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   5969篇
  免费   384篇
  国内免费   30篇
耳鼻咽喉   62篇
儿科学   136篇
妇产科学   189篇
基础医学   706篇
口腔科学   236篇
临床医学   524篇
内科学   1310篇
皮肤病学   135篇
神经病学   293篇
特种医学   190篇
外国民族医学   4篇
外科学   992篇
综合类   105篇
现状与发展   2篇
一般理论   2篇
预防医学   310篇
眼科学   159篇
药学   649篇
中国医学   41篇
肿瘤学   338篇
  2023年   68篇
  2022年   193篇
  2021年   350篇
  2020年   219篇
  2019年   284篇
  2018年   369篇
  2017年   230篇
  2016年   226篇
  2015年   226篇
  2014年   263篇
  2013年   339篇
  2012年   469篇
  2011年   414篇
  2010年   254篇
  2009年   194篇
  2008年   280篇
  2007年   265篇
  2006年   238篇
  2005年   291篇
  2004年   216篇
  2003年   211篇
  2002年   174篇
  2001年   48篇
  2000年   31篇
  1999年   47篇
  1998年   35篇
  1997年   26篇
  1996年   29篇
  1995年   24篇
  1994年   14篇
  1993年   19篇
  1992年   24篇
  1991年   19篇
  1990年   16篇
  1989年   23篇
  1988年   21篇
  1987年   21篇
  1986年   21篇
  1985年   29篇
  1984年   14篇
  1983年   20篇
  1982年   10篇
  1981年   14篇
  1980年   15篇
  1979年   18篇
  1977年   10篇
  1976年   12篇
  1975年   13篇
  1974年   6篇
  1972年   8篇
排序方式: 共有6383条查询结果,搜索用时 250 毫秒
11.
12.
13.
We examined the cytotoxic potential of nine N-[2-substituted-2-(2-thienyl)ethyl] piperazinyl quinolone derivatives on human oral epithelial mouth carcinoma (KB) and human squamous carcinoma (A431) cell lines. Phototoxic properties of these compounds were also evaluated by mouse 3T3 fibroblast under ultraviolet-A (UVA) irradiation. The percent of cell viability was evaluated by MTT assay. Compound 6 having a 4-[2-(phenylmethoxyimino)-2-(2-thienyl)ethyl] group attached to N4 position of piperazine ring of enoxacin showed the highest cytotoxicity potential on both A431 and KB cell lines (IC50 of 3.11+/-0.52 and 4.91+/-1.94 microg/ml, respectively). While some of the other tested compounds exhibited clear phototoxic potential in 3T3 cell line, compound 6 showed only a minor potential of phototoxicity. These findings suggest the high potential of 4-[2-(phenylmethoxyimino)-2-(2-thienyl)ethyl] derivative of enoxacin as a cytotoxic compound with low potency of phototoxic reactions. The mentioned chemical was identified to be of special interest for further characterization.  相似文献   
14.
Our objective was to evaluate the effect of intravenous magnesium sulphate administration to patients with preterm labour on maternal serum and amniotic fluid IL-1beta, IL-6, IL-10 and TNFalpha concentrations. Thirty-six patients at 24-34 weeks of singleton gestation, who presented with contractions (> or = 8 in 60 min) had amniocentesis to rule out intrauterine infection. The patients received intravenous MgSO4 for tocolysis. Twenty-six patients had amniocentesis performed before initiation of MgSO4 (controls) while 10 others had the procedure during tocolytic therapy (study patients). Magnesium, IL-1beta, IL-6, TNFalpha and IL-10 concentrations were measured. Study and control groups were statistically compared using Student t test. Mean magnesium levels were significantly higher in the study group (P < 0.01). There were no significant differences between the cytokines levels in maternal serum and in amniotic fluid between the groups. Our results suggest that the mechanism of magnesium as a tocolytic agent may not be mediated via the examined cytokines.  相似文献   
15.
BACKGROUND: The deliberate use of ketoconazole to reduce the need for cyclosporine (CsA) is not new, but it is particularly relevant because of the high cost of CsA. Many studies have documented this benefit in renal and cardiac transplants, but this co-administration has not been reported in patients with nephrotic syndrome. METHODS: This retrospective study included 207 nephrotic patients who were steroid resistant, dependent or frequent relapsers and received CsA therapy. Among these patients 153 received daily ketoconazole therapy in a dose of 50 mg with concomitant decrease of one-third of the CsA dose while 54 patients received CsA alone. The majority of our cases were children (179 were below 18 years) and male to female ratio was 1.7:1. RESULTS: The great majority of the study population received the drugs for 1-2 years. Patients who received CsA and ketoconazole were comparable with those who received CsA alone regarding age, sex, duration of renal disease, renal pathology, severity of nephrotic syndrome, renal function, hepatic function and steroid response. Co-administration of ketoconazole significantly reduced mean doses of CsA by 37% after 1 month and 47% at 1 year with overall net cost savings of 37%. Hepatic functions remained within the normal range in both groups. Additionally, co-administration of ketoconazole significantly improved the response to CsA therapy, successful steroid withdrawal and decreased the frequency of renal impairment. CONCLUSIONS: Co-administration of keto with CsA in idiopathic nephrotic patients significantly reduces CsA costs and may improve its response.  相似文献   
16.
