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   9829篇
  免费   649篇
  国内免费   71篇
耳鼻咽喉   107篇
儿科学   284篇
妇产科学   286篇
基础医学   1288篇
口腔科学   138篇
临床医学   809篇
内科学   2612篇
皮肤病学   267篇
神经病学   1101篇
特种医学   351篇
外科学   982篇
综合类   18篇
预防医学   604篇
眼科学   91篇
药学   645篇
中国医学   19篇
肿瘤学   947篇
  2024年   13篇
  2023年   123篇
  2022年   269篇
  2021年   416篇
  2020年   271篇
  2019年   359篇
  2018年   372篇
  2017年   288篇
  2016年   348篇
  2015年   391篇
  2014年   469篇
  2013年   578篇
  2012年   878篇
  2011年   850篇
  2010年   466篇
  2009年   395篇
  2008年   551篇
  2007年   501篇
  2006年   467篇
  2005年   408篇
  2004年   350篇
  2003年   323篇
  2002年   230篇
  2001年   84篇
  2000年   100篇
  1999年   110篇
  1998年   55篇
  1997年   34篇
  1996年   31篇
  1995年   27篇
  1994年   24篇
  1993年   32篇
  1992年   85篇
  1991年   75篇
  1990年   50篇
  1989年   72篇
  1988年   52篇
  1987年   55篇
  1986年   50篇
  1985年   57篇
  1984年   35篇
  1983年   41篇
  1981年   11篇
  1979年   16篇
  1978年   12篇
  1977年   12篇
  1973年   10篇
  1971年   13篇
  1970年   16篇
  1969年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Much research has shown that cognitive processes are largely guided by individuals' states of mind (Mancini & Gangemi, 2002a, in press; Smeets, de Jong, & Mayer, 2000). In this paper, we specifically consider a state of mind characterized by guilt for having acted irresponsibly. This state is currently considered the breeding ground for the obsessive–compulsive disorder (Rachman, 2002; Salkovskis & Forrester, 2002). Our aim is to examine the impact of this state of mind on decision under risk. We hypothesize that individuals' choices (risk seeking/risk aversion) depend on how they evaluate themselves, as guilty or as victims of a wrong, and thus on moral values. People who evaluate them‐selves as guilty are expected to show a risk‐averse preference. People who evaluate themselves as victims are expected to show a risk‐seeking preference. In two different experiments, we demonstrated that non‐clinical participants' aversion to risky choices and preference for risky choices vary as a function of their moral role (guilty/victim). As predicted, in both the experiments, participants experienced intolerance for risk, making more riskless choices, in the context of guilt. Thus, aversion to risk‐taking is actually affected by a mental state of guilt. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   
22.
23.
Laser energy can be used for a variety of neoplastic diseases including benign tumors, early stage malignancies, and advanced carcinomas, either with curative intent or for palliation. Nd:YAG laser photocoagulation of 168 colorectal adenomas allowed a complete eradication in 70% of cases, after a mean follow-up of 22 months. Advanced and obstructing tumors were treated with Nd:YAG laser to recanalize the lumen. In the upper gastrointestinal tract the recanalization of the lumen by means of laser photocoagulation improved the quality of life and survival. In fact, in our series of 308 patients treated, 1-year survival was 23% in recanalized patients and 7% in nonrecanalized patients. In the lower gastrointestinal tract, 289 cancer patients were treated and an amelioration of symptoms related to the obstruction was obtained in 93%. The current indication for photodynamic therapy is mainly the treatment of flat or ulcerative early stage tumors in the esophagus and stomach of high risk patients. Out of 17 patients treated, 14 were locally cured.  相似文献   
24.
