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   1410414篇
  免费   113528篇
  国内免费   3332篇
耳鼻咽喉   18360篇
儿科学   46547篇
妇产科学   41044篇
基础医学   200720篇
口腔科学   37692篇
临床医学   125974篇
内科学   284302篇
皮肤病学   33353篇
神经病学   116844篇
特种医学   53827篇
外国民族医学   464篇
外科学   210469篇
综合类   32754篇
现状与发展   3篇
一般理论   487篇
预防医学   109979篇
眼科学   31489篇
药学   98487篇
  1篇
中国医学   3348篇
肿瘤学   81130篇
  2021年   10843篇
  2019年   11661篇
  2018年   16568篇
  2017年   12665篇
  2016年   14254篇
  2015年   15999篇
  2014年   22550篇
  2013年   33381篇
  2012年   45367篇
  2011年   47906篇
  2010年   28149篇
  2009年   27040篇
  2008年   44301篇
  2007年   46805篇
  2006年   47373篇
  2005年   45841篇
  2004年   43733篇
  2003年   41678篇
  2002年   40174篇
  2001年   72996篇
  2000年   74522篇
  1999年   61553篇
  1998年   16987篇
  1997年   15428篇
  1996年   15581篇
  1995年   14788篇
  1994年   13394篇
  1993年   12581篇
  1992年   45835篇
  1991年   43476篇
  1990年   41486篇
  1989年   39549篇
  1988年   36178篇
  1987年   35351篇
  1986年   32859篇
  1985年   31276篇
  1984年   23823篇
  1983年   20023篇
  1982年   12207篇
  1981年   10779篇
  1979年   20700篇
  1978年   14576篇
  1977年   12084篇
  1976年   11364篇
  1975年   11619篇
  1974年   13988篇
  1973年   13533篇
  1972年   12633篇
  1971年   11469篇
  1970年   10910篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
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   
972.
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   
973.
974.
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   
975.
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   

976.
977.
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   
978.
Auditory P300 and eye tracking dysfunction in schizophrenic pedigrees   总被引:4,自引:0,他引:4  
Several psychophysiological abnormalities associated with schizophrenia have been proposed as genetic trait markers of vulnerability to the disorder. Smooth pursuit eye tracking dysfunction and abnormal long latency event-related potentials are the most promising candidates. Both are independent of the effects of psychotropic medication or mental state at the time of testing, and twin studies demonstrate that each has a high level of heritability. Having recorded smooth pursuit eye tracking and event-related potentials in 20 high-density schizophrenic families, we find abnormalities in one or both measures in most of the families studied. The abnormalities, when present, occur in the family members with schizophrenia and other forms of functional psychosis, and they have a bimodal distribution with approximately half the nonschizophrenic relatives also showing eye tracking dysfunction and/or abnormal event-related potentials. Some of these relatives had psychiatric symptoms; others were normal. Our results suggest that psychophysiological examination can help to clarify the boundaries of schizophrenia spectrum disorder. By helping to decide the phenotypic status of nonschizophrenic family members, this should increase the power of DNA linkage studies.  相似文献   
979.
The agar-gel precipitation test (AGPT) was compared with Enzyme Immunoassay (EIA) for the detection of Chlamydia trachomatis, 164 women being screened for chlamydial antibodies and antigens in their sera and in endocervical specimens, respectively. The AGPT showed good correlation with EIA in the 164 paired sera and endocervical specimens, resulting in 27 (16.5%) and 22 (13.4%) positive results, respectively (P greater than 0.05). The overall sensitivity of the AGPT compared to EIA was 86.4% (19 of 22), and the specificity was 94.4% (134 of 142).  相似文献   
980.
This study examined the relationship between risk factors and initiation of alcohol use over a 15-month period among a cohort of 7th graders who were abstainers at the time of initial testing. The relationship between risk factors and alcohol use was examined using a discriminant function analysis. At the univariate level, rejection of parental authority, deviant behavior, and sensation seeking were statistically significant. The discriminant function retained only three of the risk factors: rejection of parental authority, deviant behavior, and religious commitment. Implications for school-based prevention programs are discussed, particularly the need to target primary prevention programs based upon adolescents' risk.  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