全文获取类型
收费全文 | 45215篇 |
免费 | 2729篇 |
国内免费 | 258篇 |
专业分类
耳鼻咽喉 | 389篇 |
儿科学 | 1305篇 |
妇产科学 | 1207篇 |
基础医学 | 5928篇 |
口腔科学 | 939篇 |
临床医学 | 4501篇 |
内科学 | 9937篇 |
皮肤病学 | 881篇 |
神经病学 | 4807篇 |
特种医学 | 1518篇 |
外科学 | 5927篇 |
综合类 | 175篇 |
一般理论 | 19篇 |
预防医学 | 3356篇 |
眼科学 | 768篇 |
药学 | 2785篇 |
1篇 | |
中国医学 | 85篇 |
肿瘤学 | 3674篇 |
出版年
2024年 | 70篇 |
2023年 | 521篇 |
2022年 | 1001篇 |
2021年 | 1808篇 |
2020年 | 1057篇 |
2019年 | 1487篇 |
2018年 | 1700篇 |
2017年 | 1194篇 |
2016年 | 1342篇 |
2015年 | 1549篇 |
2014年 | 2129篇 |
2013年 | 2651篇 |
2012年 | 3921篇 |
2011年 | 3909篇 |
2010年 | 1978篇 |
2009年 | 1851篇 |
2008年 | 3123篇 |
2007年 | 3007篇 |
2006年 | 2713篇 |
2005年 | 2679篇 |
2004年 | 2245篇 |
2003年 | 2007篇 |
2002年 | 1774篇 |
2001年 | 232篇 |
2000年 | 164篇 |
1999年 | 235篇 |
1998年 | 303篇 |
1997年 | 223篇 |
1996年 | 200篇 |
1995年 | 181篇 |
1994年 | 154篇 |
1993年 | 122篇 |
1992年 | 89篇 |
1991年 | 80篇 |
1990年 | 68篇 |
1989年 | 44篇 |
1988年 | 45篇 |
1987年 | 39篇 |
1986年 | 35篇 |
1985年 | 33篇 |
1984年 | 44篇 |
1983年 | 20篇 |
1982年 | 42篇 |
1981年 | 26篇 |
1980年 | 23篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Gerhard Koßmehl Andrea Fluthwedel Horst Schfer 《Macromolecular chemistry and physics.》1992,193(1):157-166
Basic materials for contact lenses were obtained by radical copolymerization of linear α,ω-bis(methacryloyloxy)-terminated oligo- and poly(dimethylsiloxane)s, methyl methacrylate and 2,2,3,3,4,4,4-heptafuorobutyl methacrylate. Oxygen permeabilities, contact angles and ball indentation hardness were determined. 相似文献
22.
Barry W McColl Ailsa L McGregor Andrew Wong Julian D Harris Andrea Amalfitano Sandra Magnoni Andrew H Baker George Dickson Karen Horsburgh 《Journal of cerebral blood flow and metabolism》2007,27(3):477-487
Apolipoprotein E (apoE, protein; APOE, gene) is the major lipid-transport protein in the brain and plays an important role in modulating the outcome and regenerative processes after acute brain injury. The aim of the present study was to determine if gene transfer of the epsilon3 form of APOE improves outcome in a murine model of transient focal cerebral ischaemia. Mice received an intrastriatal injection of vehicle, a second-generation adenoviral vector containing the green fluorescent protein gene (Ad-GFP) or a vector containing the APOE epsilon3 gene (Ad-APOE) 3 days before 60 mins focal ischaemia. Green fluorescent protein expression was observed in cells throughout the striatum and subcortical white matter indicating successful gene transfer and expression. ApoE levels in the brain were significantly increased after Ad-APOE compared with Ad-GFP or vehicle treatment. Ad-APOE treatment reduced the volume of ischaemic damage by 50% compared with Ad-GFP or vehicle treatment (13+/-3 versus 29+/-4 versus 27+/-5 mm(3)). The extent of postischaemic apoE immunoreactivity was enhanced in Ad-APOE compared with Ad-GFP or vehicle treated mice. These results show the ability of APOE gene transfer to markedly improve outcome after cerebral ischaemia and suggest that modulating apoE levels may be a potential strategy in human stroke therapy. 相似文献
23.
