全文获取类型
收费全文 | 9386篇 |
免费 | 588篇 |
国内免费 | 57篇 |
专业分类
耳鼻咽喉 | 116篇 |
儿科学 | 241篇 |
妇产科学 | 151篇 |
基础医学 | 1319篇 |
口腔科学 | 1076篇 |
临床医学 | 665篇 |
内科学 | 1889篇 |
皮肤病学 | 334篇 |
神经病学 | 745篇 |
特种医学 | 268篇 |
外科学 | 950篇 |
综合类 | 164篇 |
一般理论 | 3篇 |
预防医学 | 976篇 |
眼科学 | 139篇 |
药学 | 581篇 |
中国医学 | 117篇 |
肿瘤学 | 297篇 |
出版年
2023年 | 82篇 |
2022年 | 202篇 |
2021年 | 350篇 |
2020年 | 249篇 |
2019年 | 302篇 |
2018年 | 329篇 |
2017年 | 243篇 |
2016年 | 226篇 |
2015年 | 355篇 |
2014年 | 434篇 |
2013年 | 515篇 |
2012年 | 765篇 |
2011年 | 744篇 |
2010年 | 461篇 |
2009年 | 373篇 |
2008年 | 503篇 |
2007年 | 480篇 |
2006年 | 494篇 |
2005年 | 405篇 |
2004年 | 315篇 |
2003年 | 284篇 |
2002年 | 246篇 |
2001年 | 175篇 |
2000年 | 143篇 |
1999年 | 140篇 |
1998年 | 98篇 |
1997年 | 100篇 |
1996年 | 83篇 |
1995年 | 64篇 |
1994年 | 61篇 |
1993年 | 58篇 |
1992年 | 63篇 |
1991年 | 55篇 |
1990年 | 51篇 |
1989年 | 59篇 |
1988年 | 50篇 |
1987年 | 48篇 |
1986年 | 34篇 |
1985年 | 37篇 |
1984年 | 40篇 |
1983年 | 19篇 |
1982年 | 24篇 |
1981年 | 19篇 |
1980年 | 29篇 |
1979年 | 15篇 |
1977年 | 15篇 |
1976年 | 16篇 |
1975年 | 22篇 |
1973年 | 18篇 |
1966年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Fagundes-Pereyra WJ Ramos Lde A Malheiro OB Freire Rde A Diniz E'Silva R de Almeida RM de Almeida RM 《Arquivos de neuro-psiquiatria》1999,57(4):994-999
PURPOSE: We aimed with study to assess the current clinical practice about the management of high blood pressure in patients in the acute phase of ischemic stroke. We also comment some topics of ischemic stroke treatment. METHODS: A case report of a patient admitted 8 hours after onset of ischemic stroke and with blood pressure of 186 x 110 mmHg was presented to 120 surgeons and clinician. They were asked to decide the best therapeutic option: to increase, decrease or maintenance blood pressure. RESULTS: Thirty-eight physicians (31.7%) considered decreasing blood pressure the best therapeutics, 82 (68.3%) considered maintenance and none decided to increase it (p < 0.05). There was no difference between the two specialties conduct. The physicians, with more than 10 years of graduation, had a tendency to decrease the blood pressure (p < 0.05). CONCLUSION: The maintenance of blood pressure may present a sufficient blood support to compensate brain flow. A high percentage of the physicians (31.7%) do not know about the current concepts of therapeutics considering hypertension in acute ischemic stroke. The development on special units to treat these patients ("stroke units") may eventually decrease the morbimortality rates of ischemic stroke. 相似文献
102.
103.
The purpose of the authors in this article was to evaluate the effects of supplementing maternal milk with two different caloric formulas on the growth of premature newborns until they reached 40 weeks of post-conceptional age. Seventy premature infants weighing < 1750g at birth were randomized: 35 adequate for gestational age (AGA) and 35 small for gestational age received maternal milk and either a special preterm formula or a modified formula. Anthropometric measurements and clinical evaluations were used to determine the nutritional status and the postnatal growth of these infants, who were analyzed in six different moments: at maximum weight loss, at return to birth weight, at definite weight gain, when exclusively fed with formula, at 2000g, and when they reached 40 weeks of post-conceptional age. The AGA premature newborns on preterm formula had greater daily weight gain, cephalic circumference increase and growth. The SGA premature newborns on preterm formula had greater daily weight gain and cephalic circumference increase observed from the third week of life onward. The AGA premature newborns on modified formula had less weight gain and smaller increments in the cephalic circumference. The SGA premature on modified formula had the worst anthropometric results. The preterm formula was more efficient than the modified formula in promoting postnatal growth of AGA and SGA premature infants. We believe that, due to their special characteristics, SGA premature should receive individualized nutritional caloric planning 相似文献
104.
