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   1424831篇
  免费   114957篇
  国内免费   3354篇
耳鼻咽喉   18505篇
儿科学   46965篇
妇产科学   41422篇
基础医学   202588篇
口腔科学   37972篇
临床医学   127685篇
内科学   287106篇
皮肤病学   33486篇
神经病学   118283篇
特种医学   54368篇
外国民族医学   464篇
外科学   212590篇
综合类   33031篇
现状与发展   3篇
一般理论   500篇
预防医学   111449篇
眼科学   31685篇
药学   99458篇
  1篇
中国医学   3353篇
肿瘤学   82228篇
  2021年   11058篇
  2019年   11874篇
  2018年   16793篇
  2017年   12861篇
  2016年   14464篇
  2015年   16209篇
  2014年   22849篇
  2013年   33913篇
  2012年   46018篇
  2011年   48637篇
  2010年   28543篇
  2009年   27464篇
  2008年   44966篇
  2007年   47506篇
  2006年   48039篇
  2005年   46564篇
  2004年   44383篇
  2003年   42291篇
  2002年   40771篇
  2001年   73375篇
  2000年   74951篇
  1999年   61950篇
  1998年   17175篇
  1997年   15583篇
  1996年   15751篇
  1995年   14929篇
  1994年   13535篇
  1993年   12714篇
  1992年   46143篇
  1991年   43756篇
  1990年   41755篇
  1989年   39844篇
  1988年   36418篇
  1987年   35584篇
  1986年   33099篇
  1985年   31484篇
  1984年   24009篇
  1983年   20170篇
  1982年   12328篇
  1981年   10884篇
  1979年   20851篇
  1978年   14702篇
  1977年   12180篇
  1976年   11469篇
  1975年   11715篇
  1974年   14129篇
  1973年   13648篇
  1972年   12752篇
  1971年   11583篇
  1970年   11001篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
We describe the reconstruction of the mandible using the spine of the scapula pedicled upon trapezius in a woman who had undergone previous mandibular irradiation and surgery. We show how the vascular supply to the trapezius scapular spine compound flap can be approached posteriorly and the spine of the scapula used to provide good length and contour for replacement of a wide mandibular defect.  相似文献   
972.
Diabetes-prone BioBreeding/Worcester (BB/Wor) rats received thrice weekly injections of mAb against antigens expressed on the surface of all T cells (OX19), cytotoxic/suppressor, and NK cells (OX8), helper/inducer cells (W3/25, OX35, OX38), and Ia+ cells (OX6, 3JP, OX17). Treatment with OX8 or OX19 achieved stable reductions of splenic and peripheral blood NK cells and helper/inducer T lymphocytes, respectively, and protected against diabetes. OX19 injections also prevented lymphocytic insulitis, thyroiditis, and the synthesis of autoantibodies to thyroid colloid and smooth muscle antigens. OX8 injections reduced splenic NK-mediated YAC-1 cell lysis, but did not prevent insulitis, thyroiditis, or autoantibody synthesis. Injections of mAb specific for antigens on the surface of helper/inducer cells, and for cells expressing IaE antigens provided marginal protection against diabetes without reductions of phenotypic subsets. These findings suggest that pancreatic beta cell destruction in the spontaneously diabetic BB/Wor rat is mediated by the combined action of NK and helper/inducer cells.  相似文献   
973.
The neuronal morphological development of the avian telencephalic cortex (DMC) is studied in Golgi-stained brain sections. The neuronal types at embryonic days 10, 13, 16, as well as of newborn chick are identified. The immature neurons are characterized by the presence of hair-like processes, growth cones and dendritic varicosities. These characteristics are absent in neuronal types of newborn chick. There are five patterns of differentiation, which produce six neuronal types in the newborn chick: horizontal neurons, pyramidal neurons, bipyramidal neurons, short axon multipolar neurons, long axon multipolar neurons and periventricular neurons. The morphological features of migrating embryonic cells are described. The dendritic spines appear in 16-day embryos in the majority of neuronal types.  相似文献   
974.
C K Kellogg  T M Retell 《Brain research》1986,366(1-2):137-144
The effect of prenatal exposure to diazepam (over gestational days 13-20) on the release of tritiated norepinephrine [( 3H]NE) from selected brain regions was analyzed to determine mechanisms whereby such exposure could disrupt functioning in specific NE neurons, as previously observed. Pregnant rats were administered diazepam (DZ) once daily at doses of 1.0, 2.5 or 10.0 mg/kg and the offspring studied as adults at 70-90 days of age and during development at 14, 21, 35 and 56 days of age. Release of [3H]NE was measured during in vitro incubation using 25 mM potassium as the depolarizing stimulus. As noted previously, prenatal exposure to DZ induced an effect only on NE neurons innervating the hypothalamus, sparing the NE innervation to the hippocampus and cerebellum. Prenatal exposure to DZ had no effect on the depolarized release of [3H]NE in the hypothalamus until after 35 days of age, a developmental pattern previously observed with respect to endogenous NE levels. In adult rat offspring, however, the depolarization-induced release of [3H]NE from the hypothalamus decreased 28%, 32% and 64% (relative to uninjected control values) in animals prenatally exposed to DZ at 1.0, 2.5 or 10 mg/kg/day respectively. Concurrent exposure of the pregnant dam to benzodiazepine antagonists (Ro 15-1788 or ethyl-beta-carboline-3-carboxylate) prevented the effects of DZ (2.5 mg/kg/day) on [3H]NE release, demonstrating again the importance of the benzodiazepine binding site to the effects induced by the early DZ exposure. The initial accumulation of the [3H]NE was not altered by the prenatal exposure.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
975.
A Coulter Counter, Model TAII, was used to determine both solubility and surface specific dissolution rate of two sparingly soluble materials suspended in micellar solutions. The equilibrium solubility increased linearly with surfactant concentration, thereby making it possible by extrapolation to characterize materials with an aqueous solubility down to 1 ppm or less. At high concentrations (greater than 0.1% w/v) the effect of surfactant concentration on the surface specific dissolution rate was less than that predicted from the increased bulk solubility.  相似文献   
976.
977.
Greater body fatness during childhood is associated with reduced risk of premenopausal breast cancer, but few studies have addressed the relation of adiposity with sex hormones in girls. We prospectively examined associations between adiposity and circulating levels of sex hormones and sex hormone-binding globulin (SHBG) among 286 girls in the Dietary Intervention Study in Children. Participants were 8 to 10 years old at baseline and were followed for an average of 7 years. Anthropometric measurements were taken at baseline and at subsequent annual visits, and blood samples were collected every 2 years. Concentrations of dehydroepiandrosterone sulfate (DHEAS) during follow-up were higher among girls with greater body mass index (BMI) at baseline. The mean for the lowest BMI quartile was 63.0 microg/dL compared with 78.8 microg/dL for the highest quartile, and each kg/m(2) increment in baseline BMI was associated with a 4.3% increase (95% confidence interval, 1.6-7.0%) in DHEAS levels during follow-up (P(trend) = 0.002). Concentrations of SHBG during follow-up were lower among girls with greater BMI at baseline. The mean for the lowest BMI quartile was 94.8 nmol compared with 57.5 nmol for the highest quartile, and each kg/m(2) increment in baseline BMI was associated with an 8.8% decrease (95% confidence interval, 7.0-10.6%) in SHBG levels during follow-up (P(trend) < 0.0001). Estrogen and progesterone concentrations were similar across BMI quartiles. These findings suggest that adiposity may alter DHEAS and SHBG levels in girls. Whether and how these differences affect breast development and carcinogenesis requires further research.  相似文献   
978.
Background: Bupivacaine retards myocardial acidosis during ischemia. The authors measured function of rat isolated hearts after prolonged storage to determine whether bupivacaine improves cardiac protection compared with standard cardioplegia alone.

