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   12230篇
  免费   717篇
  国内免费   96篇
耳鼻咽喉   80篇
儿科学   181篇
妇产科学   105篇
基础医学   1716篇
口腔科学   294篇
临床医学   900篇
内科学   3401篇
皮肤病学   318篇
神经病学   537篇
特种医学   435篇
外科学   2089篇
综合类   51篇
预防医学   374篇
眼科学   154篇
药学   793篇
中国医学   46篇
肿瘤学   1569篇
  2023年   55篇
  2022年   115篇
  2021年   251篇
  2020年   108篇
  2019年   181篇
  2018年   218篇
  2017年   194篇
  2016年   255篇
  2015年   257篇
  2014年   321篇
  2013年   413篇
  2012年   696篇
  2011年   677篇
  2010年   391篇
  2009年   359篇
  2008年   639篇
  2007年   687篇
  2006年   694篇
  2005年   740篇
  2004年   715篇
  2003年   724篇
  2002年   630篇
  2001年   324篇
  2000年   349篇
  1999年   357篇
  1998年   183篇
  1997年   141篇
  1996年   152篇
  1995年   104篇
  1994年   87篇
  1993年   109篇
  1992年   209篇
  1991年   207篇
  1990年   202篇
  1989年   195篇
  1988年   163篇
  1987年   120篇
  1986年   102篇
  1985年   108篇
  1984年   87篇
  1983年   56篇
  1982年   35篇
  1981年   38篇
  1980年   27篇
  1979年   48篇
  1978年   27篇
  1977年   32篇
  1976年   31篇
  1969年   24篇
  1968年   25篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
3.

Background

Controversy continues as to whether single-incision laparoscopic cholecystectomy, with the somewhat larger incision at the umbilicus, may lead to a worse postoperative quality of life and more pain compared with the more classic 4-port laparoscopic cholecystectomy. The aim of this study was to compare single-incision and 4-port laparoscopic cholecystectomy from the perspective of quality of life.

Methods

This study was a multicenter, parallel-group, open-label, randomized clinical trial. A total of 120 patients who were scheduled to undergo elective cholecystectomy were randomly assigned 1:1 into the single-incision laparoscopic cholecystectomy or the 4-port laparoscopic cholecystectomy group and then assessed continuously for 2 weeks during the postoperative period. The primary outcome was quality of life, defined as the time to resume normal daily activities. Postoperative pain was also assessed. To explore the heterogeneity of treatment effects, we assessed the interactions of sex, age, and working status on recovery time.

Results

A total of 58 patients in the single-incision group and 53 in the 4-port group (n?=?111, 47 male, mean age 57 years) were analyzed. The mean time to resume daily activities was 10.2 days and 8.8 days, respectively, for single-incision and 4-port laparoscopic cholecystectomy (95% confidence interval –0.4 to 3.2, P?=?.12). Similarly, the time to relief from postoperative pain did not differ significantly between the groups. Statistically insignificant but qualitative interactions were noted; in the subgroups of women, full-time workers, and patients younger than 60 years, recovery tended to be slower after single-incision laparoscopic cholecystectomy.

