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   8573篇
  免费   745篇
  国内免费   10篇
耳鼻咽喉   42篇
儿科学   210篇
妇产科学   126篇
基础医学   1065篇
口腔科学   321篇
临床医学   964篇
内科学   1994篇
皮肤病学   78篇
神经病学   640篇
特种医学   272篇
外科学   1189篇
综合类   120篇
一般理论   5篇
预防医学   926篇
眼科学   153篇
药学   739篇
中国医学   14篇
肿瘤学   470篇
  2022年   71篇
  2021年   171篇
  2020年   82篇
  2019年   158篇
  2018年   197篇
  2017年   150篇
  2016年   153篇
  2015年   174篇
  2014年   244篇
  2013年   366篇
  2012年   553篇
  2011年   534篇
  2010年   286篇
  2009年   280篇
  2008年   463篇
  2007年   484篇
  2006年   468篇
  2005年   458篇
  2004年   456篇
  2003年   354篇
  2002年   424篇
  2001年   156篇
  2000年   152篇
  1999年   180篇
  1998年   78篇
  1997年   90篇
  1996年   68篇
  1995年   68篇
  1994年   62篇
  1993年   49篇
  1992年   116篇
  1991年   108篇
  1990年   101篇
  1989年   109篇
  1988年   98篇
  1987年   93篇
  1986年   93篇
  1985年   89篇
  1984年   86篇
  1983年   82篇
  1982年   81篇
  1981年   71篇
  1980年   46篇
  1979年   70篇
  1978年   47篇
  1977年   47篇
  1976年   49篇
  1974年   49篇
  1973年   32篇
  1972年   39篇
排序方式: 共有9328条查询结果,搜索用时 15 毫秒
41.
BACKGROUND: Few studies have measured pigeon allergens in non pigeon coop environments. This study was conducted to determine approximate pigeon dropping allergen concentrations in indoor environments. METHODS: Polyclonal antibody serum was prepared by injecting a rabbit three times with crude wild pigeon dropping extract in 50 mM Tris buffer with Freund's adjuvant. One hundred and fifteen dust samples were collected in a pigeon-infested school, pigeon coops, homes and hospitals and analyzed by a direct competitive pigeon enzyme-linked immunosorbent assay (ELISA). RESULTS: The highest level of pigeon allergen inhibitory activity were recorded in four samples from pigeon coop bedding samples with a median activity of 11.2% relative to pigeon droppings. The second highest level of pigeon allergens was in a pigeon-infested high school with a median or 7.4% activity relative to pigeon droppings. At an entrance underneath pigeon roosts, one sample had a relative inhibitory activity of 62.3%. Pigeon allergen inhibitory levels were generally low in the home and hospital samples, but nevertheless 46 out of 89 of these samples were still above detection limit. CONCLUSIONS: This study suggests that large concentrations of pigeon allergens can be found in buildings without domestic pigeons such as the pigeon-infested high school.  相似文献   
42.
Grebe chondrodysplasia and brachydactyly in a family   总被引:1,自引:0,他引:1  
A family is reported in which various skeletal abnormalities have been segregating over three generations. The Great-grandfather (11) of the consultand had features consistent with Grebe chondrodysplasia. The other members of the family have brachydactyly, radiologically characterised by short first metacarpals and short middle phalanges of the index and little fingers. The possibility of association of familial brachydactyly and Grebe chondrodysplasia is discussed. An attempt has been made to deal with the genetic counselling problem in this particular family.  相似文献   
43.
A cDNA clone of mRNA for rabies virus matrix (M) protein has been identified. The clone hybridizes to an mRNA species from rabies virus-infected cells, whose size correlates to the size of the M protein in rabies virions, and selects an mRNA that translates into a polypeptide corresponding in size to M protein. The nucleotide sequence of the cloned cDNA was determined and from this a complete amino acid sequence for M protein was deduced. The deduced sequence of 202 amino acids bears no detectable sequence homology with vesicular stomatitis virus M protein although these proteins may share functional homology.  相似文献   
44.
Lipid peroxidation aldehydes of the 4-hydroxy-, ß-unsaturatedtype, as well as the tobacco-smoke related , ß-unsaturatedaldehyde, acrolein, were highly cytotoxic and decreased theintracellular thiol content in cultured human bronchial fibroblastsafter treatment with micromolar concentrations. In comparison,formaldehyde and acetaldehyde were less toxic and 100- to 300-foldhigher doses were required to affect cell survival or thiollevels. The unsaturated aldehydes also markedly inhibited theDNA repair enzyme O6-methylguanine-DNA methyltransferase knownto have a cysteine residue in its active site, but had no effecton the activity of uracil-DNA glycosylase. Our results indicatethat reactive aldehydes of either exogenous or endogenous originhave direct cytotoxic effects and may also make cells more susceptibleto other toxic chemicals due to an impairment in cellular defensemechanisms, e.g., DNA repair and detoxification by systems requiringglutathione.  相似文献   
45.
