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   574篇
  免费   78篇
  国内免费   9篇
耳鼻咽喉   6篇
儿科学   13篇
妇产科学   28篇
基础医学   63篇
口腔科学   34篇
临床医学   190篇
内科学   86篇
皮肤病学   1篇
神经病学   19篇
特种医学   32篇
外科学   49篇
综合类   5篇
预防医学   49篇
眼科学   7篇
药学   22篇
中国医学   1篇
肿瘤学   56篇
  2023年   5篇
  2021年   4篇
  2020年   4篇
  2018年   13篇
  2017年   11篇
  2016年   9篇
  2015年   15篇
  2014年   20篇
  2013年   22篇
  2012年   9篇
  2011年   8篇
  2010年   11篇
  2009年   19篇
  2008年   19篇
  2007年   25篇
  2006年   14篇
  2005年   4篇
  2004年   10篇
  2003年   16篇
  2002年   14篇
  2001年   14篇
  2000年   9篇
  1999年   18篇
  1998年   25篇
  1997年   24篇
  1996年   30篇
  1995年   14篇
  1994年   20篇
  1993年   13篇
  1992年   18篇
  1991年   16篇
  1990年   16篇
  1989年   18篇
  1988年   16篇
  1987年   13篇
  1986年   14篇
  1985年   21篇
  1984年   12篇
  1983年   5篇
  1982年   6篇
  1981年   8篇
  1980年   6篇
  1979年   7篇
  1976年   7篇
  1974年   3篇
  1973年   3篇
  1970年   4篇
  1969年   6篇
  1967年   6篇
  1914年   3篇
排序方式: 共有661条查询结果,搜索用时 15 毫秒
11.
Low-socioeconomic-status (SES) Black children have a higher mean blood pressure than most other groups. The antihypertensive effects of a 12-week aerobic exercise program were examined on 11 low-SES Black children, ages 8-12, who had blood pressure above the 95th percentile. A multiple baseline across three groups of children with baseline and exercise conditions was conducted. After the introduction of the exercise program, there were significant decreases in diastolic and systolic blood pressure. Cardiovascular fitness improved concurrently. The results suggest that vigorous exercise can decrease the blood pressure of low-SES hypertensive Black children.  相似文献   
12.
Hallam PJ, Mannucci P, Tripodi A, Bevan D, Laursen B, Tengborn L, Wacey A, Cooper DN. Three novel PROC gene lesions causing protein C deficiency. Clin Genet 1998: 54: 231–233. 0 Munksgaard, 1998
Missense mutations. three of them novel (Am210→Val, Asn248→ Ile, Ah355→Val), were found in the protein c ( PROC ) genes of 7 patients with inherited protein C deficiency associated with venous thrombosis. Comparison with the phenotypic effects of mutations in the analogous residues of factor IX causing hdernophilia B and the use of molecular modelling has provided explanations as to how these lesions might alter either the structure, function or secretion of the protein C molecules encoded.  相似文献   
13.
A cross-reactive monoclonal antibody (mAb), designated 1205, was used to study redistribution, parasitophorous vacuole (PV) incorporation, and in situ antigen production during the intracellular parasite development ofEimeria acervulina andE. tenella. Western-blot analysis of sporozoite preparations showed that the mAb recognized antigenic bands at 55 and 80 kDa. Indirect immunofluorescent antibody (IFA) labeling of sporozoites produced an internal dot pattern. Immunogold electron microscopy (IM) showed labeling of dense granules within sporozoites. The IFA pattern changed to a general-internal label in immature schizonts followed by a surface-tip pattern in mature merozoites both in vitro and in vivo. IM of the asexual stages revealed the same labeling pattern for the in vivo development of both species, and labeling of rhoptries was seen. In vitro, the PV membrane together with amorphous material within the PV was labeled by IFA during schizont development forE. tenella. No IM labeling of either the PV membrane or material within the PV was observed. Sexual stages seen in vivo for both species had the general-internal IFA pattern.  相似文献   
14.
Cesarean section   总被引:1,自引:0,他引:1  
D N Danforth 《JAMA》1985,253(6):811-818
Although the cesarean section rate has increased steadily for the past 12 years, further increase seems unlikely since the indications for performing the operation are already broadly defined. Most of the earlier indications will remain unchanged (eg, the presence of placenta previa and cephalopelvic disproportion). The trend toward vaginal delivery in perhaps 30% to 40% of breech births will probably have no material effect on the number of cesarean sections performed, and the present use of cesarean section for multiple pregnancy will probably continue. The two conditions under which cesarean section rates might become significantly lower are (1) automatic repeat cesarean section (which now accounts for more than 25% of all cesarean sections), a procedure which will probably decline as increasing numbers of such women have vaginal deliveries, and (2) a redefinition of the present midforceps classification, which will permit some of the easy midforceps deliveries from a low level to be performed without the legally abhorrent stigma of mid-forceps delivery. The value of prophylactic antibiotics for women predisposed to infection has now been proved, and further placebo studies to demonstrate this are not warranted. In the past, "type and match 2 units" was a routine prelude to cesarean section, and for every unit of blood transfused to cesarean section patients, some 25 units were cross-matched and held in (unnecessary) readiness. This formula is gradually giving way to type and screen, eliminating countless crossmatches. Because of possible harmful fetal effects, preoperative fluid loading, a necessary part of conduction anesthesia, is changing from the customary 5% glucose to the use of fluids containing no glucose. It has been suggested that conduction anesthesia may not offer unlimited time for cesarean section, as used to be thought. Apgar scores are lower if the time from uterine incision to delivery is longer than three minutes, a diminution that may be a function of the anesthesia or may reflect difficulty in delivery. Cesarean section mortality is much lower than it was in former years, but one may expect from one to two deaths per 1,000 operations. Overall, the maternal mortality from cesarean section per se is probably from three to five times higher than that of vaginal delivery (in one series, 11.5 times higher than vaginal delivery). The incidence of mild, transient respiratory signs in the newborn is higher after cesarean than after vaginal delivery, and the incidence of respiratory distress syndrome is also slightly higher.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
15.
