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   6325篇
  免费   494篇
  国内免费   14篇
耳鼻咽喉   33篇
儿科学   211篇
妇产科学   192篇
基础医学   731篇
口腔科学   73篇
临床医学   693篇
内科学   1512篇
皮肤病学   85篇
神经病学   620篇
特种医学   115篇
外国民族医学   1篇
外科学   669篇
综合类   72篇
一般理论   9篇
预防医学   747篇
眼科学   36篇
药学   403篇
中国医学   9篇
肿瘤学   622篇
  2023年   59篇
  2022年   84篇
  2021年   174篇
  2020年   108篇
  2019年   171篇
  2018年   199篇
  2017年   119篇
  2016年   130篇
  2015年   154篇
  2014年   229篇
  2013年   297篇
  2012年   487篇
  2011年   481篇
  2010年   249篇
  2009年   219篇
  2008年   302篇
  2007年   364篇
  2006年   340篇
  2005年   294篇
  2004年   260篇
  2003年   225篇
  2002年   204篇
  2001年   122篇
  2000年   139篇
  1999年   121篇
  1998年   47篇
  1997年   33篇
  1996年   39篇
  1995年   32篇
  1992年   80篇
  1991年   83篇
  1990年   63篇
  1989年   57篇
  1988年   63篇
  1987年   47篇
  1986年   45篇
  1985年   33篇
  1984年   48篇
  1980年   32篇
  1979年   26篇
  1978年   39篇
  1974年   44篇
  1973年   30篇
  1972年   31篇
  1971年   27篇
  1970年   49篇
  1969年   34篇
  1968年   38篇
  1967年   32篇
  1966年   35篇
排序方式: 共有6833条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Although there are well-established clinical human milk banks in the United States, there are no milk banks specifically intended to foster research on human milk. The authors' goal was to establish a milk bank with a core data set to support exploratory and hypothesis-driven studies on human milk. Donations to the Cincinnati Children's Research Human Milk Bank are accepted within the context of ongoing, hypothesis-driven research or on an ad hoc basis. Donors must give informed consent, and scientists wishing to use the samples must have Institutional review board approval for their use. Development of more research human milk banks can potentially provide resources for multidisciplinary collaboration and advance the study of human milk and lactation.  相似文献   
5.
R Van  C C Wun  A L Morrow  L K Pickering 《JAMA》1991,265(14):1840-1844
Fecal coliform contamination of environmental surfaces and hands in the day-care center is common. This study evaluated the effect of two diaper types on fecal contamination. Ten rooms in four day-care centers containing 141 children were studied in a prospective, randomized, crossover study. A total of 2946 samples were cultured during the 9-week study. Fecal coliforms were isolated from 307 inanimate objects (15%), 73 toy balls (46%), and 131 hands (17%). The number of contaminated inanimate objects was significantly less in rooms where paper diapers were worn when compared with that in rooms where double cloth diapers with plastic overpants were worn and in rooms where clothes were worn over diapers. Inanimate object cultures had more contamination in rooms in which diarrhea had occurred. Containment of feces by overclothes and diaper type may be important in decreasing transmission of enteric pathogens in day-care environments.  相似文献   
6.
Previously reported attenuation of skin postural vasoconstriction in women during the luteal menstrual cycle phase may be due to a progesterone-mediated decrease in myogenic or veno-arteriolar (VAR) mechanisms. Skin perfusion was measured in the shin and foot dorsum by Laser Doppler Fluxometry during leg dependency that increased vascular transmural pressure below (myogenic constriction only) and above (myogenic and VAR) the 25 mmHg threshold for activation of the VAR, and during venous distension to activate the VAR alone (cuff inflation to 50 mmHg). In six young women with normal menstrual cycles, vasoconstrictor responses to all interventions did not differ between days 7–13 (follicular) and 18–23 (luteal) of the normal menstrual cycle when progesterone levels were low and at their peak respectively. In eight women taking combined oral contraceptives (OC) and tested during pill consumption days, reductions in foot skin perfusion were smaller (P = 0.05) than in the luteal phase of the normal cycle for leg dependency below (−36.9 ± 5.2% OC vs. −52.5 ± 7.8% luteal, mean ± S.E.M.) and above (−43.7 ± 3.4% OC vs. −55.1 ± 4.8% luteal) the VAR threshold, and for venous distension (−53.1 ± 2.6% OC vs. 66.4 ± 5.5% luteal). In women with normal menstrual cycles, impaired postural vasoconstriction may be confined to those who experience pre-menstrual symptoms rather than a direct effect of endogenous hormones. Reduced vasoconstriction in the dependent foot during OC use is consistent with the known vasodilator action of exogenous hormones and its long-term effects  相似文献   
7.
