全文获取类型
收费全文 | 4806篇 |
免费 | 436篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 47篇 |
儿科学 | 207篇 |
妇产科学 | 109篇 |
基础医学 | 697篇 |
口腔科学 | 156篇 |
临床医学 | 571篇 |
内科学 | 962篇 |
皮肤病学 | 68篇 |
神经病学 | 310篇 |
特种医学 | 134篇 |
外科学 | 777篇 |
综合类 | 105篇 |
一般理论 | 2篇 |
预防医学 | 545篇 |
眼科学 | 48篇 |
药学 | 267篇 |
中国医学 | 3篇 |
肿瘤学 | 263篇 |
出版年
2022年 | 30篇 |
2021年 | 91篇 |
2020年 | 31篇 |
2019年 | 73篇 |
2018年 | 77篇 |
2017年 | 61篇 |
2016年 | 83篇 |
2015年 | 77篇 |
2014年 | 133篇 |
2013年 | 193篇 |
2012年 | 212篇 |
2011年 | 221篇 |
2010年 | 139篇 |
2009年 | 132篇 |
2008年 | 217篇 |
2007年 | 208篇 |
2006年 | 226篇 |
2005年 | 241篇 |
2004年 | 217篇 |
2003年 | 201篇 |
2002年 | 173篇 |
2001年 | 156篇 |
2000年 | 148篇 |
1999年 | 168篇 |
1998年 | 69篇 |
1997年 | 56篇 |
1996年 | 59篇 |
1995年 | 65篇 |
1994年 | 62篇 |
1993年 | 49篇 |
1992年 | 105篇 |
1991年 | 119篇 |
1990年 | 103篇 |
1989年 | 110篇 |
1988年 | 88篇 |
1987年 | 70篇 |
1986年 | 87篇 |
1985年 | 67篇 |
1984年 | 62篇 |
1983年 | 47篇 |
1982年 | 38篇 |
1981年 | 30篇 |
1980年 | 29篇 |
1979年 | 44篇 |
1978年 | 45篇 |
1977年 | 28篇 |
1976年 | 30篇 |
1974年 | 34篇 |
1973年 | 29篇 |
1971年 | 26篇 |
排序方式: 共有5271条查询结果,搜索用时 31 毫秒
1.
2.
3.
W D Lovan R A Weaver R J Lentz J K Goodrum B F Withers 《Aviation, space, and environmental medicine》1986,57(4):370-375
The Naval Special Board of Flight Surgeons was established in 1956 for the evaluation of Navy, Marine Corps, and Coast Guard problem aeromedical cases. This paper examines a sample 248 of these cases for the period of 1974-83 with respect to the characteristics of those referred, their referral diagnostic category, and the recommendation of the Special Board regarding return to a flying status. Those cases with a referral diagnostic category of ENT and Ophthalmology were less likely to be returned to flight status. Older, more senior pilots, and pilots with more total flight time were less likely to be returned to unrestricted flying than were their younger, more junior, and less experienced counterparts. Otherwise, no significant difference in outcome based on age, rank, marital status, branch of service, specialty, or flight hours was detected. Overall, 61% of those evaluated by the SBFS were returned to flight status. 相似文献
4.
Human calcium absorption from whole-wheat products 总被引:1,自引:0,他引:1
Fractional calcium absorption from wheat products and the influence of co-ingested wheat products on calcium absorption from milk were measured in a series of randomized crossover studies in healthy adult women. The wheat had been intrinsically labeled with 45Ca during growth. In the first study, fractional calcium absorption from leavened whole-wheat bread averaged 0.817 +/- 0.124. By comparison, absorption from milk, ingested at a comparable load in the same women, averaged only 0.589 +/- 0.111. When labeled bread was co-ingested with milk, at the same aggregate load as for bread alone, bread calcium absorption fell to 0.748 +/- 0.103 (P less than 0.05). In a second study, calcium absorption from an extruded cereal prepared from intrinsically labeled wheat bran was compared with milk. Calcium absorption from the cereal (0.223 +/- 0.046) was significantly less than from milk (0.375 +/- 0.072) (P less than 0.001). When the two were co-fed at the same total load, milk calcium absorption fell to 0.258 +/- 0.055 (P less than 0.001). In a third study, the effect of phytate hydrolysis through yeast fermentation and of Maillard browning on calcium absorption was investigated using leavened bread and underbaked and overbaked cookies, each made with intrinsically labeled wheat flour. Calcium absorption from cookies was not affected by the extent of browning and averaged 0.652 +/- 0.087. However, calcium absorption from bread in these same women averaged 0.703 +/- 0.108. This was significantly more than from the cookies (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
5.
