全文获取类型
收费全文 | 13561篇 |
免费 | 955篇 |
国内免费 | 57篇 |
专业分类
耳鼻咽喉 | 157篇 |
儿科学 | 403篇 |
妇产科学 | 178篇 |
基础医学 | 1644篇 |
口腔科学 | 295篇 |
临床医学 | 1559篇 |
内科学 | 3032篇 |
皮肤病学 | 233篇 |
神经病学 | 1266篇 |
特种医学 | 682篇 |
外科学 | 2093篇 |
综合类 | 136篇 |
一般理论 | 5篇 |
预防医学 | 951篇 |
眼科学 | 391篇 |
药学 | 773篇 |
中国医学 | 15篇 |
肿瘤学 | 760篇 |
出版年
2023年 | 87篇 |
2022年 | 173篇 |
2021年 | 365篇 |
2020年 | 204篇 |
2019年 | 325篇 |
2018年 | 397篇 |
2017年 | 260篇 |
2016年 | 330篇 |
2015年 | 411篇 |
2014年 | 495篇 |
2013年 | 601篇 |
2012年 | 1004篇 |
2011年 | 975篇 |
2010年 | 581篇 |
2009年 | 489篇 |
2008年 | 865篇 |
2007年 | 842篇 |
2006年 | 810篇 |
2005年 | 742篇 |
2004年 | 594篇 |
2003年 | 581篇 |
2002年 | 474篇 |
2001年 | 194篇 |
2000年 | 161篇 |
1999年 | 205篇 |
1998年 | 133篇 |
1997年 | 138篇 |
1996年 | 105篇 |
1995年 | 84篇 |
1994年 | 91篇 |
1993年 | 63篇 |
1992年 | 104篇 |
1991年 | 114篇 |
1990年 | 98篇 |
1989年 | 113篇 |
1988年 | 96篇 |
1987年 | 91篇 |
1986年 | 82篇 |
1985年 | 105篇 |
1984年 | 88篇 |
1983年 | 59篇 |
1982年 | 62篇 |
1981年 | 50篇 |
1980年 | 66篇 |
1979年 | 75篇 |
1978年 | 52篇 |
1976年 | 45篇 |
1975年 | 39篇 |
1972年 | 38篇 |
1971年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 26 毫秒
31.
A 1975 report stated that a schizophrenic genotype may be manifested in infants by a neurointegrative defect called pandysmaturation. Recent evidence supports this: (1) 12 studies found delayed development in schizophrenics' infants and in preschizophrenics; (2) "blind" psychometric evaluations favored an adult schizotypal disorder in four to six of seven high-risk subjects with pandysmaturation in the New York study; and (3) finally, in a partial replication of this method using the Jerusalem data, blind diagnoses of "probable" and "possible" pandysmaturation were significantly related to a parental diagnosis of schizophrenia and to cognitive and motor neurointegrative deficits at 10 years. Obstetrical complications were unrelated to diagnosis, pandysmaturation, or outcome in the overall sample. However, we found a small subgroup of schizophrenic offspring in whom the most severe motor deficits at follow-up were related to obstetrical complications, pandysmaturation, and low birth weight. 相似文献
32.
