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   872篇
  免费   1篇
电工技术   2篇
化学工业   15篇
建筑科学   2篇
能源动力   2篇
轻工业   4篇
无线电   1篇
一般工业技术   17篇
冶金工业   822篇
自动化技术   8篇
  2023年   1篇
  2022年   5篇
  2021年   3篇
  2020年   3篇
  2019年   3篇
  2018年   3篇
  2017年   1篇
  2014年   1篇
  2013年   3篇
  2012年   3篇
  2011年   3篇
  2009年   1篇
  2008年   2篇
  2006年   2篇
  2005年   4篇
  2004年   2篇
  2003年   6篇
  1999年   23篇
  1998年   261篇
  1997年   136篇
  1996年   86篇
  1995年   41篇
  1994年   37篇
  1993年   57篇
  1992年   8篇
  1991年   16篇
  1990年   7篇
  1989年   12篇
  1988年   11篇
  1987年   17篇
  1986年   11篇
  1985年   12篇
  1984年   1篇
  1983年   2篇
  1982年   2篇
  1981年   7篇
  1980年   4篇
  1978年   5篇
  1977年   24篇
  1976年   39篇
  1975年   4篇
  1968年   3篇
  1954年   1篇
排序方式: 共有873条查询结果,搜索用时 15 毫秒
61.
The inclusion of people with developmental disabilities in managed care as part of general efforts by states to enroll and Medicaid recipients in such plans was reviewed. Managed care was defined and the processes by which managed care organizations deliver services were explained. Escalating costs and utilization were discussed as the primary reason for the shift to managed care. The use of Medicaid Section 1115 waivers by states to include Medicaid recipients was explored. The relation between acute health care and long-term care, and the utilization patterns in each, were briefly described. Finally, elements of managed care that are particularly important to people with developmental disabilities, such as care coordination, maintenance of quality, and individual and family support, were discussed.  相似文献   
62.
63.
Bone tumors of the coracoid process of the scapula are rare, and diagnosis and treatment often are delayed. The records of 18 patients with bone tumors of the coracoid process were reviewed. Histologic types included eight cases of ordinary chondrosarcoma, three cases of dedifferentiated chondrosarcoma, two cases of osteoid osteoma, and one case each of osteosarcoma, plasmacytoma, lymphoma, giant cell tumor, and aneurysmal bone cyst. All 18 patients had shoulder pain, and eight of them had been treated with steroid injections for nonneoplastic conditions. Radiologically, chondrosarcoma did not always show clear cortical destruction, and one giant cell tumor had features mimicking those of chondrosarcoma. Five patients (three with dedifferentiated chondrosarcoma, one with chondrosarcoma, one with plasmacytoma) died of disease. The coracoid process was the site with a markedly high proportion of chondrosarcomas. Bone tumors of the coracoid process may be difficult to detect on plain radiographs. In the patient with persistent shoulder pain unresponsive to the selected treatment, additional imaging studies should be considered to eliminate the possibility of a bone lesion.  相似文献   
64.
BACKGROUND: Epidemiologic studies have demonstrated strong and consistent associations between the detection of human papillomavirus (HPV) type 16 DNA and the risk of cervical intraepithelial neoplasia (CIN) and cervical cancer. However, HPV16 is also the most common type of HPV in the normal population, and only a minority of women with HPV16 infection develop cervical cancer. Studies of genomic heterogeneity in HPV16 have demonstrated the presence of multiple variant forms in all human populations examined to date. It is conceivable that the natural variants of HPV16 in a given population may not have the same biologic behavior. PURPOSE: This study was designed to determine the association between natural variants of HPV16 and the risk of biopsy-confirmed CIN 2 or 3, the most important precancerous lesions of the uterine cervix. METHODS: Prospective studies were conducted among 1) women attending a university and 2) women presenting to a sexually transmitted disease clinic. Subjects were eligible for inclusion in this investigation if the initial cytologic findings did not reveal CIN 2-3 and HPV16 DNA was detected by means of a polymerase chain reaction (PCR)-based method in one or more cervical or vulvovaginal samples. Eligible subjects were followed every 4 months with cervical Pap smears and colposcopic examinations. Women were referred for biopsy if cytology or colposcopy suggested CIN 2-3. Two groups of HPV16 variants, prototype-like and nonprototype-like, were determined by means of single-strand conformation polymorphism (SSCP) analysis of PCR products from the noncoding region of the viral genome. Representative SSCP patterns from HPV16 variants were further characterized by direct DNA sequencing of the PCR products. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated by Cox regression analysis. RESULTS: Prototype-like variants accounted for 79% of the HPV16 detected in university students and 86% of the virus detected in patients presenting to the sexually transmitted disease clinic. CIN 2-3 was confirmed by biopsy in nine of 57 HPV16-positive women attending the university and in 10 of 66 HPV16-positive women presenting to the sexually transmitted disease clinic. Among university students, those with HPV16 nonprototype-like variants were 6.5 (95% CI = 1.6-27.2) times more likely to develop CIN 2-3 than those with prototype-like variants. A similar association was observed among women presenting to the sexually transmitted disease clinic (RR = 4.5; 95% CI = 0.9-23.8). CONCLUSIONS: This study suggests that the risk of developing CIN 2-3 is not the same with all variants of HPV16 and that nonprototype-like variants confer a greater risk compared with prototype-like variants. The important genomic differences underlying this increased risk of CIN 2-3 remain to be determined.  相似文献   
65.