Severity of a case is one of the ingredients in management systems. Severity adjustment systems have limitations, and confusion and diversity characterize definitions of severity of a case. These facts may be a consequence of lack of conceptual knowledge. Based on a holistic theory of health, we introduce a definition of severity of a case from a patient perspective. Here severity is characterized as having two basic components: disease severity and illness severity; and five dimensions: suffering, disabilities, risk of suffering, risk of disabilities and risk of death. A classification of instruments as measures of severity dimensions is presented. This classification is based on definition and application criteria. The article's main contribution is to combine theoretical and practical knowledge about severity of a case, which may empower implementations of outcome management systems in health care. 相似文献
105.
Since exogenous hemin has been shown to exert a variety of stimulatory effects on erythroid cells, including the augmentation of hemoglobin synthesis, we determined its effect on early stages of erythroid development by employing clonal cells assays. The addition of hemin at a concentration of 2 X 10(-4) M to cultures of normal murine marrow substantially increased the observed number of primitive BFU-E, which was in contrast to its lack of an effect on more mature erythroid colony-forming cells. This cell-specific enhancement of primitive BFU-E resulted in marrow frequencies equivalent to or exceeding those reported in the presence of "burst-promoting activity." In the presence of hemin, the number of BFU-E was also observed to be linearly related to the number of cells plated at very low plating densities, and the cell titration curve was observed to extrapolate to the origin. The evidence suggests that hemin may be a primary growth regulator of early developmental stages of erythroid progenitor cells. 相似文献
106.
Chronic immobilization-induced stress increases plasma testosterone and delays testicular maturation in pubertal rats 总被引:2,自引:0,他引:2
We investigated whether chronic stress, applied from prepuberty to early puberty, interferes with the spermatogenic and androgenic testicular functions. Male pubertal rats (40 days old) were immobilized 6 h per day for 15 days. Plasma concentrations of corticosterone, prolactin and testosterone were significantly augmented following immobilization, whereas plasma luteinizing hormone decreased and follicle-stimulating hormone was not altered. Acute immobilization (5 min) increased prolactin and testosterone levels in control rats but caused a significantly higher increase in these hormones when superimposed on chronic stress. A lower extent of testicular maturation was observed in pubertal rats immobilized from prepuberty. 相似文献
107.
Quantitative analysis of bcl-2 expression in normal and leukemic human B-cell differentiation. 总被引:5,自引:0,他引:5
P Menendez A Vargas C Bueno S Barrena J Almeida M De Santiago A López S Roa J F San Miguel A Orfao 《Leukemia》2004,18(3):491-498
Lack of apoptosis has been linked to prolonged survival of malignant B cells expressing bcl-2. The aim of the present study was to analyze the amount of bcl-2 protein expressed along normal human B-cell maturation and to establish the frequency of aberrant bcl-2 expression in B-cell malignancies. In normal bone marrow (n=11), bcl-2 expression obtained by quantitative multiparametric flow cytometry was highly variable: very low in both CD34(+) and CD34(-) B-cell precursors, high in mature B-lymphocytes and very high in plasma cells. Bcl-2 expression of mature B-lymphocytes from peripheral blood (n=10), spleen (n=8) and lymph node (n=5) was significantly higher (P<0.02) in CD23(-) as compared to CD23(+) B cells, independent of the type of tissue analyzed. Upon comparison with normal human B-cell maturation, bcl-2 expression in neoplastic B cells from 144 patients was found to be aberrant in 66% of the cases, usually corresponding to bcl-2 overexpression (63%). Follicular lymphoma (FL) carrying t(14;18) and MALT lymphoma were the only diagnostic groups constantly showing overexpression of bcl-2. Bcl-2 overexpression was also frequently found in precursor B-acute lymphoblastic leukemia (84%), typical (77%) and atypical (75%) B-cell chronic lymphocytic leukemia, prolymphocytic leukemia (two of three cases), mantle cell lymphoma (55%), but not in t(14;18)(-) FL, splenic marginal zone lymphoma, Burkitt lymphoma and multiple myeloma. 相似文献
108.
