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   3837篇
  免费   330篇
  国内免费   58篇
耳鼻咽喉   16篇
儿科学   133篇
妇产科学   39篇
基础医学   415篇
口腔科学   91篇
临床医学   498篇
内科学   709篇
皮肤病学   98篇
神经病学   398篇
特种医学   379篇
外科学   435篇
综合类   97篇
一般理论   2篇
预防医学   262篇
眼科学   93篇
药学   256篇
中国医学   4篇
肿瘤学   300篇
  2022年   32篇
  2021年   47篇
  2020年   32篇
  2019年   55篇
  2018年   83篇
  2017年   39篇
  2016年   59篇
  2015年   63篇
  2014年   92篇
  2013年   123篇
  2012年   135篇
  2011年   123篇
  2010年   113篇
  2009年   130篇
  2008年   141篇
  2007年   194篇
  2006年   154篇
  2005年   154篇
  2004年   141篇
  2003年   125篇
  2002年   120篇
  2001年   126篇
  2000年   135篇
  1999年   101篇
  1998年   104篇
  1997年   116篇
  1996年   137篇
  1995年   102篇
  1994年   87篇
  1993年   71篇
  1992年   72篇
  1991年   60篇
  1990年   78篇
  1989年   96篇
  1988年   89篇
  1987年   87篇
  1986年   100篇
  1985年   93篇
  1984年   30篇
  1983年   30篇
  1982年   33篇
  1981年   25篇
  1980年   25篇
  1979年   39篇
  1978年   28篇
  1977年   18篇
  1976年   18篇
  1975年   23篇
  1973年   24篇
  1972年   17篇
排序方式: 共有4225条查询结果,搜索用时 234 毫秒
41.
Numerous studies have shown evidence of cerebral ventricular enlargement in schizophrenia and its relationship to severity of clinical symptoms and psychosocial dysfunction. In this large prospective study, 88 noninstitutionalized DSM-III-R schizophrenic patients were administered a CT scan and rated for positive and negative symptomatology and premorbid adjustment. The CT scans from 14 healthy controls were used for comparison of cerebral ventricular measures. Patients had an enlarged ventricle to brain ratio of the anterior portion of the lateral ventricles, the frontal horns, compared with controls. Patients with larger frontal horns had more severe negative symptoms and poorer premorbid childhood adjustment. The area of the main body of the cerebral lateral ventricles, though not elevated in patients, was correlated with the total number of prior hospitalizations. These results support the hypothesis of a structural and functional "frontal" deficit in schizophrenia.  相似文献   
42.
43.
44.
45.
In a human in-vitro fertilization (IVF) programme, the effect of co- culture of embryos with human fibroblasts was evaluated with respect to pregnancy rate and embryo development. Patients were included in the study after giving informed written consent. The IVF treatments were randomly assigned by stratification of both age (<36 versus > or =36 years) and previous IVF attempts (yes versus no). After fertilization was established, the zygotes were transferred to a 4-well dish with or without fibroblasts and cultured for 2 days. On the third day after ovum pick-up (OPU), cell number and quality [5 (good) to 1 (poor)] of the embryos were scored and a maximum of three embryos was transferred. Supernumerary embryos of good quality were cryopreserved. The design of this study was a group sequential trial with the objective of detecting differences between pregnancy rates following IVF with conventional incubation or incubation in co-culture with fibroblasts. This design included one evaluation at half-way data collection. In the study, 148 patients had an OPU, of whom 77 were allocated to the co-culture group. There was no statistically significant difference in pregnancy rate, cell number and embryo quality between the two groups. The ongoing pregnancy rate per embryo transfer was 27% in co-culture and 30% in the conventional culture group. The implantation rates per transferred embryo were 17 and 18% respectively. Using a multivariate logistic regression model for the probability of ongoing pregnancies, the odds ratio of co-culture, adjusted for age and previous IVF attempts, was not statistically significant. In conclusion, co-culture with human fibroblasts does not contribute to an improvement of embryo quality nor to a higher pregnancy rate after IVF in an unselected group of patients.   相似文献   
46.
Seven randomized trials published in the last six years have shown that warfarin reduces the risk of ischaemic strokes and death in patients with atrial fibrillation. The annual rates of major bleeding episodes in all these trials were low and, as a result, doctors in primary and secondary care are being encouraged to consider using warfarin for patients with atrial fibrillation unless there are obvious contraindications. However, the populations used in these studies were highly selected and rigorously monitored throughout the trial period to minimize the risk of bleeding in a way which probably could not be expected in routine primary care. Although the rates of major bleeding episodes were uniformly low, the rates of minor bleeding episodes were much higher and these could impact substantially on patients' views of the treatment and on the workload of the primary care team. Evidence is now at hand which allows the stratification of risk in patients with atrial fibrillation which should enable those who are at greatest risk to be considered for this form of treatment. Patients may develop risk factors over time which could render them unsuitable for continuation of warfarin therapy. The general practitioner is centrally placed to make the decision about initiating or continuing treatment or indeed stopping it. Several models for decision making in warfarin treatment from primary and secondary care are proposed.  相似文献   
47.