Ten protein coding loci (6‐PGD, A1‐AT, ACP1, CaII, ESD, GC, GPX1, Hbβ, PGM1, and TF) were analyzed in the Mbenzele Pygmies from the Central African Republic. The frequency data were used to calculate the genetic distances between Mbenzele Pygmies and other African groups. In the principal coordinate plot of FST genetic distances, the Mbenzele cluster together with other Pygmies of the western cluster, the Biaka from C.A.R., Gielli from Cameroon, and Babinga from Congo. By contrast, they are considerably distanced from other Pygmy groups of the eastern cluster (Twa from Rwanda, Mbuti from Zaire). Genetic distances obtained using protein loci were compared with those based on microsatellite loci. The two distance matrices are insignificantly correlated (r = 0.268; one tail probability = 0.332), and the main difference is in the higher genetic affinity between the Mbenzele and Biaka Pygmies observed at the protein level. Although reasons underlying the discrepancy between inter‐populational variation at protein and DNA loci are not established with certainty, the comparison suggests that the genetic distance between the Mbenzele and Biaka Pygmies at microsatellite loci could have been shaped by genetic drift. Am. J. Hum. Biol. 14:9–14, 2002.© 2002 Wiley‐Liss, Inc.  相似文献   
25.
PDB is genetically heterogeneous. Mutations of the sequestosome1 gene have been reported in sporadic and familial forms of Paget's in patients of French Canadian and British descent. Mutational analyses in different ethnic groups are needed to accurately investigate hereditary diseases. We describe two novel mutations of sequestosome1 in 62 Italian sporadic patients, confirming the role of the encoded protein in this disorder. INTRODUCTION: Paget's disease of bone (PDB) is a relatively common disease of bone metabolism reported to affect up to 3% of whites over 55 years of age. The disorder is genetically heterogeneous, and at present, there is scientific evidence that at least eight different human chromosomal loci are correlated with its pathogenesis. Mutations of the sequestosome1 (SQSTM1) gene were identified as responsible for most of the sporadic and familial forms of Paget in patients of French Canadian and British descent. Such mutations were located at exon 7 and 8 levels, encoding for the ubiquitin protein-binding domain (UBA) and representing a mutational hot spot area. MATERIALS AND METHODS: To verify the involvement of this gene in Italian subjects affected by PDB, we performed mutational analysis in 62 sporadic PDB cases. RESULTS: We described three different mutations at exon 8 level: P392L, already described in the French Canadian population and families predominantly of British descendent, and two novel mutations consisting of the amino acid substitutions M404V and G425R. No significant differences in the clinical history of PDB have been observed in patients with SQSTM1 mutations in respect to those without. CONCLUSIONS: Even though our findings suggest a minor involvement of the SQSTM1 gene in the pathogenesis of sporadic Italian Paget's cases, the identification of different significant mutations within the SQSTM1 gene in unrelated, but clinically similar individuals, offers extremely convincing evidence for a causal relationship between this gene and PDB. Longitudinal studies are needed to assess the penetrance of genotype/phenotype correlations. Our findings confirm the evidence of a clustered mutation area at this level in this disorder.  相似文献   
26.
OBJECTIVE: To investigate the association between the use of fluoroquinolone agents and the risk of tendinitis in a large population-based case-control study. METHODS: The study was performed by linking automated health databases from the Region of Lombardia, Italy. Cases were patients aged > or =18 years who had a hospital discharge diagnosis of non-traumatic tendinitis in 2002-3. For each case, up to five controls were randomly selected among those eligible for inclusion in the study. A conditional logistic regression model was used to estimate the odds ratio of tendinitis associated with the current, recent and past use of fluoroquinolones. Odds ratios were adjusted for exposure to other antibacterials and other drugs. RESULTS: 22,194 cases and 104,906 controls met the inclusion criteria. Current use of fluoroquinolones significantly increased the risk of tendon disorders as a whole (odds ratio [OR] = 1.7; 95% CI 1.4, 2.0), tendon rupture (OR = 1.3; 95% CI 1.0, 1.8) and rupture of the Achilles' tendon (OR = 4.1; 95% CI 1.8, 9.6). Concomitant use of corticosteroids and fluoroquinolones increased the risk of both tendon rupture (OR = 3.1; 95% CI 1.5, 6.3) and rupture of the Achilles' tendon (OR = 43.2; 95% CI 5.5, 341.1). DISCUSSION: Evidence that exposure to fluoroquinolones is associated with the sudden occurrence of tendinitis is supported by this large population-based study. We can estimate that a single case of rupture of the Achilles' tendon would occur for every 5958 persons treated with fluoroquinolones (95% CI 2148, 23,085). The corresponding number needed to harm is 979 (95% CI 122, 9172) for patients who concomitantly use corticosteroids and 1638 (95% CI 351, 8843) for those aged >60 years. CONCLUSION: Clinicians should be aware of this adverse effect, and the increased risk for fluoroquinolone-associated tendinitis in elderly patients with corticosteroid use must be considered when these agents are prescribed.  相似文献   
27.