Parvalbumin 3 is an Abundant Ca2+ Buffer in Hair Cells 总被引:3,自引:0,他引:3
Stefan Heller Andrea M. Bell Charlotte S. Denis Yong Choe A.J. Hudspeth 《Journal of the Association for Research in Otolaryngology》2002,3(4):488-498
Ca2+ signaling serves distinct purposes in different parts of a hair cell. The Ca2+ concentration in stereocilia regulates
adaptation and, through rapid transduction-channel reclosure, underlies amplification of mechanical signals. In presynaptic
active zones, Ca2+ mediates the exocytotic release of afferent neurotransmitter. At efferent synapses, Ca2+ activates the
K+ channels that dominate the inhibitory postsynaptic potential. A copious supply of diffusible protein buffer isolates the
three signals by restricting the spread of free Ca2+ and limiting the duration of its action. Using cDNA subtraction and a
gene expression assay based on in situ hybridization, we detected abundant expression of mRNAs encoding the Ca2+ buffer parvalbumin
3 in bullfrog saccular and chicken cochlear hair cells. We cloned cDNAs encoding this protein from the corresponding inner-ear
libraries and raised antisera against recombinant bullfrog parvalbumin 3. Immunohistochemical labeling indicated that parvalbumin
3 is a prominent Ca2+-binding protein in the compact, cylindrical hair cells of the bullfrog's sacculus, and occurs as well
in the narrow, peanut-shaped hair cells of that organ. Using quantitative Western blot analysis, we ascertained that the concentration
of parvalbumin 3 in saccular hair cells is approximately 3 mM. Parvalbumin 3 is therefore a significant mobile Ca2+ buffer,
and perhaps the dominant buffer, in many types of hair cell. Moreover, parvalbumin 3 provides an early marker for developing
hair cells in the frog, chicken, and zebrafish. 相似文献
24.
Andrea Sabbadini 《British Journal of Psychotherapy》1991,7(4):406-415
SUMMARY. I have examined the function of silence - its possible role and meanings - in the psychoanalytic encounter. I have argued that silence is complementary to words in general, and to analytic free-associations in particular, and that silence in the patient is often more than just the expression of his resistance.
It could be useful to consider the silent space within a session as a sort of container of words -words that, for complex, over-determined, unconscious reasons cannot be uttered. I have insisted on the significance of analytic silences and warned against responding to them either through a retaliatory silence or through a flood of premature interpretations. These inadequate reactions often stem from the analyst's own anxiety evoked in him by the patient's silence.
Anxiety and silence are closely connected. Each silence is a compromise formation, concealing the unconscious fantasy from which it originates, while expressing a conscious one, often related to the transference situation. It is the task of the analyst to listen to his patient's silences in order to help him understand their meanings. 相似文献
It could be useful to consider the silent space within a session as a sort of container of words -words that, for complex, over-determined, unconscious reasons cannot be uttered. I have insisted on the significance of analytic silences and warned against responding to them either through a retaliatory silence or through a flood of premature interpretations. These inadequate reactions often stem from the analyst's own anxiety evoked in him by the patient's silence.
Anxiety and silence are closely connected. Each silence is a compromise formation, concealing the unconscious fantasy from which it originates, while expressing a conscious one, often related to the transference situation. It is the task of the analyst to listen to his patient's silences in order to help him understand their meanings. 相似文献
25.
