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   809篇
  免费   107篇
  国内免费   15篇
耳鼻咽喉   2篇
儿科学   46篇
妇产科学   11篇
基础医学   121篇
口腔科学   15篇
临床医学   87篇
内科学   157篇
皮肤病学   9篇
神经病学   111篇
特种医学   77篇
外科学   86篇
综合类   49篇
一般理论   1篇
预防医学   34篇
眼科学   29篇
药学   58篇
肿瘤学   38篇
  2021年   12篇
  2019年   12篇
  2018年   7篇
  2015年   7篇
  2014年   12篇
  2013年   19篇
  2012年   16篇
  2011年   24篇
  2010年   16篇
  2009年   16篇
  2008年   14篇
  2007年   30篇
  2006年   21篇
  2005年   36篇
  2004年   21篇
  2003年   22篇
  2002年   17篇
  2001年   24篇
  2000年   27篇
  1999年   16篇
  1998年   20篇
  1997年   19篇
  1996年   10篇
  1995年   14篇
  1994年   12篇
  1993年   15篇
  1992年   32篇
  1991年   30篇
  1990年   18篇
  1989年   17篇
  1988年   32篇
  1987年   39篇
  1986年   27篇
  1985年   16篇
  1984年   19篇
  1983年   7篇
  1982年   13篇
  1981年   8篇
  1980年   21篇
  1979年   20篇
  1978年   15篇
  1977年   11篇
  1976年   7篇
  1975年   9篇
  1974年   10篇
  1973年   6篇
  1972年   8篇
  1971年   8篇
  1970年   10篇
  1969年   8篇
排序方式: 共有931条查询结果,搜索用时 15 毫秒
1.
2.
Hereditary neuropathy with liability to pressure palsies (HNPP; also called tomaculous neuropathy) is an autosomal-dominant disorder that produces a painless episodic, recurrent, focal demyelinating neuropathy. HNPP generally develops during adolescence, and may cause attacks of numbness, muscular weakness, and atrophy. Peroneal palsies, carpal tunnel syndrome, and other entrapment neuropathies may be frequent manifestations of HNPP. Motor and sensory nerve conduction velocities may be reduced in clinically affected patients, as well as in asymptomatic gene carriers. The histopathological changes observed in peripheral nerves of HNPP patients include segmental demyelination and tomaculous or “sausage-like” formations. Mild overlap of clinical features with Charcot-Marie-Tooth (CMT) disease type 1 (CMT1) may lead patients with HNPP to be misdiagnosed as having CMT1. HNPP and CMT1 are both demyelinating neuropathies, however, their clinical, pathological, and electrophysiological features are quite distinct. HNPP is most frequently associated with a 1.4-Mb pair deletion on chromosome 17p12. A duplication of the identical region leads to CMT1A. Both HNPP and CMT1A result from a dosage effect of the PMP22 gene, which is contained within the deleted/duplicated region. This is reflected in reduced mRNA and protein levels in sural nerve biopsy samples from HNPP patients. Treatment for HNPP consists of preventative and symptom-easing measures. Hereditary neuralgic amyotrophy (HNA; also called familial brachial plexus neuropathy) is an autosomal-dominant disorder causing episodes of paralysis and muscle weakness initiated by severe pain. Individuals with HNA may suffer repeated episodes of intense pain, paralysis, and sensory disturbances in an affected limb. The onset of HNA is at birth or later in childhood with prognosis for recovery usually favorable; however, persons with HNA may have permanent residual neurological dysfunction following attack(s). Episodes are often triggered by infections, immunizations, the puerperium, and stress. Electrophysiological studies show normal or mildly prolonged motor nerve conduction velocities distal to the affected brachial plexus. Pathological studies have found axonal degeneration in nerves examined distal to the plexus abnormality. In some HNA pedigrees there are characteristic facial features, including hypotelorism. The prognosis for recovery of normal function of affected limbs in HNA is good, although recurrent episodes may cause residual deficits. HNA is genetically linked to chromosome 17q25, where mutations in the septin-9 (SEPT9) gene have been found.  相似文献   
3.
