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   1674篇
  免费   247篇
  国内免费   21篇
耳鼻咽喉   9篇
儿科学   59篇
妇产科学   28篇
基础医学   103篇
口腔科学   73篇
临床医学   269篇
内科学   441篇
皮肤病学   38篇
神经病学   65篇
特种医学   295篇
外科学   123篇
综合类   18篇
预防医学   295篇
眼科学   11篇
药学   30篇
中国医学   1篇
肿瘤学   84篇
  2023年   49篇
  2022年   15篇
  2021年   21篇
  2020年   42篇
  2019年   24篇
  2018年   55篇
  2017年   33篇
  2016年   44篇
  2015年   56篇
  2014年   99篇
  2013年   121篇
  2012年   37篇
  2011年   51篇
  2010年   63篇
  2009年   81篇
  2008年   48篇
  2007年   74篇
  2006年   50篇
  2005年   37篇
  2004年   44篇
  2003年   15篇
  2002年   15篇
  2001年   28篇
  2000年   24篇
  1999年   30篇
  1998年   65篇
  1997年   89篇
  1996年   79篇
  1995年   57篇
  1994年   62篇
  1993年   52篇
  1992年   16篇
  1991年   12篇
  1990年   31篇
  1989年   42篇
  1988年   31篇
  1987年   34篇
  1986年   33篇
  1985年   32篇
  1984年   13篇
  1983年   13篇
  1982年   24篇
  1981年   30篇
  1980年   17篇
  1979年   7篇
  1978年   5篇
  1977年   14篇
  1976年   14篇
  1975年   10篇
  1969年   2篇
排序方式: 共有1942条查询结果,搜索用时 0 毫秒
11.
Seizures are common in advanced stages of immunodeficiency virus (HIV) infection. HIV-infected outpatients and inpatients in the national hospital in Bobo-Dioulasso among whom seizures occurred had been recruited over four years. There were mainly male (30/13) with an average age of 35 years with extremes ranging from 22 to 60 years. New-onset generalised seizures occurred in all cases of cryptococcal meningitis or partial motor secondary generalised in 64% among patients with suspected cerebral toxoplasmosis due to the efficiency of the treatment of the antitoxoplasmic proof. Identified causes such as suspected cerebral toxoplasmosis (65%), suspected tuberculous meningitis (7%) as CSF culture is not available, cryptococcal meningitis (16%) were found in this study. In four cases among 43 patients, no identified causes could be determined. CD4 lymphocytes count which was available in 24 patients was under 200/41 in 74% of the cases. This study indicates clearly that seizures in young adults are strongly associated with focal brain lesions and cerebral toxoplasmosis is becoming an important cause of seizure in tropical area. This should imply a screening of toxoplasmosis with new-onset seizure in young people.  相似文献   
12.
13.
Advances in techniques of molecular biology have made possible the amplification of specific genes from single cells. This has a major clinical application in preimplantation diagnosis of monogenic disorders. However, the incidence of allele specific amplification failure (allele drop out) in heterozygous single cells can lead to misdiagnosis and the transfer of affected embryos. Few studies have been done to investigate the actual cause of allele drop out, although some investigators have succeeded in reducing but not eliminating it. Here we report the efficiency of amplifying both alleles in heterozygous cells lysed according to two different protocols. A total of 177 heterozygous cells from carriers of cystic fibrosis (CF) and haemoglobin C (HbC) were lysed using two different lysis buffers. Interestingly none of the cells that were lysed with sodium dodecyl sulphate/proteinase K showed any example of allele specific amplification failure whereas in those lysed by KOH/dithiothreitol it was present in 17.6 and 4.7% of the CF and HbC cells respectively. Our results suggest that the phenomenon of allele specific amplification failure is at least in part dependent on the lysis buffer used.   相似文献   
14.
In a simulated field trial Bacillus thuringiensis var israelensis (BTI) pellet formulation exhibited an enhanced efficacy with increasing dose. A dosage of 1.0 and 1.5 ppm was most effective under simulated field conditions. In field trials persistence of BTI pellet (1.0 ppm) was observed for 35 days in moderately polluted water collection as compared to 21 days in highly polluted water bodies.KEY WORDS: Bacillus thuringiensis, Malaria, Mosquito control  相似文献   
15.
OBJECTIVE: To compare the effectiveness of three new topical anesthetics that do not contain cocaine (prilocaine-phenylephrine, tetracaine-phenylephrine [tetraphen], and tetracaine-lidocaine-phenylephrine) to that of tetracaine-adrenaline-cocaine (TAC) during laceration repair in children. DESIGN: Prospective, randomized, double-blind clinical trial. SETTING: The emergency department of an urban children's hospital. PARTICIPANTS: Children 1 year of age or older with a laceration /= 5 years of age using a visual analogue scale (VAS). Suture technicians, research assistants, and parents also scored pain using a seven-point Likert scale. In addition, suture technicians completed an anesthetic effectiveness scale. RESULTS: There was consistently no difference demonstrated between the effectiveness of tetraphen and that of TAC for each outcome measure of each observer group. A statistically significant difference was seen among anesthetics when comparing VAS and Likert scale scores of suture technicians and Likert scale scores of research assistants. Based on post hoc analyses, these statistically significant differences were between TAC and prilocaine-phenylephrine (suture technician VAS and Likert scale) and between TAC and tetracaine-lidocaine-phenyl-ephrine (suture technician Likert scale), but not between TAC and tetraphen. When power analyses were performed using alpha = 0.05 and beta = 0.20, it was possible to detect a difference of 1.2 VAS units for each of the observer groups. Based on anesthetic effectiveness scale scores, the three new topical preparations collectively performed significantly better on the face and scalp than on the extremities (relative risk = 1.83; 95% confidence interval 1.20 < relative risk < 2.79). CONCLUSION: This study demonstrated the effectiveness and safety of three new non-cocaine-containing topical anesthetics. Consistently, there was no statistical difference demonstrated between the effectiveness of tetraphen and that of TAC for each outcome measure of each observer group. Tetraphen offers an effective alternative to TAC during laceration repair in children.  相似文献   
16.