Khellin (CAS 82-02-0) and methoxsalen (CAS 298-81-7) were examined in male albino rats to evaluate their ability to modify serum lipoprotein cholesterol. Clinical chemistry parameters were also measured to obtain information indicative of possible drug toxicity. The drugs were evaluated in four-week double dose studies. After four weeks at 0.45 mg/100 mg b.wt. for khellin and 0.27 mg/100 g b.wt. for methoxsalen, per day, both drugs significantly lowered low density lipoprotein cholesterol, high density lipoprotein cholesterol and total cholesterol. Very low density lipoprotein cholesterol and triglycerides were not changed. No apparent toxicity was observed as clinical chemistry parameters and body weights were not different compared to control values. Similar results were observed with a lower dose of khellin (0.23 mg/100 g b.wt./d). A dose of 0.13 mg/100 g b.wt./d of methoxsalen had no observable effect in this study. Confirmation of the hypocholesterolemic activity of khellin and methoxsalen in this study enhances the therapeutic potential of these compounds against atherosclerosis.  相似文献   
17.
In a double-blind, crossover designation penile intracavernous prostaglandin E1 and papaverine hydrochloride were compared in regard to effectiveness and safety in 52 patients investigated and treated for sexual erectile dysfunction. In evidence of the reliable effectiveness, prostaglandin E1 (20 micrograms/ml.) induced significant positive erectile response in 42 of 52 patients (81%). This rate reached 100% with neurogenic, hyperprolactinemic and/or psychogenic impotence. However, with papaverine hydrochloride (30 mg./ml.) and exclusively in cases of vasculogenic (most probably arteriogenic) impotence, negative erectile response was revealed as absent erection in 6 of 52 patients (11.5%) and nonrigid tumescence in 13 (25%) versus 2 (3.8%) and 8 (15.4%), respectively, with prostaglandin E1. Moreover, with prostaglandin E1 the regional pain was tolerable and transient, and the positive erectile response was not attended by priapism even in patients who formerly had priapism with papaverine hydrochloride. However, presently with prostaglandin E1 the relatively higher cost and shorter expiration period would probably limit its diagnostic and therapeutic use in Egypt, and probably in other developing countries.  相似文献   
18.
Rapid eye movement (REM) sleep deprivation has previously been shown to interfere with normal learning and memory and to inhibit long-term potentiation (LTP) in vitro. Previous studies on REM sleep deprivation and LTP have relied on in vitro analysis in isolated brain slices taken from animals following several days of sleep deprivation. LTP in the hippocampus in situ may differ from LTP in vitro due to modulatory inputs from other brain regions, which are altered after REM sleep deprivation. Here, we examined LTP in unanesthetized, behaving animals on the first and second recovery days following REM sleep deprivation to determine if similar effects are seen in vivo as previously reported in vitro. We found that LTP was significantly impaired in REM sleep-deprived animals on the second recovery day but not the first recovery day. Our results extend previous findings by showing that REM sleep deprivation continues to affect hippocampal function for more than 24h following the end of deprivation. Our results also suggest the presence of a modulatory process not present in vitro. Our findings are not explained by stress during REM sleep deprivation because equivalent circulating corticosterone levels (an index of stress) were found during both REM sleep deprivation and control treatment.  相似文献   
19.
Involution of thyroid hyperplasia (induced by a low iodine diet and a goitrogen, propylthiouracil, PTU) was obtained in mice by administering a high or a moderate dose of iodide (HID or MID, respectively). In HID involuting glands, vasoconstriction was observed after 12 hr whereas necrosis and inflammation were very abundant as early as after 6 hr and maximal after 48 hr. They were not prevented by papaverine by which vasoconstriction was inhibited, but were inhibited by the continuation of PTU by which iodide oxidation and organification were inhibited. Lipofuscin inclusions in thyroid and inflammatory cells were always associated with necrosis. On the contrary, when involution was induced by MID or by HID + triiodothyronine (T3), or by T3 alone, neither necrosis nor inflammation occurred and apoptosis was the only mode of cell deletion. No lipofuscin inclusion occurred. Our results demonstrate that iodide in excess, after being oxidized or organified, is directly toxic for iodine-deficient thyroid cells. The presence of lipofuscin suggests that its toxicity is mediated by lipid peroxidation, a consequence of production of free radicals in excess.  相似文献   
20.
Conventional tube cell culture has been recognised as the most sensitive technique available for human cytomegalovirus (HCMV) detection. Low-speed centrifugation of specimen inocula onto cell culture monolayers has been shown to increase the efficiency of infection with the AD 169 strain of HCMV. Therefore a centrifugal force of 900g for 1 hour at 37 degrees C was used to enhance the detection of HCMV cytopathic effect (CPE) in shell vials that contained circular coverslips with a monolayer of human embryonic lung (HEL) fibroblasts. Of 195 specimens, HCMV CPE was detected in 18 specimens (9.02%) on shell vial culture assay, whereas conventional tube cell culture was positive in only 13 specimens (6.6%). The shell vial culture assay was significantly more sensitive (P less than 0.05). Furthermore the development of the cytopathic effect on shell vial culture assay was significantly earlier (P less than 0.01) and more extensive. Urine samples were sonicated and the results obtained with immunofluorescence using human immune serum demonstrated that sonication increased both the intensity of fluorescence and number of fluorescent foci of HCMV-infected cells and also decreased the non-specific fluorescence of the background.  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