全文获取类型
收费全文 | 30751篇 |
免费 | 3685篇 |
国内免费 | 27篇 |
出版年
2022年 | 223篇 |
2021年 | 535篇 |
2020年 | 284篇 |
2019年 | 410篇 |
2018年 | 461篇 |
2017年 | 424篇 |
2016年 | 668篇 |
2015年 | 1123篇 |
2014年 | 1244篇 |
2013年 | 1613篇 |
2012年 | 1874篇 |
2011年 | 1821篇 |
2010年 | 1139篇 |
2009年 | 1021篇 |
2008年 | 1409篇 |
2007年 | 1466篇 |
2006年 | 1281篇 |
2005年 | 1194篇 |
2004年 | 1223篇 |
2003年 | 1092篇 |
2002年 | 1061篇 |
2001年 | 755篇 |
2000年 | 734篇 |
1999年 | 625篇 |
1998年 | 410篇 |
1997年 | 352篇 |
1996年 | 331篇 |
1995年 | 339篇 |
1994年 | 307篇 |
1993年 | 288篇 |
1992年 | 502篇 |
1991年 | 448篇 |
1990年 | 469篇 |
1989年 | 414篇 |
1988年 | 399篇 |
1987年 | 389篇 |
1986年 | 381篇 |
1985年 | 421篇 |
1984年 | 334篇 |
1983年 | 296篇 |
1982年 | 275篇 |
1981年 | 250篇 |
1980年 | 217篇 |
1979年 | 336篇 |
1978年 | 272篇 |
1977年 | 247篇 |
1976年 | 217篇 |
1975年 | 225篇 |
1974年 | 246篇 |
1973年 | 228篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
B F BuSha B G Judd H L Manning P M Simon B C Searle J A Daubenspeck J C Leiter 《Journal of applied physiology》2001,90(6):2330-2340
Evidence of the Hering-Breuer reflex has been found in humans during anesthesia and sleep but not during wakefulness. Cortical influences, present during wakefulness, may mask the effects of this reflex in awake humans. We hypothesized that, if lung volume were increased in awake subjects unaware of the stimulus, vagal feedback would modulate breathing on a breath-to-breath basis. To test this hypothesis, we employed proportional assist ventilation in a pseudorandom sequence to unload the respiratory system above and below the perceptual threshold in 17 normal subjects. Tidal volume, integrated respiratory muscle pressure per breath, and inspiratory time were recorded. Both sub- and suprathreshold stimulation evoked a significant increase in tidal volume and inspiratory flow rate, but a significant decrease in inspiratory time was present only during the application of a subthreshold stimulus. We conclude that vagal feedback modulates respiratory timing on a breath-by-breath basis in awake humans, as long as there is no awareness of the stimulus. 相似文献
34.
35.
Development and Phase 3 testing of the most advanced malaria vaccine, RTS,S/AS01, indicates that malaria vaccine R&D is moving into a new phase. Field trials of several research malaria vaccines have also confirmed that it is possible to impact the host-parasite relationship through vaccine-induced immune responses to multiple antigenic targets using different platforms. Other approaches have been appropriately tested but turned out to be disappointing after clinical evaluation. As the malaria community considers the potential role of a first-generation malaria vaccine in malaria control efforts, it is an apposite time to carefully document terminated and ongoing malaria vaccine research projects so that lessons learned can be applied to increase the chances of success for second-generation malaria vaccines over the next 10 years. The most comprehensive resource of malaria vaccine projects is a spreadsheet compiled by WHO thanks to the input from funding agencies, sponsors and investigators worldwide. This spreadsheet, available from WHO's website, is known as "the rainbow table". By summarizing the published and some unpublished information available for each project on the rainbow table, the most comprehensive review of malaria vaccine projects to be published in the last several years is provided below. 相似文献
36.
Ian R. Brown 《Journal of neurochemistry》1983,40(5):1490-1493
Abstract: Analysis of the cell-free translation products of polysomes isolated from fetal brain and other organs indicates that elevation of maternal body temperature induces the synthesis of a heat shock protein of molecular weight 74,000 (74K). The newborn mammal is particularly sensitive to induction of the 74K protein. As early postnatal development proceeds, higher body temperatures are required to induce synthesis of the 74K heat shock protein. 相似文献
37.
38.
39.
40.
Studies in animals and tissue culture have shown the importance of prolactin and growth hormone in regulating renal 1 alpha-hydroxylase activity and plasma concentrations of 1,25-dihydroxycholecalciferol (1,25(OH)2D3). Evidence for a similar role for these hormones in man was sought by using a radioreceptor assay to measure plasma 1,25(OH)2D3 concentrations in 20 normal subjects, 12 patients receiving dialysis, 11 patients with primary hyperparathyroidism, 10 pregnant women, seven women with prolactinoma, and 14 patients with acromegaly. Circulating 1,25(OH)2D3 concentrations were appreciably raised in the patients with primary hyperparathyroidism and the pregnant women (P less than 0.001), slightly but significantly increased in the patients with prolactinoma (P less than 0.05), and greatly raised in those with acromegaly (P less than 0.001). These results suggest that prolactin and growth hormone are important regulators of renal vitamin D metabolism in the physiological conditions of pregnancy, lactation, and growth in man. 相似文献