Soybean phytate content: effect on calcium absorption 总被引:4,自引:0,他引:4
R P Heaney C M Weaver M L Fitzsimmons 《The American journal of clinical nutrition》1991,53(3):745-747
Absorption of calcium from soybeans with low and high phytate contents, intrinsically labeled with 45Ca, was measured in 16 normal women and compared in 15 of these same subjects with absorption of calcium from labeled milk. The average test load of calcium for all three sources was 2.45 mmol. Fractional calcium absorption (+/- SD) from the high-phytate soybeans averaged 0.310 +/- 0.070; from the low phytate soybeans, 0.414 +/- 0.074; and from milk, 0.377 +/- 0.056. The mean difference (+/- SEM) in fractional calcium absorption for the two phytate levels was 0.104 +/- 0.014 (P less than 0.001). 相似文献
6.
7.
8.
9.
Comparison of dynamic and step-and-shoot intensity-modulated radiation therapy planning and delivery. 总被引:1,自引:0,他引:1
Intensity-modulated radiation therapy (IMRT) is commonly delivered using the dynamic or segmental mode of multileaf collimators (DMLC or SMLC). Both methods are designed to deliver intensity-modulated beams as determined by inverse planning software. In this study, we have used the Helios IMRT planning system to generate ideal treatment plans for 10 cases of 2 common treatment sites (prostate and head and neck) and have investigated the actual treatment fluence distributions generated for each of the MLC leaf motion choices. The 2 dose delivery techniques were dosimetrically compared to each other and to the treatment plans. For each technique, point doses were measured in a water phantom using ionization chambers. Also for each technique, 2-dimensional dose distributions at a selected depth in a plastic phantom were obtained, using extended range film. The total delivery time and the number of monitor units (MU) delivered by each method were also compared. Our results indicate that the 2 delivery methods produce comparable results dosimetrically. For the cases reviewed, the delivery time was an average of 15% longer for SMLC deliveries, while the number of MUs (beam-on time) required by SMLC was an average of 15% fewer, than that for the DMLC. In the interest of simplicity, lower beam-on time, and potentially fewer mechanically-related problems, we think that the SMLC delivery technique may be the better choice when Helios is used for planning and Varian linear accelerators are used for delivery. 相似文献
10.
Alternatives in the surgical management of in situ breast cancer. A meta-analysis of outcome 总被引:2,自引:0,他引:2
The surgical management of lobular carcinoma in situ (LCIS) and ductal carcinoma in situ (DCIS) remains controversial. For in situ breast cancer local excision (LE), local excision and radiation therapy (LERT) and mastectomy (MAST) have all been advocated. A search of the English literature found 13 reports concerning the surgical management of LCIS and 12 reports concerning the management of DCIS. The data were combined in a meta-analysis of outcome. As expected, recurrence rates following LE with both LCIS 8.4%) and DCIS (17%) are high. However,the overall mortality following mastectomy for recurrence, LCIS (2.8%) and DCIS (2.3%) does not differ statistically from those treated initially with mastectomy for LCIS (0.9%) and DCIS (1.7%). We conclude from these data that local recurrence after breast conserving procedures for in situ breast cancer does not carry an ominous prognosis. This knowledge should aid in planning individual therapy. 相似文献