The Escherichia coli human fecal isolates F-18 and K-12 are excellent colonizers of the streptomycin-treated mouse intestine. E. coli F-18 and E. coli K-12 eda mutants (unable to utilize glucuronate, galacturonate, and gluconate) were constructed by insertional mutagenesis. Neither the E. coli F-18 eda nor the E. coli K-12 eda mutant was able to colonize the streptomycin-treated mouse intestine, whether they were fed to mice together with their respective parental strains or alone. Complementation of the eda mutants with pTC190 (containing a functional E. coli K-12 eda gene) completely restored the colonization ability of both eda mutants. Relative to their parental strains, the E. coli F-18 eda mutant and the E. coli K-12 eda mutant grew poorly in cecal mucus isolated from mice fed either normal mouse chow or a synthetic diet containing sucrose as the sole carbon source, yet the mutants and parental strains demonstrated identical growth rates in minimal medium with glucose as the carbon source. E. coli F-18 edd eda and E. coli K-12 edd eda double mutants colonized the streptomycin-treated intestine when fed to mice alone; however, when fed simultaneously with their respective parental strains, they were poor colonizers. Since the edd gene is involved only in gluconate metabolism via the Entner-Doudoroff pathway, these results implicate the utilization of gluconate and the Entner-Doudoroff pathway as important elements in E. coli colonization of the streptomycin-treated mouse large intestine.  相似文献   
48.
Summary The anatomic constraints imposed on a total artificial heart (TAH) require specific anatomic studies. A thoracic anatomic study was performed with a scanning device equipped with three-dimensional (3-D) reconstruction software on 15 male patients, between the ages of 41 to 63 years (52 ± 6 years). All were candidates for heart transplantation. The 3-D reconstructions of the cardiovascular structures obtained from surgical anatomy data specific to TAH implantation allowed a volumetric measurement of these structures. A modeling diagram of these structures permitted reproducible quantitative measurements of the 35 geometrical parameters which characterized shape, orientation, and position of these structures within the thorax. Most of the measured parameters were characterized by low variability (coefficient of variation from 10 to 25%).
Modélisation tridimensionnelle de l'anatomie du cur et des gros vaisseaux
Résumé Les contraintes anatomiques imposées au cur artificiel total (CAT) nécessitent des études anatomiques spécifiques. Une étude anatomique thoracique a été réalisée avec un scanner doté d'un logiciel de reconstruction tridimensionnelle (3-D) chez 15 patients, tous de sexe masculin, agés de 41 à 63 ans (52 ± 6 ans), et candidats à une transplantation cardiaque. Les reconstructions 3-D des structures cardio-vasculaires réalisées selon les données de l'anatomie chirurgicale propre à l'implantation du CAT ont permis la mesure volumétrique de ces structures. Un schéma de modélisation de ces structures a permis des mesures quantitatives reproductibles de 35 paramètres géométriques caractéristiques de la forme, de l'orientation, de la position de ces structures dans le thorax. Les résultats de ces mesures ont pu être exprimés en termes statistiques. La plupart des paramètres mesurés étaient caractérisés par une faible variabilité (coefficients de variations de 10 à 25%).
  相似文献   
49.
Acute cardiac events temporally related to cocaine abuse   总被引:17,自引:0,他引:17  
The increasingly widespread use of cocaine in the United States has been accompanied and perhaps exacerbated by the misconception that the drug is not associated with serious medical complications. In particular, the potential for cocaine to precipitate life-threatening cardiac events needs to be reemphasized. We report the clinical and pathological findings in seven people in whom nonintravenous "recreational" use of cocaine was temporally related to acute myocardial infarction, ventricular tachycardia and fibrillation, myocarditis, sudden death, or a combination of these events. We also review data on 19 previously reported cases of cocaine-related cardiovascular disorders. Analysis of all 26 patients indicated the following findings: the cardiac consequences of cocaine abuse are not unique to parenteral use of the drug, since nearly all the patients took the drug intranasally; underlying heart disease is not a prerequisite for cocaine-related cardiac disorders; seizure activity, a well-documented noncardiac complication of cocaine abuse, is neither a prerequisite for, nor an accompanying feature of, cardiac toxicity of cocaine; and the cardiac consequences of cocaine are not limited to massive doses of the drug. Although the pathogenesis of cardiac toxicity of cocaine remains incompletely defined, available circumstantial evidence suggests that cocaine has medical consequences that are equal in importance to its well-documented psychosocial consequences.  相似文献   
50.
The persistence of Cytomegalovirus (CMV) with alteration of cell surface expression in certain tissues may initiate the tissue destruction that leads to the clinical manifestations of Sjogren's Syndrome. Salivary gland and lacrimal gland ductal cells are immunologically attacked due to CMV antigenic expression. The destruction of these ducts leads to xerostomia and keratonconjunctivitis sicca, the hallmarks of Sjogren's Syndrome.  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