carbon substituted pools was found to be time and dose dependent over a concentration range up to 50 microM. A 3-fold increase in total intracellular folate was noted over a 50-fold concentration range (1-50 microM) of 5-formyltetrahydrofolate tested in the colon cell line, while in the breast line, a 6-fold increase was detected over a 500-fold concentration range (0.1-50 microM). The level of 5, 10-methylenetetrahydrofolate, which was detectable only in the breast cell line, was found to increase by a factor of 10 (1.8 pmol/mg to 17.9 pmol/mg) over the concentration range studied. The majority of metabolism was into the 10-formyltetrahydrofolate and tetrahydrofolate pools in the breast cells and into the 5-methyltetrahydrofolate pool in the colon cells. Polyglutamation was also time and dose dependent, with a significant proportion of the total pool represented by the higher polyglutamate forms (Glu3-Glu5) after 24 h of continuous exposure to 5-formyl tetrahydrofolate. Pentaglutamate was the highest level noted in both cell lines. The intracellular half-life of the polyglutamate forms was inversely related to the length of the polyglutamate tail with half-lives of 71, 131, 143, 441, and 1167 min for the mono- through pentaglutamate, respectively. Finally, up to a 20:1 ratio of the biologically inactive (6R) isomer to active (6S) isomer of 5-formyltetrahydrofolate resulted in no effect on metabolism into the one-carbon substituted folate pools and only minimal decreases in metabolism to the polyglutamate forms. These studies suggest that prolonged exposure to even relatively low doses of 5-formyltetrahydrofolate may be optimal for intracellular metabolism to the most biologically relevant forms for ternary complex formation with thymidylate synthase and fluorodeoxyuradylate, since longer exposures result in a greater accumulation of the higher polyglutamates.  相似文献   
997.
The effect of localized hyperthermia on blood flow and cis-diamminedichloroplatinum(II) (CDDP) pharmacokinetics in 7,12-dimethylbenz[a]anthracene-induced mammary adenocarcinomas was studied. Blood flow was determined in rat tumors and normal tissue immediately and 1, 2, and 3 h after local hyperthermia treatment (43 degrees C, 1 h) as well as in unheated tumors of rats. The rate of blood flow in the tumor was increased 1.9 times at the end of treatment relative to control values and returned to the control values by 3 h after hyperthermia. Similarly, the rate of blood flow in the peripheral skin around the tumor immediately after hyperthermia was 2.2 times greater than that of unheated skin and returned to near normal values by 3 h after heating. Tumor-bearing rats received CDDP 1 h before, at the beginning of, at the end of, and 1 h after hyperthermia administration. The CDDP plasma concentration versus time profiles for rats did not vary statistically between treatment groups. Two h after CDDP administration, the mean tumor CDDP concentration of the rats which received drug at the beginning of hyperthermia was statistically greater (P less than 0.05) than tumor CDDP concentrations in rats which received drug at the end of heat treatment. The latter group was given CDDP when tumor blood flow was the greatest; however, mean tumor drug concentration was lowest of all the groups. The mean drug concentration in tumor tissues of rats which received drug 1 h after hyperthermia was comparable to rats which received drug at the beginning of hyperthermia. This suggests that drug delivery or uptake in tumors may be altered when local hyperthermia is administered concurrently or sequentially.  相似文献   
998.
To study micrometastasis at its earliest stages, the bacterial lacZ marker gene was introduced into human EJ Ha-ras-transformed BALB/c 3T3 cells (LZEJ), followed by their intravenous injection into nude mice. Lung micrometastases were easily identified by blue staining of lacZ-tagged cells minutes/hours after injection, permitting effective evaluation of establishment/clearance mechanisms of LZEJ cells. Different treatments were used to disable LZEJ cells (fixation, irradiation, or mitomycin C) to determine modulation of these processes--although unable to divide, these cells stain for lacZ expression for days after treatment. Fixation-killed cells generated large microfoci (> 13-15 cells/focus) with well-rounded morphologies while live, irradiated, or mitomycin-treated cells generated smaller, irregularly shaped foci (3-7 cells/focus). Fixed-cell foci were cleared more slowly from lungs than the other three classes, even when prefiltered to remove large aggregates. All foci of disabled cells were eventually cleared while a basal level of live-cell foci persisted. Co-injection of fixed and live cells (or preinjection of fixed cells, followed by live cells) resulted in complete clearance of live-cell microfoci; in contrast, preinjection of live cells (then injection of fixed cells) led to survival of live-cell micrometastases. Therefore, altered deformability and/or cell surface interactions of tumor cells modulate the effectiveness of host-clearing mechanisms in the lung and in some situations these altered cells facilitate clearance of live tumor cells that are normally tumor-progressing.  相似文献   
999.
The anticarcinogenic action of the garlic constituent diallyl sulfide (DAS), was examined in the hamster buccal pouch and forestomach. Groups of hamsters were topically treated, for up to 14 weeks, with a 0.5% solution of the buccal pouch and forestomach carcinogen 7,12-dimethylbenz[a]anthracene (DMBA). Prior to, during and after DMBA treatment, groups of hamsters were also treated, on alternate days, with a 1% solution of DAS. In addition to tumor formation, the induction of gamma-glutamyl transpeptidase (gamma GT) buccal pouch epithelial lesions served as an additional presumptive index of in vivo carcinogenesis/anticarcinogenesis. DAS resulted in a significant reduction in buccal pouch tumor frequency, buccal pouch tumor burden, buccal pouch gamma GT lesion frequency and forestomach tumor frequency. In a separate experiment, DAS also reduced the level of autoradiographically quantified unscheduled DNA repair synthesis (UDS) in pieces of hamster buccal pouch concurrently exposed in vitro to the potent buccal pouch carcinogen N-methyl-N-benzylnitrosamine (MBN). This study demonstrates that DAS is an effective anticarcinogenic agent in squamous mucosa of the hamster and suggests novel cost-effective strategies for the rapid identification of tissue-specific anticarcinogens and a quantitative assessment of their efficacy.  相似文献   
1000.
H Anholt  J Moan 《Cancer letters》1992,61(3):263-267
CaD2 mammary carcinomas transplanted into the feet of mice were treated with tetrasulfonated phthalocyanine (AlPcS4) and laser light at 680 nm. A light dose of 135 J/cm2 was either given as continuous radiation (15 min) or fractionated with 15 s exposure, 15 s darkness, 15 s exposure and so on for 30 min. The CaD2 tumors were found to respond better to a fractionated exposure than to the same energy given in one exposure. The reason for this is assumed to be a relocalization of the dye upon illumination, seen as a rapid decrease in fluorescence. When the laser light was turned off, the fluorescence returned to almost the initial value.  相似文献   
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