全文获取类型
收费全文 | 7774篇 |
免费 | 718篇 |
国内免费 | 53篇 |
专业分类
耳鼻咽喉 | 63篇 |
儿科学 | 286篇 |
妇产科学 | 270篇 |
基础医学 | 873篇 |
口腔科学 | 154篇 |
临床医学 | 832篇 |
内科学 | 1834篇 |
皮肤病学 | 148篇 |
神经病学 | 868篇 |
特种医学 | 338篇 |
外国民族医学 | 1篇 |
外科学 | 1135篇 |
综合类 | 266篇 |
一般理论 | 3篇 |
预防医学 | 588篇 |
眼科学 | 69篇 |
药学 | 389篇 |
肿瘤学 | 428篇 |
出版年
2021年 | 78篇 |
2018年 | 83篇 |
2016年 | 75篇 |
2015年 | 97篇 |
2014年 | 123篇 |
2013年 | 179篇 |
2012年 | 273篇 |
2011年 | 284篇 |
2010年 | 162篇 |
2009年 | 150篇 |
2008年 | 281篇 |
2007年 | 312篇 |
2006年 | 266篇 |
2005年 | 255篇 |
2004年 | 274篇 |
2003年 | 305篇 |
2002年 | 271篇 |
2001年 | 253篇 |
2000年 | 287篇 |
1999年 | 230篇 |
1998年 | 124篇 |
1997年 | 97篇 |
1996年 | 101篇 |
1995年 | 87篇 |
1994年 | 87篇 |
1993年 | 98篇 |
1992年 | 219篇 |
1991年 | 234篇 |
1990年 | 211篇 |
1989年 | 201篇 |
1988年 | 234篇 |
1987年 | 214篇 |
1986年 | 212篇 |
1985年 | 187篇 |
1984年 | 179篇 |
1983年 | 151篇 |
1982年 | 98篇 |
1981年 | 90篇 |
1980年 | 81篇 |
1979年 | 136篇 |
1978年 | 83篇 |
1977年 | 88篇 |
1976年 | 85篇 |
1975年 | 69篇 |
1974年 | 96篇 |
1973年 | 91篇 |
1972年 | 87篇 |
1971年 | 77篇 |
1970年 | 71篇 |
1969年 | 73篇 |
排序方式: 共有8545条查询结果,搜索用时 15 毫秒
81.
Linear regression of eye velocity on eye position and head velocity suggests a common oculomotor neural integrator 总被引:3,自引:0,他引:3
Goldman MS Kaneko CR Major G Aksay E Tank DW Seung HS 《Journal of neurophysiology》2002,88(2):659-665
The oculomotor system produces eye-position signals during fixations and head movements by integrating velocity-coded saccadic and vestibular inputs. A previous analysis of nucleus prepositus hypoglossi (nph) lesions in monkeys found that the integration time constant for maintaining fixations decreased, while that for the vestibulo-ocular reflex (VOR) did not. On this basis, it was concluded that saccadic inputs are integrated by the nph, but that the vestibular inputs are integrated elsewhere. We re-analyze the data from which this conclusion was drawn by performing a linear regression of eye velocity on eye position and head velocity to derive the time constant and velocity bias of an imperfect oculomotor neural integrator. The velocity-position regression procedure reveals that the integration time constants for both VOR and saccades decrease in tandem with consecutive nph lesions, consistent with the hypothesis of a single common integrator. The previous evaluation of the integrator time constant relied upon fitting methods that are prone to error in the presence of velocity bias and saccades. The algorithm used to evaluate imperfect fixations in the dark did not account for the nonzero null position of the eyes associated with velocity bias. The phase-shift analysis used in evaluating the response to sinusoidal vestibular input neglects the effect of saccadic resets of eye position on intersaccadic eye velocity, resulting in gross underestimates of the imperfections in integration during VOR. The linear regression method presented here is valid for both fixation and low head velocity VOR data and is easy to implement. 相似文献
82.
Targeting the BCR-ABL tyrosine kinase in chronic myeloid leukemia 总被引:19,自引:0,他引:19
83.
