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   22683篇
  免费   1779篇
  国内免费   33篇
耳鼻咽喉   195篇
儿科学   774篇
妇产科学   621篇
基础医学   2804篇
口腔科学   397篇
临床医学   2764篇
内科学   4041篇
皮肤病学   395篇
神经病学   2094篇
特种医学   701篇
外科学   3292篇
综合类   362篇
一般理论   38篇
预防医学   2368篇
眼科学   546篇
药学   1598篇
  3篇
中国医学   12篇
肿瘤学   1490篇
  2022年   156篇
  2021年   373篇
  2020年   221篇
  2019年   409篇
  2018年   466篇
  2017年   335篇
  2016年   376篇
  2015年   397篇
  2014年   591篇
  2013年   898篇
  2012年   1328篇
  2011年   1443篇
  2010年   750篇
  2009年   679篇
  2008年   1159篇
  2007年   1207篇
  2006年   1205篇
  2005年   1103篇
  2004年   1043篇
  2003年   1024篇
  2002年   903篇
  2001年   511篇
  2000年   542篇
  1999年   461篇
  1998年   250篇
  1997年   173篇
  1996年   186篇
  1995年   182篇
  1994年   142篇
  1993年   161篇
  1992年   420篇
  1991年   367篇
  1990年   379篇
  1989年   349篇
  1988年   359篇
  1987年   326篇
  1986年   307篇
  1985年   333篇
  1984年   260篇
  1983年   219篇
  1982年   149篇
  1981年   126篇
  1980年   121篇
  1979年   237篇
  1978年   172篇
  1977年   124篇
  1976年   116篇
  1974年   119篇
  1973年   128篇
  1970年   116篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The effects of continuous therapy with hydrochlorothiazide and spironolactone on pulmonary function in 34 premature infants with severe bronchopulmonary dysplasia were assessed in a randomized double-blind controlled trial. Subjects were greater than or equal to 30 days old, were supported by mechanical ventilation in greater than or equal to 30% oxygen, and had radiographic evidence of bronchopulmonary dysplasia. The treatment group (n = 19) and the placebo group (n = 15) were similar in all respects except for distribution of gender. Anthropometrics, ventilatory measurements, and the results of pulmonary function tests were evaluated at study entry and at 1, 4, and 8 weeks into therapy. Poststudy chest radiographs were compared with those obtained before the study. The proportion of infants alive at discharge was significantly increased (84%) in the treatment group compared with the placebo group (47%) (p = 0.05). There were no statistically significant differences in total hospital days or in total ventilator days. Total respiratory system compliance at 4 weeks was higher in the treatment group (0.61 +/- 0.18) than in the placebo group (0.45 +/- 0.13) (p = 0.016). No difference in outcome was detected between male and female infants in the treatment group. These results suggest that long-term diuretic therapy improves outcome in infants with bronchopulmonary dysplasia.  相似文献   
72.
Four 50 mg and three 100 mg marketed nitrofurantoin tablets were studied in 14 healthy male subjects. Urine was collected 1, 2, 3, 4, 6, 8, 12, and 23 h after each dose, and nitrofurantoin was assayed by HPLC. The in vitro dissolution of the tablets was determined using USP Apparatus 1 and 2, with 0.1 N hydrochloric acid and pH 7.2 buffer as the dissolution fluids. One of the 50 mg tablets was more rapidly and completely absorbed than the other six products. The incidence of side-effects for this product was as low or lower than the other products. It was determined that the use of the USP Apparatus 1, at 100 rev min-1, with sampling of the pH 7.2 fluid at 30 min, provided for the best overall relationship between the urinary excretion and in vitro dissolution.  相似文献   
73.
M B Wood 《Orthopedics》1986,9(6):810-816
Free vascularized bone transfer is recognized as a valuable technique for skeletal reconstruction and salvage with certain nonunions, skeletal defects, and following tumor resection. This procedure is most often indicated for reconstruction of lengthy skeletal defects or under circumstances where conventional bone grafting techniques are unlikely to succeed. Factors affecting selection of donor bone and technical peculiarities relative to the recipient sites are discussed. The results of 49 cases at the Mayo Clinic for management of nonunion, segmental gaps or following tumor resection suggest a union rate of 82%. The most consistent rate of success was found for reconstruction of defects affecting the tibia, mandible or forearm bones.  相似文献   
74.
M J Moore  F C Hay  J Wood    K N Brown 《Immunology》1991,74(1):31-36
A polyclonal anti-idiotype was raised in rabbits following immunization with a murine monoclonal antibody which recognized a 250,000 MW antigen of Plasmodium chabaudi-infected erythrocytes. The monoclonal antibody, NIMP M23 (clone 3,) has been shown to protect mice against homologous parasite challenge. Following purification, the anti-idiotype was shown to bind only the immunizing idiotype and to recognize antigen-binding site-associated anti-idiotype. Mice primed with anti-idiotype and challenged with live parasites had an altered course of infection, with significant reduction in their peak parasitaemia levels. Anti-idiotype priming did not induce an antigen-reactive antibody response in vivo but a population of T cells capable of proliferating in vitro to P. chaubaudi-infected red cells was stimulated. These data are discussed in the context of possible idiotypic interaction in murine malaria.  相似文献   
75.