Thirteen new 1-ethyl-6-fluoro-1,4-dihydro-4-oxo-7-(4-aroyl-thiocarbamoyl- 1 piperazinyl)-3-quinoline carboxylic acids were prepared, Their structures were characterized by elemental analysis, IR, HNMR and MS spectra.Preliminary pharmacological tests indicated that some of compounds Ia~m possess strong inhibiting activity against Escherichia coli, Bacillus subtilis and Proteus at concentration of 100 μg/ml.  相似文献   
4.
5.
6.
This article concludes that there is a tremendous need for gifted programs at the kindergarten and first grade levels. A review of the literature suggests that it is difficult to identify young gifted children through traditional screening techniques. The author concludes that Renzulli's Enrichment Triad Model may prove useful for identifying young gifted children.  相似文献   
7.
OBJECTIVE: To determine whether perinatal care in southwestern Ontario is regionalized, to identify trends over time in referral patterns, to quantify trends in perinatal death rates and to identify trends in perinatal death rates that give evidence of regionalization. DESIGN: Cohort study. SETTING: Thirty-two hospitals in southwestern Ontario (1 level III, 1 modified level III and 30 level II or I). PATIENTS: All pregnant women admitted to the hospitals and their infants. MAIN OUTCOME MEASURES: Antenatal and neonatal transfer status, live-born with discharge home alive from hospital of birth, stillborn, and live-born with death before discharge. RESULTS: Between 1982 and 1985 the antenatal transfer rate increased from 2.2% to 2.8% (p less than 0.003). The proportion of births of infants weighing 500 to 1499 g increased from 49% to 69% at the level III hospital. The neonatal transfer rate increased from 26.2% to 47.9% (p less than 0.05) for infants in this birth-weight category and decreased from 10.2% to 7.1% (p less than 0.03) for infants weighing 1500 to 2499 g. The death rate among infants of low birth weight was lowest among those born at the level III centre and decreased at all centres between 1982 and 1985. CONCLUSIONS: Perinatal care in southwestern Ontario is regionalized and not centralized; regionalization in southwestern Ontario increased between 1982 and 1985.  相似文献   
8.
9.
W T Chance  L Cao    J E Fischer 《Annals of surgery》1988,208(4):524-531
The effect that a 14-day treatment program of total parenteral nutrition (TPN) combined with the glutamine antimetabolite, acivicin, and anabolic hormone, insulin, has on carcass weight and muscle sparing was investigated in tumor-bearing rats. Although TPN resulted in increased carcass weight gain as compared to chow-fed tumor-bearing rats, no savings in gastrocnemius muscle could be demonstrated. The combination of TPN with daily insulin treatment elicited significant increases in both carcass weight and muscle savings, with no alteration in tumor growth. Although combining acivicin with TPN halted tumor growth and increased carcass weight, the change in carcass weight was less than that observed with the insulin-TPN combination. No muscle savings were observed in the acivicin-TPN-treated rats. Yet when acivicin and insulin were combined with TPN, tumor growth was stopped, carcass weight was gained, and muscle mass was saved. Therefore, these experiments suggest that it is possible to add lean body tissue and stabilize tumor growth in rats that receive TPN through anabolic hormone treatment combined with an inhibitor of tumor metabolism.  相似文献   
10.
The edge-spread function that is expected when imaging a sharp edge in a highly scattering medium using a time-of-flight imaging system has been investigated. Experimental results have been compared with computer simulations. The effect of scattering is to broaden the image of the edge, accompanied by an offset of the midpoint (50% transmission) of the edge. Small random errors in the measurement of the time of flight results in an increase in the offset of the edge position at very short times of flight. The offset in the midpoint of the edge is evidence of the nonlinear nature imaging process, in view of which we conclude that nonlinear algorithms will be necessary to maximize the image information available from measured intensities.  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