全文获取类型
收费全文 | 5446篇 |
免费 | 342篇 |
国内免费 | 31篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 298篇 |
妇产科学 | 203篇 |
基础医学 | 597篇 |
口腔科学 | 118篇 |
临床医学 | 461篇 |
内科学 | 1272篇 |
皮肤病学 | 58篇 |
神经病学 | 640篇 |
特种医学 | 535篇 |
外科学 | 391篇 |
综合类 | 38篇 |
一般理论 | 4篇 |
预防医学 | 501篇 |
眼科学 | 49篇 |
药学 | 325篇 |
1篇 | |
中国医学 | 1篇 |
肿瘤学 | 318篇 |
出版年
2022年 | 24篇 |
2021年 | 55篇 |
2020年 | 35篇 |
2019年 | 68篇 |
2018年 | 112篇 |
2017年 | 96篇 |
2016年 | 101篇 |
2015年 | 115篇 |
2014年 | 119篇 |
2013年 | 221篇 |
2012年 | 234篇 |
2011年 | 238篇 |
2010年 | 148篇 |
2009年 | 196篇 |
2008年 | 227篇 |
2007年 | 231篇 |
2006年 | 235篇 |
2005年 | 240篇 |
2004年 | 209篇 |
2003年 | 218篇 |
2002年 | 159篇 |
2001年 | 164篇 |
2000年 | 161篇 |
1999年 | 134篇 |
1998年 | 144篇 |
1997年 | 155篇 |
1996年 | 153篇 |
1995年 | 115篇 |
1994年 | 110篇 |
1993年 | 139篇 |
1992年 | 104篇 |
1991年 | 92篇 |
1990年 | 93篇 |
1989年 | 122篇 |
1988年 | 115篇 |
1987年 | 86篇 |
1986年 | 85篇 |
1985年 | 91篇 |
1984年 | 62篇 |
1983年 | 42篇 |
1982年 | 39篇 |
1981年 | 52篇 |
1980年 | 34篇 |
1979年 | 34篇 |
1978年 | 20篇 |
1977年 | 32篇 |
1976年 | 31篇 |
1975年 | 31篇 |
1974年 | 15篇 |
1970年 | 10篇 |
排序方式: 共有5819条查询结果,搜索用时 578 毫秒
61.
62.
F. VanderWerf Majid Aramideh Jan A. Otto Bram W. Ongerboer de Visser 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,121(4):433-441
Functionally and anatomically, the orbicularis oculi (OO) muscle can be subdivided in a pretarsal, a preseptal, and an orbital
portion. In the rhesus monkey, fluorescent and neuronal retrograde tracing experiments were performed in the pretarsal or
the orbital portion of the OO muscle, or both, using fast blue, diamidino yellow, and wheat germ agglutinin-horseradish peroxidase
as tracers. The preseptal portion was not investigated because of close anatomical relationships to the other portions. It
was found that motoneurons innervating the OO muscle are located exclusively within the intermediate subnucleus of the motor
facial nucleus. The upper pretarsal motoneurons show a specific distribution in the dorso-rostral border area of the intermediate
subnucleus, representing a dome-like organization, while lower pretarsal motoneurons are situated more ventrally in the adjacent
area. The pretarsal motoneurons are all located dorsally in the rostral half and the upper part of the caudal half of the
intermediate subnucleus. The upper pretarsal portion is subserved by about one third of the total intermediate motoneuron
population. The size of the upper pretarsal motoneurons is similar to that of the motoneurons of the lower pretarsal portion
of the OO muscle and falls, for the vast majority, into the large motoneuronal range. Motoneurons belonging to the upper and
lower orbital portions are located ventrally and are more randomly distributed in the rostral half of the intermediate subnucleus.
The size of orbital motoneurons varies from small to large. The large fraction of pretarsal motoneurons may reflect the specific
function of the upper pretarsal portion during rapid and highly coordinated movements of the eyelids in different types of
blinking.
Received: 18 September 1997 / Accepted: 13 March 1998 相似文献
63.
Rutger L. van Bezooijen Marco C. DeRuiter Nathalie Vilain Rui M. Monteiro Annemieke Visser Lianne van der Wee‐Pals Conny J. van Munsteren Pancras C.W. Hogendoorn Michel Aguet Christine L. Mummery Socrates E. Papapoulos Peter Ten Dijke Clemens W.G.M. Löwik 《Developmental dynamics》2007,236(2):606-612
Spatial-temporal regulation of bone morphogenetic protein (BMP) and Wnt activity is essential for normal cardiovascular development, and altered activity of these growth factors causes maldevelopment of the cardiac outflow tract and great arteries. In the present study, we show that SOST, a Dan family member reported to antagonize BMP and Wnt activity, is expressed within the medial vessel wall of the great arteries containing smooth muscle cells. The ascending aorta, aortic arch, brachiocephalic artery, common carotids, and pulmonary trunk were all associated with SOST expressing smooth muscle cells, while the heart itself, including the valves, and more distal arteries, that is, pulmonary arteries, subclavian arteries, and descending aorta, were negative. SOST was expressed from embryonic day 15.5 up to the neonatal period. SOST expression, however, did not correspond with inhibition of Smad-dependent BMP activity or beta-catenin-dependent Wnt activity in the great arteries. Activity of both signaling pathways was already down-regulated before induction of SOST expression. 相似文献
64.