Abstract: Background : In response to rising cesarean rates, it is reasonable for health care organizations to look to a managed care model as a means of controlling further rate increases. However, little conclusive evidence exists to support this solution. We undertook a study of the Department of Defense health care beneficiary population to assess the impact of enrollment in TRICARE Prime, the Department's managed care health plan, on cesarean delivery rates. Methods : Pooled hospital discharge records from 1999–2002 for live, singleton births were analyzed to calculate primary and repeat cesarean rates for TRICARE Prime and non‐Prime beneficiaries in the military and civilian hospitals that comprise the Department of Defense health care network. Stepwise logistic regression was used to calculate adjusted odds ratios for clinical indicators for each combination of health plan and hospital setting using theχ2difference(p < 0.05)to eliminate nonsignificant variables from the model. Total primary and repeat cesarean rates were compared with primary and repeat cesarean rates for women with no reported clinical complications to account for differences in case mix across subgroups. Statistical significance of the differences calculated for subgroups was assessed usingχ2. Results : Primary cesarean rates were significantly lower for TRICARE Prime enrollees relative to non‐Prime beneficiaries for all race subgroups and three of five age subgroups in military hospitals and four of five age subgroups in civilian hospitals. No significant differences in repeat cesarean rates were observed between Prime and non‐Prime beneficiaries within any race or age subgroup. Breech presentation followed by dystocia, fetal distress, and other complications were significant predictors for primary cesarean. Previous cesarean delivery was the leading predictor for repeat cesarean delivery. Primary and repeat cesarean rates observed for military hospitals were consistently lower than rates observed for civilian hospitals within each health plan type and age group. Conclusions : Enrollment in the managed care health plan was significantly associated with lower risk of primary cesarean delivery relative to membership in other health plans offered to Department of Defense health care beneficiaries. Repeat cesarean rates in this population varied independently of health plan type. Primary cesarean delivery was generally associated with clinical complications, whereas previous cesarean delivery was the strongest indictor for a repeat cesarean delivery. A clear explanation of reduced cesarean rates for Prime enrollees remains elusive, but it is likely that factors beyond individual practitioner decision‐making were at work. 相似文献
26.
Mono- and bi-allelic expression of insulin-like growth factor II gene in human muscle tumors 总被引:4,自引:1,他引:3
Pedone Paolo V.; Tirabosco Roberto; Cavazzana Andrea O.; Ungaro Paola; Basso Giuseppe; Luksch Roberto; Carli Modesto; Bruni Carmelo B.; Frunzio Rodolfo; Riccio Andrea 《Human molecular genetics》1994,3(7):1117-1121
Insulin-like growth factor II (IGF-II) is a mitogen for manycell types and an important modulator of muscle growth and differentiation.IGF-II gene is prevalently expressed during prenatal developmentand its gene activity is regulated by genomic imprinting, inthat the allele inherited from the father is active and theallele inherited from the mother is inactive in most normaltissues. IGF-II expression is activated in several types ofhuman neoplasms and an alteration of IGF-II imprinting has beendescribed in BeckwithWiedemann syndrome and Wilms' tumour.Here we show that monoallelic expression of IGF-II gene is conservedin normal adult muscle tissue whereas two or more copies ofactive IGF-II alleles, arising by either relaxation of imprintingor duplication of the active allele, are found in 9 out of 11(82%) rhabdomyo-sarcomas retaining heterozygosity at 11p15,regardless of the histological subtype. Since IGF-II has beenindicated as an autocrine growth factor for rhabdomyosarcomacells, these findings strongly suggest that acquisition of adouble dosage of active IGF-II gene is an important step forthe initiation or progression of rhabdomyosarcoma tumorigenesis.Among different types of muscle tumors, relaxation of imprintingseems to arise prevalently in rhabdomyosarcomas, since we havedetected only one case of partial reactivation of the maternalIGF-II allele out of 7 lelomyosarcomas tested. 相似文献
27.
Thomas M. Gehring PhD Daniel Marti MS MD Andrea Sidler MA 《Child psychiatry and human development》1994,25(2):125-138
Perceptions of family cohesion and hierarchy structures were assessed by theFamily System Test (FAST), a clinically-derived figure placement technique. Parents (N=140) and their preadolescent offspring (N=70) completed typical and conflict representations in individual as well as group settings. Typical representations were characterized by balanced family structures (i.e. cohesive and moderately hierarchical) and those displaying conflict situations showed predominantly unbalanced patterns. FAST portrayals were related to respondent (mother vs. father vs. child). Fathers represented typical family relations as balanced more often than mothers. Regarding conflict representations, children were more likely than fathers to portray the family as unbalanced. However, analyses of representations of the same family (i.e. intra-family comparisons) indicated that all respondents differed in their perceptions and, that fathers' typical portrayals showed most often the same structure as those done by the family members as a group. 相似文献
28.
