全文获取类型
收费全文 | 5607篇 |
免费 | 265篇 |
国内免费 | 58篇 |
专业分类
耳鼻咽喉 | 63篇 |
儿科学 | 75篇 |
妇产科学 | 141篇 |
基础医学 | 422篇 |
口腔科学 | 181篇 |
临床医学 | 376篇 |
内科学 | 1426篇 |
皮肤病学 | 184篇 |
神经病学 | 518篇 |
特种医学 | 228篇 |
外科学 | 914篇 |
综合类 | 35篇 |
预防医学 | 323篇 |
眼科学 | 168篇 |
药学 | 262篇 |
中国医学 | 6篇 |
肿瘤学 | 608篇 |
出版年
2024年 | 5篇 |
2023年 | 38篇 |
2022年 | 97篇 |
2021年 | 142篇 |
2020年 | 95篇 |
2019年 | 107篇 |
2018年 | 151篇 |
2017年 | 104篇 |
2016年 | 151篇 |
2015年 | 162篇 |
2014年 | 245篇 |
2013年 | 303篇 |
2012年 | 442篇 |
2011年 | 513篇 |
2010年 | 280篇 |
2009年 | 264篇 |
2008年 | 454篇 |
2007年 | 457篇 |
2006年 | 401篇 |
2005年 | 388篇 |
2004年 | 330篇 |
2003年 | 284篇 |
2002年 | 230篇 |
2001年 | 35篇 |
2000年 | 22篇 |
1999年 | 39篇 |
1998年 | 42篇 |
1997年 | 27篇 |
1996年 | 23篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 3篇 |
1992年 | 10篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1963年 | 1篇 |
排序方式: 共有5930条查询结果,搜索用时 15 毫秒
41.
42.
Utility of screening for other causes of infertility in women with "known" polycystic ovary syndrome
McGovern PG Legro RS Myers ER Barnhart HX Carson SA Diamond MP Carr BR Schlaff WD Coutifaris C Steinkampf MP Nestler JE Gosman G Leppert PC Giudice LC;National Institutes for Child Health Human Development-Reproductive Medicine Network 《Fertility and sterility》2007,87(2):442-444
We investigated the prevalence of abnormal screening results (questionnaire and testing for other causes of oligo-ovulation, male or tubal factor infertility) in a group of 1,313 oligo-ovulatory women (included and excluded subjects) whose condition was screened for inclusion in the Pregnancy in Polycystic Ovary Syndrome trial, a multicenter clinical trial that was conducted at 13 sites in the United States. Other than failure to demonstrate laboratory evidence of hyperandrogenemia, the most common reasons for subject exclusion were persistent oligospermia and tubal factor infertility. 相似文献
43.
BACKGROUND: Naturally occurring heterotopic pregnancy is rare. A surviving intrauterine pregnancy associated with a ruptured tubal pregnancy is extremely unusual. CASE: This is the first reported case of a patient presenting in hemorrhagic shock due to a ruptured tubal pregnancy that was associated with an ongoing intrauterine pregnancy complicated by fetal holoprosencephaly. CONCLUSION: Delays in diagnosis and treatment of heterotopic pregnancies may adversely affect maternal health as well as the outcome of the intrauterine pregnancy. Prenatal screening and/or diagnostic studies are necessary to evaluate the intrauterine pregnancy. 相似文献
44.
45.
Bozas G Bamias A Koutsoukou V Efstathiou E Gika D Papadimitriou CA Dimopoulos MA 《Gynecologic oncology》2007,104(3):580-585
OBJECTIVES: Synergism between gemcitabine and cisplatin is supported by preclinical and clinical data. The present study explores the efficacy of a biweekly regimen in platinum-resistant/refractory, paclitaxel-pretreated ovarian and peritoneal cancer. METHODS: 50 paclitaxel-pretreated patients with platinum-resistant/refractory ovarian or peritoneal carcinoma who had previously received paclitaxel chemotherapy, were treated with six cycles of gemcitabine 1000 mg/m(2) followed by cisplatin 40 mg/m(2) on days 1 and 15, repeated every 4 weeks. RESULTS: The median platinum-free interval (PFI) was 4 months while the median number of previous treatment lines was 2. Chemotherapy was well tolerated. Objective responses were observed in 31.5% of evaluable patients (n=35). CA125 response was observed in 68% of patients with elevated CA125 (n=41). Median overall survival (OS) was 13.2 months (95% Confidence Interval, CI: 10.2-16.2) while progression-free survival (PFS) was 4.9 months (95%CI: 3.5-6.4). A PFI of less than 3 months was associated with lower objective response rates (15.8% versus 50%, p=0.03). CONCLUSIONS: Biweekly gemcitabine and cisplatin is feasible for patients with platinum-resistant ovarian or peritoneal cancer and is associated with a favorable toxicity profile. In a population with recent exposure to platinum, a PFI of less than 3 months was the major factor influencing response to chemotherapy. 相似文献
46.
