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   1006869篇
  免费   71819篇
  国内免费   1568篇
耳鼻咽喉   13812篇
儿科学   26336篇
妇产科学   24392篇
基础医学   143030篇
口腔科学   29098篇
临床医学   88560篇
内科学   198960篇
皮肤病学   20097篇
神经病学   79634篇
特种医学   39746篇
外国民族医学   79篇
外科学   163867篇
综合类   18899篇
现状与发展   1篇
一般理论   325篇
预防医学   67608篇
眼科学   23113篇
药学   77681篇
  3篇
中国医学   2243篇
肿瘤学   62772篇
  2021年   7759篇
  2019年   7959篇
  2018年   11259篇
  2017年   8685篇
  2016年   9499篇
  2015年   10905篇
  2014年   14946篇
  2013年   21269篇
  2012年   30078篇
  2011年   31255篇
  2010年   18216篇
  2009年   17287篇
  2008年   29614篇
  2007年   30879篇
  2006年   31292篇
  2005年   30164篇
  2004年   28887篇
  2003年   27616篇
  2002年   26791篇
  2001年   55344篇
  2000年   56982篇
  1999年   47547篇
  1998年   11510篇
  1997年   10042篇
  1996年   10068篇
  1995年   9338篇
  1994年   8677篇
  1993年   7996篇
  1992年   35783篇
  1991年   34142篇
  1990年   32949篇
  1989年   32074篇
  1988年   29186篇
  1987年   28417篇
  1986年   26467篇
  1985年   25356篇
  1984年   18054篇
  1983年   15324篇
  1982年   8040篇
  1979年   15906篇
  1978年   10739篇
  1977年   9176篇
  1976年   7969篇
  1975年   8716篇
  1974年   10531篇
  1973年   9925篇
  1972年   9415篇
  1971年   8908篇
  1970年   8460篇
  1969年   7966篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Abstract. During the 1997 Congress on Gerontology the issue of advocacy was prominently raised in numerous sessions. The delegates affirmed the Declaration of Adelaide, an important statement which called attention to the policy implications of scientific findings. The Declaration set research, practice and education agendas and urged increased resources for gerontological research and programs affecting the well-being of older persons and their families. The wisdom of “linking what we know and can do with what we hope for and desire,” as the theologian Jurgen Moltman has written, requires a systematic effort on the part of gerontologists to influence public policy, standards and professional practice. In short, gerontologists must become advocates. To be effective advocates they must raise awareness of critical issues, form coalitions with those who share the goal of a better world, and exchange information and best practices if the elders of society today - and those who will be the elders of tomorrow - are to benefit from science translated into sound policies and effective practices. Gerontologists must take their scientific findings - and questions - to the forums where policies are discussed and standards and practices developed.  相似文献   
992.
During the years 1979–1986, a cohort of direct entrantexecutive officers in the Civil Service were followed up toexamine the prevalence and outcome of minor psychiatric morbidityin an occupational setting. All studies using epidemiologicalstandardized research methods agree, that prevalence rates arehigh in occupational settings. As in primary care settings,half of the illness episodes followed a chronic course, whichemphasizes the need for early detection and prompt managementof these conditions, and for evaluative studies of interventionstrategies.  相似文献   
993.
There are conflicting reports on the relationship between cerebellar vermal lobule hypoplasia and autism. Using quantitative magnetic resonance image analysis, we measured the cerebellar vermis in 125 normal individuals with a broad age range and 102 patients with a variety of neurogenetic abnormalities. We conclude that hypoplasia of cerebellar vermal lobules VI and VII is a nonspecific finding that even occurs in several conditions without autistic behavior. This suggests that it is not a specific neuroanatomical marker for autism, nor is cerebellar dys- genesis likely to be solely responsible for clinical autistic behaviors.  相似文献   
994.
Extracellular single-unit recordings were made in somatosensory cortical barrels of fentanyl-sedated rats. Whiskers were deflected singly or in paired combinations. lontophoretically-applied (−)-baclofen disproportionately reduced weak responses, and phaclofen disproportionately increased them, resulting in more tightly focused or more broadly focused receptive fields, respectively. Both drugs had only minor effects on surround inhibition. In light of previous findings, we conclude that GABAA and GABAB mechanisms both act to enhance spatial contrast, but that the former plays a much greater role in enhancing temporal resolution.  相似文献   
995.
Proliferative activity of mast cells in allergic nasal mucosa   总被引:4,自引:1,他引:3  
The proliferative activity of mast cells in the nasal mucosae of allergic (n= 14) and non-allergic (n= 18) rhinopathic patients was studied by a sequential double immuno-histochemistry using anti-proliferating cell nuclear antigen (PCNA) and anti-tryptase antibodies. Two hundred to 300 tryptase-positive cells (mast cells) were studied in each allergic nasal epithelium. In case of non-allergic nasal mucosa, only a few mast cells existed in the epithelial layer. The total number of mast cells which we could detect in all patients was 168 cells. One of these cells contained PCNA. Three hundred to 500 mast cells were studied in each subepithelial layer and deep layer of lamina propria of both diseases. PCNA-positive mast cells were observed in the nasal epithelia of 10 allergic patients. In the subepithelial layer, PCNA-positive mast cells were observed eight allergic patients and four non-allergic patients, respectively, In the deep lamina propria, PCNA-positive mast cells were observed in a few patients with both diseases. The percentage of PCNA-positive mast cells of all mast cells each area ranged from 0 to 1.7%. The incidence of PCNA-positive mast cells was statistically higher in the allergic epithelium and subepithelial layer than in the deep layer of lamina propria. Moreover, that of PCNA-positive mast cells in the subepithelial layer was higher in allergic than in non-allergic nasal mucosa. Our results suggest that mast cell proliferation may contribute to the number of mast cells in the nasal epithelium and subepithelial layer of allergic patients.  相似文献   
996.