Angelo Pan Placido Mondello Klara Posfay-Barbe Patrizia Catenazzi Annise Grandi Silvia Lorenzotti Andrea Patroni Nadia Poli Laura Soavi Giuseppe Carnevale 《Infection control and hospital epidemiology》2007,28(9):1099-1102
In an Italian hospital, we observed that hand hygiene was performed in 638 (19.6%) of 3,253 opportunities, whereas gloves were worn in 538 (44.2%) 1,218 of opportunities. We observed an inverse correlation between the intensity of care and the rate of hand hygiene compliance (R2=0.057; P<.001), but no such association was observed for the rate of glove use compliance (R2=0.014; P=.078). Rates of compliance with hand hygiene and glove use recommendations follow different behavioral patterns. 相似文献
29.
Identification of the C-terminal flanking peptide of preprocholecystokinin in rat brain by a novel radioimmunoassay 总被引:1,自引:0,他引:1
The C-terminal flanking peptide of preprocholecystokinin (preproCCK) has been identified in extracts of rat brain using a novel radioimmunoassay. There is a single form of immunoreactive material on gel filtration, ion exchange and reversed-phase HPLC. The C-terminal preproCCK immunoreactivity had a similar pattern of distribution to CCK8 in different regions of rat brain. This assay should help in studies of neuronal CCK biosynthesis. 相似文献
30.
Andrea Frudinger Research Registrar Clive I. Bartram Consultant John A. D. Spencer Consultant Michael A. Kamm Consultant 《BJOG : an international journal of obstetrics and gynaecology》1997,104(9):1009-1013
Objective To assess the relation between perineal inspection and sphincter integrity in parous women.
Design Prospective observational study.
Setting District general hospital.
Population Fifty-seven consecutive parous women attending a gynaecology clinic for problems unrelated to the pelvic floor.
Methods A detailed history of bowel function and mode of delivery obtained; the perineum inspected to determine the presence and position of scarring, and anal endosonography performed.
Results In 19 women with an intact perineum on inspection, endosonography showed perineal scarring in five, with both perineal and sphincter scarring in three. Four had urge faecal incontinence. Three patients had a perineal tear only on inspection, but this group was too small for analysis and was discounted. Nine had an episiotomy scar only. Endosonography demonstrated perineal scarring in four, and combined perineal and sphincter scarring in two; one woman in this group had urge faecal incontinence. Twenty-six women had episiotomy and perineal tears on inspection. Endosonography revealed underlying perineal scarring in five women, with combined perineal and sphincter scarring in 14; six women in this group had urge faecal incontinence and one passive incontinence for flatus. Sonographically the scarring was anterior and circumferential rather than radial, and mostly left-sided, whereas on inspection episiotomy and perineal scarring were right sided.
Conclusions A normal perineum on clinical examination does not exclude underlying sphincter damage. The incidence of sphincter damage increases significantly when an episiotomy scar is associated with a perineal tear. 相似文献
Design Prospective observational study.
Setting District general hospital.
Population Fifty-seven consecutive parous women attending a gynaecology clinic for problems unrelated to the pelvic floor.
Methods A detailed history of bowel function and mode of delivery obtained; the perineum inspected to determine the presence and position of scarring, and anal endosonography performed.
Results In 19 women with an intact perineum on inspection, endosonography showed perineal scarring in five, with both perineal and sphincter scarring in three. Four had urge faecal incontinence. Three patients had a perineal tear only on inspection, but this group was too small for analysis and was discounted. Nine had an episiotomy scar only. Endosonography demonstrated perineal scarring in four, and combined perineal and sphincter scarring in two; one woman in this group had urge faecal incontinence. Twenty-six women had episiotomy and perineal tears on inspection. Endosonography revealed underlying perineal scarring in five women, with combined perineal and sphincter scarring in 14; six women in this group had urge faecal incontinence and one passive incontinence for flatus. Sonographically the scarring was anterior and circumferential rather than radial, and mostly left-sided, whereas on inspection episiotomy and perineal scarring were right sided.
Conclusions A normal perineum on clinical examination does not exclude underlying sphincter damage. The incidence of sphincter damage increases significantly when an episiotomy scar is associated with a perineal tear. 相似文献