全文获取类型
收费全文 | 25213篇 |
免费 | 2367篇 |
国内免费 | 65篇 |
专业分类
耳鼻咽喉 | 262篇 |
儿科学 | 564篇 |
妇产科学 | 352篇 |
基础医学 | 3107篇 |
口腔科学 | 795篇 |
临床医学 | 3281篇 |
内科学 | 5388篇 |
皮肤病学 | 611篇 |
神经病学 | 1889篇 |
特种医学 | 964篇 |
外科学 | 3552篇 |
综合类 | 457篇 |
一般理论 | 24篇 |
预防医学 | 2713篇 |
眼科学 | 353篇 |
药学 | 1986篇 |
中国医学 | 24篇 |
肿瘤学 | 1323篇 |
出版年
2021年 | 372篇 |
2020年 | 216篇 |
2019年 | 357篇 |
2018年 | 390篇 |
2017年 | 283篇 |
2016年 | 342篇 |
2015年 | 387篇 |
2014年 | 530篇 |
2013年 | 849篇 |
2012年 | 1161篇 |
2011年 | 1151篇 |
2010年 | 636篇 |
2009年 | 581篇 |
2008年 | 1056篇 |
2007年 | 1066篇 |
2006年 | 1098篇 |
2005年 | 1118篇 |
2004年 | 1037篇 |
2003年 | 980篇 |
2002年 | 981篇 |
2001年 | 976篇 |
2000年 | 1004篇 |
1999年 | 844篇 |
1998年 | 297篇 |
1997年 | 252篇 |
1996年 | 237篇 |
1995年 | 251篇 |
1994年 | 201篇 |
1993年 | 206篇 |
1992年 | 608篇 |
1991年 | 629篇 |
1990年 | 583篇 |
1989年 | 515篇 |
1988年 | 484篇 |
1987年 | 478篇 |
1986年 | 474篇 |
1985年 | 470篇 |
1984年 | 339篇 |
1983年 | 293篇 |
1982年 | 217篇 |
1981年 | 205篇 |
1979年 | 324篇 |
1978年 | 238篇 |
1977年 | 201篇 |
1975年 | 165篇 |
1974年 | 214篇 |
1973年 | 204篇 |
1972年 | 169篇 |
1971年 | 192篇 |
1970年 | 170篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
White WB 《Blood pressure monitoring》2008,13(2):123-129
Poor control of clinic and 24-h blood pressure (BP) is associated with enhanced risk of all cardiovascular disease events. Certain patient groups including the elderly, African-Americans, and those with hypertension and comorbid disease are difficult to control, as are patients with stage 2 hypertension (systolic BP>or=160 mmHg or diastolic BP>or=100 mmHg). It has been estimated that more than two-thirds of high-risk hypertensive patients with stage 2 hypertension and all hypertensive patients with diabetes mellitus or kidney disease will require two or more antihypertensive agents from different therapeutic classes to reach BP goals. Combining agents with distinct and complementary modes of action can address different pathophysiologic mechanisms involved in hypertension and may lead to more complete and prompt reductions in BP. Tolerability may also improve, as certain classes of antihypertensive agents ameliorate adverse effects associated with other agents. Patients may benefit from fixed-dose combinations of drugs as this simplifies the regimen and may improve adherence with therapy, control of BP, and ultimately lead to reductions in cardiovascular events. Recent data and treatment guidelines support the use of a combination strategy as 'initial' antihypertensive therapy in high-risk patients with stage 2 hypertension. 相似文献
992.
993.
