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   3721篇
  免费   194篇
  国内免费   32篇
耳鼻咽喉   43篇
儿科学   39篇
妇产科学   38篇
基础医学   496篇
口腔科学   41篇
临床医学   269篇
内科学   744篇
皮肤病学   15篇
神经病学   465篇
特种医学   153篇
外科学   633篇
综合类   12篇
预防医学   104篇
眼科学   64篇
药学   297篇
中国医学   39篇
肿瘤学   495篇
  2023年   38篇
  2022年   84篇
  2021年   115篇
  2020年   55篇
  2019年   62篇
  2018年   85篇
  2017年   61篇
  2016年   79篇
  2015年   64篇
  2014年   78篇
  2013年   120篇
  2012年   202篇
  2011年   211篇
  2010年   134篇
  2009年   113篇
  2008年   140篇
  2007年   184篇
  2006年   145篇
  2005年   188篇
  2004年   157篇
  2003年   165篇
  2002年   149篇
  2001年   127篇
  2000年   117篇
  1999年   97篇
  1998年   49篇
  1997年   39篇
  1996年   46篇
  1995年   35篇
  1994年   34篇
  1993年   31篇
  1992年   51篇
  1991年   73篇
  1990年   72篇
  1989年   68篇
  1988年   57篇
  1987年   60篇
  1986年   60篇
  1985年   49篇
  1984年   45篇
  1983年   36篇
  1982年   15篇
  1981年   10篇
  1980年   12篇
  1979年   22篇
  1978年   11篇
  1976年   10篇
  1973年   14篇
  1970年   10篇
  1969年   10篇
排序方式: 共有3947条查询结果,搜索用时 15 毫秒
71.
72.
73.
In this study, we theoretically investigate the aromatic and open-shell characteristics of carbon nanobelts (CNBs) composed of five- and six-membered rings. We have designed nanobelts composed of indeno[1,2-b]fluorene ([1,2-b]IF) units, which are referred to as [N]IF-CNB (N: the number of five-membered rings). The number of π-electrons, nπ, in neutral [N]IF-CNB is 7N, and thus depending on N and charge states, nπ can be 4n + 2 and 4n. Quantum chemical calculations on neutral [6]IF-CNB and [8]IF-CNB and dicationic [8]IF-CNB2+ have revealed that they are expected to exhibit unique aromatic and open-shell characteristics depending on nπ, there are several analogies of the electronic structures in [N]IF-CNB to those in [N]annulene. Delocalized and intermediate open-shell electronic structures of [N]IF-CNB are also useful to drastically change the third-order nonlinear optical properties. These results suggest that theoretically designed [N]IF-CNB can be attractive and challenging targets of organic synthesis for realizing novel open-shell functional conjugated macrocycles.

Dependence of aromatic and open-shell characteristics on the number of units and charged states was theoretically investigated for carbon nanobelts composed of indeno[1,2-b]fluorene units by using quantum chemical calculations.  相似文献   
74.
ObjectivesValganciclovir (VGCV) has been shown to improve sensorineural hearing loss (SNHL) and neurological outcomes in patients with neonatal symptomatic congenital cytomegalovirus (cCMV) infection. However, reports on the pharmacokinetics, efficacy and safety of oral VGCV are limited. The aim of this study is to evaluate the pharmacokinetics of VGCV for use in the treatment of cCMV.MethodsThis was a single-center, retrospective observational study conducted at Saitama Children's Medical Center in Japan between 2012 and 2017. CMV DNA copy number, maximum plasma VGCV concentration (Cmax), and adverse events (ADEs) during treatment were evaluated.ResultsA total of 26 patients with cCMV who received VGCV were included in this study. The median age at VGCV initiation was 9.5 months (range 0–46). Twenty-one patients (81%) had SNHL at baseline. Of these, five patients (19%) presented with improved SNHL, and none experienced worsened SNHL during treatment. The mean VGCV Cmax was 3.5 μg/mL (range 2–5.3), with no significant variation among individual values, and the values were maintained during treatment. Furthermore, there were no correlations between the Cmax values and age, sex, SNHL improvement or ADEs. Neutropenia (<1000/mm3) was observed in six patients (23%); however, no serious ADEs occurred.ConclusionsVGCV prevented the progression of SNHL without serious ADEs due to its stable pharmacokinetics. This study provides safety and tolerability of VGCV for the treatment of cCMV patients.  相似文献   
75.
76.
77.