Permeation of human ovarian tissue with cryoprotective agents in preparation for cryopreservation 总被引:18,自引:10,他引:18
Newton H; Fisher J; Arnold JR; Pegg DE; Faddy MJ; Gosden RG 《Human reproduction (Oxford, England)》1998,13(2):376-380
The recent improvements in the treatment of cancer by chemo- and
radiotherapy have led to a significant increase in the survival rates of
patients with malignant disease, but at the expense of distressing side
effects. One major problem, especially for younger patients, is that
aggressive therapy destroys a significant proportion of the follicular
population, which can result in either temporary or permanent infertility.
Freeze-banking pieces of ovarian cortex prior to treatment is one strategy
for preserving fecundity. When the patient is in remission, fertility
could, theoretically, be restored by autografting the thawed tissue at the
orthotopic site or by growing isolated follicles to maturity in vitro.
Recent studies have found good follicular survival in frozen-thawed human
ovarian tissue but to optimize the process an effective cryopreservation
method needs to be developed. An essential part of such a technique is to
permeate the tissue with a cryoprotectant to minimize ice formation and the
extent of this equilibration is an important determinant of post-thaw
cellular survival. In the current study, we have investigated the diffusion
of four cryoprotective agents into human tissue at both 4 degrees C and 37
degrees C. We have also studied the effect of adding different
concentrations of the non penetrating cryoprotective agent, sucrose, to the
freezing media using the release of lactate dehydrogenase as a measure of
its protective effect. At 4 degrees C propylene glycol and glycerol
penetrated the tissue significantly slower than either ethylene glycol or
dimethyl sulphoxide. At the higher temperature of 37 degrees C all four
cryoprotectants penetrated at a faster rate, however concern about enhanced
toxicity prevents the use of these conditions in practice. Thus, the
results suggest that the best method of preparing tissue for freezing is
exposure for 30 min to 1.5 M solutions of ethylene glycol or dimethyl
sulphoxide at 4 degrees C; this achieved a mean tissue concentration that
was almost 80% that of the bathing solution. We also report that the
addition of low concentrations of sucrose to the freezing medium does not
have a significant protective effect against freezing injury.
相似文献
65.
A. H. J. Maas J. A. Kreuger A. J. Hoelen B. F. Visser 《Pflügers Archiv : European journal of physiology》1972,334(3):264-275
Summary A computer program is presented and evaluated, which calculates all acid-base parameters from data provided by either the
indirect Astrup method or the direct method using empirical formulae derived from the Siggaard-Andersen curve nomogram. The
program is implemented on a PDP 8 in a multi-user FOCAL environment and can be adapted to other electronic calculators. 相似文献
66.
Stein TP; Oram-Smith JC; Leskiw MJ; Wallace HW; Long LC; Leonard JM 《The American journal of physiology》1976,230(5):1321-1325
67.
Fever and antipyresis in the lizard Dipsosaurus dorsalis 总被引:2,自引:0,他引:2
68.
Zuidhoek S Visser A Bredero ME Postma A 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2004,157(2):265-268
It has been argued that representations of peripersonal space based on haptic input are systematically distorted by egocentric reference frames. Interestingly, a recent study has shown that noninformative vision (i.e., freely viewing the region above the haptic workspace) improves performance on the so-called haptic parallel-setting task, in which participants are instructed to rotate a test bar until it is parallel to a reference bar. In the present study, we made a start at identifying the different sensory integration mechanisms involved in haptic space perception by distinguishing the possible effects of orienting mechanisms from those of noninformative vision. We found that both the orienting direction of head and eyes and the availability of noninformative vision affect parallel-setting performance and that they do so independently: orienting towards a reference bar facilitated the parallel-setting of a test bar in both no-vision and noninformative vision conditions, and noninformative vision improved performance irrespective of orienting direction. These results suggest the effects of orienting and noninformative vision on haptic space perception to depend on distinct neurocognitive mechanisms, likely to be expressed in different modulations of neural activation in the multimodal parietofrontal network, thought to be concerned with multimodal representations of peripersonal space. 相似文献
69.
We disrupted the Aspergillus niger gene argB, encoding ornithine transcarbamylase. Full characterisation of the argB deletion was performed by Southern blot analysis, growth tests and by means of mitotic recombination, complementation and transformation. The argB locus was found to be physically removed, thus creating an auxotrophic mutation. The latter can be supplemented by addition of arginine into the culture medium. The argB gene and its disruption do not correlate to the argI13 (formerly argB13) allele described. The delta argB is on chromosome I whereas argI13 is on V. In addition, the argI13 mutation can only be complemented by the A. nidulans argB gene, whereas the new argB deletion can be complemented by both the A. niger and A. nidulans argB genes. The delta argB strain has been used to generate several strains in a breeding programme and to study the expression of important genes, such as areA and kexB. 相似文献
70.
Highly repetitive DNA sequences were isolated from genomic DNA libraries of Alstroemeria psittacina and A. inodora. Among the repetitive sequences that were isolated, tandem repeats as well as dispersed repeats could be discerned. The tandem
repeats belonged to a family of interlinked Sau3A subfragments with sizes varying from 68–127 bp, and constituted a larger HinfI repeat of approximately 400 bp. Southern hybridization showed a similar molecular organization of the tandem repeats in
each of the Brazilian Alstroemeria species tested. None of the repeats hybridized with DNA from Chilean Alstroemeria species, which indicates that they are specific for the Brazilian species. In-situ localization studies revealed the tandem repeats to be localized in clusters on the chromosomes of A. inodora and A. psittacina: distal hybridization sites were found on chromosome arms 2PS, 6PL, 7PS, 7PL and 8PL, interstitial sites on chromosome arms
2PL, 3PL, 4PL and 5PL. The applicability of the tandem repeats for cytogenetic analysis of interspecific hybrids and their
role in heterochromatin organization are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献