Mandeep Singh Jennifer White David Hasdai Patricia K Hodgson Peter B Berger Eric J Topol Robert M Califf David R Holmes 《Journal of the American College of Cardiology》2007,50(18):1752-1758
OBJECTIVES: This study sought to assess long-term outcome and determine its predictors among 30-day survivors of cardiogenic shock. BACKGROUND: Patients with cardiogenic shock have high in-hospital and 30-day mortality, but there are little data about those who survive beyond 30 days. METHODS: We analyzed baseline, in-hospital, and survival data from patients in the U.S. with ST-segment elevation myocardial infarction (STEMI) and cardiogenic shock enrolled in the GUSTO (Global Utilization of Streptokinase and Tissue-Type Plasminogen Activator for Occluded Coronary Arteries)-I trial and compared them with patients in the same trial who did not have shock. RESULTS: Of 22,883 patients enrolled in the U.S., shock occurred in 1,891 (8.3%); 953 (50.4%) survived 30 days and 527 (27.8%) survived 11 years. Of 20,992 U.S. patients without shock, 20,360 (96.9%) survived 30 days and 14,131 (67.3%) survived 11 years. After the first year, 2% to 4% of patients died each year regardless of whether they had cardiogenic shock. Using Cox proportional hazards models, we were able to predict long-term mortality in all U.S. GUSTO-I 30-day survivors from their baseline demographics and in-hospital complications. The strongest predictors were diabetes mellitus, cardiogenic shock, hypertension, previous myocardial infarction, current smoking, anterior infarct, higher Killip class, higher heart rate, and older age; patients >75 years were at highest risk. Percutaneous revascularization during the index hospitalization was associated with a reduced risk of death. CONCLUSIONS: Among patients with cardiogenic shock who survive 30 days after STEMI, annual mortality rates of 2% to 4% approximate those of patients without shock. 相似文献
994.
995.
Absolute requirement of spermidine for growth and cell cycle progression of fission yeast (Schizosaccharomyces pombe)
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Chattopadhyay MK Tabor CW Tabor H 《Proceedings of the National Academy of Sciences of the United States of America》2002,99(16):10330-10334
Schizosaccharomyces pombe cells that cannot synthesize spermidine or spermine because of a deletion-insertion in the gene coding for S-adenosylmethionine decarboxylase (Deltaspe2) have an absolute requirement for spermidine for growth. Flow cytometry studies show that in the absence of spermidine an overall delay of the cell cycle progression occurs with some accumulation of cells in the G(1) phase; as little as 10(-6) M spermidine is sufficient to maintain normal cell cycle distribution and normal growth. Morphologically some of the spermidine-deprived cells become spherical at an early stage with little evidence of cell division. On further incubation in the spermidine-deprived medium, growth occurs in most of the cells, not by cell division but rather by cell elongation, with an abnormal distribution of the actin cytoskeleton, DNA (4', 6-diamidino-2-phenylindole staining), and calcofluor-staining moieties. More prolonged incubation in the spermidine-deficient medium leads to profound morphological changes including nuclear degeneration. 相似文献
996.
The fate of the open canalicular system in surface and suspension- activated platelets 总被引:6,自引:0,他引:6
We have examined the movement of fibrinogen-gold (fgn-Au) complexes in platelets activated in suspension and by surface contact. Fgn-Au probes did not react with resting cells but were bound to the external membrane of platelets in suspension 5 seconds after addition of 1 U/mL of thrombin. At intervals over a period of 5 to 20 minutes, fgn-Au probes moved from the cell surface to peripheral and then deep channels of the open canalicular system (OCS). When platelets were surface activated by exposure to carbon-stabilized, formvar-coated grids for 5 to 20 minutes and then exposed to fgn-Au complexes for 5 minutes, probes were also observed in the OCS. At 5 minutes, over 40% of the platelets had concentrated fgn-Au in their OCS. Results after 10 minutes revealed 25% with gold-filled channels, 16% after 15 minutes, and 5% after 20 minutes. The decrease in frequency of OCS staining correlated with the increasing frequency of spread platelets, suggesting that tension produced by spreading may cause collapse of the OCS or that the OCS may evaginate onto the platelet during spreading. To evaluate the latter hypothesis, platelets were initially exposed to grids for 5 minutes and then incubated with fgn-Au for intervals of 5 to 20 minutes. The frequency of platelets with fgn-Au concentrated in the OCS was greatest at 5 minutes (44%) and decreased at the same rate as the frequency of spread platelets increased. Only 14.7% of the cells contained fgn-Au in the OCS after 20 minutes. These were primarily dendritic in form, while fully spread platelets rarely contained an OCS filled with the probe. The study indicates that fgn-Au particles are cleared to channels of the OCS independent of the mechanism of platelet activation. Fgn-Au that has been concentrated in the OCS at early stages of surface activation can be externalized during platelet spreading but remain internalized in suspension-activated cells. The OCS represents a membrane reservoir that can be evaginated onto the platelet surface during interaction with surfaces. 相似文献
997.