Detection of reactive oxygen species (ROS) and apoptosis in human fragmented embryos 总被引:8,自引:2,他引:8
Yang HW; Hwang KJ; Kwon HC; Kim HS; Choi KW; Oh KS 《Human reproduction (Oxford, England)》1998,13(4):998-1002
In human in-vitro fertilization (IVF)-embryo transfer, the in-vitro culture
environment differs from in-vivo conditions in that the oxygen
concentration is higher, and in such conditions the mouse embryos show a
higher concentration of reactive oxygen species (ROS) in simple culture
media. ROS are believed to cause damage to cell membranes and DNA
fragmentation in somatic cells. This study was conducted to ascertain the
level of H2O2 concentration within embryos and the morphological features
of cell damage induced by H2O2. A total of 62 human oocytes and embryos (31
fragmented, 15 non-fragmented embryos, 16 unfertilized oocytes) was
obtained from the IVF-embryo transfer programme. The relative intensity of
H2O2 concentrations within embryos was measured using
2',7'-dichlorodihydrofluorescein diacetate by Quanti cell 500 fluorescence
imaging and DNA fragmentation was observed with transmission electron
microscopy and an in-situ apoptosis detection kit. The H2O2 concentrations
were significantly higher in fragmented embryos (72.21 +/- 9.62, mean +/-
SEM) compared to non-fragmented embryos (31.30 +/- 3.50, P < 0.05) and
unfertilized oocytes (30.75 +/- 2.67, P < 0.05). Apoptosis was observed
only in fragmented embryos, and was absent in non-fragmented embryos.
Electron microscopic findings confirmed apoptotic bodies and cytoplasmic
condensation in the fragmented blastomeres. We conclude that there is a
direct relationship between increased H2O2 concentration and apoptosis, and
that further studies should be undertaken to confirm these findings.
相似文献
84.
Stein TP; Oram-Smith JC; Leskiw MJ; Wallace HW; Long LC; Leonard JM 《The American journal of physiology》1976,230(5):1321-1325
85.
Chronic exposure to superantigen induces regulatory CD4(+) T cells with IL-10-mediated suppressive activity 总被引:4,自引:0,他引:4
The repeated injection of bacterial superantigens (SAg), such as staphylococcus enterotoxin (SE) A or B, has been shown in mice to induce a state of unresponsiveness characterized by the lack of secretion of Th1 lymphokines, such as IL-2 and IFN-gamma, following subsequent SAg challenge. We made the observation, in vivo as well as in vitro, that unresponsiveness to SAg could be transferred from SEA- to SEB-reactive T cells (and reversibly from SEB- to SEA-specific T cells) in C57BL/6 mice but not in BALB/c mice. Since C57BL/6 mice, unlike BALB/c mice, possess TCR V(beta)3+ and V(beta)11+ T cells able to react with both SEA and SEB, we hypothesized that SAg-unresponsive V(beta)3(+) and V(beta)11+ T cells could mediate linked suppression of other SAg-reactive T cells. To analyze further this possibility, spleen cells from BALB/c mice made unresponsive to SEB were tested for their capacity to suppress the response of normal BALB/c cells to SEB. The production of both IFN-gamma and IL-2 following SEB stimulation was greatly impaired in co-cultures containing CD4(+) T cells, but not CD8(+) T cells, isolated from unresponsive animals. In vivo, the production of both IFN-gamma and IL-2 responses to SEB was dramatically reduced in animals adoptively transferred with unresponsive spleen cells. This suppression was abrogated in recipients injected with neutralizing anti-IL-10 antibodies. Moreover, in animals made unresponsive to SEB, SAg-reactive CD4(+) T cells were found to express high levels of CTLA-4, a molecule recently described to play an essential role in the suppressive function of regulatory T cells. Taken together these results demonstrate that the repetitive injection of SAg induces the differentiation of regulatory CD4(+) T cells capable of suppressing SAg-reactive naive T cells. 相似文献
86.
87.
Immune monitoring in whole blood using real-time PCR 总被引:7,自引:0,他引:7
Stordeur P Zhou L Byl B Brohet F Burny W de Groote D van der Poll T Goldman M 《Journal of immunological methods》2003,276(1-2):69-77
88.
Interchromosomal duplications of the adrenoleukodystrophy locus: a phenomenon of pericentromeric plasticity 总被引:13,自引:5,他引:13
Eichler EE; Budarf ML; Rocchi M; Deaven LL; Doggett NA; Baldini A; Nelson DL; Mohrenweiser HW 《Human molecular genetics》1997,6(7):991-1002
A 9.7 kb segment encompassing exons 7-10 of the adrenoleukodystrophy (ALD)
locus of the X chromosome has duplicated to specific locations near the
pericentromeric regions of human chromosomes 2p11,10p11, 16p11 and 22q11.
