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   14130篇
  免费   1004篇
  国内免费   54篇
耳鼻咽喉   178篇
儿科学   390篇
妇产科学   262篇
基础医学   2267篇
口腔科学   173篇
临床医学   1376篇
内科学   2606篇
皮肤病学   426篇
神经病学   1432篇
特种医学   719篇
外科学   1725篇
综合类   76篇
一般理论   8篇
预防医学   1193篇
眼科学   311篇
药学   892篇
中国医学   26篇
肿瘤学   1128篇
  2024年   14篇
  2023年   148篇
  2022年   234篇
  2021年   515篇
  2020年   329篇
  2019年   515篇
  2018年   527篇
  2017年   413篇
  2016年   413篇
  2015年   479篇
  2014年   585篇
  2013年   718篇
  2012年   1129篇
  2011年   1178篇
  2010年   601篇
  2009年   575篇
  2008年   912篇
  2007年   860篇
  2006年   831篇
  2005年   751篇
  2004年   728篇
  2003年   673篇
  2002年   552篇
  2001年   94篇
  2000年   67篇
  1999年   113篇
  1998年   124篇
  1997年   105篇
  1996年   78篇
  1995年   69篇
  1994年   53篇
  1993年   50篇
  1992年   58篇
  1991年   39篇
  1990年   42篇
  1989年   37篇
  1988年   35篇
  1987年   31篇
  1986年   32篇
  1985年   34篇
  1984年   37篇
  1983年   36篇
  1982年   36篇
  1981年   26篇
  1980年   30篇
  1979年   18篇
  1978年   22篇
  1977年   25篇
  1974年   13篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
101.
102.
Summary A formula relating oncotic pressure torat serum protein concentration was derived and found to be in complete agreement with the Landis-Pappenheimer formula derived from measurements onhuman plasma.This study was supported by the Danish Medical Research Council and Johan and Hanne Weimann's legacy.  相似文献   
103.
We study the emergence and dynamics of competing strains of digital organisms in a world with two depletable resources. Consumption of one resource produces the other resource as a by-product, and vice versa. As a consequence, two types of mutually dependent organisms emerge that each prey on the waste product of the other. In the absence of mutations, that is, in a purely ecological setting, the abundances of the two types of organisms display a wide range of different types of oscillations, from regular oscillations with large amplitude to irregular oscillations with amplitudes ranging from small to large. In this regime, time-averaged abundance levels seem to be controlled by the relative fitness of the organisms in the absence of resources. Under mutational pressure, on the other hand, populations evolve that seem to avoid the oscillations of intermediate to large amplitudes. In this case, the relative fitness of the organisms in the presence of resources plays an important role in the time-averaged abundance levels as well.  相似文献   
104.
BACKGROUND: Mizolastine is a nonsedating H1 histamine receptor antagonist with additional antiallergic properties currently marketed in Europe for the treatment of seasonal and perennial allergic rhinitis (PAR) and urticaria. OBJECTIVE: This multicenter, randomized, double-blind, parallel-group study was conducted to evaluate the efficacy and safety of mizolastine in PAR compared with loratadine and placebo. METHODS: After a 1-week placebo run-in period, 428 adult PAR patients received placebo (146 of 428), mizolastine 10 mg (141 of 428), or loratadine 10 mg (141 of 428) once daily for 28 days. Symptoms were evaluated by patients and physicians using a total nasal score, evaluating itching, rhinorrhea, nasal blockade, and sneezing severity. RESULTS: Mizolastine treatment resulted in a significantly greater decrease in patient-rated total nasal score than placebo after 2 weeks (D14; -42%, P < 0.001) and at the end of the treatment period (-46%, P = 0.01), and significantly greater than that observed with loratadine at D14 (P = 0.031). No significant difference in change in total nasal score was observed between loratadine and placebo at 2- and 4-week visits. The global safety was satisfactory and the incidence of adverse events was similar in the three treatment groups. CONCLUSIONS: Mizolastine provides effective symptom relief in PAR together with a satisfactory safety profile. Improvement with mizolastine was significantly greater than placebo throughout the study despite a large placebo effect. Also mizolastine's effects were greater those observed with loratadine after 2 weeks of treatment.  相似文献   
105.