We report improvement in muscle strength in a patient with multifocal motor neuropathy (MMN) when given high-dose intravenous immunoglobin (i.v.-Ig) treatment. The patient had asymmetrical limb weakness, atrophy and absent or weak reflexes, but no sensory disturbances. Neurography showed multiple conduction blocks in peripheral motor nerves but no sensory nerve abnormalities. Serum and anti-GM1 antibodies were not found, however, the patient had serum antibodies against the glycolipid LK1, an epitope found both in glycolipid and also in some glycoproteins in peripheral nerve myelin. Muscle strength improved 5 days after i.v.-Ig therapy, and lasted about 10 weeks. Repeated courses of treatment resulted in similar improvement. This is, to our knowledge, the first patient reported with MMN found to have antibodies against the glycolipid LK1.  相似文献   
997.
Fluctuating PEEP (F-PEEP) is a newly developed PEEP in which end-expiratory pressure (EEP) is periodically changed within a certain range. In a dog model with unilateral lung injury induced by the introduction of hydrochloric acid, F-PEEP in which the EEP was periodically changed from 0.5 to 1.5 kPa at periods of 6 min, and conventional PEEP (C-PEEP) with an optimized EEP of 1.0 kPa, were each applied for 30 min. F-PEEP produced a significantly greater improvement of PaO2 and intrapulmonary shunt (QS/QT) than C-PEEP, and at the low EEP phase, the greatest improvement accompanied by an increased dynamic compliance and a large cardiac output was obtained. These results suggest that F-PEEP provides a useful mode of artificial ventilation for the treatment of unilateral lung injury.  相似文献   
998.
Tablets of either microsized or ultramicrosized griseofulvin (2 x 125 mg), were administered to 6 healthy volunteers of either sex just before a breakfast containing 4o g. of butter. The plasma concentration of griseofulvin were determined 1, 3, 5, 7, 9, 24, and 32 h. after dosing using a spectrofluorometric method, and pharmacokinetic parameters (Cp max, t max, AUC 0 - greater than 32) were calculated. These parameters were found to be; Cp max = 0.0.681 +/- 0.1 mu/ml, t max. = 2.51 +/- 0.33 h. and AUC = 14.14 +/- 2.33 micrograms h/ml for microsized tablets and Cp max = 0.80 +/- 0.08 +/- g/ml, t max = 2.44 +/- 0.54 and AUC = 16.25 +/- 1.16 microgram h/ml for ultramicrosized tablets. Our results show that mean peak plasma level and AUC (0 - greater than 32) are only slightly higher for the ultramicrosized preparation and the time to peak plasma level is similar in two preparations. Therefore, it is concluded that coadministration of griseofulvin with food will tend to reduce the difference between the bioavailability of the two type of preparations.  相似文献   
999.
Sarafotoxins (SRTa, SRTb and SRTc) and ET-1 produced a potent vasodilator effect in spontaneously hypertensive rats in vivo and in rat isolated perfused mesenteries in vitro. Among these peptides SRTc demonstrated the most potent vasodilator activity, and was three times more active than SRTa in both preparations. These peptides induced endothelium-dependent vasodilatation in vitro and pretreatment with methylene blue inhibited this effect, while exposure to the antagonists of other vasodilators did not. In contrast, [nitrophenylsulfenylated Trp21]SRTc, SRTc(1-18) and reduced and S-carboxymethylated SRTc caused no vasodilatation in either animal model; the vasodilator effect of acetylated SRTc was less potent than that of SRTc. These results suggest that (i) the vasodilatations of these peptides may be exerted through the release of endothelium derived relaxing factor; (ii) the C-terminal Trp21 and disulfide bonds are essential; and (iii) the N-terminal amino group plays an important role in vasodilator activity.  相似文献   
1000.
We studied the effects of drugs used for treatment of bladder dysfunction in conscious rats with intact pelvic nerves and also in rats at one or two weeks after nerve decentralization on the left side. Bladder contraction accompanying micturition was continuously induced by infusion of solution at a constant rate. When the effects of oxybutynin (3 mg/kg, i.p.) and terodiline (3 and 10 mg/kg, i.p.) on the cystometrogram were studied for about 2 hr, these drugs shortened and then prolonged the micturition interval (MI), but atropine (1 and 5 mg/kg, i.p.), butylscopolamine (20 mg/kg, i.p.) and nifedipine (3 mg/kg, i.p.) exhibited only a shortening effect on the MI. After injection of oxybutynin (10 mg/kg, i.p.), solution dribbled from the urethra for about 30 min. Terodiline (3 mg/kg) caused ischuria in the rats one week after resection of the left pelvic nerve, but not in the rats two weeks after surgery. Physostigmine (0.3 mg/kg, i.p.) improved micturition in the rats one week after surgery, but the effect was not evident in the rats with intact pelvic nerves. It was found that the drugs used for treating failure to store or expel urine exhibited a beneficial effect on micturition in rats with intact pelvic nerves and also in rats one week after nerve decentralization, respectively.  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