Evidence that associative interactions between synapses during the induction of long-term potentiation occur within local dendritic domains.
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
G White W B Levy O Steward 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(7):2368-2372
The present study evaluates whether the associative interactions between synapses that lead to long-term potentiation and depression (LTP and LTD) can occur between spatially segregated synapses of the medial and lateral temporodentate pathway of the rat. Coconditioning of crossed and ipsilateral pathways resulted in LTP of the crossed system only when the current sinks of the two conditioned pathways overlapped sufficiently. Likewise, conditioning of an ipsilateral pathway alone resulted in LTD of the crossed pathway only when those current sinks overlapped sufficiently. These observations support the idea that associative events that lead to LTP or LTD can be restricted to a local dendritic domain. The postsynaptic cell can therefore serve as more than one unit of integration for synaptic modification. 相似文献
998.
S C Chua P Szabo A Vitek K H Grzeschik M John P C White 《Proceedings of the National Academy of Sciences of the United States of America》1987,84(20):7193-7197
We have isolated bovine and human adrenal cDNA clones encoding the adrenal cytochrome P-450 specific for 11 beta-hydroxylation (P450c11). A bovine adrenal cDNA library constructed in the bacteriophage lambda vector gt10 was probed with a previously isolated cDNA clone corresponding to part of the 3' untranslated region of the 4.2-kilobase (kb) mRNA encoding P450c11. Several clones with 3.2-kb cDNA inserts were isolated. Sequence analysis showed that they overlapped the original probe by 300 base pairs (bp). Combined cDNA and RNA sequence data demonstrated a continuous open reading frame of 1509 bases. P450c11 is predicted to contain 479 amino acid residues in the mature protein in addition to a 24-residue amino-terminal mitochondrial signal sequence. A bovine clone was used to isolate a homologous clone with a 3.5-kb insert from a human adrenal cDNA library. A region of 1100 bp was 81% homologous to 769 bp of the coding sequence of the bovine cDNA except for a 400-bp segment presumed to be an unprocessed intron. Hybridization of the human cDNA to DNA from a panel of human-rodent somatic cell hybrid lines and in situ hybridization to metaphase spreads of human chromosomes localized the gene to the middle of the long arm of chromosome 8. These data should be useful in developing reagents for heterozygote detection and prenatal diagnosis of 11 beta-hydroxylase deficiency, the second most frequent cause of congenital adrenal hyperplasia. 相似文献
999.
Tara N. HutchisonChad A. Krueger MD John S. BerryJames K. Aden PhD Stephen M. CohnChristopher E. White MD MSc 《The Journal of surgical research》2014
Background
This article examines the incidence of venous thromboembolism (VTE) in combat wounded, identifies risk factors for pulmonary embolism (PE), and compares the rate of PE in combat with previously reported civilian data.Methods
A retrospective review was performed of all U.S. military combat casualties in Operation Enduring Freedom and Operation Iraqi Freedom with a VTE recorded in the Department of Defense Trauma Registry from September 2001 to July 2011. The Military Amputation Database of all U.S. military amputations during the same 10-y period was also reviewed. Demographic data, injury characteristics, and outcomes were evaluated.Results
Among 26,634 subjects, 587 (2.2%) had a VTE. This number included 270 subjects (1.0%) with deep venous thrombosis (DVT), 223 (0.8%) with PE, and 94 (0.4%) with both DVT and PE. Lower extremity amputation was independently associated with PE (odds ratio [OR], 1.70; 95% confidence interval [CI], 1.07–2.69). A total of 1003 subjects suffered a lower extremity amputation, with 174 (17%) having a VTE. Of these, 75 subjects (7.5%) were having DVT, 70 (7.0%) were having PE, and 29 (2.9%) were found to have both a DVT and a PE. Risk factors found to be independently associated with VTE in amputees were multiple amputations (OR, 2; 95% CI, 1.35–3.42) and above the knee amputation (OR, 2.11; 95% CI, 1.3–3.32).Conclusions
Combat wounded are at a high risk for thromboembolic complications with the highest risk associated with multiple or above the knee amputations. 相似文献1000.