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   3095篇
  免费   320篇
  国内免费   20篇
耳鼻咽喉   14篇
儿科学   127篇
妇产科学   122篇
基础医学   411篇
口腔科学   34篇
临床医学   265篇
内科学   619篇
皮肤病学   30篇
神经病学   252篇
特种医学   117篇
外科学   440篇
综合类   129篇
一般理论   3篇
预防医学   345篇
眼科学   86篇
药学   231篇
  1篇
中国医学   4篇
肿瘤学   205篇
  2021年   36篇
  2020年   20篇
  2019年   44篇
  2018年   42篇
  2017年   50篇
  2016年   39篇
  2015年   49篇
  2014年   60篇
  2013年   94篇
  2012年   145篇
  2011年   110篇
  2010年   82篇
  2009年   93篇
  2008年   120篇
  2007年   100篇
  2006年   123篇
  2005年   97篇
  2004年   92篇
  2003年   110篇
  2002年   96篇
  2001年   105篇
  2000年   87篇
  1999年   93篇
  1998年   61篇
  1997年   56篇
  1996年   50篇
  1995年   47篇
  1994年   44篇
  1993年   48篇
  1992年   90篇
  1991年   77篇
  1990年   69篇
  1989年   71篇
  1988年   74篇
  1987年   77篇
  1986年   82篇
  1985年   65篇
  1984年   45篇
  1983年   45篇
  1982年   32篇
  1981年   40篇
  1979年   41篇
  1978年   37篇
  1977年   31篇
  1976年   22篇
  1974年   26篇
  1973年   32篇
  1971年   24篇
  1969年   22篇
  1967年   27篇
排序方式: 共有3435条查询结果,搜索用时 0 毫秒
41.
Although it has been demonstrated that a combination of mifepristoneand a prostaglandin is an effective method of inducing abortionin early pregnancy, the optimum dose of the antigestogen isunknown. Women (n = 220) requesting abortion in early pregnancy(63 days amenorrhoea) were randomized to receive a single doseof either 600 or 200 mg mifepristone followed 48 h later bya single dose of 600 µg misoprostol by mouth. The percentageof women who had a complete abortion (93.6% confidence interval90.4–95.5%) was identical in the two groups. There wasno significant difference in the number of women who passedthe fetus within 4 h of receiving the prostaglandin (64 versus74%), the days of bleeding (14.6 ± 1.1 versus 15.3 ±0.9) nor in the onset of the next period (39.7 ± 1.3versus 36.7 ± 1.3) respectively between the groups receiving200 or 600 mg mifepristone. However, the complete abortion ratewas significantly higher in women 49 days compared to women50–63 days amenorrhoea (97.5 versus 89.1% respectively;P < 0.02). There was no difference in any of the other parametersat different weeks of gestation. We conclude: (i) that the recommendeddose of mifepristone could be reduced from 600 to 200 mg withoutloss of clinical efficacy, (ii) that the combination of mifepristoneand 600 µg misoprostol is a highly effective alternativeto vacuum aspiration for inducing abortion in women < 50days amenorrhoea and (iii) at gestation >56 days, this combinationmay result in too many incomplete abortions to be clinicallyacceptable.  相似文献   
42.
An investigation of the effects on follicular development of clomiphene citrate and its two isomers En clomiphene and Zu clomiphene given separately was carried out on 19 normally cycling women being treated with donor insemination. All women received clomiphene citrate in the first cycle and, following a washout control cycle, were treated with either En clomiphene or Zu clomiphene alone. The number of follicles present, follicular phase oestrogen secretion and luteal phase pregnanediol excretion were not significantly different when Zu clomiphene cycles were compared with control cycles, but were significantly increased in En clomiphene and clomiphene citrate cycles. It is concluded that the En isomer, which has largely antioestrogenic properties, is the isomer active in inducing follicular development. The oestrogenic properties of Zu isomer did not appear to protect it from the possibly detrimental effects on sperm-cervical mucus interaction observed in both isomers and in the combined preparation.  相似文献   
43.
Human lymphocytes derived from a lymph node draining a primary breast adenocarcinoma were fused with the mouse myeloma P3X63Ag8.653 to generate human-mouse hybridomas secreting human monoclonal antibodies (MAbs) to tumor associated antigens (TAAs). One of the resulting human MAbs, YBB 190 (IgM) is described. Enzyme-linked immunosorbent assays (ELISA) employing membrane and cytosol fractions of human tissues demonstrated YBB 190 reactivity against cytosol but not membrane components of malignant and normal epithelial tissues. When tested by an indirect immunoperoxidase staining method against fresh frozen human tissue sections, YBB 190 reacted with malignant cells in 26 of 28 epithelial cancers and with normal epithelia in 11 different benign tissues. Preliminary western blot antigen characterization indicated that YBB 190 recognizes cytokeratin intermediate filaments, or a protein that is closely associated with cytokeratins. These data indicate that B cells with specificity for intermediate filaments are present in tumor draining lymph nodes. Our findings provide insights into the nature of potential autoimmune responses in cancer patients and suggest that improved tumor directed sensitization procedures may be required to more effectively utilize lymphocytes from tumor draining lymph nodes to generate therapeutically useful human MAbs to TAAs.  相似文献   
44.