Comparative sequence analysis reveals 92-96% nucleotide identity,
indicating that the autosomal ALD paralogs arose relatively recently during
the course of higher primate evolution (5-10 million years ago). Analysis
of sequences flanking the duplication region identifies the presence of an
unusual GCTTTTTGC repeat which may be a sequence-specific integration site
for the process of pericentromeric- directed transposition. The breakpoint
sequence and phylogenetic analysis predict a two-step transposition model,
in which a duplication from Xq28 to pericentromeric 2p11 occurred once,
followed by a rapid distribution of a larger duplicon cassette among the
pericentromeric regions. In addition to facilitating more effective
mutation detection among ALD patients, these findings provide further
insight into the molecular basis underlying a pericentromeric-directed
mechanism for non- homologous interchromosomal exchange.
相似文献
89.
Bozzette SA Joyce G McCaffrey DF Leibowitz AA Morton SC Berry SH Rastegar A Timberlake D Shapiro MF Goldman DP;HIV Cost Services Utilization Study Consortium 《The New England journal of medicine》2001,344(11):817-823
BACKGROUND: The introduction of expensive but very effective antiviral medications has led to questions about the effects on the total use of resources for the care of patients with human immunodeficiency virus (HIV) infection. We examined expenditures for the care of HIV-infected patients since the introduction of highly active antiretroviral therapy. METHODS: We interviewed a random sample of 2864 patients who were representative of all American adults receiving care for HIV infection in early 1996, and followed them for up to 36 months. We estimated the average expenditure per patient per month on the basis of self-reported information about care received. RESULTS: The mean expenditure was $1,792 per patient per month at base line, but it declined to $1,359 for survivors in 1997, since the increases in pharmaceutical expenditures were smaller than the reductions in hospital costs. Use of highly active antiretroviral therapy was independently associated with a reduction in expenditures. After adjustments for the interview date, clinical status, and deaths, the estimated annual expenditure declined from $20,300 per patient in 1996 to $18,300 in 1998. Expenditures among subgroups of patients varied by a factor of as much as three. Pharmaceutical costs were lowest and hospital costs highest among underserved groups, including blacks, women, and patients without private insurance. CONCLUSIONS: The total cost of care for adults with HIV infection has declined since the introduction of highly active antiretroviral therapy. Expenditures have increased for medications but have declined for other services. However, there are large variations in expenditures across subgroups of patients. 相似文献
90.
Feng J Yan J Michaud S Craddock N Jones IR Cook EH Goldman D Heston LL Peltonen L Delisi LE Sommer SS 《American journal of medical genetics》2001,105(4):369-374
Estrogen and thyroid hormones exert effects on growth, development, and differentiation of the nervous system. Hormone administration can lead to changes in behavior, suggesting that genetic variants of the estrogen receptor alpha (ERalpha) and the thyroid hormone receptor alpha (TRalpha) genes may predispose to psychiatric diseases. To investigate this possibility, regions of likely functional significance (all coding exons and flanking splice junctions) of the ERalpha and TRalpha genes were scanned in patients with schizophrenia (113), along with pilot studies in patients with bipolar illness (BPI), puerperal psychosis, autism, attention-deficit hyperactivity disorder (ADHD), and alcoholism. A total of 1.18 megabases of the ERalpha gene and 1.16 megabases of the TRalpha gene were scanned with Detection of Virtually All Mutations-SSCP (DOVAM-S), a method that detects virtually all mutations. Four missense mutations, seven silent mutations and one deletion were identified in the ERalpha gene, while only four silent mutations were present in the TRalpha gene. Two of the missense mutations in ERalpha are conserved in the six available mammalian and bird species (H6Y, K299R) and a third sequence variant (P146Q) is conserved in mammals, birds, and Xenopus laevis, hinting that these sequence changes will be of functional significance. These changes were found in one patient each with BPI, puerperal psychosis, and alcoholism, respectively. Analysis of the ERalpha and TRalpha genes in 240 subjects reveals that missense changes and splice site variants are uncommon (1.7% and 0%, respectively). Further analyses are necessary to determine if the missense mutations identified in this study are associated with predisposition or outcome for either psychiatric or nonpsychiatric diseases. 相似文献