To better understand the development of primary care classifications over the past 15 years, 10 primary care databases have been retrospectively analysed using the structure of the International Classification of Primary Care (ICPC) as the basis. All datasets were based on routine data collection using different classification systems by several family physicians during all encounters with their patients over considerable periods of time, in most cases one year. The prevalences or the rates of the available diagnostic--and reason for encounter--classes were distributed over four frequencies. With a few exceptions the distribution of diagnostic labels referring to common diseases is surprisingly similar. The use of ICPC however results in a quantum leap in the use of symptom and complaint diagnoses. Because of this shift primary care physicians now have available a classification with 400 diagnostic classes used with a prevalence of > or = 1/1000 patient-years or per 1000 visiting patients per year. The classification of reasons for encounter allows the physician to identify over 300 reasons for encounter used > or = 1/1000 patient years or per 1000 visiting patients per year. Family physicians have been successful in the development of new primary care classifications. Rag bag rubrics which are the result of the structure of ICPC are used relatively often and deserve more attention from primary care taxonomers.  相似文献   
76.
An immunochemical analysis was conducted to compare the C1 isomer of human myelin basic protein (MBP) with the newly described and less cationic, citrullinated isomer of MBP referred to as C8. Ten polyclonal antisera directed at multiple epitopes or restricted regions of MBP were used in radioimmunoassays to examine MBP-C1 and MBP-C8. Antisera reactive with MBP peptide 1-14 clearly distinguished MBP-C1 from MBP-C8. Antisera to human MBP peptides 10-19 and 90-170, but not to MBP peptide 69-89, showed modest differences between MBP-C1 and MBP-C8. The MBP-C8s from multiple sclerosis (MS) and non-MS brain reacted essentially the same. With murine monoclonal antibodies and enzyme-linked immunosorbent assay (ELISA), differences between MBP-C8 and other isomers were shown for anti-MBP 10-19 but not for anti-MBP 1-9 or anti-MBP 80-89. These findings imply differences in sequence or conformation in the structure of MBP-C7 compared to MBP-C1, most notably near the amino terminus.  相似文献   
77.
Methylazoxymethanol acetate (MAM) is a mitotic inhibitor that has been used to selectively destroy neuroblasts at specific times during gestation. The administration of MAM results in a dose-dependent microencephaly. Following MAM treatment at 15 days of gestation, we have noted an increase in the level of SS immunoreactivity in the neocortex, as determined by radioimmunoassay. Northern blot analysis for preproSS mRNA revealed an increase in MAM-treated cortex. The cellular distribution of SS has been determined using in situ hybridization and immunocytochemistry. There was a 30% increase in the density of SS-immunoreactive neurons in the cortex of the MAM-treated animals. These data suggest that SS neurons in the cortex are spared following MAM treatment at GD 15.  相似文献   
78.
OBJECTIVE: To determine the feasibility and effectiveness of laparoscopically assisted hysterectomy. DESIGN: A prospective study of the planned surgical procedure was carried out by two teams, each with two gynaecologists, who were experienced in operative laparoscopy. SETTING: The operations were carried out in a private hospital, where advanced operative laparoscopy equipment was available. PATIENTS: Seventeen patients were selected for the procedure, all of whom required hysterectomy for symptoms of pain or menorrhagia in association with uterine or other pelvic disease. Patients with carcinoma or uterine enlargement beyond 12 cm were excluded. PROCEDURE: Laparoscopically assisted hysterectomy was carried out by means of a video monitor, uterine manipulation by vaginal instrumentation, three or four abdominal punctures of less than 1 cm, and bipolar diathermy to secure vascular pedicles. The uterus was removed from the vagina by cutting vaginal skin and the cardinal ligaments. RESULTS: The operating time was 90-220 min, the blood loss was 30-200 mL, and the hospital stay lasted two to five days and convalescence two to four weeks. No serious complications occurred. CONCLUSIONS: Laparoscopically assisted hysterectomy may be valuable when adnexal or uterine abnormalities are present and vaginal hysterectomy is either contraindicated or more difficult. The procedure requires special equipment and may only be carried out by experienced gynaecological operative laparoscopists. Its acceptance will depend upon reducing the operating time to less than 90 min. It has the advantage of reducing the duration of hospital stay and the duration of convalescence when compared with abdominal hysterectomy.  相似文献   
79.
This study was designed to address the question; does expression of paternal histocompatibility antigens by fetal cells make them susceptible to immune attack in vivo during normal pregnancy? The experimental design was based on the rationale that, if alloantigens are presented by trophoblasts or other fetal cells in a manner which allows accessibility, in vitro-generated immune effector cells of combined helper/cytotoxic phenotype should produce fetal rejection of abortion. Similarly generated effector cells are capable of accelerating skin graft rejection and, when combined with IL-2 in vivo, are capable of causing regression of antigenic, but operationally non-immunogenic, tumors. The alloimmune effector cells generated in vitro during the current study were highly cytotoxic against normal adult target cells, whereas placental cells were completely resistant to cytolysis and fetal cells were only slightly susceptible. Adoptive transfer of effector cells to mice at different stages of gestation had no apparent effect on pregnancy outcome. In vivo administration of IL-2 and/or indomethacin, which expand effector cell numbers in vivo and block PGE2-mediated immune suppression, respectively, failed to potentiate the cellular effect. The data provide additional evidence that paternal histocompatibility antigens are not expressed in a format which allows susceptibility to immune attack during pregnancy. The data are discussed with respect to the role of the trophoblast in protecting developing embryos.  相似文献   
80.
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