Sepsis caused by gram-positive bacteria lacking lipopolysaccharide (LPS) has become a major and increasing cause of mortality in intensive-care units. We have recently demonstrated that the gram-positive-specific bacterial cell wall component lipoteichoic acid (LTA) stimulates the release of the proinflammatory cytokines in Kupffer cells in culture. In the present study, we have started to assess the signal transduction events by which LTA induces the production of tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and the anti-inflammatory cytokine IL-10 in rat Kupffer cells. LTA was found to trigger phosphorylation of mitogen-activated protein kinases (MAPK) (p38 MAPK and ERK 1/2) and protein kinase B (PKB). Compared to LPS, LTA was more potent in inducing PKB phosphorylation after 40 min, although we found that the cytokine responses were similar. For both bacterial molecules, blocking phosphatidylinositol 3-kinase (PI3-K; Ly294002) or Janus kinase 2 (JAK-2; AG490) particularly affected the induction of IL-6 and IL-10 release, whereas TNF-alpha levels were strongly reduced by inhibition of Src family tyrosine kinases (PP2). All three cytokines were reduced by inhibition of p38 MAPK (SB202190) or the broad-range tyrosine kinase inhibitor genistein, whereas IL-6 release was particularly blocked by inhibition of ERK 1/2 (PD98059). Divergences in the regulatory pathways controlling TNF-alpha, IL-10, and IL-6 production in Kupffer cells following LPS or LTA stimulation may create a basis for understanding how the balance between pro- and anti-inflammatory cytokines is regulated in the liver following infections by gram-positive or gram-negative bacteria.  相似文献   
106.
Anti-apolipoprotein A-1 (Apo A-1) autoantibodies were described in autoimmune disorders such as systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS) and might be involved in the genesis of arterial and venous thrombotic events. To investigate the presence of these autoantibodies in patients with acute coronary syndrome (ACS) without other features of autoimmunity, we set up an enzyme-linked immunosorbent assay (ELISA) for anti-Apo A-1 antibodies. We used it to investigate their prevalence in ACS as compared to SLE and APS and correlated them to plasma Apo A-1 and serum amyloid A protein (SAA) concentrations. The prevalence of anti-Apo A-1 autoantibodies in the healthy control group was 1% (1/92), but was significantly higher in other groups: 21% (11/53) in ACS group (P=0.001), 13% (12/92) in SLE and/or APS group (P=0.005). Multiple linear regression revealed a significant correlation between plasma Apo A-1 (r=-0.72, P=0.013), plasma SAA concentration (r=0.76, P=0.0066) and anti-Apo A-1 IgG titre in ACS patients. The presence of anti-Apo A-1 autoantibodies in patients with ACS highlights an additional link between autoimmunity, inflammation and atherosclerosis.  相似文献   
107.
There is ongoing debate whether the efficiency of local cognitive processes leads to global cognitive ability or whether global ability feeds the efficiency of basic processes. A prominent example is the well-replicated association between inspection time (IT), a measure of perceptual discrimination speed, and intelligence (IQ), where it is not known whether increased speed is a cause or consequence of high IQ. We investigated the direction of causation between IT and IQ in 2012 genetically related subjects from Australia and The Netherlands. Models in which the reliable variance of each observed variable was specified as a latent trait showed IT correlations of -0.44 and -0.33 with respective Performance and Verbal IQ; heritabilities were 57% (IT), 83% (PIQ) and 77% (VIQ). Directional causation models provided poor fits to the data, with covariation best explained by pleiotropic genes (influencing variation in both IT and IQ). This finding of a common genetic factor provides a better target for identifying genes involved in cognition than genes which are unique to specific traits.  相似文献   
108.
109.
110.
The study of a series of molecularly uniform poly(N-alkylurethanes) with a systematically varied and tailored chain architecture has shown that the packing and superstructure can be controlled by the primary structure of the urethane chain and reversibly altered by the sample treatment, respectively. Depending on the conformation or the stereogeometry of the constitutive unit built in the middle of the otherwise symmetrical oligourethane, chain-extended and/or chain-folded crystallization of the urethane chain can occur. The packing order, i. e., adjacent recentry chain-folding or chain-extended crystallization, and the thermal properties of the oligourethanes are related to the chemical structure of the central constitutive unit.  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