Our purpose is to review recent data and provide a clinical opinion on the use of antibiotics to prevent preterm birth or related maternal-neonatal complications. A literature review and a synthesis of opinion are provided. During prenatal care, standard practices should be applied regarding Neisseria gonorrhoeae, Chlamydia trachomatis, and bacteriuria. In addition, screen for and treat bacterial vaginosis in patients at high risk for preterm birth but do not treat Ureaplasma urealyticum or group B streptococci genital colonization. With preterm labor and intact membranes, standard practices should be applied regarding group B streptococci prophylaxis. Do not give antibiotics routinely to prolong pregnancy, but in patients with bacterial vaginosis and Trichomonas vaginalis specific treatment should be given. With preterm premature rupture of membranes, standard practices should be applied regarding group B streptococci prophylaxis, but additional antibiotics should also be given to prolong pregnancies at 24 to 32 weeks' gestation. Reported adverse effects have been few to date. However, increased diligence is needed for resistant organisms. In selected clinical settings antibiotic therapy is now indicated to prolong pregnancy and prevent maternal-neonatal complications associated with preterm birth.  相似文献   
66.
BACKGROUND: Ethnic and/or racial differences in drug response to antihypertensive agents have been recognized, yet the prescribing practices and the information on efficacy of various agents rely mainly on the response of whites to drugs. OBJECTIVES: To assess the management of hypertension in Asian Americans and to compare it with an age- and sex-matched group of white patients with hypertension. METHODS: The patients' medical records were used as the primary source of information for the data collection. The observational period was a 12-month window and included 200 patients of Asian origin with hypertension and 196 white patients with hypertension whose medical records were randomly selected. RESULTS: The study describes the pattern of use of antihypertensive agents and the differences in response to antihypertensive agents between Asian Americans and whites. The preferred antihypertensive agents in both Asian and white patients included monotherapy with either calcium channel blockers or angiotensin-converting enzyme inhibitors. However, medication changes, dose reduction, and the experience of side effects were all significantly more frequently recorded in Asian patients than in white patients (P < .001, P < .008, and P < .002, respectively). CONCLUSIONS: These findings are supportive of some previous reports on ethnic differences in drug response to antihypertensive agents. The findings also point to the need for further prospective studies on the outcome of hypertension management in Asian American patients.  相似文献   
67.
68.
BACKGROUND: Apoptosis maintains cell homeostasis. Altered apoptosis is involved in carcinogenesis. It was our aim to investigate whether reflux esophagitis may alter apoptosis in the esophageal mucosa and whether antireflux surgery may restore normal apoptosis. METHODS: Apoptosis was studied preoperatively and postoperatively in esophageal biopsies of 39 patients with various grades of reflux esophagitis and in Barrett's mucosa using the TUNEL method. Biopsies were also taken from lesions of the squamous epithelium adjacent to the Barrett's mucosa. RESULTS: Apoptosis increased with the severity of esophagitis. Apoptosis was low in Barrett's epithelium. Squamous epithelium adjacent to Barrett's mucosa showed increased apoptosis. After surgery apoptosis decreased in squamous epithelium, and it remained low in Barrett's epithelium. CONCLUSIONS: Apoptosis in reflux esophagitis may be protective against increased proliferation. Low apoptosis following antireflux surgery indicates that surgery is effective to prevent reflux-induced cell proliferation. Inhibition of apoptosis in Barrett's may promote carcinogenesis. This may not change following surgery.  相似文献   
69.
The subcellular distribution of glutathione S-transferase (GST) activity extracted from shoots of 3-day-old etiolated seedlings of maize (Zea mays L., Northrup-King 9283 hybrid) and the induction of soluble and membrane-bound GST activity by the safener benoxacor, the herbicide metolachlor and their combination (CGA-180937) were investigated. GST activity extracted from maize shoots was detected in both cytosolic and microsomal fractions and utilized 1-chloro-2,4-dinitrobenzene (CDNB), metolachlor, and trans-cinnamic acid (CA) as substrates. Soluble GST activity extracted from maize shoots was greater than microsomal with CDNB or metolachlor as substrate. Membrane-bound GST activity was greater than soluble with cinnamic acid as substrate. Washing the microsomal preparations from maize shoots with Triton X-100 increased GST(CA) activity. Pretreatment with the safener benoxacor or a formulated combination of the herbicide metolachlor with benoxacor induced soluble GST(CDNB), GST(metolachlor) and GST(CA) activities in maize shoots. Benoxacor and CGA-180937 induced also membrane-bound GST(CDNB) and GST(CA) activities in maize shoots, but did not affect membrane-bound GST(metolachlor) activity. These results confirm that maize contains multiple GST isozymes that differ in their substrate specificity and inducibility by safeners or other chemicals.  相似文献   
70.
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