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   1381358篇
  免费   97659篇
  国内免费   2071篇
耳鼻咽喉   19970篇
儿科学   45562篇
妇产科学   40229篇
基础医学   202832篇
口腔科学   38730篇
临床医学   117017篇
内科学   269961篇
皮肤病学   29630篇
神经病学   110227篇
特种医学   54515篇
外国民族医学   366篇
外科学   213303篇
综合类   26993篇
现状与发展   1篇
一般理论   337篇
预防医学   98514篇
眼科学   31363篇
药学   104800篇
  1篇
中国医学   2632篇
肿瘤学   74105篇
  2018年   14182篇
  2017年   10876篇
  2016年   12611篇
  2015年   13794篇
  2014年   18355篇
  2013年   28587篇
  2012年   39042篇
  2011年   42143篇
  2010年   24700篇
  2009年   22382篇
  2008年   41282篇
  2007年   44518篇
  2006年   44801篇
  2005年   43943篇
  2004年   42181篇
  2003年   41277篇
  2002年   40643篇
  2001年   61728篇
  2000年   64222篇
  1999年   53286篇
  1998年   15286篇
  1997年   13687篇
  1996年   13737篇
  1995年   12900篇
  1994年   12295篇
  1993年   11393篇
  1992年   41474篇
  1991年   40776篇
  1990年   40301篇
  1989年   39113篇
  1988年   36465篇
  1987年   35748篇
  1986年   34054篇
  1985年   32622篇
  1984年   24368篇
  1983年   21232篇
  1982年   12800篇
  1981年   11333篇
  1979年   22971篇
  1978年   16187篇
  1977年   14070篇
  1976年   13252篇
  1975年   14499篇
  1974年   16976篇
  1973年   16311篇
  1972年   15510篇
  1971年   14429篇
  1970年   13406篇
  1969年   12899篇
  1968年   12144篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
α-Sarcin binds one Zn(II) cation per protein molecule, with a Kd value of 0.9 mM, determined by equilibrium dialysis experiments. Ca(II), Mg(II), and Mn(II) do not bind to α-sarcin. Cd(II) and Co(II) also behave as Zn(II). The binding produces local modifications on the protein conformation affecting the microenvironment of tryptophan residues. The three cations modify the fluorescence emission of the protein. The near-u. v. circular dichroism spectrum of the protein is also altered. The binding of Zn(II) and related cations does not modify the secondary structure of the protein. The ribonucleolytic activity of a-sarcin is inhibited upon Zn(II) binding, but no alteration of the ability of the protein to aggregate phospholipid vesicles has been observed.  相似文献   
992.
An area analysis is presented of deaths in Auckland that were ostensibly avoidable, by appropriate medical intervention and treatment. Mortality data from the National Health Statistics Centre for the period 1977-85 were used in the analysis. The definition of an avoidable death was based on the International Classification of Diseases (ICD) code using established criteria. Eight percent of deaths of people under 65 years of age met the criteria. The basic spatial entity for the analysis is the census area unit and maps of Auckland are presented to show the distribution of avoidable mortality. It is found that there are significant and consistent spatial variations. Three areas with avoidable mortality that is generally higher than elsewhere are apparent: in south Auckland; to the north-west of the central urban sector centered on Grey Lynn; and in the eastern parts of the central sector from Glenn Innes to Onehunga.  相似文献   
993.
994.
The effects of intracerebral implants of 17 beta estradiol and cholesterol in five brain regions were tested on the duration of the dorsal immobility response in ovariectomized female rats. The dorsal immobility response was significantly prolonged by 4-hr implants of 17 beta estradiol in the dorsal striatum and nucleus accumbens, but not in the cortex, the globus pallidus, or the substantia nigra pars compacta. These data further support previous evidence that estradiol acts directly on the striatum to affect behavior in the rat.  相似文献   
995.
D J Harris  G O Waring  L L Burk 《Ophthalmology》1989,96(11):1597-1607
After penetrating keratoplasty in 52 eyes, keratography refraction and keratometry were used to select appropriate interrupted sutures for removal in order to reduce astigmatism. All eyes had one continuous and either 12 or 16 interrupted nylon sutures. The keratographs were examined retrospectively and separated into six groups on the basis of similar mire patterns. The removal of single sutures associated with three of these patterns reduced astigmatism by the following average amounts: symmetrical oval pattern, 0.44 diopters (D); D-shaped oval pattern, 2.07 D; and focal indentation pattern, 6.60 D. The other three patterns--mildly disrupted mires, incomplete mires, and uninterpretable mires--did not allow quantification of results. Examples of these keratographic patterns are presented and recommendations are made for their use in the management of astigmatism following penetrating keratoplasty.  相似文献   
996.
N-Hydroxythalidomide (1d), a potential metabolite of thalidomide (1a), was synthesized from N-phthalyglutaminic acid anhydride (1b) and O-tetrahydropyraline hydroxylamine, followed by deprotection. The teratogenicity of 1d was studied using the Hen's-Egg-Test model which had been found applicable for 1a. 1d was more teratogenic to chicken embryos compared to 1a. The percentage of teratogenic malformations in the 1d groups was 28-46%, whereas the percentage in the 1a groups was 20-23%. The oxygen protected precursor N-hydroxythalidomide (1c) was less teratogenic (11-15%).  相似文献   
997.
Two antifungal antibiotics maniwamycins A and B were isolated from the culture broth of a strain of actinomycetes, which were classified as Streptomyces prasinopilosus. These antibiotics were isolated by resin absorption and extraction with EtOAc and purified by column chromatography. Both antibiotics were found to be new azoxy substances from their physico-chemical properties. They showed broad antifungal spectra.  相似文献   
998.
A series of new 4-aryl-5-[omega-(4-aryl-1-piperazinyl)alkyl]-2(3H)- oxazolones was synthesized and tested for neuroleptic activity in mice and rats. Several compounds exhibited interesting neuroleptic activity with very low liability to the extrapyramidal side effects. In particular the activity of 4-(4-fluorophenyl)-5-[2-[4-(3,5-dichlorophenyl)-1- piperazinyl]ethyl]-2(3H)-oxazolone (14) was greater than that of butropipazone and fluanisone, while of the same order of that of chlorpromazine; however, the product showed a longer lasting activity and minor ability to produce catalepsy as compared with the reference drugs.  相似文献   
999.
Mycobacterium ulcerans infection in Ashanti region, Ghana   总被引:1,自引:0,他引:1  
We describe a series of 96 cases of Mycobacterium ulcerans infection (Buruli ulcer) from a new endemic focus in the Afram valley, north of Agogo, in Ghana. 63 cases were children under 13 years old. Active treatment by excision and skin grafting necessitates long stays in hospital and repeated procedures. Scarring and contracture are frequent. Eyes and other vital organs may be destroyed. In its endemic foci Buruli ulcer is a serious health burden on rural populations. Research is urgently needed, especially in prevention and non-surgical management.  相似文献   
1000.
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