Nineteen patients with ovarian cancer and minimal residual or persistent disease who were treated with cisplatin or carboplatin-based intraperitoneal (IP) regimens had distribution studies of IP contrast and computerized tomography prior to and during treatment. The distribution pattern was assessed retrospectively and scored for the presence of contrast in each of eight regions: the under surface of right and left diaphragms, the right and left paracolic gutters, the lesser omental sac, the intramesenteric region and the true and false pelvis. Assigning a point to each region with adequate distribution, we classified 10 patients to an excellent pattern (greater than or equal to 7 of 8 regions), 6 to a good pattern (5 to less than 7 regions), and 3 to an inadequate distribution pattern (less than 5 regions). Serial studies were performed in 8 patients after more than 4 cycles of IP therapy. In these patients, all of whom were tolerating treatment without progression, the distribution remained virtually unchanged for those with excellent distribution. One of three with good distribution manifested inadequate distribution on repeat study, and one of two with inadequate distribution improved to show a good pattern. In this small study there was no correlation of distribution patterns with plasma CA-125 at onset of IP treatment and prior surgical procedures or placement of the catheter tip. However, three patients with unsatisfactory patterns had procedures consisting of catheter placement only rather than formal reassessment laparotomies for ovarian cancer. Since satisfactory IP distribution may be required for obtaining a therapeutic advantage from IP therapy, methods for its assessment must be developed.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
8.
Avasimibe is a novel orally bioavailable ACAT inhibitor, currently under clinical development (phase III trials). It was safe when administered to rats, dogs, and humans. In vitro studies in human macrophages demonstrated that avasimibe reduces foam cell formation not only by enhancing free cholesterol efflux, but also by inhibiting the uptake of modified LDL. The concentration‐dependent reduction in cellular cholesteryl ester content in these cells was not accompanied by an increase in intracellular free cholesterol, which is in agreement with a good safety profile for avasimibe. In the liver, avasimibe caused a significant reduction in the secretion of apo B and apo B‐containing lipoproteins into plasma. Avasimibe induced cholesterol 7α‐hydroxylase and increased bile acid synthesis in cultured rat hepatocytes, and its administration to rats did not produce an increase in lithogenicity index of the bile. The hypolipidemic efficacy of the compound was demonstrated in cholesterol‐fed as well as in non‐cholesterol‐fed animals. In these models, plasma cholesterol levels were reduced, mainly due to the decrease in the non‐HDL cholesterol fraction. Clinical data are scarce, but in a study performed in 130 men and women with combined hyperlipidemia and hypoalphalipoproteinemia, avasimibe, 50–500 mg/day, significantly reduced plasma total triglyceride and VLDL‐cholesterol. Although total cholesterol, LDL‐cholesterol, and HDL‐cholesterol were unchanged, it must be stressed that animal data suggest that avasimibe may have direct antiatherosclerotic activity in addition to its cholesterol‐lowering effect. Avasimibe treatment can also contribute to increase plaque stability, as it reduces the accumulation of lipids in the arterial wall, inhibits macrophage infiltration into the media and reduces matrix metalloproteinase expression and activity. Moreover, avasimibe and statins have been shown to have synergistic effects, and the combination therapy may not only inhibit atherosclerotic lesion progression but also induce lesion regression, independently of changes in plasma cholesterol.  相似文献   
9.
10.
To establish a reference range, we measured intact parathyrin (parathyroid hormone, PTH) in 245 healthy postmenopausal women, ages 42-75 years, with use of the Allegro Intact PTH Kit from Nichols Institute Diagnostics. We also assayed serum from a subset of 120 of the women with kits specific for mid-molecule PTH. The mean intact PTH concentration for the 245 women was 32 ng/L (95% confidence interval 14-60 ng/L). Intact PTH values in these subjects were not normally distributed, although calcium concentrations in the same samples were. There was positive, but not significant (r = 0.12, P = 0.06), correlation between intact PTH and age, and a significant negative correlation between serum calcium and intact PTH that was not observed between calcium and mid-molecule PTH. The improved sensitivity of the intact PTH assay makes it useful in studies of calcium homeostasis in the normal population.  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