This report describes the consequences and some aspects of the origin and development of victim blaming in accident analysis, and some methods for investigating such events, with particular emphasis on the situation in Brazil. In Brazil, the spread of this practice seems to have been helped by several factors. (1) The idea that occupational accidents are simple phenomena with a limited number of causal factors linked to unsafe actions and/or conditions. In the past, the theory of accident proneness had less influence than in other countries. (2) Government regulations that stipulate the hiring of health and safety officers, production of "educational" material, and "preventive" campaigns that emphasize the role of the victim's "faulty" behavior in the origin of an accident. (3) Mandatory implementation of standardized models for accident investigation directed toward searching for a single "cause." Usually one conclusion, expressed in terms of unsafe acts or conditions, is formulated so that whoever performs an unsafe act is responsible for the accident. (4) Lack of knowledge, as shown in Brazilian publications on occupational accidents and in the evolution of studies on the nature of accident phenomena and of strategies adopted for their prevention. 相似文献
109.
Assessment of the mutagenicity of dichloroacetic acid in lacI transgenic B6C3F1 mouse liver 总被引:2,自引:0,他引:2
Dichloroacetic acid (DCA) is a chlorination byproduct found in finished
drinking water. When administered in drinking water this chemical has been
shown to produce hepatocellular adenomas and carcinomas in B6C3F1 mice over
the animal's lifetime. In this study, we investigated whether mutant
frequencies were increased in mouse liver using treatment protocols that
yielded significant tumor induction. DCA was administered continuously at
either 1.0 or 3.5 g/l in drinking water to male transgenic B6C3F1 mice
harboring the bacterial lacI gene. Groups of five or six animals were
killed at 4, 10 or 60 weeks and livers removed. At both 4 and 10 weeks of
treatment, there was no significant difference in mutant frequency between
the treated and control animals at either dose level. At 60 weeks, mice
treated with 1.0 g/l DCA showed a 1.3-fold increase in mutant frequency
over concurrent controls (P = 0.05). Mice treated with 3.5 g/l DCA for 60
weeks had a 2.3-fold increase in mutant frequency over the concurrent
controls (P = 0.002). The mutation spectrum recovered from mice treated
with 3.5 g/l DCA for 60 weeks contained G:C-->A:T transitions (32.79%)
and G:C-->T:A transversions (21.31%). In contrast, G:C-->A:T
transitions comprised 53.19% of the recovered mutants among control
animals. Although only 19.15% of mutations among the controls were at T:A
sites, 32.79% of the mutations from DCA-treated animals were at T:A sites.
This is consistent with the previous observation that the proportion of
mutations at T:A sites in codon 61 of the H-ras gene was increased in
DCA-induced liver tumors in B6C3F1 mice. The present study demonstrates
DCA-associated mutagenicity in the mouse liver under conditions in which
DCA produces hepatic tumors.
相似文献
110.
Fatty acid balance studies in term infants fed formula milk containing long-chain polyunsaturated fatty acids 总被引:1,自引:0,他引:1
C Morgan L Davies F Corcoran J Stammers J Colley SA Spencer D Hull 《Acta paediatrica (Oslo, Norway : 1992)》1998,87(2):136-142
Long-chain polyunsaturated fatty acids (LCP) are thought to be required for optimal nervous system development in the newborn. A commercial milk formula containing LCP (Aptamil-LCP) with a fatty acid profile closely resembling breast milk, has recently been introduced for term infants. The absorption of fatty acids in term infants was examined in a double-blind randomized controlled trial comparing Aptamil-LCP ( n = 20) and standard Aptamil ( n = 20). Formula-fed newborn infants were studied from birth for 14 d. Fat balances (3 d) were performed from d 10. A 3-d stool collection was performed from d 10 in a parallel breastfed group ( n = 21). Plasma samples were taken on d 6. Median fat excretion (mg kg−1 ) was 897.1, 615.0 and 355.2 with Aptamil, Aptamil-LCP and breastfeeding, respectively. The median total fat absorption coefficient in Aptamil-LCP-fed infants was higher than in those fed standard Aptamil ( p < 0:01). These findings were accounted for by differences in the excretion and absorption of long-chain saturated fatty acids (C14:0, C16:0 and C18:0). Higher fat excretion was associated with bulkier and firmer stools. Only trace amounts of LCP were detected in the stools of all groups. This accounted for less than 4% of dietary intake in Aptamil-LCP-fed infants. No differences in the utilization of LCP from Aptamil-LCP and breast milk feeding were apparent. Plasma phospholipid fatty acid composition data reflected differences in dietary LCP intake. Thus, PL LCP levels were highest in the breastfed infants and lowest in the Aptamil-fed infants, with values for the Aptamil-LCP-fed group falling in between. 相似文献