So far, no combination of endocrine treatments has been routinely used in the therapy of breast Cancer. It was, therefore, our interest to determine whether the combination of the antiprogestin, onapristone (ON), and the pure antiestrogen, ICI 164384 (ICI), might provide a more effective therapy than either monotherapy in experimental mammary tumors containing both estrogen and progesterone receptors. In the MXT-mammary tumor of the mouse, ON (5 mg/kg) administered for 3 weeks exerted an ovariectomy-like antitumor effect (56% inhibition), whereas ICI (30 mg/kg) was weakly effective (28% inhibition). The combination of ON and ICI was, however, distinctly more effective than the monotherapies or ovariectomy, causing 78% inhibition. A similar potentation of antitumor effect by the combination was manifested in the dimethylbenzanthracene-induced mammary tumor of the rat when ON (5 mg/kg) and ICI (30 mg/kg) were administered once daily for 4 weeks (s.c.). The remission rates of tumors found after treatment with ICI, ON, the combination and ovariectomy (complete and partial remission) were 15%, 46%, 71% and 100% respectively. In the animals bearing DMBA-induced tumors, treatment with ON alone significantly increased the serum levels of luteinizing hormone and prolactin, but caused only a slight increase in the peripheral levels of estradiol and progesterone. ON had no appreciable effect on the uterine and ovarian weights. ICI reduced the uterine weight and the serum progesterone level. In the combination with ON, ICI reversed the effect of ON on the progesterone level without influencing the luteinizing harmone and prolactin levels. These findings suggest that the augmentation of antitumor effectiveness by the combination of two antihormones can be ascribed not only to their effects at estrogen- and progester-one-receptor-binding sites, but also to the decrease in the peripheral level of progesterone. Thus, an appropriate combination of antiprogestin and pure antiestrogen may be useful in the management of breast cancer.  相似文献   
78.
"Groove pancreatitis", a form of segmental pancreatitis affecting the head of the pancreas, is local-ized within the "groove" between pancreas head, duo-denum, and common bile duct. Differentiation between groove pancreatitis and pancreatic head carcinoma is often difficult. We report a case of groove pancreatitis in which a hypoechoic mass between the duodenal wall and pancreas was clearly imaged, and narrowing of the second portion of the duodenum and bile duct stenosis were also found. The diagnosis was confirmed by surgery (pylorus-preserving pancreato duodenectomy). The patient was relieved from abdominal pain post operation. Up to the present, the patient has been good condition. We review the clinicopathologic and radiologic features of groove pancreatitis in the Japanese literature and discuss the possible role of Santorini's duct in its pathogenesis. We consider that impacted protein plugs in Santorini's duct are a pathogenic factor in the development of groove pancreatitis. Therefore, the findings of Santorini's duct on endoscopic retrograde pancreatography are very important in the diagnosis of groove pancreatitis. Groove pancreatitis presents various clinical features, such as biliary stenosis, duodenal stenosis, and pancreatic mass, and often masquerades as pancreatic head carcinoma. This condition should be kept in mind in the differential diagnosis of pancreatic head carcinoma. (Received Apr. 17, 1997; accepted Sept. 26, 1997)  相似文献   
79.
80.
To increase our understanding of the effect of thiazolidinediones, a new class of antidiabetic drugs, on liver function as well as glycemic control, we investigated liver function before, during, and after treatment with troglitazone and pioglitazone. A total of 32 patients with type 2 diabetes were studied. Glycemic control and liver function were measured before, during, and after 4 to 12 weeks of treatment with troglitazone or pioglitazone. Glycemic control was assessed by fasting levels of plasma glucose, hemoglobin A 1c , and serum insulin, and liver function was assessed by asparatate aminotransferase (AST), alanine aminotransferase (ALT), and gamma -glutamyl transpeptidase ( gamma-GTP). Homeostasis model assessment for insulin resistance was used as an index of insulin resistance. During treatment with troglitazone, fasting plasma glucose and hemoglobin A 1c levels and homeostasis model assessment for insulin resistance were significantly decreased. Serum AST, ALT, and gamma-GTP levels were significantly decreased during treatment (AST, -17.4%; ALT, -27.2%; gamma-GTP, -47.9%) and returned to pretreatment levels after 4 weeks of withdrawal of the drug. A similar tendency was observed during treatment with pioglitazone (AST, -4.7%; ALT, -16.4%; gamma-GTP, -30.8%). These data suggest that, in contrast to the deterioration of liver function reported in a small subset of patients treated with troglitazone, treatment with thiazolidinediones was associated with a decrease in serum transaminases in most patients. The improvement in liver function parameters known to be associated with fatty liver in the present study, together with an improvement in fatty liver reported for another class of insulin sensitizers, biguanides, suggests that thiazolidinediones may have a beneficial effect on fatty liver.  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