Conclusion

Postoperative quality of life did not differ substantially between single-incision laparoscopic cholecystectomy and 4-port laparoscopic cholecystectomy. Patients younger than 60 years, women, and full-time workers tended to have a somewhat slower recovery after single-incision laparoscopic cholecystectomy.  相似文献   
4.
Angiotensin II receptor blockers (ARBs) are widely used for the treatment of hypertension. It is believed that treatment with an ARB increases the level of plasma angiotensin II (Ang II) because of a lack of negative feedback on renin activity. However, Ichikawa (Hypertens Res 2001; 24: 641-646) reported that long-term treatment of hypertensive patients with olmesartan resulted in a reduction in plasma Ang II level, though the mechanism was not determined. It has been reported that angiotensin 1-7 (Ang-(1-7)) potentiates the effect of bradykinin and acts as an angiotensin-converting enzyme (ACE) inhibitor. It is known that ACE2, which was discovered as a novel ACE-related carboxypeptidase in 2000, hydrolyzes Ang I to Ang-(1-9) and also Ang II to Ang-(1-7). It has recently been reported that olmesartan increases plasma Ang-(1-7) through an increase in ACE2 expression in rats with myocardial infarction. We hypothesized that over-expression of ACE2 may be related to a reduction in Ang II level and the cardioprotective effect of olmesartan. Administration of 0.5 mg/kg/day of olmesartan for 4 weeks to 12-week-old stroke-prone spontaneously hypertensive rats (SHRSP) significantly reduced blood pressure and left ventricular weight compared to those in SHRSP given a vehicle. Co-administration of olmesartan and (D-Ala7)-Ang-(1-7), a selective Ang-(1-7) antagonist, partially inhibited the effect of olmesartan on blood pressure and left ventricular weight. Interestingly, co-administration of (D-Ala7)-Ang-(1-7) with olmesartan significantly increased the plasma Ang II level (453.2+/-113.8 pg/ml) compared to olmesartan alone (144.9+/-27.0 pg/ml, p<0.05). Moreover, olmesartan significantly increased the cardiac ACE2 expression level compared to that in Wistar Kyoto rats and SHRSP treated with a vehicle. Olmesartan significantly improved cardiovascular remodeling and cardiac nitrite/ nitrate content, but co-administration of olmesartan and (D-Ala7)-Ang-(1-7) partially reversed this anti-remodeling effect and the increase in nitrite/nitrate. These findings suggest that olmesartan may exhibit an ACE inhibitory action in addition to an Ang II receptor blocking action, prevent an increase in Ang II level, and protect cardiovascular remodeling through an increase in cardiac nitric oxide production and endogenous Ang-(1-7) via over-expression of ACE2.  相似文献   
5.
Laparoscopic cholecystectomy and time-course changes in renal function   总被引:13,自引:3,他引:10  
Background: Recently, the retraction method has been used to reduce intraabdominal pressure (IAP) during laparoscopic surgery. The purpose of this study was to determine the serial changes in renal function during laparoscopic cholecystectomy (LC) using the retraction method. Methods: Urine output, effective renal plasma flow (ERPF), and glomerular filtration rate (GFR) were measured serially in seven patients who underwent LC with 12 mmHg pneumoperitoneum (High-IAP group) and five who underwent LC using the retraction method with 4 mmHg pneumoperitoneum (Low-IAP group). Results: Urine output, ERPF, and GFR were decreased during pneumoperitoneum in the High-IAP group, whereas no significant changes in any of these parameters were observed in the Low-IAP group. Conclusions: Our findings demonstrate that reduction of IAP to 4 mmHg using the retraction method prevents the transient renal dysfunction caused by prolonged 12 mmHg pneumoperitoneum during LC, suggesting that the retraction method reduces the risk of perioperative renal dysfunction during laparoscopic surgery. Received: 26 March 1996/Accepted: 27 July 1996  相似文献   
6.
CYP2E1 and ALDH2 Genotypes and Alcohol Dependence in Japanese   总被引:2,自引:0,他引:2  
The genotypes of the CYP2E1 and ALDH2 loci of alcoholic (alcohol dependence) and nonalcoholic (healthy) Japanese were investigated to examine the relationship between the polymorphism of CYP2E1 (C1/C2) and ALDH2 ( ALDH2*1/ALDH2*2 ), and the susceptibility to alcoholism. There was no significant difference in C2 gene frequency between alcoholics (0.19) and nonalcoholics (controls) (0.20), whereas there was a significant difference in ALDH2 allele frequency, suggesting that, in Japanese, the C2 genotype of CYP2E1 may have nothing to do with the risk of developing alcohol dependence. However, the ALDH2*1 allele may influence drinking behavior and the development of alcohol dependence. Furthermore, racial interethnic differences in the frequency of the mutated allele of the CYP2E1 gene (CJ were found, like the ALDH2 gene. Japanese healthy controls showed a significantly higher frequency of the C2 allele than did Swedish healthy controls (0.05; reported by Persson et al., FEBS Lett. 319:207-211,1993).  相似文献   