Matthias Löhle Thomas Müller Carola Wicher Marcus Roedel Harald Schubert Otto W. Witte Peter W. Nathanielsz Matthias Schwab 《The Journal of physiology》2005,564(2):575-588
Synthetic glucocorticoids are administered to pregnant women in premature labour to accelerate fetal lung maturation at a time when fetal cerebrovascular and endocrine systems are maturing. Exposure to glucocorticoids at 0.8–0.9 of gestation increases peripheral and cerebrovascular resistance (CVR) in fetal sheep. We examined whether the increase of CVR and its adverse effect on cerebral blood flow (CBF) depend on the current level of maturation of the pituitary–adrenal axis and the cerebrovascular system. Using fluorescent microspheres, regional CBF was measured in 11 brain regions before and 24 h and 48 h after the start of 3.3 μg kg−1 h−1 betamethasone ( n = 8) or vehicle ( n = 7) infusions to fetal sheep at 0.73 of gestation. Hypercapnic challenges were performed before and 24 h after the onset of betamethasone exposure to examine betamethasone effects on cerebrovascular reactivity. Betamethasone exposure decreased CBF by approximately 40% in all brain regions after 24 h of infusion ( P < 0.05). The decline in CBF was mediated by a CVR increase of 111 ± 16% in the cerebral cortex and 129 ± 29% in subcortical regions ( P < 0.05). Hypercapnic cerebral vasodilatation and associated increase in CBF were blunted ( P < 0.05). Fetal CBF recovered after 48 h of betamethasone administration. There were no differences in glucocorticoid induced CBF and CVR changes compared with our previous findings at 0.87 of gestation. We conclude that the cerebrovascular effects of antenatal glucocorticoids are independent of cerebrovascular maturation and preparturient increase in activity of the fetal pituitary–adrenal axis. 相似文献
33.
The Role of APO-1-Mediated Apoptosis in the Immune System 总被引:12,自引:0,他引:12
34.
Ion-exchange chromatography and gel filtration have been reported to yield partial separation of mycobacterial antigens. These procedures were used in combination with isoelectric focusing in an attempt to purify antigens of Mycobacterium tuberculosis strain H37Ra. The fractionating action of isoelectric focusing is dependent upon differences in the isoelectric points of the proteins to be separated. Culture filtrate of M. tuberculosis H37Ra was chromatographed on Sephadex G-200. This resulted in two widely separated peaks. The first peak, presumably containing high-molecular-weight substances, was then fractionated on a diethylaminoethyl Sephadex anion-exchange column. Three peaks were collected, and each was subjected to isoelectric focusing. Each peak was further separated into two or more fractions. The serological reactivity of each fraction was determined by immunodiffusion and immunoelectrophoresis. Sensitized guinea pigs were also skin-tested with the fractions. Two of the fractions contained only a single precipitinogen. One fraction contained two precipitinogens. A fourth fraction contained three precipitinogens and was also the only fraction to display sensitin activity. Four of the fractions were inactive either as precipitinogens or sensitins. The results suggest that the methods described are useful for the separation of mycobacterial antigens. 相似文献
35.
Perkins KA Levine M Marcus M Shiffman S D'Amico D Miller A Keins A Ashcom J Broge M 《Journal of consulting and clinical psychology》2000,68(1):176-180
Because negative mood is a characteristic of both tobacco withdrawal and menstrual discomfort, withdrawal may vary by menstrual cycle phase. Tobacco withdrawal, mood, and menstrual discomfort were assessed in premenopausal women who quit smoking during either the follicular (Days 1-14 postmenstrual onset; n = 41) or luteal (Day 15 or longer postmenstrual onset; n = 37) phase of the menstrual cycle and maintained biochemically verified smoking abstinence during the postquit week. Women quitting during the luteal phase reported significantly greater increases in tobacco withdrawal and self-reported depressive symptoms than women quitting during the follicular phase. These results indicate that selecting a quit-smoking day early in the follicular phase may attenuate withdrawal and negative affect in premenopausal female smokers. 相似文献
36.
The heart in hypertension. 总被引:10,自引:0,他引:10
37.