The visualization of incorporation sites of the thymidine analog bromodeoxyuridine (BrdU) into DNA, detected by immunocytochemistry, has been proposed as an index of the percentage of S-phase cells in a variety of tissues and as an easy, less expensive alternative to autoradiography. This technique has not yet been applied to the study of physiological cell renewal in the normal liver. In the present study, results obtained with this method in the liver of normal young adult rats is reported. BrdU was administered in vivo and subsequent incorporation was detected by the PAP technique using monoclonal anti-BrdU antibodies. The nuclei exhibiting a positive reaction within the liver were few and accounted for about 0.45% of all hepatocytes. Positive cells were located preferentially in zone 1, which contained 82.7% of the labeled cells. Zone 2 contained 15.4%, while only 1.9% of the labeled cells were found in zone 3. Positive-staining Kupffer cell nuclei were rare (about 0.5% of all Kupffer cells) and were distributed randomly in the hepatic lobule. These findings provide quantitative data about hepatocyte renewal in the normal liver in the absence of a growth stimulus. The simplicity and the reproducibility of this technique suggests that further application of this method in situations assessing hepatic regeneration are indicated.  相似文献   
28.
Estrogen sulfotransferase (EST) catalyzes transfer of the sulfate group from phosphoadenosine phosphosulfate to estrogenic steroids. Since estrogen sulfates do not bind to the estrogen receptor with high affinity, EST can control the intracellular level of the receptor-active estrogens. Androgen action in the rat liver, as indicated by the androgenic induction of alpha 2u-globulin, is inhibited by low levels of estrogens. Thus, in situ estrogen inactivation by EST is expected to increase hepatic androgen sensitivity. During the lifespan of the animal, rat liver undergoes three distinct phases of androgen sensitivity, i.e. prepubertal androgen insensitivity, androgen sensitivity after approximately 40 days of age, and androgen insensitivity during senescence (greater than 750 days). EST in the liver is expressed only after puberty, when the liver becomes androgen sensitive. Furthermore, localization of EST and its corresponding mRNA within the lobular unit of the liver demonstrates that only androgen-responsive hepatocytes located around the central vein contain immunoreactive EST and its corresponding mRNA. These temporal and spatial correlations of EST expression and hepatic androgen sensitivity support the concept that steroid-inactivating enzymes play important roles in sex hormone action.  相似文献   
29.
30.
An 18-kDa leukocyte membrane protein, termed 5-lipoxygenase-activating protein (FLAP), has recently been shown to be the target of two structurally distinct classes of leukotriene biosynthesis inhibitors. These classes of inhibitors are based on indole and quinoline structures and are represented by MK-886 and L-674,573, respectively. A novel class of hybrid structure based on the indole and quinoline classes of inhibitors, termed quindoles, has recently been developed. These compounds, exemplified by L-689,037, are potent inhibitors of leukotriene biosynthesis, both in vitro and in vivo. In the present study, we have developed and characterized a potent radioiodinated photoaffinity analogue of L-689,037, termed [125I]L-691,678. This compound was used in immunoprecipitation studies with FLAP antisera to show that the quindole series of leukotriene biosynthesis inhibitors interact directly with FLAP. In addition, we show that MK-886, L-674,573, and L-689,037 specifically compete, in a concentration-dependent manner, with both [125I]L-691,678 and [125I]L-669,083, a photoaffinity analogue of MK-886, for binding to FLAP. These results suggest that these three classes of leukotriene biosynthesis inhibitors share a common binding site on FLAP, providing further evidence that FLAP represents a suitable target for structurally diverse classes of leukotriene biosynthesis inhibitors.  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