Traditionally, it has been assumed that there is only one type of anxiety; recent pharmacologic evidence suggests that there may be several. The psychoanalytic concept of "neurotic" symptoms as depressurizing mechanisms is out of keeping with most evidence now available. Spontaneous or "free-floating" anxiety may be partly biologic and genetic in origin. Anxiety symptoms evoked by specific stimuli behave in part like conditioned responses. Where conditioning theory has failed to propose a plausible unconditioned stimulus for pathologic anxiety, biology, ethology, and psychoanalysis may have been more successful.  相似文献   
46.
In 16 adult dogs the anterior cruciate ligament (ACL) was transected and then reconstructed using freeze dried fascia lata allografts. Eight of the dogs had the intraarticular graft passed through drill holes in the tibia and femur, while in the other eight dogs the graft was passed through a drill hole in the tibia and routed "over-the-top" of the lateral femoral condyle. In all dogs the grafts were then passed deep to the lateral collateral ligament and secondarily secured to the tibia as an extraarticular reconstruction. Specimens from each group underwent histologic study and biomechanical testing on a mechanical testing system at 3, 6, 12, and 24 week intervals. All grafts were found to be intact at sacrifice with no overt evidence of biologic incompatibility. The knees displayed only mild instability to clinical testing without evidence of arthrosis. Histologically, the grafts appeared to function as a collagenous scaffolding for revascularization and fibrovascular creeping substitution. The mean maximum load at failure in the 24 week specimens reached 536.44 N, compared to values of 801.85 N in contralateral knees with an intact ACL.  相似文献   
47.
Of 871 candidates presenting for upper gastrointestinal examinations, 16 met the rigorous criteria established for selecting asymptomatic normal volunteers. Frame-by-frame evaluation of their videorecorded pharyngeal swallow confirmed many observations made previously utilizing cine recording at much higher radiation dosages. In addition, new observations were made: the nasopharynx may not occlude until the bolus is entirely within the pharynx; air mixes with the bolus if the swallow is an "open" type; the epiglottis always inverts in normal individuals regardless of the type of swallow ("open," air filled oro-and hypopharynx into which the swallowed bolus is dropped; "closed," airless oropharynx into which the swallowed bolus is pushed by a continuous peristaltic drive of the tongue and palate, thus reconstituting the pharyngeal space); laryngeal descent may aid in stripping the bolus from the pharynx; the vestibule may not completely close during the swallow and the larynx can still be impervious to the bolus; the peristaltic wave does not begin until the bolus has breeched the cricopharyngeus; the cricopharyngeus may be seen frequently in normal individuals, but does not delay the passage of the bolus; asymmetric flow of the bolus around the larynx is common and may not be the result of epiglottic tilt or head positioning.  相似文献   
48.
Between 2013 and 2019, there was an increase in the consent rate for organ donation in the UK from 61% to 67%, but this remains lower than many European countries. Data on all family approaches (16,896) for donation in UK intensive care units or emergency departments between April 2014 and March 2019 were extracted from the referral records and the national potential donor audit held by NHS Blood and Transplant. Complete data were available for 15,465 approaches. Consent for donation after brain death was significantly higher than for donation after circulatory death, 70% (4260/6060) vs. 60% (5645/9405), (OR 1.58, 95%CI 1.47–1.69). Patient ethnicity, religious beliefs, sex and socio-economic status, and knowledge of a patient's donation decision were strongly associated with consent (p < 0.001). These factors should be addressed by medium- to long-term strategies to increase community interventions, encouraging family discussions regarding donation decisions and increasing registration on the organ donor register. The most readily modifiable factor was the involvement of an organ donation specialist nurse at all stages leading up to the approach and the approach itself. If no organ donation specialist nurse was present, the consent rates were significantly lower for donation after brain death (OR 0.31, 95%CI 0.23–0.42) and donation after cardiac death (OR 0.26, 95%CI 0.22–0.31) compared with if a collaborative approach was employed. Other modifiable factors that significantly improved consent rates included less than six relatives present during the formal approach; the time from intensive care unit admission to the approach (less for donation after brain death, more for donation after cardiac death); family not witnessing neurological death tests; and the relationship of the primary consenter to the patient. These modifiable factors should be taken into consideration when planning the best bespoke approach to an individual family to discuss the option of organ donation as an end-of-life care choice for the patient.  相似文献   
49.
Archives of Sexual Behavior - Changes to how gay, bisexual, and other men who have sex with men (GBM) connect with each other and with their communities have implications for HIV prevention. Social...  相似文献   
50.
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