7.
Isolated ultrafiltration, hemodialysis & peritoneal dialysis (Tx) were recently used in the treatment of intractable heart failure (HF). We examined the relation between the response of HF to Tx and the residual kidney functions. Tx was carried out in 17 patients (Pts) with HF who did not respond to aggressive medical treatment. Ten Pts (R) responded to Tx and 7 Pts (N) did not. Serum urea nitrogen (UN), creatinine (Cr), uric acid (UA), sodium (Na), potassium (K), and chloride (Cl) concentrations on admission and before Tx were not different between R and N. Urine UN, Cr, Na, K, and Cl on admission and before Tx were also not significantly different. Fractional sodium excretions (FENa), renal failure indices (RFI), and urine/plasma Cr ratios (U/P Cr) on admission were 2.0 +/- 1.6, 2.7 +/- 2.2, and 30.5 +/- 20.0 in R and 5.9 +/- 4.2, 8.2 +/- 6.0 and 11.5 +/- 3.8 in N. They were significantly different (p less than 0.05). However, these did not differ before and after Tx. These data show that FENa, RFI and U/P Cr might be useful indices in predicting the responsiveness of intractable HF to Tx.  相似文献   
8.
9.
A 30-year-old woman was admitted to Mie University Hospital for recurrence of sudden visual field defect with photopsia in the right eye. She had experienced the same episodes at the age of 15, 20, 25 and 28 years old. A diagnosis of retrobulbar optic neuritis had been made at each episode, but corticosteroid therapy failed to resolve the symptoms. Neurologic examination on admission was unremarkable except for the visual field defect of the right eye. Brain MRIs with and without gadolinium enhancement were normal. On ophthalmologic examination, visual acuity was normal, but the Mariotte blind spot of the right eye was expanded. Ophthalmoscopic examination, visual evoked potential, flicker electro-oculogram and Hess test were normal. Multifocal electroretinogram (ERG) revealed reduction in the inferior temporal response of the right eye that corresponded to the expansion of the Mariotte blind spot These findings were consistent with conditions of acute zonal occult outer retinopathy (AZOOR). The visual symptoms of AZOOR thus resemble those of retrobulbar optic neuritis and findings of multifocal ERG were useful to differentiate them. AZOOR is a newly established condition, and it is necessary to pay more attention to AZOOR on the differential diagnoses of acute-onset mono ocular visual disturbances.  相似文献   
10.
The effects of methyl 2,6-dimethyl-4-(2-nitrophenyl)-5-(2-oxo-1,3,2-dioxaphosphorinan-2- yl)-1,4- dihydropyridine 3-carboxylate (DHP-218), a new dihydropyridine calcium antagonist, on vascular smooth muscles, cardiac muscles and [3H]-nitrendipine binding to the cardiac muscle and brain membranes were investigated in vitro. Vascular smooth muscles: Calcium-induced contraction of the rat aorta in high K+ solution was inhibited by DHP-218 with the pA2 value of 9.11. The IC50 value for the inhibitory effects of this compound in high K+-induced and phenylephrine-induced contraction was 6.3 nmol/l and 66 nmol/l, respectively. Vasodilatory effects of this drug on various blood vessels of rabbits contracted by high K+ appeared to a similar extent. The onset of the vasodilatory effect was very slow and the recovery rate of vasodilatory response after washout with the bathing solution containing high K+ or phenylephrine was also very slow. Cardiac muscles: Negative chronotropic and inotropic actions were observed at concentrations more than 30 and 100 nmol/l, respectively. Duration of the plateau phase of normal action potential was shortened and the amplitude and duration of slow action potential were reduced at concentrations more than 1 mumol/l. Very high vasculoselectivity was observed. Displacement of [3H]-nitrendipine binding: The pattern of displacement of [3H]-nitrendipine binding by DHP-218 was very similar to that of other 1,4-dihydropyridines but this compound was about 70 times less potent than nifedipine in [3H]-nitrendipine displacement capacity. These results indicate that DHP-218 has specific vasodilatory action due to calcium antagonism, but association and dissociation rates with tissue and receptors were different from those of nifedipine.  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