PURPOSE: To determine long-term event-free (EFS) and overall survival (OS) for patients with stage III breast cancer treated with combined-modality therapy. PATIENTS AND METHODS: Between 1980 and 1988, 107 patients with stage III breast cancer were prospectively enrolled for study at the National Cancer Institute and stratified by whether or not they had features of inflammatory breast cancer (IBC). Patients were treated to best response with cyclophosphamide, doxorubicin, methotrexate, fluorouracil, leucovorin, and hormonal synchronization with conjugated estrogens and tamoxifen. Patients with pathologic complete response received definitive radiotherapy to the breast and axilla, whereas patients with residual disease underwent mastectomy, lymph node dissection, and radiotherapy. All patients underwent six additional cycles of adjuvant chemotherapy. RESULTS: OS and EFS were obtained with a median live patient follow-up time of 16.8 years. The 46 IBC patients had a median OS of 3.8 years and EFS of 2.3 years, compared with 12.2 and 9.0 years, respectively, in stage IIIA breast cancer patients. Fifteen-year OS survival was 20% for IBC versus 50% for stage IIIA patients and 23% for stage IIIB non-IBC. Pathologic response was not associated with improved survival for stage IIIA or IBC patients. Presence of dermal lymphatic invasion did not change the probability of survival in clinical IBC patients. CONCLUSION: Fifteen-year follow-up of stage IIIA and inflammatory breast cancer is rarely reported; IBC patients have a poor long-term outlook.  相似文献   
16.
17.
18.
19.
In order to determine their significance during dipyridamole perfusion scintigraphy, symptomatic, ECG, and scintigraphic findings were related to each other, to the hemodynamic response, and to angiographic findings in 73 consecutive patients having coronary angiography within 3 months of scintigraphy. The group having induced "cardiac" pain differed from the group without induced pain only in their higher incidence of induced ischemic ST changes, the "marked" hemodynamic response, and their lower incidence of an "absent" hemodynamic response (all p less than 0.01). Induced ST depression was found only in patients with coronary disease. In this population, dipyridamole-induced pain was a moderately specific marker and induced ST abnormalities a more highly specific marker for coronary disease. However, both were insensitive for coronary disease diagnosis. If induced pain or ST abnormalities in the presence of significant coronary disease were accepted as indicators of ischemia, then scintigraphic abnormalities appeared to be produced by dipyridamole in roughly equal incidence by ischemic and nonischemic mechanisms. Induced ischemia related frequently to an exaggerated hypotensive response with no change in double product, suggesting its cause to be an induced increase in myocardial oxygen demand. Dipyridamole-induced image defects were noted even in the absence of a peripheral hemodynamic response. This indicates that the peripheral response does not always correlate with its central coronary effect and an absent peripheral hemodynamic response does not necessarily invalidate scintigraphic results.  相似文献   
20.
Previous data from this laboratory revealed a rapid (-12h) and unexpectedly long (-30 days) inhibition of pituitary gonadotropin secretion after a single injection of Antide (Nal-Lys GnRH antagonist) in ovariectomized (OVX) monkeys. Although the apparent mechanism of action of Antide is competitive occupancy of GnRH receptors, the etiology of the prolonged action is unknown. Here, we report development of a radioreceptor assay to measure circulating Antide levels to determine the mechanism(s) of its long duration of action. Five long-term OVX monkeys were injected with Antide (3.0 mg/kg). Blood samples were collected daily for 30 days, and thereafter on alternate days until day 60. Following sc or iv Antide injection, peripheral luteinizing hormone (LH) levels declined from 281 +/- 19 ng/ml to 29 +/- 3 ng/ml within one day (P less than 0.05). LH levels slowly recovered to pretreatment levels within 35 +/- 7 days. Peripheral Antide levels were 16,531 +/- 4,432 ng/ml within 15 minutes following iv injection, and 52 +/- 21 ng/ml at 1 day after sc Antide injection. Interestingly, thereafter clearance of Antide-from the peripheral circulation was very slow, with an apparent t1/2 (second phase) of 6.5 days following iv administration. Detectable Antide levels were present in the peripheral circulation for more than one month in all five monkeys. In a second experiment, incubation of 125I-Tyro Antide with OVX monkey serum resulted in binding of the labelled peptide to serum proteins and reduction of 125I-Tyro Antide binding to pituitary receptors. Following gel permeation chromatography, greater than 70% of the radioactivity was associated with a 66 kDa protein(s). In conclusion, the prolonged duration of gonadotropin inhibition by Antide seems to derive from the long circulatory half-life of this molecule. In turn, this extended action of Antide may be manifest, at least in part, by binding to serum protein(s) that serves as a built-in peripheral depot release mechanism.  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