Methods: After measuring cardiac function on a Langendorff apparatus, hearts were perfused with cardioplegia alone (controls), cardioplegia containing 500 [mu]m bupivacaine, or cardioplegia containing 2 mm lidocaine; were stored at 4[degrees]C for 12 h; and were then reperfused. Heart rate and left ventricular developed pressures were measured for 60 min. Maximum positive rate of change in ventricular pressure, oxygen consumption, and lactate dehydrogenase release were also measured.

Results: All bupivacaine-treated, four of five lidocaine-treated, and no control hearts beat throughout the 60-min recovery period. Mean values of heart rate, left ventricular developed pressure, maximum positive rate of change in ventricular pressure, rate-pressure product, and efficiency in bupivacaine-treated hearts exceeded those of the control group (P < 0.001 at 60 min for all). Mean values of the lidocaine group were intermediate. Oxygen consumption of the control group exceeded the other groups early in recovery, but not at later times. Lactate dehydrogenase release from the bupivacaine group was less than that from the control group (P < 0.001) but did not differ from baseline.  相似文献   

979.
980.
Patients with complaints of halitosis do seek treatment from physicians and dental practitioners, because of the fear that their halitosis may interfere with their social activities. Although the prevalence of halitosis has been reported to be as high as 50%, most physicians and dental practitioners are poorly informed about the causes and treatments of halitosis. In order to care for patients with complaints of halitosis a multidisciplinary team was established at the Erasmus Medical Centre, Rotterdam, The Netherlands. The team included a dental hygienist, an otorhinolaryngologist, and a dentist, who developed a special halitosis programme. One short press release regarding the establishment of the team, was provided to the national press-centre. In the out-patient clinic more than 700 patients were seen by the team. Using a structured questionnaire fed to a PC, patients answered questions regarding complaints about the oral cavity, the upper respiratory tract, the throat, their general health, their cleansing habits of the oral cavity, and prior experiences with general physicians, dental practitioners, and medical specialists. They underwent examinations of the extent of their halitosis, of the perioral and neck region, the oral cavity, the upper respiratory tract, and the upper digestive tract. Finally, the members of the team came to a joint diagnosis and a joint treatment plan for every individual patient. Of the first 700 consecutive patients around 90% had a natural dentition without removable partial dentures. More than 60% were diagnosed as having periodontal disease with pockets of 4 mm or more in the maxilla. This figure was more than 50% in the mandible. Around 95% had tongue coating.  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