Hypospadias trends in two US surveillance systems   总被引:6,自引:0,他引:6  
OBJECTIVE: Hypospadias is a common congenital anomaly, the cause of which is unknown. Unexplained increases in the rates of hypospadias occurred in five European countries in the 1970s and 1980s. We examined data from two birth defects surveillance systems in the United States for evidence of similar trends. METHODOLOGY: The Metropolitan Atlanta Congenital Defects Program (MACDP) provided birth prevalence rates from 1968 to 1993. The nationwide Birth Defects Monitoring Program (BDMP) provided rates from 1970 to 1993. MACDP data are population-based and could be categorized by the severity of the hypospadias. BDMP data allowed analysis of rate trends for the four census regions of the United States. RESULTS: Data from both surveillance systems showed an approximate doubling of hypospadias rates in the 1970s and 1980s. MACDP data showed that the rate of severe cases increased while the ratio of mild to severe cases decreased. BDMP data showed that hypospadias rates increased markedly in all four regions of the United States. CONCLUSIONS: The observed increases are unlikely to be attributable to increased sensitivity of the surveillance systems or the identification of more mild cases by physicians over time, because either trend would have increased rather than decreased the ratio of mild to severe cases. If real, these trends represent the largest number of cases and the first report of an increase in hypospadias rates outside of Europe. Additional investigation of a possible increase in hypospadias rates is warranted.  相似文献   
17.
We have investigated the localization of thrombospondin (TSP), fibrinogen, fibronectin, and von Willebrand factor in human platelets by transmission electron microscopy of antibody-stained ultrathin frozen sections. In negatively stained thin sections, alpha granules were identified on the basis of their smooth, roughly spherical shape, size, single limiting electron-lucent 100 A membrane, and frequent presence of electron-dense nucleoid. In contrast, mitochondria exhibited characteristic double membranes and cristae. Sections were separately stained with affinity-purified polyclonal antibodies to these proteins as well as with three monoclonal anti-TSP antibodies. Antibody specificity was documented in radioimmunoassays, by immunofluorescent cross-blocking, and by staining of bands of appropriate mobility in Western blots of whole platelets. Bound antibody was visualized using a 5-nm colloidal gold-avidin conjugate. In resting cells, staining of virtually all alpha granules was observed for all four proteins. In contrast, consistent staining was absent from other organelles, including plasma membranes, mitochondria, and vacuolar structures that may represent the open canalicular system.  相似文献   
18.
Most radiotherapy (RT) involves the use of high doses (>50 Gy) to treat malignant disease. However, low to intermediate doses (approximately 3–50 Gy) can provide effective control of a number of benign conditions, ranging from inflammatory/proliferative disorders (e.g. Dupuytren''s disease, heterotopic ossification, keloid scarring, pigmented villonodular synovitis) to benign tumours (e.g. glomus tumours or juvenile nasopharyngeal angiofibromas). Current use in UK RT departments is very variable. This review identifies those benign diseases for which RT provides good control of symptoms with, for the most part, minimal side effects. However, exposure to radiation has the potential to cause a radiation-induced cancer (RIC) many years after treatment. The evidence for the magnitude of this risk comes from many disparate sources and is constrained by the small number of long-term studies in relevant clinical cohorts. This review considers the types of evidence available, i.e. theoretical models, phantom studies, epidemiological studies, long-term follow-up of cancer patients and those treated for benign disease, although many of the latter data pertain to treatments that are no longer used. Informative studies are summarized and considered in relation to the potential for development of a RIC in a range of key tissues (skin, brain etc.). Overall, the evidence suggests that the risks of cancer following RT for benign disease for currently advised protocols are small, especially in older patients. However, the balance of risk vs benefit needs to be considered in younger adults and especially if RT is being considered in adolescents or children.  相似文献   
19.
Goldberg David J.  MD  JD 《Dermatologic surgery》2005,31(10):1317-1322
BACKGROUND: Dermatologic surgical techniques have transformed cosmetic surgery over the last two decades. Many of the advances in cutaneous laser surgery, botulinum toxin injections, tumescent liposuction, and the latest filler agents have been evaluated on willing volunteers as part of organized trials under the auspices of an Institutional Review Board (IRB). OBJECTIVES: To review the developmental history of today's IRB and to provide relevance to cosmetic dermatologic research. RESULTS: Although an IRB must evaluate the "voluntariness" of a proposed research protocol, the risk-benefit ratio, particularly of elective cosmetic dermatologic surgical human studies, is of even greater importance. CONCLUSION: As more dermatologic surgeons become involved in clinical research, an understanding of the function and purpose of the IRB has become increasingly important. Research relating to cosmetic dermatologic procedures raises challenging and perplexing problems for an IRB.  相似文献   
20.
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