45.
A number of procedures or interventions which activate electrogenic ion transport in mammalian intestine are reviewed. Using in vitro models it is possible to demonstrate direct or indirect pathways to stimulate chloride secretion. Such activation, in vivo, would change the gut from a state of net water absorption to one of fluid secretion. The movement of water is driven by electrical and osmotic gradients set up as a consequence of opening regulated ion channels in epithelial cells. Secretagogues may govern epithelial intracellular second messenger pathways to regulate ion channel activity directly or by activation of membrane bound receptors on the surface of epithelial cells. In health or disease secretagogues may be derived from cells within the attendant lamina propria of the intestinal mucosa. Pharmacological techniques may be employed to determine which mediators contribute to indirect stimulation of electrogenic ion transport by activation of neurons or of immunocytes (mast cells or phagocytes). Dissection and reconstruction of models of intestinal hypersensitivity reactions show that neuro-immune networks which regulate intestinal ion transport appear to be complex, functionally integrated systems. Analysis of such interactions may identify cellular or humoral targets with which to examine novel diagnostic, preventative or therapeutic strategies with regard to intestinal diseases.  相似文献   
46.
The safety and efficacy of controlled-delivery (CD) once-a-day formulation of diltiazem administered in the evening, at a dose of 240 mg, was assessed in 37 patients with stable angina pectoris. A double-blind, placebo-controlled, randomized, crossover protocol was used. Following a 4-day washout period, patients entered a 5--7-day single-blind placebo run-in period during which qualification and reproducibility exercise treadmill tests (ETTs) were performed 24 h postdose. Eligible patients were randomized in a double-blind fashion, to either CD diltiazem or to placebo for a 7--10-day treatment period. They then entered a 5--7-day single-blind washout period, after which they received the alternate treatment for another 7 to 10 days. ETTs were performed at the end of each treatment period. Compared to placebo, evening administration of CD diltiazem produced a marked improvement of the time to ETT termination, time to onset of angina, and time to 1 mm ST depression. In addition, the number of angina attacks recorded in patient diaries was reduced compared to placebo. Incidence of adverse events was comparable with CD diltiazem and placebo. We conclude that evening administration of controlled-delivery diltiazem is highly effective and safe in the treatment of stable angina pectoris.  相似文献   
47.
The need to locate distributed resources such as mates, food, and nests is correlated with an enlarged hippocampus in many mammalian and avian species. This correlation is believed to be a consequence of selection for spatial ability. Little is known about how such ecological needs affect non-mammalian, non-avian species. In lizards, the putative hippocampal homologues are the dorsal cortex (DC) and medial cortex (MC). We examined the relationship between foraging ecology and the size of the DC and MC in congeneric male lizards. We predicted based on the mammalian and avian literature that Acanthodactylus boskianus, an active forager that captures clumped, immobile prey would have a larger MC and DC than A. scutellatus, a sit-and-wait predator, that captures mobile prey. Our previous behavioral studies showed that A. boskianus did not differ from A. scutellatus on a spatial task but that A. boskianus was significantly better at the reversal of a visual discrimination, another task that is hippocampally dependent in mammals. In the current study, we found that, relative to telencephalon volume, the MC and DC were larger in the active forager whereas a control region, the lateral, olfactory, cortex, was similar in size between species. The current anatomical results suggest that MC and DC size is related to active foraging in lizards and, along with our previous behavioral studies, show that it is possible for this relationship to occur in the absence of evidence for species differences in spatial memory. Copyright (R) 2000 S.Karger AG, Basel  相似文献   
48.
49.
We report a case of Crohn's disease with involvement of the foreskin in a 12-year-old boy. One year previously, on the basis of clinical features (diarrhea with blood, perianal fissures) and histologic examination, a diagnosis of Crohn's disease was made. Subsequently, he developed phimosis and balanitis and underwent circumcision. Sections submitted from the foreskin revealed noncaseating granulomatous inflammation consistent with Crohn's disease. Crohn's disease with involvement of the genitalia is unusual. Only 26 cases including our case have been reported in the scientific literature. We have analyzed these cases with emphasis on gender, age, clinical features, duration of Crohn's disease, and probable mode of spread to the genitalia. Careful examination of sections from genital lesions, including those submitted from the foreskin, is essential to detect small isolated granulomas that may then lead to the diagnosis of inflammatory bowel disease.  相似文献   
50.
Abstract: We report the first case of fatal anthrax meningoencephalitis in Hong Kong over the past 60 years. A 13 year-old boy presented with right lower quadrant pain, diarrhoea and progressive headache. Lumbar puncture yielded gram positive bacilli initially thought to be Bacillus cereus, a contaminant. He was treated with ampicillin and cefotaxime, but died 3 days after hospitalization. The organism isolated from blood and cerebrospinal fluid was later identified as Bacillus anthracis.  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