Synergistic interaction of topographic features in the production of bone-like nodules on Ti surfaces by rat osteoblasts 总被引:4,自引:0,他引:4
The objective of this study was to study the responses of osteoblast-like cells to rough Titanium (Ti)-coated epoxy surfaces of differing topographic complexity. Four topographies were studied: polished (PO), coarse-blasted (CB), acid-etched (AE) and coarse-blasted+acid-etched (SLA). Rat osteoblasts were cultured on these surfaces and their morphology, thickness as well as the number and size of bone-like nodules measured. To determine cell shape and cell thickness, fluorescein-5-thiosemicarbazide was used to stain the cell components including the cell membrane, the stained cells were optically sectioned using epifluorescent microscopy and the optical sections were computationally reconstructed to obtain three-dimensional images in which cell volume and cell thickness could be determined. Similarly optical sections of bone-like nodules labeled with tetracycline were also reconstructed to determine their size. The different surface topographies were found to alter the thickness and morphology of osteoblasts cultured on these surfaces. Osteoblasts produced significantly more and larger nodules on SLA compared to other surfaces. Nevertheless and perhaps surprisingly, given the evidence in various cell populations that cell shape can affect cell differentiation, cell thickness was not directly correlated with an increase in bone-like nodule formation. Data were analyzed by factorial analysis of variance. In this way the primary effect of each surface treatment ( i.e. blasting and acid etching) could be assessed as well as their interaction. Both the acid etching and blasting processes significantly affected the number and size of bone-like nodules cultured on Ti surfaces. Moreover there were significant interaction effects indicating that surface topographic features can act synergistically to enhance bone formation. This result suggests that a useful approach to the optimization of surfaces for bone production could involve systematic investigation of combinations of processes each of which produces distinct surface topographical features. 相似文献
38.
39.
Summary Study design: As part of a large screening study of perinatal depression, pregnant women were screened for demographic, depression and treatment variables in obstetrics clinics. Women taking antidepressant medication prior to conception were included in the sample as the study aimed to document rates of antidepressant medication use, and relationship to depressive symptomatology.Results: Among women who reported using antidepressant medications within 2 years prior to screening (n = 390, or 11% of all women), 22% reported current use of these medications. Women who reported using antidepressant medications (52%) and those who discontinued them (49%) evidenced elevated depressive symptoms during pregnancy.Conclusions: Both women who discontinue and some who continue antidepressants during pregnancy demonstrate depressive symptoms, suggesting sub-optimal management of both groups. Future studies should carefully assess the adequacy of treatments prescribed as well as the monitoring and adherence of recommended treatments. Full symptom remission should be the goal for antenatal and postnatal depression in order to minimize risk to mother and baby. 相似文献
40.
Ectopic bone formation associated with mesenchymal stem cells in a resorbable calcium deficient hydroxyapatite carrier 总被引:6,自引:0,他引:6
Kasten P Vogel J Luginbühl R Niemeyer P Tonak M Lorenz H Helbig L Weiss S Fellenberg J Leo A Simank HG Richter W 《Biomaterials》2005,26(29):5879-5889
Bone substitute materials can induce bone formation in combination with mesenchymal stem cells (MSC). The aim of the current study was to examine ectopic in vivo bone formation with and without MSC on a new resorbable ceramic, called calcium deficient hydroxyapatite (CDHA). Ceramic blocks characterized by a large surface (48 m2/g) were compared with beta-tricalcium phosphate (beta-TCP), hydroxyapatite (HA) ceramics (both ca. 0.5 m2/g surface) and demineralized bone matrix (DBM). Before implantation in the back of SCID mice carriers were freshly loaded with 2x10(5) expanded human MSC or loaded with cells and kept under osteogenic conditions for two weeks in vitro. Culture conditions were kept free of xenogenic supplements. Deposits of osteoid at the margins of ceramic pores occurred independent of osteogenic pre-induction, contained human cells, and appeared in 416 MSC/CDHA composites compared to 216 MSC/beta-TCP composites. ALP activity was significantly higher in samples with MSC versus empty controls (p<0.001). Furthermore, ALP was significantly (p<0.05) higher for all ceramics when compared to the DBM matrix. Compared to previous studies, overall bone formation appeared to be reduced possibly due to the strict human protocol. Ectopic bone formation in the novel biomaterial CDHA varied considerably with the cell pool and was at least equal to beta-TCP blocks. 相似文献