Falagas ME Velakoulis S Iavazzo C Athanasiou S 《European journal of obstetrics, gynecology, and reproductive biology》2007,134(2):147-156
The use of vaginal meshes has been an advance in the surgical management of women with pelvic organ prolapse. We reviewed the literature to synthesize the evidence regarding the infectious complications related to this new type of foreign body. We searched PubMed, current contents, and references of initially identified relevant articles and extracted data regarding the incidence, clinical manifestation, and management of vaginal mesh-related infections. The incidence of mesh-related infections and erosion ranged from 0 to 8%, and 0 to 33%, respectively, in the published studies. Various factors influence the development of vaginal mesh-related infectious complications such as the kind of biomedical material (e.g. filament structure, pore size) of the mesh, the type of procedure, the preventive measures taken, and the age and underlying comorbidity of the treated women. Non-specific pelvic pain, persistent vaginal discharge or bleeding, dyspareunia, and urinary or faecal incontinence are the most common manifestation of vaginal mesh-related infection. Clinical examination may reveal induration of the vaginal incision, vaginal granulation tissue, draining sinus tracts, and prosthesis erosion or rejection. Various pathogens have been implicated, including Gram-positive and Gram-negative aerobic and anaerobic bacteria. The management of mesh-related infections in women who underwent pelvic organ reconstruction is combined surgical and medical treatment. Although the use of vaginal meshes has become a new effective method of pelvic organ prolapse surgery clinicians should be aware of the various post-operative complications, including mesh-related infections. 相似文献
47.
Andrew W. Szopa-Comley Christos C. Ioannou 《Proceedings of the National Academy of Sciences of the United States of America》2022,119(23)
To increase their chances of survival, prey often behave unpredictably when escaping from predators. However, the response of predators to, and hence the effectiveness of, such tactics is unknown. We programmed interactive prey to flee from an approaching fish predator (the blue acara, Andinoacara pulcher) using real-time computer vision and two-wheeled robots that controlled the prey’s movements via magnets. This allowed us to manipulate the prey’s initial escape direction and how predictable it was between successive trials with the same individual predator. When repeatedly exposed to predictable prey, the predators adjusted their behavior before the prey even began to escape: prey programmed to escape directly away were approached more rapidly than prey escaping at an acute angle. These faster approach speeds compensated for a longer time needed to capture such prey during the subsequent pursuit phase. By contrast, when attacking unpredictable prey, the predators adopted intermediate approach speeds and were not sensitive to the prey’s escape angle but instead showed greater acceleration during the pursuit. Collectively, these behavioral responses resulted in the prey’s predictability having no net effect on the time taken to capture prey, suggesting that unpredictable escape behavior may be advantageous to prey in fewer circumstances than originally thought. Rather than minimizing capture times, the predators in our study appear to instead adjust their behavior to maintain an adequate level of performance during prey capture.Rapid evasive responses are a vital tool prey use to minimize capture by predators (1, 2). Despite their ubiquity, it can be challenging to demonstrate the benefit of escape strategies, due to the difficulties involved in designing studies which integrate realistic predation with manipulation of prey behavior that experimentally controls for confounding effects. Studying the behavior of real predators is crucial when attempting to demonstrate the adaptive value of prey adaptations, especially when these are dependent on features of predator cognition (3–5). This applies particularly to unpredictable escape behavior by prey, which is thought to enhance prey survival by compromising the ability of predators to anticipate the movement of their target (6). Although unpredictable escape tactics are widespread taxonomically (7, 8), we know little about how real predators respond to unpredictability in prey escape strategies and whether this prevents predators from adjusting their behavior over multiple interactions with prey (9, 10).Controlled experiments in which human predators target continuously moving virtual prey have demonstrated that abrupt and unpredictable changes in direction reduce the accuracy of prey targeting (11, 12). However, it is unknown whether the survival advantage conferred by unpredictable motion also applies against nonhuman predators. Additionally, the escape responses of prey which are initially stationary are common in nature, as numerous prey taxa freeze once they have detected a potential threat or remain motionless to avoid detection by predators, before eventually fleeing only once a predator gets too close (1, 13–15). One way for stationary prey to be unpredictable is to vary the initial escape angle from one encounter to the next (16). This is a distinct tactic to the unpredictable movements made by prey which move continuously regardless of the presence of a predatory threat (6) or the abrupt turns made by some prey in anticipation of a predator’s attack (17). Although theoretical models predict that for a predator of a given speed, prey should select a single optimal escape trajectory which maximizes the distance from an approaching predator (18, 19), predators might anticipate the movements of prey which repeatedly escape at a fixed angle relative to their approach (20). Contrary to expectations based on a single optimal escape path, a wide range of prey species show a substantial degree of variability in their initial escape angles (16), including amphibians (21), crustaceans (22, 23), fish (24–27), insects (28, 29), mammals (30), and reptiles (31). Given that this variability is so widespread taxonomically, investigating whether it represents an antipredator strategy aimed at generating unpredictability could have major implications for our understanding of prey escape behavior (32, 33).Many predator-prey interactions are typified by feedback between the attacker and the target (34), making it difficult to disentangle the effects of prey defenses on predators from the impact of predator behavior on prey using a purely observational approach. One way to determine the importance of prey defensive tactics is to present real predators with standardized virtual prey, whose movements and behavior can be precisely controlled and experimentally manipulated (35–39). However, previous experiments with virtual prey have used unresponsive prey items which do not react to predators, and do not allow the predator to capture prey and be rewarded, making it extremely challenging to study repeated interactions between predators and prey. These limitations can be overcome by using interactive robotic prey (40).To study the effect of unpredictability in prey escape on predators, we developed an experimental system [Fig. 1A; see also Swain et al. (41)], in which artificial robot-controlled prey were programmed to flee from blue acara cichlid (Andinoacara pulcher) predatory fish. Blue acaras are opportunistic predators with a broad diet but actively pursue highly evasive prey such as Trinidadian guppies (Poecilia reticulata) (42, 43). Prey initiated their escape response once the predator had approached within a threshold distance (Fig. 1B), mimicking the tendency of many prey to flee from a distant predator at submaximal speeds (14, 44). After an initial period in which groups of blue acaras were trained to attack the prey (the training period, SI Appendix, SI Methods), individual predators were repeatedly presented with prey which escaped either in predictable or unpredictable directions over 20 successive experimental trials (the test period). For individuals assigned to the predictable treatment (which acted as the control), prey escaped at the same angle relative to the predator’s approach from one trial to the next, whereas in the unpredictable treatment, prey were programmed to flee in random directions over successive trials (Fig. 1C). To successfully capture prey, pursuit predators must respond to changes in prey direction, which occur at the start of a chase (45–47). Across trials with predictable prey, the predators had the opportunity to gain reliable information about the prey’s likely escape direction, in contrast to the unpredictable treatment where the prey’s escape angle in previous trials was not a reliable indicator of its escape direction in future encounters. If unpredictable escape behavior is adaptive, increased uncertainty about the prey’s likely escape direction in the unpredictable treatment should reduce the performance of the predator in these trials, with slower speeds of approach (i.e., before the prey respond), longer times taken to capture prey, and/or greater kinematic costs resulting from higher speeds, increased acceleration, and more turning during the pursuit.Open in a separate windowFig. 1.The robotic prey system. (A) Diagram (not to scale) showing a side view of the experimental system, with the Bluetooth-controlled robot situated on a platform underneath the experimental tank and the webcam used to monitor the predator’s movements suspended overhead. The prey’s movements are controlled by the robot via magnets, enabling the prey to escape from an attacking predator once the predator approaches within 27 cm of the prey’s starting position. See ref. 41 for a similar system designed for robotic predators attacking prey fish shoals. (B) Prey escape angles were defined relative to the predator’s approach direction. (C) In the predictable treatment, prey escaped at the same initial angle over successive trials (the escape angle varied between individual predators). In the unpredictable treatment, the prey’s initial escape angle varied randomly from trial to trial. While the experiment manipulated the prey’s initial escape angle, the prey’s subsequent escape trajectory was fixed as a straight-line path in both treatments. 相似文献
48.
49.
50.
Matteo Morotti Christos E. Zois Rokaya El-Ansari Madeleine L. Craze Emad A. Rakha Shih-Jung Fan Alessandro Valli Syed Haider Deborah C. I. Goberdhan Andrew R. Green Adrian L. Harris 《British journal of cancer》2021,124(2):494
Background Glutamine (Gln) is an abundant nutrient used by cancer cells. Breast cancers cells and particularly triple-receptor negative breast cancer (TNBC) are reported to be dependent on Gln to produce the energy required for survival and proliferation. Despite intense research on the role of the intracellular Gln pathway, few reports have focussed on Gln transporters in breast cancer and TNBC.Methods The role and localisation of the Gln transporter SLC38A2/SNAT2 in response to Gln deprivation or pharmacological stresses was examined in a panel of breast cancer cell lines. Subsequently, the effect of SLC38A2 knockdown in Gln-sensitive cell lines was analysed. The prognostic value of SLC38A2 in a cohort of breast cancer was determined by immunohistochemistry.Results SLC38A2 was identified as a strongly expressed amino acid transporter in six breast cancer cell lines. We confirmed an autophagic route of degradation for SLC38A2. SLC38A2 knockdown decreased Gln consumption, inhibited cell growth, induced autophagy and led to ROS production in a subgroup of Gln-sensitive cell lines. High expression of SLC38A2 protein was associated with poor breast cancer specific survival in a large cohort of patients (p = 0.004), particularly in TNBC (p = 0.02).Conclusions These results position SLC38A2 as a selective target for inhibiting growth of Gln-dependent breast cancer cell lines.Subject terms: Breast cancer, Cancer metabolism 相似文献