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   36109篇
  免费   2477篇
  国内免费   138篇
耳鼻咽喉   427篇
儿科学   937篇
妇产科学   603篇
基础医学   4445篇
口腔科学   673篇
临床医学   3415篇
内科学   8686篇
皮肤病学   564篇
神经病学   3229篇
特种医学   1183篇
外国民族医学   1篇
外科学   5080篇
综合类   456篇
一般理论   17篇
预防医学   2921篇
眼科学   784篇
药学   2630篇
  1篇
中国医学   62篇
肿瘤学   2610篇
  2023年   175篇
  2022年   257篇
  2021年   645篇
  2020年   409篇
  2019年   624篇
  2018年   742篇
  2017年   554篇
  2016年   603篇
  2015年   653篇
  2014年   1038篇
  2013年   1523篇
  2012年   2311篇
  2011年   2379篇
  2010年   1331篇
  2009年   1206篇
  2008年   2282篇
  2007年   2516篇
  2006年   2573篇
  2005年   2494篇
  2004年   2431篇
  2003年   2346篇
  2002年   2282篇
  2001年   264篇
  2000年   191篇
  1999年   327篇
  1998年   493篇
  1997年   386篇
  1996年   369篇
  1995年   351篇
  1994年   317篇
  1993年   280篇
  1992年   217篇
  1991年   166篇
  1990年   161篇
  1989年   151篇
  1988年   153篇
  1987年   170篇
  1986年   141篇
  1985年   170篇
  1984年   272篇
  1983年   243篇
  1982年   336篇
  1981年   284篇
  1980年   257篇
  1979年   118篇
  1978年   162篇
  1977年   155篇
  1976年   146篇
  1975年   109篇
  1974年   96篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.

Background

The under-5 mortality rate (U5MR) is an important metric of child health and survival. Country-level estimates of U5MR are readily available, but efforts to estimate U5MR subnationally have been limited, in part, due to spatial misalignment of available data sources (e.g., use of different administrative levels, or as a result of historical boundary changes).

Methods

We analyzed all available complete and summary birth history data in surveys and censuses in six countries (Bangladesh, Cameroon, Chad, Mozambique, Uganda, and Zambia) at the finest geographic level available in each data source. We then developed small area estimation models capable of incorporating spatially misaligned data. These small area estimation models were applied to the birth history data in order to estimate trends in U5MR from 1980 to 2015 at the second administrative level in Cameroon, Chad, Mozambique, Uganda, and Zambia and at the third administrative level in Bangladesh.

Results

We found substantial variation in U5MR in all six countries: there was more than a two-fold difference in U5MR between the area with the highest rate and the area with the lowest rate in every country. All areas in all countries experienced declines in U5MR between 1980 and 2015, but the degree varied both within and between countries. In Cameroon, Chad, Mozambique, and Zambia we found areas with U5MRs in 2015 that were higher than in other parts of the same country in 1980. Comparing subnational U5MR to country-level targets for the Millennium Development Goals (MDG), we find that 12.8% of areas in Bangladesh did not meet the country-level target, although the country as whole did. A minority of areas in Chad, Mozambique, Uganda, and Zambia met the country-level MDG targets while these countries as a whole did not.

Conclusions

Subnational estimates of U5MR reveal significant within-country variation. These estimates could be used for identifying high-need areas and positive deviants, tracking trends in geographic inequalities, and evaluating progress towards international development targets such as the Sustainable Development Goals.
  相似文献   
13.
14.
ProFile 25/.04 instruments manufactured from three variants of Nitinol (1A, 1B & 2AS) were compared with stock production ProFile 25/.04 instruments and fatigue tested to failure. Cyclic fatigue testing was performed by rotating instruments at 300 RPM in a simulated steel root canal with 5 mm radius and 90 degrees curve until instrument separation. Time to failure was recorded. Torsion testing was undertaken by clamping 3 mm of each instrument tip between brass plates and rotating it at 2 RPM until failure. Data were recorded for torque and angle at fracture. Statistical differences were found with nickel-titanium variant 1B (M-Wire NiTi) nearly 400% more resistant to cyclic fatigue than stock ProFile 25/.04 (P < .001). Torsion testing found differences between all 508 Nitinol groups and M-Wire NiTi (P < .001). ProFile 25/.04 files manufactured from M-Wire NiTi have significantly greater resistance to cyclic fatigue while maintaining comparable torsional properties.  相似文献   
15.
16.
Orofacial granulomatosis (OFG) is a granulomatous disease of the orofacial region. This clinicopathological entity describes patients with oral lesions characterized by persistent and/or recurrent labial enlargement, ulcers, and a variety of other orofacial features, which on biopsy have lymphedema and noncaseating granulomas. The cause is idiopathic but appears to represent an abnormal immune reaction. This may be a manifestation of Crohn's disease (CD) since some patients with oral lesions develop typical bowel symptoms of CD in ensuing months to years; tooth-associated infections, sarcoidosis, food or contact allergies, and viruses have also been implicated in causing OFG. Clinical features of OFG are highly variable and sometimes so insidious that signs and symptoms are frequently not severe enough to cause alarm. The lips are most commonly involved and demonstrate a nontender, persistent swelling. Because of the relatively nonspecific clinical findings associated with granulomatous diseases, a microscopic diagnosis of granulomatous inflammation often presents a diagnostic dilemma for clinicians. We report a case of OFG of the lower lip and cheek and describe its management to add to the current body of literature on the subject.  相似文献   
17.
18.
Eleven diets were evaluated for their ability to produce dental calculus in albino rats. A diet containing 50 % cornstarch, 32 % nonfat dry milk, 3 % liver powder, 5 % celluflour, 1 % cottonseed oil, 5 % powdered sucrose, 1 % calcium chloride dihydrate, 2.7 % sodium dihydrogen phosphate monohydrate, and 0.3 % magnesium sulfate (Francis and Briner 1969) was remarkably effective. On the basis of a 0–3 calculus scoring system, an average score of 2.36 (S.D. = 0.65) resulted after 4 weeks' exposure to the above diet and, after 8 weeks, the average score was 2.59 (S.D. = 0.56).
While it was found that, in general, high cornstarch and milk powder diets were associated with higher calculus scores, no other diet remotely approached the above diet in calculogenicity.  相似文献   
19.
Pulpitis pain might be triggered by a cold stimulus, yet the cellular mechanisms responsible for this phenomenon are largely unknown. One possible mechanism involves the direct activation of cold-responsive thermoreceptors. The purpose of this study was to evaluate the possible role of the TRPM8 thermoreceptor in cold-mediated noxious pulpal pain mechanisms by comparing expression patterns in pulpal nerves from healthy control molars to cold-sensitive painful molars with irreversible pulpitis. Samples were identically processed with the indirect immunofluorescence method, and images were obtained with confocal microscopy. The immunofluorescence intensity and area occupied by TRPM8 within N52/PGP9.5-identified nerve fibers were quantified. Results showed that relative to normal samples, TRPM8 nerve area expression was significantly less in the cold-sensitive painful samples (34.9% vs 8%, P <0.03), but with no significant difference in immunofluorescence intensity between the 2 groups. These results suggest that TRPM8 is most likely not involved in cold-mediated noxious pulpal pain mechanisms.  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